Co-Simulation in Virtual Verification of Vehicles with Mechatronic Systems

Licentiate thesis, 2019

In virtual verification of vehicle and mechatronic systems, a mixture of subsystems are integrated numerically in an offline simulation or integrated physically in a hardware-in-loop (HIL) simulation. This heterogeneous engineering approach is crucial for system-level development and widely spreads with the industrial standard, e.g. Functional Mock-Up Interface (FMI) standard.
For the engineers, not only the local subsystem and solver should be known, but also the global coupled dynamic system and its coupling effect need to be understood. Both the local and global factors influence the stability, accuracy, numerical efficiency and further on the real-time simulation capability.
In this thesis, the explicit parallel co-simulation, which is the most common and closest to the integration with a physical system, is investigated.
In the vehicle development, the vehicle and the mechatronic system, e.g. an Electrcial Power Assisted Steering (EPAS) system can be simulated more
efficiently by a tailored solver and communicative step. The accuracy and numerical stability problem, which highly depends on the interface dynamics, can be investigated similarly in the linear robust control framework. The vehicle-mechatronic system should be coupled to give a smaller loop gain for robustness and stability. Physically, it indicates that the splitting part should be less stiff and the force or torque variable should be applied towards
the part with a higher impedance in the force-displacement coupling. Furthermore, to compensate the troublesome low-passed and delay effect from
the coupling, a new coupling method based on H∞ synthesis is developed, which can improve the accuracy of co-simulation. The method shows robustness to the system dynamics, which makes it more applicable for a complex vehicle-mechatronic system.