Model experiments on dynamic positioning system using gain scheduled controller

This paper is concerned with the dynamic position control for a semisubmersible platform model using a gain scheduled H∞ controller. Offshore floating platforms are required to control their position within allowable deviation against the external forces of ocean surface current, wind and waves. A dynamic positioning system using thrusters is generally employed for this. The purpose of the control is to maintain a given position or to adjust the position using thruster activity that does not respond to linear wave force. Based on a rotation matrix in yaw, a linear model with 4 vertices was introduced. The problem was formulated in the framework of a multimodel-based design of the H∞ control law with pole region constraint. Methodology based on LMI (linear matrix inequality) was used to solve the problem. The gain scheduled H∞ controller was implemented by interpolation of the 4 vertex controllers. Model experiments with some successful results are shown.