JPH08201060A - Geomagnetic azimuth meter - Google Patents

Abstract

PURPOSE: To enhance accuracy and reliability in the measurement by detecting the geomagnetic azimuth angle in one arbitrary direction based on the phase angle of a rotating field where the strength of combined field of rotating field and geomagnetic field, detected by means of a field strength sensor, has a maximal or minimal absolute value. CONSTITUTION: X-axis coils 3, 4 and Y-axis coils 1, 2 are arranged symmetricaliy to YZ and XZ planes, respectively, while aligning the central axes with the X-axis and Y-axis. The coils 3, 4 and 1, 2 are connected, respectively, in series and fed with AC currents IX=cosϕ and IY=sinϕ from AC current sources 10, 9 to induce fields HX, HY proportional to the currents IX, IY in the directions of X-axis and Y-axis. Output from a field strength sensor 5 is then fed to a maximal value (minimal value) detector and the phase angle ϕof rotating field having maximal value (minimal value), the waveform of the current IX, IY or the instantaneous level of the current is detected by a level detector. Finally, the detection level is subjected to inverse cosine or sine transform thus detecting the azimuth angle ϕ (ϕ-180 deg.) of geomagnetism.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a geomagnetic compass.

[0002]

2. Description of the Related Art A conventional geomagnetic compass will be described with reference to FIG. Reference numeral 15 denotes a geomagnetic direction sensor, which is composed of a pair of sensors that detect geomagnetism in a certain direction and a direction different from this by 90 °. H _E represents the horizontal component force of the earth's magnetism, assuming an XY orthogonal coordinate system in the horizontal plane (paper surface), and a certain direction is the Y-axis direction and a direction different from it by 90 ° is the X-axis direction. Thus, the azimuth angle of the geomagnetism is θ with respect to the Y-axis direction.
If the angle is °, two outputs of the detected output voltage, cos θ and sin θ, are obtained from the geomagnetic direction sensor 15.
After being supplied to the D converters 16 and 17 and converted into a digital voltage, it is supplied to the computer 18,

[0003]

[Equation 1]

Azimuth angle θ
Is detected.

[0005]

The conventional geomagnetic compass as described above has the following drawbacks. Geomagnetic direction sensor 15
If the characteristics of a pair of sensors that detect the earth's magnetism in a certain direction and a direction different from this by 90 ° are not uniform, the detection output voltage of the pair of sensors is generally A ₁ sin θ + B ₁ ,
Assuming A ₂ cos θ + B ₂ , these coefficients A ₁ , A ₂ , B
_{Between 1} and B ₂ , A ₁ ≠ A ₂ or B ₁ due to noise generation in the processing circuit, temperature drift, etc.
Since ≠ B ₂ or A ₁ ≠ A ₂ and B ₁ ≠ B ₂ , the geomagnetic azimuth cannot be accurately measured. An A / D converter and a computer are required to perform the calculation of the above-described mathematical expression 1, the configuration of the geomagnetic compass is complicated, and the price is increased. When the characteristics of the pair of sensors of the geomagnetic direction sensor 15 are not uniform as described above, the coefficient A
_Since correction means for A ₁ = A ₂ and / or B ₁ = B ₂ between ₁ , A ₂ , B ₁ , and B ₂ is required,
The structure of the geomagnetic compass will become more complicated, leading to higher prices. In order to further improve the detection accuracy of the geomagnetic direction, it is necessary to dynamically correct the detection output voltage from the pair of sensors of the geomagnetic direction sensor 15, but in that case, more complicated and expensive correction means is required, Furthermore, the structure of the geomagnetic compass becomes more complicated, leading to an increase in price.

In view of the above point, the present invention intends to propose a geomagnetic compass with a simple structure, high measurement accuracy and high reliability without being affected by noise and temperature drift in the processing circuit. It is a thing.

[0007]

The present invention has a rotating magnetic field generating means and a magnetic field strength sensor arranged at the center of the rotating magnetic field generating means for detecting magnetic field strength in any one direction.
The magnetic field strength sensor detects the magnetic field strength of the combined magnetic field of the rotating magnetic field and the geomagnetism by the rotating magnetic field generating means, and the rotating magnetic field when the absolute value of the detected magnetic field strength of the combined magnetic field reaches the maximum value or the minimum value. Any 1 from the phase angle of
A geomagnetic azimuth meter characterized by detecting a geomagnetic azimuth angle with respect to a direction.

[0008]

According to the present invention, the magnetic field strength sensor detects the magnetic field strength of the combined magnetic field of the rotating magnetic field and the earth magnetism by the rotating magnetic field generation means, and the absolute value of the detected magnetic field strength of the combined magnetic field is the maximum value or The geomagnetic azimuth angle with respect to any one direction is detected from the phase angle of the rotating magnetic field when it reaches the minimum value.

[0009]

Embodiments of the present invention will be described in detail below with reference to FIG. Assume an orthogonal coordinate system having X and Y axes in the plane of the paper and Z axis in the direction perpendicular to the plane of the paper. And
Cylindrical, square tubular, etc. X-axis coils 3 and 4 which are arranged plane-symmetrically with respect to the YZ plane and whose central axis coincides with the X-axis, and are arranged symmetrically with respect to the XZ plane, and whose central axis is the Y-axis. The corresponding Y-axis coils 1 and 2 having a cylindrical shape, a square cylindrical shape, or the like are provided. Then, in the projected image on the XY plane, the coils 1, 2,
3, 4 are arranged so as to substantially form each side of the square.

Then, the X-axis coils 3 and 4 are connected in series, an AC current source 10 is connected to the series circuit, an AC current I _X = sinφ is passed, and an X proportional to the AC current I _X is applied.
Generating a uniform magnetic field H _X in the axial direction. Further, the Y-axis coils 1 and 2 are connected in series, an AC current source 9 is connected to the series circuit, an AC current I _Y = cos φ is passed, and it is uniform in the Y-axis direction proportional to the DC current I _Y. A strong magnetic field H _Y. H _rotate indicates a composite magnetic field (rotating magnetic field) of the magnetic fields H _X and H _Y. 6, 7 and 8 are the magnetic fields H _X and H _Y , respectively.
The vector of the combined magnetic field H _rotate of and is shown. Thus, the magnetic fields H _X and H _Y are respectively expressed by the following equations.

[0011]

[Equation 2]

[0012]

(Equation 3)

Magnetic field H at the origin of the XYZ rectangular coordinate system
_{The rotate} is a vector combination of the magnetic fields H _X and H _{Y, and} is expressed by the following equation.

[0014]

[Equation 4]

This magnetic field H _rotate is a function of H _X and H _Y , and the magnetic field strength is constant and the phase angle is 0 ° to 360 °.
It is a rotating magnetic field that continuously changes in the range of °.

Consider the influence of the horizontal component force of the earth's magnetism by matching the XY plane of the XYZ orthogonal coordinate system in FIG. 3 with the horizontal plane. That is, as shown in FIG. 2, the horizontal component force of geomagnetism is indicated by H _E in the XY plane. 12 indicates the vector of the magnetic field H _E. When the horizontal component force H _E of this geomagnetism is vector- _divided into horizontal and vertical components H _EX and H _EY , it is expressed by the following equation.

[0017]

(Equation 5)

[0018]

(Equation 6)

Thus, X at the origin of the XYZ rectangular coordinates
The magnetic field H in the Y plane is a vector combination of the rotating magnetic field H _rotate and the horizontal component H _E of the earth's magnetism.
It is expressed as shown in the following equation.

[0020]

(Equation 7)

The composite magnetic field H rotates in the same direction as the rotating magnetic field H _rotate rotates. The absolute value of the intensity of this synthetic magnetic field H is expressed by the following equation.

[0022]

(Equation 8)

The azimuth angle of the horizontal component force of the geomagnetism with respect to the + X axis direction of the geomagnetism H _E is θ, and the phase angle φ of the rotating magnetic field H _rotate is the angle from the + X axis. X-axis coils 3, 4 and Y
Currents IX and IY flowing through the shaft coils 1 and 2 are as shown in FIG.
As shown in (a) and (b), the waveforms exhibit different phases by 90 °. FIG. 1C shows the phase angle φ of the rotating magnetic field H _rotate.
The phase angle φ changes in the range of 0 ° to 360 °. FIG. 1D shows the characteristic of the absolute value | H | of the synthetic magnetic field H.

From the graph of FIG. 1D, the combined magnetic field strength | H | has a maximum value when φ = θ, and a minimum value when φ = θ + 180 °. I understand. Therefore, it can be seen that the phase angles φ when the combined magnetic field strength | H | has the maximum value and the minimum value, respectively, are the azimuth angles θ and θ-180 ° of the geomagnetism.

The output from the magnetic field strength sensor 5 is
For example, supplying the maximum value detector (or the minimum value detector),
When the maximum value (or minimum value) is detected, the phase angle φ at that time is checked by looking at the waveform of the X-axis coil current IX or the Y-axis coil current IY, or the instantaneous level of the current is detected by a level detector. Then, the azimuth angle of the geomagnetism θ
(Or θ-180 °) can be detected.

Next, the ratio H _rotate / H _E of the rotating magnetic field H _rotate and the geomagnetism H _E is set to η, and when η = 0.5, 1, 2 the combined magnetic field strength | H for changes in the phase angle φ A graph around the minimum value of | is shown in FIG. According to this, η = 1
At that time, the combined magnetic field strength | H | becomes 0, and the characteristics near 0 become steep. When η = 0.5 and 2,
The minimum value becomes larger than 0, and the characteristic near the minimum value becomes slow. Therefore, the strength of the rotating magnetic field H _rotate is
_It is set to be equal to the strength of the horizontal component force of _E , and the magnetic field strength detection output from the magnetic field strength sensor 5 is supplied to, for example, a level detector so that the level becomes 0. Can be detected. Then, when it is detected that the level becomes 0, the phase angle φ at that time is set to the X-axis coil current IX or the Y-axis coil current IY.
Or the instantaneous level of the current is detected by a level detector, and the detected level is subjected to cosine inverse conversion or sine inverse conversion to determine the angle (θ-180 °) with respect to the azimuth θ of the geomagnetism. Can be detected.

[0027]

According to the present invention described above, it has a rotating magnetic field generating means and a magnetic field strength sensor arranged at the center of the rotating magnetic field generating means for detecting the magnetic field strength in any one direction.
The magnetic field strength sensor detects the magnetic field strength of the combined magnetic field of the rotating magnetic field and the geomagnetism by the rotating magnetic field generation means, and the phase of the rotating magnetic field when the absolute value of the detected magnetic field strength of the combined magnetic field is the maximum value or the minimum value. Since the geomagnetic azimuth angle with respect to any one direction is detected from the angle, the configuration is simple, and the measurement accuracy is high and the geomagnetism is highly reliable without being affected by noise or temperature drift in the processing circuit. You can get a compass.

[Brief description of drawings]

FIG. 1 is a timing chart used for explaining the operation of an embodiment. (A) X-axis coil current (b) Y-axis coil current (c) Rotating magnetic field phase angle (d) Composite magnetic field strength

FIG. 2 is an explanatory diagram of a magnetic field.

FIG. 3 is a circuit diagram showing a geomagnetic compass according to an embodiment of the present invention.

FIG. 4 is a characteristic curve diagram of the strength of a synthetic magnetic field.

FIG. 5 is a block diagram showing a conventional geomagnetic compass.

[Explanation of symbols]

 1 to 4 rotating magnetic field generating coil 5 magnetic field intensity sensor 9 exciting current source 10 exciting current source

Claims (1)

[Claims] 1. A rotating magnetic field generating means, and a magnetic field strength sensor arranged at the center of the rotating magnetic field generating means for detecting magnetic field strength in any one direction. Detects the magnetic field strength of the combined magnetic field of rotating magnetic field and geomagnetism by means,
The geomagnetic azimuth angle with respect to the arbitrary one direction is detected from the phase angle of the rotating magnetic field when the absolute value of the detected magnetic field strength of the synthesized magnetic field has a maximum value or a minimum value. A geomagnetic compass.