A MPC based Cooperated Control Strategy for Enhanced Agility and Stability of Four-Wheel Steering and Drive Electric Vehicles

Multiple actuators equipped in electric vehicles, such as four- wheel steering (4WS) and four-wheel drive (4WD), provide more degrees of freedom for chassis motion control. However, developing independent control strategies for distinct actuator types could result in control conflicts, potentially degrading the vehicle's motion performance. To address this issue, a model predictive control (MPC) based steering-drive cooperated control strategy for enhanced agility and stability of electric vehicles with 4WD and 4WS is proposed in this paper. By designing the control constraints within the MPC framework, the strategy enables single-drive control, single-steering control, and steering-drive cooperative control. In the upper control layer, a linear time-varying MPC (LTV-MPC) is designed to generate optimal additional yaw moment and additional steering angles of front and rear wheels to enhance vehicle agility and lateral stability. In the lower control layer, a linear MPC (LMPC) based torque vectoring optimization allocation strategy is implemented to track the desired additional yaw moment. Furthermore, tire slip ratios are taken into account within this layer to enhance vehicle longitudinal stability. Hardware-in-the-loop (HIL) experiments are conducted under diverse test conditions to assess the proposed cooperated control strategy. The results indicate that steering-drive cooperated control strategy can simultaneously enhance vehicle agility and stability performance compared to single-drive control and single-steering control.