Fault-Tolerant Control for 4WID/4WIS Electric Vehicle Based on EKF and SMC

This paper presents a fault-tolerant control (FTC) algorithm for four-wheel independently driven and steered (4WID/4WIS) electric vehicle. The Extended Kalman Filter (EKF) algorithm is utilized in the fault detection (FD) module so as to estimate the in-wheel motor parameters, which could detect parameter variations caused by in-wheel motor fault. A motion controller based on sliding mode control (SMC) is able to compute the generalized forces/moments to follow the desired vehicle motion. By considering the tire adhesive limits, a reconfigurable control allocator optimally distributes the generalized forces/moments among healthy actuators so as to minimize the tire workloads once the actuator fault is detected. An actuator controller calculates the driving torques of the in-wheel motors and steering angles of the wheels in order to finally achieve the distributed tire forces. If one or more in-wheel motors lose efficacy, the FD module diagnoses the actuator failures first. Then the reconfigurable control allocator accommodates faulty in-wheel motors and reconfigures the control allocation law of the healthy motors to achieve the desired vehicle motion to the greatest extent. Experimental verification is made to show that the proposed FTC algorithm is able to improve the vehicle's stability and handling performance in various driving scenarios.