Adaptive fast nonsingular terminal sliding mode control for underactuated surface vessel trajectory tracking

In this paper, we investigate the trajectory tracking control problem for underactuated surface vessels (USVs) in the presence of time-varying disturbances with unknown upper bounds. First, in order to handle the underactuation of the USVs, we introduce a coordinate transformation to redefine the output variables of the USVs. Then, the adaptive trajectory tracking control law is proposed based on the adaptive fast nonsingular terminal sliding mode (FNTSM) control technique, where the adaptive law online provides the estimation of the parameters. It is proved that the designed control law can force the USV to track the desired trajectory and tracking errors of closed-loop system converge to zero in finite time. Simulation results on an underactuated model ship verify the effectiveness of the proposed control law.