| 摘要 |
A semi-submersible floating platform having a deck supported above water by four partially-submerged main columns attached to the deck and by two totally-submerged pontoons each attached to a different pair of the main columns is provided with a damping control system for suppressing undesirable motion of the platform caused by wave motion. This damping control system includes a velocity sensor for sensing the velocity of at least one of heave, roll, and pitch components of the undesirable motion of the structure and further includes control apparatus for exerting on the platform a damping control force that is a function of and in phase opposition to the sensed velocity. The control apparatus includes one or more ballast tanks in communication with the water and apparatus for driving water from or drawing water into each ballast tank as a function of the sensed velocity. Each ballast tank may be included within an associated column or pontoon of the platform and may be provided with a ballast sensor for sensing the actual volume of water within the ballast tank relative to a mean volume of water therein. In this case, the control apparatus may include apparatus responsive to the velocity sensor and each ballast sensor for driving pump apparatus to vary the actual volume of water within each ballast tank relative to the mean volume of water therein as a function of the sensed velocity. Alternatively, each ballast tank may be mounted on the outboard surface of an associated column of the platform at approximately the location where the ambient water level intersects the column. In this case, the control apparatus may include pump apparatus for varying the air pressure in each ballast tank as a function of the sensed velocity to drive water from or draw water into each ballast tank. Although the damping control apparatus is especially effective for suppressing undesirable motion of the platform at wave periods substantially equal to the resonant period of the platform, it is also effective at other wave periods. Suppression of undesirable motion at such other wave periods may also be achieved by modifying the geometry of the columns and/or pontoons which are apportionable in sectors about a reference point of the platform. This may be accomplished, for example, by altering the cross-sectional area of the pontoons along the length thereof or by otherwise modifying the pontoons so that the portion thereof in each sector has an effective center of dynamic pontoon force that is disposed outboard of the effective center of displacement volume of the associated portion of the columns in the same sector. |
