Research On Autonomous Berthing Trajectory Planning For Underdriven Merchant Ships

With the rapid development of the world economy and shipping industry,transportation ships are moving towards large-scale development,and higher requirements are also put forward for ship control performance and maneuverability.Due to the large parking stroke,large body size,large inertia,and wide obstacle avoidance areas of underactuated commercial ships,most berthing of underactuated commercial ships currently requires the assistance of tugs to avoid accidents.Autonomous path planning and berthing of ships can reduce dependence on human factors,effectively reduce navigation risks,and reduce human resources.While relieving the pressure on crew members,it also greatly improves the safety and stability of ship operation.In this thesis,the whole berthing process is divided into two stages: intelligent collision avoidance at the far terminal and calm berthing at the end of the terminal,and its unique transition area and domain model are established to provide a basis for the autonomous berthing of underdrive merchant ships,which is of great practical significance.The main research contents of this thesis are:(1)Based on the idea of separated ship motion model(MMG),establish a mathematical model for the movement of large ships in the harbor.Taking KVLCC1(KRISO Very Large Crude Oil Carrier 1)large ship as an example,combined with the proposed mathematical model of large ship motion in this thesis,the study of the ship’s rotation performance is carried out,and the simulation data is analyzed to verify the feasibility and reliability of the motion model proposed in this thesis during the berthing and maneuvering process of large ships;(2)This article divides the autonomous berthing trajectory planning of underactuated merchant ships into two parts: the intelligent collision avoidance stage at the far terminal and the stable berthing stage at the terminal.The main influencing factors of these two stages are analyzed.In the remote terminal stage,first determine the location of the transition area,and carry out a detailed analysis of the international rules for collision avoidance at sea.At the same time,combine the maneuverability of the underactuated merchant ship,establish a domain model for the underactuated merchant ship maneuvering.Based on this model,combined with the ship collision risk,carry out a comparative analysis and research of intelligent decision-making collision avoidance algorithms,and determine the optimal collision avoidance algorithm;(3)In the stage of quay end calming berthing,based on the need of underdriven merchant vessel berthing,numerical calculation method and PID automatic rudder control principle are used to analyze the influence of PID three parameters on the quay end calming berthing process and design the conventional PID controller.Line of sight guidance method(LOS)is adopted to design the guidance system to transform the convergence process of the underdriven merchant ship position tracking error in the path tracking process into the convergence process of the underdriven merchant ship bow angle tracking error,and finally realize the trajectory planning of the underdriven merchant ship autonomous berthing;(4)Carry out the design of hardware system and software system of the model ship experimental platform,build the model ship test platform,carry out the heading control,path tracking control and autonomous berthing test under the platform,analyze the results of path tracking,so as to verify the reliability of the autonomous berthing method proposed in this thesis.