Path Following Control Research Of USV Based On Disturbance Compensation

With the continuous development of marine science and technology,the research of the surface unmanned vehicles(USV)has received more and more attention.Achieve rapid and high precision of path following control is the basis of complete USV strategic and tactical goals under the premise of safe navigation in the complex ocean environment.In this paper,based on the research and reference of domestic and foreign research results,aiming at the USV path following control problem with unknown environmental disturbance,a USV path following robust controller has been designed based on the Serret-Frenet coordinate frame.The effectiveness of the method is verified by simulation.The main work of this paper is organized as follows:1,A three-DOF ship mathematical model for USV is established,including mathematical model of environmental disturbances such as wind,wave and flow.First of all,two kinds of reference coordinate system,north east coordinate system and hull coordinate system are established to analyze the characteristics of ship motion.Secondly,the kinematics and dynamics characteristics of the ship are analyzed respectively to establish the ship mathematical model of USV.Then,wind,wave and current mathematical model is given.Finally,the open-loop simulation is carried out to verify the correctness of the mathematical model of ships.2,The USV path following control algorithm which is not constrained by the path shape is studied.The position error mathematical model of USV path tracking is established by combining the traditional line-of-sight(LOS)guidance and SF differential coordinate framework.A guidance control system is designed by inputting the tangential velocity of the desired path as the virtual control rate and the position error is converged by controlling the direction.The design of path following controller is simplified and complex model conversion is avoided.Then,according to the expectation direction given by the guidance,exponential convergence disturbance observer is used to estimate the external environment disturbance online.By introducing the feedforward compensation signal into the controller,the directional controller and the longitudinal propulsion controller are respectively designed.Finally,the simulation verifies the effectiveness and robustness of the path following control algorithm based on SFLOS.3,A path following control algorithm of integral LOS guidance(ILOS)is designed to compensate the large lateral drift under the action of ocean current.Firstly,a mathematical model of the relative velocity of USV with ocean currents is established.An adaptive disturbance observer is designed for the ocean current by introducing an integral term in the guide to compensating the ocean current.Secondly,the second-order perturbation observer is used to obtain the first and second order derivatives of the expected heading angle to avoid the "integral explosion" problem of the back-stepping method,simplifying the analytic form of the controller and facilitating the realization of the project.The simulation results show that the USV path following controller based on ILOS guidance can effectively improve the tracking accuracy and reduce the lateral position tracking error.4,A USV neural network adaptive path following controller is designed based on the integral guidance algorithm with the uncertainty of the model and the unknown disturbance.USV path following control is realized by using the nonlinear approximation property of RBF neural network and the simulation verified the validity.