Research On Autonomous Berthing Control And Guidance Technology Of Small Unmanned Surface Vehicle

With the development of navigation,control,perception and other technologies in recent years,the autonomous and intelligent degree of small Unmanned Surface Vehicle(hereinafter referred to as USV)is also increasing,but berthing always needs human intervention.In the process of berthing,USV is not only affected by the wind and waves,but also has strict requirements on the residual speed,transverse distance and approach angle.In this paper,the characteristics of USV and the whole process of berthing are analyzed,and the autonomous berthing technology of USV is studied from two directions of planning guidance and motion control.The main contents of this paper are as follows:(1)In order to solve the problem that colored noise has "bias" in parameter identification of USV’s model,the auxiliary variable is used to improve the general least squares algorithm,and an auxiliary variable least squares method is proposed,which describes the establishment of USV’s model,the setting of auxiliary variable and the derivation of algorithm.The simulation and experimental results show that the proposed auxiliary variable least square algorithm can effectively reduce the influence of colored noise on the parameter identification of time series model of USV,and improve the accuracy of model output by more than 39%,which lays a foundation for control algorithm design and simulation experiment.(2)According to the berthing experience of manned ship,a "concentric circle" path planning method is proposed,and based on this principle,an adaptive guidance method is proposed to solve the problem of how to enter the berth of USV without side thrust.Firstly,the radius and angle of concentric circle are constrained,and the speed control model and berthing path decision system are designed;Then,according to the principle of line of sight guidance,an adaptive guidance method suitable for autonomous berthing is designed.The results show that the path planning method can reasonably plan the residual velocity,transverse distance and approach angle of USV when berthing,so that the USV can enter the berth directly without side push.Compared with the traditional line of sight guidance method,the adaptive guidance method improves the control accuracy of the USV by 35% at low speed,and effectively improves the path tracking ability of the USV.(3)In order to solve the problem of low-speed motion control in autonomous berthing,a fuzzy predictive control method is proposed according to the predictive principle.Taking the time series analysis model identified above as the prediction model,the optimal control quantity in the finite time domain is calculated according to the rolling optimization principle,and the error caused by the model mismatch is corrected according to the fuzzy control principle.The simulation and experimental results show that the fuzzy predictive control method can effectively reduce the rudder angle change increment at low speed control,the overall reduction is about 53%,and the heading oscillation convergence time of USV is reduced.(4)In order to improve the reliability and real-time performance of the control system platform,the embedded control box of USV is built.According to the system structure and related equipment of USV,the driver of related equipment and the task flow of control system are designed.In order to verify the autonomous berthing method proposed in this paper,virtual autonomous berthing experiment and real berthing experiment are carried out on the experimental USV.The experimental results show that the autonomous berthing method proposed in this paper can make the USV complete the autonomous berthing and achieve docking at the berth.