Dynamic positioning of marine vessels
First Claim
1. A method of determining the position of a vessel on the surface of water relative to a reference point below the surface to which the vessel is connected by a riser, the method comprising:
- making measurements of the velocity of the vessel;
making measurements of the angle of the riser adjacent to the reference point; and
combining the velocity measurements and the riser angle measurements to derive an estimate of the position of the vessel.
3 Assignments
0 Petitions
Accused Products
Abstract
Dynamic positioning of a vessel 10 connected to the seafloor 14 by a riser 12 utilises a measurement of riser 12 bottom angle combined with a measurement of vessel 10 velocity, optionally obtained from a Doppler log 16. These two signals are combined to produce a single position estimate using an algorithm such as a Kalman filter. Using riser bottom angle only would result in an unstable control system, since the bottom angle lags the vessel motion by a considerable amount and the relationship is non-linear. Using the velocity measurement alone would result in a slow drift of position. The combination of the two eliminates the disadvantages of the individual measurements.
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Citations
11 Claims
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1. A method of determining the position of a vessel on the surface of water relative to a reference point below the surface to which the vessel is connected by a riser, the method comprising:
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making measurements of the velocity of the vessel; making measurements of the angle of the riser adjacent to the reference point; and combining the velocity measurements and the riser angle measurements to derive an estimate of the position of the vessel. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. Apparatus for determining the position of a vessel on the surface of water relative to a reference point below the surface to which the vessel is connected by a riser, the apparatus comprising:
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means for measuring the velocity of the vessel; means for measuring the angle of the riser adjacent to the reference point; and means for combining the velocity measurements and the riser angle measurements to derive an estimate of the position of the vessel. - View Dependent Claims (10, 11)
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Specification