JP4485895B2 - A device for measuring the position of a device in water, including an acoustic array with a sound velocity meter - Google Patents

Description

  The present invention relates to an apparatus for deploying a target at an underwater target position, and the apparatus is provided with a beacon for transmitting sound rays and a plurality of thrusters for controlling the arrangement of the apparatus with respect to the underwater target position.

  Such a device is known from WO 99/61307.

  Prior art devices have been used to deploy and / or recover loads of up to 1000 tons, for example on deep seabeds up to 3,000 meters or more. During deployment, the device is controlled by onboard control equipment floating on the sea surface. The control equipment needs to know the exact position of the device as accurately as possible. Therefore, a beacon on the board of the device transmits sound rays to the ship through seawater. A suitable sonic receiver receives this ray and converts it into an electrical signal that is used to calculate the position of the device relative to the ship.

  However, it has been found that as the depth of the device increases in seawater, the accuracy of position measurement decreases due to the bending of sound waves in seawater.

  Accordingly, it is an object of the present invention to further improve the position measurement accuracy of such devices during use in seawater or other fluids. Furthermore, such position measurement is required online (real time).

  In order to achieve this object, the device as defined at the beginning is characterized by a sonic meter for measuring the sonic velocity in the fluid surrounding the device. Thus, the speed of sound at a specific location in the fluid can be continuously measured and used to update the sound speed profile, i.e., data relating to sound speed as a function of fluid depth. From these data, the local bending of the sound ray can be determined online (in real time). Until now, such online decisions have not been possible. Thereby, the position measurement can be corrected in real time.

  In a preferred embodiment, the thruster comprises a first set of thrusters arranged to provide a torque control function and a second set of thrusters arranged to provide at least a translation function, each of the second set of thrusters A rotary actuator is provided on the thruster.

  This is a very advantageous embodiment. To prevent undesired rotation of the device attached to the load during deployment and thus avoid all problems associated with twisting and swiveling of the winding wire carrying the load, as already described in WO 99/61307 Only two thrusters are required. Furthermore, only two rotary thrusters are required to control the placement of the device with the load attached to the desired horizontal coordinate. Thus, before lowering the load with the device, the device can move the load to the desired horizontal coordinate, and once that coordinate is reached, the thruster maintains the load at the desired coordinate and undesired rotation of the load. Whilst the winding line can lower the load to a desired position on the seabed. Only when the desired target position on the seabed is reached, it is necessary to perform rotation in the desired orientation possible for the load by means of a thruster dedicated to torque control.

  It will be appreciated that a rotary thruster on an underwater device that deploys a load to a desired location is known from US Pat. No. 5,898,746.

  The device is preferably provided with a load cell that measures the weight of the load attached to the device. This weight suddenly decreases when the load is placed on the seabed. Thus, a signal indicating that the weight of the load has suddenly decreased can be used to determine when the device can be removed from the load.

  The present invention also relates to a processing arrangement arranged to drive an apparatus for deploying an object at a target position in water, the apparatus comprising a beacon for transmitting sound rays, a plurality of devices for controlling the position of the apparatus relative to the target position in water. And a sound speed meter that measures the speed of sound in the fluid surrounding the device, the processing configuration includes an acoustic receiver that receives the sound rays, and the processing configuration is used to calculate the position of the device. The processing arrangement is configured to use data obtained from the line, and the processing arrangement receives sound speed meter data from the sound speed meter online to determine a sound speed profile in the fluid and determines the sound ray transmitted through the fluid by the device. It is characterized in that the bending is calculated from the sound velocity profile and used for the calculation for determining the position of the device in real time.

  Such a processing arrangement can be controlled to drive the apparatus to a desired position in a desired direction with very high accuracy even at very deep depths in water. While lowering the device with load, the processing arrangement continuously receives sound speed data and determines a sound speed profile comprising sound speed data from the surface of the water to the depth of the device. The processing arrangement uses these data to determine the bending of the sound wave as a function of depth in the water and to correct the position calculation of the device.

  Such a processing configuration may be on a ship floating on the water surface. However, the part of the function of determining the sound velocity profile and calculating the ray curvature can be performed by one or more processors located elsewhere on the device itself.

  An additional sonic meter is preferably provided just below the surface of the water to provide actual data regarding the bending of the sound in the water surface layer and further correct the position calculation of the device.

  The reception of sound rays transmitted from the device is preferably performed by an acoustic array attached to the hull.

  In a highly preferred embodiment, all ships, sound rays and devices are provided with separate gyrocompasses that measure individual up and down, roll and roll. The output data from these gyrocompasses is used to further improve the accuracy of the device position measurement.

  The present invention also relates to a system comprising both such a vessel and apparatus.

  The present invention includes an acoustic array with a sound speed meter, and is configured to be deployed in water, the acoustic array receiving acoustic signals from the underwater device and processing output data of the acoustic array The processing arrangement is adapted to calculate the position of the device in the water relative to the acoustic array based on the output data in real time, and the sound speed meter is placed on the water. It is arranged to measure the speed of sound in the fluid layer directly below the floating ship and send the output data of the sonic meter to the processing arrangement, the processing arrangement based on the output data of the sonic meter, The calculation of the position of the device in water is corrected in real time.

  The device can be fully controlled by a suitable computer program after being loaded by the processing configuration. Thus, the present invention also relates to a computer program product comprising data and instructions that provide the ability to execute in the configuration after being loaded by the processing configuration.

  It also relates to a data carrier provided with such a computer program product.

  Hereinafter, the present invention will be described in detail with reference to the drawings. The drawings merely illustrate the invention and do not limit the scope thereof, which is defined only by the appended claims.

(Description of Preferred Embodiment)
Referring to FIG. 1, the layout represents FPSO 1 with a swivel collection stack 11 that is the origin of a riser 2, which is connected to a riser base 3 on the seabed 4. It is most important for the FPSO 1 to stay within the allowable dynamic excursion range during the life of the collection, so the FPSO 1 is moored to the seabed 4 by the anchor 6 or by the mooring leg 5 held by the pile.

  In order to extract oil or gas by the collecting vessel 1, it is necessary to place some relatively heavy objects on the seabed 4 with high accuracy.

  In order to secure a suitable and safe heel by the mooring leg 5, the mooring leg 5 needs to have approximately the same length. In this application, it is possible to use dredging with a weight of more than 50 tons, which is placed on the seabed 4 with an accuracy within a few meters. Furthermore, not only is the heel 6 itself very heavy, but also the mooring leg attached to the heel 6 has a weight equal to several times the weight of the heel 6 itself.

  In addition, other objects such as “template”, “gravity riser base”, and “collecting manifold” need to be placed on the seabed 4 with relatively high accuracy.

  The objects illustrated in FIG. 1 and required for oil and gas mining at sea and have to be placed on the sea floor are not only very heavy but also very expensive.

FIG. 2 shows a prior art ship 20 having a hoisting means such as a crane 21 on it. The crane 21 is provided with a hoisting wire 22, whereby an object or load 23 can be placed on the seabed 4 . In order to arrange the load 23, it is necessary to move the surface support together with the crane 21.

As a result, the inertia of the load 23 is overcome at any time, but due to the acceleration of the load 23, an uncontrollable situation occurs, thereby jumping over the target area. Due to the fact that the winding wire 22 and the load 23 are easily affected by ocean currents, when the winding wire 22 is lowered, the load 23 does not move linearly downward. The up and down float, roll and pitch of the ship 20 also negatively impacts the accuracy that can be achieved.

  FIG. 3 shows a crane ship 40 provided with an underwater device or system 50 for deploying a load 43 on the seabed 4. The marine vessel 40 includes first hoisting means provided with a first hoisting wire 42, for example, a winch 41. With this winding wire 42, for example, a load 43 such as a template can be deployed and placed on the seabed.

  As mentioned above, oil and gas field mining using a floating collection platform requires several heavy objects to be placed on the seabed 4 and must be placed on the seabed 4 with very high accuracy. Don't be. Nowadays, mining has to be done deep, up to over 3000m, making it more difficult to achieve the required accuracy. For example, one of the problems to be solved is the rotation that can occur in the load 43 carried by the winding wire 42.

  The device or system 50 is secured to the lifting wire 42 to control the position of the load 43 during deployment so that the load 43 can be placed on the seabed 4 within the required accuracy. A preferred embodiment of the system 50 will be described with respect to FIGS. 4, 5, 6a and 6b.

  System 50 may engage the end of lifting wire 42. Alternatively, the system 50 may engage directly with the load 43 itself. The system 50 includes a first or main module 51 provided with driving means such as a thruster 56 (i) (i = 1, 2, 3... I and I is an integer) (FIGS. 4 and 5). . The system further comprises a second or counter module 52. This counter module 52 is also provided with a thruster 56 (i). In use, the thrusters of the main module 51 and the counter module 52 are arranged on opposite sides of the lifting wire 42.

  System 50 is coupled to vessel 40 by a second lifting wire 45. The wire 45 can be operated using a second winding means such as a second winch 44, for example. The second winding wire 45 is installed outside the ship by an A frame 49, for example. The second winch 44 and the second winding wire 45 are usually lighter than the first winding means 48 and the first winding wire 42, respectively. The system 50 is further connected to the ship 40 by a lifeline 46. This lifeline 46 can be attached to the winding wire 45 or lowered separately from the third winch 47. The supply power wiring that provides power to the system 50, as well as electrical wiring or optical fiber, is housed in a lifeline, for example. System 50 is typically provided with means for converting electrical power into fluid power. Thus, the fluid power is used for control, i.e. for the thruster 56 (i) and the auxiliary tool comfort equipment.

  Recently, as the working depth has increased, the problems of twist and rotation of the load 43 and the long winding wire 42 have become serious. Because the heavy load 43 is attached to the underside of the winding wire 42, such twisting and rotation can cause the winding wire to wear considerably, which can cause severe damage to the winding wire. This wear may be so severe that the winding wire 42 breaks and the load 43 is lost. Another problem is that the wire in the ship may come off the sheave due to the large twisting of the wire.

Due to the fact that the thrusters 56 (i) of each of the main module 51 and counter module 52 are arranged on opposite sides of the lifting wire 42, the winding wire 42 is subjected to reverse torque in both directions. In this way, a twist prevention device is formed by the system. In order to improve the ability of the anti-twisting device, it is preferable that the distance between the main module 51 and the counter module 52 can be changed.

  FIG. 4 shows a detailed schematic diagram of a possible embodiment of a system 50 for deploying a load 43 on the seabed 4. FIG. 5 shows the system according to FIG. 4 from above.

  The system 50 includes a main module 51, a counter module 52 and an arm 53. The arm 53 can be detached from the main module 51. That is, the main module 51 can be used separately as a modular system. The arm 53 is provided with a recess 54. Two jacks 57 and 58 are provided on opposite sides of the recess 54, at least one of which can move with respect to the other. An object such as a crane block of the load 43 or the cable 42 can be clamped between the end faces of the jacks 57 and 58. In order to improve the contact between the jacks 57, 58 and the object, a clamping shoe lined with a friction element from a high friction material such as a special rubber is provided at each end of the jack.

  In use, the thruster 56 (i) can be used to position the system 50 relative to the target area of the seabed 4. The thrusters 56 (i) may be operated sequentially from a first position that is primarily inside the system 50 to a position where the thrusters protrude from the system 50. The two upper thrusters 56 (2), 56 (3) are rotatable relative to the underwater system 50. This is installed, for example, in each rotary actuator 65 (1), 65 (2). Its purpose will be described below. The thruster 56 (2) is shown enlarged in FIG. 4a.

  FIG. 5 illustrates that there are two locations 61, 62 at the top of the main module 52 for connecting the main module to the second lifting wire 45 and / or the lifeline 46. If the main module 51 is used separately, the position 61 can be used. The main module 61 balances in the air and in the water when the module 61 is deployed.

  When using the system 50, the connection between the vessel 40 and the system 50 is fixed at position 62 in order to keep the system in balance both in the air and in the water. An auxiliary counterweight 55 can be secured to the system 50 to improve the balance of the system.

  In use, the device 50 has no buoyancy. In order to improve the mobility of the system in the water, the arm 53 is provided with a hole 59 to avoid structural damage due to increased pressure during lowering and to ensure quick drainage during the collection phase.

As mentioned above, it is advantageous if the counter module 52 can be moved relative to the main module 51 . This can be achieved by using a jack 64a.

  The module 51 includes an outer frame and an inner frame (both not shown). The inner frame is preferably cylindrical. By connecting the outer frame to the inner frame, a very strong structure can be achieved. The strength of the structure is necessary to avoid premature fatigue of the system.

  The module 51 is designed, for example, to be partially made of high strength steel and thereby used as an integral part of the first winding wire 42 or the second winding wire 45. That is, the upper side of the module 52 is connected to the first part of the winding wire 45, and the lower side of the module 51 is connected to the second part of the winding wire 45, or the lower side of the module 51 is directly attached to the load. In this way, the load on the winding wire is transmitted through the module 51.

  As described above, the module 51 is provided with a thruster drive 270 for converting the electric power sent through the lifeline 46 into fluid power. The thruster drive 270 can include a motor, a pump, a manifold, and a hydraulic reservoir. Such conversion means are known to those skilled in the art and need not be further described herein. In order to communicate relevant data relating to the position, both in absolute position and relative to other objects, to the control system and / or the operator on the ship 40, the module 51 further comprises sensor means and Control means are provided. The module 51 is equipped with a sensor connection box. In addition, module 51 includes a light source 87, a gyro compass 256 including up / down floating, roll and pitch sensors, a pan tilt color camera 97, a USBL transponder 255 including a digit quartz depth sensor 253, a sound speed meter 258, and a sonardyne mini.・ Equipped with Lovnav 264. Below the module 51 are several platform light sources 94, pans and S.P. I. T.A. A camera 93, an altimeter 262, a Doppler log unit 266, and a dual head scanning sonar 260 are mounted. They are installed so that there is only clear sea water beneath them when in use. These are schematically illustrated in FIGS. 6a and 6b. It should be understood that this may be placed anywhere, for example, below module 52. Further, load cell 268 is part of system 51. All these components are schematically illustrated in FIG. 7b.

  As noted above, once the load has reached the desired depth, it is important to use a high resolution sonar device 260 with a distance log measured with a Doppler log unit 266 to achieve the required accuracy. is there. The sonar device 260 is used to determine a position relative to at least one object placed on the seabed. Using distance logging, positioning operations from maritime assistance, while achieving accuracy on the order of centimeters within a large radius, and other acoustics such as LBL (long baseline) arrays (or other USBLs, etc.) It becomes possible to dissociate from the positioning operation from the responder device.

  FIG. 7 a shows an electronic device 200 installed on the ship 40, and FIG. 7 b shows a deployable acoustic array 250 with a sonic meter 248 and a gyrocompass 252. FIG. 7 b also shows an underwater electronic device 249 installed in the underwater system 50.

  The device shown in FIG. 7a comprises four processors. That is, the navigation processor 202, the sound processor 224, the sonar control processor 236, and the thruster control processor 240. The navigation processor 202 interfaces with the other three processors 224, 236, 240 for intercommunication and complementarity.

  The navigation processor 202 includes a surface positioning device DGPS (relative global positioning system) 204, a ship gyrocompass 206, four display units 208, 210, 212, 214, a printer unit 218, a keyboard 220, a mouse 222, light It also interfaces with a fiber (de) multiplexer unit 244. If desired, a video splitter 216 may be provided to send one SVGA signal output of the navigation processor 202 to more than one display unit. In FIG. 7 a, display units 212, 214 are connected to navigation processor 202 via video splitter 216.

  The fiber optic (de) multiplexer unit 244 is also connected to an acoustic processor 224, a sonar control processor 236, and a thruster control processor 240.

  The acoustic processor 224 is connected to the command and control unit 226, which is connected to the keyboard 230, mouse 232 and display unit 228, all together forming the USBL surface unit 234.

  The acoustic processor 224 is connected to a deployable acoustic array 250 with a motion sensor unit 252 and a speed meter 248. In use, the acoustic array 250 is preferably mounted 2.5 meters below the keel of the vessel 40.

  An optical fiber (de) multiplexer unit 244 is further connected to an optical fiber (de) multiplexer 246 installed in the underwater system 50. The optical fibers interconnecting both optical fiber (de) multiplexers 244, 246 are preferably housed in a lifeline 46 (FIG. 3).

  The sonar control processor 236 is connected to the display unit 238. The thruster control processor 240 is connected to the display unit 242.

  The underwater device 249 is illustrated in block diagram form in FIG. 7b. USBL transponder 255 with DigiQuartz depth sensor 253, gyrocompass with motion sensor 256, (removable) sonic meter 258, dual head scanning sonar 260, altimeter 262, sonardyne mini lovnav 264, Doppler log 266, load cell 268, and thruster drive control 270 are all connected to fiber optic (de) multiplexer 246.

  Further, FIG. 7b shows two beacons 272, 274 that can be installed on the seabed or on a load to be deployed (or on a structure already on the seabed). These beacons 272, 274 are interrogated by, for example, Sonardine Mini Fovnav 264 (or equivalent equipment) and can send an acoustic signal back to the system 50, which is used by the system 50 itself to The distance and orientation relative to the beacon can be determined and measured. As a result of such an acoustic telemetry link, the relative position can be measured with very high accuracy. The number of such beacons is not limited to the two shown in FIG. 7b.

The functions of the components shown in the functional diagrams 7a and 7b are as follows.

  The navigation processor 202 collects marine positioning equipment data (DGPS receiver, DGPS correction, ship gyrocompass and ship motion sensors 204 and 206) to calculate the ship attitude and its fixed offset.

  The navigation processor 202 sends various settings via the fiber optic (de) multiplexers 244 and 246 to the navigation instruments of the system 50, namely the Doppler log 266, altimeter 262, and gyrocompass and motion sensor 256. After setup, it receives data from these instruments and further receives the distance / orientation and depth data of the system 50 via the acoustic processor 244 to calculate and display the system attitude and absolute coordinates.

  Integrated software for the navigation processor 202 has been developed, which works in manual or automatic mode to determine the initial orientation of the system 50, select from a number of waypoints, and perform initial positioning. Dynamic positioning controller software that can Furthermore, the onboard operator can enter an offset for the selected waypoint, which is entered in XY coordinates relative to the direction of the system 50. In order to stabilize and filter the position, another alternative type of subsea positioning device is selected via a specially designed window configuration on the screen (electronic page) of the display units 208-214. There is a possibility. The subsea instrument in use to calculate the position of the system 50 online (in real time) in other parts of the software to ensure that the operator has as many means as possible to obtain optimal results Various states are shown.

  An on-board gyrocompass 256 that includes up-and-down floating, roll and pitch sensors 88 on the system 50 provides data regarding the exact attitude of both the system 50 and the load 43 installed on the sea floor. At sea level, the operator can check these attitudes online (in real time) while descending in the control van, but even after the load 43 is placed on the seabed for final verification.

  The ship's gyrocompass 206 and the gyrocompass with motion sensor 252 installed in an acoustic array that can be used for the same function sends the ship's direction to the navigation processor 202. The navigation processor 202 uses this ship direction to calculate various offsets.

  Display units 208, 210, 212, and 214 display navigation settings, seabed view, sea level view for the operator in the control van and for another person on the marine sector operator bridge, respectively. Configured to do.

  The USBL command and control unit 226 consists of a personal computer that provides system control and configuration and displays a man-machine interface for operator control.

  The acoustic processor 224 is comprised of a single VME rack that performs a correlation process on the received signal, deep sea velocity measurement and ship attitude. In addition, it calculates the coordinates of the beacon to use. The acoustic processor 224 is coupled to the navigation processor 202 through Ethernet.

  The acoustic array 250 includes transmission and reception means. It can also be used as a transducer in acoustic communication with one or more beacons. Such a converter mode is useful when the lifeline 46 fails and an interrogation signal cannot be transmitted to the system 50. The acoustic interrogation signal can now be transmitted directly from the transducer through seawater. In all other cases, acoustic array 250 is used in receive mode. Reception is performed on two orthogonal reception bases that measure the distance and azimuth of the beacon relative to the acoustic array 250. Each receive base includes two transducers. Each received signal is amplified, filtered and forwarded to the acoustic processor 224 for digital signal processing.

  A sound speed meter 248 installed in the acoustic array 250 updates an important and unstable sound speed profile just below the ship 40 in real time. This is very important because the seawater turbulence appears to be very intense in these layers just below the ship 40.

  The gyrocompass 252 is preferably used as a motion sensor unit that transmits the attitude of the acoustic array to the acoustic processor 224 to correct data regarding the position of the system 50 underwater.

In the preferred embodiment, the beacon 274 operates in transponder mode and has the following characteristics:
-The challenge start signal generated by the acoustic processor 224 is an electrical signal, not an acoustic signal, and is transmitted to the beacon 274 through the cable link between the vessel 40 and the system 50.
The interrogation frequency is remotely controlled by the operator through a man-machine interface.

As described above, the beacon 274 can also be used in transponder mode. The beacon 274 is now activated by the surface acoustic signal transmitted by the acoustic array 250 and then sends an acoustic response signal to the acoustic array 250 through the coded acoustic signal.

Digiquartz depth sensor 253 included in beacon 274 allows very accurate depth data for system 50 to be transmitted to acoustic processor 224. The acoustic processor 244 uses these data to improve the calculation of the underwater location of the system 50 and its load.

  A sound speed meter 258 mounted in the underwater system 50 transmits data regarding the speed of sound in seawater at the depth of the underwater system to the acoustic processor 224 during descent and retrieval. The sound velocity data updates the sound velocity profiles in seawater calculated as a function of depth, and calculates ray bending from these profiles as a function of depth in seawater, thus correcting the underwater position calculation of the system 50. Used to do.

  The dual head scanning sonar 260 is used to measure the distance and direction of the system 50 to an artificial or natural target on the sea floor and output corresponding data as digital values to the navigation processor 202. The location of such artificial or natural targets can be pre-defined, or the navigation system can assign coordinates to each selected target. After giving coordinates to the object, it can be used as a navigation reference for the local coordinate system. As a result, the relative coordinate accuracy is 0.1 meter.

  An altimeter 262 attached to the system 50 measures the vertical distance from the underwater system 50 to the seabed and transmits output measurement data to the acoustic processor 224.

  The Doppler log unit 266 provides data regarding the value and direction of seawater flow at the depth of the underwater system 50. These data are used in two ways.

  First of all, the data received from the Doppler log unit 266 and the gyrocompass with motion sensor 266 is used by the acoustic processor 224 to smooth random noise related to the use of USBL online (in real time). . To obtain such smoothing, a filter is used in the main processor unit 224, such as a Kalman filter, Salomonsen filter, Salomonsen optical filter, or other suitable filter. Such filters are known to those skilled in the art. Appendix A provides a brief summary.

  Second, the output data of Doppler log unit 266 regarding current intensity, current direction, along with data regarding the current direction and intended direction of the underwater system 50, via the navigation processor 202, the thruster control processor 240. Sent to. Based on the intended direction, the thruster drive control 270 is automatically controlled. Manual control can also be provided.

  In a highly advantageous embodiment, a Doppler log unit 266 (or other suitable sensor) is used to measure the temperature and / or salinity of the seawater surrounding the system 50. Data regarding local temperature and / or salinity is transmitted to the navigation processor 202, which calculates and updates temperature and / or salinity as a function of seawater depth. These data are also used to determine the refraction of the sound wave through the seawater and thus correct the calculation of the position of the system 50.

  The Sonardine Mini Lovnav 264 is optional and can be used to provide the relative position of the system 50 with respect to local beacons on the sea floor as described above. For example, a long baseline (LBL) array can already be installed on the seabed and used for that purpose.

  The load cell 268 is used to measure the weight of the load 43 in engagement with the underwater system 50. If this weight is reduced, this is an indication that the load is currently placed on the seabed (or other target location) and the system 50 can be removed from the load 43. Output data from the load cell is transmitted to the navigation processor 202 through (de) multiplexers 244,246.

  The thruster drive control 270 is used to drive the thruster 56 (i) to bring the underwater system 50 to the desired position, as will be described in detail below.

  In FIG. 7a, four different processors 202, 224, 236 and 240 are shown to perform the functions of the system according to the invention. However, it is understood that the system can alternatively be implemented with any other suitable number of cooperating processors, including one main frame computer in a parallel or master / slave configuration. A remotely located processor may be used. A processor may be provided on the underwater system 50 to perform some of the functions.

  The processor includes memory components including a hard disk, read only memory (ROM), electrically erasable programmable read only memory (EEPROM) and random access memory (RAM). Not actively illustrated. Not all of these memory types need be provided.

  An input means known to those skilled in the art, such as a touch screen, may be provided instead of or in addition to the keyboard 220, 230 and the mouse 222, 232.

  Any communication within the overall configuration shown may be wireless.

  FIG. 5 illustrates a state in which the upper thrusters 56 (2) and 56 (3) are oriented in a direction different from that of the thrusters 56 (1) and 56 (4). The thrusters 56 (2) and 56 (3) are mounted on the rotary actuators 65 (1) and 65 (2), thereby rotating the thrusters 56 (2) and 56 (3) by a maximum of 360 °. Can turn around. The thrusters 56 (2), 56 (3) are preferably controllable separately so that each can be oriented in a different direction.

  In order for the thruster control processor 240 to accurately position the underwater system 50, a common coordinate system must be established between the navigation processor 202 and the thruster control processor 240. First, there is a standard coordinate system used by the navigation processor 202. However, it is preferable to establish two other coordinate reference systems for the underwater system 50.

  FIG. 8 shows three different coordinate systems. The coordinate system for the navigation processor 202 is denoted “Navigation Grid”. This coordinate system uses the direction of this “navigation grid” and its perpendicular.

  The thrusters 56 (2) and 56 (3) are controlled to provide a driving force in a direction called "thruster average direction". This direction, along with the normal, defines a second coordinate system.

  A third coordinate system is defined relative to the “system direction”, which is defined as the direction perpendicular to the line interconnecting the thrusters 56 (1), 56 (4).

  Thus, the error of the path followed by the underwater system 50 is an error vector that can be divided into a component parallel to the intermediate thruster direction called “average error” and a component perpendicular to the intermediate thruster direction called “perpendicular average error”. Can be defined. Appropriate sensors of the underwater system 50 provide the navigation processor 202 with a thruster intermediate direction and system direction. From these data, the navigation processor 202 generates a grid as shown in FIG.

The error is defined as the desired position DP minus the system position TP, thus generating a vector RΦ _EN for the navigation grid reference. In other words, the following formula is obtained.
DP-TP = RΦ _EN
further,
Φ _TN is the value obtained by subtracting the navigation grid direction from the system direction.
[Phi _MT is a value obtained by subtracting the system direction from the mean thruster direction.
This gives
DP-TP = RΦ _EM , Φ _EM = Φ _EN − (Φ _TN + Φ _MT )
Now that r [phi] _EM is known, it is possible to calculate the perpendicular of the mean and mean error.

  Two thrusters 56 (1) and 56 (4) are used to counteract the torsional force provided by the lifting cable 42, the drag of the equipment and the rotational moment induced by the turning of the positioning controller. The direction control loop needs to provide the navigation processor 202 with the actual system direction and the desired system direction. The actual system orientation is measured by gyrocompass 256. The desired direction is manually entered by the operator. From these two directions, the control loop of the navigation processor 202 calculates the angular distance between the required direction and the actual direction, and the direction of rotation required to move the system 50 accordingly. Next, a simple control loop controlled by the thruster control processor 240 regulates the power to the thrusters 56 (1) and 56 (4) and rotates the system 50 appropriately.

When the system 50 is powered up, it is preferred to orient both thrusters 56 (2) and 56 (3) so that the average direction of the thrusters is oriented parallel to the system direction. The thrusters 56 (2), 56 (3) are then given a small vector angle deviation from the system direction to assist in positioning in the two planes of the system 50. The size of this vector is preferably manually adjustable and may need to be configured for different tasks depending on actual sea conditions. Once the thrusters 56 (2) and 56 (3) are centered and turned, the positioning loop can take over control of the system 50.

  The positioning loop further comprises two phases.

  In the first next phase performed while the system 50 is still near sea level, the ocean current direction is measured by the Doppler log unit 266. The ocean current direction is transmitted to the navigation processor 202. Using this direction, the thruster control processor 240, which receives the appropriate command from the navigation processor 202, turns the rotary actuators 65 (1), 65 (2) so that the thruster average direction is approximately opposite to the ocean current direction. To drive. Thus, while the rotary actuators 65 (1) and 65 (2) are rotating, no power is supplied to any of the thrusters 56 (i). The system direction is measured by a fiber optic gyrocompass 256. Depth is constantly measured by Digiquartz depth sensor 254 and altitude by altimeter 262. The positioning loop then provides power to thrusters 56 (2) and 56 (3) using the mean and normal distribution for the mean error calculated according to the above equation to make system 50 desired Carry to the position.

  While driving the system 50 with the load 43 to the desired coordinates by the thrusters 56 (2), 56 (3), the thrusters 56 (1), 56 (4) are used to rotate the system 50 and its load 43. Counteract. This improves control. This is because, especially under heavy loads, the rotational movement can result in other undesirable movements in the load, which is difficult to control. If the system 50 with a load is on the desired coordinates, the load is lowered by the winding wire 42 with the system 50. During the lowering of the load 43, the load 43 is constantly controlled by the system 50 and maintains it in the desired position without rotating.

  In the next phase, the system 50 is, for example, about 200 m or less from the seabed 4. The Doppler log unit 266 then enters bottom track mode. This changes the work to a more accurate and faster response mode for the final approach to the target location on the seabed 4. The USBL random noise is then filtered using a gyro compass with Doppler log unit 266 and motion sensor 256. Once filtered, a good reading of the navigation data, including accurate system 50 speed, will make the position control loop very fast and stable. A highly fine-tuned control loop that results in motion control up to a few centimeters results. The sonar unit 260 and the Doppler log unit 266 can then be used to provide information about the perimeter of the target point, so that the load 43 can be placed in the proper coordinates and in the proper direction. Next, as required, the load 43 can be rotated by the thrusters 56 (1), 56 (4) as controlled by the thruster control processor 240.

  In order to reduce the normal average error, the thrusters 56 (2), 56 (3) are provided with two control loops: an average error control loop and a further control loop.

  The average error control loop adjusts the power equally for both thrusters 56 (2), 56 (3) to reduce the average error. As the system 50 reaches the target coordinates, the drive output to the thrusters 56 (2), 56 (3) decreases to a level that allows the system 50 to move its position in the ocean current. That is, the drive output was initially set to a level proportional to the average error. However, as the system 50 approaches the target coordinates, the control loop gradually reduces the drive power applied to the thrusters 56 (2), 56 (3). As the system 50 reaches the target coordinates, the drive output to the thrusters 56 (2), 56 (3) reaches an equilibrium that cancels the ocean current intensity. The average error control loop provides equal force with a sign equal to both thrusters 56 (2), 56 (3).

  An additional control loop is provided to reduce the normal mean error. This additional control loop adjusts the individual forces applied to the thrusters 56 (2), 56 (3) so that a motion perpendicular to the ocean current is generated. A further control loop thus applies equal forces of opposite signs to both thrusters 56 (2), 56 (3). The force applied to thrusters 56 (2), 56 (3) to reduce the normal mean error preferably decreases linearly to zero as system 50 moves to the target coordinates. Assuming that the normal direction has not changed at the point where the average error perpendicular has reached zero, the system 50 is positioned exactly above the target location on the seabed 4 and the thrusters 56 (2), 56 (3) Power is supplied to maintain the system 50 on the proper coordinates and correct for ocean currents.

  When the direction of the ocean current changes, the control loop described above needs to adjust the force applied to the thruster and eventually change the direction of the system. As the new ocean current direction acts on the system 50, the normal average error begins to increase as the system 50 moves from the target coordinates. To overcome this effect, the size of the normal mean error is again controlled and reduced to zero. The direction of the system is changed to counteract the ocean current or the natural drift of the system 50.

  The direction of rotation of the rotary actuators 65 (1), 65 (2) is defined by the normal average error symbol. To reduce the time required to rotate the rotary actuators 65 (1), 65 (2) to the required position, the thruster control processor 240 uses an algorithm to define the shortest route in the required direction. .

  For example, it is assumed that manual control by a joystick (not shown) connected to the navigation processor 202 is also arranged.

  Speed control is also preferably added during positioning of the system 50. It is preferred that the speed of the system 50 decreases as the system 50 approaches the target coordinates. For example, if the distance between the system 50 and the target is greater than a predetermined first threshold, the thruster is controlled to provide the system 50 with a maximum speed. A linearly decreasing velocity profile is used between the first threshold and the second threshold for the distance to the target coordinate, the second threshold being less than the first threshold. Within a distance less than the second threshold, the system is maintained at approximately zero speed.

USBL Measurement The USBL measurement principle is based on accurate phase measurement between two transducers. In one embodiment, a combination of short baseline (SBL) and ultrashort baseline (USBL) can be used, thereby allowing large distances between transducers without phase ambiguity. In USBL, accuracy depends on the signal-to-noise ratio and the distance between the transducers (like interferometer measurements). Next, a trade-off is made between the distance and the frequency limited by the hydrodynamic component in terms of dimensions.

ここで、σ_θは標準角偏差、
Ｌは変換器の距離、
λは波長、
θは方位角である。 Ambiguity is calculated by using SBL measurements in combination with correlation data processing. The signal to noise ratio is improved by using such correlation processing. The following equation defines the general accuracy of USBL.

Where σ _θ is the standard angular deviation,
L is the distance of the transducer,
λ is wavelength,
θ is the azimuth angle.

  The equation given above shows that it can be improved by increasing the distance L of the transducer, ie by increasing the array. Furthermore, the accuracy increases as the frequency increases. Hydrodynamic aspects and phase ambiguity reduce these parameters. The signal to noise ratio is increased by using correlation data processing.

  In order to optimize distance and accuracy, it is preferable to use a frequency of 16 kHz for the phase meter measurement. The correlation process can increase the distance range while maintaining a narrow pulse length for multipath identification.

  For ambiguity phase measurement, the system operates with SBL to determine the range sector and operates with USBL within the sector to achieve the highest accuracy.

  The range may be increased to distances greater than 8000 m by using fairly low frequencies.

Appendix A
Kalman filter The Kalman filter is probably the best known technology in the marine industry. This gives a fast filtering method based on a comparison towards the expected value calculated based on the latest history. Kalman filtering is not detailed, but see, for example, “Kalman Filtering-Theory and Practice” (ISBN 0-13-211335-X) by MS Grewal and AP Andrews Prentice Hall.

The position track can be combined with velocity data (Doppler log) and each point is improved based on adjacent points, distance in time and actual velocity. The weight between the Kalman value and the improved speed is determined by the Doppler efficiency factor, with higher values taking into account speed.
Advantages: Disadvantages:
Very fast Can be improved with fairly “smooth” result speed Not the best combination of speed and position

Simple Filter A simple filter quickly searches all positions and calculates a smooth curve that gives the least square error. That is a kind of least squares fit line.
Advantages: Disadvantages:
Fast Doppler log data is not used The result is smooth Not like a curved track

Salomonsen filter The Salomonsen filter is a highly integrated filter named after Hans Anton Salomonsen, a Danish mathematician and professor and PhD of the University of Aarhus. This takes advantage of the short-term stability of the Doppler track and combines this with the long-term tolerance of the position track.

Description Filters are used in situations where there is position data along the track, plus Doppler data. Doppler data is usually very precise, but gives no information about absolute position. In contrast, position data is an absolute position, but is usually not very precise.

The filter combines the two sets of data to produce a precise track with an absolute position. This is done as follows.
1. Doppler data is used to build the shape of the track, that is, the track formed as a cubic approximation.
2. Start at the origin (0,0) and use the velocity as defined by the Doppler data.
3. The position data is then used to accurately position the track. The track is stretched / compressed in translation, rotation, and straight to fit the position data as best as possible using the least squares technique.
4). Mainly translation. However, other variations also serve to correct systematic errors that may be present in Doppler data.

The fact that the location data is only used in the correction by 2 means that the location data is heavily averaged. This reduces position measurement uncertainty. Thus, if there is a lot of position data, the absolute position of the track is expected to be much more precise than each individual position measurement.
H. A. Salomonsen

Mathematical explanation The algorithm is divided into five steps: Step 1:
Calculate the acceleration at each point
1 / 2h _{k + 1} (X ₁ ″ + X _{k + 1} ″) = X _{k + 1} ′ −X _k ′
here
h _k = t _k −t _k−1
t _k = Time measurement time stamp
Speed measurement at X _k ′ = t _k
Acceleration measurement at X _k ″ = t _k Step 2:
Based on the acceleration and velocity and the previously calculated position (based on previous velocity measurements and acceleration), the next position is calculated.
_{X k + 1 = Sqr (h} k + 1) / 6 (2X k "+ X k + 1 ') + h k + 1X k' + X k
Where calculated at X _k = t _k (speed time stamp)
Step 3:
Calculate position with actual time stamp (using first velocity measurement)
X (t) = 1 / 2h _{k + 1} {((h _{k + 1} ) ^ 2 (tt _k ) +1/3 (t _k + 1-t) ^ 3-1 / 3 (h _{k + 1} ) ^ 3) X _{k + 1} ”/ 3 (tt _k ) ^ 3X _{k + 1} "}
Where X (t) = position at time t Step 4:
Step 5 of adding the position of the first speed measurement value to the position calculation value:
Advantages of moving, rotating, stretching or compressing the position calculation to match the position of the actual position line: Combining the best Doppler with the position Disadvantages Takes into account all the slow data due to the complex matrix Good Doppler Log-dependent results are smooth

Salomonsen Hikari The optical version of the Salomonsen filter was first introduced in the NaviBat online program and was devised to combine a faster solution with the better of the two methods.

  Because of its online nature, it only uses history to determine filter points. The result is therefore relatively coarse at the start of the line and becomes better as it moves.

Basic operation The filter initializes the filter, starting with a reset call. The reset is performed using the first speed measurement. The filter uses both velocity and position data. A cubic approximation curve is generated using velocity recording and the position is fitted as well as possible to this curve.

  The filter reads the stored location record for later processing.

  After reading the velocity record, create a “knot”. If there is a position reading between the previous speed record and the current speed record (in hours), adjust it to fit the curve.

The history filter gain parameter ranges from 0 to 1 and controls the effect of Doppler log data and history on the flow point.

  At a value of 1, the Doppler log data and history on the line has a greater weight. The value is reduced only when there are more position records than valid speed records.

  Useful values are in the range of 0.9 to 1, for example 0.99.

Error correction The position and velocity records can be compared to values predicted using previous data. Limits may be set when data is rejected.

Reset If there are many erroneous data points, there is a risk that the filter will lose track. The operator can manually reset the filter, i.e. kill the history (attempted to design an automatic reset).
Advantages: Disadvantages Combining the best Doppler and position "Not smooth" at the start of the line
Can handle noisy Doppler data with fast overall results that are smooth

Schematic representation of an FPSO (floating, collecting, storing and unloading system) dedicated to offshore petrochemical collection. It shows a prior art crane ship and represents the load mounted on the crane block with a relatively long wire rope, so that it can be understood that control of the load is virtually impossible at large depths. 1 shows a crane ship and underwater system for deploying and / or recovering loads from the seabed according to the prior art. FIG. 2 shows a detailed schematic diagram of a possible embodiment of an underwater system. 1 shows a detailed schematic diagram of one of the rotating thrusters. The underwater system seen from above is shown. The lower side of the main module with several detectors is shown. The lower side of the main module with several detectors is shown. 1 shows a schematic block diagram of an electronic device on a ship. 1 shows a schematic block diagram of an electronic device relating to sound rays and an underwater system. 3 shows the definition of three different coordinate systems used while driving an underwater system to its target position.

Explanation of symbols

50 Underwater system 51 Main module 52 Counter module 56 Thruster 57 Jack 58 Jack 200 Electronic device 249 Underwater electronic device 250 Acoustic array 252 Gyrocompass 258 Sound velocity meter 260 Sonar device 266 Topler log

Claims (14)

A device comprising an acoustic array (250) with a sound velocity meter (248) adapted to be deployed in water, said acoustic array (250) receiving acoustic signals from underwater equipment (249) and acoustic Arranged to send the output data of the array (250) to the processing arrangement, the processing arrangement being provided in the ship, and in real time the underwater equipment (249) for the acoustic array (250) based on the output data The sound speed meter (248) measures the speed of sound in the fluid layer immediately below the ship floating on the water and outputs the output data of the sound speed meter (248). Arranged to be sent to a processing arrangement, which corrects the calculation of the position of the underwater device (249) in real time based on the output data of the sonic meter (248). apparatus. The acoustic array (250), dislocation of the acoustic array (250) includes an exercise sensor that sent to the processing arrangement of the output data by measuring the roll and pitch (252), said processing arrangement, said motion sensor The apparatus according to claim 1, wherein the calculation of the position of the underwater device (249) is corrected in real time based on the output data of (252).   The apparatus of claim 2, wherein the motion sensor (252) comprises a gyrocompass.   The apparatus of claim 1, wherein the acoustic array (250) is adapted to be mounted on a hull of the ship. The apparatus of claim 1, wherein the acoustic array (250) is arranged to send an acoustic interrogation signal to the underwater device (249). The acoustic array (250) is arranged to operate in the receive mode to be executed in two orthogonal reception base, the underwater equipment receiving base, to said acoustic array (250) to the two orthogonal ( 249). The apparatus of claim 1, wherein the distance and azimuth are measured. The apparatus of claim 6, wherein each receiving base includes at least one transducer. The apparatus of claim 1, wherein the acoustic array (250) is arranged to amplify, filter, and transmit a received signal to the processing arrangement. A processing configuration (202, 224, 236, 240) for data communication with an acoustic array (250) equipped with a sound velocity meter (248),
The acoustic array (250) is adapted to be placed in water and receive acoustic signals from an underwater device (249);
The sound velocity meter (248) measures the sound velocity of the fluid layer directly below the hull (40) on the water surface.
A processing configuration (202, 224, 236, 240) is provided in the ship and is adapted to receive acoustic array output data from the acoustic array (250), and based on the acoustic array output data, the acoustic array (250) The relative position of the underwater device (249) can be calculated in real time;
The processing configuration (202, 224, 236, 240) receives sonic meter output data from the sonic meter (248), and corrects the calculation of the position of the underwater device (249) based on the sonic meter output data. Processing configuration that is possible in real time.   10. The processing arrangement (202, 224, 236, 240) of claim 9, further comprising a navigation processor (202) in data communication with at least one of the surface positioning device (204) and the hull gyrocompass (206). Constitution.   11. The processing arrangement (202, 224, 236, 240) of claim 9 or 10, further comprising an acoustic processor (224) adapted for data communication with the acoustic array (250). 12. The processing arrangement (202, 224, 236, 240) according to any one of claims 9 to 11, further comprising a thruster control processor (240) adapted for data communication with a Doppler log device (266). And an acoustic processor (224) adapted to perform data communication, wherein the Doppler log device (266) has at least one of the strength of the seawater tide and the direction of the tide at the depth of the underwater device (249). The processing configuration that is to be measured.   A ship having the processing configuration according to any one of claims 9 to 12.   The ship according to claim 13, further comprising an acoustic array (250) arranged in a fluid layer immediately below the ship (40).

Images