Robust Exact-Time Trajectory Tracking Control for Autonomous Surface Vessels

In this article, we address the trajectory tracking control problem of an autonomous surface vessel with limited information about its system dynamics in the presence of bounded external disturbances. We propose nonlinear robust control strategies that guarantee the surface vessel converges to its desired path precisely at an exact time, regardless of its initial engagement geometry with respect to the path, provided it is within a feasible region respecting the physical constraints of the vehicle. Furthermore, the proposed strategy offers an appealing feature of allowing the selection of the convergence time before the start of the engagement. This provides the control designer with an additional degree of freedom to tailor the convergence time a priori according to specific mission requirements. We first provide a design using the knowledge of the upper bound of the disturbances. Later, we extend the design for unknown disturbances. Finally, numerical simulations elucidate the merits of the proposed strategy.