JP2001083224A - Method and apparatus for measuring magnetic field - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately measure a magnetic flux density even during rotating. SOLUTION: The apparatus for measuring a magnetic field comprises a three-axis magnetic sensor TMM having sensitivity axes in directions x, y and z, a two-axis acceleration sensor having a sensitivity axis in the direction z so as to be rotatable at the x-axis used as a rotary axis. Thus, a magnetic flux density of each direction is calculated by obtaining a low frequency component of a product of the output of the x-axis sensor MMX, the output of the x-axis sensor MMY and the output of the z-axis sensor MMZ and a low frequency component of a product of the output of the z-axis sensor MMX and the output of the z-axis sensor AMZ, and correcting the respective frequency components according to an oblique angle and an angle of a precession.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic field detecting method and apparatus for detecting a target magnetic field while a magnetic detecting means is rotating, and is applied to a case where a magnetic field near a drill head is detected in a so-called horizontal drilling method. It is preferable.

[0002]

2. Description of the Related Art In a so-called horizontal drilling method, a drill pipe having a drilling means at its tip is pushed into the ground by a propulsion means for pushing the drill pipe into the ground. Then, the magnetic field is detected by a magnetic sensor in an underground drill head, and a position based on the magnetic field source is calculated from the detected direction and intensity of the magnetic field. Here, when a direct current is used as a magnetic field generation source, it is necessary to measure the magnetic field twice with the current direction reversed at the same place in order to remove the influence of geomagnetism. When the magnetic field source is an alternating current, it is not affected by geomagnetism, but it is often necessary to repeat the magnetic field measurement a plurality of times to obtain a sufficient signal-to-noise ratio. In the case of performing straight excavation, the drill head needs to be rotated, so conventionally, the excavation is interrupted, and the rotation of the drill head is stopped to perform measurement.

With reference to FIGS. 11 and 12, such a conventional magnetic field measuring method will be described. FIG. 11 is a diagram showing an arrangement of sensors in a conventional magnetic field measurement method. In the figure, AMX is an x-direction acceleration sensor, AMY is a y-direction acceleration sensor, and AMZ is a z-direction acceleration sensor.
A three-axis acceleration sensor TAM is constituted by two acceleration sensors. MMX is an x-direction magnetic sensor, MMY is a y-direction magnetic sensor, and MMZ is a z-direction magnetic sensor.
The three magnetic sensors constitute a three-axis magnetic sensor TMM. Here, three-axis magnetic sensor TMM and three-axis acceleration sensor T
AM has a fixed mutual posture. That is,
Sensitivity axis of x direction magnetic sensor MMX and x direction acceleration sensor AMX
, The sensitivity axis of the y-direction magnetic sensor MMY, the sensitivity axis of the y-direction acceleration sensor AMY, the sensitivity axis of the z-direction magnetic sensor MMZ, and the sensitivity axis of the z-direction acceleration sensor AMZ are held in parallel. Hereinafter, a pair of the three-axis magnetic sensor TMM and the three-axis acceleration sensor TAM will be referred to as a sensor system and will be referred to.

FIG. 12 is a diagram showing a flow of processing in the conventional measuring method. In this conventional measurement method, 3
3-axis magnetic sensor TMM directly from the output of the axis acceleration sensor TAM
And the output of the three-axis magnetic sensor TMM is corrected. The coordinate system fixed to the sensor system is called a sensor coordinate system. First, it is assumed that the z-axis of the sensor system is oriented in a direction opposite to the vertical. That is, it is assumed that the x-axis and the y-axis of the sensor system are horizontal. The sensor coordinate system at this time is coordinate system 1
I will call it. First, it is assumed that the sensor system is rotated around the y-axis of the coordinate system 1 by an angle θy. That is, it is assumed that the drill head is inclined from the horizontal. The sensor coordinate system after this rotation will be referred to as a coordinate system 2. Further, it is assumed that the sensor system is rotated around the x-axis of the coordinate system 2 by an angle θx, and the rotated coordinate system is referred to as a coordinate system 3.

At this time, the acceleration detected by the three-axis acceleration sensor TAM is

(Equation 1) It is. Here, G is the gravitational acceleration. Therefore,
The rotation angles θx and θy are

(Equation 2) Can be obtained by

From these angles, a transformation matrix R for obtaining the magnetic flux density before rotation can be created.

(Equation 3) However,

(Equation 4) It is. Assuming that a magnetic flux vector composed of outputs of the three-axis magnetic sensor TMM is Bs, a magnetic flux density vector Bw expressed in a coordinate system before rotation is obtained by using the conversion matrix R.

(Equation 5) More can be obtained. Here, the matrix R ⁻¹ is an inverse matrix of the transformation matrix R.

[0007]

However, this conventional measuring method has the following problems. That is, when the measurement error of the measured value of the magnetic flux density is sufficiently low, the position of the drill head can be accurately calculated by using the magnetic flux density obtained by the above-described conventional method. It is necessary to reduce the measurement error by repeating the measurement a plurality of times and taking the average. For this,
It is necessary to interrupt the excavation and perform the measurement, which reduces the work efficiency. In addition, a method of calculating a position using the magnetic flux density obtained by one measurement, repeating this plural times, and averaging the calculated positions to remove an error is possible in principle, but generally, Since the calculation of the position is based on a method of obtaining an optimal solution by repetitive calculation, if the measurement error is large, the possibility that the repetitive calculation does not converge increases. Even if the convergence occurs, the error of the calculated position is usually larger than the error of the magnetic flux density. Therefore, this method is not a practical method.

In the case of excavating soil with gravel or cobblestone, an impulsive acceleration is applied to the acceleration sensor, and unless a high-frequency component is removed by a low-pass filter, an error in measuring the attitude of the drill head increases. . However, when a low-pass filter is used, the drill head rotates several times per second, so that an error due to a phase delay in posture detection becomes a problem. The above problems are when a sufficiently high-accuracy acceleration sensor is used. However, since the drill head of the horizontal drilling method has a severe restriction on the diameter, an acceleration sensor that fits inside it has a high performance. However, there is also a problem that such products are difficult to obtain or extremely expensive.

In view of the above situation, the present invention is capable of measuring a magnetic flux density with high accuracy even while the drill head is rotating, and has sufficient accuracy even with an inexpensive acceleration sensor manufactured by so-called micromachining. It is an object of the present invention to provide a magnetic field measuring method and device capable of measuring the magnetic field.

[0010]

In order to achieve the above object, a magnetic field measuring method according to the present invention comprises: a three-axis magnetic sensor having three magnetic sensors each having a sensitivity axis in three directions orthogonal to each other; A two-axis acceleration sensor having two acceleration sensors having sensitivity axes in two orthogonal directions, respectively, such that the sensitivity axis of the two-axis acceleration sensor is parallel to the two sensitivity axes of the three-axis magnetic sensor. The three-axis magnetic sensor and the two-axis acceleration sensor are arranged spatially, and the three-axis magnetic sensor and the two-axis acceleration sensor are simultaneously rotated while maintaining a mutual attitude, with a sensitivity axis of a first acceleration sensor of the two acceleration sensors as a rotation axis. A magnetic field measuring method for measuring a static magnetic field using a measuring means adapted to be able to perform the method, wherein a magnetic sensor having a sensitivity axis in the rotation axis direction is a first magnetic sensor, Chino sensitivity axis of the magnetic sensor orthogonal to the sensitivity axis of the second acceleration sensor and the second magnetic sensor, when the remaining magnetic sensors and the third magnetic sensor,
A magnetic field in the direction of the rotation axis is calculated from a low frequency component of the output of the first magnetic sensor, and a low frequency component of a product 1, which is a product of an output of the second acceleration sensor and an output of the second magnetic sensor. And the low frequency component of the product 2, which is the product of the output of the second acceleration sensor and the output of the third magnetic sensor,
And calculating a magnetic field in a second direction perpendicular to the rotation axis and a magnetic field in a third direction perpendicular to the rotation axis and the rotation axis, the magnetic field being included in a plane perpendicular to the rotation axis.

When the AC component of the output of the second acceleration sensor divided by the gravitational acceleration is squared, and the square root of 2 of the square root of the low frequency component is set as cosine 1, the product of the product 1 is obtained. From the low frequency component divided by the cosine 1,
The magnetic field in the second direction is calculated by calculating the magnetic field in the third direction and dividing the low frequency component of the product 2 by the cosine 1. Alternatively, the value obtained by dividing the AC component of the output of the second acceleration sensor by the gravitational acceleration is 2
Raised to the power of 2, the square root of 2 of the square root of the low frequency component is taken as cosine 1, the angle 1 with cosine 1 is calculated, and the AC component of the output of the first acceleration sensor is divided by the gravitational acceleration. When the low frequency component divided by the sine of the angle 1 is cosine 2, the magnetic field in the rotation axis direction is calculated from the low frequency component of the output of the first magnetic sensor divided by the cosine 2. Calculating the magnetic field in the third direction from the low frequency component of the product 1 divided by the cosine 1 and the cosine 2 and calculating the magnetic field in the third direction by dividing the low frequency component of the product 2 by the cosine 1 The magnetic field in the second direction is calculated. Alternatively, the AC component of the output of the second acceleration sensor divided by the gravitational acceleration is squared, and the square root of 2 of the square root of the low frequency component is set as cosine 1, and the output of the first acceleration sensor is output. The square root of the low frequency component of the square of the AC component divided by the gravitational acceleration divided by the square of the cosine 1 is sine 2, and the square root of the square of the sine 2 subtracted from 1 is the cosine 2 When calculating, the magnetic field in the rotation axis direction is calculated from the low frequency component of the output of the first magnetic sensor divided by the cosine 2, and the low frequency component of the product 1 is divided by the cosine 1 and the cosine 2. , The magnetic field in the third direction is calculated, and the magnetic field in the third direction is calculated from the value obtained by dividing the low frequency component of the product 2 by the cosine 1.

Still another method of measuring a magnetic field according to the present invention is a magnetic field measuring method having three sensitivity axes in three directions orthogonal to each other.
A three-axis magnetic sensor having three magnetic sensors, and one acceleration sensor spatially arranged so that the sensitivity axis is parallel to one of the three magnetic sensors;
An axis parallel to any one of the two sensitivity axes orthogonal to the sensitivity axis of the acceleration sensor among the three-axis magnetic sensors is a rotation axis, and the three-axis magnetic sensor and the acceleration sensor are mutually connected. A magnetic field measuring method for measuring a static magnetic field using measuring means adapted to be able to rotate simultaneously while maintaining a posture, wherein a magnetic sensor having a sensitivity axis in a direction of the rotation axis is a first magnetic sensor. Of the remaining magnetic sensors, when the magnetic sensor whose sensitivity axis is orthogonal to the acceleration sensor is the second magnetic sensor, and the other magnetic sensors are the third magnetic sensors, the output of the first magnetic sensor is Calculate the magnetic field in the rotation axis direction from the low frequency component,
From the low frequency component of the product of the output of the acceleration sensor and the output of the third magnetic sensor and the low frequency component of the product of the output of the acceleration sensor and the output of the second magnetic sensor, A magnetic field in a second direction that is included in a plane extending in the direction and is orthogonal to the rotation axis;
Is calculated in a third direction orthogonal to the direction of.

Still another magnetic field measuring method according to the present invention comprises a three-axis magnetic sensor having three magnetic sensors each having a sensitivity axis in three directions orthogonal to each other, and a sensitivity axis in two directions orthogonal to each other. A two-axis acceleration sensor having two acceleration sensors having the following two spatially arranged so that the sensitivity axis of the two-axis acceleration sensor and the two sensitivity axes of the three-axis magnetic sensor are parallel to each other; A measurement performed so that the sensitivity axis of the first acceleration sensor among the acceleration sensors can be a rotation axis, and the three-axis magnetic sensor and the two-axis acceleration sensor can be simultaneously rotated while maintaining their mutual postures. A magnetic field measuring method for measuring an alternating magnetic field of a predetermined frequency by using a means, wherein a magnetic sensor having a sensitivity axis in a direction of the rotation axis is a first magnetic sensor; When the magnetic sensor whose sensitivity axis is orthogonal to the sensitivity axis of the second acceleration sensor is the second magnetic sensor, and the remaining magnetic sensors are the third magnetic sensors, the predetermined magnetic field of the output of the first magnetic sensor is determined. The magnetic field in the rotation axis direction is calculated from the frequency component, and the predetermined frequency component of the product 1 which is a product of the output of the second acceleration sensor and the output of the second magnetic sensor, and the second acceleration From a component of the predetermined frequency of a product 2 which is a product of an output of the sensor and an output of the third magnetic sensor, a component in a second direction perpendicular to the rotation axis, which is included in a plane extending in the vertical direction with respect to the rotation axis, A magnetic field and a magnetic field in a third direction orthogonal to the rotation axis and the second direction are calculated.

Furthermore, when the AC component of the output of the second acceleration sensor divided by the gravitational acceleration is squared, and the square root of the square root of the component of the predetermined frequency is 2 as cosine 1, The magnetic field in the third direction is calculated from the value obtained by dividing the component of the predetermined frequency of the product 1 by the cosine 1 and the component of the predetermined frequency of the product 2 is calculated by the cosine 1
The magnetic field in the second direction is calculated from the value divided by Alternatively, the AC component of the output of the second acceleration sensor divided by the gravitational acceleration is squared, and the square root of 2 times the square root of the component of the predetermined frequency is defined as cosine 1, and the cosine 1 is defined as cosine. When an angle 1 to be calculated is calculated and an AC component of the output of the first acceleration sensor is divided by a gravitational acceleration, a component obtained by dividing the component of the predetermined frequency by a sine of the angle 1 is set as a cosine 2, The magnetic field in the direction of the rotational axis is calculated by dividing the component of the predetermined frequency of the output of the magnetic sensor 1 by the cosine 2, and the component of the predetermined frequency of the product 1 is calculated by the cosine 1 and the cosine 2. From the division, the magnetic field in the third direction is calculated, and the component of the product 2 at the predetermined frequency is divided by the cosine 1,
The magnetic field in the second direction is calculated. Alternatively, the AC component of the output of the second acceleration sensor divided by the gravitational acceleration is squared, and the square root of 2 times the square root of the component of the predetermined frequency is set as cosine 1, and the first acceleration is calculated. The square root of the component of the predetermined frequency of the square of the output of the sensor divided by the gravitational acceleration divided by the square of the cosine 1 is defined as a sine 2, and the square of the sine 2 is subtracted from 1. When the square root of the object is cosine 2, a magnetic field in the direction of the rotation axis is calculated from a value obtained by dividing the component of the predetermined frequency of the output of the first magnetic sensor by the cosine 2,
A magnetic field in the third direction is calculated from a value obtained by dividing the component of the predetermined frequency of the product 1 by the cosine 1 and the cosine 2, and the component of the predetermined frequency of the product 2 is divided by the cosine 1. From the result, the magnetic field in the third direction is calculated.

Still another magnetic field measuring method according to the present invention is directed to a three-axis magnetic sensor having three magnetic sensors each having a sensitivity axis in three directions orthogonal to each other, and the three magnetic sensors having three sensitivity axes. One of the three-axis magnetic sensors, two of which are orthogonal to the sensitivity axis of the acceleration sensor. An axis parallel to any one of the axes is set as a rotation axis, and the predetermined axis is measured using a measuring unit configured to be able to simultaneously rotate the three-axis magnetic sensor and the acceleration sensor while maintaining a mutual attitude. A magnetic sensor having a sensitivity axis in the rotation axis direction as a first magnetic sensor, and among the remaining magnetic sensors, the sensitivity axis is orthogonal to the acceleration sensor. When the magnetic sensor is the second magnetic sensor and the other magnetic sensor is the third magnetic sensor, the magnetic field in the direction of the rotation axis is calculated from the component of the predetermined frequency in the output of the first magnetic sensor. The predetermined frequency component of the product of the output of the acceleration sensor and the output of the third magnetic sensor and the predetermined frequency component of the product of the output of the acceleration sensor and the output of the second magnetic sensor Calculating a magnetic field in a second direction orthogonal to the rotation axis and a magnetic field in a third direction orthogonal to the rotation axis and the second direction, the magnetic field being included in a plane perpendicular to the rotation axis and extending perpendicularly to the rotation axis; It is.

Further, in each of the magnetic field measuring methods, the measuring means is stored in a horizontal drilling excavating means or a storage part provided in the vicinity thereof, and measures the magnetic field near the storage part. Is what is being done. Still further, the measuring means is stored in a horizontal drilling method drilling means or a storage part provided in the vicinity thereof, and the rotation is given by rotation of a drill pipe.

Further, the magnetic field measuring apparatus of the present invention is a magnetic field measuring apparatus for measuring a static magnetic field, wherein the magnetic field measuring apparatus has three magnetic sensors having sensitivity axes in three directions orthogonal to each other. A two-axis acceleration sensor having two acceleration sensors each having a sensitivity axis in two directions orthogonal to each other, such that the sensitivity axis of the two-axis acceleration sensor is parallel to the two sensitivity axes of the three-axis magnetic sensor. The three-axis magnetic sensor and the two-axis acceleration sensor are simultaneously rotated while maintaining the mutual attitude, with the sensitivity axis of the first acceleration sensor of the two acceleration sensors as the rotation axis. And a magnetic sensor having a sensitivity axis in the rotation axis direction.
A magnetic sensor whose sensitivity axis is perpendicular to the sensitivity axis of the second acceleration sensor.
Means for calculating the magnetic field in the direction of the rotation axis from a low-frequency component of the output of the first magnetic sensor, wherein the second magnetic sensor is a third magnetic sensor; and the second acceleration sensor From the low frequency component of the product 1, which is the product of the output of the second magnetic sensor, and the low frequency component of the product 2, which is the product of the output of the second acceleration sensor and the output of the third magnetic sensor. Means for calculating a magnetic field in a second direction orthogonal to the rotation axis and a magnetic field in a third direction orthogonal to the rotation axis and the second direction, the magnetic field being included in a plane extending perpendicularly to the rotation axis. Have

Still another magnetic field measuring device of the present invention is a magnetic field measuring device for measuring a static magnetic field, wherein the three-axis magnetic sensor has three magnetic sensors each having a sensitivity axis in three directions orthogonal to each other. And one acceleration sensor spatially disposed such that a sensitivity axis is parallel to one of the three magnetic sensors, and the acceleration of the three-axis magnetic sensor 2 perpendicular to the sensitivity axis of the sensor
Measuring means configured to be capable of rotating the three-axis magnetic sensor and the acceleration sensor at the same time while maintaining a mutual attitude, with an axis parallel to any one of the sensitivity axes as a rotation axis. A magnetic sensor having a sensitivity axis in the rotation axis direction as a first magnetic sensor, and a magnetic sensor having a sensitivity axis orthogonal to the acceleration sensor as a second magnetic sensor among the remaining magnetic sensors; Is a third magnetic sensor, means for calculating the magnetic field in the rotation axis direction from the low frequency component of the output of the first magnetic sensor, and the output of the acceleration sensor and the output of the third magnetic sensor From the low frequency component of the product of the low frequency component of the product of the product of the acceleration sensor and the output of the second magnetic sensor, a second component perpendicular to the rotation axis that is included in a plane extending vertically to the rotation axis Who Of those having a means for calculating a magnetic field in a third direction perpendicular to the magnetic field and the rotation axis and the second direction.

Still another magnetic field measuring apparatus according to the present invention is a magnetic field measuring apparatus for measuring an alternating magnetic field of a predetermined frequency, comprising three magnetic sensors having sensitivity axes in three directions orthogonal to each other. A two-axis acceleration sensor having a three-axis magnetic sensor and two acceleration sensors each having a sensitivity axis in two directions orthogonal to each other, a sensitivity axis of the two-axis acceleration sensor and two sensitivities of the three-axis magnetic sensor The three-axis magnetic sensor and the two-axis acceleration sensor are disposed spatially so that their axes are parallel to each other, and the sensitivity axis of the first acceleration sensor of the two acceleration sensors is the rotation axis. A first magnetic sensor includes a measuring unit configured to be able to rotate simultaneously while maintaining a posture, and a magnetic sensor having a sensitivity axis in the rotation axis direction. When the magnetic sensor whose axis is orthogonal to the sensitivity axis of the second acceleration sensor is the second magnetic sensor, and the remaining magnetic sensors are the third magnetic sensors, the predetermined frequency of the output of the first magnetic sensor is used. Means for calculating the magnetic field in the direction of the rotation axis from the component of the second component, and a product 1 which is a product of the output of the second acceleration sensor and the output of the second magnetic sensor.
From the component of the predetermined frequency of the product of the predetermined frequency, the product of the output of the second acceleration sensor, and the output of the third magnetic sensor. Means for calculating a magnetic field in a second direction orthogonal to the rotation axis and a magnetic field in a third direction orthogonal to the rotation axis and the second direction.

Still another magnetic field measuring apparatus according to the present invention is a magnetic field measuring apparatus for measuring an alternating magnetic field of a predetermined frequency, comprising three magnetic sensors having sensitivity axes in three directions orthogonal to each other. A three-axis magnetic sensor having a three-axis magnetic sensor and an acceleration sensor spatially arranged so that a sensitivity axis is parallel to one of the three magnetic sensors. Of the two, the axis parallel to any one of the two sensitivity axes orthogonal to the sensitivity axis of the acceleration sensor is set as a rotation axis, and the three-axis magnetic sensor and the acceleration sensor are maintained in a mutual attitude. Measuring means capable of rotating at the same time and a magnetic sensor having a sensitivity axis in the direction of the rotation axis are defined as a first magnetic sensor, and among the remaining magnetic sensors, a magnetic sensor whose sensitivity axis is orthogonal to the acceleration sensor is used. The sensor and the second magnetic sensor, when the other magnetic sensor and the third magnetic sensor, the first
Means for calculating the magnetic field in the rotation axis direction from the component of the predetermined frequency of the output of the magnetic sensor; and the component of the predetermined frequency of the product of the output of the acceleration sensor and the output of the third magnetic sensor. From the component of the predetermined frequency of the product of the output of the acceleration sensor and the output of the second magnetic sensor, a magnetic field in a second direction, which is included in a plane extending perpendicularly to the rotation axis and perpendicular to the rotation axis, Means for calculating a magnetic field in a third direction orthogonal to the rotation axis and the second direction.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The magnetic field measuring method and apparatus of the present invention can be applied to both the case of detecting a static magnetic field and the case of detecting an AC magnetic field of a predetermined frequency. The case where a static magnetic field is detected will be described. When a magnetic field having a predetermined frequency is measured, as described later, a frequency component may be extracted instead of a low frequency component in the following description.

In the magnetic field measuring method of the present invention, three magnetic sensors are arranged so that their sensitivity axes are orthogonal to each other. One of them has the sensitivity axis parallel to the axis of rotation of the drill head. The direction of the rotation axis is the x-axis, and the direction parallel to the plane extending vertically from the x-axis and perpendicular to the rotation axis is z.
The direction of the right-handed system orthogonal to the x-axis and the z-axis is defined as the y-axis direction. This definition of the coordinate system includes a case where the coordinate system is already inclined from horizontal. The three acceleration sensors are arranged so that their sensitivity axes are orthogonal to each other, and each acceleration sensor is parallel to the x-axis, y-axis, and z-axis, respectively. For the sake of simplicity, in this state, the acceleration sensors whose sensitivity axes are parallel to the x-axis, y-axis, and z-axis are called an x-direction acceleration sensor, a y-direction acceleration sensor, and a z-direction acceleration sensor, respectively. Similarly, for the magnetic sensor, the x-direction magnetic sensor, the y-direction magnetic sensor,
It is referred to as a directional magnetic sensor.

In the magnetic field measuring method for measuring a static magnetic field according to the present invention, the z-direction component of the magnetic flux density is determined from the low frequency component of the product of the outputs of the z-direction magnetic sensor and the y-direction acceleration sensor. The y-direction component of the magnetic flux density is determined from the low frequency component of the product of the sensor outputs. Furthermore, x
From the low frequency component of the output of the directional magnetic sensor, the magnetic flux density x
Find the directional component. In addition, an effective inclination from horizontal taking into account the influence of the swinging motion (precession motion) is obtained from the low-frequency component of the square of the output of the z-direction acceleration sensor or the y-direction acceleration sensor. The components in the z and y directions are corrected. Further, the influence of the swing motion is estimated based on the low-frequency component of the square of the output of the x-direction acceleration sensor, and the x-direction component of the magnetic flux density is corrected.

Hereinafter, each embodiment of the present invention will be described in detail. FIG. 1 shows an example of the arrangement of sensors in one embodiment of the magnetic field measuring method of the present invention. In the figure, AMX is an x-direction acceleration sensor, and AMZ is a z-direction acceleration sensor. A two-axis acceleration sensor DAM is constituted by the AMX and the AMX. MMX is an x-direction magnetic sensor, MMY is a y-direction magnetic sensor, MMZ is a z-direction magnetic sensor, and these constitute a three-axis magnetic sensor TMM.

As described above, according to the magnetic field measuring method of the present invention,
Unlike the conventional method described above, the object can be achieved by using a two-axis acceleration sensor. By the way, in the drill head of the horizontal drilling method, since the drill head has directionality, it is necessary to know both the inclination angle and the rotation angle of the drill head. Of course, if a two-axis acceleration sensor is used, this object can be achieved. However, when the inclination is detected by the acceleration sensor, the resolution of the angle measurement is poor when the sensitivity axis is nearly parallel to the direction of gravity. is there.
For this reason, a three-axis acceleration sensor may be used. The present invention can naturally be applied to this case as well. Also,
The output of the z-direction magnetic sensor MMZ used in the present invention does not include a DC component. If there is a DC component, the DC component needs to be cut off by a capacitor or the like. Although this appears to be a drawback of the present invention, it is a significant advantage. Small acceleration sensors made by micromachining have a large offset when no acceleration is applied,
In addition, the temperature fluctuation of the offset and the fluctuation over time are large.
Therefore, in the conventional method for measuring a DC component, sufficient measurement accuracy cannot be obtained or complicated temperature compensation is required. On the other hand, even in such a small acceleration sensor, the sensitivity is often much more stable than the offset. Since a direct current component is not required in the present invention, accurate measurement is possible even with a small acceleration sensor made by such micromachining.

Now, referring to FIG. 1, the three-axis magnetic sensor
The TMM and the two-axis acceleration sensor DAM are held with their mutual postures fixed. That is, the sensitivity axis of the x-direction magnetic sensor MMX and the sensitivity axis of the x-direction acceleration sensor AMX, the sensitivity axis of the z-direction magnetic sensor MZ, and the sensitivity axis of the z-direction acceleration sensor AMX are respectively parallel. The sensitivity axis of the y-direction magnetic sensor MMY is orthogonal to these two directions. Hereinafter, a pair of the three-axis magnetic sensor TMM and the two-axis acceleration sensor DAM will be referred to as a sensor system and will be referred to. The coordinate system fixed to the sensor system is called a sensor coordinate system.

First, a coordinate system for describing a sensor system targeted by the present invention and the movement of the sensor system will be described (see FIG. 1B). First, it is assumed that the z-axis of the sensor system (sensor coordinate system) faces in the direction opposite to the vertical. That is, it is assumed that the x-axis and the y-axis of the sensor system are horizontal. Also, the sensor system rotates about an axis parallel to the x-axis. That is, the rotation axis of the drill head is parallel to the x-axis. The sensor coordinate system at this time is called a coordinate system 1. First, it is assumed that the sensor system is rotated around the y-axis of the coordinate system 1 by an angle θy. That is, it is assumed that the drill head is inclined from the horizontal. The sensor coordinate system after this rotation will be referred to as a coordinate system 2. Further, it is assumed that the sensor system is rotated around the x-axis of the coordinate system 2 by an angle θx, and the rotated coordinate system is referred to as a coordinate system 3. Sensor system is coordinate system 3
(The same applies to the coordinate system 2). The x-axis of the sensor coordinate system rotates about the x-axis of the sensor coordinate system. The swing of the precession may change randomly.

Next, a method for measuring the magnetic flux density in a vector manner will be described. Since the sensor system is rotated about the y-axis of the sensor coordinate system by an angle θy from a horizontal posture, a rotation matrix Ry representing this is represented by the following equation (6).

(Equation 6) Also, the gravitational acceleration vector Gw represented by the coordinate system 1 is

(Equation 7) Therefore, if this is represented by the coordinate system 2,

(Equation 8) Becomes Regarding the magnetic flux density vector B, the values expressed in the sensor coordinate system (the above-described coordinate system 2) after rotating the angle θy are referred to as the x component, the y component, and the z component of the magnetic flux density vector B. That is,

(Equation 9)

Further, an angle θx around the x-axis of the coordinate system 2
In the rotated coordinate system 3, the gravitational acceleration vector and the magnetic flux density vector are

(Equation 10) Becomes here,

[Equation 11] It is.

Next, a precession movement is incorporated. The precession motion is assumed to swing from the angle θx in the direction of the offset Δθx by an angle Δθy. The transformation matrix Rpre representing this is

(Equation 12) Becomes However,

(Equation 13) It is.

The magnetic flux density vector Bs and the acceleration vector Gs detected by the three-axis magnetic sensor TMM and the two-axis acceleration sensor DAM are affected by the precession.

[Equation 14] It is expressed as If these are expressed for each component,

(Equation 15) Becomes

Here, what needs to be actually detected by the sensor in the present invention is that the magnetic flux density components Bsx, Bsy, Bsz,
The acceleration components are Gsx and Gsz or Gsy. Although the acceleration component may detect either Gsz or Gsy,
Here, a description will be given on the assumption that the z-direction acceleration component Gsz is detected.

FIG. 2 shows the magnetic flux density components Bsx and Bs detected by the three-axis magnetic sensor TMM and the two-axis acceleration sensor DAM.
It is a figure which shows the procedure which calculates the magnetic flux density components Bx, By, and Bz shown in said Formula (9) from y, Bsz and acceleration components Gsx, Gsz. In the figure, arrows indicate the flow of information. In FIG. 2, the y-direction magnetic flux density multiplying unit MPY-BY
Is the y-direction component Bsy of the magnetic flux density and the z-direction component Gsz of the acceleration.
The z-direction magnetic flux density multiplying unit MPY-BZ calculates the product of the z-direction component Bsz of the magnetic flux density and the z-direction component Gsz of the acceleration, and the z-direction acceleration multiplying unit MPY-GZ calculates the product of the acceleration z This represents a process of taking the square of the direction component Gsz.

The x-direction magnetic flux density low-pass filter LP
FX performs low-pass filtering on the output of the x-direction magnetic sensor MMX (x-direction component Bsx of the magnetic flux density), and y-direction magnetic flux density low-pass filter LPFY applies the y-direction component Bsy of the magnetic flux density.
Low-pass filter LPFZ performs low-pass filtering on the product of the z-direction component Bsz of the magnetic flux density and the z-direction component Gsz of the acceleration. The low-pass filter ALPFX represents low-pass filtering for the output of the x-direction acceleration sensor AMX (x-direction component Gsx of acceleration), and the z-direction acceleration low-pass filter ALPZ represents low-pass filtering for the square of the output of the z-direction acceleration sensor AZ. Since these low-pass filtering processes are equivalent to averaging the measured data, averaging can be performed easily even during rotation, and the averaging is performed automatically. ing.

Further, the x-direction magnetic flux density correction unit DCX performs a correction calculation process for obtaining the x-direction component Bx of the magnetic flux density.
The y-direction magnetic flux density correction unit DCY performs a correction operation for obtaining the y-direction component By of the magnetic flux density by the z-direction magnetic flux density correction unit DC.
Z represents a correction calculation process for obtaining a z-direction component Bz of the magnetic flux density. The inclination cosine calculation unit CTA calculates the cosine or sine of the inclination angle, and the precession cosine calculation unit CPA calculates the average cosine. The process of calculating the swing angle of the differential motion and the process of calculating the tilt angle calculation unit CPT to obtain the tilt angle θy are shown.

First, the x-direction magnetic flux density low-pass filter LP
The processing contents of FX will be described. This processing is for obtaining the low frequency component <Bsx> of the x-direction component Bsx of the magnetic flux density, and the cos (θx−Δθx) and sin (θx−
Δθx), the low-frequency component <Bsx> of the x component of the magnetic flux density obtained by the operation.
Is

(Equation 16) Becomes Here, the symbol <A> represents a low-pass filter process for extracting a low-frequency component of A.

The process of the y-direction magnetic flux density low-pass filter LPFY is for obtaining a low frequency component <BsyGsz> of the product of the y-direction component Bsy of the magnetic flux density and the z-direction component Gsz of the acceleration.
The result of the processing divided by the gravitational acceleration G <BsyGsz /
G>

[Equation 17] Becomes Here, ignoring the term including Δθy ² which is small compared to the other terms,

(Equation 18) Becomes

The processing of the z-direction magnetic flux density low-pass filter LPFZ is for obtaining a low frequency component <BszGsz> of the product of the z-direction component Bsz of the magnetic flux density and the z-direction component Gsz of the acceleration.
The result of the processing divided by the gravitational acceleration G <BszGsz /
G>

[Equation 19] Becomes In this equation (27), similarly to the equation (26), the term Δθy ² is ignored because it is small.

The processing of the x-direction acceleration low-pass filter ALPFX is based on the low-frequency component <Gsx> of the x-direction component Gsx of the acceleration.
This is an operation for removing a term including sin (θx−Δθx) in the equation (22). <Gsx / G> obtained by dividing the low frequency component of the x component Gsx of the acceleration obtained by this operation by the gravitational acceleration G is

(Equation 20) Becomes

The processing of the z-direction acceleration low-pass filter ALPFZ is for obtaining the low frequency component <Gsz ² > of the square Gsz ² of the z-direction component Gsz of the acceleration, and the processing result is divided by the square of the gravitational acceleration G. The thing <(Gsz / G) ² >

(Equation 21) Becomes In equation (29), as in equation (26),
The term Δθy ² is ignored because it is small.

From this equation (29),

(Equation 22) Can be sought, and

(Equation 23) Can be requested. This processing is performed by the inclination cosine calculation unit CTA
This is the content of processing.

In the equation (28), that is, <Gsx / G>, the effect of <cosΔθy> is directly reflected as compared with the equation (29), that is, <(Gsz / G) ² >. Therefore, from the equations (31) and (28), <cosΔθ
y> can be estimated well. That is,

(Equation 24) Here, the sign may be determined so that <cosΔθy> is positive. This process is performed by the precession cosine calculation unit CPA.

Equations (26), (30) and (3)
The y-direction magnetic flux density correction unit DCY obtains the y-direction component By of the magnetic flux density from 2).

(Equation 25) Is performed. Further, the z-direction component Bz of the magnetic flux density is obtained from the above equations (27) and (30).
Directional magnetic flux density correction unit DCZ, where:

(Equation 26) Is performed. Further, the x-direction magnetic flux density correction unit DC
In X, the x-direction component Bx of the magnetic flux density is obtained from the equations (25) and (32). That is,

[Equation 27] Is performed.

Finally, the inclination angle calculation unit CPT performs the following processing:

[Equation 28] Or

(Equation 29) To calculate the inclination angle θy. In this way, the magnetic flux density components Bsx, Bsy, Bsz and the acceleration components Gsx, detected by the three-axis magnetic sensor TMM and the two-axis acceleration sensor DAM,
From Gsz, the components Bx, By, Bz of the magnetic flux density vector in the x, y, and z directions and the inclination angle θy can be obtained.
If necessary, the magnetic flux density in the coordinate system 1 where the inclination angle θy is 0 can be calculated from the result.

If the deflection angle Δθy of the precession is small, it is not necessary to correct <cosΔθy>. One embodiment of the signal processing in this case is shown in FIG. As is clear from the comparison with FIG. 2, in this embodiment, the precession cosine calculation unit CPA is omitted. In the present embodiment, the content of the processing of the y-direction magnetic flux density correction unit DCY is as follows. That is, from the equations (26) and (30),

[Equation 30] By the processing described above, the y-direction component By of the magnetic flux density is obtained. Further, the inclination angle calculation unit CPT calculates the inclination angle θy using the above equation (37).

Also, as a modification of the processing flow shown in FIG. 3, the inclination angle θy calculated by the inclination angle calculation unit CPT is calculated as <cos
θy> can be calculated and given to the x-direction magnetic flux density correction unit DCX, the y-direction magnetic flux density correction unit DCY, and the z-direction magnetic flux density correction unit DCZ. In this case, the z-direction acceleration multiplication unit MPY-GZ
And the z-direction acceleration low-pass filter ALPFZ are unnecessary,
The inclination cosine calculation unit CTA calculates <cos θy> from the inclination angle θy calculated by the inclination angle calculation unit CPT, and calculates the x-direction magnetic flux density correction unit DCX, the y-direction magnetic flux density correction unit DCY, and the z-direction magnetic flux density correction unit DCZ. Should be given.

If the deflection angle Δθy of the precession is small, the present invention can be realized using a uniaxial acceleration sensor, that is, a z-direction acceleration sensor AMZ. FIG. 4 shows an example of sensor arrangement in this embodiment. FIG. 5 shows a processing flow in this arrangement. In the present embodiment, the y-direction magnetic flux density correction unit DCY performs a process according to the equation (38). In addition, the inclination angle calculation unit CPT calculates the equation (3)
The inclination angle θy is calculated using 6). In the present embodiment, since the x-direction acceleration sensor AMX that requires a DC component is not required, accurate measurement can be performed only with a small acceleration sensor made of micromachining having a problem with offset stability. It has such an excellent feature.

In the embodiment shown in FIGS. 2 and 3, the x-direction acceleration sensor AMX needs to output a signal containing a DC component. Therefore, an embodiment in which only the AC component of the output of the x-direction acceleration sensor AMX is used to correct the precession motion using only the acceleration sensor having a large offset and its temperature drift. explain. FIG. 6 is a diagram showing an example of a processing flow in this embodiment. As is apparent from a comparison between FIG. 6 and FIG. 2, the method of this embodiment is different from the method of FIG. 2 in that an x-direction acceleration multiplication unit MPY-GX is added. I have.

In this embodiment, the x-direction acceleration sensor AM
X outputs only the AC component. x direction acceleration multiplier MPY-G
X is the AC component Gsx output from the x-direction acceleration sensor AMX.
Is performed to generate the square of (It is indicated by adding a wavy symbol (tilde) above G to indicate that it is an AC component.)

(Equation 31) It is. Therefore, the output of the x-direction acceleration multiplication unit MPY-GX is

(Equation 32) Becomes Therefore, as in the case described above, the output of the x-direction acceleration low-pass filter ALPFX is

[Equation 33] Becomes

The precession cosine calculator CPA will now

(Equation 34) By the calculation of, the average cosine of the deflection angle of the precession <cos 運動
θy> is calculated. The other processing is the same as in the case of FIG. 2 described above.

Although the embodiments of the present invention for measuring a static magnetic field have been described above, the present invention can similarly measure a static magnetic field even when the object to be measured is an AC magnetic field. However,
When measuring the AC magnetic field, when measuring the static magnetic field described above, the output of the x-direction magnetic sensor MMX, the processing result of the y-direction magnetic flux density multiplying unit MPY-BY, and the z-direction magnetic flux density multiplying unit
Instead of the x-direction magnetic flux density low-pass filter LPFX, y-direction magnetic flux density low-pass filter LPFY, and z-directional magnetic flux density low-pass filter LPFZ used to extract low frequency components from the processing results of MPY-BZ, the frequency component of the magnetic field to be measured An x-direction magnetic flux density band-pass filter BFPX, a y-direction magnetic flux density band-pass filter BFPY, and a z-direction magnetic flux density band-pass filter BFPZ, which are band-pass filters for extracting the magnetic field, are used. FIGS. 7, 8, 9, and 10 show the flow of processing when measuring an AC magnetic field by the same method as that shown in FIGS. 2, 3, 5, and 6, respectively.

When measuring the AC magnetic field, assuming that the angular frequency of the AC magnetic field is ω _B , instead of the equation (9),

(Equation 35) Must be used. At this time, the x-direction magnetic sensor MMX
The component of the frequency ω _B taken out by the x-direction magnetic flux density band-pass filter BPFX from the output (corresponding to the equation (25) when the low frequency component is taken out) is

[Equation 36] Becomes

Further, the y-direction magnetic flux density multiplying unit MPY-BY to y
Component of the frequency omega _B drawn by magnetic flux density bandpass filter BPFY (corresponding to formula (26) in the case of taking out the low frequency component),

(37) Becomes Finally, the component of the frequency ω _B extracted from the z-direction magnetic flux density multiplying unit MPY-BZ by the y-direction magnetic flux density band-pass filter BPFZ (corresponding to the above equation (27) when extracting the low frequency component) is

(38) Becomes Further, the acceleration may be processed according to the same formula as that for measuring the static magnetic field described above.

When measuring the AC magnetic field, the x-direction magnetic flux density correction unit DCX, the y-direction magnetic flux density correction unit DCY, and the z-direction magnetic flux density correction unit DCZ basically perform the same processing as that for measuring the static magnetic field. Just do it. However, when measuring the alternating magnetic field, x-direction magnetic flux density correction unit DCX, y-direction magnetic flux density correction unit DCY, because the frequency is to process the z-direction magnetic flux density correction unit DCZ is an amount of omega _B, a static magnetic field Before performing the processing performed when measuring, the operation of extracting the respective amplitudes, that is,

[Equation 39] Is performed. Also, after performing the same processing as when measuring the static magnetic field, a method of extracting the amplitude is also possible,
Extracting the amplitude in advance reduces the amount of calculation.

It should be noted that the magnetic flux density can be measured by the same method as that of the related art when the sensor system is not rotating. Further, in the above description, the magnetic field measurement for measuring the position of the drill head in the horizontal drilling method has been described as an example, but the magnetic field measurement method and apparatus of the present invention are not limited to this. It can be widely applied when measuring a magnetic field.

[0056]

As described above, according to the present invention,
Not only can accurate measurements be made using a smaller number of acceleration sensors than in the past, but also accurate measurements can be made using a small and inexpensive acceleration sensor made by micromachining. In addition, since the magnetic field is measured from the low frequency component, the data is automatically averaged even during rotation, and stable measurement is possible. Further, since the magnetic flux density can be measured while the drill head is rotating, the position of the drill head can be continuously measured without interrupting the excavation. The rotation of the drill head in the horizontal drilling method is not always smooth, and the drill head normally swings with the rotation of the drill head. According to the present invention, the present invention can be applied to the case where the rotation of the drill head is not smooth or the case where the drill head makes a swinging motion, and can reduce these effects. Further, not only a static magnetic field but also an alternating magnetic field can be measured.

[Brief description of the drawings]

FIG. 1 is a diagram showing an arrangement example of a magnetic sensor and an acceleration sensor according to an embodiment of the present invention.

FIG. 2 is a diagram schematically showing a processing flow in the embodiment of the present invention.

FIG. 3 is a diagram schematically showing a flow of processing in the embodiment when the deflection angle of the precession is small.

FIG. 4 is a diagram showing an example of sensor arrangement in an embodiment using a one-axis acceleration sensor.

FIG. 5 is a diagram showing an example of a flow of signal processing in the embodiment when a one-axis acceleration sensor is used.

FIG. 6 is a diagram showing a flow of signal processing in an embodiment using only an AC component of the acceleration sensor.

FIG. 7 is a diagram showing a flow of signal processing in an embodiment for measuring an AC magnetic field using a two-axis acceleration sensor.

FIG. 8 is a diagram showing a flow of signal processing in another embodiment for measuring an AC magnetic field using a two-axis acceleration sensor.

FIG. 9 is a diagram showing a flow of signal processing in an embodiment for measuring an AC magnetic field using a one-axis acceleration sensor.

FIG. 10 is a diagram showing a flow of signal processing in an embodiment in which an AC magnetic field is measured using only an AC component of a two-axis acceleration sensor.

FIG. 11 is a diagram showing an arrangement of sensors in a conventional measuring method.

FIG. 12 is a diagram showing a flow of processing in a conventional measurement method.

[Explanation of symbols]

 ALPFX x-direction acceleration low-pass filter ALPFZ z-direction acceleration low-pass filter AMX x-direction acceleration sensor AMY y-direction acceleration sensor AMZ z-direction acceleration sensor BFPX x-direction magnetic flux density bandpass filter BFPY y-direction magnetic flux density bandpass filter BFPZ z-direction magnetic flux density bandpass Filter CPA Precession cosine calculation unit CPT Inclination angle calculation unit DAM 2-axis acceleration sensor DCX x-direction magnetic flux density correction unit DCY y-direction magnetic flux density correction unit DCZ z-direction magnetic flux density correction unit CTA tilt cosine calculation unit LPFX x-direction magnetic flux density low-pass filter LPFY y-direction magnetic flux density low-pass filter LPFZ z-direction magnetic flux density low-pass filter MMX x-direction magnetic sensor MMY y-direction magnetic sensor MMZ z-direction magnetic sensor MPY-BY y-direction magnetic flux density multiplying unit MPY-BZ z-directional magnetic flux density multiplying unit MPY-GX x-direction acceleration multiplier MPY-GZ z-direction acceleration multiplier TAM 3-axis acceleration sensor TMM 3-axis magnetic sensor Support

Claims (16)

[Claims] A three-axis magnetic sensor having three magnetic sensors each having a sensitivity axis in three directions orthogonal to each other;
A two-axis acceleration sensor having two acceleration sensors each having a sensitivity axis in two directions orthogonal to each other, such that the sensitivity axis of the two-axis acceleration sensor is parallel to the two sensitivity axes of the three-axis magnetic sensor. The three-axis magnetic sensor and the two-axis acceleration sensor are simultaneously rotated while maintaining the mutual attitude, with the sensitivity axis of the first acceleration sensor of the two acceleration sensors as the rotation axis. A magnetic field measuring method for measuring a static magnetic field using measuring means adapted to be capable of causing a magnetic sensor having a sensitivity axis in a rotation axis direction to be a first magnetic sensor; When the magnetic sensor whose sensitivity axis is orthogonal to the sensitivity axis of the second acceleration sensor is the second magnetic sensor and the remaining magnetic sensors are the third magnetic sensor, the low frequency of the output of the first magnetic sensor is low. Calculating the magnetic field in the rotation axis direction from several components; and calculating a low frequency component of a product 1, which is a product of an output of the second acceleration sensor and an output of the second magnetic sensor, and an output of the second acceleration sensor. From the low frequency component of the product 2, which is the product of the output of the third magnetic sensor, a magnetic field in a second direction perpendicular to the rotation axis and included in a plane extending perpendicularly to the rotation axis and the rotation axis A magnetic field measuring method comprising calculating a magnetic field in a third direction orthogonal to the second direction. 2. A square obtained by dividing an AC component of an output of the second acceleration sensor by a gravitational acceleration to obtain a square root of 2 times a square root of a low-frequency component thereof. The magnetic field in the third direction is calculated from the low frequency component divided by the cosine 1, and the magnetic field in the second direction is calculated from the low frequency component of the product 2 divided by the cosine 1. 2. The magnetic field measuring method according to claim 1, wherein: 3. A square obtained by dividing an AC component of the output of the second acceleration sensor by a gravitational acceleration, and taking a square root of 2 times a square root of a low frequency component thereof as a cosine 1, and the cosine 1 is a cosine. When an angle 1 to be calculated is calculated, and a low frequency component obtained by dividing an AC component of an output of the first acceleration sensor by a gravitational acceleration and a sine of the angle 1 is obtained as a cosine 2, the first magnetism is obtained. The magnetic field in the direction of the rotation axis is calculated from the low frequency component of the output of the sensor divided by the cosine 2, and the third frequency is calculated from the low frequency component of the product 1 divided by the cosine 1 and the cosine 2. The magnetic field measurement method according to claim 1, wherein a magnetic field in a direction is calculated, and a magnetic field in the second direction is calculated from a value obtained by dividing a low-frequency component of the product 2 by the cosine 1. 4. The first acceleration sensor, wherein the AC component of the output of the second acceleration sensor divided by the gravitational acceleration is squared, and the square root times two of the square root of the low frequency component is set as cosine 1. The square root of the low frequency component of the square of the output AC component divided by the gravitational acceleration divided by the square of cosine 1 is sine 2, and the square root of the square of the sine 2 subtracted from 1 is the cosine. 2, the magnetic field in the rotation axis direction is calculated from the value obtained by dividing the low frequency component of the output of the first magnetic sensor by the cosine 2, and the low frequency component of the product 1 is calculated by the cosine 1 and the cosine 2. The magnetic field in the third direction is calculated from the divided value, and the magnetic field in the third direction is calculated from the value obtained by dividing the low frequency component of the product 2 by the cosine 1. 2. The magnetic field measurement method according to 1. 5. A three-axis magnetic sensor having three magnetic sensors each having a sensitivity axis in three directions orthogonal to each other,
One acceleration sensor spatially disposed so that a sensitivity axis is parallel to one of the three magnetic sensors; and an acceleration sensor of the three-axis magnetic sensor. Any one of two sensitivity axes orthogonal to the sensitivity axis
A magnetic field measuring method for measuring a static magnetic field by using a measuring means adapted to be able to simultaneously rotate the three-axis magnetic sensor and the acceleration sensor while maintaining a mutual attitude while using an axis parallel to the rotation axis as a rotation axis. Wherein a magnetic sensor having a sensitivity axis in the direction of the rotation axis is a first magnetic sensor, and among the remaining magnetic sensors, a magnetic sensor whose sensitivity axis is orthogonal to the acceleration sensor is a second magnetic sensor. When the third magnetic sensor is used as the third magnetic sensor, the magnetic field in the rotation axis direction is calculated from the low frequency component of the output of the first magnetic sensor, and the output of the acceleration sensor and the output of the third magnetic sensor are calculated. From the low frequency component of the product of the product of the above and the low frequency component of the product of the output of the acceleration sensor and the output of the second magnetic sensor, it is included in a plane extending vertically to the rotation axis and is orthogonal to the rotation axis. 2 in the direction of the magnetic field and the rotating shaft and the second
A magnetic field in a third direction orthogonal to the direction of (i). 6. A three-axis magnetic sensor having three magnetic sensors each having a sensitivity axis in three directions orthogonal to each other,
A two-axis acceleration sensor having two acceleration sensors each having a sensitivity axis in two directions orthogonal to each other, such that the sensitivity axis of the two-axis acceleration sensor is parallel to the two sensitivity axes of the three-axis magnetic sensor. The three-axis magnetic sensor and the two-axis acceleration sensor are simultaneously rotated while maintaining the mutual attitude, with the sensitivity axis of the first acceleration sensor of the two acceleration sensors as the rotation axis. A magnetic field measuring method for measuring an alternating magnetic field of a predetermined frequency using a measuring means adapted to be capable of causing a magnetic field having a sensitivity axis in a rotation axis direction as a first magnetic sensor, When the magnetic sensor whose sensitivity axis is orthogonal to the sensitivity axis of the second acceleration sensor is the second magnetic sensor and the remaining magnetic sensors are the third magnetic sensor, the first magnetic sensor Calculating the magnetic field in the direction of the rotation axis from the component of the output of the predetermined frequency in the direction of the rotation axis; and calculating the product of the predetermined frequency of the product 1 which is the product of the output of the second acceleration sensor and the output of the second magnetic sensor. From the component of the predetermined frequency of the product 2, which is the product of the component, the output of the second acceleration sensor, and the output of the third magnetic sensor, is included in a plane extending in the vertical direction with respect to the rotation axis. A magnetic field measurement method comprising: calculating a magnetic field in a second direction orthogonal to the first direction and a magnetic field in a third direction orthogonal to the rotation axis and the second direction. 7. A square obtained by dividing an AC component of an output of the second acceleration sensor by a gravitational acceleration to obtain a square root of a square root of 2 of a square root of the component of the predetermined frequency. The magnetic field in the third direction is calculated from the component obtained by dividing the component of the predetermined frequency of the product 1 by the cosine 1, and the magnetic field obtained by dividing the component of the predetermined frequency of the product 2 by the cosine 1. 7. The magnetic field measuring method according to claim 6, wherein the magnetic field in the second direction is calculated. 8. A square obtained by dividing an AC component of an output of the second acceleration sensor by a gravitational acceleration, and taking a square root of two times a square root of a component of the predetermined frequency as a cosine 1, When the cosine 2 is obtained by calculating the angle 1 with cosine as the cosine and dividing the AC component of the output of the first acceleration sensor by the gravitational acceleration, but dividing the component of the predetermined frequency by the sine of the angle 1 Calculating a magnetic field in the direction of the rotation axis from a value obtained by dividing the component of the output of the first magnetic sensor at the predetermined frequency by the cosine 2, and calculating the predetermined frequency component of the product 1 by the cosine 1 and Calculating the magnetic field in the third direction from the result of division by cosine 2 and calculating the magnetic field in the second direction from the result of dividing the component of the product 2 at the predetermined frequency by the cosine 1 7. The magnetic field measuring method according to claim 6, wherein: . 9. A square obtained by dividing an AC component of an output of the second acceleration sensor by a gravitational acceleration, and taking a square root of 2 times a square root of a component of the predetermined frequency as a cosine 1, A square root of a component obtained by dividing the AC component of the output of the acceleration sensor by the gravitational acceleration and dividing the component of the predetermined frequency by the square of the cosine 1 is defined as a sine 2.
When the square root of a value obtained by subtracting the square of? From 1 is cosine 2, a magnetic field in the rotation axis direction is calculated from a value obtained by dividing the component of the predetermined frequency of the output of the first magnetic sensor by the cosine 2, A magnetic field in the third direction is calculated from the product of the predetermined frequency component of the product 1 divided by the cosine 1 and the cosine 2, and the predetermined frequency component of the product 2 is divided by the cosine 1. 7. The magnetic field measuring method according to claim 6, wherein the magnetic field in the third direction is calculated from the result. 10. A three-axis magnetic sensor having three magnetic sensors each having a sensitivity axis in three directions orthogonal to each other, and the sensitivity axis is parallel to one of the three magnetic sensors. Having one acceleration sensor spatially arranged as described above, and an axis parallel to any one of two sensitivity axes orthogonal to the sensitivity axis of the acceleration sensor among the three-axis magnetic sensors Is a rotation axis, and a magnetic field measuring method for measuring an AC magnetic field of a predetermined frequency by using a measuring unit configured to be able to simultaneously rotate the three-axis magnetic sensor and the acceleration sensor while maintaining a mutual posture. A magnetic sensor having a sensitivity axis in the direction of the rotation axis is defined as a first magnetic sensor, and a magnetic sensor having a sensitivity axis orthogonal to the acceleration sensor is defined as a second magnetic sensor. Magnetic When the sensor is a third magnetic sensor, the magnetic field in the rotation axis direction is calculated from the component of the predetermined frequency in the output of the first magnetic sensor, and the output of the acceleration sensor and the third magnetic field are calculated. From the component of the predetermined frequency of the product of the product of the sensor output and the product of the output of the acceleration sensor and the output of the second magnetic sensor, A magnetic field measurement method comprising calculating a magnetic field in a second direction orthogonal to the rotation axis and a magnetic field in a third direction orthogonal to the rotation axis and the second direction. 11. The apparatus according to claim 1, wherein said measuring means is stored in a storage part provided at or near the excavation means of the horizontal drilling method, and measures a magnetic field near the storage part. The magnetic field measurement method according to any one of the above. 12. The apparatus according to claim 1, wherein said measuring means is stored in a drilling means of a horizontal drilling method or a storage part provided in the vicinity thereof, and said rotation is given by rotation of a drill pipe. 11. The method for measuring a magnetic field according to any one of 10). 13. A magnetic field measuring apparatus for measuring a static magnetic field, comprising: a three-axis magnetic sensor having three magnetic sensors each having a sensitivity axis in three directions orthogonal to each other; and a sensitivity axis in two directions orthogonal to each other. A two-axis acceleration sensor having two acceleration sensors having the following two spatially arranged so that the sensitivity axis of the two-axis acceleration sensor and the two sensitivity axes of the three-axis magnetic sensor are parallel to each other; The sensitivity axis of the first acceleration sensor among the plurality of acceleration sensors as the rotation axis,
A measuring unit configured to be able to simultaneously rotate the axial magnetic sensor and the two-axis acceleration sensor while maintaining a mutual posture; and a magnetic sensor having a sensitivity axis in the rotational axis direction as a first magnetic sensor; When the magnetic sensor whose sensitivity axis is orthogonal to the sensitivity axis of the second acceleration sensor is the second magnetic sensor and the remaining magnetic sensors are the third magnetic sensor, the first magnetic sensor Means for calculating the magnetic field in the direction of the rotational axis from the low frequency component of the output of the second sensor; and the low frequency component of the product 1, which is the product of the output of the second acceleration sensor and the output of the second magnetic sensor, From the low frequency component of the product 2, which is the product of the output of the acceleration sensor and the output of the third magnetic sensor, a magnetic field in a second direction which is included in a plane extending perpendicularly to the rotation axis and perpendicular to the rotation axis. And before Magnetic field measuring apparatus characterized by having means for calculating a magnetic field in a third direction perpendicular to the rotational axis and the second direction. 14. A magnetic field measuring apparatus for measuring a static magnetic field, comprising: a three-axis magnetic sensor having three magnetic sensors each having a sensitivity axis in three directions orthogonal to each other;
One acceleration sensor spatially disposed so as to be parallel to one sensitivity axis of the three magnetic sensors, and orthogonal to a sensitivity axis of the acceleration sensor of the three-axis magnetic sensors. Measuring means configured to be able to rotate the three-axis magnetic sensor and the acceleration sensor at the same time while maintaining a mutual attitude, with a rotation axis being an axis parallel to any one of the two sensitivity axes. And a magnetic sensor having a sensitivity axis in the rotation axis direction as a first magnetic sensor, and among the remaining magnetic sensors, a magnetic sensor having a sensitivity axis orthogonal to the acceleration sensor as a second magnetic sensor; When the sensor is a third magnetic sensor, means for calculating the magnetic field in the rotation axis direction from a low frequency component of the output of the first magnetic sensor; output of the acceleration sensor and output of the third magnetic sensor When From the low frequency component of the product of the low frequency component of the product, the output of the acceleration sensor, and the output of the second magnetic sensor, a second component that is included in a plane extending vertically to the rotation axis and that is orthogonal to the rotation axis Magnetic field and the axis of rotation and the second
Means for calculating a magnetic field in a third direction orthogonal to the direction of the magnetic field. 15. A magnetic field measuring apparatus for measuring an alternating magnetic field of a predetermined frequency, comprising: a three-axis magnetic sensor having three magnetic sensors each having a sensitivity axis in three directions orthogonal to each other; A two-axis acceleration sensor having two acceleration sensors each having a sensitivity axis is spatially arranged such that the sensitivity axis of the two-axis acceleration sensor and the two sensitivity axes of the three-axis magnetic sensor are parallel to each other. And a sensitivity axis of a first acceleration sensor of the two acceleration sensors as a rotation axis;
A measuring unit configured to be able to simultaneously rotate the axial magnetic sensor and the two-axis acceleration sensor while maintaining a mutual posture; and a magnetic sensor having a sensitivity axis in the rotational axis direction as a first magnetic sensor; When the magnetic sensor whose sensitivity axis is orthogonal to the sensitivity axis of the second acceleration sensor is the second magnetic sensor and the remaining magnetic sensors are the third magnetic sensor, the first magnetic sensor Means for calculating a magnetic field in the direction of the rotation axis from a component of the predetermined frequency of the output of the second frequency sensor; and the predetermined frequency of a product 1, which is a product of an output of the second acceleration sensor and an output of the second magnetic sensor. From the component of the predetermined frequency of the product 2, which is the product of the output of the second acceleration sensor and the output of the third magnetic sensor, the rotation axis included in a plane extending in the vertical direction with the rotation axis. Directly Magnetic field measuring apparatus characterized by having means for calculating a third magnetic field in the direction of the perpendicular to the second magnetic field and the rotating shaft and the second direction in a direction. 16. A magnetic field measuring apparatus for measuring an AC magnetic field having a predetermined frequency, comprising: a three-axis magnetic sensor having three magnetic sensors each having a sensitivity axis in three directions orthogonal to each other;
One acceleration sensor spatially disposed so as to be parallel to one sensitivity axis of the three magnetic sensors, and orthogonal to a sensitivity axis of the acceleration sensor of the three-axis magnetic sensors. Measuring means configured to be able to rotate the three-axis magnetic sensor and the acceleration sensor at the same time while maintaining a mutual attitude, with a rotation axis being an axis parallel to any one of the two sensitivity axes. And a magnetic sensor having a sensitivity axis in the rotation axis direction as a first magnetic sensor, and among the remaining magnetic sensors, a magnetic sensor having a sensitivity axis orthogonal to the acceleration sensor as a second magnetic sensor; When the sensor is a third magnetic sensor, means for calculating a magnetic field in the direction of the rotation axis from a component of the predetermined frequency of an output of the first magnetic sensor; and an output of the acceleration sensor and the third magnetic field. Sen From the component of the predetermined frequency of the product of the product of the predetermined frequency and the product of the output of the acceleration sensor and the output of the second magnetic sensor, a component of the product of the predetermined frequency is included in a plane extending in the vertical direction with the rotation axis. Means for calculating a magnetic field in a second direction orthogonal to the rotation axis and a magnetic field in a third direction orthogonal to the rotation axis and the second direction.