Active Fault Tolerant Decentralized Control Strategy for an Autonomous 2WS4WD Electrical Vehicle Path Tracking

This paper presents an active fault tolerant control (AFTC) strategy for preserving the path tracking for an autonomous 2 wheel-steering 4 wheel-driving (2WS4WD) electrical vehicle in the presence of an actuator fault. It is based on a decentralized fault tolerant control strategy for overactuated systems. The strategy consists of generating new REFERENCEs for redundant actuators, which are only used when faults are detected, and tracking these REFERENCEs. For a 2WS4WD vehicle, five actuators are used in normal situations to ensure the vehicle path tracking: the front-wheel steering actuator and the four traction actuators. However, in faulty situations, the vehicle's rear-wheel steering actuator is controlled in order to preserve the system's path tracking and to ensure the desired performance. The elaborated control law that is used to control the rear-wheels steering system is composed of 2 interconnected control loops: an outer loop and an inner loop. This decentralized control strategy tolerates the traction and the front-wheel steering actuator faults. The main advantage of the proposed fault tolerant strategy is that the faults can be compensated by computing online new REFERENCEs for the control loops without changing the initial controllers. This strategy provides the necessary time for a diagnosis system to precisely isolate the faulty actuator. This method is tested and validated on a realistic vehicle dynamic model co-simulated using CarSim and Matlab-Simulink softwares.