Learning tracking controllers under unknown disturbances for the installation of rigid and flexible structures |
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Authors: | Hideyuki Suzuki Tao Qi Keisuke Watanabe |
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Institution: | (1) Department of Environmental and Ocean Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan, JP;(2) Aker Maritime Inc, Houston, USA, US;(3) Department of Marine Design and Engineering, Tokai University, Shimizu, Japan, JP |
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Abstract: | During the installation operations of underwater structures, offshore structures such as semisubmersibles, the steady nonlinear
hydrodynamic force due to the ocean current, the tidal current, and the hydrodynamic interaction between structures are regarded
as major disturbances. Generally, it is difficult and very expensive to collect information about these disturbances in advance,
although such knowledge would be important and necessary for precise installation. Because of this situation, we have proposed
a learning tracking controller (LTC) for automated tracking/docking operations of offshore structures. The LTC can be operated
without any information about current, and can be applied to the installation problem of flexible structures whose flexibility
cannot be ignored. In order to confirm the effectiveness of the LTC, basin tests were carried out using experimental models
with an unknown current. Two types of basin experiment were executed using an ultrasound ranging system and thrusters. One
was trajectory tracking of a semisubmersible, and the other was the precise mating of flexible underwater structures. In both
cases the LTC showed good performance, and in the latter case in particular, two flexible models were successfully made to
track the given trajectory and dock to the docking targets with an accuracy of ±5 mm, after the trajectory had been tracked
six to seven times for learning purposes. No elastic responses were excited in the flexible model.
Received for publication on Dec. 1, 1999; accepted on March 13, 2000 |
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Keywords: | : learning tracking controller flexible structural control unknown disturbances precise mating automated offshore installation |
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