Research On The Thrust Allocation For Dynamic Positioning System Of Semi-submersible Platform

Dynamic positioning system can resist external interferences (wind, wave and ocean current etc) and keep ship steadily in given position and yaw angle in command of control system with its own Power, It has no influence of ocean depth, positions accurately and rapidly, and operates expediently. Thrust allocation is an important part of the dynamic positioning system. In this thesis, we propose a rational and effective method of solving thrust allocation to the semi-submersible rig based on the GA optimal algorithm.In this paper, we introduce the theory of thrust allocation and GA optimal algorithm first, and give the mathematic model of thrust allocation with eight azimuth thrusters. We also give the optimum objective and constraint conditions by the actual system, and then design our thrust allocation algorithm with the help of the basic operations of the GA optimal algorithm.In order to validate the thrust allocation algorithm, we give the simulation system mathematic model first, and then we introduce the design of the controller,simulation of wind,application of the thrust allocation,validation of the mathematic model of the platform and the movement simulation.We present a simulation at last, in the simulation a given task was accomplished in a designed typical environment: average wind speed is 10 m/s, the wind angle is 45,225 and 315 degree. We give the curves of the output thrusts and angles. we analyze the datum gained, and prove that the thrust allocation we designed is feasible. In the end, the research on GA optimal algorithm with different parameters was given.