Study On The Unified Motion Model Applied In The Dynamic Positioning System

There are three kinds of dynamic positioning system research methods namely,numerical simulation and model test and real ship testing.Model test and real ship testing need high cost and long experiment period,therefore the numerical simulation method is the most economical method.But the results of numerical simulation compared with model test and real ship testing results is far from,so the relative numerical study proceeds only commonly.Its directive significance is not necessarily a lot for the engineering practice.In numerical simulation,the equation of motion in the most dynamic positioning systems uses the low frequency maneuvering motion equation and the motion equation assumes that structure is excited with low frequency wave without considering the memory effect of fluid.So it is hard to capture the nonlinear response of the external exciting force on the structures.Simulation results of the platform motion,power consumption has no great guiding significance for engineering practice.Based on this idea,the author introduces the unifid motion equation into dynamic positioning system,and to conduct a comprehensive analysis to verify its effectiveness.This paper firstly introduces the basic theory of dynamic positioning system including dynamic positioning system compositions and compositions of the environment external force and describing the motion of the structures in different coordinate systems,etc.After a detailed introduction of unified equation theory includes the speed and zero speed equation of motions in the state space expression.Next make some conclusions including unifid motion equation and frequency equation maneuverability principle and the processing diagram,summarizing advantages and disadvantages of the different motion models derived from the formula.Then introduce dynamic positioning system's time-domain simulation of a semi-submersible platform and a simple simulation to validate effectiveness of two programs.Finally to make semi-submersible platform as an example and to include the design of typical working conditions are numerically simulated.To compare and analyse the unified motion equation and low-frequency maneuvering motion equation results including horizontal positioning accuracy,power consumption,rolling and pitching angles.In chapter 6,to introduce a semi-submersible platform experiment including dynamic positioning ability analysis in different working conditions and analysis of positioning precision,power consumption.Finally the results are compared with the results of unified equation of motion verifying the superiority of the unified motion equation in numerical simulation program,to make guidances for engineering practice.