Research Of Nonlinear Sliding Mode Control For Underactuated Surface Vessel Trajectory Tracking

Underactuated vessels model is a multi-input, multi-output, strong coupling, nonintegrity of the nonlinear system. The ship sailing in the ocean, the ship motion disturbance caused by wind, wave, flow interference, its essence can be classified into ship model parameter perturbation, and the dynamic change of ship loading quality and the speed of the ship, causing the ship model parameter uncertainty. Because in the actual situation, the ship speed state is often difficult to measure, so the traditional control method is difficult to solve the existing problems.With more complex task requirements in the rapid development of marine and engineering system, explore new ship control method has become a hot topic in recent years.This paper mainly studies nonlinear sliding mode control for underactuated surface vessel trajectory tracking, and the main research work is as follows:(1)For underactuated ship trajectory tracking control problem with speed state unpredictable, a underactuated ship output feedback sliding mode controller based on observer is proposed.Observer is designed by using Lyapunov method and stable first, and then according to the desired trajectory combined with the actual location information, kinematics loop virtual speed control law is designed, through the stabilization of speed error to achieve stabilization of the tracking error. In the dynamic loop designing first and second order sliding mode surface, thrust and stem torque sliding mode control law is obtained by exponential reaching law, and by using Lyapunov method for system stability analysis.(2) For model parameter uncertainty and external disturbance of the underactuated ship trajectory tracking problem, a RBF neural network adaptive sliding mode controller is proposed.The interference is regarded as model parameter uncertainty, using the features of RBF neural network which can approximate arbitrary function to estimate the unknown parameters of ship model.According to the desired trajectory combined with the actual location information, kinematics loop virtual speed control law is designed, through the stabilization of speed error to achieve stabilization of the tracking error. In the dynamic loop designing first and second order sliding mode surface, thrust and stem torque adaptive sliding mode control law is obtained by exponential reaching law, and by using Lyapunov method for system stability analysis.(3)For the above about design of output feedback sliding mode controller and RBF neural network adaptive sliding mode controller of underactuated vessels have been vertified by simulation. The final simulation results show that all controllers designed in this paper can make the ship accurately track the desired trajectory, to verify the effectiveness of the control algorithm.