Fixed-Time Non-Singular Terminal Sliding Mode Trajectory Tracking Control for Underactuated USV

This article addresses the trajectory tracking control problem of an underactuated unmanned surface vessel (USV) in the presence of external disturbances, model uncertainties, and unmeasurable velocities. First, the mathematical model of the underactuated USV is reformulated using the hand-position approach. Then, a fixed-time extended state observer(FTESO) is designed to estimate both the unknown velocities and disturbances. Following this, a non-segmented fixed-time non-singular terminal sliding mode controller (NFTNTSMC) is developed, guaranteeing that the tracking error converges to zero within a fixed time. The stability and fixed-time convergence of the system are rigorously proven via the Lyapunov method. Ultimately, numerical simulations are conducted to assess the effectiveness and reliability of the proposed control strategy.