Trajectory tracking control of underactuated surface vessel with output tracking error constraints

This paper studies the tracking control problem for underactuated surface vessel with unknown time-varying disturbances. To avoid the controller singularity problem, the constraints on output tracking errors of underactuated surface vessel are enforced in the control design. With the help of error transformation functions, the constrained tracking control of the vessel is converted into the stabilization of the transformed error systems. To compensate for the effect of the external disturbances, disturbance observers are presented to estimate the unknown time-varying disturbances. Subsequently, disturbance-observer-based tracking control is developed to steer the vessel along a desired reference trajectory with guaranteeing the tracking errors within certain predefined bounds. The performance of the proposed tracking control is demonstrated through simulation results.