EP0217712A1 - Demagnetizing device, particularly for ships - Google Patents

Demagnetizing device, particularly for ships Download PDF

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Publication number
EP0217712A1
EP0217712A1 EP86402086A EP86402086A EP0217712A1 EP 0217712 A1 EP0217712 A1 EP 0217712A1 EP 86402086 A EP86402086 A EP 86402086A EP 86402086 A EP86402086 A EP 86402086A EP 0217712 A1 EP0217712 A1 EP 0217712A1
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EP
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Prior art keywords
conductors
magnetization
value
ship
capacitors
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EP86402086A
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German (de)
French (fr)
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EP0217712B1 (en
Inventor
Germain Guillemin
Jean-Jacques Periou
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Thales SA
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Thomson CSF SA
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    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F13/00—Apparatus or processes for magnetising or demagnetising
    • H01F13/006—Methods and devices for demagnetising of magnetic bodies, e.g. workpieces, sheet material

Definitions

  • the invention relates to a demagnetization device for canceling or modifying the magnetization of an object, in particular a naval vessel, an airplane, or a combat tank.
  • This disturbance is called the magnetic signature of this object and is used in the military field for the detection of this object. It is in particular a phenomenon used for the detection of submarines and for the triggering of mines. It is therefore of great interest to minimize the disturbance of the Earth's magnetic field caused by military vehicles, in particular submarines and ships.
  • the magnetization of a ship for example, consists of a permanent magnetization which is independent of the place where the ship is located and of the orientation of the ship relative to the Earth's magnetic field, and of a magnetization induced by the terrestrial magnetic field and which is a function of the place where the ship is located and its orientation relative to the terrestrial magnetic field. It is not possible to definitively and completely neutralize the magnetization of a ship because of the variations of the terrestrial magnetic field according to the place and because of the movements of the ship in this field. On the other hand, the magnetization of a very large object such as a ship is not evenly distributed in this object, therefore it should be neutralized at each point of the ship to obtain a zero magnetic signature. In practice, it is therefore not possible to completely cancel the magnetic signature of a ship. In the best case, it is possible to cancel its vertical component by creating a vertical magnetization exactly compensating for the vertical component of the magnetization induced by the earth's magnetic field, and it is possible to reduce its horizontal components by canceling the horizontal components of permanent magnetization.
  • a device of the first type constitutes a large installation located in a port and makes it possible to treat different ships at regular intervals.
  • a device of the second type makes it possible to permanently neutralize the magnetic signature of a ship by opposing to it a variable magnetic field as a function of the geographic position of the ship and as a function of its attitude with respect to the earth's magnetic field.
  • This second type of device is efficient but expensive in material and energy.
  • Ships fitted with a magnetic immunization device are also periodically treated in a demagnetization station to reduce their permanent magnetization to a perfectly defined value, which facilitates the adjustment of their magnetic immunization device and makes it possible to reduce its consumption. of energy.
  • the device according to the invention is a device of the first type.
  • a first known device comprises: a current pulse generator; conductors connected to this generator and forming turns surrounding the ship by forming a solenoid whose major axis corresponds to the major axis of the vessel; and magnetometers placed at the bottom of the sea to measure the magnetization of the ship.
  • An operator manually controls the current pulse generator according to the measurements provided by the magnetometers.
  • the current pulses have a duration of the order of 30 seconds each, an alternately positive and negative polarity, and a decreasing amplitude from a value of approximately 4000 amperes.
  • the intensity of the current is constant and it is supplied by a rectifying device receiving its energy from the public electrical network.
  • This device has the disadvantage of a very long implementation time because it takes several days to set up and interconnect the conductors, which are large very heavy cables, and because it then takes a day of treatment to obtain demagnetization.
  • this device requires an electrical installation of very large power, of the order of a megawatt, because it consumes a very high power for the duration of the current pulses. During the rest of the time, the high-power electrical installation has no use.
  • a second known device comprises: conductors placed at the bottom of the sea and forming turns having a vertical axis, and a sinusoidal alternating current generator having a frequency of the order of 1 Hz and an intensity of several thousand amps.
  • the demagnetizing vessel passes over these turns in order to approach and then move away from them.
  • the growth then the decrease of the magnetic field caused by the approaching then the distance of the ship realize a neutralization of the three components of the magnetization of this ship.
  • This device also requires a high-power electrical installation because of the large size of the turns, for example 20 m ⁇ 20 m, and because of their distance from the ship.
  • demagnetization can be badly done if the ship does not pass exactly in the plane of symmetry of the turns, and this device only allows demagnetization: it does not allow to apply a determined magnetization to neutralize the vertical component of l magnetization induced by the Earth's magnetic field.
  • a third known device comprises conductors forming turns folded in the shape of a double U surrounding a portion of the hull of the ship and moved continuously along this hull for a time interval of the order of six minutes; and a generator of alternating positive and negative current pulses, having a frequency of the order of 0.5 Hz.
  • This device is generally used to treat small boats, with an electrical power involved greater than 200 kw.
  • this device does not make it possible to apply a determined magnetization to also compensate for the vertical component of the magnetization induced in the ship by the terrestrial magnetic field.
  • the object of the invention is to provide a demagnetization device requiring an electrical installation of lower power than the known devices, in order to lower the cost of this electrical installation; reducing the processing time for each vessel; and making it possible to create a permanent magnetization determined to neutralize the vertical component of the magnetization induced in the ship by the terrestrial magnetic field.
  • the device comprises: a capacitor bank which is charged slowly by a relatively low power electrical installation and which is discharged quickly, in a few hundred milliseconds; electrical conductors forming turns much smaller than the length of the ship, for localized treatment of each portion of the ship; and a control device for automating the processing, by controlling the charge voltage of the capacitors and the direction of the discharge current as a function of the magnetization measured by magnetometers, and as a function of a set value.
  • a demagnetization device in particular for ships, comprising conductors forming turns placed near an object to be demagnetized and a generator for injecting current pulses into these conductors, comprising: - capacitors; - Means for charging these capacitors at a determined voltage; - means for discharging the capacitors in the conductors, characterized in that it further comprises at least one magnetometer for measuring the magnetization of the object, and means for controlling the charge voltage of the capacitors as a function of the magnetization of the object to be demagnetized.
  • the exemplary embodiment shown in FIG. 1 is intended to demagnetise a ship 1 in the horizontal directions and to impart to it a predetermined magnetization, not zero, in the vertical direction in order to compensate for the magnetization induced by the terrestrial magnetic field.
  • This example comprises conductors 2 to 6 forming three sets of turns whose axes are orthogonal two by two; five magnetometers 7 to 11; an input terminal 16 connected to a public electrical distribution network; a generator 17 of direct current; a capacitor bank 18; a bridge switching device 19; an inductor 20; a switch 21 with two inputs and six outputs; a device 22 for controlling the charging voltage of the capacitor bank 18; a computing device mainly consisting of a microprocessor 23; a screen and a keyboard 24.
  • the vessel 1 is treated in portions of a length of the order of 20 meters.
  • the conductors are moved to treat a neighboring portion or the ship is moved relative to these conductors.
  • the device makes it possible to carry out demagnetization successively along three orthogonal axes corresponding to the three axes of the sets of turns.
  • the screen and the keyboard 24 make it possible to supply the demagnetization device with a set value determining the desired residual magnetization in the vertical direction to compensate for the magnetization induced by the earth's magnetic field.
  • a first set of turns is formed of conductors 6 installed at the bottom of the sea and forming a square of 20m ⁇ 20m.
  • a second set of turns consists of two halves symmetrical with respect to the longitudinal axis of the ship 1 and formed of square turns of 20m ⁇ 20m whose plane is parallel to the plane of symmetry of the ship and which are located near the sides of that -this.
  • a third set of conductors 4 and 5 is located in a plane perpendicular to the longitudinal axis of the ship and passing through the centers of the turns formed by conductors 2, 3 and 6. This third set of conductors comprises incomplete square turns formed by the conductors 4 and other incomplete square turns formed by the conductors 5 and intended to close the circuits of the conductors 4.
  • the conductors 4 form three sides of square turns of dimensions 20m ⁇ 20m, the upper side missing. All of the conductors 5 form incomplete square turns distant from the conductors 4 so as not to counter the magnetic field created by the conductors 4.
  • the conductors 4 are intended to create a magnetic field in the direction of the longitudinal axis of the ship 1
  • the conductors 2 and 3 are intended to create a magnetic field in the direction of the transverse axis of the ship 1.
  • the conductors 6 are intended to create a magnetic field in the vertical direction.
  • the switch 21 receives on its two inputs current pulses which it transmits to one of the sets of conductors according to a selection signal applied to a control input by microprocessor 23.
  • the five magnetometers 7 to 11 make it possible to measure the magnetic field created by the magnetization of the ship 1.
  • Each magnetometer provides three measurement signals corresponding respectively to three components of the magnetic field, orthogonal two by two and parallel to the directions of the three magnetic fields created respectively by the three sets of conductors.
  • the magnetometers are integral with the three sets of conductors and are located below the vessel, at a level below the horizontal part of the turns formed by the conductors 4.
  • the lower part of the turns formed by the conductors 4 , the lower part of the turns formed by conductors 2 and 3, and all of the turns formed by conductors 6 are located in the same plane which is lower than the keel of the ship.
  • the magnetometer 7 is placed on the axis of symmetry of the turns formed by the conductors 6, and the other four magnetometers are located at the same distance, of the order of 15m, from the magnetometer 7 and are in a horizontal passing plane by this one.
  • the magnetometers 8 and 10 are located on a straight line passing through the magnetometer 7 and parallel to the ship's longitudinal axis while the magnetometers 9 and 11 are located on a straight line passing through the magnetometer 7 and perpendicular to this axis.
  • the screen and the keyboard 24 are coupled to the microprocessor 23 to receive information to be displayed on the screen and to transmit the orders given by the operator by typing on the keyboard.
  • the microprocessor 23 has a multiple input coupled to the magnetometers 7 to 11 to receive their measurement signals, and an input connected to an output of the device 22 providing a logic signal when the capacitor bank 18 is sufficiently charged. It has an output connected to a control input of the device 22 for controlling the charging voltage to provide it with a value signal V o determining the charging voltage of the capacitor bank 18; an output providing a binary word P to a control input of the bridge switching device 19, to trigger the passage of current in the sets of conductors 2 to 6 with a chosen direction, by controlling the closing of two branches of the bridge.
  • the generator 17 receives the electrical energy supplied at 16 by the public network. It has two outputs connected respectively to two inputs of the capacitor bank 18. This has two outputs connected respectively to two inputs of the device 19 and to two inputs of the servo device 22.
  • the device 19 is a bridge switching device, produced for example by means of thyristors. It has two outputs connected respectively to a first terminal of the inductor 20 and to a first input of the switch 21. A second terminal of the inductor 20 is connected to a second input of the switch 21.
  • the switch 21 can be achieved by means thyristors, according to conventional techniques.
  • the device 22 for controlling the charging voltage of the capacitor bank 18 has an output connected to a control input of the generator 17 for charging the capacitor bank 18 at a voltage corresponding to the value V o of the signal supplied by the microprocessor 23. This charge is carried out approximately at constant current.
  • the device 22 sends a logic signal to the microprocessor 23 and the latter can then trigger the sending of a current pulse in one of the sets of conductors by controlling the device 19.
  • the discharge circuit of the capacitor bank 18 is constituted by the device 19, the inductor 20, the switch 21, and the ohmic resistance of the set of conductors which is put into the circuit by means of the switch 21.
  • the inductance of the conductors constituting the turns is negligible compared to the value of the inductance 20 and the presence of the vessel 1 near the conductors has little influence on the total inductance of the circuit.
  • the current pulse obtained is not rectangular but its duration can nevertheless be defined by considering the time interval during which the current intensity is equal to i max minus 3dB. This duration is equal to 1.7. ⁇ .
  • a period of the order of a few hundred milliseconds is necessary to obtain an effective demagnetization treatment. For example, 500 ms is a duration achieving a good compromise between the efficiency of demagnetization and the electrical energy necessary to create this current pulse.
  • the maximum intensity is equal to 31.12.CV o . If this maximum intensity is set at 1000 amperes, the initial charge CV o of the capacitor bank 18 is equal to 800 coulombs. For an end-of-charge voltage equal to 1000 volts, the capacity C must then have the value 0.8 0.8 Farads. In an exemplary embodiment, the charging time to obtain this voltage is equal to 1.5 minutes and the initial charging current has an intensity of 50 amps. The electrical power supplied by the installation is therefore of the order of 50 kw during the charging of the capacitor bank 18.
  • the device according to the invention can of course operate with a damping greater or less than the critical damping.
  • the pulses of maximum efficiency are obtained when the discharge circuit has a damping close to the critical damping.
  • each portion of the ship is treated along three axes in succession.
  • demagnetization simultaneously along three axes by providing three independent capacitor banks, three independent charging devices and three independent discharge devices, controlled in parallel by the same calculation device.
  • the magnetometers 7 to 11 make it possible to measure the magnetization of the portion of the ship being processed.
  • the magnetometers 8 and 10 make it possible to take account respectively of the magnetization of the portion which has been treated immediately previously and of the magnetization of the portion which will be treated immediately after.
  • the magnetometers 9 and 11, which are offset transversely with respect to the magnetometer 7, make it possible to take account of the non-homogeneity of the magnetization in the portion of the ship being processed.
  • the processing of a portion of a ship begins with the measurement of its magnetization.
  • the measurement signals supplied by the magnetometers 7 to 11 allow the calculation device 23 to determine, for the three directions, the polarity and the intensity i max of the current for a first demagnetization pulse. This intensity is proportional to the magnetization measured in the corresponding direction.
  • the formula (2) makes it possible to correspond to i max a value V o of the end of charge voltage of the capacitor bank 18. When this charge voltage is reached the servo device 22 supplies a logic signal to the microprocessor 23 The latter can then trigger the discharge.
  • the microprocessor 23 determines an intensity value i max for a second demagnetization pulse and deduces therefrom the value V o of the end of charge voltage of the capacitor bank 18.
  • the device servo 22 warns the microprocessor 23 which can then trigger the discharge of a second pulse. This sequence is repeated until the magnetization, in the direction considered, has been brought back to the set value set by the operator. This setpoint is zero for the horizontal components and not zero for the vertical component.
  • the value of the vertical component of the permanent magnetization is chosen according to the region where the ship is to sail.
  • the magnetization of the portion of the vessel to be treated is estimated from measurements of the magnetic field, in three directions, by the five magnetometers 8 to 11, assuming that the barycenter of the magnetic masses corresponds to the barycenter G of the ship's hull.
  • the components Mx, My, Mz of the magnetization at this point G are linked to the values B x , B y , B z of the magnetic field measured by one of the magnetometers, by the known relationships: where x, y, z are the coordinates of the magnetometer in an orthonormal coordinate system located in G and where r is the distance between the magnetometer and the point G.
  • this coefficient is determined by a very rough calculation or by a test, in each of the three directions. It is stored in the microprocessor's memory. The imprecision of this coefficient is not a problem since the device demagnetizes the portion of the ship by successive approximations by making the horizontal components of the magnetization tend towards zero and by making the vertical component tend towards the set value.
  • k x , k y , k z are three constant coefficients corresponding respectively to the two horizontal directions and to the vertical direction.
  • the constant C is a non-zero reference value supplied by the operator by means of the keyboard 24 to obtain a determined vertical component.
  • the sequence of the current pulses for processing each portion of the ship can be controlled automatically by the microprocessor 23, without the intervention of an operator, or else the microprocessor 23 can wait for an order given by the operator before triggering each pulse.
  • the microprocessor 23 can display on the screen 24 the values of the measured magnetization, to allow the operator to monitor the progress of the demagnetization treatment.

Abstract

L'invention concerne les dispositifs de désaimantation utilisés notamment pour désaimanter des navires ou des sous-marins dans des stations fixes. Un exemple de réalisation comporte trois ensembles de conducteurs (2 à 6) pour démagnétiser un navire (1) selon trois directions ; un générateur de courant continu (17) ; une batterie de condensateurs (18) ; un dispositif (19) de commutation en pont ; une inductance (20) ; un commutateur (21) permettant de sélectionner l'un des trois ensembles de conducteurs ; un dispositif (22) d'asservissement de la tension de charge de la batterie de condensateurs (18) ; des magnétomètres (7 à 11) ; et un écran-clavier (24) permettant notamment de fournir à un microprocesseur (23) une valeur de consigne fixant la valeur de l'aimantation résiduelle souhaitée. La désaimantation consiste à envoyer dans chaque ensemble de conducteurs une suite de décharges, d'intensité de plus en plus petite et asservie à la valeur de l'aimantation restante, pour faire converger l'aimantation vers la valeur souhaitée. Application à la désaimantation de navires, sous-marins, avions, chars, etc.The invention relates to demagnetization devices used in particular for demagnetizing ships or submarines in fixed stations. An exemplary embodiment comprises three sets of conductors (2 to 6) for demagnetizing a ship (1) in three directions; a direct current generator (17); a capacitor bank (18); a bridge switching device (19); an inductor (20); a switch (21) for selecting one of the three sets of conductors; a device (22) for controlling the charging voltage of the capacitor bank (18); magnetometers (7 to 11); and a keyboard screen (24) making it possible in particular to supply a microprocessor (23) with a set value fixing the value of the desired residual magnetization. The demagnetization consists in sending in each set of conductors a series of discharges, of increasingly smaller intensity and subject to the value of the remaining magnetization, in order to make the magnetization converge towards the desired value. Application to demagnetization of ships, submarines, planes, tanks, etc.

Description

L'invention concerne un dispositif de désaimantation pour annuler ou modifier l'aimantation d'un objet, notamment un bâtiment naval, un avion, ou un char de combat.The invention relates to a demagnetization device for canceling or modifying the magnetization of an object, in particular a naval vessel, an airplane, or a combat tank.

L'aimantation que possède un tel objet perturbe le champ magné­tique terrestre. Cette perturbation est appelée signature magnétique de cet objet et est exploitée dans le domaine militaire pour la détection de cet objet. C'est notamment un phénomène utilisé pour la détection des sous-marins et pour le déclenchement des mines. Il est donc d'un grand intérêt de réduire le plus possible la perturbation du champ magnétique terrestre causée par les véhicules militaires, notamment les sous-marins et les navires.The magnetization that such an object has disrupts the earth's magnetic field. This disturbance is called the magnetic signature of this object and is used in the military field for the detection of this object. It is in particular a phenomenon used for the detection of submarines and for the triggering of mines. It is therefore of great interest to minimize the disturbance of the Earth's magnetic field caused by military vehicles, in particular submarines and ships.

L'aimantation d'un navire, par exemple, est constituée d'une aimantation permanente qui est indépendante du lieu où est situé le navire et de l'orientation du navire par rapport au champ magnétique terrestre, et d'une aimantation induite par le champ magnétique terrestre et qui est fonction du lieu où est situé le navire et de son orientation par rapport au champ magnétique terrestre. Il n'est pas possible de neutraliser définitive­ment et complètement l'aimantation d'un navire à cause des variations du champ magnétique terrestre en fonction du lieu et à cause des mouve­ments du navire dans ce champ. D'autre part, l'aimantation d'un très gros objet tel qu'un navire n'est pas répartie uniformément dans cet objet, par conséquent elle devrait être neutralisée en chaque point du navire pour obtenir une signature magnétique nulle. En pratique, il n'est donc pas possible d'annuler totalement la signature magnétique d'un navire. Dans le meilleur des cas, il est possible d'annuler sa composante verticale en créant une aimantation verticale compensant exactement la composante verticale de l'aimantation induite par le champ magnétique terrestre, et il est possible de réduire ses composantes horizontales en annulant les composantes horizontales de l'aimantation permanente.The magnetization of a ship, for example, consists of a permanent magnetization which is independent of the place where the ship is located and of the orientation of the ship relative to the Earth's magnetic field, and of a magnetization induced by the terrestrial magnetic field and which is a function of the place where the ship is located and its orientation relative to the terrestrial magnetic field. It is not possible to definitively and completely neutralize the magnetization of a ship because of the variations of the terrestrial magnetic field according to the place and because of the movements of the ship in this field. On the other hand, the magnetization of a very large object such as a ship is not evenly distributed in this object, therefore it should be neutralized at each point of the ship to obtain a zero magnetic signature. In practice, it is therefore not possible to completely cancel the magnetic signature of a ship. In the best case, it is possible to cancel its vertical component by creating a vertical magnetization exactly compensating for the vertical component of the magnetization induced by the earth's magnetic field, and it is possible to reduce its horizontal components by canceling the horizontal components of permanent magnetization.

On distingue deux types de dispositifs permettant de réduire la signature magnétique d'un navire : des dispositifs indépendants des navires et appelés stations de démagnétisation et des dispositifs embarqués sur les navires, appelés dispositifs d'immunisation magnétique. Un dispositif du premier type constitue une grosse installation située dans un port et permet de traiter différents navires à intervalles réguliers.There are two types of device used to reduce the magnetic signature of a ship: devices independent of ships and called demagnetization stations and devices on board ships, called magnetic immunization devices. A device of the first type constitutes a large installation located in a port and makes it possible to treat different ships at regular intervals.

Un dispositif du second type permet de neutraliser en permanence la signature magnétique d'un navire en lui opposant un champ magnétique variable en fonction de la position géographique du navire et en fonction de son attitude par rapport au champ magnétique terrestre. Ce second type de dispositifs est efficace mais coûteux en matériel et en énergie. Les navires équipés d'un dispositif d'immunisation magnétique sont en outre traités périodiquement dans une station de démagnétisation pour ramener leur magnétisation permanente à une valeur parfaitement défi­nie, ce qui facilite le réglage de leur dispositif d'immunisation magnétique et permet de réduire sa consommation d'énergie.A device of the second type makes it possible to permanently neutralize the magnetic signature of a ship by opposing to it a variable magnetic field as a function of the geographic position of the ship and as a function of its attitude with respect to the earth's magnetic field. This second type of device is efficient but expensive in material and energy. Ships fitted with a magnetic immunization device are also periodically treated in a demagnetization station to reduce their permanent magnetization to a perfectly defined value, which facilitates the adjustment of their magnetic immunization device and makes it possible to reduce its consumption. of energy.

Le dispositif selon l'invention est un dispositif du premier type. On connaît plusieurs dispositifs constituant des stations de démagnétisation pour navires. Un premier dispositif connu comporte : un générateur d'impulsions de courant ; des conducteurs reliés à ce générateur et formant des spires entourant le navire en formant un solénoïde dont le grand axe correspond au grand axe du navire ; et des magnétomètres placés au fond de la mer pour mesurer l'aimantation du navire. Un opérateur commande manuellement le générateur d'impulsions de courant en fonction des mesures fournies par les magnétomètres. Les impulsions de courant ont une durée de l'ordre de 30 secondes chacune, une polarité alternativement positive et négative, et une amplitude décroissante à partir d'une valeur de 4000 ampères environ. Pendant la durée de chaque impulsion l'intensité du courant est constante et elle est fournie par un dispositif de redressement recevant son énergie à partir du réseau électrique public. Ce dispositif a pour inconvénient une durée de mise en oeuvre très longue parce qu'il faut plusieurs jours pour mettre en place et interconnecter les conducteurs, qui sont des gros câbles très lourds, et parce qu'il faut ensuite une journée de traitement pour obtenir une désaimantation. En outre, ce dispositif nécessite une installation électri­que de très grosse puissance, de l'ordre d'un mégawatt, parce qu'il consomme une très forte puissance pendant la durée des impulsions de courant. Pendant le reste du temps l'installation électrique de grande puissance n'a aucune utilité.The device according to the invention is a device of the first type. Several devices are known which constitute demagnetization stations for ships. A first known device comprises: a current pulse generator; conductors connected to this generator and forming turns surrounding the ship by forming a solenoid whose major axis corresponds to the major axis of the vessel; and magnetometers placed at the bottom of the sea to measure the magnetization of the ship. An operator manually controls the current pulse generator according to the measurements provided by the magnetometers. The current pulses have a duration of the order of 30 seconds each, an alternately positive and negative polarity, and a decreasing amplitude from a value of approximately 4000 amperes. During the duration of each pulse the intensity of the current is constant and it is supplied by a rectifying device receiving its energy from the public electrical network. This device has the disadvantage of a very long implementation time because it takes several days to set up and interconnect the conductors, which are large very heavy cables, and because it then takes a day of treatment to obtain demagnetization. In addition, this device requires an electrical installation of very large power, of the order of a megawatt, because it consumes a very high power for the duration of the current pulses. During the rest of the time, the high-power electrical installation has no use.

Un second dispositif connu comporte : des conducteurs placés au fond de la mer et formant des spires ayant un axe vertical, et un générateur de courant alternatif sinusoïdal ayant une fréquence de l'ordre de 1 Hz et une intensité de plusieurs milliers d'ampères. Le navire à démagnétiser effectue un passage au-dessus de ces spires afin de se rapprocher puis s'éloigner d'elles. La croissance puis la décroissance du champ magnétique provoquées par le rapprochement puis l'éloignement du navire réalisent une neutralisation des trois composantes de l'aimantation de ce navire. Ce dispositif nécessite, lui aussi, une installation électrique de grande puissance à cause de la grande dimension des spires, par exemple 20 m × 20 m, et à cause de leur distance par rapport au navire. En outre, la désaimantation peut être mal faite si le navire ne passe pas exactement dans le plan de symétrie des spires, et ce dispositif ne permet que la désaimantation : il ne permet pas d'appliquer une aimantation déterminée pour neutraliser la composante verticale de l'aimantation induite par le champ magnétique terrestre.A second known device comprises: conductors placed at the bottom of the sea and forming turns having a vertical axis, and a sinusoidal alternating current generator having a frequency of the order of 1 Hz and an intensity of several thousand amps. The demagnetizing vessel passes over these turns in order to approach and then move away from them. The growth then the decrease of the magnetic field caused by the approaching then the distance of the ship realize a neutralization of the three components of the magnetization of this ship. This device also requires a high-power electrical installation because of the large size of the turns, for example 20 m × 20 m, and because of their distance from the ship. In addition, demagnetization can be badly done if the ship does not pass exactly in the plane of symmetry of the turns, and this device only allows demagnetization: it does not allow to apply a determined magnetization to neutralize the vertical component of l magnetization induced by the Earth's magnetic field.

Un troisième dispositif connu comporte des conducteurs formant des spires repliées en forme de double U entourant une portion de la coque du navire et déplacées continûment le long de cette coque pendant un intervalle de temps de l'ordre de six minutes ; et un générateur d'impul­sions de courant alternativement positives et négatives, ayant une fré­quence de l'ordre de 0,5 Hz. Ce dispositif est généralement utilisé pour traiter de petits bateaux, avec une puissance électrique mise en jeu supérieure à 200 kw. D'autre part, ce dispositif ne permet pas d'appliquer une aimantation déterminée pour compenser aussi la composante verticale de l'aimantation induite dans le navire par le champ magnétique terrestre.A third known device comprises conductors forming turns folded in the shape of a double U surrounding a portion of the hull of the ship and moved continuously along this hull for a time interval of the order of six minutes; and a generator of alternating positive and negative current pulses, having a frequency of the order of 0.5 Hz. This device is generally used to treat small boats, with an electrical power involved greater than 200 kw. On the other hand, this device does not make it possible to apply a determined magnetization to also compensate for the vertical component of the magnetization induced in the ship by the terrestrial magnetic field.

Le but de l'invention est de réaliser un dispositif de désaimanta­tion nécessitant une installation électrique de puissance moindre que les dispositifs connus, afin d'abaisser le coût de cette installation électrique ; diminuant la durée de traitement pour chaque navire ; et permettant de créer une aimantation permanente déterminée pour neutraliser la compo­sante verticale de l'aimantation induite dans le navire par le champ magnétique terrestre. Pour atteindre ce but le dispositif selon l'invention comporte : une batterie de condensateurs qui est chargée lentement par une installation électrique de relativement faible puissance et qui est déchargée rapidement, en quelques centaines de millisecondes ; des con­ducteurs électriques formant des spires de dimensions très inférieures à la longueur du navire, pour réaliser un traitement localisé de chaque portion du navire ; et un dispositif d'asservissement permettant d'automatiser le traitement, en asservissant la tension de charge des condensateurs et le sens du courant de décharge en fonction de l'aimantation mesurée par des magnétomètres, et en fonction d'une valeur de consigne.The object of the invention is to provide a demagnetization device requiring an electrical installation of lower power than the known devices, in order to lower the cost of this electrical installation; reducing the processing time for each vessel; and making it possible to create a permanent magnetization determined to neutralize the vertical component of the magnetization induced in the ship by the terrestrial magnetic field. To achieve this object, the device according to the invention comprises: a capacitor bank which is charged slowly by a relatively low power electrical installation and which is discharged quickly, in a few hundred milliseconds; electrical conductors forming turns much smaller than the length of the ship, for localized treatment of each portion of the ship; and a control device for automating the processing, by controlling the charge voltage of the capacitors and the direction of the discharge current as a function of the magnetization measured by magnetometers, and as a function of a set value.

Selon l'invention, un dispositif de désaimantation, notamment pour navires, comportant des conducteurs formant des spires placées à proxi­mité d'un objet à désaimanter et un générateur pour injecter des impulsions de courant dans ces conducteurs, comportant :
- des condensateurs ;
- des moyens pour charger ces condensateurs à une tension déterminée ;
- des moyens pour décharger les condensateurs dans les conduc­teurs, caractérisé en ce qu'il comporte en outre au moins un magnétomè­tre pour mesurer l'aimantation de l'objet, et des moyens pour asservir la tension de charge des condensateurs en fonction de l'aimantation de l'objet à désaimanter.According to the invention, a demagnetization device, in particular for ships, comprising conductors forming turns placed near an object to be demagnetized and a generator for injecting current pulses into these conductors, comprising:
- capacitors;
- Means for charging these capacitors at a determined voltage;
- means for discharging the capacitors in the conductors, characterized in that it further comprises at least one magnetometer for measuring the magnetization of the object, and means for controlling the charge voltage of the capacitors as a function of the magnetization of the object to be demagnetized.

L'invention sera mieux comprise et d'autres détails apparaîtront à l'aide de la description ci-dessous et des figures l'accompagnant :

  • - la figure 1 représente le schéma synoptique d'un exemple de réalisation du dispositif selon l'invention ;
  • - la figure 2 représente le graphe d'une impulsion de courant mise en oeuvre dans cet exemple de réalisation.
The invention will be better understood and other details will appear with the aid of the description below and the accompanying figures:
  • - Figure 1 shows the block diagram of an embodiment of the device according to the invention;
  • - Figure 2 shows the graph of a current pulse implemented in this exemplary embodiment.

L'exemple de réalisation représenté sur la figure 1 est destiné à désaimanter un navire 1 dans les directions horizontales et à lui communi­quer une aimantation prédéterminée, non nulle, dans la direction verticale afin de compenser l'aimantation induite par le champ magnétique terres­tre. Cet exemple comporte des conducteurs 2 à 6 formant trois ensembles de spires dont les axes sont orthogonaux deux à deux ; cinq magnéto­mètres 7 à 11 ; une borne d'entrée 16 reliée à un réseau public de distribution électrique ; un générateur 17 de courant continu ; une batte­rie de condensateurs 18 ; un dispositif 19 de commutation en pont ; une inductance 20 ; un commutateur 21 à deux entrées et six sorties ; un dispositif 22 d'asservissement de la tension de charge de la batterie de condensateurs 18 ; un dispositif de calcul constitué principalement d'un microprocesseur 23 ; un écran et un clavier 24.The exemplary embodiment shown in FIG. 1 is intended to demagnetise a ship 1 in the horizontal directions and to impart to it a predetermined magnetization, not zero, in the vertical direction in order to compensate for the magnetization induced by the terrestrial magnetic field. This example comprises conductors 2 to 6 forming three sets of turns whose axes are orthogonal two by two; five magnetometers 7 to 11; an input terminal 16 connected to a public electrical distribution network; a generator 17 of direct current; a capacitor bank 18; a bridge switching device 19; an inductor 20; a switch 21 with two inputs and six outputs; a device 22 for controlling the charging voltage of the capacitor bank 18; a computing device mainly consisting of a microprocessor 23; a screen and a keyboard 24.

Le navire 1 est traité par portion d'une longueur de l'ordre de 20 mètres. Lorsqu'une portion a été traitée les conducteurs sont déplacés pour traiter une portion voisine ou bien le navire est déplacé par rapport à ces conducteurs. Le dispositif permet de réaliser successivement la désaimantation selon trois axes orthogonaux correspondant aux trois axes des ensembles de spires. L'écran et le clavier 24 permettent de fournir au dispositif de désaimantation une valeur de consigne déterminant l'aiman­tation résiduelle souhaitée dans la direction verticale pour compenser l'aimantation induite par le champ magnétique terrestre.The vessel 1 is treated in portions of a length of the order of 20 meters. When a portion has been treated, the conductors are moved to treat a neighboring portion or the ship is moved relative to these conductors. The device makes it possible to carry out demagnetization successively along three orthogonal axes corresponding to the three axes of the sets of turns. The screen and the keyboard 24 make it possible to supply the demagnetization device with a set value determining the desired residual magnetization in the vertical direction to compensate for the magnetization induced by the earth's magnetic field.

Un premier ensemble de spires est formé de conducteurs 6 installés au fond de la mer et formant un carré de 20m × 20m. Un second ensemble de spires est constitué de deux moitiés symétriques par rapport à l'axe longitudinal du navire 1 et formé de spires carrées de 20m × 20m dont le plan est parallèle au plan de symétrie du navire et qui sont situées près des flancs de celui-ci. Un troisième ensemble de conducteurs 4 et 5 est situé dans un plan perpendiculaire à l'axe longitudinal du navire et passant par les centres des spires formées par les conducteurs 2, 3 et 6. Ce troisième ensemble de conducteurs comporte des spires carrées incomplètes formées par les conducteurs 4 et d'autres spires carrées incomplètes formées par les conducteurs 5 et destinées à refermer les circuits des conducteurs 4. Les conducteurs 4 forment trois côtés de spires carrées de dimensions 20m × 20m, le côté supérieur manquant. L'ensemble des conducteurs 5 forme des spires carrées incomplètes éloignées des conducteurs 4 afin de ne pas contrarier le champ magné­tique créé par les conducteurs 4. Les conducteurs 4 sont destinés à créer un champ magnétique dans la direction de l'axe longitudinal du navire 1. Les conducteurs 2 et 3 sont destinés à créer un champ magnétique dans la direction de l'axe transversal du navire 1. Les conducteurs 6 sont destinés à créer un champ magnétique dans la direction verticale.A first set of turns is formed of conductors 6 installed at the bottom of the sea and forming a square of 20m × 20m. A second set of turns consists of two halves symmetrical with respect to the longitudinal axis of the ship 1 and formed of square turns of 20m × 20m whose plane is parallel to the plane of symmetry of the ship and which are located near the sides of that -this. A third set of conductors 4 and 5 is located in a plane perpendicular to the longitudinal axis of the ship and passing through the centers of the turns formed by conductors 2, 3 and 6. This third set of conductors comprises incomplete square turns formed by the conductors 4 and other incomplete square turns formed by the conductors 5 and intended to close the circuits of the conductors 4. The conductors 4 form three sides of square turns of dimensions 20m × 20m, the upper side missing. All of the conductors 5 form incomplete square turns distant from the conductors 4 so as not to counter the magnetic field created by the conductors 4. The conductors 4 are intended to create a magnetic field in the direction of the longitudinal axis of the ship 1 The conductors 2 and 3 are intended to create a magnetic field in the direction of the transverse axis of the ship 1. The conductors 6 are intended to create a magnetic field in the vertical direction.

Ces trois ensembles de conducteurs sont reliés chacun par deux lignes au commutateur 21. Le commutateur 21 reçoit sur ses deux entrées des impulsions de courant qu'il transmet à l'un des ensembles de conduc­teurs en fonction d'un signal de sélection appliqué à une entrée de commande par le microprocesseur 23. Les cinq magnétomètres 7 à 11 permettent de mesurer le champ magnétique créé par l'aimantation du navire 1. Chaque magnétomètre fournit trois signaux de mesure corres­pondant respectivement à trois composantes du champ magnétique, ortho­gonales deux à deux et parallèles aux directions des trois champs magnétiques créés respectivement par les trois ensembles de conducteurs.These three sets of conductors are each connected by two lines to the switch 21. The switch 21 receives on its two inputs current pulses which it transmits to one of the sets of conductors according to a selection signal applied to a control input by microprocessor 23. The five magnetometers 7 to 11 make it possible to measure the magnetic field created by the magnetization of the ship 1. Each magnetometer provides three measurement signals corresponding respectively to three components of the magnetic field, orthogonal two by two and parallel to the directions of the three magnetic fields created respectively by the three sets of conductors.

Les magnétomètres sont solidaires des trois ensembles de con­ducteurs et sont situés en-dessous du navire, à un niveau inférieur à la partie horizontale des spires formées par les conducteurs 4. Dans cet exemple de réalisation, la partie inférieure des spires formées par les conducteurs 4, la partie inférieure des spires formées par les conducteurs 2 et 3, et l'ensemble des spires formées par les conducteurs 6 sont situés dans un même plan qui est plus bas que la quille du navire. Le magnétomètre 7 est placé sur l'axe de symétrie des spires formées par les conducteurs 6, et les quatre autres magnétomètres sont situés à une même distance, de l'ordre de 15m, par rapport au magnétomètre 7 et sont dans un plan horizontal passant par celui-ci. Les magnétomètres 8 et 10 sont situés sur une droite passant par le magnétomètre 7 et parallèle à axe longitudinal du navire alors que les magnétomètres 9 et 11 sont situés sur une droite passant par le magnétomètre 7 et perpendiculaire à cet axe.The magnetometers are integral with the three sets of conductors and are located below the vessel, at a level below the horizontal part of the turns formed by the conductors 4. In this embodiment, the lower part of the turns formed by the conductors 4 , the lower part of the turns formed by conductors 2 and 3, and all of the turns formed by conductors 6 are located in the same plane which is lower than the keel of the ship. The magnetometer 7 is placed on the axis of symmetry of the turns formed by the conductors 6, and the other four magnetometers are located at the same distance, of the order of 15m, from the magnetometer 7 and are in a horizontal passing plane by this one. The magnetometers 8 and 10 are located on a straight line passing through the magnetometer 7 and parallel to the ship's longitudinal axis while the magnetometers 9 and 11 are located on a straight line passing through the magnetometer 7 and perpendicular to this axis.

L'écran et le clavier 24 sont couplés au microprocesseur 23 pour recevoir des informations à afficher sur l'écran et pour transmettre les ordres donnés par l'opérateur en tapant sur le clavier. Le microprocesseur 23 possède une entrée multiple couplée aux magnétomètres 7 à 11 pour recevoir leurs signaux de mesure, et une entrée reliée à une sortie du dispositif 22 fournissant un signal logique quand la batterie de condensa­teur 18 est suffisamment chargée. Il possède une sortie reliée à une entrée de commande du dispositif 22 d'asservissement de la tension de charge pour lui fournir un signal de valeur Vo déterminant la tension de charge de la batterie de condensateurs 18 ; une sortie fournissant un mot binaire P à une entrée de commande du dispositif 19 de commutation en pont, pour déclencher le passage du courant dans les ensembles de conducteurs 2 à 6 avec un sens choisi, en commandant la fermeture de deux branches du pont.The screen and the keyboard 24 are coupled to the microprocessor 23 to receive information to be displayed on the screen and to transmit the orders given by the operator by typing on the keyboard. The microprocessor 23 has a multiple input coupled to the magnetometers 7 to 11 to receive their measurement signals, and an input connected to an output of the device 22 providing a logic signal when the capacitor bank 18 is sufficiently charged. It has an output connected to a control input of the device 22 for controlling the charging voltage to provide it with a value signal V o determining the charging voltage of the capacitor bank 18; an output providing a binary word P to a control input of the bridge switching device 19, to trigger the passage of current in the sets of conductors 2 to 6 with a chosen direction, by controlling the closing of two branches of the bridge.

Le générateur 17 reçoit l'énergie électrique fournie en 16 par le réseau public. Il possède deux sorties reliées respectivement à deux entrées de la batterie de condensateurs 18. Celle-ci possède deux sorties reliées respectivement à deux entrées du dispositif 19 et à deux entrées du dispositif d'asservissement 22. Le dispositif 19 est un dispositif de commutation en pont, réalisé par exemple au moyen de thyristors. Il possède deux sorties reliées respectivement à une première borne de l'inductance 20 et à une première entrée du commutateur 21. Une seconde borne de l'inductance 20 est reliée à une seconde entrée du commutateur 21. Le commutateur 21 peut être réalisé au moyen de thyristors, selon des techniques classiques.The generator 17 receives the electrical energy supplied at 16 by the public network. It has two outputs connected respectively to two inputs of the capacitor bank 18. This has two outputs connected respectively to two inputs of the device 19 and to two inputs of the servo device 22. The device 19 is a bridge switching device, produced for example by means of thyristors. It has two outputs connected respectively to a first terminal of the inductor 20 and to a first input of the switch 21. A second terminal of the inductor 20 is connected to a second input of the switch 21. The switch 21 can be achieved by means thyristors, according to conventional techniques.

Le dispositif 22 d'asservissement de la tension de charge de la batterie de condensateurs 18 possède une sortie reliée à une entrée de commande du générateur 17 pour charger la batterie de condensateurs 18 à une tension correspondant à la valeur Vo du signal fourni par le microprocesseur 23. Cette charge est réalisée approximativement à courant constant. Lorsque la charge de la batterie de condensateurs 18 a atteint la valeur fixée, le dispositif 22 envoie un signal logique au microprocesseur 23 et celui-ci peut alors déclencher l'envoi d'une impul­sion de courant dans un des ensembles de conducteurs en commandant le dispositif 19.The device 22 for controlling the charging voltage of the capacitor bank 18 has an output connected to a control input of the generator 17 for charging the capacitor bank 18 at a voltage corresponding to the value V o of the signal supplied by the microprocessor 23. This charge is carried out approximately at constant current. When the charge of the capacitor bank 18 has reached the fixed value, the device 22 sends a logic signal to the microprocessor 23 and the latter can then trigger the sending of a current pulse in one of the sets of conductors by controlling the device 19.

Le circuit de décharge de la batterie de condensateurs 18 est constitué par le dispositif 19, l'inductance 20, le commutateur 21, et la résistance ohmique de l'ensemble de conducteurs qui est mis dans le circuit au moyen du commutateur 21. L'inductance des conducteurs constituant les spires est négligeable par rapport à la valeur de l'induc­tance 20 et la présence du navire 1 à proximité des conducteurs influe peu sur l'inductance totale du circuit.The discharge circuit of the capacitor bank 18 is constituted by the device 19, the inductor 20, the switch 21, and the ohmic resistance of the set of conductors which is put into the circuit by means of the switch 21. The inductance of the conductors constituting the turns is negligible compared to the value of the inductance 20 and the presence of the vessel 1 near the conductors has little influence on the total inductance of the circuit.

Il est connu que le courant de décharge d'un condensateur de capacité C dans un circuit possèdant une inductance L et une résistance R peut donner lieu à deux régimes différents selon la valeur de l'amortisse­ment de ce circuit. Si la valeur R est inférieure à 2

Figure imgb0001
le courant est un courant oscillatoire amorti. Si la résistance R a une valeur supérieure ou égale à 2
Figure imgb0002
 le courant est constitué d'une seule impulsion.It is known that the discharge current of a capacitor of capacitance C in a circuit having an inductance L and a resistor R can give rise to two different regimes depending on the value of the damping of this circuit. If the R value is less than 2
Figure imgb0001
 the current is a damped oscillating current. If resistance R has a value greater than or equal to 2
Figure imgb0002
 the current consists of a single pulse.

Lorsque la résistance R est égale à 2

Figure imgb0003
l'amortissement est dit critique. L'intensité du courant en fonction du temps est donnée par la formule :
Figure imgb0004
 Vo étant la tension de charge du condensateur à l'instant t = 0 et τ étant la constante de temps. L'intensité de ce courant passe par un maximum pour t = τ et a pour valeur :
Figure imgb0005
 When the resistance R is equal to 2
Figure imgb0003
 depreciation is said to be critical. The intensity of the current as a function of time is given by the formula:
Figure imgb0004
 V o being the charge voltage of the capacitor at time t = 0 and τ being the time constant. The intensity of this current passes through a maximum for t = τ and has the value:
Figure imgb0005

La figure 2 représente la forme de l'impulsion de courant obtenue, pour un amortissement critique. Cette figure représente le graphe de la fonction :

Figure imgb0006
en fonction de la variable : x =
Figure imgb0007
FIG. 2 represents the shape of the current pulse obtained, for critical damping. This figure represents the graph of the function:
Figure imgb0006
 depending on the variable: x =
Figure imgb0007

L'impulsion de courant obtenue n'est pas rectangulaire mais on peut néanmoins définir sa durée en considérant l'intervalle de temps pendant lequel l'intensité du courant est égale à imax moins 3dB. Cette durée est égale à 1,7. τ. L'expérience montre qu'une durée de l'ordre de quelques centaines de millisecondes est nécessaire pour obtenir un traite­ment de démagnétisation efficace. Par exemple, 500 ms est une durée réalisant un bon compromis entre l'efficacité de la démagnétisation et l'énergie électrique nécessaire pour créer cette impulsion de courant.The current pulse obtained is not rectangular but its duration can nevertheless be defined by considering the time interval during which the current intensity is equal to i max minus 3dB. This duration is equal to 1.7. τ. Experience shows that a period of the order of a few hundred milliseconds is necessary to obtain an effective demagnetization treatment. For example, 500 ms is a duration achieving a good compromise between the efficiency of demagnetization and the electrical energy necessary to create this current pulse.

Par exemple, pour cette durée de 500 ms l'intensité maximale est égale à 31,12.C.Vo . Si cette intensité maximale est fixée à 1000 ampères, la charge initiale C.Vo de la batterie de condensateurs 18 est égale à 800 coulombs. Pour une tension de fin de charge égale à 1000 volts la capacité C doit alors avoir pour valeur 0,8 Farads. Dans un exemple de réalisation le temps de charge pour obtenir cette tension est égal à 1,5 minute et le courant initial de charge a une intensité de 50 ampères. La puissance électrique fournie par l'installation est donc de l'ordre de 50 kw pendant la charge de la batterie de condensateurs 18.For example, for this duration of 500 ms the maximum intensity is equal to 31.12.CV o . If this maximum intensity is set at 1000 amperes, the initial charge CV o of the capacitor bank 18 is equal to 800 coulombs. For an end-of-charge voltage equal to 1000 volts, the capacity C must then have the value 0.8 0.8 Farads. In an exemplary embodiment, the charging time to obtain this voltage is equal to 1.5 minutes and the initial charging current has an intensity of 50 amps. The electrical power supplied by the installation is therefore of the order of 50 kw during the charging of the capacitor bank 18.

Le dispositif selon l'invention peut bien entendu fonctionner avec un amortissement supérieur ou inférieur à l'amortissement critique. En pratique les impulsions d'efficacité maximale sont obtenues lorsque le circuit de décharge a un amortissement voisin de l'amortissement critique.The device according to the invention can of course operate with a damping greater or less than the critical damping. In practice, the pulses of maximum efficiency are obtained when the discharge circuit has a damping close to the critical damping.

Suivant une variante, il est à la portée de l'homme de l'art de remplacer l'inductance 20 par un circuit d'adaptation comportant plusieurs inductances et plusieurs condensateurs dans le but de fournir aux trois ensembles de conducteurs des impulsions de courant ayant une forme voisine de la forme rectangulaire.According to a variant, it is within the reach of those skilled in the art of replacing the inductor 20 by an adaptation circuit comprising several inductors and several capacitors in order to supply the three sets of conductors with current pulses having a shape close to that of the rectangular shape.

Afin de réduire le plus possible la puissance de l'installation électrique, chaque portion de navire est traitée selon trois axes successi­vement. Cependant il est envisageable de réaliser la désaimantation simultanément selon trois axes en prévoyant trois batteries de condensa­teurs indépendantes, trois dispositifs de charge indépendants et trois dispositifs de décharge indépendants, commandés en parallèle par un même dispositif de calcul.In order to reduce the power of the electrical installation as much as possible, each portion of the ship is treated along three axes in succession. However, it is possible to carry out demagnetization simultaneously along three axes by providing three independent capacitor banks, three independent charging devices and three independent discharge devices, controlled in parallel by the same calculation device.

Les magnétomètres 7 à 11 permettent de mesurer l'aimantation de la portion de navire en cours de traitement. Les magnétomètres 8 et 10 permettent de tenir compte respectivement de l'aimantation de la portion qui a été traitée immédiatement précédemment et de l'aimantation de la portion qui va être traitée immédiatement après. Les magnétomètres 9 et 11, qui sont déportés transversalement par rapport au magnétomètre 7, permettent de tenir compte de la non-homogénéité de l'aimantation dans la portion de navire en cours de traitement.The magnetometers 7 to 11 make it possible to measure the magnetization of the portion of the ship being processed. The magnetometers 8 and 10 make it possible to take account respectively of the magnetization of the portion which has been treated immediately previously and of the magnetization of the portion which will be treated immediately after. The magnetometers 9 and 11, which are offset transversely with respect to the magnetometer 7, make it possible to take account of the non-homogeneity of the magnetization in the portion of the ship being processed.

Le traitement d'une portion d'un navire commence par la mesure de son aimantation. Les signaux de mesure fournis par les magnétomètres 7 à 11 permettent au dispositif de calcul 23 de déterminer, pour les trois directions, la polarité et l'intensité imax du courant pour une première impulsion de démagnétisation. Cette intensité est proportionnelle à l'ai­mantation mesurée dans la direction correspondante. La formule (2) permet de faire correspondre à imax une valeur Vo de la tension de fin de charge de la batterie de condensateurs 18. Quand cette tension de charge est atteinte le dispositif d'asservissement 22 fournit un signal logique au microprocesseur 23. Ce dernier peut alors déclencher la décharge.The processing of a portion of a ship begins with the measurement of its magnetization. The measurement signals supplied by the magnetometers 7 to 11 allow the calculation device 23 to determine, for the three directions, the polarity and the intensity i max of the current for a first demagnetization pulse. This intensity is proportional to the magnetization measured in the corresponding direction. The formula (2) makes it possible to correspond to i max a value V o of the end of charge voltage of the capacitor bank 18. When this charge voltage is reached the servo device 22 supplies a logic signal to the microprocessor 23 The latter can then trigger the discharge.

Après la décharge d'une première impulsion de courant, une mesure de l'aimantation résiduelle est réalisée dans la direction considé­rée. Le microprocesseur 23 détermine une valeur d'intensité imax pour une seconde impulsion de désaimantation et en déduit la valeur Vo de la tension de fin de charge de la batterie de condensateur 18. Quand la batterie de condensateurs 18 a atteint la tension Vo , le dispositif d'asservissement 22 avertit le microprocesseur 23 qui peut alors déclen­cher la décharge d'une seconde impulsion. Cette séquence est réitérée jusqu'à ce que l'aimantation, dans la direction considérée, ait été ramenée à la valeur de consigne fixée par l'opérateur. Cette valeur de consigne est nulle pour les composantes horizontales et non nulle pour la composante verticale. La valeur de la composante verticale de l'aimantation perma­nente est choisie en fonction de la région où le navire doit naviguer.After the discharge of a first current pulse, a measurement of the residual magnetization is carried out in the direction considered. The microprocessor 23 determines an intensity value i max for a second demagnetization pulse and deduces therefrom the value V o of the end of charge voltage of the capacitor bank 18. When the capacitor bank 18 has reached the voltage V o , the device servo 22 warns the microprocessor 23 which can then trigger the discharge of a second pulse. This sequence is repeated until the magnetization, in the direction considered, has been brought back to the set value set by the operator. This setpoint is zero for the horizontal components and not zero for the vertical component. The value of the vertical component of the permanent magnetization is chosen according to the region where the ship is to sail.

L'estimation de l'aimantation de la portion de navire à traiter est réalisée à partir des mesures du champ magnétique, dans les trois directions, par les cinq magnétomètres 8 à 11, en faisant l'hypothèse que le barycentre des masses magnétiques correspond au barycentre G de la coque du navire. Les composantes Mx, My, Mz de l'aimantation en ce point G sont liées aux valeurs Bx , By , Bz du champ magnétique mesuré par l'un des magnétomètres, par les relations connues :

Figure imgb0008
où x, y, z sont les coordonnées du magnétomètre dans un repère orthonormé situé en G et où r est la distance entre le magnétomètre et le point G. Les valeurs x, y, z, r étant connues, pour chaque magnétomètre, il y a à résoudre un système de 15 équations à trois inconnues. Il peut être résolu par la méthode classique appelée méthode des moindres carrés, par exemple. La programmation du microprocesseur 23 pour appliquer cette méthode est à la portée de l'homme de l'art.The magnetization of the portion of the vessel to be treated is estimated from measurements of the magnetic field, in three directions, by the five magnetometers 8 to 11, assuming that the barycenter of the magnetic masses corresponds to the barycenter G of the ship's hull. The components Mx, My, Mz of the magnetization at this point G are linked to the values B x , B y , B z of the magnetic field measured by one of the magnetometers, by the known relationships:
Figure imgb0008
 where x, y, z are the coordinates of the magnetometer in an orthonormal coordinate system located in G and where r is the distance between the magnetometer and the point G. The values x, y, z, r being known, for each magnetometer, there has to solve a system of 15 equations with three unknowns. It can be solved by the classic method called the least squares method, for example. Programming the microprocessor 23 to apply this method is within the reach of ordinary skill in the art.

Pour neutraliser l'une des composantes Mx , My , Mz , de l'aiman­tation il faut créer une aimantation exactement opposée au moyen de l'un des ensembles de spires. Il existe une relation théoriquement connue entre l'intensité dans ces spires et l'aimantation crée, cette intensité est donc calculable. Cette intensité est proportionnelle à la valeur de la compo­sante à neutraliser. D'après la formule (2) la tension de fin de charge, Vo , est donc proportionnelle à la valeur de cette composante, mais le coefficient de proportionnalité ne peut pas être calculé de manière précise car il dépend de la forme de la spire et de la position du navire par rapport aux spires, qui ne sont pas connus de manière précise.To neutralize one of the components M x , M y , M z , of the magnetization, it is necessary to create an exactly opposite magnetization by means of one of the sets of turns. There is a theoretically known relation between the intensity in these turns and the magnetization created, this intensity is therefore calculable. This intensity is proportional to the value of the component to be neutralized. According to formula (2) the end of charge voltage, V o , is therefore proportional to the value of this component, but the proportionality coefficient cannot be calculated precisely since it depends on the shape of the turn and the position of the vessel in relation to the turns, which are not precisely known.

En pratique, ce coefficient est déterminé par un calcul très approximatif ou par un essai, dans chacune des trois directions. Il est stocké dans la mémoire du microprocesseur. L'imprécision de ce coeffi­cient n'est pas gênante car le dispositif désaimante la portion de navire par approximations successives en faisant tendre les composantes horizon­tales de l'aimantation vers zéro et en faisant tendre la composante verticale vers la valeur de consigne. Un mode de réalisation simple consiste donc à programmer le microprocesseur 23 pour calculer trois valeurs de la tension de charge selon les formules :
Vo = kx . Mx
Vo = ky . My
Vo = kz .|Mz - C|
où kx , ky , kz sont trois coefficients constants correspondant respective­ment aux deux directions horizontales et à la direction verticale. Pour cette dernière, la constante C est une valeur de consigne, non nulle, fournie par l'opérateur au moyen du clavier 24 pour obtenir une compo­sante verticale déterminée.In practice, this coefficient is determined by a very rough calculation or by a test, in each of the three directions. It is stored in the microprocessor's memory. The imprecision of this coefficient is not a problem since the device demagnetizes the portion of the ship by successive approximations by making the horizontal components of the magnetization tend towards zero and by making the vertical component tend towards the set value. A simple embodiment therefore consists in programming the microprocessor 23 to calculate three values of the charging voltage according to the formulas:
V o = k x . M x
V o = k y . M y
V o = k z . | M z - C |
where k x , k y , k z are three constant coefficients corresponding respectively to the two horizontal directions and to the vertical direction. For the latter, the constant C is a non-zero reference value supplied by the operator by means of the keyboard 24 to obtain a determined vertical component.

La suite des impulsions de courant pour traiter chaque portion de navire peut être commandée automatiquement par le microprocesseur 23, sans intervention d'un opérateur, ou bien le microprocesseur 23 peut attendre un ordre donné par l'opérateur avant de déclencher chaque impulsion. Le microprocesseur 23 peut afficher sur l'écran 24 les valeurs de l'aimantation mesurée, pour permettre à l'opérateur de surveiller le déroulement du traitement de démagnétisation.The sequence of the current pulses for processing each portion of the ship can be controlled automatically by the microprocessor 23, without the intervention of an operator, or else the microprocessor 23 can wait for an order given by the operator before triggering each pulse. The microprocessor 23 can display on the screen 24 the values of the measured magnetization, to allow the operator to monitor the progress of the demagnetization treatment.

Claims (5)

1. Dispositif de désaimantation, notamment pour navires, compor­tant des conducteurs (2 à 6) formant des spires placées à proximité d'un objet (1) à désaimanter, et un générateur pour injecter des impulsions de courant dans ces conducteurs (2 à 6), comportant :
- des condensateurs (18) ;
- des moyens (17, 22) pour charger ces condensateurs (18) à une tension déterminée ;
- des moyens (19 à 21) pour décharger les condensateurs (18) dans les conducteurs (2 à 6) ;
caractérisé en ce qu'il comporte en outre au moins un magnéto­mètre (7 à 11) pour mesurer l'aimantation de l'objet (1), et des moyens (22 à 24) pour asservir la tension de charge des condensateurs (18) en fonction de l'aimantation de l'objet (1) à désaimanter.1. Demagnetization device, in particular for ships, comprising conductors (2 to 6) forming turns placed near an object (1) to be demagnetized, and a generator for injecting current pulses into these conductors (2 to 6 ), comprising:
- capacitors (18);
- means (17, 22) for charging these capacitors (18) at a determined voltage;
- means (19 to 21) for discharging the capacitors (18) in the conductors (2 to 6);
characterized in that it further comprises at least one magnetometer (7 to 11) for measuring the magnetization of the object (1), and means (22 to 24) for controlling the charging voltage of the capacitors (18) depending on the magnetization of the object (1) to be demagnetized. 2. Dispositif selon la revendication 1 caractérisé en ce que les conducteurs (2 à 6) forment trois ensembles de spires ayant des axes orthogonaux deux à deux et permettant de créer respectivement trois composantes d'un champ magnétique dans une même portion de l'objet (1), les conducteurs (2 à 6) étant déplacés par rapport à l'objet (1) pour désaimanter successivement toutes les portions de celui-ci, et en ce que le magnétomètre (7) fournit trois signaux de mesure correspondant à trois composantes orthogonales de l'aimantation de l'objet (1) dans trois direc­tions parallèles aux champs magnétiques engendrés respectivement par les trois ensembles de spires formés par les conducteurs (2 à 6).2. Device according to claim 1 characterized in that the conductors (2 to 6) form three sets of turns having orthogonal axes two by two and allowing to respectively create three components of a magnetic field in the same portion of the object (1), the conductors (2 to 6) being moved relative to the object (1) to successively demagnetize all the portions thereof, and in that the magnetometer (7) provides three measurement signals corresponding to three orthogonal components of the magnetization of the object (1) in three directions parallel to the magnetic fields generated respectively by the three sets of turns formed by the conductors (2 to 6). 3. Dispositif selon la revendication 2, caractérisé en ce que les moyens pour asservir comportent des moyens de calcul (23) ayant une entrée couplée au magnétomètre (7) pour recevoir un signal de mesure de l'aimantation dans chacune des trois directions, et ayant deux sorties reliées respectivement à une entrée de commande des moyens pour charger (17 et 22) et à une entrée de commande des moyens pour décharger (19 à 21), pour leur fournir respectivement un signal de valeur Vo déterminant la valeur de la tension de fin de charge des condensateurs (18) et un signal P déterminant le sens du courant de décharge dans les conducteurs (2 à 6), déterminés pour chaque direction en fonction du signal de mesure de l'aimantation dans la direction considérée.3. Device according to claim 2, characterized in that the means for slaving comprise calculation means (23) having an input coupled to the magnetometer (7) for receiving a signal for measuring the magnetization in each of the three directions, and having two outputs connected respectively to a control input for charging means (17 and 22) and to a control input for discharging means (19 to 21), to respectively supply them with a value signal V o determining the value of the end of charge voltage of the capacitors (18) and a signal P determining the direction of the discharge current in the conductors (2 to 6), determined for each direction as a function of the magnetization measurement signal in the direction considered. 4. Dispositif selon la revendication 3, caractérisé en ce que le dispositif de calcul (23) détermine, pour chaque direction, un signal P en fonction du signe de la composante mesurée et détermine une valeur Vo proportionnelle à la valeur absolue de la différence entre une valeur de consigne et le module de la composante de l'aimantation mesurée, afin de faire tendre vers zéro cette différence en réalisant successivement plusieurs décharges pour une même direction et pour une même portion de l'objet (1).4. Device according to claim 3, characterized in that the calculating device (23) determines, for each direction, a signal P as a function of the sign of the measured component and determines a value V o proportional to the absolute value of the difference between a set value and the module of the component of the magnetization measured, in order to make this difference tend towards zero by successively carrying out several discharges for the same direction and for the same portion of the object (1). 5. Dispositif selon la revendication 4, caractérisé en ce qu'il comporte en outre d'autres magnétomètres (8 à 11) disposés à proximité de l'objet (1) et couplés au dispositif de calcul (23) pour estimer l'aimanta­tion de l'objet (1) à partir de mesures en plusieurs points distincts.5. Device according to claim 4, characterized in that it further comprises other magnetometers (8 to 11) arranged near the object (1) and coupled to the calculation device (23) to estimate the magnetization of the object (1) from measurements at several distinct points.
EP86402086A 1985-09-27 1986-09-23 Demagnetizing device, particularly for ships Expired - Lifetime EP0217712B1 (en)

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FR8514374 1985-09-27
FR8514374A FR2587969B1 (en) 1985-09-27 1985-09-27 DE-MAGNET DEVICE, PARTICULARLY FOR NAVAL VESSELS

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EP0247367A1 (en) * 1986-04-29 1987-12-02 Bundesrepublik Deutschland vertr. durch d. Bundesm. d. Vert. vertr. durch den Präs. d. Bundesamt. für Wehrtech. u. Beschaffung Method for setting a magnetic installation for self-protection to compensate the disturbing magnetic field of a vehicle, in particular a ship
EP0356146A2 (en) * 1988-08-19 1990-02-28 The Marconi Company Limited Magnet assembly
WO2000054293A1 (en) * 1999-03-06 2000-09-14 Imo Institut Fur Mikrostrukturtechnologie Und Opt Oelektronik E.V. System for writing magnetic scales
CN104361974A (en) * 2014-11-07 2015-02-18 中国人民解放军海军工程大学 Movable demagnetizing device
RU2616508C2 (en) * 2015-09-17 2017-04-17 Федеральное государственное унитарное предприятие "Крыловский государственный научный центр" Method of demagnetization vessel and device for its implementation
EP2755217A3 (en) * 2013-01-14 2018-01-24 Albert Maurer Demagnetisation method

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US6798632B1 (en) * 2002-06-13 2004-09-28 The United States Of America As Represented By The Secretary Of The Navy Power frequency electromagnetic field compensation system
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US7451719B1 (en) * 2006-04-19 2008-11-18 The United States Of America As Represented By The Secretary Of The Navy High temperature superconducting degaussing system
RU2583257C1 (en) * 2014-12-05 2016-05-10 Федеральное государственное унитарное предприятие "Крыловский государственный научный центр" (ФГУП "Крыловский государственный научный центр") Method for demagnetisation of ship
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Cited By (8)

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Publication number Priority date Publication date Assignee Title
EP0247367A1 (en) * 1986-04-29 1987-12-02 Bundesrepublik Deutschland vertr. durch d. Bundesm. d. Vert. vertr. durch den Präs. d. Bundesamt. für Wehrtech. u. Beschaffung Method for setting a magnetic installation for self-protection to compensate the disturbing magnetic field of a vehicle, in particular a ship
EP0356146A2 (en) * 1988-08-19 1990-02-28 The Marconi Company Limited Magnet assembly
EP0356146A3 (en) * 1988-08-19 1990-07-04 The Marconi Company Limited Magnet assembly
WO2000054293A1 (en) * 1999-03-06 2000-09-14 Imo Institut Fur Mikrostrukturtechnologie Und Opt Oelektronik E.V. System for writing magnetic scales
EP2755217A3 (en) * 2013-01-14 2018-01-24 Albert Maurer Demagnetisation method
CN104361974A (en) * 2014-11-07 2015-02-18 中国人民解放军海军工程大学 Movable demagnetizing device
CN104361974B (en) * 2014-11-07 2017-01-18 中国人民解放军海军工程大学 Movable demagnetizing device
RU2616508C2 (en) * 2015-09-17 2017-04-17 Федеральное государственное унитарное предприятие "Крыловский государственный научный центр" Method of demagnetization vessel and device for its implementation

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DE3676412D1 (en) 1991-02-07
NO165991C (en) 1991-05-15
NO863829D0 (en) 1986-09-25
NO863829L (en) 1987-03-30
NO165991B (en) 1991-02-04
FR2587969A1 (en) 1987-04-03
CA1283163C (en) 1991-04-16
EP0217712B1 (en) 1991-01-02
FR2587969B1 (en) 1991-10-11

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