Research On Automatic Berthing Control Of Unmanned Surface Vessel

In recent years,more and more attention is paid to the research and development of unmanned surface vessel.The design of automatic berthing controller under strong environmental disturbance is one of the key problems to be solved.This thesis investigates the intelligent control of unmanned surface vessel automatic berthing,aiming to provide new ideas and methods for the research of unmanned surface vessel berthing support system and intelligent/unmanned vessel full route automatic control system.The main research work completed as follows.(1)The maneuvering mathematical models of unmanned surface vessel with pod propulsion and flap rudder are established respectively.It is typical to study these two types of unmanned surface vessel with good maneuverability.For different forms of propeller and rudder,two different automatic berthing modes are adopted in this paper.A reasonable automatic berthing strategy is proposed for the maneuvering of the pod driven unmanned surface vessel;According to its characteristics of low speed and slow state change in the harbor,MMG(maneuvering modeling group)mathematical model of automatic berthing is established based on the thrust vector mathematical model of pod;The calculation method of marine environment disturbance is given.For the unmanned surface vessel with flap rudder,the separated mathematical model is established,and the lift force calculation formula of flap rudder is given.Then,the vessel's maneuverability is analyzed based on the method of equivalent rudder angle.The turning angles and RPMs(revolutions per minute)of pod driven vessel are related to the rotation speed and rudder angle of conventional vessel in a function relationship.Four working conditions are proposed for simulation,including the normal state of the vessel running process and the fault state.By comparing the maneuverability analysis method of twin-pod propulsion vessel with that of single propeller and single rudder vessel,a new idea is provided for the analysis of maneuverability of multiple thrusters.Finally,the maneuverability of pod driven unmanned vessel and flap rudder unmanned vessel is compared and analyzed.It can be concluded that these two types of unmanned vessel have better maneuverability than conventional vessel.(2)In view of the uncertainty of unknown time-varying disturbance and parameter of mathematical model,the automatic berthing control strategy of unmanned surface vessel driven by pod is given.The adaptive backstepping sliding mode control method based on GAN(generative adversarial networks)is used to design the control law.In the simulation,large amplitude oscillation is produced in the initial stage of sliding mode control.So the method of adding tracking differentiator in the initial stage of the system is adopted.According to the distribution characteristics of the thrusters of the pod driven vessel,the thrust allocation strategy based on the sequential quadratic programming is given.In the simulation analysis,the GAN-Backstepping-SMC method is compared with the sliding mode control method based on approaching law.The simulation results show that the two methods can complete the automatic berthing task of unmanned surface vessel under certain disturbance,and the GAN-Backstepping-SMC method has better dynamic control.(3)As the automatic berthing task requires high control accuracy,in order to further improve the control speed and anti disturbance capability,the relevant theoretical methods of finite time automatic berthing control with better practical engineering significance are introduced.Firstly,a finite time observer is designed to estimate the dynamic uncertainties inside and outside the system,and its finite time convergence is proved.In order to avoid the singularity when using the finite time control theory to design the control law,an automatic berthing controller based on global fast nonsingular terminal sliding mode is designed to avoid this problem.Finally,the simulation results show that the designed automatic berthing mechanism can achieve finite time stability and improve the control speed and anti disturbance capability of the automatic berthing process.(4)For the automatic berthing of underactuated unmanned surface vessel with flap rudder,an experiment of automatic berthing of unmanned surface vessel is carried out in the Japanese Institute of Fisheries Engineering.In order to determine the automatic berthing route,the method of line of sight is used to determine the trajectory of the unmanned vessel.The trajectory is designed to control the vessel's movement with a reasonable angle of entering the berth.In terrms of speed control,the step-by-step decreasing method is adopted according to the actual navigation berthing operation.Before the experiment,the remote control simulation system based on user datagram protocol(UDP)communication is established.The simulation test system is applied to verify the automatic berthing effect of GAN-Backstepping-SMC control law and finite time control law at first.The conclusion that finite time control law has better rapidity and stability under disterbances is also obtained.In the tank experiment,the nonlinear active disturbance rejection controller and PID controller are used to compare and analyze the ability of automatic berthing of underactuated unmanned surface vessel with flap rudder in windy and windless conditions.So the control effect of these two algorithms is simulated before the tank experiment.Combined with the simulation results,the actual tank experiment is carried out.The experimental results show that the nonlinear active disturbance rejection controller has good robustness and improves the stability under disturbance.By means of above-mentioned experimental study and simulation verification,which are beneficial to the research on automatic berthing control of unmanned surface vessel,the berthing control safety is likely improved,and the helpful experimental data is obtained.