The Modeling Research Of Modern Ship Dynamic Positioning System

With the rapid development of the global economy, energy shortages and environmental pollution have become a worldwide problem, so exploring and developing marine resources became the important sustainable ways for most countries. Ships and semi-submersible platforms as floating operating system is the important carrier of deep-sea assignments, the research for the vessel and platforms received more and more attention.The modern ship dynamic positioning (Abbreviation DP) system is that the ships rely on the power of the thrust system to overcome the wind and ocean currents, the interference of the external environment, such as the waves to keep itself at a certain position and head. Compared to the traditional moor and anchor positioning method, modern DP system isn't limited by depth, positioning more accurate and faster, etc. As the marine environment is complex and changeable, how to build a accurate mathematical for the system has been the orientation and research hotspot.This paper analyzes the DP system's current research situation at home and abroad. Take the ocean engineering ship as study subject, the paper established the dynamic positioning ships'model and Marine environmental disturbance force and thrusters mathematic model of the system, through the integral design of the control system and simulation tests show the effectiveness of the model.First, this paper studies different ship model structures and their hydrodynamic items'calculation method, then combined with our experimental ship model calculated its relevant hydrodynamic derivatives and mathematical model. this paper introduces the model's transformation method between the experimental ship and the actual ship. Marine environment disturbance force mainly includes the wind, waves and currents, the environment is complex and changeable constantly, also the disturbance models under different sea conditions is different, this paper discussed the environment's mathematical model. It introduces the thruster system's structure and its allocation strategies, presents the propeller's mathematical model and the calculation method of its thrust and torque coefficient.Secondly, this paper studies the design method and its performance of Kalman filter. According to the mathematical model of DP system, its filter and state estimation method were presented, ship speed and position of low frequency motion was acquired through this method. An improved Kalman filter is designed to filter out high frequency motion and measurement noise, the method presented in this paper is proved effective through simulation test.Finally, The control system architecture is introduced. According to the nonlinear characteristics of system model, an adaptive Backstepping control method was presented. By MATLAB simulation, the effectiveness of the model and control strategy was testified.