JP2011099872A - Azimuth measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To measure an azimuth based on terrestrial magnetism detected by using a Hall element. <P>SOLUTION: A correction value storage part 7 stores reference values Lx, Ly of an x-axis Hall element HEx and a y-axis Hall element HEy, and a correction calculation part 6 subtracts offset cancelable in circuit from output amplification values Dx, Dy of the x-axis Hall element HEx and the y-axis Hall element HEy, and further subtracts the reference values Lx, Ly therefrom, to thereby take out only values α, β in proportion to each axial component of the terrestrial magnetism. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an azimuth angle measuring apparatus, and is particularly suitable for application in the case of obtaining azimuth by detecting geomagnetism.

In recent years, with the spread of mobile phones and PDAs, the need for navigation systems for pedestrians has increased, and the demand for orientation sensor systems for measuring the direction of travel together with the current position of pedestrians has increased.
In order to measure the traveling direction of a pedestrian, there has been a conventional method of detecting the geomagnetism using a highly sensitive fluxgate sensor to obtain an azimuth. In addition, as such a prior art, patent document 1 is mentioned, for example.

JP 2005-70049 A

However, since the core material and windings are used in the fluxgate sensor, the size of the device is increased, the price is also expensive, and there is an object that generates magnetism such as a speaker nearby in the mobile phone. Is not suitable for use in a navigation system for pedestrians and the like because the magnetic material saturates the core material and makes it impossible to measure geomagnetism.
Therefore, the object of the present invention is to be able to measure the orientation from the geomagnetism even when a low-sensitivity magnetic sensor is used or when it is mounted in a mobile device that has an object that generates magnetism larger than the geomagnetism nearby. It is to provide an azimuth measuring device.

  In order to solve the above-described problem, according to the azimuth angle measuring device according to claim 1, the azimuth angle measuring device mounted in a mobile device, the magnetic sensor having two or more axes for detecting geomagnetism, A first correction value storage unit that stores a reference value 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. An azimuth angle calculation unit that calculates an azimuth on which the mobile device is heading based on an output correction value by the calculation unit, and the azimuth angle measurement device is an offset that can be canceled in a circuit from the output of the magnetic sensor The reference value is subtracted from the output value obtained by subtracting.

According to the azimuth measuring apparatus according to claim 2, at least one of the magnetic sensors is a Hall element.
According to the azimuth measuring apparatus according to claim 3, the Hall element includes a chopper section that switches connection between an input terminal of a power source that drives the Hall element and a voltage output terminal of the Hall element, and The element has a first terminal pair and a second terminal pair formed of two terminals provided at positions facing each other, and the chopper portion includes the second terminal when the first terminal pair is used as an input terminal. When the terminal pair is used as an output terminal and the second terminal pair is used as an input terminal, the output voltage is output from the output terminal while switching between the input terminal and the output terminal so that the first terminal pair is used as an output terminal. Is output to the outside, and the output voltage output by switching between the input terminal and the output terminal is added or subtracted, so that the circuit included in the output of the Hall element is cancelled. After canceling most of Le possible offsets, characterized by subtracting the reference value.

  According to the azimuth measuring apparatus according to claim 4, the magnetic sensor is a magnetic sensor having three or more axes for detecting geomagnetism, and the output value of each axis of the inclination sensor having two or more axes and the inclination sensor. Based on an inclination angle calculation unit that calculates an inclination angle at which the mobile device is inclined with respect to a horizontal plane, a magnetic sensor output correction value by the first correction calculation unit, and an inclination angle calculation value of the two or more axes. And an azimuth angle calculation unit for calculating the azimuth of the horizontal plane toward which the mobile device is directed.

  Further, according to the azimuth measuring apparatus according to claim 5, the magnetic sensor is a triaxial or more magnetic sensor for detecting geomagnetism, an inclination angle setting means for setting an inclination angle, and the first correction calculation. And an azimuth angle calculation unit that calculates the azimuth of the horizontal plane on which the mobile device is facing based on the magnetic sensor output correction value by the unit and the tilt angle set by the tilt angle setting means.

Moreover, according to the azimuth measuring apparatus according to claim 6, the first correction value storage unit stores a plurality of reference values corresponding to usage states of the mobile device, and the first correction calculation unit The subtraction is performed by selecting a reference value corresponding to the usage state of the mobile device.
Further, according to the azimuth angle measuring apparatus according to claim 7, the azimuth angle measuring apparatus mounted in the mobile device, wherein the second correction value storage unit stores sensitivity ratios of the magnetic sensors having two or more axes. And a second correction calculator for multiplying the output value of the magnetic sensor by the sensitivity ratio.

Further, according to the azimuth angle measuring apparatus according to claim 8, the azimuth angle measuring apparatus mounted in a mobile device, wherein the reference value is subtracted from an output amplification value of the two or more axis magnetic sensor. It is characterized by comprising an integration averaging unit that integrates and averages the values.
According to the azimuth measuring apparatus according to claim 9, the azimuth angle measuring apparatus includes a chopper section that switches connection between an input terminal of a power source that drives the Hall element and a voltage output terminal of the Hall element, and uses the chopper section And a third correction calculator for subtracting the reference value after canceling most of the offset included in the output of the Hall element.

  As described above, according to the present invention, even when a low-sensitivity magnetic sensor is used or when there is an object that generates magnetism larger than the geomagnetism in the vicinity of the mobile device, it is based on the geomagnetism. It becomes possible to measure the azimuth of the mobile device, and it is possible to reduce the size and cost of the azimuth measuring device and relax the conditions of the mobile device that can be mounted.

It is a block diagram which shows the structure of the azimuth measuring device which concerns on 1st Embodiment of this invention. It is a figure which shows the drive method and output signal of the chopper part which concern on one Embodiment of this invention. 3 is a flowchart showing an operation example of a correction calculation unit 6 and an azimuth calculation unit 8 in FIG. 1. It is a block diagram which shows the structure of the azimuth measuring device which concerns on 2nd Embodiment of this invention. It is a block diagram which shows the structure of the azimuth measuring device which concerns on 3rd Embodiment of this invention. It is a figure which shows an example of the correction value which concerns on one Embodiment of this invention. It is a figure which shows the relationship between the geomagnetic vector which concerns on one Embodiment of this invention, and a rotating shaft. 6 is a flowchart showing an example of operations of the correction calculation unit 16, the inclination angle calculation unit 20, and the azimuth angle calculation unit 18 of FIG.

Hereinafter, an azimuth measuring device according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a configuration of an azimuth measuring apparatus according to the first embodiment of the present invention.
In FIG. 1, a biaxial magnetic sensor 1, a chopper unit 2, a magnetic sensor drive power supply unit 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 The two-axis magnetic sensor 1 is provided with an x-axis hall element HEEx and a y-axis hall element HEy.

Here, the x-axis Hall element HEEx and the y-axis Hall element HEy are for detecting geomagnetism, and are preferably compound semiconductor systems such as InSb, InAs, and GaAs.
The chopper unit 2 is used to switch terminals for driving the x-axis hall element HEx and the y-axis hall element HEy. The drive voltage output from the magnetic sensor drive power supply unit 3 is converted into the x-axis hall element HEx and the y-axis hall element HEy. Apply to.

Here, the chopper unit 2 can use, for example, 90 ° chopper driving or 360 ° chopper driving. In the 90 ° chopper drive, when driving the x-axis hall element HEx and the y-axis hall element HEy, most of the offset terms of the hall elements themselves included in the outputs of the x-axis hall element HEx and the y-axis hall element HEy are mostly used. 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 by the subsequent amplifier itself can be canceled. .

FIG. 2 is a diagram illustrating a 360 ° chopper driving method and an output signal of the chopper unit 2 according to an embodiment of the present invention.
In FIG. 2, four terminals T1 to T4 are provided in the x-axis hall element HEEx and the y-axis hall element HEy. In the 360 ° chopper driving method, the x-axis Hall element HEEx and the y-axis Hall element HEy are driven while switching the input terminal and the output terminal for every four phases.

  When the phase is 0 °, the terminals T1 and T3 of the x-axis hall element HEx and the y-axis hall element HEy are used as input terminals, the terminal T3 is set to the LOW level, and the terminal T1 is set to the high level. Set. Then, using the terminals T2 and T4 of the x-axis hall element HEEx and the y-axis hall element HEy as output terminals, the voltage V1 is taken out from the terminal T2 and the voltage V2 is taken out from the terminal T4, whereby the output after differential amplification As D0 = (V1-V2), a value of D0 = (H1 + H2 + F1 + F2) + F3 can be obtained.

  However, H1 is a Hall voltage proportional to the Hall element magnetosensitive axis component of the magnetic field originating from the outside of the mobile device such as geomagnetism, and H2 is proportional to the magnetic Hall element magnetosensitive axis component originating from inside the mobile device such as the speaker magnet. Hall voltage F1 is the offset voltage of the x-axis Hall element HEx and the y-axis Hall element HEy whose signs are inverted with respect to the Hall voltage when the phase of the input terminal / output terminal is rotated by 90 degrees, and F2 is the input voltage This is the offset voltage of the x-axis hall element HEx and the y-axis hall element HEy whose signs do not change with respect to the hall voltage when the phase of the terminal / output terminal is rotated by 90 degrees, usually F1 >> F2, F1 accounts for most of the offset voltage of the Hall element itself. F3 is an offset voltage of the differential input amplifier 4.

  When the phase is 90 °, the terminals T2 and T4 of the x-axis hall element HEx and the 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, using the terminals T1 and T3 of the x-axis hall element HEx and the y-axis hall element HEy as output terminals, the voltage V1 is taken out from the terminal T1 and the voltage V2 is taken out from the terminal T3, whereby the output after differential amplification As D90 = (V1-V2), a value of D90 = (H1 + H2-F1 + F2) + F3 can be obtained.

  When the phase is 180 °, the terminals T3 and T1 of the x-axis hall element HEx and the y-axis hall element HEy are used as input terminals, the terminal T1 is set to the LOW level, and the terminal T3 is set to the high level. Then, using the terminals T2 and T4 of the x-axis hall element HEEx and the y-axis hall element HEy as output terminals, the voltage V1 is taken out from the terminal T2 and the voltage V2 is taken out from the terminal T4, whereby the output after differential amplification As D180 = (V1−V2), a value of D180 = − (H1 + H2 + F1 + F2) + F3 can be obtained.

  When the phase is 270 °, the terminals T4 and T2 of the x-axis hall element HEx and the y-axis hall element HEy are used as input terminals, the terminal T2 is set to the LOW level, and the terminal T4 is set to the high level. Then, using the terminals T1 and T3 of the x-axis hall element HEx and the y-axis hall element HEy as output terminals, the voltage V1 is taken out from the terminal T1 and the voltage V2 is taken out from the terminal T3, whereby the output after differential amplification As D360 = (V1-V2), a value of D360 =-(H1 + H2-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 y-axis hall element HEy and the electrical offset term of the amplifier are canceled, and the x-axis hall element HEx and A change in output due to a temperature change or the like can be reduced by subtracting an offset term that can be canceled in terms of circuit from the output of the y-axis Hall element HEy.
(D0 + D90-D180-D360) = H1 + H2 + F2

Next, in FIG. 1, 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 amplified output amplification values Dx and Dy are A / D converted. After being converted to a digital signal by the unit 5, it is input to the correction calculation unit 6.
Here, the correction value storage unit 7 stores reference values Lx and Ly of the x-axis Hall element HEx and the y-axis Hall element HEy corresponding to the above H2 + F2, and the correction calculation unit 6 stores the reference values Lx and Ly. By using it, the output amplification values Dx and Dy of the x-axis Hall element HEx and the y-axis Hall element HEy are corrected, and only the values α and β proportional to the respective geomagnetism axis components corresponding to H1 are extracted.

In addition, as the reference values Lx and Ly stored in the correction value storage unit 7, the reference of the x-axis hall element HEEx and the y-axis hall element HEy measured by chopper driving in a state where the azimuth measuring device is put in a portable device. Values Lx and Ly 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, thereby obtaining the x-axis hall element HEx and the y-axis hall element. Only values α and β proportional to each axis component of geomagnetism can be extracted from the output of HEy.

When values α and β proportional to each axis component of geomagnetism are taken out by the correction calculation unit 6, the values α and β are output to the azimuth calculation unit 7. Then, the azimuth angle calculation unit 7 calculates the azimuth angle θ based on the signs of the values α and β proportional to each axis component of geomagnetism and the equation θ = arcTAN (β / α).
Thereby, even if the signal obtained from the geomagnetism is weak, the residual offset value after canceling the offset by the chopper unit 2 remains equal to or higher than the signal component, and also near the portable device, The azimuth angle can be calculated even when there is something that generates magnetism larger than geomagnetism, such as a speaker.

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

Next, 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, thereby obtaining a value α proportional to each axis component of geomagnetism. Only β is extracted (step S3) and output to the azimuth calculation unit 8.
Next, the azimuth angle calculation unit 8 calculates the azimuth angle θ by using values α and β proportional to each axis component of geomagnetism (step S4), and outputs the calculated azimuth angle θ (step S5). .

FIG. 4 is a block diagram showing a configuration of an azimuth measuring apparatus according to the second embodiment of the present invention.
In FIG. 4, an integration averaging unit 9 for integrating and averaging the signals output from the correction calculation unit 6 is provided at the subsequent stage of the correction calculation unit 6 of FIG. 1. Then, the azimuth angle calculation unit 8 calculates the azimuth angle θ based on the integrated average value.
In general, in the case of a portable device, particularly a device having a limited power supply capacity such as a cellular phone, fixed-point arithmetic is often performed in order to reduce power consumption or increase calculation speed.

In such a case, by subtracting the reference value from the output of the Hall element to reduce the absolute value and then performing integration averaging, it becomes easy to prevent calculation overflow and maintain high calculation accuracy.
As a result, only the values α and β proportional to each axis component of geomagnetism can be integrated and averaged to improve the S / N ratio, and the low-sensitivity x-axis hall element HEx and y-axis hall element HEy were used. Even in such a case, it is possible to ensure the angular resolution necessary for measuring the traveling direction of the pedestrian.

FIG. 5 is a block diagram showing a configuration of an azimuth measuring apparatus according to the third embodiment of the present invention.
In FIG. 5, a three-axis magnetic sensor 11, a chopper unit 12, a magnetic sensor drive power supply unit 13, a differential input amplifier 14, an A / D conversion unit 15, a correction calculation unit 16, a correction value storage unit 17, and an azimuth angle calculation unit 18. , An integration average unit 19, an inclination angle calculation unit 2F, a 2-axis inclination sensor 21, and an inclination sensor drive power supply unit 22, and the 3-axis magnetic sensor 11 includes an x-axis hall element HEEx, a y-axis hall element HEy, and a z-axis hall element. HEz is provided.

Note that the x-axis hall element HEEx, the y-axis hall element HEy, and the z-axis hall element HEz are for detecting geomagnetism, and are preferably compound semiconductors such as InSb, InAs, and GaAs.
Here, the drive terminals of the x-axis hall element HEEx, the y-axis hall element HEy, and the z-axis hall element HEz are switched by the chopper unit 12. The signals output from the x-axis hall element HEEx, the y-axis hall element HEy, and the z-axis hall element HEz are amplified by the differential input amplifier 14, and the amplified output amplification values Dx, Dy, and Dz are A After being converted to a digital signal by the / D conversion unit 15, it is input to the correction calculation unit 16.
The biaxial tilt sensor 21 measures the tilt of the mobile terminal on which the azimuth measuring device is mounted, and outputs the measurement results Ka and Kb to the correction calculation unit 16.

Here, in the correction value storage unit 17, in addition to the reference values Lx, Ly, Lz of the x-axis hall element HEx, the y-axis hall element HEy, and the z-axis hall element HEz, the x-axis hall element HEx, the y-axis hall element HEy. And the sensitivity ratios Gx, Gy, Gz of the z-axis Hall element HEz are stored.
Then, the correction calculation unit 16 uses these reference values Lx, Ly, Lz and sensitivity ratios Gx, Gy, Gz to amplify the output of the x-axis hall element HEx, the y-axis hall element HEy, and the z-axis hall element HEz. The values Dx, Dy, Dz are corrected, and only the values α, β, γ proportional to the geomagnetism axis components are taken out.

FIG. 6 is a diagram illustrating an example of reference values Lx, Ly, Lz and sensitivity ratios Gx, Gy, Gz according to an embodiment of the present invention.
In FIG. 6, the geomagnetic sensitivity values of the Hall elements HEEx, HEy, HEz (the output values of the Hall elements HEx, HEy, HEz corresponding to the maximum value of the horizontal horizontal component) are 17.3, 15.9, 18. 0.

  In addition, the offset values (mV) of the Hall elements HEx, HEy, and HEz measured without chopper driving before the azimuth measuring device is put in the portable device are -164.5, 301.0, and 1064.0. The offset value (mV) of each Hall element HEx, HEy, HEz measured with chopper driving in the state before putting the azimuth measuring device into the portable device is 25.3, 22.8, 16.8, azimuth The offset value (mV) of each Hall element HEx, HEy, HEz measured without chopper driving in the state after the angle measuring device is put in the portable device is −58.1, 253.8, 774.7, direction The offset values (mV) of each Hall element HEx, HEy, HEz measured with chopper driving in the state before putting the angle measuring device into the portable device are 131.7, −24.4, −272. It is.

The Hall elements HEEx, HEy, and HEz were manufactured by Asahi Kasei Electronics Co., Ltd .: HW105C, and the driving voltage was 1.0 V and the differential input amplifier gain was 500 times.
In addition, as the geomagnetic sensitivity value, the Hall element magnetosensitive axis is arranged horizontally, rotated at a uniform speed around the horizontal plane, and the value obtained by dividing the difference between the maximum output and the minimum output at this time by 2 is used. It was.
Further, as the offset value, a value obtained by arranging the Hall element magnetosensitive axis to be horizontal, rotating it at a uniform speed around the horizontal plane, and integrating the output at this time over one round was used.

As described above, even when the same product is used, the Hall element's geomagnetic sensitivity value varies for each Hall element HEx, HEy, and HEz, and is ignored when measuring weak signals such as geomagnetism. Can not.
Also, due to the influence of magnetism from a magnet used for a speaker of a portable device, the offset values of the Hall elements HEx, HEy, HEz are greatly different before and after the azimuth measuring device is inserted into the portable device, and the difference is Even when a chopper is used, the level is equal to or higher than the signal component of each Hall element HEEx, HEy, HEz when geomagnetism is measured.

Therefore, when the azimuth measuring device is mounted on a portable device and used, the sensitivity correction values (reciprocal of the ratio) of each Hall element HEx, HEy, and HEz and the position measuring device in a state after being put in the portable device. The measured reference value is stored in the correction value storage unit 17.
Then, the correction calculation unit 16 of FIG. 5 uses the sensitivity correction values stored in the correction value storage unit 17 as 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. And it correct | amends using the reference value measured in the state after putting an azimuth measuring device in a portable apparatus.

The azimuth angle calculation unit 18 uses the corrected geomagnetic triaxial data α, β, γ and the biaxial inclination angles φ, η calculated by the inclination angle calculation unit 20 to obtain an azimuth angle. θ is calculated.
Thereby, even when the portable terminal equipped with the azimuth measuring device is tilted, the azimuth can be calculated using weak geomagnetism.

In the embodiment of FIG. 6, an example in which the offset values of the Hall elements HEx, HEy, and HEz differ greatly before and after the azimuth measuring device is inserted into the portable device is shown. However, the Hall elements HEx, HEy, and HEz The offset value varies not only before and after inserting the azimuth measuring device into the portable device, but also depending on the usage state of the portable device.
For example, in a foldable mobile phone, the offset values of the hall elements HEx, HEy, and HEz differ between a state in which the mobile phone is folded and a state in which the mobile phone is closed.

For this reason, for each Hall element HEx, HEy, HEz, a plurality of offset values for each use state of the portable device are stored in the correction value storage unit 17, and the direction calculation unit 16 is an offset corresponding to the current use state of the portable device. The direction may be calculated by selecting a value.
Here, when the azimuth angle θ is calculated using the triaxial geomagnetic data α, β, γ and the biaxial tilt angle data φ, η corrected for sensitivity and offset, 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, TMx axes are set corresponding to geomagnetic vectors (x, y, z), and two axes orthogonal to the TMx axes are defined as TMy axes and TMz axes.
When the azimuth measuring device is mounted on the mobile terminal 10 and used, the orientation of the mobile terminal 10 with respect to the geomagnetic vector (x, y, z) is θ and the depression angle is δ. Further, the mobile terminal 10 is inclined from the horizontal plane by φ in the longitudinal direction and by η in the short direction.

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

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

  Next, by transforming the formula of α in the formula (2), the following formula (3) is obtained.

  Next, when the expression (3) is substituted into the expressions β and γ in the expression (2), the following expressions (4) and (5) are obtained.

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

  Next, when the azimuth angle θ is obtained by modifying the equation (6), the following equation (7) is obtained.

Thus, the azimuth angle θ can be calculated without using the depression angle δ by using the triaxial geomagnetic data α, β, γ and the biaxial tilt angle data φ, η.
FIG. 8 is a flowchart showing an operation example of the correction calculation unit 16, the inclination angle calculation unit 20, and the azimuth angle calculation unit 18 of FIG.
In FIG. 8, when the correction calculation unit 16 obtains 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), the x-axis hall element HEx, Reference values Lx, Ly, Lz of the y-axis hall element HEy and the z-axis hall element HEz are acquired from the correction value storage unit 17 (step S12).

  Next, the correction calculation unit 16 subtracts the reference values Lx, Ly, and Lz from the output amplification values Dx, Dy, and Dz of the x-axis hall element HEx, the y-axis hall element HEy, and the z-axis hall element HEz (step S13). . Then, the subtraction result is corrected using the sensitivity ratios Gx, Gy, Gz of the x-axis hall element HEx, the y-axis hall element HEy, and the z-axis hall element HEz, and values α, β, γ proportional to the respective geomagnetism axis components are corrected. After taking out only (step S14), it outputs to the azimuth angle calculation part 18.

Next, the inclination angle calculation unit 20 acquires the output values Ka and Kb of the biaxial inclination sensor 21 (step S15). Then, the inclination angles φ and η are calculated using the output values Ka and Kb (step S 16) 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 proportional to each axis component of the geomagnetism (step S17), and the calculated azimuth The angle θ is output (step S18).
In the above-described embodiment, the method of using the measured values of the biaxial tilt sensor 21 to determine the tilt angles φ and η has been described. However, the user sets the tilt angle, and using the set values, The azimuth angle θ may be calculated.

  The azimuth measuring device of the present invention described above can be applied to any device that uses a magnetic sensor to determine the azimuth, but when a low-sensitivity magnetic sensor is used, or the azimuth angle This is particularly effective when there is an object that generates magnetism greater than the geomagnetism near the equipment on which the measuring device is mounted.

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 part 4, 14 Differential input amplifier 5, 15 A / D conversion unit 6, 16 Correction calculation unit 7, 17 Correction value storage unit 8, 18 Azimuth angle calculation unit 9, 19 Cumulative average unit 20 Tilt angle calculation unit 10 Portable terminal 21 Biaxial tilt sensor 22 Tilt sensor drive power supply unit

Claims (9)

An azimuth measuring device mounted in a mobile device,
Two or more axis magnetic sensors for detecting geomagnetism,
A first correction value storage unit for storing a reference value for each axis output of the magnetic sensor;
A first correction calculator for subtracting the reference value from the output amplification value of the magnetic sensor;
An azimuth angle calculation unit that calculates an azimuth on which the mobile device is headed based on an output correction value by the first correction calculation unit;
With
The azimuth angle measuring apparatus subtracts the reference value from an output value obtained by subtracting an offset that can be canceled in a circuit from the output of the magnetic sensor. The azimuth angle measuring apparatus according to claim 1, wherein at least one of the magnetic sensors is a Hall element. The Hall element includes a chopper unit that switches connection between an input terminal of a power source that drives the Hall element and a voltage output terminal of the Hall element,
The Hall element has a first terminal pair and a second terminal pair composed of two terminals provided at positions facing each other, and the chopper portion is configured so that the first terminal pair is used as an input terminal. When the second terminal pair is used as an output terminal and the second terminal pair is used as an input terminal, the input terminal and the output terminal are switched so that the first terminal pair is used as an output terminal. Output the output voltage to the outside
After canceling most of the circuit-cancellable offset included in the output of the Hall element by adding and subtracting the output voltage output by switching between the input terminal and the output terminal, the reference value is The azimuth angle measuring device according to claim 2, wherein the azimuth angle measuring device is subtracted. The magnetic sensor is a triaxial or more magnetic sensor that detects geomagnetism,
A tilt sensor with two or more axes;
An inclination angle calculation unit that calculates an inclination angle at which the mobile device is inclined with respect to a horizontal plane, based on each axis output value of the inclination sensor;
An azimuth angle calculation unit that calculates the azimuth of the horizontal plane toward which the mobile device is facing based on the magnetic sensor output correction value by the first correction calculation unit and the tilt angle calculation value of the two or more axes. The azimuth measuring apparatus according to any one of claims 1 to 3, wherein The magnetic sensor is a triaxial or more magnetic sensor that detects geomagnetism,
An inclination angle setting means for setting an inclination angle;
An azimuth angle calculation unit that calculates the azimuth of the horizontal plane toward which the mobile device is facing, based on the magnetic sensor output correction value by the first correction calculation unit and the tilt angle set by the tilt angle setting unit. The azimuth measuring device according to any one of claims 1 to 3, wherein The first correction value storage unit stores a plurality of reference values corresponding to usage states of the mobile device,
The azimuth measuring apparatus according to claim 1, wherein the first correction calculation unit performs subtraction by selecting a reference value corresponding to a usage state of the mobile device. An azimuth measuring device mounted in a mobile device,
A second correction value storage unit for storing a sensitivity ratio of the two or more magnetic sensors;
The azimuth angle measuring apparatus according to claim 1, further comprising a second correction calculation unit that multiplies the output value of the magnetic sensor by the sensitivity ratio. An azimuth measuring device mounted in a mobile device,
The azimuth angle according to any one of claims 1 to 7, further comprising an integration averaging unit that integrates and averages output correction values obtained by subtracting the reference value from output amplification values of the two or more axis magnetic sensors. Measuring device. A chopper unit that switches connection between an input terminal of a power source that drives the Hall element and a voltage output terminal of the Hall element, and
8. A third correction calculation unit that subtracts the reference value after canceling most of the offset included in the output of the Hall element using the chopper unit. The azimuth measuring device according to claim 1.

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