Liyuan Zhang

Bio: Liyuan Zhang is an academic researcher from University of Erlangen-Nuremberg. The author has contributed to research in topics: Design space exploration & Design flow. The author has an hindex of 3, co-authored 6 publications receiving 42 citations.

A co-simulation approach for control performance analysis during design space exploration of cyber-physical systems

Abstract: In modern embedded systems, more and more control applications are executed in a distributed fashion. Here, the architecture as well as the scheduling policies influence the control performance. Thus, considering control performance as design objective at Electronic System Level becomes mandatory. This work presents a control performance analysis approach based on the co-simulation of high level models of plants and a virtual prototype of the controllers in the system. The work in hand integrates this co-simulation in a Design Space Exploration, resulting in a fully automatic toolflow at the ESL that accounts for several control performance metrics as additional principle design objectives together with other design objectives such as monetary cost or energy consumption.

Bridging algorithm and ESL design: Matlab/Simulink model transformation and validation

Abstract: Matlab/Simulink is today's de-facto standard for model-based design in domains such as control engineering and signal processing. Particular strengths of Simulink are rapid design and algorithm exploration. Moreover, commercial tools are available to generate embedded C or HDL code directly from a Simulink model. On the other hand, Simulink models are purely functional models and, hence, designers cannot seamlessly consider the architecture that a Simulink model is later implemented on. In particular, it is not possible to explore the different architectural alternatives and investigate the arising interactions and side-effects directly within Simulink. To benefit from Matlab/Simulink's algorithm exploration capabilities and overcome the outlined drawbacks, this work introduces a model transformation framework that converts a Simulink model to an executable specification, written in an actor-oriented modeling language. This specification then serves as the input of well-established Electronic System Level (ESL) design flows that, e. g., enables Design Space Exploration (DSE) and automatic code generation for both hardware and software. We also present a validation technique that considers the functional correctness by comparing the original Simulink model with the generated specification in a co-simulation environment. The co-simulation can also be used to evaluate the performance of implementation candidates during DSE. As case study, we present and investigate a torque vectoring application from an electric automotive vehicle.

A co-simulation approach for system-level analysis of embedded control systems

Abstract: Control applications have become an integral part of modern networked embedded systems. However, there often exists a gap between control engineering and system design. The control engineer has detailed knowledge about the algorithms but is abstracting from the system architecture and implementation. On the other hand, the system designer aims at achieving high-quality implementations based on quality constraints specified by the control engineer. This may result in either an overdesigned system in case the specifications are pessimistic or an unsafe system behavior when specifications are too optimistic. Thus, future design automation approaches have to consider the quality of control applications both as design objectives and design constraints to achieve safe yet highly optimized system implementations. The work at hand introduces an automatic tool flow at the Electronic System Level (ESL) that enables the optimization of a system implementation with quality of control being introduced as a principal design objective, like the maximum braking distance, while respecting constraints like maximum slip to ensure maneuverability of a car. The gap between mathematically well-defined models for system synthesis and common analysis techniques for control quality is bridged by co-simulation: A SystemC-based virtual prototype of a distributed controller implementation is combined with high-level models of the plants specified in Matlab/Simulink. Through a model transformation, the traditional development process of control applications is combined with state-of-the-art ESL techniques, ensuring model consistency while enabling a high degree of automation.

Hardware/Software Codesign: The Past, the Present, and Predicting the Future

Abstract: Hardware/software codesign investigates the concurrent design of hardware and software components of complex electronic systems. It tries to exploit the synergy of hardware and software with the goal to optimize and/or satisfy design constraints such as cost, performance, and power of the final product. At the same time, it targets to reduce the time-to-market frame considerably. This paper presents major achievements of two decades of research on methods and tools for hardware/software codesign by starting with a historical survey of its roots, by highlighting its major research directions and achievements until today, and finally, by predicting in which direction research in codesign might evolve in the decades to come.

Comprehensive Abstraction of VHDL RTL Cores to ESL SystemC

Abstract: ..................................................................................................... 90 KOKKUVÕTE .................................................................................................. 92 ACKNOWLEDGEMENTS ............................................................................... 94 Appendix A ........................................................................................................ 95 Appendix B ...................................................................................................... 103 Appendix C ...................................................................................................... 109 Appendix D ...................................................................................................... 117 Appendix E ...................................................................................................... 125 Appendix F ...................................................................................................... 133

Cyber-physical systems design: formal foundations, methods and integrated tool chains

Abstract: The engineering of dependable cyber-physical systems (CPSs) is inherently collaborative, demanding cooperation between diverse disciplines. A goal of current research is the development of integrated tool chains for model-based CPS design that support co-modelling, analysis, co-simulation, testing and implementation. We discuss the role of formal methods in addressing three key aspects of this goal: providing reasoning support for semantically heterogeneous models, managing the complexity and scale of design space exploration, and supporting traceability and provenance in the CPS design set. We briefly outline an approach to the development of such a tool chain based on existing tools and discuss ongoing challenges and open research questions in this area.

Multi-Objective Co-Optimization of FlexRay-Based Distributed Control Systems

Abstract: Recently, research on control and architecture co- design has been drawing increasingly more attention. This is because these techniques integrate the design of the controllers and the architecture and explore the characteristics on both sides to achieve more efficient design of embedded control systems. However, there still exist several challenges like the large design space and inadequate trade-off opportunities for different objectives like control performance and resource utilization. In this paper, we propose a co-optimization approach for FlexRay-based distributed control systems, that synthesizes both the controllers and the task and communication schedules. This approach exploits some FlexRay protocol specific characteristics to reduce the complexity of the whole optimization problem. This is done by employing a customized control design and a nested two-layered optimization technique. Therefore, compared to existing methods, the proposed approach is more scalable. It also allows multi-objective optimization taking into account both the overall control performance and the bus resource utilization. This approach generates a Pareto front representing the trade-offs between these two, which allows the engineers to make suitable design choices.