Research On Trajectory Tracking Control Method Of Underactuated Unmanned Surface Vessel

In recent years,with the dramatic development of unmanned driving technology,research on underactuated unmanned surface vessels has received extensive attention in both military and civilian fields.By carrying different devices,underactuated unmanned surface vessels can accomplish tasks with operational risks such as vigilance patrol,marine environment inspection,resource survey and water search.Trajectory tracking control is the core to complete various operational tasks.The trajectory tracking control is the core of completing various operation tasks,and the scale of the tracking error determines the accuracy of the operation tasks and the size of the probability of accidents.Therefore,the design of a trajectory tracking controller with higher performance is important for the research of underactuated unmanned surface vessels.In this paper,the trajectory tracking control method of underactuated unmanned surface vessel is studied.Based on the six degree of freedom vessel model and the environmental wind,wave and current model,a simplified three degree of freedom underactuated unmanned surface vessel kinematics and dynamics mathematical model is given.A trajectory tracking control scheme is designed with a three degree of freedom underactuated unmanned surface vessel as the control object,combined with sliding mode control theory and an observer.For the problem of unknown wind,wave and current disturbances encountered during navigation,a nonlinear disturbance observer is designed to observe the unknown environmental disturbances and compensate the disturbances with the observed values of the disturbances.For the problem of asymptotic convergence of the control law designed in the conventional sliding mode control,nonsingular terminal sliding mode control laws are designed for the surge force and the yaw moment,respectively.The nonlinear factor in the nonsingular terminal sliding mode makes the system state converge to the sliding mode surface quickly and improves the convergence speed,so that the underactuated unmanned surface vessel can complete the trajectory tracking task in a finite time.The designed nonlinear disturbance observer combined with nonsingular terminal sliding mode control scheme is verified by theoretical analysis and MATLAB numerical simulation to achieve underactuated unmanned surface vessel trajectory tracking control under external environmental disturbance.To address the problem of unavailability of position and velocity information of underactuated unmanned surface vessel due to measurement equipment malfunction,as well as the problem of external disturbances and model parameter perturbation,a nonlinear expansion state observer is designed in order to be able to obtain position and velocity information while handling disturbances.A nonsingular fast terminal sliding surface is designed to derive the control law using the error model of an underactuated unmanned surface vessel.It is verified by MATLAB numerical simulation that the nonlinear extended state observer combined with a nonsingular fast terminal sliding mode control scheme can achieve underactuated unmanned surface vessel trajectory tracking control.The designed control scheme has the advantages of suppressing disturbances,small tracking errors,small chattering of the system,and high robustness.