Robust finite-time fault-tolerant control for dynamic positioning of ships via nonsingular fast integral terminal sliding mode control

A passive sliding-mode fault-tolerant control (FTC) scheme is developed in this paper for the dynamic positioning (DP) of ships to guarantee closed-loop finite-time stability in the presence of an actuator fault, a parameter uncertainty in the system and an unknown external disturbance. First, a novel nonsingular fast integral terminal sliding mode (NFITSM) which has more faster convergence rate and less chattering behavior is proposed to eliminate the singularity completely. Second, by integrating the proposed NFITSM and finite-time stability theory, a passive fault-tolerant controller is developed. Based on Lyapunov stability theory, global finite-time convergence of sliding mode and tracking errors is proved. A novel adaptive law is proposed to cope with real sliding mode constraints. Finally, the results of numerical simulation show that the proposed fault-tolerant controller successfully achieves good performance.