6. CONCLUSION
A new DPS using an advanced control was developed to improve position keeping characteristics of an offshore platform.
The tank tests are conducted for FPSO type platform and mono column type platform. Then, it can realize a stable holding at a specified position under environmental disturbance and minimize a total energy of control thrusters. Generally, It was found that the H∞ control provides better positioning performance in the wave area ranging from the low frequency to high frequency, compared with other controls[1]-[3].
Also, numerical simulators matched with the real system's behavior were developed, and can determine specification of the platform and simulate behavior of motion in advanced.
Through a series of studies, the dynamic positioning system could be established capable of obtaining a good positioning performance by a small thruster force under disturbed oceanographic and meteorological phenomena in petroleum developing areas. In addition, the control device capable of automatically control the positioning based on the positional and angular information obtained by sensors was developed, and its effectiveness was verified by the tank experiment.
ACKNOWLEDGEMENT
This study was performed through a joint research between Japan National Oil Corporation and Mitsubishi Heavy Industries, Ltd. We deeply grateful to Technology Research Center, Japan National Oil Corporation for its assistance and guidance, and are also gratefully obliged to members of Mitsubishi Heavy Industries, Ltd. for supporting design and experiment, and also Prof. Grimble and Senior Lecturer Dr. Katebi, University of Strathclyde, UK, for their assistance in the field of control theory.
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