JPH04111404A - Method for demagnetizing hull - Google Patents

Abstract

PURPOSE:To mathematically efficiently demagnetize a hull and, at the same time, to minimize the magnetic field in a specific direction by finding the magnetic moment of the hull by calculating dipole moments from the three component data of magnetic fields. CONSTITUTION:A plurality of magnetic sensors D1-DN are arranged below a hull 1. The magnetic field and coil effect of the hull in an un-demagnetized state are calculated as a plurality of dipole moments from the three components Hx, Hy, and Hz of the magnetic fields detected by the magnetic sensors. The magnetic moments are reduced by calculating the dipole moments as a magnetic source. In this demagnetizing method, the magnitude of the magnetic source becomes clear, since the plurality of dipole moments at a specific position in the hull are specified from the magnetism detected data on three axes of Hx, Hy, and Hz. The coil effect can also be specified from the moment of the specified position.

Description

[Detailed description of the invention] (b) Industrial application fields The present invention relates to a method for demagnetizing a ship's body (ship).

(B) Conventional technology The conventional method for demagnetizing a ship's hull is to place a plurality of magnetic sensors under the ship's hull, first determine the magnetic field of each magnetic sensor in a state where the degaussing coil is not energized, that is, in a non-demagnetized state, and then The method used was to energize the demagnetizing coils to obtain the coil effects of each coil (M, L, and A coils), and to minimize this H22 component by subtracting it from the magnetic field in the non-demagnetizing state.

(c) Problems to be Solved by the Invention The conventional degaussing method described above only minimizes the magnetic field H8 of the ship's hull, but does not even mention its magnetic source. Therefore, no emphasis was placed on components H,,H. In other words, demagnetizing only H8 in the lower part of the hull has the effect of reducing the magnetic source in the hull and also makes the dipole orientation broader in the magnetic field in the lower part of the hull. , the sides could not be demagnetized to that extent.

This invention has been made in view of the above-mentioned problems, and aims to provide a method for demagnetizing a ship's hull that can reduce the size of the magnetic source itself and demagnetize not only the lower part of the ship but also the upper and side parts of the ship. Stay with purpose and one.

(d) Means and operation for solving the problem The ship hull demagnetization method of the present invention includes arranging a plurality of magnetic sensors under the ship hull, and detecting three components (H, , H, ,
H, ), the magnetic field and coil effect of the undemagnetized state of the ship's hull are calculated as multiple dipole moments at specified positions on the ship, and the calculation of the dipole moment, which is the magnetic source, is
I am trying to make the moment small.

In this degaussing method, a plurality of dipole moments at specified positions within the hull are set to H, H,,H.

Since it is identified using three-axis magnetic detection data, the size of the magnetic source becomes clear. Coil effects can also be identified by the moment at this identified position.

The magnetic source itself is reduced by optimizing the moment of each coil effect using a processing method such as the method of least squares from the dipole moment of the magnetic field. Furthermore, by intentionally changing the orientation of the moment, the magnetic field in a specific direction can be reduced intensively.

(E) Examples The present invention will be explained in more detail with reference to Examples below.

FIG. 2 is a diagram showing the positional relationship between the hull and the magnetic sensor in which the present invention is implemented. In the figure, a plurality of magnetic sensors D, , D,
,..., D8 is installed.

These magnetic sensors D, , D, ,..., DH are H,
, H, , H, three component magnetic fields can be detected. Also, although not shown in the figure, the hull 1 has a demagnetizing coil (
M, A, L) [see Figure 4].

A system block diagram for calculating the optimum ampere-turn of the degaussing coil (M, ASL) is shown in FIG. This system consists of magnetic sensors D, D2, ..., DN, a multiplexer 2 for time-sequentially taking in the detection signals from these magnetic sensors D1, D2, ...DH, and converting each detection signal into a digital signal. A/D converter 3 to convert,
CPU4 that controls data import and executes various calculations
, a key manual section 5 for inputting operation commands, a memory 6 for storing data and the like, and a display 7 for displaying output data and the like. Originally, these hardware configurations in this system are not particularly new.

Next, optimization processing for performing demagnetization in the above system will be described with reference to flowcharts shown in FIGS. 1(A) and 1(B).

First, the data of the three components H, H, H of the magnetic sensors DI, D2, . , water depth, ship position data, and dipole position and number are input (step ST2.5T3). Then, the dipole moment is calculated from these input values (step 5T4).

The calculation is H8-αM, I+βM y H+γM□+...(α,
β, T: water depth, ship position function) As a result, by the least squares method, n dipole moments MXI, M93, M□, ..., M xll, M
Calculate y, 1, Mo.

Next, while the coils of the hull 1 are energized, the data of the three components H,, Hy, H, of the measured values of the magnetic sensors DI, Dt, ..., D8, which are the effects of each coil, are input (step 5T5). ), the water depth, ship position data, dipole position and number are input (step ST6.5T7), and the AT (ampere turn) of each coil is also manually input (step 578). Then, using a calculation formula similar to step ST4, dipole moments M'', M''MM-(MM
I, M”, M” ・-2M N −, MM −, M
M-) is calculated (step 5T9). Similarly, M L 1'', ML'', and ML'' are calculated for the A coil unit M'', MAffi, MAII, and L coil.

Then, the following formula % is established from the dipole moment in the non-demagnetized state found in step ST4 and the dipole moment corresponding to the coil effect found in step ST9.
Read the formula %, use the least duplex method to find A, B, ... (AT), and output this A, B, ... (Step 5T10)
).

Note that if there is a direction in which the magnetic field is particularly desired to be minimized, that direction is input (step 5T11). If the direction is input, judge the orientation of the moment (step 5Ti2). If you want to minimize it in the upward direction, adjust the moment 1-AT in the direction shown in FIG. 5(A) ( Step 5T13). In this case, for example, if the top and bottom ratios are about 1 and 3, the magnetic field will be as shown in Figure 5 (B).
It will be as shown below. Furthermore, if l is particularly desired to be minimized in the downward direction, the moment orientation is adjusted so that the moment becomes smaller in the downward direction (step 5T14).

(f) Effect of the invention: According to this invention, H
By calculating the dipole moment using the X, H, and component data, it is possible to obtain an accurate magnetic moment of the ship's hull, and the demagnetization work can be carried out mathematically and efficiently. Also, it is possible to minimize the magnetic field in a specific direction,
You can control the remaining magnetic field after locating the degaussing coil. Furthermore, since the induced and permanent components of the magnetic source can be separated and divided into each component of the moment, azimuth extrapolation (D
A C-Degaussing Auto Cont.
Rot) can also be performed by extrapolation of the essential magnetic source rather than the conventional demagnetization proportional to the trigonometric function of H, so the demagnetization performance is improved.

[Brief explanation of drawings]

1(A) and 81(B) are flowcharts for explaining the degaussing optimization process in a system according to an embodiment of the present invention, and FIG. 2 shows the positional relationship between the hull and the magnetic sensor. Figure 3 is a block diagram of a system in which the present invention is implemented, Figure 4 is a diagram schematically showing a degaussing coil installed in the hull, and Figure 5 is a block diagram of a system in which the present invention is implemented. Momen (
6(A) is a diagram illustrating an example of the orientation of moment, and FIG. 6(B) is a diagram illustrating the relationship between the upper and lower magnetic fields in the illustrated orientation. It is a diagram. 1: Hull, 48CPtJ. D, -D, ...DH: Magnetic sensor, M-A-
L: Demagnetizing coil. Figure (B) Figure (A)

Claims (1)

[Claims] (1) Multiple magnetic sensors are placed under the hull, and the three components (H_x, H_y, H_z) of the magnetic field detected by these magnetic sensors are
), a method of demagnetizing hull magnetism in which the magnetic field and coil effect of the undemagnetized state of the hull are calculated as multiple dipole moments at specified positions on the hull, and the moments are reduced by calculating the dipole moment, which is the magnetic source. .