Fixed-time velocity-free sliding mode tracking control for marine surface vessels with uncertainties and unknown actuator faults

In this paper, a novel fixed-time fault-tolerant control scheme is proposed for trajectory tracking of marine surface vessels (MSVs). A fixed-time extended state observer (FXESO) is developed to enhance the robustness. In conjunction with the FXESO, a fixed-time sliding mode control (FXSMC) law is applied to trajectory tracking control. The designed tracking control system can be stabilized to the origin in fixed time in the presence of actuator faults (AF), unmodelled dynamics, unmeasurable system states and exogenous disturbances. Specially, the convergence time of the system is independent of the initial states of an MSV. Meanwhile, a complete proof of closed-loop fixed-time stability is given. Finally, comparative simulations manifest the performance and advantage of the developed fixed-time control method.