Global sliding mode based trajectory tracking control for underactuated surface vessels with uncertain dynamics

A global sliding mode control scheme is proposed to force an underactuated surface vessel to track a desired trajectory, in spite of the presence of uncertain parameters and unmodelled uncertainties including external disturbances and measurement noise, etc. The effect that the rudder generates a lateral acceleration on the sway direction is considered. In this case, the system is nonminimum phase. An output redefined point p, which is placed on the ship principal symmetry axis at a distance l from the ship center of mass, is introduced to transform the nonminimum phase into a stable internal dynamic. The controller is designed by using the global sliding mode control to ensure the existence of a sliding mode throughout an entire response. The stability analysis is taken based on Lyapunov theory. Some numerical simulations are provided to validate the effectiveness of the proposed controller.