Hardware-In-The-Loop Simulation with Extended Physical Tire Models for Virtual Testing of Control Units

Hardware-in-the-loop (HIL) simulation has been an integral part of automotive control unit development for many years. Due to the fact that real controllers are tested, the guaranteed real-time capability of the simulation environment represents a prerequisite for HIL simulation. For this reason, mainly basic, empirical tire models are used in HIL simulation so far, for example based on the Magic Formula of PACEJKA. Although those basic models deliver particularly short computing times, they reach their limits both in certain vehicle dynamics situations and with specific types of tires.
This article therefore illustrates the use of the real-time capable physical tire model CDTire/Realtime combined with the open integration and test platform CarMaker on a HIL system to test a brake controller. With this approach, the simulation of several use cases modeling specific vehicle dynamics situations on the HIL test bench becomes possible. The first use case presented is ABS controlled braking on an uneven road. The entire tire is subjected to vibration, although the circumferential vibrations of the belt are not taken into account with basic models. The impacts of these vibrations on the simulation results are discussed. Another possible use case is the sudden loss of pressure in a tire and the resulting ESC control intervention. This application is entirely new in HIL testing of ESC control units, since the loss of pressure could not be modeled with basic tire models until now.
In the future, the applications shown will continue to enable testing of controllers in the HIL network with tires that previously could only be simulated to a limited extend with basic tire models. One example are tractor tires, whose complex vibration behavior has a significant impact on vehicle dynamics. Similar tires are used on numerous other off-highway vehicles as well. The results indicate that the use of virtual prototypes is possible throughout the entire development process.