Fault Tolerant Control of a 4 Wheels Driven Steer by Wire Electric Vehicle: Case of Active Front Steering Faults

This paper presents an Active Fault-Tolerant Control strategy for a four-wheel-drive electric vehicle equipped with in-wheel motors and a Steer-by-Wire system with Active Front Steering. A nonlinear full-vehicle dynamic model is developed, incorporating vertical, lateral, longitudinal, wheel, and tire-road interaction dynamics. A multi-layer Global Chassis Control architecture is designed to simultaneously ensure vehicle stability, maneuverability, and trajectory tracking performance. At the control layer, a Super-Twisting Sliding Mode Controller is implemented for yaw rate and side-slip angle regulation, coordinated via a stability index-based decision mechanism. Steering actuator faults are modeled as both Loss-of-Effectiveness and additive faults. An adaptive observer is proposed for real-time estimation of fault parameters and fault-type identification using residualbased evaluation functions. The proposed AFTC scheme is experimentally validated through single-lane-change maneuvers under varying fault magnitudes. Experimental results demonstrate robust fault detection capability, accurate fault magnitude estimation, and effective maintenance of vehicle stability, even under severe actuator degradations.