Linear Formation And Iterative Docking Control Of Unmanned Ships

In recent years,with the development of technology and the improvement of demand,transport,recovery,power supply and other functions can be derived from the docking between multiple unmanned ships.In addition,the unmanned ship cluster can also be connected to the floating bridge by the way of end-to-end docking.In order to make the unmanned ship cluster docking accurately,a reliable formation and docking method is needed.Therefore,this paper studies the autonomous docking process of unmanned ship cluster under linear formation.The research contents are as follows:（1）Establish the model of unmanned ship system.According to the controlled object of unmanned ship,inertial coordinate system and volume coordinate system are established.The position and motion parameters of the unmanned ship under three degrees of freedom are expressed by using the linear relationship between coordinate systems,and the kinematics model of the unmanned ship is established.Then,the dynamics model is established according to the structure and propeller distribution of the unmanned ship.Finally,the maneuverability of unmanned ship under different inputs is analyzed by numerical simulation.（2）Design collision avoidance algorithm of unmanned ship linear formation.Partial differential equations（PDE）is used to model the process of unmanned ship formation,and the discrete distributed control rate of unmanned ship formation is obtained by three-point central difference method.The control rate boundary acts as the virtual leader of the unmanned ship formation and the rest as the followers.The follower only needs to know the relative position of the next step in the formation process based on the relative position of its left and right neighbors.In addition,repulsive force field is introduced through artificial potential field method to provide driving force for collision avoidance of unmanned ship formation,and potential field rotation force is added to help unmanned ship formation jump out of the local minimum.Finally,the simulation experiment is carried out to verify the feasibility of the collision avoidance algorithm of unmanned ship formation under random initial position.（3）Design the docking control algorithm of unmanned ship.The docking process of unmanned ship in linear formation can be regarded as the linear trajectory tracking process of unmanned ship.In the first docking process,the model predictive control method is used to track the unmanned ship.However,in the process of linear trajectory tracking,the unmanned ship cannot track linear trajectory well due to the influence of model mismatch,water flow,wind and other disturbances,so the docking fails.However,unmanned ship docking is a repeatable process,so when the unmanned ship fails in the first docking,it returns to the ori gin and starts docking again.In the subsequent docking process,the iterative learning model predictive control method is used to overcome the interference of the unmanned ship under the linear trajectory tracking.Finally,the feasibility of the iterative learning model predictive control method is verified by numerical simulation.（4）Coppelia Sim simulation software is used to demonstrate the formation and docking process of unmanned ships.The three-dimensional model of the unmanned ship,water surface scene,visual sensor,April Tag positioning tag,and the formation of the unmanned ships with docking control process are designed.Finally,under Coppelia Sim software,the feasibility of the unmanned ship linear formation and docking process is verified through three-dimensional dynamic demonstration.