| As an intelligent and unmanned small ship,Unmanned Surface Vehicles(USVs)have been used more and more in maritime transportation,military patrols,environmental monitoring,and search and rescue operations.However,due to the underactuated nature of the USVs without side thrusters and the low-speed during berthing,the steering performance of the USVs is poor.Additionally,there are also surge and wall effects,wind and wave disturbances,and other interferences that can significantly affect the state of the USVs during low-speed berthing.Therefore,autonomous berthing control of underactuated USVs is a very complex problem.This thesis studies the autonomous berthing problem of the USVs,and the main contents are as follows:1 Firstly,the commonly used coordinate system for the USVs is introduced,and then a6 DOF mathematical model is established based on the motion characteristics of the USVs.According to the actual application situation,it is simplified into a 3DOF mathematical model.Finally,a brief introduction is given to the line-of-sight guidance method used in this article.2.A study was conducted on the path tracking control problem of the USVs during autonomous berthing,using a model-free adaptive predictive control algorithm based on the USVs’ path tracking control.Firstly,the desired heading angle was obtained through a lineof-sight guidance algorithm,then the outer-loop PID control algorithm was used to output the desired heading angle velocity.The error between the desired heading angle velocity and the actual heading angle velocity was used as the input of the model-free adaptive predictive control algorithm,which ultimately resulted in the output of rudder torque control.The convergence of the tracking error of the closed-loop system and the stability of bounded input and output were analyzed.Finally,in an undisturbed environment and a disturbed environment,the designed controller was compared with the classical PID control algorithm and model-free adaptive control algorithm through simulation experiments,verifying the effectiveness and superiority of the model-free adaptive predictive scheme in autonomous berthing control of the USVs.3.A fractional-order model reference adaptive control algorithm for the path tracking of the USVs is studied based on the Popov hyperstability theory.Firstly,a suitable reference model is selected based on the 3DOF mathematical model of the USVs.Then,the PID algorithm is combined with the model reference adaptive control algorithm,and a fractionalorder module is introduced to achieve control of the heading angle and velocity of the USVs.The stability of the control algorithm is proven using the Popov hyperstability theory.Simulation results show that the control algorithm can effectively control the heading angle and velocity of the USVs to the desired values,and can reduce the impact of disturbances such as wind,waves,and currents on the control performance. |
