| 摘要 |
1,153,223. Automatic position control. INSTITUT FRANCAIS DU PETROLE, DES CARBURANTS ET LUBRIFIANTS. Jan. 6, 1967 [Jan. 6, 1966], No.889/67. Heading G3R. Electrical signals dependent on the direction and magnitude of drift of a floating vessel from a desired position rotate a central annular element, carrying two propulsion units, about a vertical axis to a position in which drift is automatically corrected by applying a thrust corresponding to the magnitude of drift. In Fig. 2A, a floating vessel 2, e.g. for offshore drilling, is provided with a central well surrounded by an annular member 1 which is freely rotatable about a vertical axis ZZ' on ball and roller bearings 6 and 8 respectively. Annular member 1, the weight of which is substantially balanced by the upward force on it due to water displacement, carries a pair of propellers H 1 H 2 arranged diametrically opposite with their axes horizontal. In this arrangement the propeller axes are parallel and equidistant from axis ZZ'. The vessel is moved in any desired direction by rotating the annular member 1 to an appropriate position and applying equal thrust by the two propellers. To maintain the vessel over a desired position on the seabed, automatically, electrical signals corresponding to the rectangular co-ordinates of any drift relative axes of the vessel or absolute axes determined by a gyro-compass are derived either from a tiltmeter associated with a line connecting the vessel to the desired position or from the transit times of acoustic signals transmitted from the vessel to four hydrophone receivers located around the desired position on the seabed and connected to electromagnetic wave transmitters on buoys above. A system of sine-cosine resolvers or potentiometers is used to convert these rectangular coordinate signals to polar co-ordinate signals so that the signal representing angle of drift is available to cause rotation of the annular member 1 to a corresponding position either by an electric motor or by differential thrust of the propellers, and the signal corresponding to the extent of drift is available to produce a corresponding thrust of the propellers. These controls are effected through follow-up servosystems, propeller thrust variation being obtained by adjustment of the injection pumps of diesel engines. |
