Way-point Tracking Control of Underactuated Ships
This chapter presents state feedback and output feedback controllers that force underactuated ships to globally ultimately track a straight line under environmental disturbances induced by waves, wind, and ocean currents. When there are no environmental disturbances, the controllers are able to drive the heading angle and cross-tracking error to zero asymptotically. Based on the backstepping technique and several technical lemmas introduced for a nonlinear system with nonvanishing disturbances, a full state feedback controller is first designed. An output feedback controller is then developed by using a nonlinear observer, which globally exponentially estimates the unmeasured sway and yaw velocities from the measured sway displacement and the measured yaw angle.
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