JP2003065791A - Azimuth angle measuring device and azimuth angle measuring method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure an azimuth based on terrestrial magnetism detected using a Hall element. SOLUTION: The reference values Lx, Ly of an x-axis Hall element HEx and a y-axis Hall element HEy are stored in the memory 7 of a correction value, and a correction calculator 6 corrects the output amplifying values Dx, Dy of the x-axis Hall element HEx and the y-axis Hall element HEy and then fetches only values α, βproportional to each axis component of the terrestrial magnetism using these reference values Lx, Ly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an azimuth angle measuring device and an azimuth angle measuring method, and is particularly suitable for application in the case of detecting an azimuth by detecting geomagnetism.

[0002]

2. Description of the Related Art In recent years, with the spread of mobile phones and PDAs, the needs for navigation systems for pedestrians have increased, and the demand for direction sensor systems for measuring the pedestrian's current position as well as the direction of travel has increased. . As a conventional method for measuring the traveling direction of a pedestrian, there has been a method of detecting the terrestrial magnetism by a highly sensitive fluxgate sensor to obtain the azimuth.

[0003]

However, in the fluxgate sensor, since the core material and the winding are used,
The size of the device becomes large and the price becomes expensive. Furthermore, if there is a speaker or other nearby magnet that produces magnetism in the mobile phone, the magnet will saturate the core material, and the measurement of geomagnetism will be possible. Since it cannot be used, it was not suitable for use in a pedestrian navigation system or the like.

Therefore, an object of the present invention is to use a magnetic sensor having a low sensitivity or even when the magnetic sensor is mounted in a mobile device having an object which generates a magnetic field larger than the earth's magnetic field nearby.
An azimuth measuring device and an azimuth measuring method capable of measuring the azimuth from the earth's magnetism.

[0005]

In order to solve the above-mentioned problems, the azimuth measuring device according to claim 1 is an azimuth measuring device mounted in a mobile device for detecting geomagnetism. A magnetic sensor having two or more axes, a first correction value storage unit that stores reference values for each axis output of the magnetic sensor, and a first correction calculation unit that subtracts the reference value from an output amplification value of the magnetic sensor. And an azimuth angle calculation unit that calculates the azimuth in which the mobile device is heading, based on the output correction value by the first correction calculation unit.

According to another aspect of the azimuth measuring device of the present invention, the azimuth measuring device is mounted in a mobile device, wherein each of the magnetic sensors has three or more axes for detecting geomagnetism. A first correction value storage unit that stores a reference value for the axis output, a first correction calculation unit that subtracts the reference value from the output amplification value of the magnetic sensor, a two-axis tilt sensor, and the tilt A three-axis magnetic sensor output correction value by the first correction calculation unit is provided, including a tilt angle calculation unit that calculates a tilt angle at which the mobile device is tilted with respect to a horizontal plane based on output values of each axis of the sensor. And the above 2
An azimuth angle calculation unit that calculates an azimuth in which the mobile device is heading based on a calculated value of the tilt angle of the axis is provided.

According to another aspect of the azimuth measuring device of the present invention, the azimuth measuring device is mounted in a mobile device, and the magnetic sensor has three or more axes for detecting geomagnetism, and each of the magnetic sensors. A first correction value storage unit that stores a reference value for the shaft output, a first correction calculation unit that subtracts the reference value from the output amplification value of the magnetic sensor, and an inclination angle setting unit that sets an inclination angle, An azimuth angle calculation unit that calculates the azimuth of a horizontal plane on which the mobile device is heading, based on the output values of the magnetic sensor outputs of three or more axes corrected by the first correction calculation unit and the tilt angle set by the tilt angle setting unit. It is characterized by including.

Further, according to the azimuth angle measuring device of the fourth aspect, the first correction value storage unit stores a plurality of reference values corresponding to a usage state of the mobile device, and the first correction value storage unit stores the plurality of reference values. The calculation unit is characterized by selecting a reference value corresponding to the usage state of the mobile device and performing the subtraction. In addition, claim 5
According to the azimuth measuring device described in the above, the azimuth measuring device is mounted in a mobile device, and further includes a second correction value storage unit that stores a sensitivity ratio of the magnetic sensors of two or more axes, It is characterized by further comprising a second correction calculation unit that multiplies the output value of the magnetic sensor by the sensitivity ratio.

According to another aspect of the azimuth measuring device of the present invention, the azimuth measuring device is installed in a mobile device, and the reference value is subtracted from the output amplified values of the magnetic sensors of two or more axes. An integrated averaging unit that integrates and averages the output correction values is provided. Further, according to the azimuth measuring device of the seventh aspect, at least one of the magnetic sensors is a Hall element.

Further, according to the azimuth measuring device of the present invention, a chopper part for switching the connection between the input terminal of the power source for driving the hall element and the voltage output terminal of the hall element is provided, and the chopper part is provided. Is used to offset most of the offset included in the output of the Hall element, and then the third correction calculation unit that subtracts the reference value is provided.

Further, according to the azimuth measuring method of the ninth aspect, from the respective axis outputs of the magnetic sensors of two or more axes which detect the geomagnetism, which are installed in the mobile equipment, the respective axes stored in advance are stored. The azimuth in which the mobile device is heading is calculated based on the correction value obtained by subtracting the reference value.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An azimuth measuring device and an azimuth measuring method according to embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of an azimuth angle measuring device according to a first embodiment of the present invention.

In FIG. 1, a biaxial magnetic sensor 1, a chopper section 2, a magnetic sensor drive power source section 3, a differential input amplifier 4,
An A / D conversion unit 5, a correction calculation unit 6, a correction value storage unit 7, and an azimuth angle calculation unit 8 are provided, and the biaxial magnetic sensor 1 has x
An axial Hall element HEx and a y-axis Hall element HEy are provided. Here, the x-axis Hall element HEx and the y-axis Hall element HEy are for detecting geomagnetism, and are preferably compound semiconductors such as InSb, InAs, and GaAs.

The chopper section 2 is for switching the terminals for driving the x-axis Hall element HEx and the y-axis Hall element HEy, and the drive voltage output from the magnetic sensor drive power source section 3 is applied to the x-axis Hall element HEx and the y-axis. Hall element H
Apply to Ey. Here, the chopper unit 2 is, for example, 9
A 0 ° chopper drive or a 360 ° chopper drive can be used. In the 90 ° chopper drive, when driving the x-axis hall element HEx and the y-axis hall element HEy, the x-axis hall element HEx and the y-axis hall element HEy are driven.
Most of the offset term of the Hall element itself included in the output of y can be canceled.

Further, in the 360 ° chopper drive, not only the offset term of the Hall element itself included in the outputs of the x-axis Hall element HEx and the y-axis Hall element HEy but also the electrical offset term of the amplifier itself in the subsequent stage is canceled. be able to. FIG. 2 is a diagram showing a 360 ° chopper driving method and output signals of the chopper unit 2 according to the embodiment of the present invention.

In FIG. 2, the x-axis Hall element HEx and the y-axis Hall element HEy are provided with four terminals T1 to T4. Then, in the 360 ° chopper driving method, the x-axis Hall element HEx and the y-axis Hall element HEy are driven while switching the input terminal and the output terminal for every four phases. Here, when the phase is 0 °, x
The terminals T1 and T3 of the axial Hall element HEx and the y-axis Hall element HEy are used as input terminals, and the terminal T3 is LOW.
The terminal T1 is set to the high level while being set to the level. Then, by using the terminals T2 and T4 of the x-axis Hall element HEx and the y-axis Hall element HEy as output terminals, and taking out the voltage V1 from the terminal T2 and taking out the voltage V2 from the terminal T4, the output after differential amplification is obtained. As D0 = (V1-V2), D0 = (H1 + H2
The value + F1 + F2) + F3 can be obtained.

However, H1 is a Hall voltage proportional to the Hall element magnetic sensitive axis component of the magnetic field originating outside the mobile equipment such as the earth magnetism, and H2 is a magnetic Hall element magnetic sensitive axis originating inside the mobile equipment such as the magnet of the speaker. Hall voltage proportional to the component,
F1 is an offset voltage of the x-axis Hall element HEx and the y-axis Hall element HEy whose sign is inverted with respect to the Hall voltage when the phase of the input terminal / output terminal is rotated by 90 degrees, and F2 is an input terminal / output terminal. Is an offset voltage of the x-axis Hall element HEx and the y-axis Hall element HEy whose sign does not change with respect to the Hall voltage when the phase is rotated by 90 degrees. Usually, F1 >> F2, and F1 is the Hall element. It accounts for most of its own offset voltage.
Further, F3 is an offset voltage of the differential input amplifier 4.

When the phase is 90 °, the x-axis Hall element H
The terminals T2 and T4 of the Ex and y-axis Hall element HEy are used as input terminals, the terminal T4 is set to the LOW level, and the terminal T2 is set to the High level. Then, the x-axis Hall element HEx and the y-axis Hall element HE
Using each terminal T1 and T3 of y as an output terminal,
Voltage V1 from the terminal T3
By taking 2 out, the output D90 after differential amplification =
As (V1-V2), D90 = (H1 + H2-F1 +
A value of F2) + F3 can be obtained.

When the phase is 180 °, the respective terminals T3 and T1 of the x-axis Hall element HEx and the y-axis Hall element HEy.
Is used as an input terminal, the terminal T1 is set to the LOW level, and the terminal T3 is set to the High level.
The x-axis Hall element HEx and the y-axis Hall element H
Using each terminal T2 and T4 of Ey as an output terminal,
By taking out the voltage V1 from the terminal 2 and the voltage V2 from the terminal T4, the output D180 after the differential amplification is obtained.
= (V1-V2), D180 =-(H1 + H2 +
The value F1 + F2) + F3 can be obtained.

When the phase is 270 °, the respective terminals T4 and T2 of the x-axis Hall element HEx and the y-axis Hall element HEy.
Is used as an input terminal, the terminal T2 is set to the LOW level, and the terminal T4 is set to the High level.
The x-axis Hall element HEx and the y-axis Hall element H
Using each terminal T1 and T3 of Ey as an output terminal,
By taking out the voltage V1 from the terminal 1 and the voltage V2 from the terminal T3, the output D360 after the differential amplification is obtained.
= (V1-V2), D360 =-(H1 + H2-
The value F1 + F2) + F3 can be obtained.

Then, by calculating these outputs by the following equations, most of the offset terms of the x-axis Hall element HEx and the y-axis Hall element HEy and the electrical offset term of the amplifier are canceled, and the x-axis Hall element HEx is canceled. Element HE
It is possible to reduce an offset term that can be canceled in terms of a circuit from the output of the x- and y-axis Hall element HEy, and reduce a change in the output due to a temperature change or the like.

(D0 + D90-D180-D360) =
H1 + H2 + F2 Next, in FIG. 1, the signals output from the x-axis Hall element HEx and the y-axis Hall element HEy are amplified by the differential input amplifier 4, and the output amplification values Dx, D amplified here.
After y is converted into a digital signal by the A / D converter 5, it is input to the correction calculator 6.

Here, the correction value storage unit 7 stores the above H2 +
The reference values Lx and Ly of the x-axis Hall element HEx and the y-axis Hall element HEy corresponding to F2 are stored, and the correction calculation unit 6 uses the reference values Lx and Ly to calculate the x-axis Hall element HEx and the y-axis. The output amplification values Dx and Dy of the Hall element HEy are corrected, and only the values α and β proportional to each axial component of the geomagnetism corresponding to the above H1 are extracted.

As the reference values Lx and Ly stored in the correction value storage unit 7, the x-axis Hall element HE measured by driving the chopper with the azimuth angle measuring device in a portable device.
The reference values Lx and Ly of the x- and y-axis Hall element HEy can be stored. Then, the correction calculation unit 6 subtracts the reference values Lx and Ly from the output amplification values Dx and Dy of the x-axis Hall element HEx and the y-axis Hall element HEy to obtain the x-axis Hall element HEx and the y-axis Hall element. From the output of HEy, only the values α and β proportional to each axial component of the earth's magnetism can be extracted.

When the correction calculator 6 obtains the values α and β proportional to the axial components of the earth's magnetism, the values α and β are output to the azimuth calculator 7. And the azimuth calculator 7
Is the sign of the values α and β proportional to each axial component of the geomagnetism, and θ
= ArcTAN (β / α), the azimuth angle θ is calculated. As a result, even if the residual offset value after canceling the offset in the chopper unit 2 remains at a level equal to or higher than the signal component, even if the signal obtained from the geomagnetism is weak, it is It is possible to calculate the azimuth angle even when there is a speaker or the like that generates a magnetism larger than the earth magnetism.

FIG. 3 is a flow chart showing an operation example of the correction calculator 6 and the azimuth calculator 8 of FIG. In FIG. 3, when the correction calculation unit 6 acquires the output amplification values Dx and Dy of the x-axis Hall element HEx and the y-axis Hall element HEy (step S1), the x-axis Hall elements HEx and y are obtained.
The reference values Lx and Ly of the axial Hall element HEy are acquired from the correction value storage unit 7 (step S2).

Next, the correction calculator 6 determines the x-axis Hall element H.
Output amplification values Dx, D of the Ex and y-axis Hall element HEy
By subtracting the reference values Lx and Ly from y, only values α and β proportional to each axial component of the earth's magnetism are extracted (step S3) and output to the azimuth angle calculation unit 8. Next, the azimuth angle calculation unit 8 calculates the azimuth angle θ by using the values α and β proportional to each axial component of the geomagnetism (step S4), and outputs the calculated azimuth angle θ (step S5). .

FIG. 4 is a block diagram showing the arrangement of an azimuth angle measuring apparatus according to the second embodiment of the present invention. In FIG. 4, a cumulative averaging unit 9 for cumulatively averaging the signals output from the correction calculation unit 6 is provided at the subsequent stage of the correction calculation unit 6 in FIG. 1. Then, the azimuth calculation unit 8 calculates the azimuth θ based on the integrated average value.

Usually, in the case of a portable device, especially a device such as a mobile phone having a limited power supply capacity, the power consumption is suppressed,
Fixed-point arithmetic is often performed to speed up the calculation. In such a case, by subtracting the reference value from the output of the Hall element, reducing the absolute value, and then performing the integration averaging, it is easy to prevent calculation overflow and keep the calculation accuracy high.

As a result, only the values α and β proportional to each axial component of the earth's magnetism are integrated and averaged to improve the S / N ratio, and the x-axis Hall element HEx and the y-axis Hall element HEy with low sensitivity can be improved. Even in the case of using, the angular resolution necessary for measuring the traveling direction of the pedestrian can be secured. FIG. 5 is a block diagram showing the configuration of the azimuth angle measuring device according to the third embodiment of the present invention.

In FIG. 5, the triaxial magnetic sensor 11, the chopper unit 12, the magnetic sensor driving power supply unit 13, the differential input amplifier 14, the A / D conversion unit 15, the correction calculation unit 16, the correction value storage unit 17, the azimuth angle. A calculation unit 18, an integrated averaging unit 19, a tilt angle calculation unit 2F, a biaxial tilt sensor 21 and a tilt sensor drive power supply unit 22 are provided, and the triaxial magnetic sensor 11 includes an x-axis Hall element HEx, a y-axis Hall element HEy, and a z-axis Hall element HEy. A shaft Hall element HEz is provided.

The x-axis Hall element HEx, the y-axis Hall element HEy, and the z-axis Hall element HEz are for detecting the earth's magnetism, for example, InSb, InAs, Ga.
A compound semiconductor system such as As is preferable. Here, the drive terminals of the x-axis Hall element HEx, the y-axis Hall element HEy, and the z-axis Hall element HEz are replaced by the chopper section 12. Then, the x-axis Hall element HEx,
The signals output from the y-axis Hall element HEy and the z-axis Hall element HEz are amplified by the differential input amplifier 14, and the output amplification values Dx, Dy, Dz amplified here are digital signals by the A / D converter 15. After being converted to
6 is input.

The biaxial tilt sensor 21 measures the tilt of the mobile terminal equipped with the azimuth measuring device and outputs the measurement results Ka and Kb to the correction calculator 16. Here, the correction value storage unit 17 stores the reference value L of the x-axis Hall element HEx, the y-axis Hall element HEy, and the z-axis Hall element HEz.
In addition to x, Ly, and Lz, the sensitivity ratio G of the x-axis Hall element HEx, the y-axis Hall element HEy, and the z-axis Hall element HEz
x, Gy, and Gz are stored.

Then, the correction calculator 16 uses the reference values Lx, Ly, Lz and the sensitivity ratios Gx, Gy, Gz to determine the x-axis Hall element HEx, the y-axis Hall element HEy and the z-axis Hall element HEz. Output amplification value D
x, Dy, Dz are corrected, and only the values α, β, γ proportional to each axial component of the earth's magnetism are extracted. FIG. 6 shows reference values Lx, Ly, Lz and a sensitivity ratio Gx according to an embodiment of the present invention.
It is a figure which shows an example of Gy and Gz.

In FIG. 6, each Hall element HEx, HE
The geomagnetic sensitivity values of y and HEz (output values of the Hall elements HEx, HEy, and HEz corresponding to the maximum value of the geomagnetic horizontal component) are 17.3, 15.9, and 18.0. Also,
Hall elements HEx, HEy, H measured without driving the chopper in a state before putting the azimuth measuring device into the portable device.
The offset value (mV) of Ez is -164.5, 3F
1.1, 1064.0, offset value (mV) of each Hall element HEx, HEy, HEz measured with a chopper driven in a state before the azimuth angle measuring device is put in the portable device.
25.3, 22.8, 16.8, the offset value (mV) of each Hall element HEx, HEy, HEz measured without the chopper drive in the state after the azimuth angle measuring device is put in the portable device. , -58.1, 253.8, 774.7,
Hall elements HEx, HEy, H measured with a chopper driven in a state before the azimuth measuring device is put in a portable device.
The offset values (mV) of Ez are 131.7, -24.
4 and -272.5.

Hall elements HEx, HEy, HEz
Was manufactured by Asahi Kasei Denshi KK: HW105C, and the driving voltage was 1.0 V and the differential input amplifier gain was 500 times. Also, as the geomagnetic sensitivity value, the Hall element is arranged so that the magnetic sensitive axis is horizontal, and is rotated at a constant speed on the horizontal plane for one revolution,
A value obtained by dividing the difference between the maximum output and the minimum output at this time by 2 was used.

Further, as the offset value, a value obtained by arranging the Hall element magnetic sensitive axis so as to be horizontal, rotating at a constant speed on the horizontal plane for one revolution, and integrating and averaging the outputs at this time for one revolution was used.
As described above, even if the same product is used, the geomagnetic sensitivity values of the Hall elements are equal to those of the Hall elements HEx, HEy,
There is a variation for each HEz, which cannot be ignored when a weak signal such as geomagnetism is measured.

Further, due to the influence of magnetism from the magnet used for the speaker of the portable equipment, the Hall elements HEx, HEy, H are placed before and after the azimuth measuring device is put in the portable equipment.
The offset value of Ez is greatly different, and the difference is equal to or higher than the signal components of the Hall elements HEx, HEy, and HEz when the earth magnetism is measured even when the chopper is used.

Therefore, when the azimuth angle measuring device is mounted on a portable device for use, the Hall elements HEx, HEy, H
The correction value storage unit 17 stores the Ez sensitivity correction value (reciprocal of the ratio) and the reference value measured after the position angle measuring device is put in the portable device. Then, the correction calculator 16 of FIG.
Is a sensitivity correction value and an azimuth angle measurement device stored in the correction value storage unit 17 in the portable device, the output amplification values Dx and Dy of the x-axis Hall element HEx, the y-axis Hall element HEy, and the z-axis Hall element HEz. Correct using the reference value measured after insertion.

Then, the azimuth calculation unit 18 calculates the corrected three-axis geomagnetic data α, β, γ and the inclination angle calculation unit 20.
The azimuth angle θ is calculated by using the inclination angles φ and η of the two axes calculated in step 1. As a result, even when the mobile terminal equipped with the azimuth measuring device is tilted, the azimuth can be calculated using the weak geomagnetism.

In the embodiment of FIG. 6, before and after the azimuth measuring device is placed in the portable device, the Hall elements HEx, H
Although the example in which the offset values of Ey and HEz are greatly different is shown, the offset values of the Hall elements HEx, HEy, and HEz are different not only before and after the azimuth measuring device is inserted into the mobile device but also depending on the usage state of the mobile device. . For example, in a foldable mobile phone, the offset values of the Hall elements HEx, HEy, and HEz are different between when the mobile phone is folded and when the mobile phone is closed.

Therefore, each Hall element HEx, HEy,
Regarding HEz, a plurality of offset values for each usage state of the mobile device are stored in the correction value storage unit 17, and the azimuth calculation unit 16
May calculate an azimuth by selecting an offset value corresponding to the current usage state of the mobile device. here,
3-axis geomagnetic data α with corrected sensitivity and offset,
When calculating the azimuth angle θ using β, γ and the inclination angle data φ, η of the two axes, the following calculation algorithm can be used.

FIG. 7 is a diagram showing the relationship between the geomagnetic vector and the rotation axis when calculating the azimuth angle θ. In FIG. 7, the TMx axis is set corresponding to the geomagnetic vector (x, y, z), and the two axes orthogonal to the TMx axis are TMy axis, T
Let it be the Mz axis. When the azimuth measuring device is mounted on the mobile terminal 10 and used, the geomagnetic vector (x,
The azimuth of the mobile terminal 10 with respect to y, z) is θ, and the depression angle is δ. In addition, the mobile terminal 10 is φ from the horizontal plane in the longitudinal direction,
It is assumed that η is inclined in the lateral direction.

Then, in order to correct the depression angle δ, TMy
Rotate -δ around the axis, and rotate the axis after this by H
X, HY, and HZ. Next, it is rotated by θ around the HZ axis, and the axes after this rotation are designated as M1x, M1y, and M1z. Next, rotate by -φ around the M1y axis, and set the axes after this rotation as M2x, M2y, and M2z.
Rotate -η around the M2x axis.

By these rotations, the following equation (1) is established between the geomagnetic vector (x, y, z) and the outputs (α, β, γ) from the Hall elements H1 to H3.

[0046]

[Equation 1]

Then, the geomagnetic vector (x, y, z) =
When the outputs (α, β, γ) from the Hall elements H1 to H3 are obtained from the relationship of (1, 0, 0), the following equation (2) is obtained.

[0048]

[Equation 2]

Next, by modifying the expression of α in the expression (2), the following expression (3) is obtained.

[0050]

[Equation 3]

Next, by substituting the equation (3) into the equations β and γ in the equation (2), the following equations (4) and (5) are obtained.

[0052]

[Equation 4]

Next, from equations (4) and (5), cos (δ)
By obtaining, the following equation (6) is obtained.

[0054]

[Equation 5]

Next, by transforming the equation (6) to obtain the azimuth angle θ, the following equation (7) is obtained.

[0056]

[Equation 6]

Thus, the triaxial geomagnetic data α, β,
By using γ and biaxial tilt angle data φ and η, the azimuth angle θ can be calculated without using the depression angle δ. FIG. 8 is a flowchart showing an operation example of the correction calculation unit 16, the tilt angle calculation unit 20, and the azimuth angle calculation unit 18 of FIG.

In FIG. 8, the correction calculator 16 acquires the output amplification values Dx, Dy, Dz of the x-axis Hall element HEx, the y-axis Hall element HEy, and the z-axis Hall element HEz (step S11), and then the x-axis Hall element HEx. Reference value L of the element HEx, the y-axis Hall element HEy, and the z-axis Hall element HEz
x, Ly, and Lz are acquired from the correction value storage unit 17 (step S12).

Next, the correction calculator 16 determines the x-axis Hall element HEx, the y-axis Hall element HEy, and the z-axis Hall element H.
From the output amplification values Dx, Dy, Dz of Ez, the reference values Lx, L
y and Lz are subtracted (step S13). Then, the subtraction result is corrected using the sensitivity ratios Gx, Gy, and Gz of the x-axis Hall element HEx, the y-axis Hall element HEy, and the z-axis Hall element HEz, and the values α, β proportional to the respective axis components of the earth's magnetism,
After taking out only γ (step S14), it outputs it to the azimuth calculation unit 18.

Next, the tilt angle calculation unit 20 acquires the output values Ka and Kb of the biaxial tilt sensor 21 (step S1).
5). Then, using the output values Ka and Kb, the inclination angles φ and η
Is calculated (step S16) and output to the azimuth angle calculation unit 18. Next, the azimuth angle calculation unit 18 calculates the azimuth angle θ by using the values α, β, γ and the inclination angles φ, η that are proportional to each axial component of the geomagnetism (step S17), and the calculated azimuth angle. The angle θ is output (step S18).

In the above embodiment, the inclination angle φ,
Although the method of using the measurement value of the biaxial tilt sensor 21 to obtain η has been described, the user sets the tilt angle,
The azimuth angle θ may be calculated using this set value.

[0062]

As described above, according to the present invention,
Even when using a magnetic sensor with low sensitivity,
Even if there is an object that generates a magnetic field larger than the earth's magnetism inside the mobile device, it is possible to measure the direction of the mobile device based on the geomagnetism, and the azimuth angle measuring device can be made smaller and less expensive, and can be installed. It is possible to reduce the conditions of mobile devices.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an azimuth angle measuring device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a driving method and an output signal of the chopper portion according to the embodiment of the present invention.

FIG. 3 is a flowchart showing an operation example of a correction calculation unit 6 and an azimuth angle calculation unit 8 of FIG.

FIG. 4 is a block diagram showing a configuration of an azimuth angle measuring device according to a second embodiment of the present invention.

FIG. 5 is a block diagram showing a configuration of an azimuth angle measuring device according to a third embodiment of the present invention.

FIG. 6 is a diagram showing an example of a correction value according to an embodiment of the present invention.

FIG. 7 is a diagram showing a relationship between a geomagnetic vector and a rotation axis according to the embodiment of the present invention.

8 is a flowchart showing an operation example of a correction calculation unit 16, a tilt angle calculation unit 20 and an azimuth angle calculation unit 18 of FIG.

[Explanation of symbols]

1 2-axis magnetic sensor 11 3-axis magnetic sensor HEx x-axis Hall element HEy y-axis Hall element HEz z-axis Hall element 2,12 Chopper part 3, 13 Magnetic sensor drive power supply 4,14 Differential input amplifier 5, 15 A / D converter 6, 16 Correction calculator 7, 17 Correction value storage 8, 18 Azimuth calculator 9, 19 Integrated averaging section 20 Tilt angle calculation unit 10 mobile terminals 21 2-axis tilt sensor 22 Tilt sensor drive power supply

Claims (9)

[Claims] 1. An azimuth measuring device mounted in a mobile device, comprising a magnetic sensor having two or more axes for detecting geomagnetism, and a first correction value for storing a reference value for each axis output of the magnetic sensor. A storage unit and a first correction calculation unit that subtracts the reference value from the output amplification value of the magnetic sensor are provided, and the mobile device is heading based on the output correction value by the first correction calculation unit. An azimuth angle measuring device comprising an azimuth angle calculating unit for calculating an azimuth. 2. An azimuth measuring device mounted in a mobile device, comprising a magnetic sensor having three or more axes for detecting geomagnetism, and a first correction value for storing a reference value for each axis output of the magnetic sensor. The storage unit includes a first correction calculation unit that subtracts the reference value from an output amplification value of the magnetic sensor, and an inclination sensor having two or more axes, and the movement based on each axis output value of the inclination sensor. The device includes a tilt angle calculation unit that calculates a tilt angle with respect to a horizontal plane, and the first correction calculation unit sets the magnetic sensor output correction values of three or more axes and the tilt angle calculation values of two or more axes. On the basis of,
An azimuth angle measuring device comprising an azimuth angle calculation unit that calculates an azimuth of a horizontal plane on which the mobile device is heading. 3. An azimuth measuring device mounted in a mobile device, comprising a magnetic sensor having three or more axes for detecting geomagnetism, and a first correction value for storing a reference value for each axis output of the magnetic sensor. A storage unit, a first correction calculation unit that subtracts the reference value from the output amplification value of the magnetic sensor, an inclination angle setting unit that sets an inclination angle, and a magnetic field of three or more axes by the first correction calculation unit. An azimuth angle measuring device comprising an azimuth angle calculation unit that calculates an azimuth of a horizontal plane on which the mobile device is heading, based on a sensor output correction value and the tilt angle set by the tilt angle setting means. 4. The first correction value storage unit stores a plurality of reference values corresponding to the usage state of the mobile device, and the first correction calculation unit corresponds to the usage state of the mobile device. The azimuth measuring device according to claim 1, wherein the reference value is selected and subtraction is performed. 5. An azimuth measuring device mounted in a mobile device, further comprising a second correction value storage section for storing a sensitivity ratio of the magnetic sensors of two or more axes, and the output of the magnetic sensor. The azimuth measuring device according to claim 1, further comprising a second correction calculation unit that multiplies a value by the sensitivity ratio. 6. An azimuth measuring device mounted in a mobile device, comprising: an integrating and averaging unit for integrating and averaging output correction values obtained by subtracting the reference value from output amplified values of the magnetic sensors of two or more axes. The azimuth measuring device according to claim 1, wherein the azimuth measuring device comprises: 7. At least one of the magnetic sensors comprises:
The azimuth measuring device according to claim 1, which is a Hall element. 8. An offset included in the output of the Hall element, the chopper section switching connection between an input terminal of a power source for driving the Hall element and a voltage output terminal of the Hall element. The azimuth measuring apparatus according to claim 7, further comprising a third correction calculation unit that subtracts the reference value after canceling most of the above. 9. The movement is based on a correction value obtained by subtracting a reference value of each axis stored in advance from each axis output of two or more axis magnetic sensors for detecting geomagnetism mounted in a mobile device. An azimuth measuring method, characterized in that the azimuth of a device is calculated.