Four-Wheel Independent Drive Electric Vehicle Stability Control Using Novel Adaptive Sliding Mode Control

Four-wheel independent drive is an important research topic for the future development of pure electric vehicles (EVs) due to its fast response and great flexibility of path tracking. One of the critical issues is to maintain the vehicle motion stability of the four-wheel independent drive (4WID) EV (4WID EV) by appropriately distributing the torque of each wheel. The article presents a hierarchical control structure to counteract the stability problems caused by the actuator faults and road friction uncertainties. Instead of using linear control at the top-level (i.e., the outer control loop), a novel sliding mode controller with adaptive proportional-integral (PI) sliding surface is designed to achieve the required virtual control signal. For the bottom-level controller (or the inner loop controller), dynamic control allocation is employed to optimally allocate the required actual torque for each wheel. The stability of the overall closed-loop system is successfully achieved and proved by using the Lyapunov method. The proposed controller has been tested via simulation and experiments with various actuator faults and road conditions. All the test cases showed the superiority of the proposed method compared to some of the currently existing 4WID control strategies.