4WS and DYC coordinated control for 4WS-4WID autonomous vehicles considering tire nonlinearity

To address the issue of path tracking and stability of four wheel steering and four wheel independent drive (4WS-4WID) autonomous vehicles under extreme conditions, this paper proposes a coordinated control method for four wheel steering (4WS) and direct yaw moment control (DYC). First, a sliding mode observer (SMO) is employed to estimate lateral forces and correct the cornering stiffness, and based on model predictive control (MPC) theory, an adaptive MPC path tracking controller is designed. Then, considering the nonlinear characteristics of tires, the 4WS stability controller and DYC stability controller with nonlinear lateral force are designed by sliding mode control (SMC). On this basis, with the control objectives of sideslip angle and yaw rate, the 4WS weight and DYC weight are coordinated through an extension method to obtain the optimal rear wheel angle and additional yaw moment, ensuring stability control while reducing unnecessary energy waste. Finally, the Carsim-Simulink co-simulation tests and controller-in-the-loop experiment verify the coordinated control strategy can significantly enhance both path tracking accuracy and vehicle stability under extreme conditions.