Tracking Control of Underactuated Surface Ships: Using Unscented Kalman Filter to Estimate the Uncertain Parameters

This paper proposes an unscented Kalman filter (UKF) based tracking controller to force underactuated nonlinear autonomous ships to follow a reference path under constant disturbances induced by wave, wind and ocean-current. The controller development is based on UKF and backstepping techniques. The UKF is used to update the estimation of the uncertain parameters online to avoid the parameters' drift due to time-varying added mass matrices. Along the way of tracking control, we obtain a new stability result for nonlinear underactuated systems with non-vanishing uncertainties. Simulations conducted with respect to the tracking control of unmanned ship illustrate the effectiveness of our proposed controller.