Robust global asymptotic stabilization of underactuated surface vessels with parameter uncertainties

This paper investigates the position and the full-state stabilization problems of an underactuated surface vessel with parameter uncertainties. Two control schemes are proposed with the first one steering the vessel´s position and velocity to zero and the second guaranteeing the convergence of all states to zero. The controller design is based on the direct Lyapunov method, the Barbalat´s lemma and the sliding-mode technique. In both schemes, the global uniform asymptotic stability of the closed-loop system is achieved despite parameter uncertainties. The effectiveness of the proposed control laws is verified by simulation results.