Research on hierarchical control of vehicle yaw stability with rear-wheel steer-by-wire considering angle tracking

Rear-wheel steering-by-wire (RSBW) vehicles improve vehicle safety by controlling the rear-wheel actively. However, vehicle states are affected by nonlinear dynamics. In order to improve vehicle yaw stability and realize active rear-wheel steering, a hierarchical controller for RSBW vehicles is proposed. It consists of an adaptive terminal sliding mode controller (ATSMC) for the desired sideslip angle tracking as well as yaw rate tracking, and a linear active disturbance rejection controller (LADRC) for steering angle tracking. First, two degrees of freedom vehicle model with nonlinear tire model is adopted to describe the vehicle dynamics. And a dynamic model of the RSBW system considering time-belt transmission characteristics is established. Second, an adaptive law and an integral term are incorporated into the ATSMC to enhance its robustness and convergence rate. And a linear extended state observer (LESO) is utilized to estimate extended states of the RSBW system and realize control compensation, ensuring the angle tracking accuracy and anti-interference capability. Finally, Simulink and Carsim co-simulation and hard-ware-in-loop simulation are conducted to compare different controller. The results indicate that the proposed controller can track the desired states, and have a better performance improving the yaw stability of RSBW vehicles and reduce tracking error of the rear-wheel steer angle.