Integrated rear wheel steering angle and yaw moment optimal control of four-wheel-steering vehicle

In order to solve the problem of excessive understeer of four-wheel -steering vehicle with zero mass-center side-slip angle and proportional control at high speed, adding direct yaw moment control to the proportional control of four wheel steering, a two DOF (degree of freedom) four-wheel-steering vehicle model with integrated control of steering angle and yaw moment was established. The control objective that side-slip angle and yaw rate have the best performance was settled. An integrated optimal control system was designed using feed forward and state feedback which are based on the servo tracking optimal control theory. Using Matlab/Simulink, control model was built and simulation of it was carried out. The simulation results show that the integrated optimal control method can improve vehicle handling stability effectively and doesn´t increase the driver´s driving burden at the same time.