Patent EA-004201-B1 (EA)
Title: Apparatus for deploying a load to an underwater target position with enhanced accuracy and a method to control such apparatus
IPC: G01S5/14
Filed: 2000-03-20
Abstract: 1. Apparatus (50) for deploying an object (43) to an underwater target position, the apparatus being provided with a beacon to transmit acoustic rays and a plurality of thrusters (56 (i), i = 1, 2 ... I, I being an integer) to control positioning of said apparatus with respect to said underwater target position characterized in that the apparatus is provided with a sound velocity meter (258) to measure velocity of sound in a fluid surrounding said apparatus and to transmit sound velocity data in real-time. 2. Apparatus according to claim 1, wherein said thrusters comprise a first set of thrusters (56(1), 56 (4)) arranged to provide a torque control function and a second set of thrusters (56 (2), 56 (3) arranged to provide at least a translation function, each thruster of said second set of thrusters (56 (2), 56 (3)) being provided with a rotary actuator (65(1), 65 (2)). 3. Apparatus according to any of the claims 1 or 2, wherein said apparatus is provided with a gyrocompass with motion sensors (256) to sense roll and pitch of the apparatus in use. 4. Apparatus according to any of the preceding claims, wherein the apparatus is provided with a sonar unit (260) to determine the position of said apparatus with respect to at least one object external to said apparatus. 5. Apparatus according to claim 4, wherein the apparatus is provided with a Doppler log unit (266) to measure current strength of said fluid. 6. Apparatus according to any of the preceding claims, comprising load cells (268) to measure weight of a load (43) engaged by the apparatus. 7. Apparatus according to any of the preceding claims, wherein the apparatus is provided with a temperature sensor (266) to measure temperature in said fluid and to transmit temperature data in real-time. 8. Apparatus according to any of the preceding claims, wherein the apparatus is provided with a salinity meter (266) to measure salinity of said fluid and to transmit salinity data in real-time. 9. A processing arrangement arranged to drive an apparatus (50) for deploying an object (43) to an underwater target position, the apparatus being provided with a beacon to transmit acoustic rays, a plurality of thrusters (56 (i), i = 1, 2 ... I, I being an integer) to control positioning of said apparatus with respect to said underwater target position, and a sound velocity meter (258) to measure velocity of sound in a fluid surrounding said apparatus and to transmit sound velocity data in real-time, the processing arrangement being provided with an acoustic receiver (250) to receive said acoustic rays, the processing arrangement is arranged to use data derived from said acoustic rays in a calculation to determine the position of the apparatus characterized in that the processing arrangement is arranged to receive on-line sound velocity meter data from said sound velocity meter (258) to determine a sound velocity profile in said fluid and to calculate from said sound velocity profile bending of said acoustic rays transmitted by the apparatus through the fluid and to use this in the calculation to determine the position of said apparatus in real-time. 10. Processor arrangement according to claim 9, wherein said thrusters of the apparatus comprise a first set of thrusters (56(1), 56 (4)) arranged to provide a torque control function and a second set of thrusters (56 (2), 56 (3) arranged to provide at least a translation function, each thruster of said second set of thrusters (56 (2), 56 (3)) being provided with a rotary actuator (65(1), 65 (2)), and said processing arrangement is arranged to perform the following functions in use: - to control application of driving power to said thrusters of said first set of thrusters (56(1), 56 (4)) to keep said apparatus in a desired orientation in a first plane defined by driving forces generated by said thrusters (56(1), 56 (4)) of said first set; - to control application of driving power to said thrusters of said second set of thrusters (56 (2), 56 (3)) and to said rotary actuators (65(1), 65 (2)) to move said apparatus in a mean direction and a direction perpendicular to said mean direction to a desired location, said mean direction and said direction parallel to said mean direction being in a second plane defined by driving forces generated by said thrusters (56(1), 56 (4)) of said second set. 11. A processing arrangement according to claim 10, in said apparatus said first and second plane not being coincident, the processing arrangement being arranged to receive first sense signals from a gyrocompass with motion sensors (256) on the apparatus (50) regarding roll and pitch of the apparatus in use. 12. A processing arrangement according to claim 11, wherein the first sense signals from the gyrocompass with motion sensors (256) are used in the calculation to determine the attitude of the apparatus. 13. A processing arrangement according to any of the claims 9-12, the apparatus including a temperature sensor (266), wherein the processing arrangement is arranged to receive temperature data from said temperature sensor, to update a temperature profile in said fluid and to assist a correction of determining the position of said apparatus in real-time. 14. A processing arrangement according to any of the claims 9-13, the apparatus including a salinity meter (266), wherein the processing arrangement is arranged to receive salinity data from said salinity meter, to update a salinity profile in said fluid and to correct determining the position of said apparatus in real-time. 15. A vessel provided with a processing arrangement according to any of the claims 9 through 14. 16. A vessel according to claim 15, wherein the vessel is provided with an acoustic array (250) attached to a hull of the vessel and an ultra short base line surface unit (234) on board of the vessel arranged to communicate with said acoustic array (250), the acoustic array (250) being arranged to receive acoustic signals from at least said apparatus (50) and to provide acoustic array output data to said processing arrangement, which is arranged to perform, in real-time, the calculation of the position of at least said apparatus (50) relative to said acoustic array (250) based on said acoustic array output data. 17. A vessel according to claim 16, wherein the acoustic array (250) comprises a sound velocity meter (248) to measure velocity of sound in fluid layers just below the vessel and to provide sound velocity meter output data to said processing arrangement, said processing arrangement being arranged to correct said calculation of said position of said apparatus (50) based on said sound velocity meter output data in real-time. 18. A vessel according to claim 16 or 17, wherein the acoustic array (250) comprises an acoustic array gyrocompass (252) to measure heave, roll and pitch of the acoustic array (250) and to provide acoustic array gyrocompass output data to said processing arrangement, the processing arrangement being arranged to correct said calculation of said position of said apparatus (50) based on said acoustic array gyrocompass output data in real-time. 19. A vessel according to any of the claims 15 through 18, wherein the vessel comprises a vessel gyrocompass (206) to measure heave, roll and pitch of the vessel and to provide vessel gyrocompass output data to said processing arrangement, the processing arrangement being arranged to correct said calculation of said position of said apparatus (50) based on said vessel gyrocompass output data in real-time. 20. A system comprising a vessel according to any of the claims 15 through 19 and an apparatus according to any of the claims 1 through 8, the apparatus and the processing arrangement being arranged to communicate with one another. 21. A system according to claim 20, wherein the apparatus and the processing arrangement are coupled via fiber optic (de) multiplexers (244,246) interconnected by an optical fiber. 22. A method of driving an apparatus (50) for deploying an object (43) to an underwater target position, the apparatus being provided with a beacon to transmit acoustic rays, a plurality of thrusters (56 (i), i = 1,2, ... I, I being an integer) to control positioning of said apparatus with respect to said underwater target position, and a sound velocity meter (258) to measure velocity of sound in a fluid surrounding said apparatus and to transmit sound velocity data in real-time, the method comprising the steps of: - receiving said acoustic rays, - using data derived from said acoustic rays in a calculation to determine the position of the apparatus - receiving sound velocity meter data from said sound velocity meter (258) and deter mining a sound velocity profile in said fluid, and - calculating from said sound velocity profile bending of said acoustic rays transmitted by the apparatus through the fluid and to use this in the calculation to determine the position of said apparatus. 23. A computer program product comprising data and instructions that after being loaded by a processing arrangement provides said arrangement with the capacity to carry out a method according to claim 22. 24. A data carrier provided with a computer program product according to claim 23.