Design of variable structure controller for active steering vehicle

In order to improve the safety of vehicle during emergency obstacle avoidance and critical state, sliding mode variable structure control strategy was studied for active four-wheel steering vehicle based on steer-by-wire technology. A variable structure controller was designed for active steering vehicle, the cornering stiffnesses of the front and rear tires and the outer disturbance of an actual vehicle were treated as uncertain parameters, but their variances were in limited ranges, and a certain linearity vehicle model with certain parameters was taken as an ideal following goal. Based on driver-vehicle-road closed loop system, simulation result indicates that four-wheel steering vehicle with variable structure controller can maintain near zero sideslip angle and desired yaw rate, and its path errors are only 0 m and 0.05 m after changing line. Obviously, the controlled vehicle system behaves favorable performance for following path and robustness for uncertainty, its handleability and active safety are improved.