Global stabilization control of underactuated ships with input saturation

In this paper, stabilization control of an underactu-ated ship in the presence of input saturation is addressed. By introducing a virtual reference, the stabilization is transformed into a path following problem thus the error dynamics is divided into a cascade of two subsystems, and the torques in surge and yaw axis are designed separately using the backstepping technique. It is shown that the closed-loop system is stable and the mean-square errors can be made arbitrarily small by choosing design parameters. Simulation results also verify the effectiveness of the proposed scheme.