Coordination Control of Maneuverability and Stability for Four-Wheel-Independent-Drive EV Considering Tire Sideslip

Four-wheel-independent-drive electric vehicle (EV) can generate the active yaw moment by the differential torque to change the steering characteristics such as oversteer or understeer. However, the utilization of the same actuators implies that the stability and flexibility will interfere with each other. This article proposes a coordination control strategy to simultaneously improve the low-speed flexibility and high-speed stability of the vehicle. First, the geometry of the vehicle steering and the steady-state steering characteristics under active yaw moments are analyzed. Subsequently, a gain scheduling controller is designed to adjust the magnification of the yaw rate based on the driver’s intention. Next, a feedforward and an enhanced sliding mode controller are applied to quickly track the target motion. Due to the overlapping nature of the actuators in the differential drive-assisted steering (DDAS) and vehicle stability control (VSC) system, the coordination strategy is developed based on the phase plane theory. Moreover, a torque distribution algorithm derived from the modified extreme value method with lesser calculation is proposed. Finally, simulations and experiments under relevant conditions are conducted to verify the effectiveness and the reliability of the designed control strategy. The results suggest that the proposed strategy can significantly improve maneuverability and ensure vehicle stability.