Virtual prototyping of vehicular electric steering assistance system using co-simulations
Doctoral thesis, 2021

Virtual prototyping is a practical necessity in vehicle system development. From desktop simulation to track testing, several simulation approaches, such as co-simulation and hardware-in-loop (HIL) simulation, are used. However, due to interfacing problems, the consistency of testing results may not be ensured. Correspondingly, inherent inaccuracies result from numerical coupling error and non-transparent HIL interface, which involves control tracking error, delay error, and attached hardware and noise effects. This work aims to resolve these problems and provide seamless virtual prototypes for vehicle and electric power-assisted steering (EPAS) system development.
The accuracy and stability of explicit parallel co-simulation and HIL simulation are investigated. The imperfect factors propagate in the simulation tools like perturbations, yield inaccuracy, and even instability according to system dynamics. Hence, reducing perturbations (coupling problem) and improving system robustness (architecture problem) are considered.
In the coupling problem, a delay compensation method relying on adaptive filters is developed for real-time simulation. A novel co-simulation coupling method on H-infinity synthesis is developed to improve accuracy for a wide frequency range and achieve low computational cost. In the architecture problem, a force(torque)-velocity coupling approach is employed. The application of a force (torque) variable to a component with considerable impedance, e.g., the steering rack (EPAS motor), yields a small loop gain as well as robust co-simulation and HIL simulation. On a given EPAS HIL system, an interface algorithm is developed for virtually shifting the impedance, thus enhancing system robustness.
The theoretical findings and formulated methods are tested on generic benchmarks and implemented on a vehicle-EPAS engineering case. In addition to the acceleration of simulation speed, accuracy and robustness are also improved. Consequently, consistent testing results and extended validated ranges of virtual prototypes are obtained.

explicit parallel co-simulation

Vehicle and mechatronic system

interface algorithm.

coupling method

HIL simulation

Opponent: Dipl.-Ing. Dr.techn., Georg Stettinger, Virtual Vehicle Center, Austria


Weitao Chen

Chalmers, Mechanics and Maritime Sciences, Vehicle Engineering and Autonomous Systems

Integration and Analysis of EPAS and Chassis System in FMI-based co-simulation

Proceedings of the 13th International Modelica Conference,; (2019)p. 717-724

Paper in proceeding

Real-time Co-simulation Method Study for Vehicle Steering and Chassis System

IFAC-PapersOnLine,; Vol. 51(2018)p. 273-278

Paper in proceeding

Chen W., Bruzelius F., Klomp M. and Jacobson B., A Method to Improve Stability and Transparency for Mechanical Hardware-in-the-Loop Simulation

Nowadays, vehicles have more mechatronic systems to achieve electrification and automation. To save development cost and time, most of the work relies on simulation using computers, instead of real vehicle tests. This approach refers to virtual prototyping, of which the complexity is determined by the components such as software tools and hardware devices. In a typical engineering case (e.g., vehicle and electric power assisted steering system), a virtual prototype involves several software tools to accelerate the simulation speed. Moreover, real-time performance is desired so that hardware devices can be integrated and tested together.
However, some undesired issues occur in virtual prototyping due to the integration. Numerical error is introduced by the separation of simulation tools; communication delay and noises are unavoidable in software-hardware interface; control error is incurred as well. These issues, that do not exist on a physical vehicle or in a monolithic simulation tool, can degrade the testing reliability. For example, steering vibration can occur on a vehicle-steering virtual prototype and some tests can even fail due to the interfacing problems.
To resolve the problems and develop the system in a consistent way, virtual prototypes must be built appropriately. One straightforward way is to reduce the numerical error, compensate the communication delay and noises by implementing some approximation methods that are more advanced than the default setup. The other way is to design the prototype configuration to make it more robust to the incurred problems, for example error and noise of a force variable is less sensitive to a heavier component than a lighter one. Solutions by both means are effectively implemented and increase the reliability of the prototype. This is confirmed by the eliminated vibrations caused by the tools. In addition, simulation failure in some test cases can be removed implying an extended usage of the tool.

Steer by wire Opportunities, performance and system safety (SWOPPS)

VINNOVA (2017-05504), 2018-03-09 -- 2021-07-01.

Virtual Architecture for Development and Verification of Chassis Mechatronic Systems

European Commission (EC) (675999), 2016-07-01 -- 2022-06-30.

Volvo Cars, 2016-07-01 -- 2022-06-30.

Subject Categories

Mechanical Engineering

Vehicle Engineering

Electrical Engineering, Electronic Engineering, Information Engineering

Control Engineering

Areas of Advance

Information and Communication Technology




Basic sciences

Learning and teaching

Pedagogical work



Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 4991


Chalmers University of Technology

Opponent: Dipl.-Ing. Dr.techn., Georg Stettinger, Virtual Vehicle Center, Austria

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