Ship Adaptive Course Keeping Control With Nonlinear Disturbance Observer

This paper investigates a scheme to reject the unknown bounded time varying external disturbance for a ship course keeping control system. A mathematical model of a steering system is derived considering nonlinear features that could affect the control design process. The feedback linearization approach is adopted to simplify the nonlinear system. The adaptive sliding mode control algorithm and nonlinear disturbance observer method are developed for course keeping maneuvers in vessel steering and for providing robust performance for the environment disturbance and rudder dynamics. Furthermore, the overall stability conditions of the presented controllers are analyzed by Lyapunov's direct method. Finally, the effectiveness of the controllers is illustrated by the simulation results on a navy vessel with twin rudders.