GB2488963A - Portable station for measuring and adjusting the magnetic signature of a naval ship - Google Patents
Portable station for measuring and adjusting the magnetic signature of a naval ship Download PDFInfo
- Publication number
- GB2488963A GB2488963A GB9308296A GB9308296A GB2488963A GB 2488963 A GB2488963 A GB 2488963A GB 9308296 A GB9308296 A GB 9308296A GB 9308296 A GB9308296 A GB 9308296A GB 2488963 A GB2488963 A GB 2488963A
- Authority
- GB
- United Kingdom
- Prior art keywords
- magnetic
- ship
- measuring
- magnetic field
- naval ship
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
- G01V3/00—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation
- G01V3/08—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices
- G01V3/081—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices the magnetic field is produced by the objects or geological structures
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
- B63G—OFFENSIVE OR DEFENSIVE ARRANGEMENTS ON VESSELS; MINE-LAYING; MINE-SWEEPING; SUBMARINES; AIRCRAFT CARRIERS
- B63G9/00—Other offensive or defensive arrangements on vessels against submarines, torpedoes, or mines
- B63G9/06—Other offensive or defensive arrangements on vessels against submarines, torpedoes, or mines for degaussing vessels
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/02—Measuring direction or magnitude of magnetic fields or magnetic flux
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/12—Measuring magnetic properties of articles or specimens of solids or fluids
- G01R33/1215—Measuring magnetisation; Particular magnetometers therefor
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
- G01V3/00—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation
- G01V3/08—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices
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- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- General Physics & Mathematics (AREA)
- Remote Sensing (AREA)
- Life Sciences & Earth Sciences (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- Electromagnetism (AREA)
- Geology (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Environmental & Geological Engineering (AREA)
- Geophysics (AREA)
- Aviation & Aerospace Engineering (AREA)
- Measuring Magnetic Variables (AREA)
- Geophysics And Detection Of Objects (AREA)
Abstract
The portable station for measuring and adjusting the magnetic signature of a naval ship provided with magnetic immunisation loops comprises at least two measuring sets intended to be deployed at sea on either side of the naval ship, each measuring set comprising at least two magnetic sensors (C1, Cn) disposed vertically, one above the other in each case, and means for transmitting measurements (18, 19). The naval ship is equipped with means for receiving measurements and means for computing the theoretical magnetic field, the computing means comprising a magnetic model of the naval ship allowing computation of the magnetic field radiated under the naval ship.
Description
Pgrta1ble 8t&tiQn for ffiçaaurinaAnd dusting the nk&gaetc a ignatur QLailaval sJ4p The invention relates to a portable station for measuring and adjusting the magnetic signature of a naval S ship deployable at sea.
It is known that the presence of ferromagnetic materials in a naval ship renders the latter detectable by means for detecting its "magnetic signature". These detection means may for example by built into mines or carried by aircraft.
The magnetic signature of a ship is constituted by its permanent magnetisation and by its induced magnet-isation. The permanent magnétisation is due to the ferromagnetic materials used in the construction of the ship and, is substantially constant. On the other hand, the induced magnetisation is essentially variable and, in the case of a ship, depends on its orientation in the earth's magnetic field, on its heading and on its incli-nation due to roll and pitch.
The magnetic signature of the ship therefore allows it to be spotted, followed, and possibly allows the guidance or firing of missiles for the purpose of destroying it. It is therefore very important to minimise or even to eliminate this magnetic signature in order to prevent its detection by a magnetic method.
This magnetic ixnmunisation method is carried out by creating in the volume of the ship a magnetic field which compensates for that of the ship in order to eliminate its magnetic signature. To this end, the ship is provided with a set of circuits called immunisation loops which carry adjustable electric currents.
The adjustment of the currents in the immunisation loops is carried out by means of a measuring station. Conventionally, the measuring stations are constituted by a linear array of magnetic sensors dis-posed on the sea bed and connected by cables to a station installed on land which analyses the measurements taken in order to determine the characteristics of the currents to be caused to flow in the various loops.
A *
The various components of the permanent magnetisation and of the induced magnetisation of a naval ship are determined by means of such a measuring station by making the naval ship travel the same path over the S array of magnetic sensors several times, using different headings.
However, such a measuring station requires a series of operations such as adjustment of the alignment of the sensors and measurement of their position, these operations becoming more difficult as the number of sensors increases. Furthermore, it is not transportable since it is necessary for the sensors to be disposed in line and connected to a processing centre installed on land comprising means for measuring the trajectory of the ship. Consequently, when the ship is distant from the measuring station, there are no longer any means for monitoring its magnetic signature and possibly reducing it by modifying the electric currents flowing in the inununisat ion loops.
It is also known to produce transportable magne-tic measuring stations which can be carried on board the ship and which allow, in particular, the computation of the various components of the magnetic magnetisation of a naval 8hip according to its geographic position, for example in its port of departure and then in its port of arrival at another latitude. In particular, a magnetic measuring station exists which is transportable and comprises two magnetometers placed on the sea bed and each connected to a radio buoy on the surface transmit-ting the data collected by the magnetometers to the naval ship.
The naval ship comprises on-board computing means allowing the magnetic field under the naval ship at sea-bed level to be computed. The two magnetometers must be separated by a distance equal to at least twice the depth of water corresponding to the depth at which they are disposed. The data are acquired by moving the naval ship along an axis perpendicular to the axis joining the two magnetometers and equidistant from the latter, the * .3..
ship moving at a constant speed preferably corresponding to its maximum speed.
Because portable stations of this type comprise only two sensors, the associated magnetic compensation is not very accurate. tn fact, this small number of sensors does not allow the acquisition of a sufficient number of parameters to refine the computation of the various components of the magnetisation of the ship, particularly under its keel.
Furthermore, the use of this portable station is difficult since the relative position of the inagnetome-ters used must be known. The quality of the magnetic compensation carried out is considerably inferior to the quality obtained using land measuring stations.
The invention proposes overcoming these various disadvantages of the prior art and proposes the produc-tion of a portable station for measuring the magnetic signature of a naval ship allowing the provision of results equivalent to the results obtained using fixed land-based magnetic measuring stations and which can be deployed rapidly.
Another purpose of the invention is to produce a portable station in which the location of the magnetic sensors can be determined freely.
Another purpose of the invention is to provide a portable station which can be retrieved easily after use.
To this end, the invention consists in producing a portable station which comprises on-board computing means comprising a magnetic model of the naval ship whose parameters are determined from measurements taken by magnetic sensors. The theoretical field is then computed throughout the surrounding space of the naval ship and in particular under the keel of this naval ship. In order to take the measurements, the portable station comprises at least two measuring sets intended to be deployed on either side of the naval ship. Each measuring set com-prises at least two magnetometers connected to each other and to a buoy by cables. When the station is deployed, the magnetometers of each measuring set are disposed vertically, one above the other, and kept at a constant depth of immersion, their spacing being freely deter-mined.
According to the invention, the portable station S for measuring and adjusting the magnetic signature of a naval ship provided with magnetic inununisation loops is characterised in that it comprises at least two measuring sets intended to be deployed at sea on either side of the naval ship, each measuring set comprising at least two magnetic sensors disposed vertically, one above the other in each case, and means for transmitting measurements, and in that the naval ship is equipped with means for receiving measurements and means for computing the theo-retical magnetic field, the computing means comprising a magnetic model of the naval ship allowing computation of
the magnetic field under the naval ship.
Other features and advantages of the invention will appear clearly in the following description given by way of non-limitative example with reference to the accompanying figures in which: -Figure 1 is a diagram of a first illustrative embodiment of a portable station for measuring the magnetic signature of a naval ship, according to the invention; -Figure 2 is a diagram of a second illustrative portable station for measuring the magnetic signature of a naval ship, according to the invention; -Figure 3 is a flow chart of a method for optirnising a model of the naval ship,in operation of the invention.
Figures 1 and 2 show two illustrative embodiments of a portable station for measuring the magnetic signa-ture of a naval ship. A naval ship 1 operates in an environment likely to present a.
risk of detection of its magnetic signature. The ship is provided with a suite of irnmunisation loops (not shown) which carry adjustable electric currents.
In order to adjust the value of the currents allowing the magnetic signature of the naval ship to be : a5e minimised, a portable measuring station is deployed close to the naval ship. This measuring station comprises at least two measuring sets comprising magnetometers Cl to Cn and C'l to C'n disposed vertically, one above the other, and connected by cable to floating buoys 10, 11, these two sets being deployed on either side of the naval ship in such a way as to delimit a navigation channel.
The number n of magnetometers per measuring set is determined according to the desired accuracy of immunisation. However, it is necessary for there to be at least two magnetometers per measuring set. Each measuring set is associated with an electronic unit 16, 17 which processes the signals coming from the magnetometers so that they can be transmitted, for example, in the form of VHF radio waves, to the naval ship. To this end, each buoy 10, 11 is provided with transmission means 18, 19.
The distance separating the two measuring sets is equal to at least twice the depth of water corresponding to the depth of immersion of each measuring set.
According to a first illustrative embodiment shown in Figure 1, the magnetometers Cl to Cn, or C'l to C'n respectively, of a same measuring set and the elec-tronic unit 16, or 17 respectively, which is associated with them, are installed in a container 25, or 35 respec-tively, with positive buoyancy which is kept at a given distance from the sea bed by means of a kentledge 26, 36 fixed to the sea bed. The electronic unit 25, 35 is connected to the kentledge 26, 36 and to the surface buoy 10, 11 by means of a cable 28, 38 In order to retrieve the measuring sets, an explosive attachment 29, 39 is disposed at the point of thonnection of the cable 28, 38 with the kentledge 26, 36. This explosive attachment is remote-controlled in order to disconnect the container from the kentledge.
According to a second illustrative embodiment shown in Figure 2, each measuring set is suspended from a floating buoy 10, 11 in such a way as to maintain a predetermined and fixed depth of immersion.
The magnetometers of a same set are connected to ads each other and to the buoy by a cable 12, 13 provided with ballasting means 14, 15, these ballasting means ensuring verticality of the magnetometers with respect to the ship.
The naval ship is equipped with means for receive ing data transmitted by the transmitting means, and comprises means f or computing the magnetic field. The computing means comprise a magnetic model of the ship allowing, on the basis of the magnetic field values measured by the magnetometers at predetermined points, computation of the magnetic field radiated throughout the surrounding space of the naval ship and, in particular, under the keel of the ship.
The magnetic model of the naval ship is deterS mined prior to the ship setting sail. By way of example of a magnetic model, the naval ship can be represented by a set of point magnetic sources dipoles or ellipsoids).
The optimum location of these sources is determined in an iterative manner according to Figure 3. In step 40, the location of the sources is initialised. This location is chosen empirically. In step 41, the theoretical magnetic field is computed at different places corresponding to the measuring points by the solving of a system of m equations (m being the number of magnetic measurements).
In step 42, a modelling error is computed by comparing
the computed values of the magnetic field with the
measured values. In step 43, the modelling error is compared with a predetermined threshold value SI. If the error is greater than the threshold value SI, the sources ao are displaced in a random manner in step 44 and steps 41 to 43 are repeated until the difference between the computed and measured values of the magnetic field is less than the predetermined threshold Si. If the error is less than the threshold Si, the iterative procedure is complete.
The accuracy of the computation of the magnetic field depends on the accuracy of the knowledge of the position of the magnetometers with respect to the naval ship. The verticality of the sensors being ensured, it suffices to know the position of the buoys. The position of the buoys can be determined, for example, using optical means by placing a laser on the naval ship and a reflector on each buoy and carrying out optical sight.n ings; it can also be determined by other means such as, for example, acoustic means with a hydrophone installed on the naval ship and a sonic bleep on each of the buoys, or by radio means (VHF signals).
The functioning of the station for measuring and adjusting the magnetic signature of a naval ship is as follows.
The magnetometers measure the vertical component of the magnetic field at their location points. The other components of the magnetic field can also be measured, if necessary, using triaxial magnetometers. The measurements are taken by moving the naval ship in the navigation channel delimited by the two measuring sets and along an axis perpendicular to the axis connecting the two buoys of each measuring set. The movement of the naval ship preferably takes place at a constant speed and equi- distant from the two buoys of each set. These measure-ments are processed by the electronic units 16, 17 and transmitted by the transmitting means to the receiving and computing means installed on board the naval ship.
The computing means compute the theoretical magnetic field at various places corresponding to the measuring points and compare the values obtained with the measured values. If the difference between the theoreti-cal and measured values is less than a predetermined threshold 52, the computing means compute the magnetic field under the keel of the ship at a given depth, for example 9 to.10 m, and modify, it necessary, the value of the currents to be caused to flow in the linmunisation loops in order to reduce the magnetic signature of the naval ship. If the difference between the theoretical and measured values is greater than the predetermined threshold $2, the magnetic model of the ship is modified by randomly and iteratively changing the position of the point magnetic sources until the difference between the theoretical and measured values is less than the threshold Si. The magnetic field under the keel of the ship is then computed with the new magnetic model and the currents to be caused to flow in the ixnmunisation loops are modified in order to reduce the magnetic signature of the naval ship.
The present invention is not limited to the previously described illustrative embodiments1 in par-ticular, the magnetometers used are uniaxial and measure only the vertical component of the magnetic field, but it is possible to use triaxial magnetic sensors and to measure three components of the magnetic field along three orthogonal directions. The number of magnetometers per measuring set is not limited and their location is chosen in any manner; it suffices that there be at least two magnetometers per measuring set and that these be disposed vertically one above the other in each case.
Similarly, there can be more than two measuring sets.
Finally, this type of portable station can be used as a fixed station, the mounting and adjusting of the magnetometers for each set being carried out in the factory. The number of operations required for installa-tion and adjustment on site is then reduced without reducing the number of magnetometers. H.
Claims (5)
1. A portable station for measuring and adjusting the H magnetic signature of a naval ship provided with magnetic immunisation loops, comprising at least two measuring sets intended to be deployed at sea on either side of the naval ship, each measuring set comprising at least two magnetic sensors disposed vertia cally, one above the other in each case, and means for transmitting measurements, the naval ship beingeguipped with means for receiving measurements and means ± or computing the theoretical magnetic field, the computing means comprising a magnetic model of the naval ship allowing computation of the magnetic field radiated under the naval ship.
2. A portable station according to Claim 1, wherein the magnetometers of a same set are installed in a container with positive buoyancy, the container being connected to a surface buoy-.
3. A Portable station according to Claim 1, wherein the magnetometers of a same set are connected to each other and to a surface buoy by a cable provided with ballasting means.
4. A portable station according to any one of the preceding claims, wherein the magnetic model of the ship is a set of point magnetic sources whose optimum location is determined iteratively on the basis of measurements taken by the magnetometers.
5. A portable station for measuring and adjusting the magnetic signature of a naval ship provided with magnetic immunization loops, substantially as described hereinbefore with reference to the accompanying drawings and as shown in Figure 1, Figure 2 or Figure 3 of those drawings. !0Amendments to the claims have been filed as follows 1. A mobile arrangement for measuring and adjusting the magnetic signature of a naval ship provided with magnetic invru.inisation loops, comprising at least two ireasurinc sets intended to be deployed at sea on either side of the naval ship, each measuring set comprising at least two magnetic sensors disposed vertically, one above the other in each case, means for transmitting measurements from the measuring sets and receiving means operable to receive signals transmitted from said transmitting means, said receiving means to be located on the ship In use of the arrangement, said arrangement further comprising means for computing a theoretical magnetic field to be located on the ship in use of the arrangement, comprising a magnetic model of the ship which allows the magnetic field radiated under the naval ship to be computed, means for comparing the computed magnetic field and the measured magnetic field, and means operable to adjust current in the immunisation loops, wherein the means for computing the theoretical magnetic field and the means for comparing the computed magnetic field and the treasured magnetic field are operable to cooperate to enure that the theoretical magnetic field is within a preselected limit of the measured magnetic field, and the means operable to adjust the current in the ijununisation loops adjusts the current in a way which takes into account the theoretical magnetic field, and reduces the magnetic signature of the ship.2. A mobile arrangement according to claim 1, wherein the magnetometers of a same set are installed in a container with positive buoyancy, the container being connected to a surface buoy.3. A mobile arrangement according to claim 1, wherein the magnetometers of a same set are connected to each other and to a surface buoy by a cable provided with ballasting means.4. A mobile arrangement according to any one of the preceding claims, wherein the magnetic model of the ship is a set of point magnetic sources whose otpimurn location is determined iteratively on the basis of measurements taken by the magnetometers.5. A mobile arrangement for measuring and adjusting the magnetic signature of a naval ship provided with magnetic immunisation loops, substantially as described hereiribefore with reference to the accompanying drawings and as shown in Figure 1 and 3, or Figure 2 and 3 of those drawings.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR9205054 | 1992-04-24 |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB9308296D0 GB9308296D0 (en) | 2011-04-20 |
| GB2488963A true GB2488963A (en) | 2012-09-19 |
| GB2488963B GB2488963B (en) | 2013-03-06 |
Family
ID=43923171
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9308296.4A Expired - Fee Related GB2488963B (en) | 1992-04-24 | 1993-04-22 | A mobile arrangement for measuring and adjusting the magnetic signature of a naval ship |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2488963B (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| RU2551412C1 (en) * | 2013-12-30 | 2015-05-20 | Федеральное государственное унитарное предприятие "Крыловский государственный научный центр" (ФГУП "Крыловский государственный научный центр") | Mobile test bench for measurement and configuring of magnetic field of supermarine or submarine object |
| RU2606649C2 (en) * | 2015-05-18 | 2017-01-10 | Российская Федерация, От Имени Которой Выступает Министерство Промышленности И Торговли Российской Федерации | Method of surface or underwater object magnetic field parameters measuring on stationary magnetic test bench |
| RU2619481C1 (en) * | 2016-04-08 | 2017-05-16 | Российская Федерация, От Имени Которой Выступает Министерство Промышленности И Торговли Российской Федерации | Maneuverable stand for measuring and adjustment the magnetic field of marine facilities |
| RU208300U1 (en) * | 2021-05-05 | 2021-12-13 | Публичное Акционерное Общество "Корпорация Всмпо-Ависма" | INSTALLATION FOR MONITORING THE DISTRIBUTION OF THE MAGNETIC FIELD ON THE SHELL OF THE CRYSTALLIZER OF THE VACUUM ARC FURNACE |
| RU2789914C1 (en) * | 2022-04-11 | 2023-02-14 | Федеральное государственное унитарное предприятие "Крыловский государственный научный центр" | Maneuverable stand for measuring and adjusting the magnetic field of marine equipment objects |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1987002324A1 (en) * | 1985-10-18 | 1987-04-23 | The Secretary Of State For Defence In Her Britanni | A magnetic self-ranging system for use in the degaussing of ships |
| US4808923A (en) * | 1983-08-04 | 1989-02-28 | Thomson Csf | System for calculating the path of a naval vessel |
-
1993
- 1993-04-22 GB GB9308296.4A patent/GB2488963B/en not_active Expired - Fee Related
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4808923A (en) * | 1983-08-04 | 1989-02-28 | Thomson Csf | System for calculating the path of a naval vessel |
| WO1987002324A1 (en) * | 1985-10-18 | 1987-04-23 | The Secretary Of State For Defence In Her Britanni | A magnetic self-ranging system for use in the degaussing of ships |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| RU2551412C1 (en) * | 2013-12-30 | 2015-05-20 | Федеральное государственное унитарное предприятие "Крыловский государственный научный центр" (ФГУП "Крыловский государственный научный центр") | Mobile test bench for measurement and configuring of magnetic field of supermarine or submarine object |
| RU2606649C2 (en) * | 2015-05-18 | 2017-01-10 | Российская Федерация, От Имени Которой Выступает Министерство Промышленности И Торговли Российской Федерации | Method of surface or underwater object magnetic field parameters measuring on stationary magnetic test bench |
| RU2619481C1 (en) * | 2016-04-08 | 2017-05-16 | Российская Федерация, От Имени Которой Выступает Министерство Промышленности И Торговли Российской Федерации | Maneuverable stand for measuring and adjustment the magnetic field of marine facilities |
| RU208300U1 (en) * | 2021-05-05 | 2021-12-13 | Публичное Акционерное Общество "Корпорация Всмпо-Ависма" | INSTALLATION FOR MONITORING THE DISTRIBUTION OF THE MAGNETIC FIELD ON THE SHELL OF THE CRYSTALLIZER OF THE VACUUM ARC FURNACE |
| RU2789914C1 (en) * | 2022-04-11 | 2023-02-14 | Федеральное государственное унитарное предприятие "Крыловский государственный научный центр" | Maneuverable stand for measuring and adjusting the magnetic field of marine equipment objects |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2488963B (en) | 2013-03-06 |
| GB9308296D0 (en) | 2011-04-20 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 20130606 |