Fixed-time output feedback sliding mode tracking control of marine surface vessels under actuator faults with disturbance cancellation

Abstract

This paper proposes a novel fixed-time output feedback sliding mode tracking control of marine surface vessels (MSVs) under unknown external disturbances, unmeasurable velocities, unmodelled dynamics and actuator faults (AF). A fixed-time extended state observer (FXESO) is proposed to observe unknown lumped disturbances. Considering the FXESO, a novel fixed-time velocity-free fault-tolerant control law is applied to trajectory tracking based on a fixed-time non-singular fast terminal sliding mode manifold (FNFTSMM). The control scheme is able to make an MSV track a reference trajectory exactly, and the tracking errors can be stabilized to the origin in fixed time. Meanwhile, the upper bounded value of the convergence time does not depend on vessels’ initial values. Finally, simulation results and comparisons illustrate the merits of the proposed control scheme.