Integrated vehicle dynamics control using semi-active suspension and active braking systems

This article presents an integrated control of yaw, roll and vertical dynamics based on a semi-active suspension and an electronic stability control with active differential braking system. During extreme manoeuvres, the probability of vehicle rollover is increased and the stability of lateral and yaw vehicle motions is deteriorated because of the saturation of tyre forces. Furthermore, when the road excitation frequencies are equal to the natural frequencies of the unsprung masses, the resonance phenomena occurs, which causes some oscillations getting revealed on responses of the yaw and lateral vehicle dynamics. In these situations, the active braking alone cannot be helpful to improve the vehicle handling and stability, considerably. In order to overcome these difficulties, a coordinated control of the semi-active suspension and the active braking is proposed, using a fuzzy controller and an adaptive sliding mode controller, respectively. A non-linear full vehicle model with 14 degrees of freedom is established and combined with the modified Pacejka tyre model. As the majority of vehicle dynamics variables and the road profile inputs cannot be measured in a cost-efficient way, a non-linear estimator based on unscented Kalman filter is designed to estimate the entire vehicle dynamics states and the road unevenness. Simulation results of the steering manoeuvres on the random road inputs show that the proposed chassis system can effectively improve the vehicle handling, stability and ride comfort.