Terminal Sliding Mode Fault Tolerant Control for Autonomous Underwater Vehicles

This paper investigates a fault tolerant control (FTC) scheme based on terminal sliding mode technology for autonomous underwater vehicle (AUV) in the presence of modelling uncertainty, ocean current disturbance and unknown thruster faults. Firstly, a thruster fault diagnosis method is proposed, which includes two modules of fault detection and fault estimation. Observers are used both in the two modules, and for accurate thruster fault reconstruction, the fault identification scheme is proposed to estimate the thruster fault effect by introducing an intermediate variable. Then, a fault tolerant controller is proposed based on terminal sliding mode control technique, which guarantees that the trajectory tracking errors of AUV is asymptotically stable subject to thruster fault. Finally, results from simulations are presented to verify the effectiveness of the proposed active fault tolerant control method for different kinds of desired trajectories and multiple types of thruster faults.