Dynamic Analysis Of Dynamic Positioning Capability For Deepwater Floating Structure

Dynamic positioning system(DPS) has been the main locating way for floating structure in deep sea instead traditional mooring system, which has a wide range of applications in many fields, such as marine research, marine oil and gas resource development etc. However, there are only a small number of foreign agencies who have independent intellectual property rights software which can do the simulation of dynamic positioning system and analysis of dynamic positioning capabilities, they are in monopoly position in this field,there is no sophisticated software can be used in domestic reaearch.Based on the principle and components of dynamic positioning system, following work has been done. First, from the ship's three degrees of freedom maneuvering equations, reasonable linearization have been done to get a low-frequency motion model which is suitable for dynamic positioning system. The high-frequency motion of ship can be treated as the first-order wave motion, a fourth-order colored-noise filter driven by a white noise can simulate the ship's high-frequency motion, and the high-frequency motion model has been established. Second, according to the methods which some classification societies recommended and results of Hydrostar, A more reasonable procedure has been sought to calculate wind, wave and current load. Third, a Kalman filter have been selected to deal with unmodeled noise, measurement noise and high-frequency signals to get the optimal state estimation of ship motion, LQR have been applied to carry out the state feedback control of the various states components. The thrust distribution logic of semi-submersible platform and FPSO has been presented through a discussion at last.A dynamic analysis program for dynamic positioning system have been developed using the MATLAB, this program can simulate the motion of a DP controlled ship or platform under the corresponding sea state in a period of time, and present the vessel motion curves and thrust curves of each thruster in the simulation time.