Georg Stettinger

Model-based coupling approach for non-iterative real-time co-simulation

Non-iterative co-simulation is a prerequisite for the time correct coupling of distributed solved numerical problems. For this coupling approach typically signal-based extrapolation schemes are used to resolve existing bidirectional dependencies between the interacting subsystems. Nevertheless, the introduced coupling errors influence the entire system behavior. In the case of coupled real-time systems inherent time-delays and noisy measurements lead to significant additional distortions. Thus, to avoid a deteriorating dynamic behavior of coupled systems - which can even lead to instability - new coupling approaches are mandatory. A model-based extrapolation scheme is motivated to realize a compensation of the occurring round-trip-times and noise-handling. Besides the description of the fundamentals a representative example demonstrates the effectiveness of the proposed coupling approach.

A model-based approach for prediction-based interconnection of dynamic systems

This paper proposes a model based coupling technique for interconnected systems. It helps to overcome problems arising whenever the interconnections have a non-negligible influence on the overall system behavior. The main idea of the method is to use prediction schemes which compensate for performance degradation due to coupling imperfections. Exemplarily the so-called co-simulation scenario is selected to demonstrate the principles of the presented approach and its effectiveness by means of a complex real-time application.

Fault-tolerant coupling of real-time systems: A case study

This paper demonstrates the application of a model-based coupling approach to cope with non negligible coupling imperfections and faults of interconnected real-time systems. Performance degradation of the coupled overall system is prevented via model-based prediction schemes, which compensate for effects caused by e.g. deadline violations of the coupled real-time systems or data losses and transmission time delays due to the communication network. As an example, the real-time co-simulation setup of a modular driving simulator demonstrates the practical applicability and effectiveness of the proposed coupling approach.

TrustVehicle – Improved Trustworthiness and Weather-Independence of Conditionally Automated Vehicles in Mixed Traffic Scenarios

The introduction of automated vehicles to the market raises various questions and problems. One of those problems is the trustworthiness of the automated systems and in this connection the user’s perception and acceptance. The user’s perception is especially important during SAE level 3 automated driving (L3AD), where the driver has to be able to resume vehicle control, and during the initial deployment of automated systems, where mixed traffic situations occur, in which automated and human-driven vehicles share the same road space. The Horizon 2020 project TrustVehicle aims at investigating critical scenarios, especially in mixed traffic situations and under harsh weather conditions, and at improving the trustworthiness and availability of L3AD functionalities through a user-centric approach.

Concepts for improved availability and computational power in automated driving

Automated vehicles are required to operate on highways and in complex urban scenarios. To safely handle these complex environmental influences, sophisticated automated driving functions demand a high availability of all involved components in combination with increased computational power. Particular multi-core platforms are deployed to cope with these demands. To achieve higher system availability for SAE level 3 and higher, fail operational concepts from system level down to Microcontroller Unit (MCU) level are needed. These concepts include hardware as well as software requirements and are discussed in this paper. For an increased computing performance, the idea and further the model of a parallel computation method for driving functions and their control algorithms is introduced. For that a stabilizing controller is implemented on different cores of the multi-core processor. Finally, this resulting closed-loop system is modeled as a hybrid system which will serve as an input for further stability analysis.ZusammenfassungAutonome Fahrzeuge sollen in Zukunft auf Autobahnen sowie in komplexen urbanen Situationen funktionieren. Damit solche hochentwickelten autonomen Fahrsysteme diese komplexen Umwelteinflüsse sicher verarbeiten können, bedarf es einer hohen Verfügbarkeit dieser Systeme sowie einer hohen Prozessorleistung. Dieser Bedarf wird durch den Einsatz von Multi-Core-Prozessoren bewältigt. Höhere Verfügbarkeit von Fahrfunktion mit SAE Level 3 wird durch fehlertolerante Konzepte auf System- bis hin zur Mikrocontroller-Ebene erreicht. Diese Konzepte bestehen aus Hardware- und Software-Anforderungen. Zur Steigerung der Rechenperformance werden hier die Idee und ein Modell für parallele Rechenmethoden für Fahrfunktionen und Regler vorgestellt. Dafür wird ein stabilisierender Regler auf verschiedene Prozessorkerne des Multi-Core-Prozessors implementiert. Schließlich wird die resultierende geschlossene Regelschleife als hybrides System modelliert und kann für weitere Stabilitätsanalysen verwendet werden.

Recursive FIR-Filter design for fault-tolerant real-time co-simulation

The coupling of real-time and non-real-time systems is directly related to different types of faults which require adequate handling. These faults, such as communication time-delays, data-loss or noisy measurements, originate from the incorporation of real hardware (real-time system) and lead to significant challenges in the coupling process. Without compensating their destabilizing effects the simulation results are corrupted. Ignoring those effects can even result in unstable closed-loop systems in the worst case, which may in turn result in hardware damage. This work proposes a recursive FIR-filter design approach which compensates such fault effects. The effectiveness of the proposed coupling filters is demonstrated by a representative example.

Modellbasierte Echtzeit-Co-Simulation: Überblick und praktische Anwendungsbeispiele

ZusammenfassungDiese Arbeit behandelt die sogenannte Echtzeit-Co-Simulationsproblematik. Im Speziellen wird die Einbindung von Hardwarekomponenten in einen Softwareverbund durch kommunikationsbedingte Latenzzeiten und Messrauschen erschwert. Zur Behandlung dieser Störungen wird ein modellbasierter Kopplungsansatz vorgestellt. Mittels Prädiktion von Koppelgrößen können die Auswirkungen von Störeinflüssen deutlich reduziert werden. Die Effektivität dieses Kopplungsansatzes wird an einem Labormodell demonstriert. Darüber hinaus werden einige typische industrielle Anwendungsszenarien skizziert.AbstractThis work deals with the so-called real-time co-simulation problem. In detail, the incorporation of real-time systems into the co-simulation approach is heavily influenced by communication time-delays and noisy coupling signals. In order to overcome the arising problems a model-based coupling approach is presented. The proposed coupling technique is based on identified subsystem models and compensates for time-delays while mitigating the effects of sensor noise. The designed coupling technique is evaluated on a laboratory setup. Additionally, typical industrial applications are presented.

Sliding mode control for constraint stabilization in multi-body system dynamic analysis

For real-time simulation a limited computation time is available for each step and explicit numerical schemes are mandatory. In the case of constraint dynamical systems, a index reduction of the differential algebraic equation system is necessary to solve the system explicitly with respect to a specific time derivative of the original constraint. Different techniques exist to mitigate the resulting drift effect. A control-based approach, the Baumgarte stabilization, introduces a linear constraint violation error behaviour. In this paper, a non-linear control scheme for constraint stabilization is proposed. The sliding mode concepts allows a fast attenuation of the constraint error and thus, an improved numerical accuracy is possible. The continuous time control law is directly embedded into the system equations and solved by the numerical solver at discrete time instants. Typical problems such as chattering and suitable parametrizations are addressed. Both schemes are examined by the use of a theoretical example to demonstrate the performance improvement.