Research On The Modeling & Characteristics Simulation For Ship Motion

Movement rules and control methods of ships can be analyzed through ship experiments at sea, however, these experiments are of high cost, long cycle, and sometimes have some risks. Instead, simulation experiments of ship motion model could overcome these disadvantages, and to a certain extent, they can reflect the ship movement rules, and replace some of the sea experiments. Therefore, studying force and mathematical models of ships not only has great significance to ship motion control and dynamic positioning of offshore platform, but plays a very important role to the development of a variety of ship simulator.Based on the analysis to force and the law of kinematics of system components of ships, this paper establishes ship mathematical model in three degrees of freedom, and considers the environmental disturbance force on the ship movement, and then related simulation experiments are done while position and heading changes of the ship motion are analyzed.(1) This paper introduces the coordinate system of the ship, various forms of force it suffers, the factors which impact the propeller thrust and torque, and the interaction between the ship hull and propeller movement.(2) Four-quadrant propeller characteristics and its analytical form are studied, and effective propeller thrust and torque calculation method, added mass of the ship and related content are discussed, as well as the mathematical model of ship-motor-propeller system is built.(3) On the basis of the mathematical model, the simulation model is built with MATLAB/Simulink, and the corresponding simulation experiment is completed. Compared to the KONGSBERG running results, the model in this paper could reflect dynamic characteristics of the propeller system.(4) The characteristics of ship motion system and the environmental interference power are analyzed, equations on three degrees of freedom of motion are created according to the ship kinematics law, and the mass and damping matrix are calculated while the motion equation is expressed in state space form, and then the simulation experiments with a thrust set is completed. After that, the impact on interference force for ship position and course is discussed.The ship-motor-propeller model here could act as a reference for electrical propulsion system based on dSPACE hardware in the loop simulation, the ship model on three-degree of freedom, to some extent, reflects the ship movement law, which is author's exploration research in dynamic positioning of ships and offshore platform.Finally, the main contents and the existent problems are summarized, and the future work is proposed.