Fault-tolerant control of FWIA electric ground vehicles with differential drive assisted steering

This paper investigates a novel fault-tolerant control approach against active steering system failure based on differential drive assisted steering (DDAS) on four-wheel independently actuated (FWIA) electric ground vehicles. The front-wheel steering angle can be generated with the front-wheel differential driving torque when the steering motor fails. DDAS being the only steering power source is a potential alternative to replace the regular steering system in defective situation. On this issue, this paper deploys a hierarchical control method to utilize DDAS for automatic steering. The higher-level controller is dedicated to generate the desired control input including the yaw moments based on a robust LQR approach, and the lower-level controller is responsible for control allocation and giving out the respective desired tire forces and the desired steering angle. Simulation based on a high-fidelity and full-car model indicates that DDAS-based fault-tolerant control design for FWIA electric vehicle is effective to achieve equal handling and maneuverability performance in case of the steering failure.