Global asymptotic stabilization of an underactuated surface vessel

Stablization of an underactuated surface vessel using only two available controls is a challenging problem. In most studies, it can be solved with persistent angular excitation, which can be well achieved by time-varying feedback control. But the Lyapunov function of time-varying system is rather difficult to choose. In this paper, a new time-varying state transformation is proposed, and a time-varying Lyapunov function can be easily to constructed to design a stabilization control law based on backstepping approach. Simulation results are provided to validate the theoretical results.