FxTESO based adaptive sliding mode control for dynamic positioning vessels with uncertainties and unknown disturbances

This paper develops a novel fixed-time control scheme for dynamic positioning (DP) ships to address the critical challenges of system uncertainties and time-varying disturbances. The proposed fixed-time extended state observer (FxTESO) provides accurate estimation of unmeasurable velocities and total disturbances with convergence time independent of initial conditions, overcoming limitations of asymptotic observers. The proposed method by uniquely combining adaptive sliding mode control (ASMC) with dynamic surface control (DSC), employing an integral-enhanced sliding mode surface to eliminate chattering while ensuring computational efficiency. Furthermore, a saturation compensation strategy is introduced to address input constraints (IC). The stability of the proposed methodology is proven using the Lyapunov theory, ensuring that all state errors are uniformly ultimately bounded (UUB). Simulation results demonstrate the effectiveness and superiority of the proposed method.