JP4643716B2 - Electronic compass - Google Patents

Description

  The present invention relates to an electronic compass capable of accurately measuring an azimuth.

  Conventionally, an electronic compass mounted on a mobile phone or the like is known. This electronic compass is equipped with a triaxial magnetic sensor that detects the intensity of geomagnetism in the triaxial directions of the X, Y, and Z axes. Based on this detection value, the orientation that the mobile phone is facing is calculated and displayed. Display on the screen.

  However, since many electronic components are mounted on the mobile terminal, the mobile terminal itself is magnetized, and this magnetic field (internal magnetic field) has a problem that the detection value of the three-axis magnetic sensor becomes inaccurate. The internal magnetic field changes even when the portable terminal approaches the magnet, the temperature changes, or an impact is applied. Therefore, an electronic compass has been developed that can correct the detection error of the three-axis magnetic sensor due to the internal magnetic field of the mobile terminal (see the following patent document).

  A specific correction method will be described. By changing the attitude of the mobile terminal, the detection value (Xi, Yi, Zi) of the three-axis magnetic sensor changes. This detection value exists on the surface of a sphere (hereinafter referred to as an orientation sphere). When there is an influence of the internal magnetic field, the center point of the azimuth sphere does not coincide with the origin of the three-axis magnetic sensor and is offset. By setting the center point of this azimuth sphere as the origin of the three-axis magnetic sensor, the influence of the internal magnetic field can be removed.

JP 2008-107102 A JP-A-6-58758

In order to obtain the center point of the azimuth sphere, for example, the following method is adopted.
(1) A method in which the user performs an operation of rotating the mobile terminal once in the X-axis, Y-axis, and Z-axis directions, and calculates the center point using the median value of the maximum value and the minimum value.
(2) The user performs an operation of rotating the mobile terminal greatly, and thereby, four detection values that exist on the surface of the bearing sphere and are separated from each other are acquired. A method of calculating the center point of the azimuth sphere using these four detection values.

  However, when the above method is used, there is a problem that it is difficult for the user to use the mobile terminal because it is necessary to rotate the mobile terminal greatly, and further, a three-dimensional rotation is required. Moreover, since a large rotation operation is assumed, automatic correction is difficult.

  The present invention has been made in view of such conventional problems, and can correct the center point of the azimuth sphere while minimizing the rotation operation of the mobile terminal performed by the user, and is based on the internal magnetic field of the mobile terminal. It is intended to provide an electronic compass that can calculate the correct bearing without the influence.

The first invention is an electronic compass that is provided in a mobile terminal and detects an orientation in which the mobile terminal faces while correcting the influence of the internal magnetic field of the mobile terminal,
A three-axis magnetic sensor that is fixed to the portable terminal and that detects the geomagnetism intensity in the three-axis directions of the X axis, the Y axis, and the Z axis that are orthogonal to each other;
The detected value (Xi, Yi, Zi) of the geomagnetism by the three-axis magnetic sensor calculates the center point of the azimuth sphere drawn with the attitude change of the mobile terminal, and the center point after the calculation is the center after the calculation Center point correction means for correcting the point;
Azimuth calculating means for correcting the detected value of the geomagnetism by the three-axis magnetic sensor using the corrected coordinates of the center point and calculating the azimuth of the portable terminal using the corrected detected value; With
The center point correcting means calculates a center axis of a circle including the first detection value, the second detection value, and the third detection value detected by the three-axis magnetic sensor, and the first detection value , Passing through an intermediate point of a straight line connecting one detection value of the second detection value and the third detection value and the fourth detection value existing at a position off the plane including the circle. , The intersection of the perpendicular bisector perpendicular to the straight line and the central axis is calculated as the center point of the azimuth sphere ,
The first detection value, the second detection value, and the third detection value are acquired while the operation of confirming the azimuth is performed by the user of the mobile terminal, and the first detection value is further acquired for the user. In order to obtain 4 detection values, the electronic compass is provided with a reversing operation notifying means for notifying that a mobile reversing operation for reversing the mobile terminal is performed (Claim 1).
A second invention is an electronic compass that is provided in a mobile terminal and detects an orientation that the mobile terminal faces while correcting the influence of the internal magnetic field of the mobile terminal.
A three-axis magnetic sensor that is fixed to the portable terminal and that detects the geomagnetism intensity in the three-axis directions of the X axis, the Y axis, and the Z axis that are orthogonal to each other;
The detected value (Xi, Yi, Zi) of the geomagnetism by the three-axis magnetic sensor calculates the center point of the azimuth sphere drawn with the attitude change of the mobile terminal, and the center point after the calculation is the center after the calculation Center point correction means for correcting the point;
Azimuth calculating means for correcting the detected value of the geomagnetism by the three-axis magnetic sensor using the corrected coordinates of the center point and calculating the azimuth of the portable terminal using the corrected detected value; With
The center point correcting means calculates a center axis of a circle including the first detection value, the second detection value, and the third detection value detected by the three-axis magnetic sensor, and the first detection value , Passing through an intermediate point of a straight line connecting one detection value of the second detection value and the third detection value and the fourth detection value existing at a position off the plane including the circle. , The intersection of the perpendicular bisector perpendicular to the straight line and the central axis is calculated as the center point of the azimuth sphere,
In an application utilizing the direction function of the electronic compass, a horizontal rotation operation capable of detecting the first detection value, the second detection value, and the third detection value, and the fourth detection value can be detected. An electronic compass comprising automatic correction means for automatically calculating and correcting the center point of the azimuth sphere during execution of a command for performing a reversing operation or a tilting operation (claim 2). .

Next, the function and effect of the first invention will be described.
According to the above configuration, since the first detection value, the second detection value, and the third detection value can be acquired while the user is using the electronic compass, the rotation operation for acquiring the fourth detection value is performed. The center point of the azimuth sphere can be calculated by imposing it only once on the user. In addition, since this rotation operation is a small rotation operation that can be done by rotating it about 90 ° in one direction, it is easier to perform compared to the conventional case of rotating it around the X, Y, and Z axes. It is.

  While using the electronic compass, the user naturally performs an operation of rotating the portable terminal about the vertical axis in order to confirm the traveling direction. While this operation is performed, the first detection value to the third detection value are acquired, and the central axis is calculated. And a 4th detection value is acquired by the operation which a user turns over and tilts a portable terminal. Accordingly, the vertical bisector can be calculated, and the center point of the azimuth sphere can be obtained by calculating the intersection of the vertical bisector and the central axis.

  By correcting the detection value of the three-axis magnetic sensor using the center point of the azimuth sphere, it is possible to obtain the detection value of geomagnetism from which the influence of the internal magnetic field is removed. As a result, the orientation of the mobile terminal can be accurately obtained. If the tilting operation or the reversing operation corresponds to the zoom-up or screen switching required when using the electronic compass, the user can naturally perform this operation and perform the center point correction of the azimuth sphere without intending it. That is, automatic calibration is possible.

Further, the present invention includes the above reversal operation notifying means.
If it does in this way, in order to notify a user to carry out carrying inversion operation, the 4th detection value can be acquired certainly. As a result, the center point of the azimuth sphere can be reliably calculated, and an accurate azimuth can be obtained without the influence of the internal magnetic field of the mobile terminal.
Next, the function and effect of the second invention will be described. The second invention includes the automatic correction means.
The reversing operation is an operation of reversing the mobile terminal by about 180 °, and the tilting operation is an operation of tilting the mobile terminal by a smaller angle. When the user executes this command, a specific command can be given to the portable terminal. For example, when the reverse operation is performed, the screen can be zoomed or switched.
When the user uses the electronic compass, the horizontal rotation operation for rotating the portable terminal in the horizontal direction is naturally performed, and thus the first to third detection values can be acquired during this time. When the user performs the reversing operation or the tilting operation, the specific command is executed, and the fourth detection value is acquired together with the specific command. Then, the center point of the azimuth sphere is calculated and automatically corrected.
As a result, the center point can be corrected without the user being aware of anything.
As described above, according to the present invention, the center point of the azimuth sphere can be automatically corrected while minimizing the rotation operation of the mobile terminal performed by the user, and the influence of the internal magnetic field of the mobile terminal is eliminated. An electronic compass capable of calculating an accurate orientation can be provided.

1 is a partially cutaway perspective view of a mobile terminal according to Embodiment 1. FIG. 1 is a block diagram of an electronic compass in Embodiment 1. FIG. FIG. 3 is an explanatory diagram of an orientation sphere in Example 1. FIG. 3 is a diagram for explaining a method for calculating a center point of an orientation sphere according to the first embodiment. The figure for demonstrating the relationship between a portable terminal and direction (theta) in Example 1. FIG. 2 is a simplified diagram of a three-axis magnetic sensor in Embodiment 1. FIG. 2 is a flowchart of a program according to the first embodiment. 10 is a flowchart of a program according to the second embodiment. 10 is a flowchart of a program according to the third embodiment. 10 is a flowchart of a program according to the fourth embodiment.

Further, the absolute value R of the geomagnetism is calculated from the detected value (Xi, Yi, Zi) by using the following mathematical formula,
R = √ (Xi ² + Yi ² + Zi ² )
An abnormality determining means for determining whether or not the R is within a predetermined range, and when the R is determined not to be within the predetermined range by the abnormality determining means, the center point correcting means It is preferable to perform correction (Claim 3 ).
In this way, the center point of the azimuth sphere can be corrected only when the mobile terminal approaches a magnet or the like and the detected value of the three-axis magnetic sensor is determined to be abnormal. Therefore, it is not necessary to calculate or correct the center point of the azimuth sphere when the detection value is normal.

Also, when the newly calculated center point is (a2, b2, c2) and the center point before calculation is (a1, b1, c1), the following formula R1 = √ ((Xi−a1) ² + (Yi-b1) ² + (Zi-c1) ² )
R2 = √ ((Xi−a2) ² + (Yi−b2) ² + (Zi−c2) ² )
Is used to calculate absolute values R1 and R2 of geomagnetism for a plurality of detection values (Xi, Yi, Zi) other than the first detection value to the fourth detection value, and the maximum value R1 _max and the minimum value of R1 are calculated. A difference ΔR1 between the values R1 _{min and} a difference ΔR2 between the maximum value R2 _max and the minimum value R2 _min of R2 are obtained, and improvement determination means for determining whether ΔR2 is smaller than ΔR1 is provided. Is determined to be smaller than ΔR1, the center point is preferably corrected from (a1, b1, c1) to (a2, b2, c2) (Claim 4 ).
Although the center point before correction is more accurate, and it can be assumed that the detection of the geomagnetism becomes inaccurate by correction, this problem can be prevented by adopting the above-described configuration.

In addition, a triaxial acceleration sensor that detects each intensity of gravitational acceleration in the triaxial direction is provided.
A depression angle abnormality determining means for calculating a depression angle of the geomagnetism from a detection value of the three-axis acceleration sensor and a detection value of the three-axis magnetic sensor and determining whether the depression angle is within a predetermined range; If the above-mentioned dip angle is determined not to be within the predetermined range by該伏angle abnormality determination means, it is preferable to correct the center point (claim 5).
In this way, the center point of the azimuth sphere can be corrected only when the mobile terminal approaches, for example, a magnet or the like and the geomagnetic dip is determined to be abnormal. Therefore, it is not necessary to calculate or correct the center point of the azimuth sphere when the dip angle is normal.

Example 1
An electronic compass according to an embodiment of the present invention will be described with reference to FIGS.
This example is an electronic compass 1 that is provided in the mobile terminal 2 and detects the direction in which the mobile terminal 2 faces while correcting the influence of the internal magnetic field of the mobile terminal 2. As shown in FIG. 1, an electronic compass 1 of this example is fixed to a portable terminal 2 and detects three intensities of geomagnetism in three axial directions of an X axis, a Y axis, and a Z axis that are orthogonal to each other. A magnetic sensor 3 is provided.
Further, as shown in FIG. 3, the detected value P (Xi, Yi, Zi) of the geomagnetism by the three-axis magnetic sensor 3 calculates the center point O2 of the azimuth sphere 6 drawn with the attitude change of the mobile terminal 2, Center point correcting means 40 (see FIG. 2) for correcting the center point O1 before calculation to the center point O2 after calculation is provided.
Further, as shown in FIG. 3, using the coordinates of the corrected center point O2, the detection value P (Xi, Yi, Zi) of the geomagnetism by the triaxial magnetic sensor 3 is corrected, and the detection value after the correction is calculated. An azimuth calculating means 41 (see FIG. 2) for calculating the azimuth in which the mobile terminal 2 is directed is provided.
As shown in FIG. 4, the center point correction means 40 includes a first detection value P1 (X1, Y1, Z1) detected by the triaxial magnetic sensor 3, a second detection value P2 (X2, Y2, Z2), While calculating the central axis 7 of the circle 70 including the third detection value P3 (X3, Y3, Z3), one of the first detection value P1, the second detection value P2, and the third detection value P3. A vertical bisector 8 perpendicular to the straight line 81 passing through the midpoint 80 of the straight line 81 connecting one detected value and the fourth detected value P4 existing at a position off the plane including the circle 70, and the center The intersection with the axis 7 is calculated as the center point O 2 of the azimuth sphere 6.

  As shown in FIG. 1, in this example, a three-axis magnetic sensor 3 and a microcomputer 4 are mounted on a mobile terminal 2 (mobile phone). The Z axis of the three-axis magnetic sensor 3 is oriented in the direction perpendicular to the operation surface 150 of the mobile terminal 2, and the X axis is oriented in the lateral width direction of the mobile terminal 2. Further, the Y axis is oriented in a direction perpendicular to both the X axis and the Z axis.

  A simplified diagram of the triaxial magnetic sensor 3 is shown in FIG. Thus, the triaxial magnetic sensor 3 has a structure in which the three amorphous wires (magnetic sensitive bodies) 30x to 30z and the control unit 32 are mounted on the substrate 31. These three amorphous wires 30x to 30z are directed in the X-axis direction, the Y-axis direction, and the Z-axis direction, respectively, and detect the X-axis component, the Y-axis component, and the Z-axis component of the geomagnetic vector, respectively.

  As shown in FIG. 2, the microcomputer 4 described above includes a CPU 50, a ROM 51, a RAM 52, an I / O 54, and a line 53 that connects them. The microcomputer 4 includes a transmission / reception unit 111, a communication control unit 11, a rear speaker 12, a vibrator for incoming notification, a GPS antenna 18, a GPS positioning unit 19, a triaxial acceleration sensor 17, a display unit 14, an operation unit 15, a microphone / speaker. 16 is connected. The ROM 51 stores a program 51p, and the CPU 50 reads out and executes the program 51p, whereby the center point correcting means 40, the direction calculating means 41, the reversing operation notifying means 42, and the automatic correcting means 43 of the present invention. The abnormality determination unit 44, the improvement determination unit 45, and the depression angle abnormality determination unit 46 are realized.

Next, a method for correcting the detected value of geomagnetism will be described with reference to FIG. 3 is an azimuth sphere before correction, and 6 is an azimuth sphere after correction. The center point O 1 is the center point of the azimuth sphere 60, and the center point O 2 is the center point of the azimuth sphere 6.
The center point of the triaxial magnetic sensor 3 does not coincide with the origin O of the X axis, the Y axis, and the Z axis, and the center point is offset due to the influence of the internal magnetic field of the mobile terminal 2. Since the internal magnetic field also changes depending on the environment such as temperature, the center point also changes from O1 to O2 accordingly.

The azimuth sphere 6 including the first detection value P1 to the fourth detection value P4 acquired by the triaxial magnetic sensor 3 is calculated, and the center point O2 (a2, b2, c2) is obtained. By setting the center point O2 as the center of the three-axis magnetic sensor, the influence of the internal magnetic field can be removed.
That is, the detected value OP vector (Xi, Yi, Zi) affected by the internal magnetic field can be corrected to an accurate geomagnetic O2P vector by using the following formula.

方位θは、図５に示すごとく、３軸磁気センサ３のＹ軸を水平面Ｈに投影し、その投影ベクトルＹ’と、磁北に向かうベクトル５０とのなす角度である。 Next, a method for calculating the orientation of the mobile terminal 2 will be described. The corrected geomagnetism (Xi-a2, Yi-b2, Zi-c2) = (Mx, My, Mz). Further, the detected value of the gravitational acceleration G by the above-described triaxial acceleration sensor 17 is assumed to be (Gx, Gy, Gz). From these detection values, the orientation θ of the mobile terminal 2 at the terminal tilted by the roll angle η and the pitch angle φ can be calculated by using, for example, the following mathematical formula.

As shown in FIG. 5, the azimuth θ is an angle formed by projecting the Y axis of the three-axis magnetic sensor 3 onto the horizontal plane H and the projection vector Y ′ and the vector 50 heading toward magnetic north.

  Next, referring to FIG. 4, the first detection value P1 (X1, Y1, Z1), the second detection value P2 (X2, Y2, Z2) acquired by the three-axis magnetic sensor, and the third detection value P3 ( A method of calculating the center point O2 (a2, b2, c2) of the azimuth sphere 6 using the X3, Y3, Z3) and the fourth detection value P4 (X4, Y4, Z4) will be described.

First, it is confirmed that the detected values P1, P2, and P3 are separated from the predetermined distance k1 by using the following mathematical formula.

また、中心軸線７は下記数式を用いて求めることができる。

Next, the center point Q (x _q , y _q , z _q ) and the center axis 7 of the circle 70 are obtained from the detected values P1, P2, P3. The point Q can be obtained using the following mathematical formula.

The central axis 7 can be obtained using the following mathematical formula.

It is confirmed that the measured value P4 is separated from the plane P1P2P3 by a predetermined distance k2. That is, the projection component of the P4Q vector onto the direction vector of the central axis 7 is obtained.

The intersection O2 between the vertical bisector 8 of P1 and P4 and the central axis 7 is obtained using the following mathematical formula.

  Next, a flowchart of the above-described program 51p is shown in FIG. When the program 51p is started, first the first detection value P1 to the third detection value P3 are acquired (step S1). The detected values P1 to P3 can be acquired during the use of the electronic compass 1 because the user performs an operation of rotating the portable terminal 2 about the vertical axis. When step S1 ends, the process proceeds to step S2, and the central axis 7 (see FIG. 4) is calculated.

  Thereafter, the process proceeds to step S3, and the fourth detection value P4 existing at a position deviating from the plane (see FIG. 4) including the first detection value P1 to the third detection value P3 is acquired. The fourth detection value P4 is acquired by notifying the user so as to perform an operation of inverting the mobile terminal 2.

  After acquiring the fourth detection value P4, the center point O2 of the azimuth sphere 6 is calculated (step S4). In step S5, the center point of the azimuth sphere is changed from O1 (a1, b1, c1) to O2 (a2, b2, c2) (see FIG. 3). Thereafter, using the value (Xi−a2, Yi−b2, Zi−c2) obtained by correcting the measurement value P (Xi, Yi, Zi) of the triaxial magnetic sensor 3 and the above formula 2, the orientation θ of the portable terminal 2 is obtained. Is calculated and displayed on the display unit 14 (step S6).

  When the program is executed again after step S6 is completed, the corrected center point O2 is replaced with O1. Then, by executing Steps S1 to S6 again, new detection values P1 to P4 are acquired, and a new center point O2 is calculated.

The function and effect of this example will be described. In this example, the central axis 7 (see FIG. 4) of the circle 70 passing through the first detection value P1 to the third detection value P3 is calculated. Further, a vertical bisector 8 of the fourth detection value P4 existing at a position deviating from the plane including the circle 70 and any one of the first detection value P1 to the third detection value P3 is obtained. The intersection of the center axis 7 and the vertical bisector 8 is determined as the center point O 2 of the azimuth sphere 6.
In this way, since the first detection value P1, the second detection value P2, and the third detection value P3 can be acquired while the user is using the electronic compass 1, the fourth detection value P4 is acquired. Therefore, the center point O2 of the azimuth sphere 6 can be calculated only by imposing a rotation operation for the user only once. In addition, since this rotation operation is a small rotation operation that can be done by rotating it about 90 ° in one direction, it is easier to perform compared to the conventional case of rotating it around the X, Y, and Z axes. It is.

  That is, while using the electronic compass 1, the user naturally performs an operation of rotating the portable terminal 2 about the vertical axis in order to confirm the traveling direction. While this operation is performed, the first detection value P1 to the third detection value P3 are acquired, and the central axis 7 is calculated. Then, when the user performs an operation such as turning over the mobile terminal 2, the fourth detection value P4 is acquired. Thereby, the vertical bisector 8 can be calculated, and the center point of the azimuth sphere 6 can be obtained by calculating the intersection of the vertical bisector 8 and the central axis 7.

  By correcting the detection value of the three-axis magnetic sensor 3 using the center point of the azimuth sphere 6, it is possible to obtain the detection value of the geomagnetism from which the influence of the internal magnetic field is removed. As a result, the orientation of the mobile terminal 2 can be accurately obtained.

Moreover, in this example, in order to acquire the 4th detection value P4, the reverse operation alerting | reporting means 42 which alert | reports to a user so that the portable reversal operation which reverses the portable terminal 2 may be performed is provided.
If it does in this way, in order to alert | report a user to perform portable inversion operation, the 4th detection value P4 can be acquired reliably. As a result, the center O2 of the azimuth sphere 6 can be reliably calculated, and an accurate azimuth θ that eliminates the influence of the internal magnetic field of the mobile terminal 2 can be obtained.

Further, in this example, in an application utilizing the orientation function of the electronic compass 1, a horizontal rotation operation capable of detecting the first detection value P1, the second detection value P2, and the third detection value P3, and the fourth detection An automatic correction means 43 is provided that automatically calculates and corrects the center point O2 of the azimuth sphere 6 during execution of a command that performs a reversing operation or tilting operation that can detect the value P4.
The reversing operation is an operation of reversing the mobile terminal 2 by about 180 °, and the tilting operation is an operation of tilting the mobile terminal 2 by an angle smaller than that. When the user executes this command, a specific command can be given to the portable terminal. For example, when the reverse operation is performed, the screen can be zoomed or switched.
When the user uses the electronic compass 1, the horizontal rotation operation for rotating the portable terminal 2 in the horizontal direction is naturally performed, and thus the first detection value P1 to the third detection value P3 can be acquired during this time. When the user performs the reversing operation or the tilting operation, the specific command is executed, and the fourth detection value P4 is acquired together with the specific command. Then, the center point O2 of the azimuth sphere 6 is calculated and automatically corrected.
As a result, the center point O2 can be corrected without the user being aware of anything.

  As described above, according to the present invention, the center point O2 of the azimuth sphere 6 can be corrected while minimizing the rotation operation of the mobile terminal 2 performed by the user, and the influence of the internal magnetic field of the mobile terminal 2 is removed. In addition, it is possible to provide an electronic compass 1 that can calculate an accurate azimuth θ.

(Example 2)
In this example, the center point is corrected only when the detected value of geomagnetism is abnormal. As shown in FIG. 8, in this example, in step S1, the first detection value P1 (X1, Y1, Z1), the second detection value P2 (X2, Y2, Z2), the third detection value P3 (X3, Y3, After obtaining Z3), the process moves to step S1a, and the absolute value R of the geomagnetism is calculated by using the following mathematical formula.
R = √ (X1 ² + Y1 ² + Z1 ² )
Then, it is determined whether or not R is within a predetermined range. If YES is determined in this step, the process proceeds to step S1b, the azimuth θ of the portable terminal 2 is calculated using the center point O1 before correction, and the process returns to step S1. If NO is determined in step S1a, the process proceeds to step S1c, and “Please change the measurement location” is displayed. Thereafter, the detection values P1, P2, and P3 are acquired again (step S1d), the absolute value R is calculated again, and it is determined whether or not this R is within a predetermined range (step S1e). If YES is determined here, the process moves to step S1b, and the orientation θ of the portable terminal 2 is calculated and displayed using the center point O1 before correction. If it is determined No in step S1e, step S2 and subsequent steps are processed.
In addition, the same configuration as that of the first embodiment is provided.

  The function and effect of this example will be described. According to the above configuration, the center point of the azimuth sphere 6 can be corrected only when the mobile terminal 2 approaches a magnet or the like and it is determined that the detection value of the three-axis magnetic sensor 3 is abnormal. Therefore, it is not necessary to calculate or correct the center point of the azimuth sphere 6 when the detected value is normal.

(Example 3)
In this example, the program 51p is changed. As shown in FIG. 9, after calculating the center point O2 in step S4, the process moves to step S5a to determine which of the old center point O1 and the new center point O2 is better. From the coordinates (a1, b1, c1) of the old center point O1 and the coordinates (a2, b2, c2) of the new center point O2, the geomagnetic absolute values R1 and R2 (see FIG. 3) are calculated using the following formula. The calculation is performed for a plurality of detection values P (Xi, Yi, Zi) other than the first detection value P1 to the fourth detection value P4.
R1 = √ ((Xi−a1) ² + (Yi−b1) ² + (Zi−c1) ² )
R2 = √ ((Xi−a2) ² + (Yi−b2) ² + (Zi−c2) ² )
Then, a difference ΔR1 between the maximum value R1 _max and the minimum value R1 _min of R1 is calculated. Further, the difference ΔR2 between the maximum value R2 _max and the minimum value R2 _min of R2 is obtained. If ΔR2 is smaller than ΔR1, it is determined that the new center point O2 is better (improved), and the process moves to step S5c. The center point of the azimuth sphere is set to O2. If R2> R1, it is determined that the old center point O1 is better (not improved), and the process moves to step S5b to set the center point of the azimuth sphere to O1.

  If the new center point O2 is improved compared to the old center point O1, the variation in R2 becomes smaller than R1, so that ΔR1> ΔR2 (see FIG. 3). In this example, R1 and R2 are calculated for, for example, about five measurement values P (Xi, Yi, Zi), and ΔR1 and ΔR2 are obtained from the maximum and minimum values. In calculating R1 and R2, the first detection value P1, the second detection value P2, the third detection value P3, and the fourth detection value P4 are excluded from the central points of these detection values P1 to P4. This is because when O2 is used and R2 is calculated using P1 to P4, R2 = 0.

  The center point O1 before correction is more accurate, and it may be assumed that the detection of the geomagnetism becomes inaccurate due to correction, but this problem can be prevented by adopting the above configuration.

そして、伏角αが所定範囲内であるか否かを判断する。ここでＹｅｓと判断された場合はステップＳ１ｂを処理し、その後ステップＳ１’に戻る。また、ステップＳ１ａ’でＮｏと判断された場合は、ステップＳ２以降を処理する。 Example 4
In this example, steps S1 and S1a of the program 51p are changed. As shown in FIG. 10, in this example, in step S1 ′, the detected value P (Mx, My, Mz) of the geomagnetism by the triaxial magnetic sensor 3 and the detected value G (Gx of the gravitational acceleration by the triaxial acceleration sensor 17 are displayed. , Gy, Gz). Thereafter, the process proceeds to step S1a ′, and the dip angle α is calculated using the following mathematical formula.

Then, it is determined whether or not the depression angle α is within a predetermined range. If YES is determined here, step S1b is processed, and then the process returns to step S1 ′. On the other hand, if it is determined No in step S1a ′, step S2 and subsequent steps are processed.

  In this way, the center point of the azimuth sphere 6 can be corrected only when the portable terminal 2 approaches, for example, a magnet or the like, and the geomagnetic dip angle α is determined to be abnormal. Therefore, there is no need to calculate or correct the center point of the azimuth sphere 6 when the depression angle α is normal.

(Experimental example 1)
An experimental example of the electronic compass 1 according to the present invention will be shown. First, the following compass was prepared.
Azimuth meter 3-axis magnetic sensor 3 (magnetic measurement resolution 3 mG, linearity 0.3% / full scale X, Y, and Z axes are placed in the right hand system Measurement range 3G A / D conversion 12 bits Measurement time 1 millisecond With a measurement interval of 40 milliseconds).
A mobile phone equipped with this compass and incorporating the program 51p was created.
The mobile phone has a distribution of an internal magnetic field of ± 5000 mG, and an azimuth meter is installed at a location of 100 mG.
Experimental results There was an initial origin abnormality (500, 500, 500 mG), and the compass did not function. In addition, the user was informed of the abnormality in red. As a result of the user flipping back in the roll direction, the origin was (20, 10, 20 mG), and the compass functioned normally.
This point was confirmed.

(Experimental example 2)
The normal state was continuously displayed in blue for each measurement using the compass and the mobile phone of Experimental Example 1. When the roll is rotated or tilted, it is displayed in sound or green. As a result of comparing the recalculation results (10, 10 and 20 mG) with the conventional origin, a better value was obtained, so the remeasured value was taken as the new origin.

(Experimental example 3)
When the magnet was brought close to the compass using the compass and the mobile phone of Experimental Example 1, the absolute value of the magnetic field measurement was 2050 mG with respect to the absolute value of the geomagnetism of 470 mG, and the red color was displayed to the user. Please change the measurement location. " When moving to another place away from the magnet, the red display disappeared quickly.

(Experimental example 4)
When the powerful magnet was brought close to the compass in the compass and the mobile phone of Experimental Example 1, the absolute value of the magnetic field measurement was 3000 mG or more. This abnormality was displayed in red as "Please change the measurement location" to the user. When moving to another location away from the magnet, a red display remained. When rotating, the compass did not function without commanding rotation. Therefore, when the roll reversal operation was performed, the red color disappeared, and the compass returned to normal operation.

DESCRIPTION OF SYMBOLS 1 Electronic compass 2 Mobile terminal 3 3-axis magnetic sensor 4 Microcomputer 40 Center point correction means 41 Direction calculation means 42 Inversion operation notification means 43 Automatic correction means 44 Abnormality determination means 45 Improvement determination means 6 Azimuth sphere 7 Center axis 8 Vertical bisection Surface 80 Intermediate point O1 (before correction) center point O2 (after correction) center point

Claims (5)

An electronic compass that is provided in a mobile terminal and detects an orientation in which the mobile terminal faces while correcting the influence of the internal magnetic field of the mobile terminal,
A three-axis magnetic sensor that is fixed to the portable terminal and that detects the geomagnetism intensity in the three-axis directions of the X axis, the Y axis, and the Z axis that are orthogonal to each other;
The detected value (Xi, Yi, Zi) of the geomagnetism by the three-axis magnetic sensor calculates the center point of the azimuth sphere drawn with the attitude change of the mobile terminal, and the center point after the calculation is the center after the calculation Center point correction means for correcting the point;
Azimuth calculating means for correcting the detected value of the geomagnetism by the three-axis magnetic sensor using the corrected coordinates of the center point and calculating the azimuth of the portable terminal using the corrected detected value; With
The center point correcting means calculates a center axis of a circle including the first detection value, the second detection value, and the third detection value detected by the three-axis magnetic sensor, and the first detection value , Passing through an intermediate point of a straight line connecting one detection value of the second detection value and the third detection value and the fourth detection value existing at a position off the plane including the circle. , The intersection of the perpendicular bisector perpendicular to the straight line and the central axis is calculated as the center point of the azimuth sphere ,
The first detection value, the second detection value, and the third detection value are acquired while the operation of confirming the azimuth is performed by the user of the mobile terminal, and the first detection value is further acquired for the user. 4. An electronic compass comprising reversing operation notifying means for notifying that a mobile reversing operation for reversing the mobile terminal is performed in order to obtain a detected value .   An electronic compass that is provided in a mobile terminal and detects an orientation in which the mobile terminal faces while correcting the influence of the internal magnetic field of the mobile terminal,
  A three-axis magnetic sensor that is fixed to the portable terminal and that detects the geomagnetism intensity in the three-axis directions of the X axis, the Y axis, and the Z axis that are orthogonal to each other;
  The detected value (Xi, Yi, Zi) of the geomagnetism by the three-axis magnetic sensor calculates the center point of the azimuth sphere drawn with the attitude change of the mobile terminal, and the center point after the calculation is the center after the calculation Center point correction means for correcting the point;
  Azimuth calculating means for correcting the detected value of the geomagnetism by the three-axis magnetic sensor using the corrected coordinates of the center point and calculating the azimuth of the portable terminal using the corrected detected value; With
  The center point correcting means calculates a center axis of a circle including the first detection value, the second detection value, and the third detection value detected by the three-axis magnetic sensor, and the first detection value , Passing through an intermediate point of a straight line connecting one detection value of the second detection value and the third detection value and the fourth detection value existing at a position off the plane including the circle. , The intersection of the perpendicular bisector perpendicular to the straight line and the central axis is calculated as the center point of the azimuth sphere,
  In an application utilizing the direction function of the electronic compass, a horizontal rotation operation capable of detecting the first detection value, the second detection value, and the third detection value, and the fourth detection value can be detected. An electronic compass comprising automatic correction means for automatically calculating and correcting the center point of the azimuth sphere during execution of a command for performing a reversing operation or a tilting operation.   In Claim 1 or Claim 2, the absolute value R of the geomagnetism is calculated from the detected value (Xi, Yi, Zi) by using the following formula:
R = √ (Xi ² + Yi ² + Zi ² )
  An abnormality determining means for determining whether or not the R is within a predetermined range, and when the R is determined not to be within the predetermined range by the abnormality determining means, the center point correcting means An electronic compass characterized by correction.   In claim 3, when the newly calculated center point is (a2, b2, c2) and the center point before calculation is (a1, b1, c1),
R1 = √ ((Xi−a1) ² + (Yi-b1) ² + (Zi-c1) ² )
R2 = √ ((Xi−a2) ² + (Yi-b2) ² + (Zi-c2) ² )
Are used to calculate absolute values R1 and R2 of geomagnetism for a plurality of detection values (Xi, Yi, Zi) other than the first detection value to the fourth detection value, and the maximum value R1 of R1 is calculated. _max And the minimum value R1 _min Difference ΔR1 and the maximum value R2 of R2 _max And the minimum value R2 _min An improvement determining means for determining whether or not ΔR2 is smaller than ΔR1, and when the improvement determining means determines that ΔR2 is smaller than ΔR1, the center point is An electronic compass characterized by correcting from (a1, b1, c1) to (a2, b2, c2).   In any 1 paragraph of Claims 1-4, A triaxial acceleration sensor which detects each intensity of gravity acceleration in the above-mentioned triaxial direction is provided,
  A depression angle abnormality determining means for calculating a depression angle of the geomagnetism from a detection value of the three-axis acceleration sensor and a detection value of the three-axis magnetic sensor and determining whether the depression angle is within a predetermined range; An electronic compass characterized by correcting the center point when the dip angle abnormality determining means determines that the dip angle is not within the predetermined range.

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