On path following of underactuated surface ships

In this paper, a hybrid solution is proposed for motion control of underactuated surface ships with actuator constraints and unknown disturbances. It combines backstepping method with Active Disturbance Rejection Control (ADRC) and sliding mode control (SMC) to form an effective and robust control structure. A coordinate transformation of nonlinear equation is introduced to steer the ship to follow the desired path. The cross track error caused by wind and current is removed via active disturbance rejection, in conjunction with the SMC based control law. Simulations were performed on a nonlinear kinematics model of a training ship to validate the stability and robustness of the proposed path following controller.