Robust car steering by yaw rate control

It is shown that feedback control can improve the robustness of the driver-car system with respect to uncertain operating conditions. Robustness is achieved by controlling the yaw rate instead of the steering angle. Integrating unit feedback of the yaw rate error makes the yaw mode unobservable from the front axle lateral acceleration and thereby take uncertainty out of the steering transfer function. Rear-wheel steering allows pole placement for the yaw mode. A main result of this study is a robust compensator/actuator design for all cars and all operating conditions. A further result applies to cars with additional rear-wheel steering. This second input can be used to place yaw-mode eigenvalues in desired locations. By the decoupling property, shifting of these eigenvalues has no influence on the transfer function from the steering wheel to the lateral acceleration of the front axle