Adaptive Sliding Mode Control For Path Following Of Underactuated Ships Based On Observer

With the rapid development of control technology and the emergence of intelligent ships,the problem of underactuated ship control has attracted more and more attention.This topic combines backstepping technology,sliding mode control algorithm,extended observer,integral synoviplane,parameter adaptive method,nonlinear velocity observer and other advanced control theories,aiming to solve the problems of internal and external interference of underactuated ships.Based on the actual situation,this thesis studies the adaptive sliding path following control problem of underactuated ships,and solves the important problems of adaptive compensation,namely the model uncertainty and environmental interference of the system.The research results are mainly as follows:1.A comprehensive modeling of the underactuated ship is carried out,and the ship maneuvering motion equation is derived by a systematic method,and the motion simulation model is established.On this basis,the controller design model is completed by simplification.This thesis also describes in detail the modeling method of common natural factors such as wind,wave and current,and constructs a numerical simulation model to test the performance characteristics of control ships when they encounter the interference of natural environmental factors.2.In the problem of underactuated ship path following control,the traditional sliding film control has the defects that it takes a long time for the system state to reach the sliding mode surface,and high frequency buffeting and large amplitude occur when the system just reaches the sliding mode surface.Based on the mathematical model of ship motion,an improved approach law method is proposed,which can reduce buffeting to the maximum extent on the basis of ensuring the dynamic quality of the system.Shorten the time to reach the sliding surface.The reference heading angle is designed according to the inversion algorithm,which simplifies the controller design.The nonlinear observer is introduced to estimate the velocity which is difficult to measure and the stability of the controller is proved by means of Lyapunov stability theory.3.Considering the external disturbance of underactuated ships at sea,an adaptive sliding mode controller with velocity observer is designed based on sliding mode control and adaptive technology.In order to improve control accuracy and eliminate steady-state error,integral term is introduced into sliding surface design.The velocity which is difficult to measure is observed with an improved nonlinear velocity observer.The stability theory of Lyapunov function is used to prove that the control input obtained by the system can guarantee the fast convergence of following error in finite time.4.Finally,the Matlab/Simulink software is used to conduct simulation research on the underactuated ship,and a practice ship named "Yupeng" from Dalian Maritime University is selected as the experimental simulation object to evaluate the effect of the designed ship path following controller.According to all test data,it can be concluded that the controller proposed in this study successfully weakens the influence of ship model parameter changes and external disturbances,thus realizing the control of underactuated ship path following.