Path Following Control Method For USV Based On Improved LOS Guidance Law And ESO Sideslip Angle Estimation

As a kind of unmanned marine intelligent delivery platform,USV(Unmanned Surface Vehicles)can undertake long-term,large-scale,low-cost marine scientific research and engineering tasks in the ocean,and has a broad application prospect.The path following control technology of USV is a key part of realizing the offshore operation.However,as a typical underactuated system,USV is vulnerable to the influence of complex marine environment disturbance.At the same time,following different types of expected paths will also face different problems,which puts forward higher requirements for the design of USV path following controller.In order to solve the above problems,this thesis firstly summarizes the types and characteristics of common mathematical models of USV,including three maneuvering mathematical models and four response mathematical models.The differences and connections between different models and their respective applicable occasions are simply explained.The model information required for the path tracking of the USV is analyzed,and the 3-DOF mathematical model of the USV is finally selected and established,which lays the model foundation for the subsequent simulation experiments.Secondly,based on the indirect control method of improved LOS(Line-of-Sight)guiding law and fuzzy PID heading speed controller,the following control of a class of expected paths composed of independent path points is realized.In the process of following this kind of path,waypoint switching will cause the mutation of the expected heading,which will lead to the poor path following effect.To solve this problem,the LOS guidance law is improved by using the idea of variable speed control.Based on the existing LOS guidance law,the design of variable speed control law is added,so that it can provide both the expected heading and the expected speed at the same time,so as to reduce the impact of heading change during the waypoint switching.In order to give consideration to the practicability and robustness of the controller,the heading speed controller is designed by using fuzzy PID to realize the accurate tracking of the expected heading and speed.The effectiveness of the proposed method is verified by simulation and ship experiments.Finally,considering a class of expected path tracking control defined by parameter equation under marine environmental disturbance,an indirect path tracking control method based on the sideslip angle estimation of an ESO(Extended State Observer)is proposed.First of all,the path is different from the path consisting of individual path points,which are continuously changing.Although it does not involve the problem of waypoint switching,the path curvature will have a bad effect on the path following effect.In order to reduce the influence of curvature on path following,the speed guidance law is designed by establishing the relationship between speed and curvature.Secondly,for the sideslip angle caused by environmental disturbance,the extended state observer is used to estimate the sideslip angle and compensate it in the LOS guidance law,so as to improve the accuracy of the path tracking of the USV under ocean disturbance.Considering the perturbation of model parameters caused by ocean disturbance and external disturbance,a sliding mode controller is designed to track the expected heading and speed.Finally,the simulation results show the effectiveness of the proposed method.