Nonlinear tracking control of underactuated surface vessel

We consider in this paper the tracking control problem of an underactuated surface vessel. Based on the cascaded structure of tracking error dynamics, we present two new tracking controllers using Barbalat´s lemma and back-stepping techniques under mild assumptions on the reference trajectory. The closed-loop systems achieve global asymptotical and exponential tracking respectively. Simulation results show that the proposed control laws are effective.