Abstract
KEYWORDS–Four wheel independent steering (4WIS); Steering mode switching; Perturbation suppression; synthesis control; Robustness
ABSTRACT–Various steering modes can be easily achieved in steer-by-wire 4WIS electric vehicle, including front wheel steering (FWS), rear wheel steering (RWS), four wheel steering (4WS), pivot steering and so on. In order to achieve steering mode switching without parking, a steer-by-wire 4WIS prototype electric vehicle is manufactured and different controllers are designed. In controller design, the sideslip angle and yaw rate of steady state in two steering modes are viewed as known conditions, the ideal sideslip angle and yaw rate in the process of steering mode switching are fitted by polynomial, then the controller is designed to track ideal sideslip angle and yaw rate. As to nominal model, simulation results show that optimal controller has better performance than PID and robust controllers. Furthermore, simulations for synthesis robust controller are implemented to compare the vehicle performance under different perturbations of tire cornering stiffness and longitudinal velocity, and simulation results show that the designed synthesis robust controller has good tracking ability, strong robust stability and good robust performance against different perturbations.