A Fault-Tolerant Control Method for 4WIS/4WID Electric Vehicles Based on Reconfigurable Control Allocation

This paper presents a fault-tolerant control (FTC) method for four-wheel independently driven and steered (4WIS/4WID) electric vehicles based on a reconfigurable control allocation to increase the flexibility for vehicle control and improve the safety of vehicle after the steering actuator fails. The proposed fault tolerant control method consists of the following three parts: 1) a fault detection and diagnosis (FDD) module that monitors vehicle steering condition, detects and diagnoses actuator failures; 2) an upper controller that computes the generalized forces/moments to track the desired vehicle motion and trajectory; 3) a reconfigurable control allocator that optimally distributes the generalized forces/moments to four wheels. The FTC approach based on the reconfigurable control allocation reallocates the generalized forces/moments among healthy steering actuators and driving motors once the actuator failures is detected. If one of the steering actuators fails (the road wheel cannot steer), the FDD module will diagnose the actuator failures by the steering wheel angle sensors. Then the reconfigurable control allocator accommodates faulty driving motors and reconfigures the control allocation law of the healthy motors to achieve the desired vehicle motion, maximize the vehicle-road grip margin and minimize the deviation from the desired trajectory to the utmost extent. Simulations using a high-fidelity, full-vehicle model have been conducted to verify the proposed algorithm. It has been shown from the simulations that the proposed fault-tolerant control (FTC) method can make the vehicle track the desired motion and trajectory when the steering actuator failure occurs so that it can improve the safety and maneuverability of vehicle.