IJCAS

In this paper, we address the problem of course-tracking for ships with unknown time-varying parameters, completely unknown time-varying control coefficient, and unknown time-varying bounded environmental disturbances. Incorporating a Nussbaum function and an adaptive law into the backstepping design method, we propose a course-tracking control law. The strict stability analysis shows that the designed course-tracking control law makes the course-tracking error settle into an arbitrarily small compact and guarantees the global uniform ultimate boundedness of all signals of the resulting closed-loop system by appropriately choosing design parameters. Simulation results and simulation comparisons on two ships demonstrate the effectiveness and the superiority of the proposed course-tracking control law.

Keywords: Adaptive robust control, backstepping, course-tracking of ships, Nussbaum function, unknown disturbances, unknown time-varying parameters.