Backstepping technique for tracking control of an underactuated surface vessel with unmeasured thrus

We consider in this paper the tracking control problem of an underactuated surface vessel moving on the horizontal plane. A reference feasible trajectory for the position and orientation of the surface vessel is planned so that it is consistent with vehicle dynamics. Using these reference values the dynamics of the vehicle is transformed to the error cascade structure. The proposed controller is designed using Lyapunovs direct method and the popular backstepping techniques are utilized to stabilize the above system and force the tracking error to globally exponentially stabilized to the origin. Extension to unmeasured thruster dynamics is also considered. Simulation results that validate the proposed tracking methodology are presented and discussed.