2022 |
Simon Schneegans, Moritz Zeumer, Jonas Gilg, Andreas Gerndt CosmoScout VR – A Modular 3D Solar System Based on SPICE (Inproceedings) In: IEEE Aerospace Conference, Hybrid Event (Big Sky, MO, USA), March 5-12, 2022, IEEE, 2022. (BibTeX) @inproceedings{Schneegans2022, |
Tobias Franz, Christoph Seidl, Philipp M. Fischer, Andreas Gerndt Utilizing Multi-level Concepts for Multi-phase Modeling (Journal Article) In: Software and Systems Modeling, 2022. @article{Franz2022, |
2021 |
Nick Brown, Nash Rupert, Piero Poletti, Giorgio Guzzeta, Mattia Manica, Agnese Zardini, Markus Flatken, Jules Vidal, Charles Gueunet, Evgenij Belikov, Julien Tierny, Artur Podobas, Wei Der Chen, Stefano Markidis, Andreas Gerndt Utilising Urgent Computing to Tackle the Spread of Mosquito-borne Diseases (Inproceedings) In: IEEE/ACM Supercomputing, Workshop, HPC for Urgent Decision Making (UrgentHPC), ST. Louis, MO, USA, Nov. 19, 2021, ACM/IEEE, 2021. @inproceedings{Brown2021,It is estimated that around 80% of the world's population live in areas susceptible to at-least one major vector borne disease, and approximately 20% of global communicable diseases are spread by mosquitoes. Furthermore, the outbreaks of such diseases are becoming more common and widespread, with much of this driven in recent years by socio-demographic and climatic factors. These trends are causing significant worry to global health organisations, including the CDC and WHO, and-so an important question is the role that technology can play in addressing them. In this work we describe the integration of an epidemiology model, which simulates the spread of mosquito-borne diseases, with the VESTEC urgent computing ecosystem. The intention of this work is to empower human health professionals to exploit this model and more easily explore the progression of mosquito-borne diseases. Traditionally in the domain of the few research scientists, by leveraging state of the art visualisation and analytics techniques, all supported by running the computational workloads on HPC machines in a seamless fashion, we demonstrate the significant advantages that such an integration can provide. Furthermore we demonstrate the benefits of using an ecosystem such as VESTEC, which provides a framework for urgent computing, in supporting the easy adoption of these technologies by the epidemiologists and disaster response professionals more widely. |
Jonas Gilg, Sebastian Zander, Simon Schneegans, Volker Ahlers, Andreas Gerndt Comparison of Depth Buffer Techniques for Large and Detailed 3D Scenes (Inproceedings) In: GI VR/AR 2021, GI Worskhop, Virtual Event, Sep. 9-10, 2021, 2021. @inproceedings{Gilg2021,Large scale 3D scenes in applications like space simulations are often subject to depth buffer related issues and visual artefacts like Z-fighting and spatial jittering. These issues are primarily a result of indistinguishable depth buffer values. To mitigate these issues, many techniques have been developed over time to better distribute depth values over the clipping range. These techniques range from simple adjustments of the projection matrix to complex solutions like multistage rendering with layered depth buffers. This work presents, compares and evaluates commonly used approaches found in iterature and real world applications. An experiment is set up to compare the presented depth buffer techniques using the metric of minimum triangle separation (MTS). The gathered results are presented and evaluated, to give a good overview on which techniques are well suited for the use in applications with large scale 3D scenes. |
Anna Bahnmüller, Jan Wulkop, Jonas Gilg, Daniel Schanz, Andreas Schröder, Georgia Albuquerque, Andreas Gerndt Augmented Reality for Massive Particle Distribution (Inproceedings) In: GI VR/AR 2021, GI Worskhop, Virtual Event, Sep. 9-10, 2021, 2021, (BEST PAPER AWARD). @inproceedings{Bahnmueller2021,Understanding the behavior of aerosol particles remains a key concern especially during the current corona pandemic times. In this paper, we present a method for visualizing the distribution of aerosol particles in augmented reality (AR) using the Microsoft Hololens device. We use this technology to obtain better spatial perception of particles in the real world which are invisible to the naked eye. As a case study, we show the flow field of exhaled aerosols with and without wearing a mask. To do this, we first measure the particle flow under laboratory conditions. Then we trace a certain amount of exhaled particles. Using the particle system component of the Unity game engine, our AR application also takes each particle's 3D position into consideration. Furthermore, 3 different particle visualization approaches are evaluated to develop the ability to visualize the maximum number of particles on Microsoft HoloLens without compromising on visual quality. Finally, we were able to show virtual particles in the real world. Without mask they propagate forward and with mask they ascend. With an optimized implementation, we achieved a simultaneous display of nearly 80,000 moving particles at an average rate of 35 frames per second. |
Sascha Müller, Adeline Jordon, Thomas Noll, Andreas Gerndt A Modular Approach to Non-deterministic Dynamic Fault Trees with Repair (Inproceedings) In: 40th International Conference on Computer Safety, Reliability and Security (SafeComp2021), Sep. 7-10, York, UK, 2021, 2021. @inproceedings{Mueller2021, |
Tobias Franz, Ayush Mani Nepal, ain Alabedin ZHaj Hammadeh, Olaf Maibaum, Andreas Gerndt, Daniel Lüdtke Tasking Modeling Language: A toolset for model-based engineering of data-driven software systems (Inproceedings) In: 2nd European Workshop on On-Board Data Processing (OBDP2021), ESA Workshop, June 14-17, 2021, 2021. @inproceedings{Franz2021,The interdisciplinary process of space systems engineering poses challenges for the development of the on-board software. The software integrates components from different domains and organizations and has to fulfill requirements, such as robustness, reliability, and real-time capability. Model-based methods not only help to give a comprehensive overview, but also improve productivity by allowing artifacts to be generated from the model automatically. However, general-purpose modeling languages, such as the Systems Modeling Languagetextttchar126(SysML), are not always adequate because of their ambiguity resulting from their generic nature. Furthermore, sensor data handling, analysis, and processing of data in on-board software requires focus on the system's data flow and event mechanism. To achieve this, we developed the Tasking Modeling Languagetextttchar126(TML) which allows system engineers to model complex event-driven software systems in a simplified way and to generate software from the model. Type and consistency checks on the formal level help to reduce errors early in the engineering process. TML is focused on data-driven systems and its models are designed to be extended and customized to specific mission requirements. This paper describes the architecture of TML in detail, explains the base technology, the methodology, and the developed domain specific languagestextttchar126(DSLs). It evaluates the design approach of the software via a case study and presents advantages as well as challenges faced. |
Andreas Lund, Zain Alabedin Haj Hammadeh, Patrick Kenny, Vishav Bensal, Andrii Kovalov, Hannes Watolla, Andreas Gerndt, Daniel Lüdtke ScOSA System Software: The Reliable And Scalable Middleware For A Heterogeneous And Distributed On-board Computer Architecture (Journal Article) In: CEAS Space Journal, 2021. @article{Lund2021,Designing on-board computers (OBC) for future space missions is determined by the trade-off between reliability and performance. Space applications with higher computational demands are not supported by currently available, state-of-the-art, space-qualified computing hardware, since their requirements exceed the capabilities of these components. Such space applications include Earth observation with high-resolution cameras, on-orbit real-time servicing, as well as autonomous spacecraft and rover missions on distant celestial bodies. An alternative to state-of-the-art space-qualified computing hardware is the use of commercial-off-the-shelf (COTS) components for the OBC. Not only are these components cheap and widely available, but they also achieve high performance. Unfortunately, they are also significantly more vulnerable to errors induced by radiation than space-qualified components. The ScOSA (Scalable On-board Computing for Space Avionics) Flight Experiment project aims to develop an OBC architecture which avoids this trade-off by combining space-qualified radiation-hardened components (the reliable computing nodes, RCNs) together with COTS components (the high performance nodes, HPNs) into a single distributed system. To abstract this heterogeneous architecture for the application developers, we are developing a middleware for the aforementioned OBC architecture. Besides providing an monolithic abstraction of the distributed system, the middleware shall also enhance the architecture by providing additional reliability and fault tolerance. In this paper, we present the individual components comprising the middleware, alongside the features the middleware offers. Since the ScOSA Flight Experiment project is a successor of the OBC-NG and the ScOSA projects, its middleware is also a further development of the existing middleware. Therefore, we will present and discuss our contributions and plans for enhancement of the middleware in the course of the current project. Finally, we will present first results for the scalability of the middleware, which we obtained by conducting software-in-the-loop experiments of different sized scenarios. |
Riccardo Fellegara, Markus Flatken, Francesco De Zan, Andreas Gerndt Interactive Visualization and Topology-based Analysis of Large-scale Time-varying Remote-sensing Data: Challenges and Opportunities (Inproceedings) In: EGU General Assembly 2021, Conference Abstracts, Online, April 19-30, 2021, 2021, (Extended Abstract). @inproceedings{Fellegara2021a,Over the last few years, the amount of large and complex data in the public domain has increased enormously and new challenges arose in the representation, analysis and visualization of such data. Considering the number of space missions that provided and will provide remote sensing data, there is still the need of a system that can be dispatched in several remote repositories and being accessible from a single client of commodity hardware. To tackle this challenge, at the DLR Institute for Software Technology we have defined a dual backend frontend system, enabling the interactive analysis and visualization of large-scale remote sensing data. The basis for all visualization and interaction approaches is CosmoScout VR, a visualization tool developed internally at DLR, and publicly available on Github, that allows the visualization of complex planetary data and large simulation data in real-time. The dual component of this system is based on an MPI framework, called Viracocha, that enables the analysis of large data remotely, and allows the efficient network usage about sending compact and partial results for interactive visualization in CosmoScout as soon as they are computed. A node-based interface is defined within the visualization tool, and this lets a domain expert to easily define customized pipelines for processing and visualizing the remote data. Each “node” of this interface is either linked with a feature extraction module, defined in Viracocha, or to a rendering module defined directly in CosmoScout. Being this interface completely customizable by a user, multiple pipelines can be defined over the same dataset to enhance even more the visualization feedback for analysis purposes. Being an ongoing project, on top of these tools, as a novel strategy in EO data processing and visualization, we plan to define and implement strategies based on Topological Data Analysis (TDA). TDA is an emerging set of technique for processing the data considering its topological features. These include both the geometric information associated to a point, as well all the non-geometric scalar values, like temperature and pressure, to name a few, that can be captured during a monitoring mission. One of the major theories behind TDA is Discrete Morse Theory, that, given a scalar value, is used to define a gradient on such function, extract the critical points, identify the region-of-influence of each critical point, and so on. This strategy is parameter free and enables a domain scientist to process large datasets without a prior knowledge of it. An interesting research question, that it will be investigated during this project is the correlation of changes of critical points at different time steps, and the identification of deformation (or changes) across time in the original dataset. |
Arnau Prat, Jan Sommer, Ayush Mani Nepal, Tobias Franz, Hauke Müntinga, Andreas Gerndt, Daniel Lüdtke The BECCAL Experiment Design and Control Software (Inproceedings) In: IEEE Aerospace Conference, Virtual Event, March 6-20, 2021, IEEE, 2021. @inproceedings{Prat2021, |
Azeem Syed Muhammad, Krishnan Chandran, Georgia Albuquerque, Frank Steinicke, Andreas Gerndt A Constraints-based Interaction System for Spacecraft Design in Augmented Reality (Inproceedings) In: IEEE Aerospace Conference, Virtual Event, March 6-20, 2021, IEEE, 2021. @inproceedings{Muhammad2021, |
2020 |
Ayush Mani Nepal, Arnau Prat Sala, Kilian Johann Höflinger, Andreas Gerndt, Daniel Lüdtke Modeling and Simulation of a Spacecraft Payload Hardware Using Machine Learning Techniques (Inproceedings) In: ASCEND 2020, Virtual Event, Nov. 16-18, 2020, American Institute of Aeronautics and Astronautics (AIAA), 2020. @inproceedings{Nepal2020,Space systems are complex and consist of multiple subsystems. Research and development teams of such complex systems are usually distributed among various institutions and space agencies. This affects the quality of the On-board Software (OBSW) since testing it without having all required subsystems at the software development site can be troublesome. In this paper, we present a data-driven method which can be used to synthesize parts of a system or even an entire system as a black-box model. We exploit the data collected from the real hardware to derive a model using a Machine Learning (ML) algorithm. The proposed model can easily be distributed among development teams and is dedicated to emulate the system for testing the OBSW. |
Andrii Kovalov, Tobias Franz, Hannes Watolla, Vishav Vishav, Andreas Gerndt, Daniel Lüdtke Model-Based Reconfiguration Planning for a Distributed On-board Computer (Inproceedings) In: 12th System Analysis and Modelling (SAM) Conference - Languages, Methods and Tools for AI-based Systems, co-located with MODELS 2020, Virtual Event, Oct. 19-20, 2020, pp. 55–62, Association for Computing Machinery (ACM), 2020. @inproceedings{Kovalov2020,The ScOSA project (Scalable On-board Computing for Space Avionics) of the German Aerospace Center aims at combining radiation hardened space hardware together with unreliable, but high performance COTS (commercial off-the-shelf) components as the processing nodes in a heterogeneous on-board network in order to provide future space missions with the necessary processing capabilities. However, such a system needs to cope with node failures. Our approach is to use a static reconfiguration graph that controls how software tasks are mapped to the processing nodes, and how this mapping should change in response to possible node failures. In this paper we present a model-based approach and a tool for automatic generation of reconfiguration graphs. Based on the software and hardware models, we traverse the graph of all possible failure situations. For every node of this graph we solve a combinatorial optimization problem of mapping tasks to processing nodes either with an SMT solver or using a genetic algorithm. The resulting reconfiguration graph can then be translated into the configuration files that are deployed on the target system, eliminating the need for tedious and error-prone manual configuration design. |
Jan Sommer, Andreas Gerndt, Daniel Lüdtke Shared Data Types for OSRA and TASTE using Modern C++ (Inproceedings) In: Workshop on Model Based Space Systems and Software Engineering (MBSE2020), ESA-Workshop, Virtual Event, Sep. 28-29, 2020, 2020. @inproceedings{Sommer2020,The European Space Agency (ESA) currently provides two tools for the modeling of onboard software: The Assert Set of Tools for Engineering (TASTE) and the OnBoard Software Reference Architecture (OSRA). For data type modeling, TASTE uses the standardized Abstract Syntax Notation One (ASN.1), while OSRA provides an internal eCorebased data type representation. Unfortunately, the interworking between the two frameworks lacks a mechanism to exchange data easily without duplicating the data type information. In this work, we present our approach for the exchange of data types and data values between software developed with both tools. We show our additions to the OSRA infrastructure enabling the exchange of data types between OSRA and TASTE based on the same data type descriptions in ASN.1. This includes complementing the OSRA editor with the ability to read and write ASN.1 data type descriptions and to specify the data type encodings in TASTE's ASN.1 Control Notation. Our previous implementation of the ASN.1 data types in Modern C++ has been extended with a prototypical implementation for the serialization of the data types compatible with TASTE's ACN encoded types. As for the data types themselves, C++ metaprogramming techniques have been used for the encoder. This allows us to keep the code generators simple and maintainable. Some early results on the exchange of data between OSRA, enabled with our prototype generator, and the TASTE framework with its own ASN.1 compiler are presented and discussed. |
Sascha Müller, Liana Mikaelyan, Andreas Gerndt, Thomas Noll Synthesizing and Optimizing FDIR Recovery Strategies from Fault Trees (Journal Article) In: Science of Computer Programming, vol. 196, pp. 102478, 2020. @article{Mueller2020b,Redundancy concepts are major design drivers in fault-tolerant space systems. It can be a difficult task to decide when to activate which redundancy, and which component should be replaced. In this paper, we refine a methodology where recovery strategies are synthesized from a model of non-deterministic dynamic fault trees. The synthesis is performed by transforming non-deterministic dynamic fault trees into Markov automata that represent all possible choices between recovery actions. From the corresponding scheduler, optimized for maximum expected long-term reachability of failure states, a recovery strategy, optimal with respect to mean time to failure, can then be derived and represented by a model we call recovery automaton. We discuss techniques for reducing the state space of this recovery automaton, and analyze their soundness and completeness. We show that they do not generally guarantee recovery automata with the minimal number of states and derive a class where this guarantee holds. Implementation details for our approach are given and its effectiveness is verified on the basis of three case studies. |
Andreas Lund, Zain Alabedin Haj Hammadeh, Patrick Kenny, Vishav Vishav, Andrii Kovalov, Andreas Gerndt, Daniel Lüdtke A Fault-tolerant, Scalable and Distributed Middleware for Future Space Missions (Inproceedings) In: Deutscher Luft- und Raumfahrtkongress (DLRK), Online Event, Sep. 1-3, 2020, Deutsche Gesellschaft für Luft- und Raumfahrt, 2020. @inproceedings{Lund2020,The computational demands of current space missions outrun the capability of available state-of-the-art space-qualified computing hardware. Future missions, including earth-observation with high-resolution cameras, on-orbit real-time servicing, as well as autonomous spacecraft and rover missions on distant celestial bodies, will have even higher requirements concerning the computational power of the spacecrafts hardware. An approach to overcome these difficulties, which is already used and will be used widely in the future, is the use of interconnected commercial-off-the-shelf (COTS) processors for the on-board computers (OBC) of spacecraft. The COTS processors, while offering a much higher performance at a much lower cost, have the disadvantage of being more vulnerable to soft errors induced by radiation in comparison to space-qualified processors. In this context, the ScOSA Flight Experiment project develops an OBC which copes with the requirements for future space missions. The OBC will combine reliable computing nodes (RCNs) together with high-performance nodes (HPNs) into a single distributed system. For abstracting this complex architecture to a monolithic system, a middleware is needed. In this paper, we present the ScOSA middleware by means of its individual components. Furthermore, we explain its features of heterogeneity, scalability, reconfiguration, cross-processor distribution and fault-tolerance. Since the ScOSA Flight Experiment project is a successor of the OBC-NG and the ScOSA projects, its middleware is also a further development of the existing middleware. Therefore, we will present and discuss our contributions and plans for enhancement of the middleware in the course of the new project. |
Sascha Müller, Kilian Johann Höflinger, Michal Smisek, Andreas Gerndt Towards an FDIR Software Fault Tree Library for Onboard Computers (Inproceedings) In: IEEE Aerospace Conference, Yellowstone Conference Center, Big Sky, Montana, March 8-13, 2020, pp. 1–10, IEEE, 2020. @inproceedings{Mueller2020a,The increasing complexity of space missions, their software architectures, and hardware that has to meet the demands for those missions, imposes numerous new challenges for many engineering disciplines such as reliability engineering. Affected by the ever growing demand for more onboard computation power are the onboard computers. They in return require Fault Detection, Isolation, and Recovery (FDIR) architectures to support their fault tolerant operation in the harsh environment of space. Especially high performance commercial processing units face the challenge of dealing with negative radiation effects, which may significantly degrade their operation. To design performant and fault tolerant onboard computers, it is of high interest to assess the effectiveness of the FDIR architecture in the early phase of system design. This can be achieved using Fault Tree Analysis (FTA). However, to create complete fault trees manually is an error prone and labor intensive task. In this paper, the methodology for assessing the FDIR design of onboard computers in space systems, presented in [1], is refined by introducing a library of FDIR routines. The routines are modeled using fault trees and are composed into a software system fault tree using a basic fault model and a design configuration chosen by the reliability engineer. To assess the configurations, we give a heuristic based on a factor-criteria-metric model. We demonstrate the feasability of our approach on the basis of a case study on the rover of the Martian Moons eXploration (MMX) mission. Several FDIR configurations are studied and fault trees are generated for them. For the chosen case study, we obtain a reduction of up to 80% in terms of modeling effort. |
Anna Bahnmüller, Syed Muhammad Azeem, Georgia Albuquerque, Andreas Gerndt Evaluation of Interaction Techniques for Early PhaseSatellite Design in Immersive AR (Inproceedings) In: IEEE Aerospace Conference, Yellowstone Conference Center, Big Sky, Montana, March 8-13, 2020, IEEE, 2020. @inproceedings{Bahnmueller2020,In this paper, we present a new controller-based interaction technique on the Microsoft HoloLens to support communication for the early phase satellite design at the Concurrent Engineering Facility (CEF). We design a virtual satellite with virtual moveable objects utilizing two different interaction methods: the default hand gesture-based interaction method and a novel controller-based interaction method for rotation and translation of satellite components in immersive augmented reality. In order to evaluate our method, we conduct a perceptual study with 12 participants. We apply multiple performance metrics for each user on both methods. Additionally, we measure user preferences and ease of use. Our results show that our controller-based method is significantly more precise for placing objects (consisting of position and orientation). Furthermore, it is less time consuming than the hand gesture-based method and more preferred by the participants. |
2019 |
Arturo S. García, Terrence Fernando, David J. Roberts, Christian Bar, Michele Cencetti, Wito Engelke, Andreas Gerndt Collaborative Virtual Reality Platform for Visualizing Space Data and Mission Planning (Journal Article) In: Multimedia Tools and Applications, Springer, June 1, 2019, vol. 78, no. 23, pp. 33191–33220, 2019, ISSN: 1380-7501. @article{Garcia2019,This paper presents the system architecture of a collaborative virtual environment in which distributed multidisciplinary teams involved in space exploration activities come together and explore areas of scientific interest of a planet for future missions. The aim is to reduce the current challenges of distributed scientific and engineering meetings that prevent the exploitation of their collaborative potential, as, at present, expertise, tools and datasets are fragmented. This paper investigates the functional characteristics of a software framework that addresses these challenges following the design science research methodology in the context of the space industry and research. An implementation of the proposed architecture and a validation process with end users, based on the execution of different use cases, are described. These use cases cover relevant aspects of real science analysis and operation, including planetary data visualization, as the system aims at being used in future European missions. This validation suggests that the system has the potential to enhance the way space scientists will conduct space science research in the future. |
Jan Sommer, Daniel Lüdtke, Andreas Gerndt Creating a Reliable Data Type Framework for the OSRA Using Modern C++ (Inproceedings) In: 70th International Astronautical Congress (IAC), Washington, D.C., USA, Oct. 21-25, 2019, International Astronautical Federation (IAF), 2019. @inproceedings{Sommer2019b,Ever increasing demands on the complexity of onboard software has lead the European Space Agency to define the OnBoard Software Reference Architecture (OSRA) creating a common framework for modeling onboard software for space applications. OSRA provides tools for the description of onboard software (OSW) in a componentcentric way, but leaves the implementation of the OSW itself or related autocoding tools to other institutions. As a first step towards a codegeneration framework from high level software models, we present source code mappings from the OSRA data type model to a C++ type system. The goal of the framework is to take care of type safety and value consistency issues and to provide an intuitive interface to the application developer for defining and working with data types, while at the same time having the target of autocoding in mind. We use language features introduced with the modern C++ standards to allow for extensive validity checks at compiletime and additional checks at runtime. For the integration with OSRA tools, we take an intermediate step transforming the graphically declared types of OSRA into an ASN.1 representation before generating the corresponding C++ source code. The integration is bidirectional, i.e. data types, which have been constructed solely in ASN.1 notation, can also be used inside OSRA models which helps maintaining more complex data structures in a textual format and enables us to use existing complex data sets from previous projects and from The Assert Set of Tools for Engineering (TASTE) project to test the feasibility and the limitations of the type system. In the end, we present a type system which can be autogenerated and automatically avoids common sources of error like faulty initialization, outofbound access and accidental range overflows. Such errors cause compiletime errors if possible and runtime errors otherwise. In order to provide developers with a practical solution, efforts were made to facilitate integration with existing code bases or third party libraries which allows an iterative process of adaption. We strive to generate complete onboard software projects from the OSRA component model. The data type system defined here provides therefore the basis for that endeavor as it determines the way components will exchange data and how developers will need to interact with them. |
Philipp M. Fischer, Caroline Lange, Volker Maiwald, Sascha Müller, Andrii Kovalov, Janis Häseker, Thomas Gärtner, Andreas Gerndt Spacecraft Interface Management in Concurrent Engineering Sessions (Inproceedings) In: 16th International Conference on Cooperative Design, Visualization and Engineering (CDVE2019), Mallorca, Spain, Oct. 6-9, 2019, pp. 54–63, Springer, Cham, 2019. @inproceedings{Fischer2019,This paper contributes to the topic of spacecraft interface and data rate management in Concurrent Engineering (CE) sessions. At DLR, CE is used together with a CE process for designing new spacecraft. The software Virtual Satellite supports this process. It provides a shared system model to the engineers to exchange design information. Until today, it supports the structural decomposition of the system and the analysis of design drivers such as the mass or power consumption of the spacecraft. During one of the S2TEP studies for a multi-mission platform it was required to have a closer look to power and data interfaces. This paper discusses the state of the art to this topic and derives a generic approach to it. This approach is customized and nally implemented in Virtual Satellite and directly applied in the S2TEP study. |
Diana Peters, Philipp M. Fischer, Philipp M. Schäfer, Kobkaew Opasjumruskit, Andreas Gerndt Digital Availability of Product Information for Collaborative Engineering of Spacecraft (Inproceedings) In: 16th International Conference on Cooperative Design, Visualization and Engineering (CDVE2019), Mallorca, Spain, Oct. 6-9, 2019, pp. 74–83, Springer, Cham, 2019. @inproceedings{Peters2019,In this paper, we introduce a system to collect product information from manufacturers and make it available in tools that are used for concurrent design of spacecraft. The planning of a spacecraft needs experts from dierent disciplines, like propulsion, power, and thermal. Since these dierent disciplines rely on each other there is a high need for communication between them, which is often realized by a Model-Based Systems Engineering (MBSE) process and corresponding tools. We show by comparison that the product information provided by manufacturers often does not match the information needed by MBSE tools on a syntactic or semantic level. The information from manufacturers is also currently not available in machine-readable formats. Afterwards, we present a prototype of a system that makes product information from manufacturers directly available in MBSE tools, in a machine-readable way. |
Zain A. H. Hammadeh, Tobias Franz, Olaf Maibaum, Andreas Gerndt, Daniel Lüdtke Event-Driven Multithreading Execution Platform for Real-Time On-Board Software Systems (Inproceedings) In: Adam Lackorzynski, Daniel Lohmann (Ed.): 15th Workshop on Operating Systems Platforms for Embedded Real-Time Applications (OSPERT), Stuttgart, Germany, July 9, 2019, pp. 29–34, 2019. @inproceedings{Hammadeh2019,The high computational demand and the modularity of future space applications make the effort of developing multithreading reusable middlewares worthwhile. In this paper, we present a multihreading execution platform and a software development framework that consists of abstract classes with virtual methods. The presented work is written in C++ following the event-driven programming paradigm and based on the inverse of control programming principle. The platform is portable over different operating systems, e.g., Linux and RTEMS. This platform is supported with a modeling language to automatically generate the code from the given requirements. Our platform has been used in already flying satellites, e.g., Eu:CROPIS. We present in this paper an example that illustrates how to use the proposed platform in designing and implementing an on-board software system. |
Olaf Maibaum, Ansgar Heidecker, Fabian Greif, Markus Schlotterer, Andreas Gerndt FDIR Handling in Eu:CROPIS (Inproceedings) In: 12th IAA Symposium on Small Satellites for Earth Observation, Berlin, Germany, May 06-10, 2019, International Academy of Astronautics (IAA), 2019. @inproceedings{Maibaum2019,Fault detection, isolation, and recovery (FDIR) mechanisms in on-board software are essential to guarantee the survival of the satellite in case of a hardware malfunction. E.g., outage of essential attitude control system (ACS) actuators or sensors can lead to mission loss. The on-board software has to handle such situation autonomously by switching to cold redundant devices or by isolation of information from hot redundant devices. The FDIR implementation for the ACS of the spin stabilized small satellite Eu:CROPIS (Euglena Combined Regenerative Organic food Production In Space) is shown in this paper. |
Kilian Höflinger, Sascha Müller, Ting Peng, Moritz Ulmer, Daniel Lüdtke, Andreas Gerndt Dynamic Fault Tree Analysis for a Distributed Onboard Computer (Inproceedings) In: IEEE Aerospace Conference, Yellowstone Conference Center, Big Sky, Montana, March 2-9, 2019, IEEE, 2019. @inproceedings{Hoeflinger2019,Future space missions will demand greater capabilities regarding the processing of sensor data on onboard computers of satellites than current space technology can provide. Limited downlink bandwidth, high resolution sensors and more rigid real-time control algorithms, dedicated to increase satellite autonomy, drive the need for growing onboard computing performance. To overcome these challenges, new high-performance onboard computers are necessary, leading to an increased consideration of Commercial-Of-The-Shelf (COTS) components. The DLR project Scalable Onboard Computing for Space Avionics (ScOSA) targets these challenges with a complex onboard computer design consisting of space-qualified and COTS computing devices, arranged as heterogeneous SpaceWire-interconnected grid computer in space. However, the utilization of COTS components in the harsh space environment imposes new challenges on the system. Therefore, Fault Detection Isolation and Recovery (FDIR) mechanisms are important functionalities of systems like ScOSA. These enable the preservation of the demanded dependability levels for an embedded system in space. To ensure this dependability, the FDIR subsystem configuration requires a detailed analysis regarding potential faults in the system. For this purpose, we employed Dynamic Fault Tree (DFT) analysis, a methodology which is used to model faults and their temporal propagation through an onboard computer. With this paper, we contribute a new building block for showing the applicability of DFT analysis and for closing the gap between theory and practical application of DFTs. The quantitative results of the analysis of the contribution of the ScOSA FDIR subsystem to the overall system reliability are taken as baseline for a discussion on how to effectively improve the system's reliability further. To showcase the methodology, an earth observation low earth orbit use case scenario is defined and the by FDIR means enforced processing system of the Xilinx Zynq SoC computing devices with a DFT analysis evaluated. |
Jan Sommer, Raghuraj Tarikere Phaniraja Setty, Olaf Maibaum, Andreas Gerndt, Daniel Lüdtke Evaluation and Development of the Interaction Layer for Inter-Component Communication of the Onboard Software Reference Architecture (Inproceedings) In: IEEE Aerospace Conference, Yellowstone Conference Center, Big Sky, Montana, March 2-9, 2019, IEEE, 2019. @inproceedings{Sommer2019a,Ever increasing demands on the complexity of onboard software has led the European Space Agency to define the Onboard Software Reference Architecture (OSRA) to create a common framework for modeling onboard software for space applications. The first major version was released at the end of 2017 and provides the metamodel with additional documentation and a model editor. It enables the user to create a detailed high-level representation of an onboard software system, but leaves the choice of an execution platform and the generation of actual source code for it to the implementing party. The core philosophy of OSRA is to divide the onboard software into independent components with clearly defined interfaces and separate the functional and non-functional aspects of components. However, OSRA aims to cover a large range of applications and therefore provides a large variety of modeling artifacts for component interaction. While this gives a lot of design freedom to the software architect designing the overall software, it moves the responsibility of supporting all aspects and behavioral requirements correctly to the execution platform and interaction layer. In this study, we analyze the demands of OSRA towards the execution platform and necessary elements which have to be added or generated in order to support the multitude of different inter-component interactions. The results of the analysis are used to implement the first prototypical code-generation framework for OSRA models. The target execution platform for the code generators is the Tasking Framework, a reactive cooperative multitasking framework from DLR. It has successful flight heritage in numerous spacecraft projects and has also been the target of code generation from software models before. Nevertheless, many of the aspects discussed here apply equally to common priority-based preemptive multitasking frameworks. The analysis and the implementation both uncovered several issues where clarification in the OSRA metamodel description was necessary. We will discuss the additional constraints we introduced towards the metamodel in order to deal with these issues, which eases the generation of code skeletons and scheduling primitives. Finally, while this study concentrates on the inter-component interactions, we will also discuss further aspects currently missing from OSRA and which either need to be added by the implementing party or in a future revision. |
Sebastian Utzig, Robert Kaps, Azeem Syed Muhammad, Andreas Gerndt Augmented Reality for Remote Collaboration in Aircraft Maintenance Tasks (Inproceedings) In: IEEE Aerospace Conference, Yellowstone Conference Center, Big Sky, Montana, March 2-9, 2019, IEEE, 2019. @inproceedings{Utzig2019,In this paper, we present a concept study to facilitate maintenance of an operating aircraft based on its lifelong collected data, called Digital Twin. It demonstrates a damage assessment scenario on a real aircraft component. We propose a graphical user interface that contains menu-guided instructions and inspection documentation to increase the efficiency of manual processes. Furthermore, experts located at different sites can join via a virtual session. By inspecting a 3D model of the aircraft component, they can see synchronized information from a Digital Twin database. With Augmented Reality glasses, the Microsoft HoloLens, a Digital Twin can be experienced personally. In the inspector's view, the 3D model of the Digital Twin is directly superimposed on the physical component. This Mixed Reality Vision can be used for inspection purposes. Any inspection related information can be directly attached to the component. For example, damage locations are marked by the inspector on the component's surface and are stored in the Digital Twin database. Our scenario demonstrates how new information can be derived from the combination of collected data and analyses from the Digital Twin database. This information is used to maintain the continued airworthiness of the aircraft. Feedback from domain related engineers confirm that our interface has an enormous potential for solving current maintenance problems in the aviation industry. Additionally, our study provides ideas for the integration of further analysis functions into the interface. |
Liana Mikaelyan, Sascha Müller, Andreas Gerndt, Thomas Noll Synthesizing and Optimizating FDIR Recovery Strategies from Fault Trees (Inproceedings) In: Cyrille Artho, Peter Csaba Ölveczky (Ed.): 6th International Workshop on Formal Techniques for Safety-Critical Systems (FTSCS), ICEFM Workshop, Gold Coast, Australia, November 16, 2018, pp. 37–54, Springer, Cham, 2019. @inproceedings{MIKA18,Redundancy concepts are an integral part of the design of space systems. Deciding when to activate which redundancy and which component should be replaced can be a difficult task. In this paper, we refine a methodology where recovery strategies are synthesized from a model of non-deterministic dynamic fault trees. The synthesis is performed by transforming non-deterministic dynamic fault trees into Markov Automata. From the optimized scheduler, an optimal recovery strategy can then be derived and represented by a model we call Recovery Automaton. We discuss techniques on how this Recovery Automaton can be further optimized to contain fewer states and transitions and show the effectiveness of our approach on two case studies. |
Sascha Müller, Thomas Noll, Andreas Gerndt Synthesizing Failure Detection, Isolation, and Recovery Strategies from Nondeterministic Dynamic Fault Trees (Journal Article) In: Journal of Aerospace Information Systems (JAIS), vol. 16, no. 2, pp. 52–60, 2019. @article{Mueller2019,Redundancy concepts are an integral part of the design of space systems. Deciding when to activate which redundancy and which component should be replaced can be a difficult task. In this paper, a model of nondeterministic dynamic fault trees is presented. It is shown how appropriate recovery strategies can be synthesized from them. This is achieved by transforming a nondeterministic dynamic fault tree into a Markov automaton. From the optimized scheduler of this Markov automaton, an optimal recovery strategy can then be derived. The model of recovery automata is also introduced to represent these strategies. Finally, how these synthesized strategies can help improve overall system reliability is discussed. |
2018 |
Artur Baranowski, Sebastian Utzig, Philipp Fischer, Andreas Gerndt, Jens Herder 3D Spacecraft Configuration using Immersive AR Technology (Inproceedings) In: Jens Herder, Christian Geiger, Ralf Dörner, Paul Grimm (Ed.): Virtuelle und Erweiterte Realität: 15. Workshop der GI-Fachgruppe VR/AR, Düsseldorf, Germany, October 10-11, 2018, pp. 71–82, Shaker Verlag, 2018. @inproceedings{BARA18,In this paper we propose an integrated immersive augmented reality solution for a software tool supporting spacecraft design and verication. The spacecraft design process relies on expertise in many domains, such as thermal and structural engineering. The various subsystems of a spacecraft are highly interdependent and have diering requirements and constraints. In this context, interactive visualizations play an important role in making expert knowledge accessible. Recent immersive display technologies oer new ways of presenting and interacting with computer-generated content. Possibilities and challenges for spacecraft conguration employing these technologies are explored and discussed. A user interface design for an application using the Microsoft HoloLens is proposed. To this end, techniques for selecting a spacecraft component and manipulating its position and orientation in 3D space are developed and evaluated. Thus, advantages and limitations of this approach to spacecraft conguration are revealed and discussed. |
Benjamin Weps, Daniel Lüdtke, Tobias Franz, Olaf Maibaum, Thijs Wendrich, Hauke Müntinga, Andreas Gerndt A Model-Driven Software Architecture for Ultra-Cold Gas Experiments in Space (Inproceedings) In: 69th International Astronautical Congress (IAC), Bremen, Germany, October 1-5, International Astronautical Federation (IAF) 2018. @inproceedings{Weps2018,Developing software for large and complex experiments is a challenging task. It must incorporate many requirements from different domains, all with their own conceptions about the overall systems. An additional level of complexity is added if the experiment is conducted autonomously during a sounding rocket flight. Without a proper software architecture and development techniques, achieving and maintaining a high code quality is a very cumbersome task. |
Philipp M. Fischer, Meenakshi Deshmukh, Aaron Koch, Robert Mischke, Antonio Martelo Gomez, Andreas Schreiber, Andreas Gerndt Enabling a Conceptual Data Model and Workflow Integration Environment for Concurrent Launch Vehicle Analysis (Inproceedings) In: 69th International Astronautical Congress (IAC), Bremen, Germany, October 1-5, 2018, International Astronautical Federation (IAF) 2018. @inproceedings{FISC18b,Concurrent Engineering (CE) and Model Based Systems Engineering (MBSE) have increased the efficiency of spacecraft, and satellite design in particular. Early design of satellites in Concurrent Engineering Centers (CEC) has almost become business as usual. However, such progress has still to be achieved for the design of launchers. Applying the same approaches as used for satellites has not led to the same amount of improvement, yet. To address this, DLR initiated the project Concurrent Launch Vehicle Analysis (CLAVA) to investigate the shortcomings and to improve the efficiency of conceptual launcher design and analysis. From an MBSE point of view, investigations show that concurrent modelling requires new Conceptual Data Models. In contrast to designing satellites, they are focused on a much more physical abstraction rather than a functional one. Regarding simulations, it has become clear that the conceptual design phase of launchers requires far more computationally intense simulations in a sequential order. With this knowledge, it is possible to outline a new process for CE studies allowing for concurrent design phases and sequential simulation phases. For this, an adjusted architecture of tools is required as well. The data model used for satellite studies within DLR's Concurrent Engineering Facility (CEF) does not fit to the requirements of launcher design and has been adapted. Additionally, DLR's aeronautics divisions have already made substantial progress in increasing the efficiency of their simulations. They employ automated simulation workflows using a parametric model for information exchange between integrated tools. This approach has been adopted and integrated. This paper outlines how this approach is combined with CE and MBSE concepts used for satellites and addresses the specific requirements of launcher design. It provides details about the database used during CE sessions, and how its information is transferred into the parametric data model used to run the required simulations. The conceptual data model of this database has been adapted to the physical representation of launchers; these changes will also be discussed. Furthermore, the general idea of the workflow and the design of the parametric model will be presented. The paper concludes by providing an outlook of how DLR intends to continue on this work, and further refine the developed tools and processes into daily CE and CEF application. |
Sascha Müller, Andreas Gerndt Towards a Conceptual Data Model for Fault Detection, Isolation and Recovery in Virtual Satellite (Inproceedings) In: 8th International Systems & Concurrent Engineering for Space Applications Conference (SECESA), Glasgow, UK, September 26-28, 2018, ESA 2018. @inproceedings{MUEL18,Reliability engineering is an integral part in the design of safety critical systems. Especially spacecraft that cannot receive physical maintenance once delivered into orbit heavily require a fault tolerant design approach. In order to overcome these challenges, concepts from the domain of Fault Detection, Isolation and Recovery (FDIR) are employed. With this paper we present our approach for bringing Model Based Systems Engineering into the realm of reliability engineering using the Virtual Satellite (VirSat) framework. The tool we are developing for this purpose is called VirSat FDIR. In this paper, we discuss a Conceptual Data Model for modelling important aspects of the FDIR domain that we have conceived and implemented for VirSat FDIR. It supports modelling of FDIR faults, recovery, analysis and requirements. We further discuss how these models can be actively used for the purpose of generation of FDIR artefacts and the process of Verification and Validation. |
Philipp Matthias Schäfer, Philipp M. Fischer, Nico Brehm, Christian Erfurth, Andreas Gerndt, Kobkaew Opasjumruskit, Diana Peters Toward a Digital Platform for Spacecraft Manufacturing (Inproceedings) In: 8th International Systems & Concurrent Engineering for Space Applications Conference (SECESA), Glasgow, UK, September 26-28, 2018, ESA 2018. @inproceedings{SCHA18,Professionals of many disciplines are involved in a spacecraft mission. They all use different software tools that are tailored to their tasks and they share data in various ways among themselves. These data sharing activities form a network, which, given modern software engineering practices, offers a lot of opportunities for improvement: simplify data source discoverability, automate previously manual data sharing activities, and better make use available data sources. To simplify data source discoverability, we propose a digital platform with a serviceoriented architecture. Such an architecture also helps to better make use of available data sources. Additionally, we present our projects that automate previously manual data sharing activities and that make better use of available data sources. With the development of the digital platform we aim at providing a significant reduction in resource expenditure, especially time expenditure, for spacecraft missions. |
Yang Liu, Peng Xiaodong, Zhou Wugen, Bo Liu, Andreas Gerndt Template-Based 3D Reconstruction of Non-rigid Deformable Object from Monocular Video (Journal Article) In: 3D Research, 3D Display Research Center, Springer Link, vol. 9, iss. 2, 2018. @article{LIU18,In this paper, we propose a template-based 3D surface reconstruction system of non-rigid deformable objects from monocular video sequence. Firstly, we generate a semi-dense template of the target object with structure from motion method using a subsequence video. This video can be captured by rigid moving camera orienting the static target object or by a static camera observing the rigid moving target object. Then, with the reference template mesh as input and based on the framework of classical template-based methods, we solve an energy minimization problem to get the correspondence between the template and every frame to get the time-varying mesh to present the deformation of objects. The energy terms combine photometric cost, temporal and spatial smoothness cost as well as as-rigid-as-possible cost which can enable elastic deformation. In this paper, an easy and controllable solution to generate the semi-dense template for complex objects is presented. Besides, we use an effective iterative Schur based linear solver for the energy minimization problem. The experimental evaluation presents qualitative deformation objects reconstruction results with real sequences. Compare against the results with other templates as input, the reconstructions based on our template have more accurate and detailed results for certain regions. The experimental results show that the linear solver we used performs better efficiency compared to traditional conjugate gradient based solver. |
Tobias Franz, Daniel Lüdtke, Olaf Maibaum, Andreas Gerndt Model-Based Software Engineering for an Optical Navigation System for Spacecraft (Journal Article) In: CEAS Space Journal, Springer, Vienna, vol. 10, iss. 2, pp. 147-156, 2018. @article{FRAN18,The project Autonomous Terrain-based Optical Navigation (ATON) at the German Aerospace Center (DLR) is developing an optical navigation system for future landing missions on celestial bodies such as the moon or asteroids. Image data obtained by optical sensors can be used for autonomous determination of the spacecraft's position and attitude. Camera-in-the-loop experiments in the Testbed for Robotic Optical Navigation (TRON) laboratory and flight campaigns with unmanned aerial vehicle (UAV) are performed to gather flight data for further development and to test the system in a closed-loop scenario. The software modules are executed in the C++ Tasking Framework that provides the means to concurrently run the modules in separated tasks, send messages between tasks, and schedule task execution based on events. Since the project is developed in collaboration with several institutes in different domains at DLR, clearly defined and well-documented interfaces are necessary. Preventing misconceptions caused by differences between various development philosophies and standards turned out to be challenging. After the first development cycles with manual Interface Control Documents (ICD) and manual implementation of the complex interactions between modules, we switched to a model-based approach. The ATON model covers a graphical description of the modules, their parameters and communication patterns. Type and consistency checks on this formal level help to reduce errors in the system. The model enables the generation of interfaces and unified data types as well as their documentation. Furthermore, the C++ code for the exchange of data between the modules and the scheduling of the software tasks is created automatically. With this approach, changing the data flow in the system or adding additional components (e.g., a second camera) have become trivial. |
Philipp M. Fischer, Meenakshi Deshmukh, Volker Maiwald, Dominik Quantius, Antonio Martelo Gomez, Andreas Gerndt Conceptual Data Model - A Foundation for Successful Concurrent Engineering (Journal Article) In: Concurrent Engineering: Research and Applications (CERA), vol. 26, iss. 1, pp. 55-76, 2018. @article{FISC18a,Today, phase A studies of future space systems are often conducted in special design facilities such as the Concurrent Engineering Facility (CEF) at the German Aerospace Center (DLR). Within these facilities the studies are performed following a defined process making use of a data model for information exchange. Quite often it remains unclear what exactly such a data model is and how it is implemented and applied. Nowadays, such a data model is usually a software using a formal specification describing its capabilities within a so called meta-model. This meta-model, often referred as Conceptual Data Model (CDM), is finally used and instantiated as system model during these CE studies. Such software also provides a user interface for instantiating and sharing the system model within the design team and it provides capabilities to analyze the system model on the fly. This is possible due to the semantics of the underlying CDM creating a common language used to exchange and process design information. This paper explains the implementation of the data model at DLR and shows information how it is applied in the concurrent engineering process of the CEF. It highlights important aspects concerning the modeling capabilities during a study and discusses how they can be implemented into a corresponding CDM. Accordingly, the paper presents important aspects such as rights management and data consistency and the implications of them to the software's underlying technology. A special use case of the data model is depicted and shows the flexibility of the implementation proven by a study of a multi module space station. |
2017 |
Chen Gao, Philipp Martin Fischer, Andreas Gerndt, Zhen Yang A Study of Uncertainty Analysis for Formation Satellite Detection System in Space Science Mission (Inproceedings) In: 68th International Astronautical Congress (IAC), Adelaide, Australia, September 25-29, 2017, International Astronautical Federation (IAF) 2017. @inproceedings{GAO17,A space science mission can be thought as a detection system of its scientific goals. Accuracy of positioning, timing and attitude adjusting, and margins of the payload specification are inevitable uncertainties in parameters which influence the achievement of a space mission goal. Accordingly, mission deviations need to be considered. In the early design phase of a space mission, space engineers are mainly interested whether the requirements of scientific goals are satisfied within specified margins. Thus, a quantitative analysis on how these uncertainties affect the goals would support evaluation and optimization of the mission. As an example, this paper addresses satellite formation missions which play a more and more important role in space science. Such missions provide a unique advantage in detecting high dimensional physical phenomena like the magnetic reconnection in the geo-magnetosphere while single satellites cannot. Merely satellite formation missions can distinguish spatial and temporal variations which are highly coupled parameters. However, this requires differential analysis which is hard to solve. Instead, stochastic-based simulations like the Monte Carlo method are applied where parameter uncertainties are expressed as a distribution formular. The parameter values are randomly generated by these distributions. Then, the simulations are performed multiple times. A massive number of results allows figuring out how the detection system is affected by these uncertainties. But, the resampling process of the Monte Carlo method is complex and time consuming. In this paper, the Weighted Regress Analysis (WRA) method is introduced to speed-up the computation. It approximates the detection system function by a linear function solving a series of coefficients from a set of Monte Carlo results. The drawback of this approach is that the estimation of uncertainties is less precise. To evaluate the availability and accuracy of both methods, we discuss our comparison results in this paper based on a simplified formation detection model. |
Andrii Kovalov, Elisabeth Lobe, Andreas Gerndt, Daniel Lüdtke Task-Node Mapping in an Arbitrary Computer Network Using SMT Solver (Inproceedings) In: Nadia Polikarpova, Steve Schneider (Ed.): 13th International Conference on Integrated Formal Methods (iFM 2017), Torino, Italy,September 18-22, 2017, pp. 177–191, Springer, Cham, 2017. @inproceedings{KOVA17,The problem of mapping (assigning) application tasks to processing nodes in a distributed computer system for spacecraft is investigated in this paper. The network architecture is developed in the project `Scalable On-Board Computing for Space Avionics' (ScOSA) at the German Aerospace Center (DLR). In ScOSA system the processing nodes are connected to a network with an arbitrary topology. The applications are structured as directed graphs of periodic and aperiodic tasks that exchange messages. In this paper a formal definition of the mapping problem is given. We demonstrate several ways to formulate it as a satisfiability modulo theories (SMT) problem and then use Z3, a state-of-the-art SMT solver, to produce the mapping. The approach is evaluated on a mapping problem for an optical navigation application as well as on a set of randomly generated task graphs. |
Sascha Müller, Thomas Noll, Andreas Gerndt Synthesizing FDIR Recovery Strategies From Non-Deterministic Dynamic Fault Trees (Inproceedings) In: AIAA SPACE and Astronautics Forum and Exposition, Orlando, Florida, September 12-14, 2017, AIAA Association, 2017. @inproceedings{MUEL17,Redundancy concepts are an integral part of the design of space systems. Deciding when to activate which redundancy and which component should be replaced can be a difficult task. In this paper, a model of non-deterministic dynamic fault trees is presented and it is shown how appropriate strategies can be synthesized from them. This is achieved by transforming a non-deterministic dynamic fault tree into a Markov Automaton. From the optimized scheduler of this Markov Automaton, an optimal recovery strategy can then be derived. We also introduce the model of Recovery Automata to represent these strategies. |
Philipp M. Fischer, Daniel Lüdtke, Caroline Lange, Frank-Cyrus Roshani, Frank Dannemann, Andreas Gerndt Implementing Model-based System Engineering for the Whole Lifecycle of a Spacecraft (Journal Article) In: CEAS Space Journal, Springer, Vienna, vol. 9, no. 3, pp. 351–365, 2017. @article{FISC17,Design information of a spacecraft is collected over all phases in the lifecycle of a project. A lot of this information is exchanged between different engineering tasks and business processes. In some lifecycle phases Model Based Systems Engineering (MBSE) has introduced system models and databases that help to organize such information and to keep it consistent for everyone. Nevertheless, none of the existing databases approached the whole lifecycle yet. Virtual Satellite is the MBSE database developed at DLR. It has been used for quite some time in Phase A studies and is currently extended for implementing it in the whole lifecycle of spacecraft projects. Since it is unforeseeable which future use cases such a database needs to support in all these different projects, the underlying data model has to provide tailoring and extension mechanisms to its Conceptual Data Model (CDM). This paper explains the mechanisms as they are implemented in Virtual Satellite, which enables extending the CDM along the project without corrupting already stored information. As an upcoming major use case, Virtual Satellite will be implemented as MBSE tool in the S2TEP project. This project provides a new satellite bus for internal research and several different payload missions in the future. This paper explains how Virtual Satellite will be used to manage configuration control problems associated with such a multi-mission platform. It discusses how the S2TEP project starts using the software for collecting the first design information from concurrent engineering studies, then making use of the extension mechanisms of the CDM to introduce further information artefacts such as functional electrical architecture, thus linking more and more processes into an integrated MBSE approach. |
Olaf Maibaum, Thomas Terzibaschian, Christian Raschke, Andreas Gerndt Deduced Software Design Principles from Experiences with the Technical Debt in Reused Software (Inproceedings) In: Rainer Sandau, Klaus Brieß, Eberhard Gill (Ed.): 11th International Symposium on Small Satellite for Earth Observation, Berlin, April 24-28, 2017, pp. 389–392, Wissenschaft und Technik, 2017. @inproceedings{MAIB17,Software reuse conserves software design decisions for the future, but technology evolves over time. Previous design decisions thereby become technical debt in designs for future projects in the case of software reuse. This may result in risk and cost increases for future projects. The small satellite BIROS is an example of such a project and is examined in this paper. The reused software prohibits state-of-the-art test techniques without significant modification to the software architecture, which is not a software reuse. The necessary changes in the software architecture are presented in this paper and how it protects against faults that arose during the system test and commissioning phase. |
Yang Liu, Meenakshi Deshmukh, Jan C. Wulkop, Philipp M. Fischer, Andreas Gerndt Real-time Immersive Visualization for Satellite Configuration and Version Comparison (Inproceedings) In: Simulation and EGSE for European Space Programmes (SESP 2017), European Space Agency (ESA) Workshop, Noordwijk, The Netherlands, March 28-30, 2017, ESA 2017. @inproceedings{LIU17,Spacecraft design and development is a complex Task which requires a long lifecycle and many phases of iterative construction. Thus, there are usually many versions of configuration design evolving over time. A clear understanding and comparison of these different Versions of spacecraft configurations can bring benefits to both stakeholders and domain experts of the project. However, usually the configuration and system data is stored in textual format in tables and in files which is not efficient to compare results by checking all the subsystem and parameters in different versions one by one. As an alternative, this paper gives a detailed insight how to compare versions by means of 3D visualization and Virtual Reality (VR) technologies. The basis of our approach is the Virtual Satellite (VirSat) which is the standard tool for concurrent engineering studies at the German Aerospace Center (DLR). The key performance indicators of an early space mission design are the mass, the power consumption, and the temperature. In order to Highlight differences of these quantities and distribution of key performance indicators, the VirSat uses color coding for more intuitive understanding. To analyze the changes of geometry information, additional two visualization modes have been integrated for comparing and indicating the differences between versions. In the first mode, two versions of configurations are visually overlapped. The differences are indicated by special colors. In the second mode, different versions of the design yield a successive animation in order to follow the design evolution. Both modes require model transformation from VirSat's central system data model to visualization model which is used for appropriate visualization approaches. The paper gives a detailed architectural overview and discusses benefits and future opportunities. |
2016 |
Turgay Aslandere, Markus Flatken, Andreas Gerndt Simulation of Hard Shadows on Large Spherical Terrains (Journal Article) In: 3D Research, Springer-Verlag, Berlin - Heidelberg, vol. 7, no. 4, 2016. @article{ASLA16,Real-time rendering of high precision shadows using digital terrain models as input data is a challenging task. Especially when interactivity is targeted and Level of Detail (LoD) data structures are utilized to tackle huge amount of data. In this paper, we present a real-time rendering approach for the computation of hard shadows using large scale digital terrain data obtained by satellite imagery. Our approach is based on an extended horizon mapping algorithm that avoids costly pre-computations and ensures high accuracy. This algorithm is further developed to handle large data. The proposed algorithms take the surface curvature of the large spherical bodies into account during the computation. The performance issues are discussed and the results are presented. The generated images can be exploited in 3D research and aerospace related areas. |
Ting Peng, Benjamin Weps, Kilian Höflinger, Kai Borchers, Daniel Lüdtke, Andreas Gerndt A New SpaceWire Protocol for Reconfigurable Distributed On-Board Computers (Inproceedings) In: International SpaceWire Conference, Yokohama, Japan, October 25-27, 2016, pp. 175–182, IEEE, 2016. @inproceedings{PENG16b,There are several standardized protocols based on SpaceWire which provide data exchange between several nodes. SpaceWire is also suitable for interprocess communication (IPC), by the help of higher level protocols. However, currently there is no standardized protocol which is targeting IPC on SpaceWire networks. This paper proposes a protocol, which uses the capabilities of SpaceWire to build up networks for distributed computing on a spacecraft. The core of this protocol is the IPC mechanism for communication between the nodes and methods to support a reconfiguration of the network. A key feature of this protocol is an interface for a reconfiguration mechanism, which can be implemented on application level. This enables the utilization of unreliable commercial off the shelf (COTS) nodes, allowing system recovery from erroneous state. Additionally, the reconfiguration can be used to adapt the distributed computer to different mission phases. The protocol has the potential to build the foundation of a distributed on-board computer consisting of COTS components. Such distributed computer could be capable of fulfilling high performance demands as well as high reliability needs. Though, the protocol itself is not restricted to be used solely in fully-featured reconfigurable distributed systems. The IPC methods can be applied stand-alone as well, to establish a lightweight communication between nodes on a SpaceWire network by excluding the reconfiguration parts of the protocol. |
Philipp M. Fischer, Meenakshi Deshmukh, Volker Maiwald, Dominik Quantius, Antonio Martelo Gomez, Andreas Gerndt Conceptual Data Model - A Foundation For Successful Concurrent Engineering (Inproceedings) In: 7th International Systems & Concurrent Engineering for Space Applications Conference (SECESA), Madrid, Spain, October 5-7, 2016, ESA 2016. @inproceedings{FISC16b,Today, Phase A studies of future space systems are often conducted in special design facilities such as the Concurrent Engineering Facility (CEF) at the German Aerospace Center (DLR). Within these facilities the studies are performed following a defined process making use of a data model for information exchange. Quite often it remains unclear what exactly such a data model is and how it is implemented and applied. Nowadays, such a data model is implemented as software using a formal specification describing its capabilities within a so called meta-model. This meta-model, often referred as Conceptual Data Model (CDM), is finally used and instantiated as System Model during these CE studies. Such software provides a user interface for instantiating and sharing the System Model within the design team and provides capabilities to analyze the System Model on the fly. This is possible due to the semantics of the underlying CDM creating a common language used to exchange and process design information. This paper explains the implementation of the data model at DLR and shows information how it is applied in the concurrent engineering process of the CEF. It highlights important aspects concerning the modeling capabilities during a study and discusses how they can be implemented into a corresponding CDM. Accordingly the paper presents important aspects such as rights management and data consistency and the implications of them to the software's underlying technology. A special use case of the data model is depicted and shows the flexibility of the implementation proven by a study of a multi module space station. |
Ting Peng, Kilian Höflinger, Benjamin Weps, Olaf Maibaum, Kurt Schwenk, Daniel Lüdtke, Andreas Gerndt A Component-Based Middleware for a Reliable Distributed and Reconfigurable Spacecraft Onboard Computer (Inproceedings) In: 35th Symposium on Reliable Distributed Systems (SRDS), Budapest, Hungary, September 26-29, 2016, pp. 337–342, IEEE, 2016, (Short Paper). @inproceedings{PENG16a,Emerging applications for space missions require increasing processing performance from the onboard computers. DLR's project ``Onboard Computer - Next Generation'' (OBC-NG) develops a distributed, reconfigurable computer architecture to provide increased performance while maintaining the high reliability of classical spacecraft computer architectures. Growing system complexity requires an advanced onboard middleware, handling distributed (realtime) applications and error mitigation by reconfiguration. The OBC-NG middleware follows the Component-Based Software Engineering (CBSE) approach. Using composite components, applications and management tasks can easily be distributed and relocated on the processing nodes of the network. Additionally, reuse of components for future missions is facilitated. This paper presents the flexible middleware architecture, the composite component framework, the middleware services and the model-driven Application Programming Interface (API) design of OBC-NG. Tests are conducted to validate the middleware concept and to investigate the reconfiguration efficiency as well as the reliability of the system. A relevant use case shows the advantages of CBSE for the development of distributed reconfigurable onboard software. |
Philipp M. Fischer, Daniel Lüdtke, Caroline Lange, Frank-Cyrus Roshani, Frank Dannemann, Andreas Gerndt Implementing Model Based System Engineering for the Whole Lifecycle of a Spacecraft (Inproceedings) In: Deutscher Luft- und Raumfahrtkongress (DLRK), Braunschweig, Germany, September 13-15, 2016, Deutsche Gesellschaft für Luft- und Raumfahrt - Lilienthal-Oberth e.V., 2016. @inproceedings{FISC16a,Design information of a spacecraft is collected over all phases in the lifecycle of a project. A lot of this information is exchanged between different engineering tasks and business processes. In some lifecycle phases Model Based System Engineering (MBSE) has introduced system models and databases that help to organize such information and to keep it consistent for everyone. Nevertheless, none of the existing databases approached the whole lifecycle yet. Virtual Satellite is the MBSE database developed at DLR. It has been used for quite some time in Phase A studies and is currently extended for implementing it in the whole lifecycle of spacecraft projects. Since it is unforeseeable which future use-cases such a database actually needs to support in all these different projects, the underlying data model has to provide tailoring and extension mechanisms to its Conceptual Data Model (CDM). These mechanisms as they are implemented in Virtual Satellite enable extending the CDM along the project without corrupting already stored information. As an upcoming major use-case, Virtual Satellite will be implemented as MBSE tool in the S2TEP project. This project provides a new satellite bus for internal research and several different payload missions in the future. Virtual Satellite will be used to manage configuration control problems associated with such a multi mission platform. The S2TEP project will also start using it for collecting the first design information from concurrent engineering studies, then making use of the extension mechanisms of the CDM to introduce further information artefacts such as functional electrical architecture, thus linking more and more processes into an integrated MBSE approach. |
Tobias Franz, Daniel Lüdtke, Olaf Maibaum, Andreas Gerndt Model-Based Software Engineering for an Optical Navigation System for Spacecraft (Inproceedings) In: Deutscher Luft- und Raumfahrtkongress (DLRK), Braunschweig, Germany, September 13-15, 2016, Deutsche Gesellschaft für Luft- und Raumfahrt - Lilienthal-Oberth e.V., 2016. @inproceedings{FRAN16,The project ATON (Autonomous Terrain-based Optical Navigation) at the German Aerospace Center (DLR) is developing an optical navigation system for future landing missions on celestial bodies such as the Moon or asteroids. Image data obtained by optical sensors can be used for autonomous determination of the spacecraft's position and attitude. Camera-in-the-loop experiments in the TRON (Testbed for Robotic Optical Navigation) laboratory and flight campaigns with unmanned aerial vehicle (UAV) are performed to gather flight data for further development and to test the system in a closed-loop scenario. The software modules are executed in the C++ Tasking Framework that provides the means to concurrently run the modules in separated tasks, send messages between tasks, and schedule task execution based on events. Since the project is developed in collaboration with several institutes in different domains at DLR, clearly defined and well-documented interfaces are necessary. Preventing misconceptions caused by differences between various development philosophies and standards turned out to be challenging. After the first development cycles with manual Interface Control Documents (ICD) and manual implementation of the complex interactions between modules, we switched to a model-based approach. The ATON model covers a graphical description of the modules, their parameters and communication patterns. Type and consistency checks on this formal level help to reduce errors in the system. The model enables the generation of interfaces and unified data types as well as their documentation. Furthermore, the C++ code for the exchange of data between the modules and the scheduling of the software tasks is created automatically. With this approach, changing the data flow in the system or adding additional components (e.g. a second camera) have become trivial. |
Johannes Hummel, Janki Dodiya, Laura Eckardt, Robin Wolff, Andreas Gerndt, Torsten W. Kuhlen A Lightweight Electrotactile Feedback Device for Grasp Improvement in Immersive Virtual Environments (Inproceedings) In: Tobias Höllerer, Victoria Interrante, Anatole Lécuyer, Evan Suma (Ed.): IEEE Virtual Reality Conference (VR), Greenville, SC, USA, March 19-23, 2016, pp. 39–48, IEEE, 2016. @inproceedings{HUMM16,An immersive virtual environment is the ideal platform for the planning and training of on-orbit servicing missions, as it provides a flexible and safe environment. In such kind of virtual assembly simulation, grasping virtual objects is one of the most common and natural interactions. However, unlike grasping objects in the real world, it is a non-trivial task in virtual environments, where the primary feedback is visual only. A lot of research investigated ways to provide haptic feedback, such as force, vibrational and electrotactile feedback. Such devices, however, are usually uncomfortable and hard to integrate in projection-based immersive YR systems. In this paper, we present a novel, small and lightweight electro-tactile feedback device, specifically designed for immersive virtual environments. It consists of a small tactor with eight electrodes for each finger and a signal generator attached to the user's hand or arm. Our device can be easily integrated with an existing optical finger tracking system. The study presented in this paper assesses the feasibility and usability of the interaction device. An experiment was conducted in a repeated measures design using the electrotactile feedback modality as independent variable. As benchmark, we chose three typical assembly tasks of a YR simulation for satellite on-orbit servicing missions, including pressing a button, switching a lever switch, and pulling a module from its slot. Results show that electrotactile feedback improved the user's grasping in our virtual on-orbit servicing scenario. The task completion time was significantly lower for all three tasks and the precision of the user's interaction was higher. The workload reported by the participants was significantly lower when using electrotactile feedback. Additionally, users were more confident with their performance while completing the tasks with electrotactile feedback. We describe the device, outline the user study and report the results. |
Jafar Akhundov, Matthias Werner, Volker Schaus, Andreas Gerndt Using Timed Automata to Check Space Mission Feasibility in the Early Design Phases (Inproceedings) In: IEEE Aerospace Conference, Yellowstone Conference Center, Big Sky, MT, USA, March 5-12, IEEE, 2016. @inproceedings{Akhundov2016,According to the model-based systems engineering paradigm, all engineers contribute to a single centralized data model of the system. The German Aerospace Center (DLR) develops a software tool Virtual Satellite which enables the engineers to store, exchange and alter their corresponding subsystem data on base of a distributed system model and thus contribute to the overall mission design during concurrent engineering (CE) sessions. Each engineer has their own scope of responsibilities, e.g. satellite trajectory, communication, or thermal analysis. Tracking implications of design changes on the whole system and feasibility aspects of the design is not trivial. Having an automated feasibility checking mechanism as a part of CE which would run iteratively after each design change provides a useful feedback mechanism for engineers and for the spacecraft client. For the purpose of mission feasibility checking a domain specific language (DSL) has been implemented using the Xtext Java framework. The extended parametric data model defined in the DSL serves as an executable representation of the spacecraft mission. The idea to use such an executable model to create a preliminary mission plan and hence confirm missions feasibility during conceptual study has already been introduced by Schaus et al. at the DLR. However, the vector of values of system variables was assumed to be equivalent with the currently active component, implying that component activities are mutually exclusive. This led to over-constraining of the execution model. Our work argues that concurrency considerations are critical from the earliest design phases. Since satellite is coupled with its environment and concurrency is an intrinsic property of the physical nature, considering concurrency allows for more realistic mission plans. The contributions of this paper are the introduction of concurrency considerations at the early space mission design phases and the use of timed automata tool (UPPAAL) for the mission feasibility check during concurrent engineering sessions. As a result, with almost no overhead, the planned mission can be analyzed in a more realistic way. Furthermore, the run-times of the feasibility check amount to 10-100 milliseconds or less, which is also a significant improvement with respect to the previous work. This allows for more precision and fine granular modeling, and is a promising basis for model refinements in the consecutive mission design phases. |
Heike Benninghoff, Kai Borchers, Anko Börner, Michael Dumke, Görschwin Fey, Andreas Gerndt, Kilian Höflinger, Jörg Langwald, Daniel Lüdtke, Olaf Maibaum, Ting Peng, Kurt Schwenk, Benjamin Weps, Karsten Westerdorff OBC-NG Concept and Implementation (Technical Report) Deutsches Zentrum für Luft- und Raumfahrt (DLR) no. DLR-FB-2016-3, 2016. @techreport{BENN16,OBC-NG is the abbreviation for on-board-computer next generation -- a project founded and made by the German Aerospace Center (DLR). The project goal is to provide the basis for future on-board computer (OBC) for space-missions. This document summarizes the conducted work, made in the DLR-project OBC-NG and its predecessor project ``Software and Hardware Architecture for Re-configurable Computers''. |
2015 |
Turgay Aslandere, Markus Flatken, Andreas Gerndt A Real-Time Physically Based Algorithm for Hard Shadows on Dynamic Height-Fields (Inproceedings) In: André Hinkenjann, Jens Maiero, Roland Blach (Ed.): Virtuelle und Erweiterte Realität, 12. Workshop der GI-Fachgruppe VR/AR, Sankt Augustin, Germany, September 10-11, 2015, pp. 101–112, Shaker Verlag, Aachen, 2015. @inproceedings{ASLA15,Bump maps are commonly used in computer graphics to visualize bumps and wrinkles on the surface of an object, more specifically, in height-field rendering. In order to render shadows for large terrain data using bump maps, various methods such as horizon mapping have been suggested. A horizon map describes the occlusion of terrain data by using angles with respect to a view point. In this paper, we propose a method exploiting ideas from horizon mapping to generate real time shadows for large terrain data. We only consider a single azimuth direction per height-field point to compute the shadows. The generated horizon map is computed in real time and allows for interactive exploration of the terrain. We demonstrate that our method produces accurate results while keeping the memory requirements low |
Meenakshi Deshmukh, Robin Wolff, Philipp M. Fischer, Markus Flatken, Andreas Gerndt Interactive 3D Visualization to Support Concurrent Engineering in the Early Space Mission Design Phase (Inproceedings) In: Challenges in European Aerospace (CEAS), CEAS Air & Space Conference, Delft, The Netherlands, September 7-11, 2015, Council of European Aerospace Societies (CEAS), 2015. @inproceedings{DESH15b,The development of space systems involves complex interdisciplinary systems engineering. The concurrent engineering (CE) approach has been successfully applied to the early design phase of space missions. To bridge the gap between the development phases and between the different domain experts, a model based system engineering (MBSE) approach is showing promising results. To support CE and MBSE during space mission development, the German Aerospace Center (DLR) has started developing a new tool called Virtual Satellite. It offers extended software support required by CE for inter-domain communication, data exchange, dependency analysis, on the fly data analysis, data consistency while maintaining a common system model based on the MBSE approach. However, the general issues of inter-domain communication and understanding still exist and may lead to misinterpretation. To overcome this problem it is intended to take advantage of interactive 3D visualization and Virtual Reality techniques to visualize the complex system model and, thus, provide a common understanding of the system model and the intrinsic domain knowledge. Furthermore, this will promote the experts to communicate their ideas and improve the visibility of potential design issues. The paper describes the efforts taken at DLR in this direction, architecture details and advantages of adopting these techniques into space mission development from the early design phase. |
Markus Flatken, Jonas Merkel, Anne Berres, Ingrid Hotz, Andreas Gerndt, Hans Hagen Dynamic Scheduling for Progressive Large-Scale Visualisation (Inproceedings) In: Enrico Bertini, Jessie Kennedy, Enrico Puppo (Ed.): Eurographics Conference on Visualization (EuroVis), Short Papers, Cagliari, Italy, May 25-29, 2015, pp. 37–41, The Eurographics Association, 2015. @inproceedings{FLAT15,The ever-increasing compute capacity of high-performance systems enables scientists to simulate physical phenomena with a high spatial and temporal accuracy. Thus, the simulation output can yield dataset sizes of many terabytes. An efficient analysis and visualization process becomes very difficult especially for explorative scenarios where users continuously change input parameters. Using a distributed rendering pipeline may relieve the visualization frontend considerably but is often not sufficient. Therefore, we additionally propose a progressive data streaming and rendering approach. The main contribution of our method is the importance-guided order of data processing for block structured datasets. This requires a dynamic scheduling of data chunks on the parallel post-processing system which has been implemented by using an R-Tree. In this paper, we demonstrate the efficiency of our implementation for view-dependent feature extraction with varying viewpoints. |
Meenakshi Deshmukh, Benjamin Weps, Pedro Azevedo Isidro, Andreas Gerndt Model Driven Language Framework to Automate Command and Data Handling Code Generation (Inproceedings) In: IEEE Aerospace Conference, Big Sky, MT, USA, March 7-14, 2015, pp. 1–9, IEEE, 2015. @inproceedings{DESH15a,On-board computer software (OBSW) is an integral part of every space mission. It has been continuously growing in size and complexity. The insufficient level of automation in the development process of such software leads to low software re-usability and drives up the costs. This paper presents a generic approach to describe and model the on-board software in terms of data that is processed by it. Domain Specific Language (DSL) based framework is developed using which provides a DSL editor, a model validator, and a code generator. Using the framework, a system data model is created. The C++ code is generated from it which is then customized to implement low-level behavior. As a proof of concept, the telecommand handling functionality of OBSW is developed to prove the feasibility of applying the solution to the whole system. Based on the analysis conducted on the source code of the TET-1 satellite of the German Aerospace Center (DLR), a DSL is designed and implemented. The resulting DSL-based framework is tested with an example model and target code customization, showing its ease of use and proving that it behaves as expected. |
Mikel Sagardia, Katharina Hertkorn, Thomas Hulin, Simon Schätzle, Robin Wolff, Johannes Hummel, Janki Dodiya, Andreas Gerndt VR-OOS: The DLR's Virtual Reality Simulator for Telerobotic On-Orbit Servicing with Haptic Feedback (Inproceedings) In: IEEE Aerospace Conference, Big Sky, MT, USA, March 7-14, 2015, IEEE, 2015. @inproceedings{SAGA15,The growth of space debris is becoming a severe issue that urgently requires mitigation measures based on maintenance, repair, and de-orbiting technologies. Such on-orbit servicing (OOS) missions, however, are delicate and expensive. Virtual Reality (VR) enables the simulation and training in a flexible and safe environment, and hence has the potential to drastically reduce costs and time, while increasing the success rate of future OOS missions. This paper presents a highly immersive VR system with which satellite maintenance procedures can be simulated interactively using visual and haptic feedback. The system can be used for verification and training purposes for human and robot systems interacting in space. Our framework combines unique realistic virtual reality simulation engines with advanced immersive interaction devices. The DLR bimanual haptic device HUG is used as the main user interface. The HUG is equipped with two light-weight robot arms and is able to provide realistic haptic feedback on both human arms. Additional devices provide vibrotactile and electrotactile feedback at the elbow and the fingertips. A particularity of the realtime simulation is the fusion of the Bullet physics engine with our haptic rendering algorithm, which is an enhanced version of the Voxmap-Pointshell Algorithm. Our haptic rendering engine supports multiple objects in the scene and is able to compute collisions for each of them within 1 msec, enabling realistic virtual manipulation tasks even for stiff collision configurations. The visualization engine ViSTA is used during the simulation to achieve photo-realistic effects, increasing the immersion. In order to provide a realistic experience at interactive frame rates, we developed a distributed system architecture, where the load of computing the physics simulation, haptic feedback and visualization of a complex scene is transferred to dedicated machines. The implementations are presented in detail and the performance of the overall system is validated. Additionally, a preliminary user study in which the virtual system is compared to a physical test bed shows the suitability of the VR-OOS framework. |
Arturo Garcia, David Roberts, Terrence Fernando, Christian Bar, Robin Wolff, Janki Dodiya, Wito Engelke, Andreas Gerndt A Collaborative Workspace for Strengthening Collaboration among Space Scientists (Inproceedings) In: IEEE Aerospace Conference, Big Sky, MT, USA, March 7-14, 2015, IEEE, 2015. @inproceedings{GARC15,Space exploration missions have produced large data of immense value, to both research and the planning and operating of future missions. However, current datasets and simulation tools fragment teamwork, especially across disciplines and geographical location. The aerospace community already exploits virtual reality for purposes including space tele-robotics, interactive 3D visualization, simulation and training. However, collaborative virtual environments are yet to be widely deployed or routinely used in space projects. Advanced immersive and collaborative visualization systems have the potential for enhancing the efficiency and efficacy of data analysis, simplifying visual benchmarking, presentations and discussions. We present preliminary results of the EU funded international project CROSS DRIVE, which develops an infrastructure for collaborative workspaces for space science and missions. The aim is to allow remote scientific and engineering experts to collectively analyze and interpret combined datasets using shared simulation tools. The approach is to combine advanced 3D visualization techniques and interactive tools in conjunction with immersive virtuality telepresence. This will give scientists and engineers the impression of teleportation from their respective buildings across Europe, to stand together on a planetary surface, surrounded by the information and tools that they need. The conceptual architecture and proposed realization of the collaborative workspace are described. ESA's planned ExoMars mission provides the use-case for deriving user requirements and evaluating our implementation. |
2014 |
Volker Schaus, Daniel Lüdtke, Philipp M. Fischer, Andreas Gerndt Collaborative Modeling and Simulation in Spacecraft Design (Incollection) In: Daniele Gianni, Andrea D'Ambrogio, Andreas Tolk (Ed.): Modeling and Simulation-Based Systems Engineering Handbook, pp. 149–179, CRC Press, 2014. @incollection{SCHA14b,Introduction Collaboration is a key factor for successful development of spacecraft. It is a broad term and has many meanings because exchange of information is needed all along the development life cycle. A successful design directly depends on sharing necessary information with others and, on the other hand, comprehending and using relevant information as input for your own work. Modeling and simulation is extensively used in spacecraft design and appears in many different varieties throughout the whole development life cycle. It covers a wide range, from simple orbit simulations based on analytical equations to high-fidelity and multidomain simulations using distributed high-performance computers. In today's large-scale, complex projects, traditional engineering approaches reach... |
Daniele Gianni, Andrea D'Ambrogio, Volker Schaus, Andreas Gerndt, Marco Lisi, Pierluigi De Simone Interface Management in Concurrent Engineering Facilities for Systems and Service Systems Engineering: A Model-based Approach (Inproceedings) In: Italian INCOSE Conference on Systems Engineering (CIISE), Rome, Italy, November 24-25, 2014, pp. 72–81, INCOSE Italia 2014. @inproceedings{GIAN14b,Concurrent engineering facilities (CEFs) are successfully used in the aeropsace sector to design systems and services that that fulfill the requirements. Model-based systems engineering (MBSE) enables the effective (i.e., unambiguous) communication in the collaborative activities within concurrent engineering and service systems engineering facilities. The advantages obtained by the MBSE approach can be further scaled up by an innovative approach that take into explicit account the representation of the inter-systems aspects, i.e., those aspects, namely interfacs, that stay in between the system, its sub-systems and external entities (other systems and organizations). Such an approach, briefly denoted as a Model-based Interface Engineering (MBIE), brings several benefits to the CEF activities. This paper illustrates the integration of the Interface Communication Modelling Language (ICML) into the existing MBSE methods for the CEF software framework VirSat, by identifying the business needs driving the use of MBIE approaches and showing example application scenarios. |
Daniele Gianni, Volker Schaus, Andrea D'Ambrogio, Andreas Gerndt, Marco Lisi, Pierluigi DeSimone In: 6th International Conference on Systems & Concurrent Engineering for Space Applications (SECESA), Stuttgart, Germany, October 8-10, 2014, ESA 2014. @inproceedings{GIAN14a, |
Volker Schaus, Juliane Müller, Meenakshi Deshmukh, Andy Braukhane, Andreas Gerndt Bidirectional Graphical Modelling Supporting Concurrent Spacecraft Design (Inproceedings) In: 6th International Conference on Systems & Concurrent Engineering for Space Applications (SECESA), Stuttgart, Germany, October 8-10, 2014, ESA 2014. @inproceedings{SCHA14a,A graphical representation of the system under design in form of diagrams is a powerful way to present complex relationships. Diagrams appear in almost every concurrent design activity in some way sooner or later in the process. Generally they help to explain the design or give an overview so that the other stakeholders can quickly understand a (sub-) system build-up or a proposed solution. Furthermore diagrams are also important for documentation purposes (presentations, reports, interface control documents). Typically the diagrams are made in some external tool and the content is not linked to the constantly changing system model. Especially considering the fast pace of concurrent design studies, such diagrams become quickly inconsistent and outdated, thus breaking the model-based paradigm. This is the motivation for the work presented in this paper to include basic support for graphical modeling within the Model-based System Engineering tool called Virtual Satellite. The paper presents three different diagram types, explains their content and relevance for concurrent engineering sessions. It further mentions implementation details and the used technologies to include bidirectional graphical modeling editors in the Virtual Satellite software. |
Achim Basermann, Gregor Matura, Fang Chen, Andreas Gerndt, Martin Aumüller, Derek Groen ExaScale Pre- and Post-Processing - Strategy and Software Technology (Technical Report) CRESTA Consortium no. 3, 2014. @techreport{BASE14,Today's large-scale simulations deal with complex geometries and numerical data on an extreme scale. As computation approaches the exascale, it will no longer be possible to write and store full-sized result data sets. In-situ data analysis and scientific visualisation provide feasible solutions to the analysis of complex large-scale simulations. To bring pre- and post-processing to the exascale we must consider modifications to data structure and memory layout, and address latency and error resiliency. Load balancing is a crucial pre-processing task on extremely parallel systems. Here, our focus is on a load balancing strategy that supports multiple simulation phases and includes their costs to calculate a data distribution that leads to an optimal performance for the full simulation. The software library PPStee developed in CRESTA already incorporates this idea. It was explicitly designed to support multiple simulation phases. The user provides communication costs of a simulation phase represented as edge weights of a graph corresponding to the simulation data. The according computation costs of the phase are matched to vertex weights. As multiple weight sets can be included, the partitioning of the simulation data is calculated to achieve an optimal load balance covering the full simulation cycle. PPStee supports various partitioning tools, repartitioning and improved initial data distributions by exploiting knowledge from previous simulation runs. PPStee was successfully integrated into several large-scale fluid simulation codes. Here, we demonstrate the flexibility of PPStee with the hemodynamic simulation code HemeLB. In-situ processing has become a key concept in exascale data post-processing and visualisation. Waiting for a simulation to finish and writing out huge amounts of simulation output is no longer a viable solution for data analysis. Instead, visualisation and data analysis must happen when and where a certain simulation step has been carried out, as the so-called in-situ processing. Our in-situ processing system provides scalable distributed post-processing. This system supports on-the-fly data analysis and user interaction to on-going simulations. Here, we demonstrate the feasibility of our system by an online-monitoring scenario with the hemodynamic simulation code HemeLB. Remote hybrid rendering (RHR) is used to access remote exascale simulations from immersive projection environments over the Internet. The display system may range from a desktop computer to an immersive virtual environment such as a CAVE. The display system forwards user input to the visualisation cluster, which uses highly scalable methods to render images of the post-processed simulation data and returns them to the display system. The display system enriches these with context information rendered locally, before they are shown. RHR decouples local interaction from remote rendering and thus guarantees smooth interactivity during exploration of large remote data sets. Here, we discuss strategies, algorithms and techniques for RHR in exascale scenarios and present performance measurements for a prototype developed in CRESTA. For performance analysis, the prototype has been instrumented to collect timing information, compression ratios and image quality metrics. |
Markus Flatken, Christian Wagner, Andreas Gerndt Distributed Post-Processing and Rendering for Large-Scale Scientific Simulations (Incollection) In: Charles D. Hansen, Min Chen, Christopher R. Johnson, Arie E. Kaufman, Hans Hagen (Ed.): Scientific Visualization: Uncertainty, Multifield, Biomedical, and Scalable Visualization, pp. 381–398, Springer, London, 2014. @incollection{FLAT14b,With the ever-increasing capacity of high-performance computing (HPC) systems, computational simulation models become finer and more accurate. The size and complexity of the data produced, however, pose tremendous challenges for the visualization and analysis tasks. Explorative approaches, in particular, require the development of interactive human-computer interfaces using distributed and parallel post-processing architectures. Such infrastructures can also be used for the interaction with running simulations, with applications ranging from online monitoring to computational steering. Additionally, remote and parallel rendering can be integrated into the overall setup. This chapter gives an overview of current solutions and ongoing research activities in this domain. |
Meenakshi Deshmukh, René Schwarz, Andy Braukhane, Rosa Paris Lopez, Andreas Gerndt Model Linking to Improve Visibility and Reusability of Models during Space System Development (Inproceedings) In: IEEE Aerospace Conference, Big Sky, MT, USA, March 1-8, 2014, IEEE, 2014. @inproceedings{DESH14,The development of space systems involves complex interdisciplinary systems engineering. To manage such complexity, simulation and calculation models are becoming an integral part of it, where different domain-specific models (power, thermal, structure, propulsion, communication, etc.) are developed using different tools. Every domain model contains valuable knowledge of a respective discipline. However, creating such models takes an ample amount of time and efforts. Therefore, a common management for these models is needed to preserve the knowledge and to reuse them in future space missions. The project Simulation Model Library (SimMoLib) at the German Aerospace Center (DLR) develops guidelines and best practices regarding model development, model documentation, validation and verification, as well as model reviews to establish a collection of reusable models. To efficiently catalog the models, an innovative software system is created to support collaborative development, submission, archiving, review, search, and utilization of models. In SimMoLib, a model linking concept has been developed and implemented to enhance the model search and their probable reuse. Along with regular keyword-based search, a direct and an indirect linking between the models in the library has been implemented. Therefore, the model linking increases the visibility and consequently promotes the reuse of single and interdependent models within the library. The paper further describes different types of model relationships, categories, hierarchical levels of model development, implementation and presentation of model linking in detail. |
Daniel Lüdtke, Karsten Westerdorff, Kai Stohlmann, Anko Börner, Olaf Maibaum, Ting Peng, Benjamin Weps, Görschwin Fey, Andreas Gerndt OBC-NG: Towards a Reconfigurable On-board Computing Architecture for Spacecraft (Inproceedings) In: IEEE Aerospace Conference, Big Sky, MT, USA, March 1-8, 2014, IEEE, 2014. @inproceedings{LUED14,The computational demands on spacecraft are rapidly increasing. Current on-board computing components and architectures cannot keep up with the growing requirements. Only a small selection of space-qualified processors and FPGAs are available and current architectures stick with the inflexible cold-redundant structure. The objective of the ongoing project OBC-NG (On-board Computer - Next Generation) is to find new concepts for on-board-computer to fulfill future requirements. The concept presented in this paper is based on a distributed reconfigurable system, consisting of different nodes for processing, management and interface operations. OBC-NG will exploit the high performance of commercial off-the-shelf (COTS) hardware parts. To compensate the shortcomings of COTS parts the OBC-NG redundancy approach differs from the classic way and error mitigation techniques will work mainly on software level. This paper discusses the hardware and software architecture of the system as well as the redundancy and reconfiguration concept. Our ideas will be proven in an OBC-NG prototype, planned for the next year. |
Robin Wolff, Carsten Preusche, Andreas Gerndt A Modular Architecture for an Interactive Real-time Simulation and Training Environment for Satellite On-orbit Servicing (Journal Article) In: Journal of Simulation (JOS), Palgarve Macmillan, UK, vol. 8, no. 1, pp. 50–63, 2014. @article{WOLF14,Maintaining or repairing satellites in orbit is a delicate task that requires expert skills. The planning, training and analysis of on-orbit servicing (OOS) missions performed by astronauts or through remote operation using a robot is often time consuming and costly. Virtual Reality (VR) enables simulation and training in a flexible and safe environment. This paper describes an interactive real-time environment that supports a number of OOS tasks within an immersive VR environment. The system simulates the dynamic and kinematic behaviour of satellite components and provides photo-realistic visualization of satellite parts and the space environment. It integrates user interaction with haptic force feedback through a bi-manual haptic human machine interface, as well as simulates and interfaces to a humanoid robot for tele-operation.In order to provide a realistic experience at interactive frame rates, we propose a distributed system architecture, where the load of computing the physics simulation, haptic feedback and visualization of the complex scene is transferred to dedicated machines. The modular architecture is designed to allow the inclusion of further simulation processes. Several mechanisms for reducing the communication traffic have been implemented. This paper gives an overview of the system architecture, outlines the software implementation and documents an evaluation of the real-time performance of our system in detail. We describe how system performance was measured in terms of simulation timings and distribution load, as well as report on latencies at several stages. Results show that our distributed system is capable of providing visual and haptic feedback at high frame rates required for user interaction with end-to-end latencies of less than 8ms and 3ms, respectively. |
Andreas Gerndt, Janki Dodiya, Katharina Hertkorn, Thomas Hulin, Johannes Hummel, Mikel Sagardia, Robin Wolff Fallbeispiel für VR/AR - Virtuelle Satellitenreparatur im Orbit (Incollection) In: Ralf Dörner, Wolfgang Broll, Paul Grimm, Bernhard Jung (Ed.): Virtual und Augmented Reality (VR/AR) - Grundlagen und Methoden der Virtuellen und Augmentierten Realit"at, eXamen.press, pp. 303–305, Springer Vieweg, 2014. @incollection{GERN14, |
2013 |
Johannes Hummel, Janki Dodiya, Robin Wolff, Andreas Gerndt, Torsten Kuhlen Usability Evaluation of Two Simple Methods for Representing Heaviness of Virtual Objects (Inproceedings) In: Marc Erich Latoschik, Oliver Staadt, Frank Steinicke (Ed.): Virtuelle und Erweiterte Realität, 10. Workshop der GI-Fachgruppe VR/AR, Würzburg, September 19-20, 2013, pp. 157–168, Shaker Verlag, 2013. @inproceedings{HUMM13b,Perception of heaviness of virtual objects can play an important role in improving the user interaction within virtual environments. It could especially prove beneficial in applications, such as virtual assembly and medical surgery, which largely consist of selection, manipulation and grasping tasks. In order to achieve weight perception in virtual environments, haptic devices have been commonly used. However, they are hard to incorporate into immersive virtual environments (IVEs) due to their functional complexity. This paper evaluates the usability of two simple interaction approaches using a light-weight finger-tracking device. One method is based on the distance between tracked fingers and the thumb, the other uses the intensity of pinching fingers during grasping gestures providing tactile feedback. Building on previous results of evaluating the performance by measuring the Weber fraction, in this paper, we further evaluate usability of our methods as a function of the overall workload placed on the user while performing a sorting task based on perceived weight. The results confirmed that the performance of both methods for the sorting task is comparable and both methods allow distinguishing between the heaviness. However, the experienced workload was higher for the pinch based compared to the distance based method and participants had higher confidence in the distance based method. |
Peter Collienne, Robin Wolff, Andreas Gerndt, Torsten Kuhlen Physically Based Rendering of the Martian Atmosphere (Inproceedings) In: Marc Erich Latoschik, Oliver Staadt, Frank Steinicke (Ed.): Virtuelle und Erweiterte Realität, 10. Workshop der GI-Fachgruppe VR/AR, Würzburg, September 19-20, 2013, pp. 97–108, Shaker Verlag, Aachen, 2013. @inproceedings{COLL13,With the introduction of complex precomputed scattering tables by Bruneton in 2008, the quality of visualizing atmospheric scattering vastly improved. The presented algorithms allowed for the rendering of complex atmospheric features such as multiple-scattering or light shafts in real-time and at interactive framerates. While their published implementation corresponding to the publication was merely a proof of concept, we present a more practical approach by applying their scattering theory to an already existing planetary rendering engine. Because the commonly used set of parameters only describes the atmosphere of the Earth, we further extend the scattering formulation to visualize the atmosphere of the planet Mars. Validating the modified scattering and resulting parameters is then done by comparison with available imagery from the Martian atmosphere. |
Volker Schaus, Michael Tiede, Philipp M. Fischer, Daniel Lüdtke, Andreas Gerndt A Continuous Verification Process in Concurrent Engineering (Inproceedings) In: AIAA Space Conference, San Diego, CA, USA, September 10-12, 2013, 2013. @inproceedings{SCHA13b,This paper presents how a continuous mission verification process similar than in software engineering can be applied in early spacecraft design and Concurrent Engineering. Following the Model-based Systems Engineering paradigm, all engineers contribute to one single centralized data model of the system. The data model is enriched with some extra information to create an executable representation of the spacecraft and its mission. That executable scenario allows for verifications against requirements that have been formalized using appropriate techniques from the field of formal verification. The paper focuses on a current approach of integrating this verification mechanism into our Concurrent Engineering environment. In an example study, we explain how basic mission requirements are created at the beginning of the spacecraft design. After each iteration and change, the integrated verification will be executed. This instantly highlights the effects of the modification and points out potential problems in the design. Using the continuous verification process alongside the Concurrent Engineering process helps to mature both, the requirements and the design itself. |
Volker Schaus, Philipp M. Fischer, Andreas Gerndt Taking Advantage of the Model: Application of the Quantity, Units, Dimension, and Values Standard in Concurrent Spacecraft Engineering (Inproceedings) In: 23rd Annual International Symposium of the International Council of Systems Engineering (INCOSE), Philadelphia, PA, USA, June 24-27, 2013, pp. 878–888, Wiley, 2013. @inproceedings{SCHA13a,Designing a spacecraft involves many experts from different domains. In the early design phases they are brought together to discuss the spacecraft in a short period of time. The elements and building blocks the individual engineers want to use are stored and described in a shared system model provided by a software framework. A lot of features like the masses or dimensions are described using parameters. Due to the various domains and individual preference, many different units are used, leading to mistakes, distraction and misunderstandings caused by unit conversions. Our paper describes a pragmatic approach how the QUDV is integrated into an existing system model. This allows taking advantage of it by automatically analyzing the unit consistency as well as performing automatic conversions. The presented work shows that with a profound integration into the existing software framework, the engineers can overcome the error-prone task of unit checks and conversion problems. |
Olaf Frauenberger, Mirco Tegler, Jens Richter, Holger Maass, Klaus-Dieter Missling, Eckehard Lorenz, Andreas Gerndt The Generalized Processing Chain for BIRD and FireBIRD Mission (Inproceedings) In: Rainer Sandau, Hans-Peter Röser, Arnoldo Valenzuela (Ed.): 9th IAA Symposium Small Satellites for Earth Observations, Berlin, Germany, April 8-12, 2013, Wissenschaft und Technik Verlag Berlin, 2013. @inproceedings{FRAU13,The FireBIRD mission has been designed to detect and monitor dynamic high temperature events, such as wild fires or volcano eruptions. In order to provide calibrated and geo-referenced data in near real time to users, a ground processing system is going to be established and deployed in the downstream chain in the national ground segment in Neustrelitz. The ground processing system consists of the Payload System Management (PSM) and one or more Instrument Processing Facility (IPFs). Due to the experimental nature of small satellite missions the components of the ground system have been often specific solutions. The design of the FireBIRD ground segment uses a modular design with separate control and payload data interfaces. For data interfaces abstract data descriptions are used in order to achieve a mission independent design to a large extend. A design constraint is to separate processing control components from data processing components as far as possible. The goal is to achieve extendibility and reusability of the processing components as well as portability of the IPF to other systems and migration for future missions. |
Olaf Maibaum, Andreas Gerndt Safe Integration of Payload Experiments in an AOCS (Inproceedings) In: Rainer Sandau, Hans-Peter Röser, Arnoldo Valenzuela (Ed.): 9th IAA Symposium on Small Satellites for Earth Observation, Berlin, April 8-12, 2013, pp. 423–426, Wissenschaft & Technik Verlag, 2013. @inproceedings{MAIB13a, |
Johannes Hummel, Janki Dodiya, Robin Wolff, Andreas Gerndt, Torsten Kuhlen An Evaluation of Two Simple Methods for Representing Heaviness in Immersive Virtual Environments (Inproceedings) In: Anatole Lécuyer, Frank Steinicke, Mark Billinghurst (Ed.): IEEE Symposium on 3D User Interfaces (3DUI), Orlando, FL, USA, March 16-17, 2013, pp. 87–94, IEEE, 2013. @inproceedings{HUMM13a,Weight perception in virtual environments generally can be achieved with haptic devices. However, most of these are hard to integrate in an immersive virtual environment (IVE) due to their technical complexity and the restriction of a user's movement within the IVE. We describe two simple methods using only a wireless light-weight finger-tracking device in combination with a physics simulated hand model to create a feeling of heaviness of virtual objects when interacting with them in an IVE. The first method maps the varying distance between tracked fingers and the thumb to the grasping force required for lifting a virtual object with a given weight. The second method maps the detected intensity of finger pinch during grasping gestures to the lifting force. In an experiment described in this paper we investigated the potential of the proposed methods for the discrimination of heaviness of virtual objects by finding the just noticeable difference (JND) to calculate the Weber fraction. Furthermore, the workload that users experienced using these methods was measured to gain more insight into their usefulness as interaction technique. At a hit ratio of 0.75, the determined Weber fraction using the finger distance based method was 16.25% and using the pinch based method was 15.48%, which corresponds to values found in related work. There was no significant effect of method on the difference threshold measured and the workload experienced, however the user preference was higher for the pinch based method. The results demonstrate the capability of the proposed methods for the perception of heaviness in IVEs and therefore represent a simple alternative to haptics based methods. |
Rolf Westerteiger, Gregory Streletz, Oliver Kreylos, Geoffrey A. Gebbie, Howard J. Spero, Louise H. Kellogg, Andreas Gerndt, Bernd Hamann, Hans Hagen Exploration of Time-dependent Paleoceanographic Flow Data in Virtual Reality (Inproceedings) In: GeoViz Worshop, Hamburg, Germany, March 6-8, 2013, 2013, (Extended Abstract). @inproceedings{WEST13, |
Philipp M. Fischer, Daniel Lüdtke, Volker Schaus, Andreas Gerndt A Formal Method for Early Spacecraft Design Verification (Inproceedings) In: IEEE Aerospace Conference, Big Sky, MT, USA, March 2-9, 2013, IEEE, 2013. @inproceedings{FISC13,In the early design phase of a spacecraft, various aspects of the system under development are described and modeled using parameters such as masses, power consumption or data rates. In particular power and data parameters are special since their values can change depending on the spacecrafts operational mode. These mode-dependent parameters can be easily verified to static requirements like a maximum data rate. Such quick verifications allow the engineers to check the design after every change they apply. In contrast, requirements concerning the mission lifetime such as the amount of downlinked data during the whole mission, demands a more complex procedure. We propose an executable model together with a simulation framework to evaluate complex mission scenarios. In conjunction with a formalized specification of mission requirements it allows a quick verification by means of formal methods. |
2012 |
Fang Chen, Markus Flatken, Achim Basermann, Andreas Gerndt, James Hetherington, Timm Krüger, Gregor Matura, Rupert Nash In: Preparing Applications for Exascale Through Co-design, SC 2012 Workshop, Salt Lake City, UT, USA, November 16, 2012, IEEE, 2012. @inproceedings{CHEN12,Today's fluid simulations deal with complex geometries and numerical data on an extreme scale. As computation approaches the exascale, it will no longer be possible to write and store the full-sized data set. In situ data analysis and scientific visualisation provide feasible solutions to the analysis of complex large scaled CFD simulations. To bring pre- and postprocessing to the exascale we must consider modifications to data structure and memory layout, and address latency and error resiliency. In this respect, a particular challenge is the exascale data processing for the sparse geometry lattice-Boltzmann code HemeLB, intended for hemodynamic simulations. In this paper, we assess the needs and challenges of HemeLB users and sketch a co-design infrastructure and system architecture for pre- and post-processing the simulation data. To enable in situ data visualisation and analysis during a running simulation, post-processing needs to work on a reduced subset of the original data. Particular choices of data structure and visualisation techniques need to be co-designed with the application scientists in order to achieve efficient and interactive data processing and analysis. In this work, we focus on the hierarchical data structure and suitable visualisation techniques which provide possible solutions to interactive in situ data processing at exascale. Architectural challenges and road-maps will be presented as the major focus of this paper. We sketch a software architecture which integrates pre- and post-processing techniques that can provide in situ analysis and ultimately computational steering to HemeLB. |
Volker Schaus, Philipp M. Fischer, Dominik Quantius, Andreas Gerndt Automated Sensitivity Analysis in Early Space Mission Design (Inproceedings) In: 5th International Workshop on Systems & Concurrent Engineering for Space Applications (SECESA 2012), Lisabon, Portugal, October 17-19, 2012, ESA 2012. @inproceedings{SCHA12,Concurrent Engineering in space mission design features several hundred design parameters provided by more than a dozen domain experts. The quality of the design strongly depends on the individual expertise of the people in the team, their experience and collaboration. As part of the design team, a moderator guides the study. In order to bring the study forward, he must have a good overview, ask the design team the right questions and trigger the next actions while keeping the study objectives in mind. The system design evolves quickly; major changes to the baseline are frequent and have to be taken into account. In this dynamic process it is desirable to quickly identify all the effects of a design change throughout the whole system. The paper presents an automated sensitivity analysis approach to evaluate the current design. This analysis can be used directly during the study to identify design drivers and relationships between individual design parameters. The sensitivity data helps to focus on the right components or subsystems and to guide the design process in a well-founded way. The paper explains the implementation of the automated sensitivity analysis algorithm based on a shared system data model, which is capable of holding all the necessary parameters and equations. The implementation in the DLR software Virtual Satellite and the interaction with the user is discussed. A comprehensible example of laying out the fuel tank of a spacecraft shows how the sensitivity analysis can be interpreted and how it can help to improve the design quality. The same example is later used to point out the local relevance of the sensitivity results. In this case, one design parameter is successively changed by three orders of magnitude. Looking at the sensitivity values in each step, the impact of one parameter is completely shifted to another parameter. This effect is the result of the associated dimension of the design parameters. A second implementation calculating dimensionless sensitivity coefficients is then used to create quantifiable results that allow for comparison between the design parameters. In the concluding section on future work we discuss how the automated sensitivity analysis can be used during an actual Concurrent Engineering study with several hundred design parameters. |
Johannes Hummel, Robin Wolff, Janki Dodiya, Andreas Gerndt, Torsten Kuhlen Towards Interacting with Force-Sensitive Thin Deformable Virtual Objects (Inproceedings) In: Ronan Boulic, Carolina Cruz-Neira, Kiyoshi Kiyokawa, David Roberts (Ed.): Joint Virtual Reality Conference (JVRC), Madrid, Spain, October 16-19, 2012, pp. 17–20, Eurographics Association, 2012, (Short Paper). @inproceedings{HUMM12c,The selection of the right input devices for 3D interaction methods is important for a successful VR system. While natural direct interaction is often preferred, research has shown that indirect interaction can be beneficial. This paper focuses on an immersive simulation and training environment, in which one sub-task it is to carefully grasp and move a force-sensitive thin deformable foil without damaging it. In order to ensure transfer of training it was necessary to inform the user of the fact of gentle grasping and moving the foil. We explore the potential of three simple and light-weight interaction methods that each map interaction to a virtual hand in a distinct way. We used a standard tracked joystick with an indirect mapping, a standard finger tracking device with direct mapping based on finger position, and a novel enhanced finger tracking device, which additionally allowed pinch force input. The results of our summative user study show that the task performance did not show a significant difference among the three interaction methods. The simple position based mapping using finger tracking was most preferred, although the enhanced finger tracking device with direct force input offered the most natural interaction mapping. Our findings show that both a direct and indirect input method have potential to interact with force-sensitive thin deformable objects, while the direct method is preferred. |
Rolf Westerteiger, Tracy Compton, Tony Bernadin, Eric Cowgill, Klaus Gwinner, Bernd Hamann, Andreas Gerndt, Hans Hagen Interactive Retro-Deformation of Terrain for Reconstructing 3D Fault Displacements (Journal Article) In: IEEE Transaction on Visualization and Computer Graphics (TVCG), vol. 18, iss. 12, pp. 2208–2215, 2012. @article{WEST12c,Planetary topography is the result of complex interactions between geological processes, of which faulting is a prominent component. Surface-rupturing earthquakes cut and move landforms which develop across active faults, producing characteristic surface displacements across the fault. Geometric models of faults and their associated surface displacements are commonly applied to reconstruct these offsets to enable interpretation of the observed topography. However, current 2D techniques are limited in their capability to convey both the three-dimensional kinematics of faulting and the incremental sequence of events required by a given reconstruction. Here we present a real-time system for interactive retro-deformation of faulted topography to enable reconstruction of fault displacement within a high-resolution (sub 1m/pixel) 3D terrain visualization. We employ geometry shaders on the GPU to intersect the surface mesh with fault-segments interactively specified by the user and transform the resulting surface blocks in realtime according to a kinematic model of fault motion. Our method facilitates a human-in-the-loop approach to reconstruction of fault displacements by providing instant visual feedback while exploring the parameter space. Thus, scientists can evaluate the validity of traditional point-to-point reconstructions by visually examining a smooth interpolation of the displacement in 3D. We show the efficacy of our approach by using it to reconstruct segments of the San Andreas fault, California as well as a graben structure in the Noctis Labyrinthus region on Mars. |
Rolf Westerteiger, Andreas Gerndt, Bernd Hamann Spherical Terrain Rendering Using the Hierarchical HEALPix Grid (Inproceedings) In: Visualization of Large and Unstructured Data Sets (VLUDS), IRTG 1131 Workshop, Kaiserslautern, Germany, June 10-11, 2011, Dagstuhl Publishing, October 10, 2012. @inproceedings{WEST12b,We present an interactive spherical terrain rendering system employing a hierarchical subdivision of the HEALPix coordinate system using quadtrees. Compared to other parameterizations, the scheme avoids singularities and allows for efficient fusion of mixed-resolution digital elevation models and imagery. A Level-of-Detail heuristic is used to guarantee both high performance and visual fidelity. Unified treatment of DEM and imagery data is achieved by performing the HEALPix projection within a GPU shader. The system is applied to the exploration of Mars, using both MOLA (NASA) and HRSC (German Aerospace Center) data sets. |
Hao Zhang, Andreas Gerndt, Bo Liu Static Simulation Scheduling for the Validation of Space System Requirement Decomposition (Inproceedings) In: 63rd International Astronautical Congress (IAC), Naples, Italy, October 1-5, 2012, International Astronautical Ferderation (IAF), 2012. @inproceedings{ZHAN12b,One important issue in space engineering is to ensure that all system requirements are always fulfilled throughout the whole development process. To perform this task, various validation technologies have been developed. In this paper, document-based reviews and Modelling & Simulation technology are illustrated as two of such technology examples. Their disadvantages are analysed as well. The fundamental challenge for them is to carry out a consistent validation throughout the whole development process. To resolve this problem, a static simulation scheduling approach is proposed in this paper. This scheduling approach is based on a hierarchical decomposition model of a space system. The model is constructed following the principles of Model-Based Systems Engineering (MBSE). It maps all requirements to state variables and defines states as well as relations along three red lines of a space mission: inter-subsystems, internal subsystems, and space mission lifecycle. In the static simulation scheduling approach, the validation is driven just by the states of state variables and their relations. But, the specific validation process is dependent on current states of the processed variable. The scheduling approach is illustrated and demonstrated in this paper. It facilitates a preliminary validation analysis throughout the whole development lifecycle that would otherwise be cost intensive or even be impossible. Furthermore, after each system refinement, the validation analysis can be performed again automatically. Our work is based on the ``Virtual Satellite'', which is being developed by German Aerospace Center (DLR). We are pursuing the possibility to implement specification, analysis, design, and operation of space missions in a unified framework. |
Philipp M. Fischer, Daniel Lüdtke, Volker Schaus, Olaf Maibaum, Andreas Gerndt Formal Verification in Early Mission Planning (Inproceedings) In: Workshp on Simulation and EGSE Facilities for Space Programmes (SESP), Noordwijk, The Netherlands, September 25-27, 2012, 2012. @inproceedings{FISC12a,Spacecraft are complex systems. Changing one of its design parameter can have implications on the overall design and might become a crucial factor to mission success. In the early phases of spacecraft design, parameters as well as the mission goals are likely to change. These changes have to be applied carefully and need to be analyzed in respect to the whole system and the intended mission. The software Virtual Satellite supports this analysis by using an abstract model where the engineers can enter design data of their components. It allows describing operational phases of the spacecraft by defining modes such as Recharge or Science. These operational modes can be referenced by parameters to define individual values for them. Together with their respective mode durations, it can be determined for example how much energy is consumed in a specific mode or how much is produced. But this does not consider the influence of the parameter with respect to the overall mission goals. For example having a mission life time of 20 years and a spacecraft which spends too much of that time to maintain its power state, it remains unclear if the remaining time is long enough to gather enough scientific data as demanded by the mission requirements. This paper shows an approach to such problems based on formal verification. The data of the early phase model is used to create a state model of the spacecraft. Both, the model and the formalized requirements will be given to a model checker that automatically verifies on formal basis that the spacecraft complies with its specification. This method enables engineers to quickly check the design with respect to the mission requirements once they applied changes to it or to the requirements. |
Rolf Westerteiger, Fang Chen, Andreas Gerndt, Bernd Hamann, Hans Hagen Remote GPU-Accelerated Online Pre-processing of Raster Maps for Terrain Rendering (Inproceedings) In: Christian Geiger, Jens Herder, Tom Vierjahn (Ed.): Virtuelle und Erweiterte Realität - 9. Workshop der GI-Fachgruppe VR/AR, Düsseldorf, Germany, September 19-20, 2012, pp. 143–154, Shaker Verlag, 2012. @inproceedings{WEST12a,We present a distributed architecture for accelerated pre-processing of remote sensing data for immediate terrain visualization. Interactive 3D visualization approaches for large terrain datasets employ level of detail techniques that require a multi-resolution data representation. The high computational cost of constructing these representations is often not viewed as a major drawback, as it is considered an o-line pre-processing step. This prevents the application of existing methods in the case of changing data, which is becoming increasingly important for a multitude of applications where datasets are being generated, transmitted and must be visualized immediately, such as in disaster management. Our system uses graphics processing units (GPUs) to accelerate the process of generating a multi-resolution representation, achieving sucient performance to enable on-line visualization on a front-end workstation communicating with a back-end cluster of machines equipped with GPUs. As a reference data structure, we use a quad tree decomposition of the so-called HEALPix sphere parameterization, which is well-suited for spherical terrain rendering. Our system correctly handles overlapping and unregistered mixed-resolution datasets. We demonstrate the ecacy of our approach by applying it to the surface of Mars using both the NASA Mars Orbiter Laser Altimeter and the ESA Mars Express High Resolution Stereo Camera datasets. |
Christian Wagner, Markus Flatken, Fang Chen, Andreas Gerndt, Charles Hansen, Hans Hagen Interactive Hybrid Remote Rendering for Multi-pipe Powerwall Systems (Inproceedings) In: Christian Geiger, Jens Herder, Tom Vierjahn (Ed.): Virtuelle und Erweiterte Realität - 9. Workshop der GI-Fachgruppe VR/AR, Düsseldorf, Germany, September 19-20, 2012, pp. 155–166, Shaker Verlag, 2012. @inproceedings{WAGN12b,To understand complex physical phenomena, interactive and explorative post-processing of their numerical simulations has proven to be a feasible solution. This task can be enhanced by using virtual environments (VR) with high immersion and natural interaction techniques. While interactive VR systems provide high frame rates with low latencies, the hardware resources driving their displays are often insuffcient to visualize large scale simulation results. Local memory capacities are easily exceeded by dataset sizes and render performance is insuffcient to achieve the required frame rates. Parallel remote rendering techniques, on the other hand, support huge distributed memories and massive render performance. However these techniques have long interaction delays and the update rate is bandwidth limited. In this paper, we introduce a software architecture that oers a hybrid rendering approach for interactive visualization of large scale simulation data using a multi-pipe powerwall system. Local and remote images are generated on a frontend and parallel backend application with different frame rates. An image re-adjustment technique is used to deal with delayed remote images and hide latencies. |
Hao Zhang, Andreas Gerndt, Bo Liu 3D State Decomposition Modeling Method for MBSE in Space Engineering (Inproceedings) In: AIAA SPACE 2012 Conference & Exposition, Pasadena, CA, USA, September 11-13, 2012, AIAA Inc., 2012. @inproceedings{ZHAN12a,The increasing number of space missions and the market environment make it mandatory that the design process and design models have to be reused in future space missions. As a solution to such a reuse problem, Model-Based Systems Engineering (MBSE) is highly recommended. Since constructing a model is the first step to reach MBSE, a 3D state decomposition modeling method is proposed in this paper. Starting from Technical Requirements (TRs), the method maps them to state variables and defines states as well as relations along three red lines of space engineering: internal subsystem, inter-subsystems, and space mission lifecycle. Eventually, it yields decomposition of a space system into a hierarchical three-dimensional model of states. Relying on the Eclipse Modeling Framework (EMF), the model can be described and stored in a standardized format, which allows the reuse of once defined models in subsequent space missions. This study leads to a novel MBSE solution to implement specification, analysis, design, and operation of space mission systems in a unified framework. |
Meenakshi Deshmukh, Volker Schaus, Philipp M. Fischer, Dominik Quantius, Volker Maiwald, Andreas Gerndt Decision Support Tool for Concurrent Engineering in Space Mission Design (Inproceedings) In: Josip Stjepandic, Georg Rock, Cees Bil (Ed.): 19th ISPE International Conference on Concurrent Engineering (CE2012), Trier, Germany, September 3-7, 2012, pp. 497–508, Springer Verlag, London, 2012. @inproceedings{DESH12,The concurrent engineering (CE) approach has been successfully applied to the early design phase of space missions. During CE sessions, a software support is needed to allow multidisciplinary design data exchange. At the moment, a spreadsheet-based solution enhanced with macros is used at the German Aerospace Center (DLR) to create a system model of a space mission during the early design phase. Now there is an increasing demand to take advantage of this system model and provide data analysis features which improve the decision making during CE sessions. Since the current approach is limited for such analysis, DLR has started developing a new tool called Virtual Satellite. It offers extended software support required by the Concurrent Engineering Facility of DLR in Bremen. On top of the previous spreadsheet functionalities, it provides means for online data analysis and system modeling. The results of these data analyses are presented to the discipline experts using different views which help in performing an early design optimization. In this paper, the impact of these views on the decision making during the AEGIS space mission study is presented as a proof of concept. |
Johannes Hummel, Robin Wolff, Tobias Stein, Andreas Gerndt, Torsten Kuhlen An Evaluation of Open Source Physics Engines for Use in Virtual Reality Assembly Simulations (Inproceedings) In: George Bebis, Richard Boyle, Bahram Parvin, Darko Koracin, Charless Fowlkes, Sen Wang, Min-Hyung Choi, Stephan Mantler, Jürgen Schulze, Daniel Acevedo, Klaus Mueller, Michael Papka (Ed.): 8th International Symposium on Visual Computing (ISVC), Rethymnon, Crete, July 16-18, 2012, pp. 346–357, Springer, 2012. @inproceedings{HUMM12b,We present a comparison of five freely available physics engines with specific focus on robotic assembly simulation in virtual reality (VR) environments. The aim was to evaluate the engines with generic settings and minimum parameter tweaking. Our benchmarks consider the minimum collision detection time for a large number of objects, restitution characteristics, as well as constraint reliability and body inter-penetration. A further benchmark tests the simulation of a screw and nut mechanism made of rigid-bodies only, without any analytic approximation. Our results show large deviations across the tested engines and reveal benefits and disadvantages that help in selecting the appropriate physics engine for assembly simulations in VR. |
Daniel Lüdtke, Jean-Sébastien Ardaens, Meenakshi Deshmukh, Rosa Paris Lopez, Andy Braukhane, Ivanka Pelivan, Stephan Theil, Andreas Gerndt Collaborative Development and Cataloging of Simulation and Calculation Models for Space Systems (Inproceedings) In: 21th IEEE International Workshops on Enabling Technologies: Infrastructure for Collaborative Enterprises (WETICE), Toulouse, France, June 25-27, 2012, pp. 244–249, IEEE Computer Society Press, 2012. @inproceedings{LUED12b,The application of modeling and simulation in the design, development and validation process of complex systems has significantly increased in the last decades. Creating high quality models is a time-consuming task. Particularly, if models should be shared and reused in future projects. In this paper, results of the project Simulation Model Library (SimMoLib) are presented that address the issues concerning the preservation of knowledge that lies within simulation and calculation models. SimMoLib provides modeling guidelines and best practices to help the developer to prepare models that can be reused in other contexts. Validation and verification of these models is covered by proposing a set of guidelines and two test frameworks as well as by promoting peer reviews of models by other experts. To archive, catalogue, and distribute models, a software framework is under development which supports the creation, management, retrieval, and utilization of models. In order to allow the collaborative editing of calculation and simulation models a simplified version control mechanism is established. SimMoLib is currently targeted to support the development of space systems. In the future it will be opened to other domains. |
Daniel Lüdtke, Sinan Mece, Meenakshi Deshmukh, Michael Bock, Andreas Schreiber, Andreas Gerndt A Framework to Model Metadata for Knowledge Management Tools (Inproceedings) In: 4th International Conference on Knowledge Management for Space Missions, Toulouse Space Show 2012, Toulouse, France, June 25-28, 2012, 2012. @inproceedings{LUED12a,In recent years many kinds of knowledge management tools are being developed. Most of them have in common that they provide an interface to acquire artifacts along with a certain set of metadata. In this paper, a new framework is presented to model metadata for knowledge management tools and to generate metadata-related program code from this model for different components of the target tool. These components include graphical user interfaces for desktop applications, data base schemes, and metadata-related web client code. Finally, two applications from the knowledge management domain are presented, where this framework is successfully integrated to reduce development time substantially. |
Christian Wagner, Andreas Gerndt, Charles Hansen, Hans Hagen Interactive In-Situ Online Monitoring of Large Scale CFD Simulations with Cut-Planes (Inproceedings) In: IEEE Virtual Reality Workshop, Immersive Visualization Revisited: Challenges and Opportunities, Orange County, CA, USA, March 4, 2012, 2012, (Short Paper). @inproceedings{WAGN12a,Online monitoring of running simulations is gaining importance in order to inspect or validate ongoing calculations. With increasing high performance computing capacities copying raw data to a dedicated visualization cluster becomes too expensive. Therefore, insitu approaches using same compute resources are required. Cut-planes became a common visualization tool in order to analyze complex three-dimensional scalar fields. Within this method, interesting regions are sliced with one or more planes on which the intersected scalar field is represented. To explore the whole dataset, cut-planes need to be moved around interactively which requires high update rates. Typical cut-plane algorithms process all cells crossed by the plane resulting in high extraction times and output sizes. In order to provide guaranteed response times we use a progressive sampling scheme instead. By sampling the cut-plane at distinct positions the presented methods are independent of the cell count in the affected region. In this paper we present a solution combining interactive exploration inside a virtual reality environment and in-situ cut-plane extraction supporting required interactive update rates. |
Rolf Westerteiger, Andreas Gerndt, Bernd Hamann, Hans Hagen Spatial Analysis of Terrain in Virtual Reality (Inproceedings) In: IEEE Virtual Reality Workshop, Immersive Visualization Revisited: Challenges and Opportunities, Orange County, CA, USA, March 4, 2012, 2012, (Short Paper). @inproceedings{WEST12,We extend an existing virtual reality terrain visualization framework to support spatial analysis tasks for geoscientific purposes. We demonstrate both interactive measurement of height profiles as well as volume measurement within polygonal footprints. In this application, virtual reality technology enables superior perception of the placement of these lines with respect to terrain features. |
Philipp M. Fischer, Robin Wolff, Andreas Gerndt Collaborative Satellite Configuration Supported by Interactive Visualization (Inproceedings) In: IEEE Aerospace Conference, Big Sky, MT, USA, March 3-10, 2012, IEEE, 2012. @inproceedings{FISC12b,Planning a spacecraft requires the expert knowledge from diverse disciplines, such as propulsion or structure. Reliable communication between the experts is crucial, as the individual requirements of a satellite's various subsystems heavily depend on each other. Today, early mission design sessions are often held in specially designed rooms, so-called concurrent engineering facilities. Here, the experts come together and directly discuss with each other in a shared place, enabling them to find a common ground much quicker. Nevertheless, in certain aspects it remains difficult for the experts to share and describe their knowledge within the team. In particular for configuration purposes it is a hurdle to verbally discuss positions and orientations of different parts. We propose a new approach of using shared interactive visualization for the configuration task, which enables every engineer to individually place parts and to alter it in case of discrepancies. |
Doreen Seider, Philipp Fischer, Markus Litz, Andreas Schreiber, Andreas Gerndt Open Source Software Framework for Applications in Aeronautics and Space (Inproceedings) In: IEEE Aerospace Conference, Big Sky, MT, USA, March 3-10, 2012, IEEE, 2012. @inproceedings{SEID12,The DLR developed the open source software framework RCE to support the collaborative and distributed work in the shipyard industry. From a technology side of view a software from the shipbuilding field has many requirements in common with aerospace software projects. Accordingly, RCE has become the basis for further projects within the DLR. Over the last years of usage a subset of frequently used software components could be derived and are provided by the RCE framework. In particular, the workflow engine, allowing the integration of different domain-specific tools from local and remote locations into one overall calculation has become important for various projects. We present RCE and show how its software components are reused in two aerospace applications. |
2011 |
Robin Wolff, Carsten Preusche, Andreas Gerndt A Modular Architecture for an Interactive Real-Time Simulation and Training Environment for Satellite On-Orbit Servicing (Inproceedings) In: 15th IEEE/ACM International Symposium on Distributed Simulation and Real Time Applications (DS-RT), Salford, MediaCity, UK, September 4-7, 2011, pp. 72–80, 2011. @inproceedings{WOLF11,This paper outlines the development of a real-time interactive application for the analysis, training and programming of on-orbit servicing tasks within a virtual reality environment. The main challenges put on the system are the real-time simulation of the realistic dynamic and kinematic behavior of satellite components and additionally integrate interaction through a bimanual haptic interface, as well as enable tele-operation of a robot. We give an overview of the application, describe the real-time challenges and outline our approach and proposed system structure. |
Volker Schaus, Karsten Großekatthöfer, Daniel Lüdtke, Andreas Gerndt Collaborative Development of a Space System Simulation Model (Inproceedings) In: 20th IEEE International Workshops on Enabling Technologies: Infrastructure for Collaborative Enterprises (WETICE 2011), Paris, France, June 27-29, 2011, pp. 164–169, IEEE Computer Society, 2011. @inproceedings{SCHA11,Modeling and simulation is a powerful method to evaluate the design of a space system. Simulation models represent valuable knowledge and require considerable time and effort for their development. Means for reuse should be taken into account from the beginning of model creation. This paper presents a collaborative model development process, which creates prerequisite information for successful reuse of simulation models. It introduces a knowledge model and proposes reviewed documentation at each step in the process. These pieces of documentation enable successive reuse at different levels. The modeling process was evaluated by creating a system simulation of the OOV-TET-1 satellite including three satellite subsystems, dynamics, kinematics, and space environment. Furthermore, the organization of models and their documentation artifacts is crucial in order to search, find, and reuse models across project partners and across projects. The paper suggests a flexible model database that suits the special requirements of typical space projects and large research organizations. |
Philipp M. Fischer, Volker Schaus, Andreas Gerndt Design Model Data Exchange Between Concurrent Engineering Facilities by Means of Model Transformation (Inproceedings) In: 13th NASA-ESA Workshop on Product Data Exchange, Cypress, CA, USA, May 11-12, 2011, NASA/ESA 2011. @inproceedings{FISC11,The German Aerospace Center (DLR) is developing the software Virtual Satellite for use in their Concurrent Engineering Facility. Throughout the design process of a spacecraft the software supports engineers to store and manage the data and results of their engineering sessions. The European Cooperation for Space Standardization (ECSS) is promoting a new technical memorandum for model based data exchange across the facilities. In order to enable data exchange from Virtual Satellite's own model representation to the ECSS specification, a transformation based on a triple-graph grammar has been applied. This approach allows engineers to import and export design information from the ECSS model. In addition, the grammar allows for synchronization of two instantiated models. |
Olaf Maibaum, Thomas Terzibaschian, Christian Raschke, Andreas Gerndt Software Reuse of the BIRD ACS for the TET Satellite Bus (Inproceedings) In: Rainer Sandau, Hans-Peter Röser, Arnoldo Valenzuela (Ed.): 8th IAA Symposium on Small Satellites for Earth Observation, Berlin, Germany, April 4-8, 2011, pp. 409–412, Wissenschaft und Technik Verlag Berlin, 2011. @inproceedings{MAIB11,The paper present the software reuse case of the BIRD ACS as TET-1 AOCS. The reuse was succesful and the paper present the necessary adaptions and the software design concepts for the software reuse case. |
2010 |
Christian Wagner, Markus Flatken, Michael Meinel, Andreas Gerndt, Hans Hagen FSSteering: A Distributed Framework for Computational Steering in a Script-based CFD Simulation Environment (Inproceedings) In: Werner Benger, Andreas Gerndt, Simon Su, Wolfram Schoor, Michael Koppitz, Wolfgang Kapferer, Hans-Peter Bischof, Massimo Di Perro (Ed.): 6th High-End Visualization Workshop, Obergurgl, Austria, December 8-12, 2010, pp. 9–20, Lehmanns Media, Berlin, Germany, 2010. @inproceedings{WAGN10,In order to get insight into interesting flow phenomena, the traditional work-flow of computational fluid dynamics (CFD) consists of setting up and computing the flow field followed by a consecutive post-processing analysis. Only after this analysis one can identify parameters that may have been set wrongly in a configuration stage. Once these parameters are corrected, another time-consuming loop has to be started. To identify inadequate parameter settings already during the simulation run, online monitoring concepts were introduced. Combined with computational steering methods, parameter values can additionally be adjusted which eventually reduces the number of required iterations to yield satisfactory results. At the German Aerospace Center, a comprehensive framework called FlowSimulator has been developed to offer a generic Python-based interface for the management of CFD simulations. It can easily be enhanced by add-ons. One of these extensions is FSSteering which is described in this paper in more detail. As a computational steering environment, FSSteering provides functionalities essential for interactive visualization and explorative analysis. Besides existing computational steering environments and frameworks, a user-centred and domain-specific view is proposed. Existing functionality can be reused without rewriting simulation code to enable for effective steering in CFD. To be more efficient, components of the architecture are distributed across different resources. Whereas the CFD simulation typically runs on a parallel supercomputer, the visualization is carried out on a high-performance virtual reality system which allows interactive data exploration. The post-processing in between can be performed on the supercomputer or on a separate parallelization cluster. But it is also possible to switch between different existing post-processing toolkits. This is just possible because of the very flexible configuration management of the distributed steering framework. We will demonstrate the steering capabilities and the system flexibility by two current research examples. An outlook for future steps concludes this paper. |
Joachim Steinmetz, Olaf Maibaum, Andreas Gerndt, Stephan Borgert, Max Mühlhäuser Symbolic Abstraction of System Requirements (Inproceedings) In: Systems Engineering Infrastructure Conference (SEISCONF 2010), Ottobrunn, Germany, October 19, 2010, 2010. @inproceedings{STEI10,Because aerospace systems become more and more complex, the pile of documents specifying the requirements for such systems grows continuously. It is obvious that it is not enough just to produce more documents. The expressiveness of system requirements has to be considered as well. However, the ambiguity of natural language generally used to define requirements impedes a manageable growth of system complexities. Therefore, new approaches of abstraction and formalization are needed. In this paper, we describe a semi-automatic implementation of symbolic abstraction by using methods of natural language processing and temporal logic. A graphical presentation of grammatical relations supports the comprehensibility of symbolic abstraction whereas methods defined by the Linear Temporal Logic (LTL) are incorporated to specify the temporal order of requirements. We demonstrate our approach by using exemplary requirements for the ExoMars mission. |
Volker Schaus, Philipp M. Fischer, Daniel Lüdtke, Andy Braukhane, Oliver Romberg, Andreas Gerndt Concurrent Engineering Software Development at German Aerospace Center - Status and Outlook (Inproceedings) In: 4th International Workshop on Systems & Concurrent Engineering for Space Applications (SECESA 2010), Lausanne, Switzerland, October 13-15, 2010, ESA 2010. @inproceedings{SCHA10, |
Holger Schumann, Heinrich Wendel, Andy Braukhane, Axel Berres, Andreas Gerndt, Andreas Schreiber Concurrent Systems Engineering in Aerospace: From Excel-based to Model Driven Design (Inproceedings) In: 8th Conference on Systems Engineering Research (CSER), Hoboken, NJ, March 17-19, 2010, USC/Stevens 2010. @inproceedings{SCHU10,Concurrent engineering is a modern and very effective discipline of systems engineering. In the European space domain, the European Space Agency is the pioneer in this area and has performed early design studies for 10 years now. The Integrated Design Model (IDM) is still the state of the art in concurrent engineering software environments. It is based on Microsoft Excel, which induces several benefits and drawbacks related to concurrent engineering. The German Aerospace Center has used the IDM for several design studies and has identified two promising approaches to further increase the effectiveness of the concurrent engineering software environment by using modern model driven software technologies. Both concepts were implemented, and in this paper they are compared to each other and opposed to the IDM. |
2009 |
Axel Berres, Marco Berlin, Andreas Kotz, Thomas Terzibaschian, Andreas Gerndt A Generic Simulink Model Template for Simulation of Small Satellites (Inproceedings) In: Rainer Sandau, Hans-Peter Röser, Arnoldo Valenzuela (Ed.): 7th IAA Symposium on Small Satellites for Earth Observation, Berlin, Germany, May 4-8, 2009, pp. 247–250, Wissenschaft und Technik Verlag, 2009. @inproceedings{BERR09,This paper presents a template architecture for a straightforward specification of small satellite missions by means of a domain specific language. Furthermore, the process to transform this model to a platform-dependent, executable simulation is depicted. As a first prototype environment, Simulink has been selected. The design adaptation during the developing process is illustrated using the power system of the OOV-TET satellite. |
Andreas Gerndt, Rolf Hempel, Edmund Kügeler, Torsten Kuhlen Post-Processing Pipeline Optimization for Interactive Exploration of Multi-Block Turbine Propulsion Simulation Datasets (Inproceedings) In: Werner Berger, Wolfram Schoor, Simon Su, Andreas Gerndt (Ed.): 5th High-End Visualization Workshop, Baton Rouge, LA, USA, March 18-21, 2009, pp. 62–78, Lehmanns Media, 2009. @inproceedings{GERN09b,With the increasing power of current supercomputers, flow field simulations become larger and larger. Those datasets are too large to fit into the main memory of a visualization workstation and too large to be processed in a reasonable time on a stand-alone system. Distributed post-processing can eliminate dominant bottlenecks. With parallel computer systems, the post-processing can show a considerable speed-up. In this paper, we address issues to optimize several phases of the pipeline-based post-processing for interactive exploration of time-dependent, multi-block flow field simulation datasets. Firstly, we present the distributed post-processing framework, its approach to manage multi-block data structures, and how nested parallelization can improve the overall runtime. Scalability, balancing, and efficiency of algorithms optimized for unsteady multi-block datasets are presented. However, complex feature extractions are still time-consuming. For interactive exploration approaches in virtual environments, further strategies like streaming of intermediate data from post-processing backend to visualization frontend are needed. If the extracted visualization objects are too complex to be rendered with interactive frame rates, view-dependent multi-resolution techniques can help to present essential details without losing real-time rendering. To improve the interactivity, several integrated strategies are evaluated. Run-time measurements prove the efficiency of the approaches. An outlook for future steps concludes this paper. |
Andreas Gerndt, Robert Miller, Simon Su, Ehab Meselhe, Carolina Cruz-Neira Interactive Exploration of Coastal Restoration Modeling in Virtual Environments (Inproceedings) In: Ian E. McDowall, Margaret Dolinsky (Ed.): 21st Annual Symposium on Electronic Imaging, Conference on the Engineering Reality of Virtual Reality, San Jose, CA, USA, January 18-22, 2009, IS&T/SPIE, 2009. @inproceedings{GERN09a, |
Simon Su, Carolina Cruz-Neira, Emad Habib, Andreas Gerndt Virtual Hydrology Observatory: An Immersive Visualization of Hydrology Modeling (Inproceedings) In: Ian E. McDowall, Margaret Dolinsky (Ed.): 21st Annual Symposium on Electronic Imaging, Conference on the Engineering Reality of Virtual Reality, San Jose, CA, USA, January 18-22, 2009, IS&T/SPIE, 2009. @inproceedings{SU09,The Virtual Hydrology Observatory will provide students with the ability to observe the integrated hydrology simulation with an instructional interface by using a desktop based or immersive virtual reality setup. It is the goal of the virtual hydrology observatory application to facilitate the introduction of field experience and observational skills into hydrology courses through innovative virtual techniques that mimic activities during actual field visits. The simulation part of the application is developed from the integrated atmospheric forecast model: Weather Research and Forecasting (WRF), and the hydrology model: Gridded Surface/Subsurface Hydrologic Analysis (GSSHA). Both the output from WRF and GSSHA models are then used to generate the final visualization components of the Virtual Hydrology Observatory. The various visualization data processing techniques provided by VTK are 2D Delaunay triangulation and data optimization. Once all the visualization components are generated, they are integrated into the simulation data using VRFlowVis and VR Juggler software toolkit. VR Juggler is used primarily to provide the Virtual Hydrology Observatory application with fully immersive and real time 3D interaction experience; while VRFlowVis provides the integration framework for the hydrologic simulation data, graphical objects and user interaction. A six-sided CAVE(TM)-like system is used to run the Virtual Hydrology Observatory to provide the students with a fully immersive experience. |
2008 |
Holger Schumann, Andy Braukhane, Andreas Gerndt, Jan Thimo Grundmann, Rolf Hempel, Bobby Kazeminejad, Oliver Romberg, Martin Sippel Overview of the New Concurrent Engineering Facility at DLR (Inproceedings) In: 3rd International Workshop on System & Concurrent Engineering for Space Applications (SECESA), Rome, Italy, October 15-17, 2008, ESA 2008. @inproceedings{SCHU08,In October 2008, the German Aerospace Center (DLR) inaugurated a new Concurrent Engineering Facility (CEF) in Bremen which is used mainly for design studies at the new DLR Institute of Space Systems. The CEF consists of a main conferencing room for twelve disciplines and up to seven experts or guests, and two smaller rooms for splinter meetings. So far, several one week studies have been carried out, two were dedicated to the DLR compact satellite program. As it is planned to use the CEF not only for phase 0/A studies but also during later phases of the system development cycle, the Concurrent Engineering (CE) process as well as the technical infrastructure have to meet additional requirements, related to dynamic simulations and remote collaboration. Software projects have been initiated at DLR with the objective to create a next-generation CEF infrastructure that will meet those requirements. This paper gives an overview of the facility infrastructure and the ongoing CEF-related software projects at DLR. The AsteroidFinder project served as a first test case for the CE process. Details of first CE sessions carried out for this project and lessons learned are presented. Finally, an outlook on planned future enhancements is given. |
Andreas Gerndt, Malcolm Hutson, Paul Fung, Carolina Cruz-Neira Fire in a Storage: From Simulation to Virtual Environments (Inproceedings) In: 5th INTUITION International Conference, Turin, Italy, Oct. 6-8, 2008, 2008. @inproceedings{Gerndt2008b, |
Andreas Gerndt, Torsten Kuhlen, Carolina Cruz-Neira Interactive Tracking of Three-dimensional Critical Points in Unsteady, Large-scale CFD Datasets (Inproceedings) In: Hamid R. Arabnia, Leonidas Deligiannidis (Ed.): The 2008 International Conference on Computer Graphics and Virtual Reality (CGVR'08), Las Vegas, NV, USA, July 14-17, 2008, pp. 22–28, CSREA Press, 2008. @inproceedings{Gerndt2008a, |
2007 |
Thomas Düssel, Herwig Zilken, Wolfgang Frings, Thomas Eickermann, Andreas Gerndt, Marc Wolter, Torsten Kuhlen Distributed Collaborative Data Analysis with Heterogeneous Visualisation Systems (Inproceedings) In: Jean M. Favre, Luis Paulo Santos, Dirk Reiners (Ed.): 7th Eurographics Symposium on Parallel Graphics and Visualization (EGPGV), Lugano, Switzerland, May 20-21, 2007, pp. 21–28, The Eurographics Association, 2007. @inproceedings{Duessel2007, |
2006 |
Andreas Gerndt, Samuel Sarholz, Marc Wolter, Dieter Mey, Christian Bischof, Torsten Kuhlen Nested OpenMP for Efficient Computation of 3D Critical Points in Multi-Block CFD Datasets (Inproceedings) In: ACM/IEEE International Conference for High Performance Computing, Networking, Storage and Analysis (SC06), Tampa, FL, USA, November 11-17, 2006, ACM New York, NY, USA, 2006. @inproceedings{Gerndt2006c, |
Marc Wolter, Andreas Gerndt, Torsten Kuhlen, Christian Bischof Markov Prefetching for Multi-Block Tracing on Parallel Post-Processors (Inproceedings) In: Jang-Hyuk Kwon, Jacques Periaux, Pat Fox, Nobuyuki Satofuka, Akin Ecer (Ed.): International Conference on Parallel Computational Fluid Dynamics (ParCFD 2006), Busan, Korea, May 15-18, 2006, pp. 27–34, Elsevier Science, 2006. @inproceedings{Wolter2006b, |
Andreas Gerndt, Samuel Sarholz, Marc Wolter, Dieter Mey, Christian Bischof, Torsten Kuhlen 3-D Critical Points Computed by Nested OpenMP (Inproceedings) In: Alan Heirich, Bruno Raffin, Luis Paulo Santos (Ed.): 6. Eurographics Symposium on Parallel Graphics and Visualization (EGPGV), Braga, Portugal, May 11-12, 2006, pp. 21–24, 2006, (Short Papers Proceedings). @inproceedings{Gerndt2006b, |
Marc Wolter, Bernd Hentschel, Marc Schirski, Andreas Gerndt, Torsten Kuhlen Time Step Prioritising in Parallel Feature Extraction on Unsteady Simulation Data (Inproceedings) In: Alan Heirich, Bruno Raffin, Luis Paulo Santos (Ed.): 6. Eurographics Symposium on Parallel Graphics and Visualization (EGPGV), Braga, Portugal, May 11-12, 2006, pp. 91–98, The Eurographics Association, 2006. @inproceedings{Wolter2006a, |
Andreas Gerndt Fakultät für Mathematik, Informatik und Naturwissenschaften, RWTH Aachen University, Germany, 2006. @phdthesis{Gerndt2006a, |
2005 |
Andreas Gerndt, Torsten Kuhlen, Christian Bischof VIRACOCHA: Paralleles CFD-Postprocessing für die echtzeitfähige Visualisierung und Interaktion in VR-basierten Arbeitsumgebungen (Inproceedings) In: Torsten Kuhlen, Leif Kobbelt, Stefan Müller (Ed.): Virtuelle und Erweiterte Realität - 2. Workshop der GI-Fachgruppe VR/AR, Aachen, Germany, September 26-27, 2005, pp. 159–170, Shaker Verlag, 2005. @inproceedings{GERN05b, |
Andreas Gerndt, Marc Schirski, Torsten Kuhlen, Christian Bischof Parallel Calculation of Accurate Path Lines in Virtual Environments through Exploitation of Multi-Block CFD Data Set Topology (Journal Article) In: Journal of Mathematical Modelling and Algorithms (JMMA), vol. 4, no. 1, pp. 35–52, 2005. @article{GERN05a, |
2004 |
Andreas Gerndt, Bernd Hentschel, Marc Wolter, Torsten Kuhlen, Christian Bischof VIRACOCHA: An Efficient Parallelization Framework for Large-Scale CFD Post-Processing in Virtual Environments (Inproceedings) In: ACM/IEEE Conference on Supercomputing (SC04), Pittsburgh, PA, USA, November 6-12, 2004, IEEE Computer Society, Washington, DC, USA, 2004. @inproceedings{Gerndt2004c, |
Andreas Gerndt, Stefan Lankes, Mark Asbach, Torsten Kuhlen, Thomas Bemmerl, Christian Bischof Conceptual Design and Implementation of a Pipeline-Based VR-System Parallelized by CORBA, and Comparison with Existing Approaches (Inproceedings) In: International Conference on Virtual Reality Continuum and its Applications in Industry (VRCAI 2004), Singapore, June 16-18, 2004, pp. 368–374, ACM SIGGRAPH, 2004. @inproceedings{Gerndt2004b, |
Andreas Gerndt, Torsten Kuhlen, Thomas Reimersdahl, Matthias Haack, Christian Bischof VR-based Interactive CFD Data Comparison of Flow Fields in a Human Nasal Cavity (Inproceedings) In: Robert L. Galloway (Ed.): SPIE Medical Imaging 2004: Visualization, Image-Guided Procedures, and Display, San Diego, CA, USA, February 14-19, 2004, pp. 65–76, SPIE, Bellingham, WA, USA, 2004. @inproceedings{Gerndt2004a, |
2003 |
Andreas Gerndt, Marc Schirski, Thorsten Kuhlen, Christian Bischof Parallel Calculation of Accurate Path Lines using Multi-Block CFD Datasets with Changing Geometry (Inproceedings) In: Hamid R. Arabnia, Youngsong Mun (Ed.): International Conference on Parallel and Distributed Processing Techniques and Application (PDPTA'03), Las Vegas, Nevada, USA, June 23-26, 2003, pp. 1298–1304, CSREA Press, 2003. @inproceedings{Gerndt2003b, |
Andreas Gerndt, Thomas Reimersdahl, Torsten Kuhlen, Christian Bischof, Ingolf Hörschler, Matthias Meinke, Wolfgang Schröder Large-Scale CFD Data Handling in a VR-Based Otorhinolaryngological CAS-System using a Linux-Cluster (Journal Article) In: The Journal of Supercomputing - An International Journal of High-Performance Computer Design, Analysis, and Use, vol. 25, no. 2, pp. 143–154, 2003, ISSN: 0920-8542. @article{Gerndt2003a, |
Marc Schirski, Andreas Gerndt, Thomas Reimersdahl, Torsten Kuhlen, Philipp Adomeit, Oliver Lang, Stefan Pischinger, Christian Bischof ViSTA FlowLib - A Framework for Interactive Visualization and Exploration of Unsteady Flows in Virtual Environments (Inproceedings) In: Andreas Kunz, Joachim Deisinger (Ed.): 7th International Immersive Projection Technologies Workshop / 9th Eurographics Workshop on Virtual Environments (IPT/EGVE), Zurich, Switzerland, May 22-23, 2003, pp. 77–85, ACM Siggraph, 2003. @inproceedings{Schirski2003, |
2001 |
Thomas Reimersdahl, Ingolf Hörschler, Andreas Gerndt, Torsten Kuhlen, Matthias Meinke, Georg Schlöndorff, Wolfgang Schröder, Christian Bischof Airflow Simulation inside a Model of the Human Nasal Cavity in a Virtual Reality-based Rhinological Operation Planning System (Inproceedings) In: Heinz U. Lemke, Michael W. Vannier, Kiyonari Inamura, Allan G. Farman, Kunio Doi (Ed.): Computer-Assisted Radiology and Surgery (CARS 2001), 15th International Congress and Exhibition, Berlin, Germany, June 27-30, 2001, pp. 85–90, Elsevier, 2001. @inproceedings{Reimersdahl2001, |
Andreas Gerndt, Thomas Reimersdahl, Torsten Kuhlen, Christian Bischof Large Scale CFD Data Handling in a VR-based Otorhinolaryngological CAS-System using a Linux-Cluster (Inproceedings) In: Hamid R. Arabnia (Ed.): International Conference on Parallel and Distributed Processing Techniques and Application (PDPTA'01), Las Vegas, Nevada, USA, June 25-28, 2001, pp. 1773–1779, CSREA Press, Athens, GA, USA, 2001. @inproceedings{Gerndt2001,Many oft he operations to eliminate complaints concerning respiration impairments fail. In order to improve the success rate it is important to recognize the responsiveness of the flow field within the nose's cavities. Therefore we are developing a Computer Assisted Surgery (CAS) system that combines Computational Fluid Dynamics (CFD) and Virtual Reality (VR) technology. However, the primary prerequisite for VR-based applications is real-time interaction. A single graphics workstation is not capable of satisfying this condition and of simultaneously calculating flow features employing the huge CFD dataset. In this paper we will present our approach of a distributed system that relieves the load on the graphics workstation and makes use of an "off-the-shelf" parallel Linux cluster in order to calculate streamlines. Moreover, we introduce first results and discuss remaining difficulties. |
Andreas Gerndt, Thomas Reimersdahl, Torsten Kuhlen, Christian Bischof Large Scale CFD Data Handling with Off-The-Shelf PC-Clusters in a VR-based Rhinological Operation Planning System (Inproceedings) In: Peter Wilders, Akin Ecer, Jacques Periaux, Nobuyuki Satofuka, Pat Fox (Ed.): 13th Parallel Computational Fluid Dynamics - Practice and Theory, Egmond aan Zee, The Netherlands, May 21-23, 2001, pp. 135–142, Elsevier Science B.V., 2001, ISBN: 0-444-50672-1. @inproceedings{Gerndt2002,The human nose can suffer from different complaints. However, many operations to eliminate respiration impairments fail. In order to improve the success rate it is important to recognize the responsiveness of the flow field within the nose’s cavities. Therefore, weare developing an operation planning system that combines Computational Fluid Dynamics (CFD) and Virtual Reality (VR) technology. The primary prerequisite for VR-based applications is real-time interaction. A single graphics workstation is not capable of satisfying this condition and of simultaneously calculating flow features employing the huge CFD data set. In this paper we will present our approach of a distributed system that relieves the load on the graphics workstation and makes use of an ”off-the-shelf” parallel Linux cluster in order to calculate streamlines. Moreover, we introduce first results and discuss remaining difficulties. |
2000 |
Andreas Gerndt, Thomas Reimersdahl, Torsten Kuhlen, Jörg Henrichs, Christian Bischof A Parallel Approach for VR-based Visualization of CFD Data with PC Clusters (Inproceedings) In: Michel Deville, Robert Owens (Ed.): 16th IMACS World Congress 2000 on Scientific Computation, Applied Mathematics and Simulation, Lausanne, Switzerland, August 21-25, 2000, IMACS, New Brunswick, NJ, USA, 2000, (http://publications.rwth-aachen.de/record/110535). @inproceedings{Gerndt2000,In this paper we present two CFD visualization projects based on our virtual reality software toolkit ViSTA (Virtual Reality Software University of Technology Aachen). We describe an environment for parallelized visualization algorithms to achieve a fluent visualization of large datasets. Moreover, we present a first implementation of this parallel concept on PC clusters, show attempts to resolve remaining difficulties, and introduce first results. |
Thomas Reimersdahl, Torsten Kuhlen, Andreas Gerndt, Jörg Henrichs, Christian Bischof ViSTA: A Multimodal, Platform-independent VR-Toolkit Based on WTK, VTK, and MPI (Inproceedings) In: 4th International Immersive Projection Technology Workshop (IPT 2000), Ames, Iowa, USA, June 19-20, 2000, Iowa State University, 2000. @inproceedings{Reimersdahl2000, |
2022 |
CosmoScout VR – A Modular 3D Solar System Based on SPICE (Inproceedings) In: IEEE Aerospace Conference, Hybrid Event (Big Sky, MO, USA), March 5-12, 2022, IEEE, 2022. |
Utilizing Multi-level Concepts for Multi-phase Modeling (Journal Article) In: Software and Systems Modeling, 2022. |
2021 |
Utilising Urgent Computing to Tackle the Spread of Mosquito-borne Diseases (Inproceedings) In: IEEE/ACM Supercomputing, Workshop, HPC for Urgent Decision Making (UrgentHPC), ST. Louis, MO, USA, Nov. 19, 2021, ACM/IEEE, 2021. |
Comparison of Depth Buffer Techniques for Large and Detailed 3D Scenes (Inproceedings) In: GI VR/AR 2021, GI Worskhop, Virtual Event, Sep. 9-10, 2021, 2021. |
Augmented Reality for Massive Particle Distribution (Inproceedings) In: GI VR/AR 2021, GI Worskhop, Virtual Event, Sep. 9-10, 2021, 2021, (BEST PAPER AWARD). |
A Modular Approach to Non-deterministic Dynamic Fault Trees with Repair (Inproceedings) In: 40th International Conference on Computer Safety, Reliability and Security (SafeComp2021), Sep. 7-10, York, UK, 2021, 2021. |
Tasking Modeling Language: A toolset for model-based engineering of data-driven software systems (Inproceedings) In: 2nd European Workshop on On-Board Data Processing (OBDP2021), ESA Workshop, June 14-17, 2021, 2021. |
ScOSA System Software: The Reliable And Scalable Middleware For A Heterogeneous And Distributed On-board Computer Architecture (Journal Article) In: CEAS Space Journal, 2021. |
Interactive Visualization and Topology-based Analysis of Large-scale Time-varying Remote-sensing Data: Challenges and Opportunities (Inproceedings) In: EGU General Assembly 2021, Conference Abstracts, Online, April 19-30, 2021, 2021, (Extended Abstract). |
The BECCAL Experiment Design and Control Software (Inproceedings) In: IEEE Aerospace Conference, Virtual Event, March 6-20, 2021, IEEE, 2021. |
A Constraints-based Interaction System for Spacecraft Design in Augmented Reality (Inproceedings) In: IEEE Aerospace Conference, Virtual Event, March 6-20, 2021, IEEE, 2021. |
2020 |
Modeling and Simulation of a Spacecraft Payload Hardware Using Machine Learning Techniques (Inproceedings) In: ASCEND 2020, Virtual Event, Nov. 16-18, 2020, American Institute of Aeronautics and Astronautics (AIAA), 2020. |
Model-Based Reconfiguration Planning for a Distributed On-board Computer (Inproceedings) In: 12th System Analysis and Modelling (SAM) Conference - Languages, Methods and Tools for AI-based Systems, co-located with MODELS 2020, Virtual Event, Oct. 19-20, 2020, pp. 55–62, Association for Computing Machinery (ACM), 2020. |
Shared Data Types for OSRA and TASTE using Modern C++ (Inproceedings) In: Workshop on Model Based Space Systems and Software Engineering (MBSE2020), ESA-Workshop, Virtual Event, Sep. 28-29, 2020, 2020. |
Synthesizing and Optimizing FDIR Recovery Strategies from Fault Trees (Journal Article) In: Science of Computer Programming, vol. 196, pp. 102478, 2020. |
A Fault-tolerant, Scalable and Distributed Middleware for Future Space Missions (Inproceedings) In: Deutscher Luft- und Raumfahrtkongress (DLRK), Online Event, Sep. 1-3, 2020, Deutsche Gesellschaft für Luft- und Raumfahrt, 2020. |
Towards an FDIR Software Fault Tree Library for Onboard Computers (Inproceedings) In: IEEE Aerospace Conference, Yellowstone Conference Center, Big Sky, Montana, March 8-13, 2020, pp. 1–10, IEEE, 2020. |
Evaluation of Interaction Techniques for Early PhaseSatellite Design in Immersive AR (Inproceedings) In: IEEE Aerospace Conference, Yellowstone Conference Center, Big Sky, Montana, March 8-13, 2020, IEEE, 2020. |
2019 |
Collaborative Virtual Reality Platform for Visualizing Space Data and Mission Planning (Journal Article) In: Multimedia Tools and Applications, Springer, June 1, 2019, vol. 78, no. 23, pp. 33191–33220, 2019, ISSN: 1380-7501. |
Creating a Reliable Data Type Framework for the OSRA Using Modern C++ (Inproceedings) In: 70th International Astronautical Congress (IAC), Washington, D.C., USA, Oct. 21-25, 2019, International Astronautical Federation (IAF), 2019. |
Spacecraft Interface Management in Concurrent Engineering Sessions (Inproceedings) In: 16th International Conference on Cooperative Design, Visualization and Engineering (CDVE2019), Mallorca, Spain, Oct. 6-9, 2019, pp. 54–63, Springer, Cham, 2019. |
Digital Availability of Product Information for Collaborative Engineering of Spacecraft (Inproceedings) In: 16th International Conference on Cooperative Design, Visualization and Engineering (CDVE2019), Mallorca, Spain, Oct. 6-9, 2019, pp. 74–83, Springer, Cham, 2019. |
Event-Driven Multithreading Execution Platform for Real-Time On-Board Software Systems (Inproceedings) In: Adam Lackorzynski, Daniel Lohmann (Ed.): 15th Workshop on Operating Systems Platforms for Embedded Real-Time Applications (OSPERT), Stuttgart, Germany, July 9, 2019, pp. 29–34, 2019. |
FDIR Handling in Eu:CROPIS (Inproceedings) In: 12th IAA Symposium on Small Satellites for Earth Observation, Berlin, Germany, May 06-10, 2019, International Academy of Astronautics (IAA), 2019. |
Dynamic Fault Tree Analysis for a Distributed Onboard Computer (Inproceedings) In: IEEE Aerospace Conference, Yellowstone Conference Center, Big Sky, Montana, March 2-9, 2019, IEEE, 2019. |
Evaluation and Development of the Interaction Layer for Inter-Component Communication of the Onboard Software Reference Architecture (Inproceedings) In: IEEE Aerospace Conference, Yellowstone Conference Center, Big Sky, Montana, March 2-9, 2019, IEEE, 2019. |
Augmented Reality for Remote Collaboration in Aircraft Maintenance Tasks (Inproceedings) In: IEEE Aerospace Conference, Yellowstone Conference Center, Big Sky, Montana, March 2-9, 2019, IEEE, 2019. |
Synthesizing and Optimizating FDIR Recovery Strategies from Fault Trees (Inproceedings) In: Cyrille Artho, Peter Csaba Ölveczky (Ed.): 6th International Workshop on Formal Techniques for Safety-Critical Systems (FTSCS), ICEFM Workshop, Gold Coast, Australia, November 16, 2018, pp. 37–54, Springer, Cham, 2019. |
Synthesizing Failure Detection, Isolation, and Recovery Strategies from Nondeterministic Dynamic Fault Trees (Journal Article) In: Journal of Aerospace Information Systems (JAIS), vol. 16, no. 2, pp. 52–60, 2019. |
2018 |
3D Spacecraft Configuration using Immersive AR Technology (Inproceedings) In: Jens Herder, Christian Geiger, Ralf Dörner, Paul Grimm (Ed.): Virtuelle und Erweiterte Realität: 15. Workshop der GI-Fachgruppe VR/AR, Düsseldorf, Germany, October 10-11, 2018, pp. 71–82, Shaker Verlag, 2018. |
A Model-Driven Software Architecture for Ultra-Cold Gas Experiments in Space (Inproceedings) In: 69th International Astronautical Congress (IAC), Bremen, Germany, October 1-5, International Astronautical Federation (IAF) 2018. |
Enabling a Conceptual Data Model and Workflow Integration Environment for Concurrent Launch Vehicle Analysis (Inproceedings) In: 69th International Astronautical Congress (IAC), Bremen, Germany, October 1-5, 2018, International Astronautical Federation (IAF) 2018. |
Towards a Conceptual Data Model for Fault Detection, Isolation and Recovery in Virtual Satellite (Inproceedings) In: 8th International Systems & Concurrent Engineering for Space Applications Conference (SECESA), Glasgow, UK, September 26-28, 2018, ESA 2018. |
Toward a Digital Platform for Spacecraft Manufacturing (Inproceedings) In: 8th International Systems & Concurrent Engineering for Space Applications Conference (SECESA), Glasgow, UK, September 26-28, 2018, ESA 2018. |
Template-Based 3D Reconstruction of Non-rigid Deformable Object from Monocular Video (Journal Article) In: 3D Research, 3D Display Research Center, Springer Link, vol. 9, iss. 2, 2018. |
Model-Based Software Engineering for an Optical Navigation System for Spacecraft (Journal Article) In: CEAS Space Journal, Springer, Vienna, vol. 10, iss. 2, pp. 147-156, 2018. |
Conceptual Data Model - A Foundation for Successful Concurrent Engineering (Journal Article) In: Concurrent Engineering: Research and Applications (CERA), vol. 26, iss. 1, pp. 55-76, 2018. |
2017 |
A Study of Uncertainty Analysis for Formation Satellite Detection System in Space Science Mission (Inproceedings) In: 68th International Astronautical Congress (IAC), Adelaide, Australia, September 25-29, 2017, International Astronautical Federation (IAF) 2017. |
Task-Node Mapping in an Arbitrary Computer Network Using SMT Solver (Inproceedings) In: Nadia Polikarpova, Steve Schneider (Ed.): 13th International Conference on Integrated Formal Methods (iFM 2017), Torino, Italy,September 18-22, 2017, pp. 177–191, Springer, Cham, 2017. |
Synthesizing FDIR Recovery Strategies From Non-Deterministic Dynamic Fault Trees (Inproceedings) In: AIAA SPACE and Astronautics Forum and Exposition, Orlando, Florida, September 12-14, 2017, AIAA Association, 2017. |
Implementing Model-based System Engineering for the Whole Lifecycle of a Spacecraft (Journal Article) In: CEAS Space Journal, Springer, Vienna, vol. 9, no. 3, pp. 351–365, 2017. |
Deduced Software Design Principles from Experiences with the Technical Debt in Reused Software (Inproceedings) In: Rainer Sandau, Klaus Brieß, Eberhard Gill (Ed.): 11th International Symposium on Small Satellite for Earth Observation, Berlin, April 24-28, 2017, pp. 389–392, Wissenschaft und Technik, 2017. |
Real-time Immersive Visualization for Satellite Configuration and Version Comparison (Inproceedings) In: Simulation and EGSE for European Space Programmes (SESP 2017), European Space Agency (ESA) Workshop, Noordwijk, The Netherlands, March 28-30, 2017, ESA 2017. |
2016 |
Simulation of Hard Shadows on Large Spherical Terrains (Journal Article) In: 3D Research, Springer-Verlag, Berlin - Heidelberg, vol. 7, no. 4, 2016. |
A New SpaceWire Protocol for Reconfigurable Distributed On-Board Computers (Inproceedings) In: International SpaceWire Conference, Yokohama, Japan, October 25-27, 2016, pp. 175–182, IEEE, 2016. |
Conceptual Data Model - A Foundation For Successful Concurrent Engineering (Inproceedings) In: 7th International Systems & Concurrent Engineering for Space Applications Conference (SECESA), Madrid, Spain, October 5-7, 2016, ESA 2016. |
A Component-Based Middleware for a Reliable Distributed and Reconfigurable Spacecraft Onboard Computer (Inproceedings) In: 35th Symposium on Reliable Distributed Systems (SRDS), Budapest, Hungary, September 26-29, 2016, pp. 337–342, IEEE, 2016, (Short Paper). |
Implementing Model Based System Engineering for the Whole Lifecycle of a Spacecraft (Inproceedings) In: Deutscher Luft- und Raumfahrtkongress (DLRK), Braunschweig, Germany, September 13-15, 2016, Deutsche Gesellschaft für Luft- und Raumfahrt - Lilienthal-Oberth e.V., 2016. |
Model-Based Software Engineering for an Optical Navigation System for Spacecraft (Inproceedings) In: Deutscher Luft- und Raumfahrtkongress (DLRK), Braunschweig, Germany, September 13-15, 2016, Deutsche Gesellschaft für Luft- und Raumfahrt - Lilienthal-Oberth e.V., 2016. |
A Lightweight Electrotactile Feedback Device for Grasp Improvement in Immersive Virtual Environments (Inproceedings) In: Tobias Höllerer, Victoria Interrante, Anatole Lécuyer, Evan Suma (Ed.): IEEE Virtual Reality Conference (VR), Greenville, SC, USA, March 19-23, 2016, pp. 39–48, IEEE, 2016. |
Using Timed Automata to Check Space Mission Feasibility in the Early Design Phases (Inproceedings) In: IEEE Aerospace Conference, Yellowstone Conference Center, Big Sky, MT, USA, March 5-12, IEEE, 2016. |
OBC-NG Concept and Implementation (Technical Report) Deutsches Zentrum für Luft- und Raumfahrt (DLR) no. DLR-FB-2016-3, 2016. |
2015 |
A Real-Time Physically Based Algorithm for Hard Shadows on Dynamic Height-Fields (Inproceedings) In: André Hinkenjann, Jens Maiero, Roland Blach (Ed.): Virtuelle und Erweiterte Realität, 12. Workshop der GI-Fachgruppe VR/AR, Sankt Augustin, Germany, September 10-11, 2015, pp. 101–112, Shaker Verlag, Aachen, 2015. |
Interactive 3D Visualization to Support Concurrent Engineering in the Early Space Mission Design Phase (Inproceedings) In: Challenges in European Aerospace (CEAS), CEAS Air & Space Conference, Delft, The Netherlands, September 7-11, 2015, Council of European Aerospace Societies (CEAS), 2015. |
Dynamic Scheduling for Progressive Large-Scale Visualisation (Inproceedings) In: Enrico Bertini, Jessie Kennedy, Enrico Puppo (Ed.): Eurographics Conference on Visualization (EuroVis), Short Papers, Cagliari, Italy, May 25-29, 2015, pp. 37–41, The Eurographics Association, 2015. |
Model Driven Language Framework to Automate Command and Data Handling Code Generation (Inproceedings) In: IEEE Aerospace Conference, Big Sky, MT, USA, March 7-14, 2015, pp. 1–9, IEEE, 2015. |
VR-OOS: The DLR's Virtual Reality Simulator for Telerobotic On-Orbit Servicing with Haptic Feedback (Inproceedings) In: IEEE Aerospace Conference, Big Sky, MT, USA, March 7-14, 2015, IEEE, 2015. |
A Collaborative Workspace for Strengthening Collaboration among Space Scientists (Inproceedings) In: IEEE Aerospace Conference, Big Sky, MT, USA, March 7-14, 2015, IEEE, 2015. |
2014 |
Collaborative Modeling and Simulation in Spacecraft Design (Incollection) In: Daniele Gianni, Andrea D'Ambrogio, Andreas Tolk (Ed.): Modeling and Simulation-Based Systems Engineering Handbook, pp. 149–179, CRC Press, 2014. |
Interface Management in Concurrent Engineering Facilities for Systems and Service Systems Engineering: A Model-based Approach (Inproceedings) In: Italian INCOSE Conference on Systems Engineering (CIISE), Rome, Italy, November 24-25, 2014, pp. 72–81, INCOSE Italia 2014. |
In: 6th International Conference on Systems & Concurrent Engineering for Space Applications (SECESA), Stuttgart, Germany, October 8-10, 2014, ESA 2014. |
Bidirectional Graphical Modelling Supporting Concurrent Spacecraft Design (Inproceedings) In: 6th International Conference on Systems & Concurrent Engineering for Space Applications (SECESA), Stuttgart, Germany, October 8-10, 2014, ESA 2014. |
ExaScale Pre- and Post-Processing - Strategy and Software Technology (Technical Report) CRESTA Consortium no. 3, 2014. |
Distributed Post-Processing and Rendering for Large-Scale Scientific Simulations (Incollection) In: Charles D. Hansen, Min Chen, Christopher R. Johnson, Arie E. Kaufman, Hans Hagen (Ed.): Scientific Visualization: Uncertainty, Multifield, Biomedical, and Scalable Visualization, pp. 381–398, Springer, London, 2014. |
Model Linking to Improve Visibility and Reusability of Models during Space System Development (Inproceedings) In: IEEE Aerospace Conference, Big Sky, MT, USA, March 1-8, 2014, IEEE, 2014. |
OBC-NG: Towards a Reconfigurable On-board Computing Architecture for Spacecraft (Inproceedings) In: IEEE Aerospace Conference, Big Sky, MT, USA, March 1-8, 2014, IEEE, 2014. |
A Modular Architecture for an Interactive Real-time Simulation and Training Environment for Satellite On-orbit Servicing (Journal Article) In: Journal of Simulation (JOS), Palgarve Macmillan, UK, vol. 8, no. 1, pp. 50–63, 2014. |
Fallbeispiel für VR/AR - Virtuelle Satellitenreparatur im Orbit (Incollection) In: Ralf Dörner, Wolfgang Broll, Paul Grimm, Bernhard Jung (Ed.): Virtual und Augmented Reality (VR/AR) - Grundlagen und Methoden der Virtuellen und Augmentierten Realit"at, eXamen.press, pp. 303–305, Springer Vieweg, 2014. |
2013 |
Usability Evaluation of Two Simple Methods for Representing Heaviness of Virtual Objects (Inproceedings) In: Marc Erich Latoschik, Oliver Staadt, Frank Steinicke (Ed.): Virtuelle und Erweiterte Realität, 10. Workshop der GI-Fachgruppe VR/AR, Würzburg, September 19-20, 2013, pp. 157–168, Shaker Verlag, 2013. |
Physically Based Rendering of the Martian Atmosphere (Inproceedings) In: Marc Erich Latoschik, Oliver Staadt, Frank Steinicke (Ed.): Virtuelle und Erweiterte Realität, 10. Workshop der GI-Fachgruppe VR/AR, Würzburg, September 19-20, 2013, pp. 97–108, Shaker Verlag, Aachen, 2013. |
A Continuous Verification Process in Concurrent Engineering (Inproceedings) In: AIAA Space Conference, San Diego, CA, USA, September 10-12, 2013, 2013. |
Taking Advantage of the Model: Application of the Quantity, Units, Dimension, and Values Standard in Concurrent Spacecraft Engineering (Inproceedings) In: 23rd Annual International Symposium of the International Council of Systems Engineering (INCOSE), Philadelphia, PA, USA, June 24-27, 2013, pp. 878–888, Wiley, 2013. |
The Generalized Processing Chain for BIRD and FireBIRD Mission (Inproceedings) In: Rainer Sandau, Hans-Peter Röser, Arnoldo Valenzuela (Ed.): 9th IAA Symposium Small Satellites for Earth Observations, Berlin, Germany, April 8-12, 2013, Wissenschaft und Technik Verlag Berlin, 2013. |
Safe Integration of Payload Experiments in an AOCS (Inproceedings) In: Rainer Sandau, Hans-Peter Röser, Arnoldo Valenzuela (Ed.): 9th IAA Symposium on Small Satellites for Earth Observation, Berlin, April 8-12, 2013, pp. 423–426, Wissenschaft & Technik Verlag, 2013. |
An Evaluation of Two Simple Methods for Representing Heaviness in Immersive Virtual Environments (Inproceedings) In: Anatole Lécuyer, Frank Steinicke, Mark Billinghurst (Ed.): IEEE Symposium on 3D User Interfaces (3DUI), Orlando, FL, USA, March 16-17, 2013, pp. 87–94, IEEE, 2013. |
Exploration of Time-dependent Paleoceanographic Flow Data in Virtual Reality (Inproceedings) In: GeoViz Worshop, Hamburg, Germany, March 6-8, 2013, 2013, (Extended Abstract). |
A Formal Method for Early Spacecraft Design Verification (Inproceedings) In: IEEE Aerospace Conference, Big Sky, MT, USA, March 2-9, 2013, IEEE, 2013. |
2012 |
In: Preparing Applications for Exascale Through Co-design, SC 2012 Workshop, Salt Lake City, UT, USA, November 16, 2012, IEEE, 2012. |
Automated Sensitivity Analysis in Early Space Mission Design (Inproceedings) In: 5th International Workshop on Systems & Concurrent Engineering for Space Applications (SECESA 2012), Lisabon, Portugal, October 17-19, 2012, ESA 2012. |
Towards Interacting with Force-Sensitive Thin Deformable Virtual Objects (Inproceedings) In: Ronan Boulic, Carolina Cruz-Neira, Kiyoshi Kiyokawa, David Roberts (Ed.): Joint Virtual Reality Conference (JVRC), Madrid, Spain, October 16-19, 2012, pp. 17–20, Eurographics Association, 2012, (Short Paper). |
Interactive Retro-Deformation of Terrain for Reconstructing 3D Fault Displacements (Journal Article) In: IEEE Transaction on Visualization and Computer Graphics (TVCG), vol. 18, iss. 12, pp. 2208–2215, 2012. |
Spherical Terrain Rendering Using the Hierarchical HEALPix Grid (Inproceedings) In: Visualization of Large and Unstructured Data Sets (VLUDS), IRTG 1131 Workshop, Kaiserslautern, Germany, June 10-11, 2011, Dagstuhl Publishing, October 10, 2012. |
Static Simulation Scheduling for the Validation of Space System Requirement Decomposition (Inproceedings) In: 63rd International Astronautical Congress (IAC), Naples, Italy, October 1-5, 2012, International Astronautical Ferderation (IAF), 2012. |
Formal Verification in Early Mission Planning (Inproceedings) In: Workshp on Simulation and EGSE Facilities for Space Programmes (SESP), Noordwijk, The Netherlands, September 25-27, 2012, 2012. |
Remote GPU-Accelerated Online Pre-processing of Raster Maps for Terrain Rendering (Inproceedings) In: Christian Geiger, Jens Herder, Tom Vierjahn (Ed.): Virtuelle und Erweiterte Realität - 9. Workshop der GI-Fachgruppe VR/AR, Düsseldorf, Germany, September 19-20, 2012, pp. 143–154, Shaker Verlag, 2012. |
Interactive Hybrid Remote Rendering for Multi-pipe Powerwall Systems (Inproceedings) In: Christian Geiger, Jens Herder, Tom Vierjahn (Ed.): Virtuelle und Erweiterte Realität - 9. Workshop der GI-Fachgruppe VR/AR, Düsseldorf, Germany, September 19-20, 2012, pp. 155–166, Shaker Verlag, 2012. |
3D State Decomposition Modeling Method for MBSE in Space Engineering (Inproceedings) In: AIAA SPACE 2012 Conference & Exposition, Pasadena, CA, USA, September 11-13, 2012, AIAA Inc., 2012. |
Decision Support Tool for Concurrent Engineering in Space Mission Design (Inproceedings) In: Josip Stjepandic, Georg Rock, Cees Bil (Ed.): 19th ISPE International Conference on Concurrent Engineering (CE2012), Trier, Germany, September 3-7, 2012, pp. 497–508, Springer Verlag, London, 2012. |
An Evaluation of Open Source Physics Engines for Use in Virtual Reality Assembly Simulations (Inproceedings) In: George Bebis, Richard Boyle, Bahram Parvin, Darko Koracin, Charless Fowlkes, Sen Wang, Min-Hyung Choi, Stephan Mantler, Jürgen Schulze, Daniel Acevedo, Klaus Mueller, Michael Papka (Ed.): 8th International Symposium on Visual Computing (ISVC), Rethymnon, Crete, July 16-18, 2012, pp. 346–357, Springer, 2012. |
Collaborative Development and Cataloging of Simulation and Calculation Models for Space Systems (Inproceedings) In: 21th IEEE International Workshops on Enabling Technologies: Infrastructure for Collaborative Enterprises (WETICE), Toulouse, France, June 25-27, 2012, pp. 244–249, IEEE Computer Society Press, 2012. |
A Framework to Model Metadata for Knowledge Management Tools (Inproceedings) In: 4th International Conference on Knowledge Management for Space Missions, Toulouse Space Show 2012, Toulouse, France, June 25-28, 2012, 2012. |
Interactive In-Situ Online Monitoring of Large Scale CFD Simulations with Cut-Planes (Inproceedings) In: IEEE Virtual Reality Workshop, Immersive Visualization Revisited: Challenges and Opportunities, Orange County, CA, USA, March 4, 2012, 2012, (Short Paper). |
Spatial Analysis of Terrain in Virtual Reality (Inproceedings) In: IEEE Virtual Reality Workshop, Immersive Visualization Revisited: Challenges and Opportunities, Orange County, CA, USA, March 4, 2012, 2012, (Short Paper). |
Collaborative Satellite Configuration Supported by Interactive Visualization (Inproceedings) In: IEEE Aerospace Conference, Big Sky, MT, USA, March 3-10, 2012, IEEE, 2012. |
Open Source Software Framework for Applications in Aeronautics and Space (Inproceedings) In: IEEE Aerospace Conference, Big Sky, MT, USA, March 3-10, 2012, IEEE, 2012. |
2011 |
A Modular Architecture for an Interactive Real-Time Simulation and Training Environment for Satellite On-Orbit Servicing (Inproceedings) In: 15th IEEE/ACM International Symposium on Distributed Simulation and Real Time Applications (DS-RT), Salford, MediaCity, UK, September 4-7, 2011, pp. 72–80, 2011. |
Collaborative Development of a Space System Simulation Model (Inproceedings) In: 20th IEEE International Workshops on Enabling Technologies: Infrastructure for Collaborative Enterprises (WETICE 2011), Paris, France, June 27-29, 2011, pp. 164–169, IEEE Computer Society, 2011. |
Design Model Data Exchange Between Concurrent Engineering Facilities by Means of Model Transformation (Inproceedings) In: 13th NASA-ESA Workshop on Product Data Exchange, Cypress, CA, USA, May 11-12, 2011, NASA/ESA 2011. |
Software Reuse of the BIRD ACS for the TET Satellite Bus (Inproceedings) In: Rainer Sandau, Hans-Peter Röser, Arnoldo Valenzuela (Ed.): 8th IAA Symposium on Small Satellites for Earth Observation, Berlin, Germany, April 4-8, 2011, pp. 409–412, Wissenschaft und Technik Verlag Berlin, 2011. |
2010 |
FSSteering: A Distributed Framework for Computational Steering in a Script-based CFD Simulation Environment (Inproceedings) In: Werner Benger, Andreas Gerndt, Simon Su, Wolfram Schoor, Michael Koppitz, Wolfgang Kapferer, Hans-Peter Bischof, Massimo Di Perro (Ed.): 6th High-End Visualization Workshop, Obergurgl, Austria, December 8-12, 2010, pp. 9–20, Lehmanns Media, Berlin, Germany, 2010. |
Symbolic Abstraction of System Requirements (Inproceedings) In: Systems Engineering Infrastructure Conference (SEISCONF 2010), Ottobrunn, Germany, October 19, 2010, 2010. |
Concurrent Engineering Software Development at German Aerospace Center - Status and Outlook (Inproceedings) In: 4th International Workshop on Systems & Concurrent Engineering for Space Applications (SECESA 2010), Lausanne, Switzerland, October 13-15, 2010, ESA 2010. |
Concurrent Systems Engineering in Aerospace: From Excel-based to Model Driven Design (Inproceedings) In: 8th Conference on Systems Engineering Research (CSER), Hoboken, NJ, March 17-19, 2010, USC/Stevens 2010. |
2009 |
A Generic Simulink Model Template for Simulation of Small Satellites (Inproceedings) In: Rainer Sandau, Hans-Peter Röser, Arnoldo Valenzuela (Ed.): 7th IAA Symposium on Small Satellites for Earth Observation, Berlin, Germany, May 4-8, 2009, pp. 247–250, Wissenschaft und Technik Verlag, 2009. |
Post-Processing Pipeline Optimization for Interactive Exploration of Multi-Block Turbine Propulsion Simulation Datasets (Inproceedings) In: Werner Berger, Wolfram Schoor, Simon Su, Andreas Gerndt (Ed.): 5th High-End Visualization Workshop, Baton Rouge, LA, USA, March 18-21, 2009, pp. 62–78, Lehmanns Media, 2009. |
Interactive Exploration of Coastal Restoration Modeling in Virtual Environments (Inproceedings) In: Ian E. McDowall, Margaret Dolinsky (Ed.): 21st Annual Symposium on Electronic Imaging, Conference on the Engineering Reality of Virtual Reality, San Jose, CA, USA, January 18-22, 2009, IS&T/SPIE, 2009. |
Virtual Hydrology Observatory: An Immersive Visualization of Hydrology Modeling (Inproceedings) In: Ian E. McDowall, Margaret Dolinsky (Ed.): 21st Annual Symposium on Electronic Imaging, Conference on the Engineering Reality of Virtual Reality, San Jose, CA, USA, January 18-22, 2009, IS&T/SPIE, 2009. |
2008 |
Overview of the New Concurrent Engineering Facility at DLR (Inproceedings) In: 3rd International Workshop on System & Concurrent Engineering for Space Applications (SECESA), Rome, Italy, October 15-17, 2008, ESA 2008. |
Fire in a Storage: From Simulation to Virtual Environments (Inproceedings) In: 5th INTUITION International Conference, Turin, Italy, Oct. 6-8, 2008, 2008. |
Interactive Tracking of Three-dimensional Critical Points in Unsteady, Large-scale CFD Datasets (Inproceedings) In: Hamid R. Arabnia, Leonidas Deligiannidis (Ed.): The 2008 International Conference on Computer Graphics and Virtual Reality (CGVR'08), Las Vegas, NV, USA, July 14-17, 2008, pp. 22–28, CSREA Press, 2008. |
2007 |
Distributed Collaborative Data Analysis with Heterogeneous Visualisation Systems (Inproceedings) In: Jean M. Favre, Luis Paulo Santos, Dirk Reiners (Ed.): 7th Eurographics Symposium on Parallel Graphics and Visualization (EGPGV), Lugano, Switzerland, May 20-21, 2007, pp. 21–28, The Eurographics Association, 2007. |
2006 |
Nested OpenMP for Efficient Computation of 3D Critical Points in Multi-Block CFD Datasets (Inproceedings) In: ACM/IEEE International Conference for High Performance Computing, Networking, Storage and Analysis (SC06), Tampa, FL, USA, November 11-17, 2006, ACM New York, NY, USA, 2006. |
Markov Prefetching for Multi-Block Tracing on Parallel Post-Processors (Inproceedings) In: Jang-Hyuk Kwon, Jacques Periaux, Pat Fox, Nobuyuki Satofuka, Akin Ecer (Ed.): International Conference on Parallel Computational Fluid Dynamics (ParCFD 2006), Busan, Korea, May 15-18, 2006, pp. 27–34, Elsevier Science, 2006. |
3-D Critical Points Computed by Nested OpenMP (Inproceedings) In: Alan Heirich, Bruno Raffin, Luis Paulo Santos (Ed.): 6. Eurographics Symposium on Parallel Graphics and Visualization (EGPGV), Braga, Portugal, May 11-12, 2006, pp. 21–24, 2006, (Short Papers Proceedings). |
Time Step Prioritising in Parallel Feature Extraction on Unsteady Simulation Data (Inproceedings) In: Alan Heirich, Bruno Raffin, Luis Paulo Santos (Ed.): 6. Eurographics Symposium on Parallel Graphics and Visualization (EGPGV), Braga, Portugal, May 11-12, 2006, pp. 91–98, The Eurographics Association, 2006. |
Fakultät für Mathematik, Informatik und Naturwissenschaften, RWTH Aachen University, Germany, 2006. |
2005 |
VIRACOCHA: Paralleles CFD-Postprocessing für die echtzeitfähige Visualisierung und Interaktion in VR-basierten Arbeitsumgebungen (Inproceedings) In: Torsten Kuhlen, Leif Kobbelt, Stefan Müller (Ed.): Virtuelle und Erweiterte Realität - 2. Workshop der GI-Fachgruppe VR/AR, Aachen, Germany, September 26-27, 2005, pp. 159–170, Shaker Verlag, 2005. |
Parallel Calculation of Accurate Path Lines in Virtual Environments through Exploitation of Multi-Block CFD Data Set Topology (Journal Article) In: Journal of Mathematical Modelling and Algorithms (JMMA), vol. 4, no. 1, pp. 35–52, 2005. |
2004 |
VIRACOCHA: An Efficient Parallelization Framework for Large-Scale CFD Post-Processing in Virtual Environments (Inproceedings) In: ACM/IEEE Conference on Supercomputing (SC04), Pittsburgh, PA, USA, November 6-12, 2004, IEEE Computer Society, Washington, DC, USA, 2004. |
Conceptual Design and Implementation of a Pipeline-Based VR-System Parallelized by CORBA, and Comparison with Existing Approaches (Inproceedings) In: International Conference on Virtual Reality Continuum and its Applications in Industry (VRCAI 2004), Singapore, June 16-18, 2004, pp. 368–374, ACM SIGGRAPH, 2004. |
VR-based Interactive CFD Data Comparison of Flow Fields in a Human Nasal Cavity (Inproceedings) In: Robert L. Galloway (Ed.): SPIE Medical Imaging 2004: Visualization, Image-Guided Procedures, and Display, San Diego, CA, USA, February 14-19, 2004, pp. 65–76, SPIE, Bellingham, WA, USA, 2004. |
2003 |
Parallel Calculation of Accurate Path Lines using Multi-Block CFD Datasets with Changing Geometry (Inproceedings) In: Hamid R. Arabnia, Youngsong Mun (Ed.): International Conference on Parallel and Distributed Processing Techniques and Application (PDPTA'03), Las Vegas, Nevada, USA, June 23-26, 2003, pp. 1298–1304, CSREA Press, 2003. |
Large-Scale CFD Data Handling in a VR-Based Otorhinolaryngological CAS-System using a Linux-Cluster (Journal Article) In: The Journal of Supercomputing - An International Journal of High-Performance Computer Design, Analysis, and Use, vol. 25, no. 2, pp. 143–154, 2003, ISSN: 0920-8542. |
ViSTA FlowLib - A Framework for Interactive Visualization and Exploration of Unsteady Flows in Virtual Environments (Inproceedings) In: Andreas Kunz, Joachim Deisinger (Ed.): 7th International Immersive Projection Technologies Workshop / 9th Eurographics Workshop on Virtual Environments (IPT/EGVE), Zurich, Switzerland, May 22-23, 2003, pp. 77–85, ACM Siggraph, 2003. |
2001 |
Airflow Simulation inside a Model of the Human Nasal Cavity in a Virtual Reality-based Rhinological Operation Planning System (Inproceedings) In: Heinz U. Lemke, Michael W. Vannier, Kiyonari Inamura, Allan G. Farman, Kunio Doi (Ed.): Computer-Assisted Radiology and Surgery (CARS 2001), 15th International Congress and Exhibition, Berlin, Germany, June 27-30, 2001, pp. 85–90, Elsevier, 2001. |
Large Scale CFD Data Handling in a VR-based Otorhinolaryngological CAS-System using a Linux-Cluster (Inproceedings) In: Hamid R. Arabnia (Ed.): International Conference on Parallel and Distributed Processing Techniques and Application (PDPTA'01), Las Vegas, Nevada, USA, June 25-28, 2001, pp. 1773–1779, CSREA Press, Athens, GA, USA, 2001. |
Large Scale CFD Data Handling with Off-The-Shelf PC-Clusters in a VR-based Rhinological Operation Planning System (Inproceedings) In: Peter Wilders, Akin Ecer, Jacques Periaux, Nobuyuki Satofuka, Pat Fox (Ed.): 13th Parallel Computational Fluid Dynamics - Practice and Theory, Egmond aan Zee, The Netherlands, May 21-23, 2001, pp. 135–142, Elsevier Science B.V., 2001, ISBN: 0-444-50672-1. |
2000 |
A Parallel Approach for VR-based Visualization of CFD Data with PC Clusters (Inproceedings) In: Michel Deville, Robert Owens (Ed.): 16th IMACS World Congress 2000 on Scientific Computation, Applied Mathematics and Simulation, Lausanne, Switzerland, August 21-25, 2000, IMACS, New Brunswick, NJ, USA, 2000, (http://publications.rwth-aachen.de/record/110535). |
ViSTA: A Multimodal, Platform-independent VR-Toolkit Based on WTK, VTK, and MPI (Inproceedings) In: 4th International Immersive Projection Technology Workshop (IPT 2000), Ames, Iowa, USA, June 19-20, 2000, Iowa State University, 2000. |