Robust Composite Nonlinear Feedback Path-Following Control for Independently Actuated Autonomous Vehicles With Differential Steering

This paper investigates utilizing the front-wheel differential drive-assisted steering (DDAS) to achieve the path-following control for independently actuated (IA) electric autonomous ground vehicles (AGVs), in the case of the complete failure of the active front-wheel steering system. DDAS, which is generated by the differential torque between the left and right wheels of IA electric vehicles, can be utilized to actuate the front wheels as the sole steering power when the regular steering system fails, and thus avoids dangerous consequences for AGVs. As an inherent emergency measure and an active safety control method for the steering system of electric vehicles, DDAS strategy is a valuable fault-tolerant control approach against active steering system failure. To improve the transient performance of the fault-tolerant control with the DDAS, a novel multiple-disturbance observer-based composite nonlinear feedback (CNF) approach is proposed to realize the path-following control for IA AGVs considering the tire force saturations. The disturbance observer is designed to estimate the external multiple disturbances with unknown bounds. CarSim-Simulink joint simulation results indicate that the proposed controller can effectively achieve the fault-tolerant control and improve the transient performance for path following in the faulted-steering situation.