Robust Tire Force Distribution with Velocity Suppression for Four Wheel Steering/Driving Cars

In this paper, a novel robust path tracking controller with tire distribution for 4WS/4WD vehicle is presented. The proposed control law prevents wheel force saturation by balancing four tire forces, while vehicle velocity is controlled so that it converges to the reference one as long as the required acceleration can be generated. If driving force is saturated due to high speed cornering vehicle velocity is automatically reduced by active control of lateral forces so that required centripetal force is decreased. Thus, the proposed method suppresses the vehicle trajectory deviation from the reference one. In addition, sliding mode controller assures the robustness with respect to the uncertainty of cornering power or road friction coefficient. Both tracking performance and robustness of the proposed method are shown through simulations.