Abstract: In practice, vehicles always undertake different loadings and have velocity variation because of braking/ accelerating. Under of the yaw-rate tracking feedback control logic, a μ synthesis robust controller is designed with the optimized weighting functions to attenuate the external disturbances. The controller is provided with better performance for whole closed-loop controlled 4WS (Four-wheel steering)vehicle comparing the arrived by the normal 4WS controller designed by old techniques. The results show that the 4WS vehicle with μ synthesis robust controller not only has greater maneuverability and robust performance but also has the strong ability to resist the disturbance, and it is not sensitive to the variation of vehicle parameters. The controller also improves the disadvantage for the H∞ controller which normally is conservative about the disturbance resistance.

Key words: Four-wheel steering, Robust control, Yaw-rate, μsynthesis