Research On Trajectory Tracking Control Strategy Of Unmanned Surface Vehicles

In recent years,with the continuous development of society,people's demand for all kinds of natural resources increased dramatically,and the output of land resources has gradually been unable to meet such demand,so countries turned their attention to marine resources.In the process of exploration and development of marine resources,unmanned surface vehicles(USVs)has been widely used because of its flexibility,high autonomy and strong expansibility.At present,improving the autonomy of the system is the development trend of USVs,so we must make breakthroughs in communication,intelligent decision-making and trajectory tracking control.Among them,accurate and reliable trajectory tracking control can ensure USVs to navigate along the desired trajectory,and provide basic guarantee for its efficient completion of various tasks.Therefore,the trajectory tracking control of USVs has important research value.This thesis focuses on the research of the trajectory tracking control of USVs,and the main contents are as follows:1.The dynamic characteristics of the USVs are introduced from the aspects of kinematics and kinetics.Combining with the designing requirements of trajectory tracking controller,a 3-degree-of-freedom(sway,yaw,row)motion model for underactuated USVs is established.In this thesis,the neural dynamic model is an indispensable part,so it is introduced.2.Combining with a kind of neural dynamic model,a sliding mode trajectory tracking controller for USVs based on the variable boundary layer is designed.The designing of the controller is divided into kinematics loop and kinetics loop.In the kinematics loop,virtual speed control laws are designed according to position error by using tanh function,and two neural dynamic models are introduced to deal with the virtual control laws,so as to reduce the calculation complexity of the controller,furthermore,the smooth and bounded of the virtual control laws are ensured.In the kinetics loop,according to the outputs of neural dynamic models,the actual control laws of the trajectory tracking control system are designed.In the process of designing the control laws,saturation functions with variable boundary layers are used,the boundary layers of the saturation functions could change with system control errors.Finally,the stability of the system is proved by theoretical analysis,and the effectiveness of the controller design method is verified by numerical simulation.3.A backstepping trajectory tracking controller for USVs based on disturbance observer is designed.The designing of the controller is divided into kinematics loop and kinetics loop too.In the kinematics loop,the position errors under inertial coordinate system are changed to the hull coordinate system by differential homeomorphism transformation.In order to improve the tracking accuracy and dynamic performance of the system,the integral terms of position errors are introduced to design the virtual speed control laws.In addition,for avoiding differential explosion and make the virtual speeds smooth and bounded,the neural dynamic models are used to control the virtual speed laws.In the kinetics loop,the actual control laws of the system are designed according to Lyapunov functions.By using the observation values of disturbance observer to carry out feedforward compensation for the control variables,the anti-disturbance ability of the trajectory tracking controller for USVs is improved.Finally,the Lyapunov function is constructed to analyze the stability of the system,and the effectiveness of the controller design method is analyzed by numerical simulation.