A nonlinear disturbance observer(NDO) is used to observe the uncertainties and random wave disturbances of fin stabilizer system. By selecting the design parameters, the nonlinear disturbance observer is made in exponential convergence. Subsequently, sliding backstepping controller is designed for the system with nonlinear disturbance observer. The proposed controller can guarantee the stabilization of the closed-loop system. The simulation results show that the control strategy
is effective to decrease the roll motion of fin stabilizer control system at various sea conditions of different wave direction angles and speeds, and the controller has strong robust stability to overcome the uncertainties and random wave disturbances.