Path Following Control For Underactuated Ship Based On Second Order Sliding Mode

With the rapid development of the global economy,the surface underactuated ships,as the main means of transportation for trade between countries,have been widely concerned by countries from all over the world.In order to ensure that the underactuated ship can success-fully complete all kinds of designated navigation tasks,the realization of path following control has become a research hotspot.However,considering the strong nonlinear and coupling characteristics of the underactuated ship in the process of operation,the traditional control method has been unable to meet its accuracy requirements.Therefore,seeking effective control strategy is the key to solve the problem of path following control.This paper mainly focuses on the research of the path following control strategy for surface underactuated ship,the main research work is as follows:Firstly,the paper introduces the kinematics and dynamic mathematical model of the un-deractuated ship,on this basis,the model was simplified according to the research content of this paper.Eventually,the mathematical model of the underactu ated ship with three degrees of freedom in horizontal plane was obtained.Secondly the chattering problem in the sliding mode control method was addressed,and for effectively suppress chattering and improve the tracking control accuracy of the system,the path following controller of underactuated ships was de-signed by using Super-Twisting second order sliding mode.Thirdly,it was difficult to obtain the boundary value of the complex and variable disturbance at sea,which makes it difficult to select the controller parameters.For solving the problem,a path following control strategy based on adaptive second-order sliding mode was proposed.In this method,adaptive control was used to realize the real-time estimation of the boundary value of external disturbance,and then the parameters of the controller were updated so that can get the better control effect.Fi-nally,aiming at the problem of inaccurate measurement caused by external environment in-terference during the measurement process of ship speed sensor.For solving this problem,an adaptive second-order sliding mode control strategy based on extended observer was proposed.In this method the real-time estimation of the speed state information can be realized by con-structing the extended observer,so that can solve the problem of inaccurate speed measurement and realize the ship's path following control at the same time.Through corresponding simulation research on the above control strategies,the simulation results show that the controller designed in this paper have strong robustness and good dynamic control performance,and finally effectively achieves the path following control of the under-actuated ships.