Research on Dynamic Positioning System for Floating Structure

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The research is concerned with a thruster assisted mooring system and dynamic positioning system for a floating platform.(1) In the thruster assisted mooring system, moorings are used to maintain the position of the platform against quasi-constant external forces induced by current and wind. The control purpose is to suppress the slow drift oscillation due to drifting force in irregular wanes using thrusters so they do not respond the linear exciting force in the wave frequency range. The problem was formulated in a framework of HィイD2∞ィエD2 control, and was solved using the LMI control toolbox on Matlab. Model experiments in oblique incident waves were carried out and successful results were obtained.(2) A dynamic positioning system using thrusters is generally employed for controlling a position of a floating platform at the deep sea area because it is difficult to use mooring system. The specification of the proposed controller are that it maintain a given position and to change its position without offset using thrusters that do not respond to the linear exciting force in the wave frequency range. Based on a rotation matrix in yaw, a linear mathematical model with four vertices was introduced. The problem was formulated in a framework of multi-model based design of HィイD2∞ィエD2 control law with pole region constraint. Model experiments were carried out and the results were successful.