High-Accuracy Trajectory Tracking Control Of Underactuated Surface Vehicles

Underactuated surface vehicle(USV)is driven by the propeller thrust and yaw moment,due to the input number of the control system is less than the number of degrees of freedom,and motion control system of an USV cannot be converted to a drift-less system.Therefore,the USV belong to a class of particular nonholonomic systems,it is more difficult to control than that of general underactuated mechanical system.Besides,the navigation of ships in the ocean is very easy to be interfered by the marine environment such as wind,wave and current.This undoubtedly increases the difficulty of motion control for an USV.With the development of society,people's demand for USV is increasing.They are mainly applied to military,marine transportation,marine development and so on.The motion control of an USV has received extensive attention.To sum up,it is of great significance for the research of USV.For the motion control system of USV,combined with dynamic surface control(DSC)and finite time disturbance observer,we study on the tracking control problem of USV.The main work done in this paper is as follows:Firstly,a DSC based trajectory tracking control scheme for an USV is proposed.Control laws for two independent inputs of the USV are designed subsequently within the scheme by utilizing the structure of tracking error dynamics.The DSC approach is incorporated into the backstepping technique to avoid differentiation of intermediate virtual signals and circumvent the curse of dimension,thereby resulting in global asymptotically stable.Simulation studies demonstrate that the proposed DSC scheme is effective and efficient.Then,the trajectory tracking control problem of an USV with input saturation is solved by combining with DSC approach and input saturation auxiliary design system.The tracking error system is transformed into a cascaded form with driving and driven subsystems,we can design controller for the two subsystem separately using DSC approach and an auxiliary design system is used to deal with input saturation of control input.Finally,the trajectory tracking control problem of USV which lacks an independent actuator in the sway axis with unknown disturbances.The tracking error system can be viewed as a cascaded structure consisting of two subsystems,the DSC approach is employed to stabilize the two subsystems separately and the unknown disturbances are addressed by finite-time disturbance observer.The DSC approach is incorporated into the backstepping technique to avoid differentiation of intermediate virtual signals and circumvent the curse of dimension.Combined with the cascaded theory,we can prove that the tracking error can converge to zero asymptotically.Simulation studies demonstrate that the proposed scheme is effective and efficient.