Sliding mode control of AFS+ARS+DYC for the yaw stability of a 4WIS-4WID vehicle

The active front steering and active rear steering (AFS+ARS) controllers, the direct yaw-moment controllers (DYCs) for yaw rate and sideslip angle are designed for a four-wheel independent steering, four-wheel independent drive (4WIS-4WID) vehicle by applying the theory of slide-mode variable structure control. For coordinating the coupling between yaw rate and sideslip angle, a coordinated controller is designed and a wheel drive/brake co-distribution is implemented for additional yaw moment. Then a 2 DOF 4WIS-4WID vehicle reference model is introduced with its yaw rate and sideslip angle state variables fed back to AFS+ARS controller to complete AFS+ARS and DYC control system integration. Finally with vehicle uncertain parameters and gust disturbance added, the control strategy is applied to a 16-DOF 4WIS-4WID vehicle model to conduct simulation verification and comparison with AFS+ARS and DYCs for conventional PID and differential braking. The results show that the control strategy designed improves both the disturbance resistance and accuracy of system, expands the stable region of system and further enhances the active safety of vehicle.