Robust Control Study for Four-Wheel Active Steering Vehicle

Vehicle is a complex uncertain system with parameter perturbations and external disturbances; these uncertainties will easily result in the loss of vehicle driving stability. Tire cornering stiffness is a key influencing factor on maneuverability of vehicle. In order to maintain driving stability in vehicle cornering, through regarding tire cornering stiffness and outer disturbances as bounded uncertain parameters, a sliding mode controller applied to four-wheel steering vehicle is designed based on robust control theory. The dynamic simulation indicates that the sliding model controller designed not only can overcome the influence of uncertain factor on the maneuverability of 4WS vehicle and effectively prevent the loss of vehicle stability; but also ensure the steering quality of vehicle no significant change. It improves the active safety and handle ability of the 4WS vehicle during emergency obstacle avoidance and critical state accordingly.