JPS63139280A - Magnetism compensation apparatus - Google Patents

Abstract

PURPOSE:To obtain a compensation apparatus requiring no axial alignment of a compensation coil and three low sensitivity fluxmeters, by providing the low sensitivity fluxmeters, a high sensitivity magnetometer, a constant calculation part, a constant memory part, a compensation quantity calculation part and a subtraction circuit. CONSTITUTION:A constant calculation part 30 calculates the values of a permanent magnetic field Hp, a 3X3 constant matrix A and a 3X3 constant matrix B on the basis of the outputs of low sensitivity fluxmeters 11-13 and the output of a subtraction circuit 60 and a constant from the calculation part 30. A compensation calculation circuit 50 calculates a noise magnetic field D according to a predetermined formula on the basis of the output of the memory part 40 and the outputs of the low sensitivity fluxmeters 11-13. The subtraction circuit 60 inputs the output of the calculation part 50 and that of a high sensitivity magnetometer 20 to perform the subtracting calculation of both outputs. Further, gate switches S1-S3 are gated ON only when the calculation of a constant is performed. Since the output of the subtraction circuit 60 is inputted to the constant calculation part 30, the constant can be calculated more accurately.

Description

[Detailed description of the invention]! Natsu Awakami ■And Separation This invention detects disturbances in the geomagnetic field by installing a magnetic detector on an aircraft, etc., and compensates for disturbances in the geomagnetic field due to the magnetic influence inherent to the aircraft itself when searching for shipwrecks, etc. In order to do this, especially when performing constant calculations,
This invention relates to a magnetic compensation device with an improved input method to a constant calculation unit.

In general, noise magnetic fields generated from the vehicle itself include a permanent magnetic field Hp, an induced magnetic field Hi, and an eddy current magnetic field He.

Permanent magnetic fields are generated by the steel parts of the vehicle itself, induced magnetic fields by soft iron parts, and eddy current fields by electric currents flowing in electrical conductors.

If an external magnetic field is to be accurately measured using a vehicle, such as an airplane, three types of noise magnetic fields based on the vehicle itself must be removed in advance.

Therefore, a highly sensitive magnetic needle is used. Therefore, the noise magnetic field from the vehicle itself sensed by a highly sensitive magnetometer mounted on the vehicle to measure the magnetic field is expressed as follows.

First, it is assumed that the permanent magnetic field in the magnetometer detection section of the high-sensitivity magnetometer is Hp, the induced magnetic field is Hl, and the eddy current magnetic field is He. Here, the permanent magnetic field Hp, the induced magnetic field Ht, and the eddy current magnetic field He
Both are three-dimensional vector quantities.

Since the permanent magnetic field is generated because the vehicle itself is semi-permanently magnetized, Hp is constant.

The induced magnetic field is such that when an object that is easily magnetized is placed in an external magnetic field, it will be magnetized in that direction in proportion to the magnitude of the external magnetic field, so Hi = AE
...It is expressed as ■. Here, E is a three-dimensional vector representing the external magnetic field, and A is a 3×3 constant matrix of the vehicle itself. In addition, an eddy current magnetic field is a field in which a current flows in a conductor in response to a change in an external magnetic field, generating a secondary magnetic field, and the magnitude thereof is proportional to the rate of change over time of the external magnetic field. It is expressed as He=B−dE/dt −··■. Here, dE/dt is the time differential of the external magnetic field E,
B is a vehicle-specific 3×3 constant matrix.

Therefore, assuming that the noise magnetic field of the vehicle itself in the magnetometer detection section is Hn, Hn is expressed as Hn=Hp+AE+B-dE/dt...■. Here, Hn is a three-dimensional vector.

In the conventional system, a compensating coil generates a magnetic field of the same magnitude as Hn and in the opposite direction, and this is applied to the magnetometer detection section to compensate for the noise of the vehicle itself.

The above conventional method will be explained with reference to the drawings.

In Figure 2, 1 is three orthogonal low-sensitivity magnetometers, 2
3 is a constant storage unit, 3 is a noise magnetic field calculation circuit that calculates a noise magnetic field based on the output of the low-sensitivity magnetometer 1 and the output of the constant storage unit 2, 4 is a compensation coil drive circuit, and 5 is three orthogonal The compensation coil 6 is a highly sensitive magnetometer.

Here, the low-sensitivity magnetometer 1 detects the external magnetic field E in equation 0. However, Hp, A, and B in the formula 0 are constants and are stored in the constant storage section 2.

The noise magnetic field calculation circuit 3 takes in the output of the low-sensitivity magnetometer 1, that is, the value of the external magnetic field E, and calculates In expressed by the equation 0. The compensation coil drive circuit 4 converts this value into a current, and the compensation coil 5 generates a magnetic field. The highly sensitive magnetometer 6 detects the vector sum of the magnetic field generated by the vehicle itself and this compensation magnetic field, and thus measures the compensated external magnetic field.

In the conventional method, it is necessary to align the three low-sensitivity magnetometers and the compensation coil with each other, and the degree of alignment depends on the performance of noise compensation. There is a problem in that while it has a direct effect on the alignment, it is difficult to ensure the accuracy of the axis alignment.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a magnetic compensation device that does not require alignment of the compensation coil and three low-sensitivity magnetometers, which was conventionally required.

A magnetic compensation device according to the present invention is a magnetic compensation device that compensates for an induced magnetic field HI, a permanent magnetic field Hp, and an eddy current magnetic field He generated from a vehicle itself, and is a magnetic compensation device that compensates for a 3×3 constant matrix A. , B, if the three-dimensional vector is E, compensation is performed by subtracting the permanent magnetic field Hp, the 3×3 constant matrix A,
The configuration is such that the value of B is calculated based on the low sensitivity magnetometer output and the compensated output signal.

The magnetic compensation device according to the present invention performs constant calculation by inputting the compensated output signal, that is, the output of the subtraction circuit, to the constant calculation section.

Next, in Figure 1, 11.12.13 are three orthogonal low-sensitivity magnetometers;
are the three-directional components of the external magnetic field (geomagnetic field), namely E
The magnitude of x-, E y s E z, in other words, the attitude of the vehicle is detected. Strictly speaking, the low-sensitivity magnetometers 11, 12, and 13 simultaneously detect the earth's magnetic field as well as the amount of change ΔE in the earth's magnetic field based on the noise magnetic field of the vehicle itself, sunken ships, etc., but the latter two quantities are determined by the earth's magnetic field. Since the amount is very small compared to the amount of 11.
12.13 is sufficient to detect only the earth's magnetism among external magnetic fields.

Reference numeral 20 is a high-sensitivity magnetometer that uses, for example, optical magnetic resonance, and this high-sensitivity magnetometer 20 has a variation S10 in the external magnetic field.
(The high-sensitivity magnetometer 20 detects the amount of change in the earth's magnetic field ΔE, the magnetic '!IS based on shipwrecks, etc., and the unique magnetic ID of the vehicle itself, but ΔE is extremely small compared to both, so In reality, the amount of change in the external magnetic field is sufficient as D+S.) 30 is a constant calculation section, and this constant calculation section 30 combines the outputs of the low sensitivity magnetometers 11, 12, and 13 with the outputs of the subtraction circuit 60. Based on the permanent magnetic field Hp and 3×3
Calculate the values of constant matrix A and 3×3 constant matrix B. 40 indicates the output from the constant calculation unit 30, that is, the values of the permanent magnetic field Hp, the 3×3 constant matrix A, and the 3×3 constant matrix B.1. ! A constant storage unit 50 is a compensation calculation unit that calculates D based on the formula (2) based on the output of the constant storage unit 40 and the output of the low sensitivity magnetometers 11, 12, and 13. 60 is a subtraction circuit that inputs the output of the compensation amount calculation unit 50 and the output of the high-sensitivity magnetometer 20 and performs a subtraction calculation.

Note that gate switches S1 and S2 are provided between the low sensitivity magnetometers 11, 12, and 13 and the constant calculation section 30, and between the output side of the subtraction circuit 60 and the constant calculation section 30, respectively. Further, a gate switch S3 is provided between the constant calculation section 30 and the constant storage section 40. These gate switches S
1, S2, and S3 are gated only when performing constant calculation. A method of calculating constants in the magnetic compensation device configured as described above will be explained. However, in the constant calculation section, the permanent magnetic field Hp, 3 × 3 constant matrices A, B
Due to the need to accurately determine the altitude of a vehicle, such as an airplane, the altitude of the vehicle itself is set high in order to avoid the influence of magnetism caused by shipwrecks and the like detected by the highly sensitive magnetic needle.

■Turn on gate switches S1 and S2, gate switch S
3 is turned off, for example, by applying various motions to the aircraft and changing the outputs from the low-sensitivity magnetometers 11, 12, and 13, the constant calculation unit 30 calculates the permanent magnetic field Hp and 3×
Have students calculate the values of three constant matrices A and B.

However, the values of the permanent magnetic field and 3x3 constant matrix determined at this point include various errors that occur during measurement, so instead of Hp, A, and B, the values of the permanent magnetic field and the 3x3 constant matrix are Hp + Δi (p, A + ΔA
, B+ΔB. in this case,? iti compensation calculation unit 50
The output of is zero.

■With the gate switch S3 turned on, the above value Hp
+ΔHpSA+ΔA, , B+ΔB are stored in the constant storage section 40.

■Turn on gate switches S1 and S2, gate switch S
3 is turned off, the aircraft is given various motions again, and the same calculations as above are performed. In this case, the compensation amount calculation unit 50 receives Hp+ΔHp, A+ΔA from the constant storage unit 40.
, B+ΔB are given, the compensation amount calculation unit 50 calculates the equation (2) and inputs D+ΔD to the subtraction circuit 60.

(2) For the reasons mentioned above, the magnetic influence caused by sunken ships and the like is removed from the high-sensitivity magnetometer 20, and therefore only the noise magnetic field of the aircraft itself is output. This high sensitivity magnetometer 2
The output of 0 is input to the subtraction circuit 60.

(2) The subtraction circuit 60 subtracts the two inputs, outputs ΔD, and inputs this output ΔD to the constant calculation section 30 via the gate switch S2, and the constant calculation section 30 performs the same calculation as described above. A more accurate constant than before, namely Hp+Δ2Hp,
They are stored in the constant storage unit 40 as A+Δ2A, , B+Δ2B.

■Turn on gate switch S3. As a result, the constant storage section 40 stores the above Hp+Δ2Hp, A+Δ2A, B+Δ2
B is input to the compensation amount calculation section 50.

■Compensation amount calculation unit 50 calculates the above Hp+Δ2HI)% A+
Using Δ2A, B+Δ2B as new constants, calculation is performed using the equation (2), and the result is stored in the constant storage unit 40.

By repeating the procedure 0 or more times, it is possible to calculate a constant more accurately, and it is possible to accurately calculate the noise magnetic field according to the formula (2).

As described above, the magnetic compensation device according to the present invention is configured so that the output of the subtraction circuit is input to the constant calculation section, so that more accurate constant calculation is possible.

[Brief explanation of the drawing]

FIG. 1 shows a block diagram of an embodiment of the present invention, and FIG. 2 shows a block diagram of a conventional magnetic compensation device. 11.12.13...Low-sensitivity magnetometer, 20...High-sensitivity magnetic needle, 30...Constant calculation section, 40...Constant symbol,! ! Part, 50... Compensation amount calculation part, 60... Subtraction circuit, Sl, S2, S3... Gate switch. Patent applicant: Toru Ryoshita, Director General, Technology Research Headquarters, Defense Agency

Claims (1)

[Claims] (1) A low-sensitivity magnetometer that measures the three-directional components of earth's magnetism, Ex, Ey, and Ez, a high-sensitivity magnetometer that measures the magnitude of the external magnetic field, a constant calculation section, and the contents from the constant calculation section are stored. Based on the output from the constant storage section, the low-sensitivity magnetometer, and the constant storage section, D=(1/|E|)E・[Hp+AE+B(dE/dt
)], and a subtraction circuit that subtracts the output from the compensation amount calculation unit and the high-sensitivity magnetometer. A magnetic compensation device characterized in that the output from the low-sensitivity magnetometer is inputted, and the output of the subtraction circuit is inputted via a gate switch S3.