Coordinated active steering and four-wheel independently driving/braking control with control allocation
This paper presents a hierarchical coordinated control algorithm for integrating active front steering and four-wheel independently driving/braking control. In the higher-level controller, an adaptive siding mode control law and a coordination law for adjusting the yaw rate and slip angle control priorities are applied to determine the desired front wheel steering angle and external yaw moment. In the lower-level controller, a control allocation algorithm with actuators and tire forces constraint considerations is designed to assign the desired yaw moment to the front wheel steering system and four wheels. The weighting factors of tracking errors and control inputs in the cost function are online updated according to the vehicle stability index. Simulation results with a high-fidelity, CarSim, full-vehicle model show that handling and stability of the vehicle can be improved with the proposed controller. What is more, control of sideslip angle can be more focused when the vehicle is hitting the manoeuvring limitation.