EP0024307A1 - Device for compensating the magnetic field of disturbance of an object by means of a magnetic self-protection arrangement - Google Patents

Abstract

1. Arrangement for the compensation of magnetic interference fields by objects, preferably ships, by means of degaussing assemblies controlled by the interference field, in which differential field probes for detecting the inhomogeneous interference field, power amplifiers and compensation windings of the degaussing assembly form control circuits, which are used to control the currents flowing in the compensation windings of the assembly, characterized in that auxiliary integration elements are provided for the control circuits (3, 5-8), that individual interference fields are provided with separate control circuits for compensation, and that the separate control circuits are operated parallel to each other and parallel to the compensation assembly embracing the entire object (2).

Description

The invention relates to a method according to the preamble of the main claim.

From DE-PS 977 727 a device for controlling magnetic self-protection systems (MES) against the effect of the induced portion of the magnetic moment of ships is known. For this purpose, three field measuring probes are provided outside the magnetic interference range of the ship, preferably on a non-magnetic mast tip, which control the excitation of power amplifiers via a field measuring device, which in turn supply currents for the compensation windings of the system. The three field measuring probes should be arranged individually or preferably rotatably together and the field measuring devices and power amplifiers should be equipped with special devices for negative feedback and thus for uninterrupted self-monitoring of the entire system.

DE-PS 977 846 shows that the geometric interference field gradients arising from the ship and occurring in the associated probe pairs are used to control the MES windings. With this procedure automatic self-compensation in the manner of a closed control loop may be possible.

• 1.) Änderungen des permanenten magnetischen Zustandes durch Alterung, Erschütterungen, Anbringen und Entfernen von magnetischen Teilen oder Geräten, Auswechseln von Maschinen, Waffen, Übernahme und Verschießen von magnetischer Munition, Torpedos, Übernahme von in Blechdosen verpacktem Proviant bzw. Beseitigen der leeren Blechdosen.
• 2.) Änderung der Tauchtiefe von ferromagnetischen U-Booten.
• 3.) Rückkopplungseffekte auf die Schlingereffekte (Wirbelstromerzeugung durch Schlingern) werden nicht direkt gemessen und dementsprechend nicht exakt kompensiert. Hierzu werden schwierig zu ermittelnde Erfahrungswerte benötigt. Die Wirbelstromeffekte durch Stampf- und Rollbewegungen des Objektes bleiben unberücksichtigt.
• 4.) Die Kompensation steht nicht im direkten Zusammenhang mit dem gemessenen Eigenfeld des zu kompensierenden Objektes. Es muß jeweils vorausgesetzt werden, daß sie richtig eingestellt wird und später keine Änderung erfährt.
• 5.) Kompensation von Feldern elektrischer Fahranlagen bleibt unberücksichtigt.
• 6.) Eine Selbstvermessung bzw. Kontrolle des Eigenfeldes ist nicht möglich.

Finally, it is also known from DE-PS 977 881 to compensate for the effects of individual interference bodies within a vehicle by attaching so-called anti-dipoles in the vicinity of the magnetic center of gravity of the interference body. These MES systems, which are only mentioned as examples, suffer from the essential deficiency that changes in the magnetic state of an object cannot be recorded with sufficient accuracy, the following changes being mentioned:

• 1.) Changes in the permanent magnetic state due to aging, vibrations, attaching and removing magnetic parts or devices, changing machines, weapons, taking over and firing magnetic ammunition, torpedoes, taking over provisions packed in tin cans or removing the empty tin cans.
• 2.) Change the diving depth of ferromagnetic submarines.
• 3.) Feedback effects on the roll effects (eddy current generation by roll) are not measured directly and accordingly are not exactly compensated for. This requires empirical values that are difficult to determine. The eddy current effects caused by tamping and rolling movements of the object are not taken into account.
• 4.) The compensation is not directly related to the measured field of the object to be compensated. It must be assumed that it is set correctly and that no changes are made later.
• 5.) Compensation for fields of electrical driving systems is not taken into account.
• 6.) A self-measurement or control of the own field is not possible.

With a gradient magnetic probe, which normally consists of two magnetic sensors that are mounted antiparallel at a basic distance from one another, the polarity of the measuring effect can be used to determine the direction of the magnetic field strength an inhomogeneous magnetic field, e.g. B. the own field of a ship can be closed if it is known to which side of the probe the absolute amounts of the magnetic field strength decrease or increase.

If the above-mentioned requirement is met, a gradient probe can be used according to FIG. 1 to compensate for the magnetic self-field 1 of an object 2. In this example, the arrangement of a gradient magnetometer probe 3 is shown. Here the probe is located away from object 2 to be compensated. It is attached approximately in the radial direction to object 2. This "being away" from the magnetic center of gravity already fulfills the above-mentioned condition due to the distance law for the magnetic field of the object.

A polarity reversal of the stray field results in a clear polarity reversal of the probe effect at the deflection of the Magnetomeier display instrument 4, as shown in FIG. 2, when the probe is only able to detect components of the object's own field.

The invention has for its object to provide a method with which magnetic changes can be detected on the spot and the corresponding compensation means can be influenced directly using a much more precise field probe.

To achieve this object, the features specified in the characterizing part of the main claim are used according to the invention. Further developments of the invention are characterized in the subclaims.

First of all, it should be pointed out a difficulty which is present when using gradient probes of the previous design.

If a probe is attached in the vicinity of an object to be compensated, the gradients here are particularly large due to the magnetic distance limit, which means that the accuracy requirements do not have to be very great. However, in this case the influence of magnetic inhomogeneities of the object is particularly disruptive, e.g. B. in ships, the structures, frames, devices, etc.

However, the greater the distance between the probe and the object, the more similar the magnetic self-field measured at the top to that at the bottom. However, increasing the distance of the probe from the object results in a significant reduction in the measuring effect. But there must be demands on the measurement accuracy of gradient magnetometers, for. B. to measure the magnetic field of ships, which are currently not to be met. The reason for this relatively low accuracy is that it is not possible to align the two sensors of a probe exactly antiparallel.

It is normally not known in which direction and by what amount the two sensors of the probe are crooked, and it is therefore not possible to distinguish the measurement effect from the disturbance variable. In particular, thermal expansion, mechanical stress and the age of the material have a misaligning effect.

If a probe is moved in a homogeneous earth field, there should theoretically be no measurement effect. Depending on the spatial position of the probe in relation to the earth field and depending on the type of movement, disturbing effects occur which make it impossible to solve important measurement problems. They are often larger than the measuring effect.

Exemplary embodiments according to the invention are shown in the drawing, namely FIGS. 1 and 2 show the arrangement of a gradient magnetometer probe in the magnetic earth field, FIGS. 3 and 4 show the coupling of the probe to the compensation winding, FIG. 5 shows a rotatable magnetometer probe, FIG. 6 one way of reducing the number of probes, and Figures 7 to 9 further examples of reducing the number of probes.

In FIG. 3, the probe and the compensation winding are coupled to one another in such a way that the measuring effect of the probe 3 at the output of a gradient magnetometer 5 is integrated via an integration element 6, for example an electronic integration element, an integration amplifier or a computer. The output signal of the integration element is then supplied to a power element 7 as electrical voltage. A DC power amplifier can be used for this. However, it is also possible to supply the signal indirectly to the excitation winding of a direct current generator or to supply it for driving thyristors use. The power element 7 supplies the current for a compensation winding 8 (MES winding) with which the magnetometer electronics 5 to 7 are permanently connected in such a way that the magnetic field generated, or a component thereof, is directed opposite the measured field.

Such a combination can be used to compensate for an object 2 and / or parts of an object wherever the compensation of a specific stray field component is considered necessary. In the example according to FIG. 4, components 9, 10 and 11 are provided for the X, Y and Z directions.

The probe for performing the method is improved in such a way that it is rotatably supported about its longitudinal axis according to FIG. For this purpose, two non-magnetic ball bearings 13 and 14 and a hydraulic, pneumatic or electric motor, preferably a synchronous motor, are provided. However, the probe can also be rotated by hand, with wind power or by means of the travel current. Because of the inevitable misalignment of the two anti-parallel sensors 15 and 16, which are shown exaggeratedly obliquely in the figure, both sensors produce a more or less large interaction. The two interfering effects are usually different in size and out of phase with one another. Both interactions are subtracted after the usual switching of gradient magnetometers. This creates an alternating effect in the form of an alternating voltage, which is superimposed on the actual measuring effect. This disturbing, symmetrical alternating effect is now made to disappear by attenuators or filters. The pure measuring effect is thus available. Eliminating the disturbing alternating field effect is facilitated by the fact that its frequency corresponds exactly to the speed of the probe. The speed should therefore be selected so that it is as different as possible from the frequency of the measuring effects. A speed adjustment device can be used for this.

If the gradient changes quickly, e.g. B. with alternating fields generated by the object, it is advisable to switch off the interference frequency occurring due to misalignment of the sensors 15 and 16 by counting stages.

To pass on the measurement signals from the rotating probe, slip rings 17 (mercury slip rings), inductive or capacitive transmitters or

Radio transmitters are used. In this case, it is advisable to use the entire electronics 18 of the magnetometer or parts thereof, e.g. B. circulate miniaturized form together with the probe.

However, it is also conceivable to have the probe torsional vibrations, preferably harmonic, by angles of 360 or also by smaller angles. Torsional vibrations have the advantage that the sensors can be connected to the downstream links by means of cables.

Furthermore, the number of probes required to compensate for an object can be reduced. Instead of using three probes, one for the V, L and H windings corresponding to the Z, X and Y directions, a single probe 19 according to FIG. 6 is sufficient if it is skewed to the coil directions X. , Y and Z is arranged. This probe can be a fixed or rotating probe. If a component of the object to be demagnetized is of particular importance; so the angular position of the probe is closer to this direction than another less important one. The resultant measuring effect contains the measuring effects of the X, Y and Z components as one quantity.

• Nacheinander werden alle vorhandenen Wicklungen an den Sensor angekoppelt. Es wird ein Strom auf die erste Kompensationswicklung geschaltet und mittels einer Logikschaltung die Stromrichtung sofort umgeschaltet, falls der Meßeffekt hierdurch ansteigt. Fällt der Meßeffekt dagegen ab, so läßt man den Strom in dieser Richtung für kurze Zeit weiterfließen. Danach wird mit den übrigen Wicklungen entsprechend verfahren und der ganze Vorgang wiederholt, bis der Meßeffekt an der Sonde Null wird. Die jeweiligen Stromgrößen können dabei laufend abnehmend vorgesehen oder die Stromflußzeiten verkürzt werden.

A breakdown for controlling the windings can be carried out in the following way:

• All existing windings are connected to the sensor one after the other. A current is switched to the first compensation winding and the current direction is immediately switched by means of a logic circuit if the measuring effect thereby increases. On the other hand, if the measuring effect drops, the current is allowed to continue flowing in this direction for a short time. The other windings are then moved accordingly and the whole process is repeated until the measuring effect on the probe becomes zero. The respective current quantities can continuously decrease or the current flow times can be shortened.

Another possibility of making the gradient measurement effect zero and thus the natural field of the object to be compensated is to transfer the control of the current direction for the compensation windings to special field probes which detect the direction of the natural field of the object. If e.g. B. a V, L and H winding are provided, a triple probe for the X, Y and Z directions is to be used.

Another possibility for the rotating probe is to consciously rotate a sensor in a certain direction deviating from an ideal position, and preferably by an angle that lies outside the angular tolerance of the sensors. Since the direction of the misalignment of the sensor is thus known, the resulting measuring effect of this sensor can be used to infer the field direction at the location of the sensor. The greatest measuring effect occurs with the rotating position of the probe, where the measuring direction of the sensor and the field direction come closest. However, both sensors can also be tilted in the manner described.

It is known and advantageous to have some or all of the probes in one place, e.g. B. in the mast of a ship, as shown in Figure 7. In this example, probe 20 measures the gradient of the X component, probe 21 that of the Y component, and probe 22 that of the Z component. The probe base then receives exactly or only approximately a radial direction (gradient direction) to the object. In this case of application, however, it is necessary to arrange the sensors in the probes in a different way. Although they are always to be installed antiparallel, the sensors receive the direction of the corresponding field direction to be measured. All sensors can also be combined in one probe (FIG. 8), or one sensor each takes over, crooked, the function of more than one sensor (FIG. 9), analogously to the example described in FIG. 6. The probes should be set up in a known manner, if possible, where probe zero coincides with the object's own field zero. In this case, the compensation principle according to the invention only requires that the gradient effect measured by the probe and the compensation effect caused by the compensation winding go together towards zero. A linear relationship or other established relationship need not be fulfilled.

However, if it is not possible to find a location for the installation of the probe for which this condition is met, an adjustment device must be provided. With this, an adjustable constant or field-dependent effect is superimposed on the probe measurement effect, which compensates for the zero difference.

The gain between the measuring effect and the compensation current is also adjustable. This can compensate for unavoidable, annoying induction effects in the vicinity of the probe. But it can also be one special auxiliary compensation winding for the inductively acting fault, which affects the probe, are attached. Their exposure is to be determined and set by means of a magnetic measurement.

The gradient magnetometer can continue. be provided with a signal display in order to make it possible to detect extreme loads or faults. A measuring instrument or an optical or acoustic display device can be used for this purpose. This is particularly necessary when an effect that can no longer be compensated occurs.

The sensor and the electronics are advantageously to be manufactured according to the modular principle.

The compensation described using the gradient measurement method is predestined for protecting ships from gradient mines. However, it can also be used for devices, engines, land vehicles, armored vehicles and for controlling the compensation of interference-free spaces and rooms or for measuring purposes.

The rotating probe makes it possible to dispense with the precision required in the manufacture of the gradient probes currently used. In addition to the elongated sensors, a Hall sensor can also be used for the rotating probe.

The rotary probe is suitable for self-measurement, in particular it can be towed behind a ship or pulled longitudinally or transversely under the ship or attached freely or tensioned or carried out by a dinghy. When dragging through the water, the measurement also benefits from the gyro effect of the rotating probe, which has to be deliberately amplified. It can be driven by the traction current via impellers. In a particularly advantageous manner, the gradient probe can be attached in the sonar dome under a ship.

For compensation according to the invention, it is in principle irrelevant whether the object's own field is created by permanent, inductive or magnetostrictive magnetism. The compensation is also independent of the course, latitude and longitude. It is both for roll effects can also be used for stamping and rolling effects. Alternating fields can also be compensated for. Any change in the own field can be compensated for independently. The rotation probe can also be used to find magnetic objects, ships, submarines, etc. For this purpose, it can be used from ships, aircraft or land vehicles.

Claims (19)

1. A method for compensating for magnetic interference fields of objects, preferably ships, by means of interference-controlled magnetic self-protection systems, the currents flowing in the windings of the system being controlled by differential field probes, characterized in that control loops from the compensation windings with associated differential field probes, integration and power elements be formed and used to compensate for individual interference fields parallel to each other and parallel to the higher-level compensation system of the object. 2. The method according to claim 1, characterized in that the differential field probes are attached at locations where the differential field strengths are always zero when the interference fields determined with the aid of probes (probe rows or probe carpets) are set to optimal compensation i interference field minimums by means of the compensation windings. 3. The method according to claim 1, characterized in that in the presence of local interference fields acting on the differential field probes and not compensable by means of the MES windings, the probe eating effect constant or magnetic field-dependent effects are superimposed. 4. The method according to claim 3, characterized in that interference fields in the vicinity of the differential field probes are compensated for by special auxiliary windings. 5. The method according to claim 1, characterized in that the differential field probes are mounted remotely from the object. 6. The method according to claim 1, characterized in that the probes and / or the electronics are created according to the modular principle. 7. The method according to claim 5, characterized in that the probes are accommodated in the sonar dome of a ship. 8. The method according to claims 1 to 6, characterized in that the method is applied to water and land vehicles and on squares and in rooms. 9. The method according to claim 1, characterized in that a signal device is combined with the differential field probes, with which an exceeding of permissible values or a fault is indicated. 10. Device for carrying out the method according to claim 1 with a differential field probe, which has two sensors whose measuring directions are parallel to the base, characterized in that the probe is arranged rotatably about its longitudinal axis. 11. The device according to claim 10, characterized in that a hydraulic-pneumatic or electric motor serves as a rotary drive for the probe. 12. The device according to claim 10, characterized in that a manual rotation of the probe by means of a handwheel, handle or hand crank is provided. 13. The device according to claim 10, characterized by a rotary drive of the probe by means of wind, propeller or cup cross. 14. Device according to claim 10, characterized by a water flow motor as a rotary drive for the probe. 15. The device according to claim 10, characterized by attenuators, filters or counting stages for eliminating adjustment errors of the probe. 16. The device according to claim 10, characterized by a device for changing the speed of the probe. 17. The device according to claim 10, characterized in that the probe carries out torsional vibrations. 18. The device according to claim 10, characterized in that a sensor of the probe is tilted. 19. Device according to claims 10 to 17, characterized in that inductive, capacitive transmitters or radio transmitters are provided for transmitting the measured values from the rotating probe.

Images