Research On Disturbance Observer Based Robust Trajectory Tracking Control For Underactuated Surface Vessels

In order to ensure the safety of ship navigation,and improve the economic performance of ship operation.Higher level requirements for the marine cybernetics are put forward by people.For the high performance of trajectory tracking controller,not only ean avoidthe abrasion of the actuators,save the voyage and fuel,but also has strong robustness against the environmental disturbance.Since most of merchant ships are with features of underactuated constraint.Therefore,it has significant promotion on the automation of domestic ships to develop a kind of high performance controller for the underactuated ships.As one of special nonlinear system,the underactuated ship is with the characteristics of large inertia,strong coupling,nonholonomic and model uncertainty.For such complicated nonlinear systems,the difficulties of controller design not only concentrate on the nonlinearities of the system,but also the compensation of the environmental disturbance.And it is urgent to develop a kind of effective and practical control algorithm.In this paper,with consideration of model uncertainty and environmental disturbance,a novel disturbance observer based robust trajectory tracking controller is proposed for the underactuated ships.By applying the parameter estimation,the upper bound of the model uncertainty is estimated.The external disturbance is observed accurately by nonlinear disturbance observer.Then,by fusion of Backstepping and DSC technique,the result of accurate tracking for the reference path by the underactuated ship is achieved and the explosion of complexity problem is avoided.Furthermore,the GUUB stability of the closed-loop system is proved by the Lyapunov theory.Finally,by employing an underactuated surface vessel as the plant,the effectiveness and robustness of the proposed algorithm is demonstrated by the MATLAB numerical simulation.