JP2011252808A - Magnetism detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform calibration processing for obtaining a reference original point of a spherical coordinate with a small operation amount concerning a magnetism detection device using three axial sensors for detecting geomagnetism.SOLUTION: Coordinate point data Di(xi, yi, zi) of geomagnetic vectors are obtained based on detection outputs from three geomagnetic sensors. The coordinate point data are positioned on a non-spherical coordinate Ga having a center Oc(xc, yc, zc) at an off-set position separated from the original point O of a three-dimensional detection coordinate and also having a distortion with the size of detection error coefficients a, b, c. Then, a temporary spherical coordinate G1, which has the center Oc and has an minimum error compared with a plurality of the coordinate point data Di, is obtained by calculation, so as to specify coordinate points xc, yc, zc. The detection error coefficients a, b, c are not obtained by calculation but selected from the prepared combinations of numerals as the ones with the smallest error.

Description

  The present invention relates to a magnetic detection device in which a magnetic vector detected by a magnetic sensor is obtained as coordinate point data on spherical coordinates, and in particular, calibration processing for obtaining a reference of coordinate point data is performed with a minimum of arithmetic processing. The present invention relates to a magnetic detection device capable of performing the above.

  A magnetic detection device using magnetic sensors arranged on three axes is used as an azimuth sensor or an angular velocity sensor that detects geomagnetism. When a magnetic field intensity such as geomagnetism is detected by a magnetic sensor arranged toward the X axis, the Y axis, and the Z axis that are orthogonal to each other, the magnetic detection device converts a magnetic vector into a three-dimensional detection coordinate based on the detection output. Recognized as the upper coordinate point.

  In this type of magnetic detection device, when the power is turned on, it is unclear at which position on the three-dimensional detection coordinates the magnetic vector appears due to the presence of an offset magnetic field and the influence of external magnetic noise. Therefore, it is necessary to perform calibration processing to convert the detected coordinate point data into data on three-dimensional detection coordinates centered on a predetermined origin.

  In the following Patent Document 1, it is pointed out that the azimuth data obtained by detecting geomagnetism with a magnetic detection device appears on a coordinate system that approximates an ellipse. Describes the compensation by converting to an ideal circular ring.

  In Patent Document 2 below, as a method for obtaining a reference origin on a three-dimensional detection coordinate with a small amount of data, three coordinate point data are obtained when a plurality of geomagnetic vectors are detected and three coordinate point data are obtained. An invention is disclosed in which an equidistant point is obtained from the reference point and this point is used as a reference origin.

Japanese translation of PCT publication No. 7-507874 JP 2007-163389 A

  In the calibration process shown in Patent Document 1, since there are many unknowns to be obtained by the calculation process, it takes time for the calculation and it is difficult to perform an accurate calibration process.

  The calibration process described in Patent Document 2 is easy to calculate, but since the reference origin is obtained from a small number of data, there is a high possibility that the error of the reference origin after the calculation will increase.

  SUMMARY OF THE INVENTION The present invention solves the above-described conventional problems, and an object of the present invention is to provide a magnetic detection device capable of performing a highly accurate calibration process with a minimum of arithmetic processing.

The present invention includes a magnetic detection unit and a calculation unit having a magnetic sensor for detecting magnetic field strength in three orthogonal directions, and the calculation unit includes:
(A) From the detected value of the magnetic field strength in the three axis directions, the direction of the magnetic vector is obtained as coordinate point data on the three-dimensional detection coordinates,
(B) When a plurality of coordinate point data is obtained, a provisional spherical coordinate that minimizes an error from the plurality of coordinate point data and a coordinate of the center of the provisional spherical coordinate on the three-dimensional detection coordinates are obtained,
(C) A plurality of combinations of detection error coefficients a, b, and c in the three-axis directions, each of which is a constant, are set in advance, and coincide with the center of the provisional spherical coordinate and have a plurality of sets of detection error coefficients a, b. Among the plurality of aspherical coordinates obtained by applying any one of, c, the one having the smallest error from the plurality of coordinate point data is specified as the aspherical coordinate where the coordinate point data is located. Is.

Furthermore, the present invention provides
(D) The correction of the coordinate point data on the corrected spherical coordinate from the detection error coefficients a, b, c of the aspherical coordinate with the least error from a plurality of coordinate point data and the coordinates of the center of the provisional spherical coordinate. It is converted into coordinate point data.

  The coordinate point data obtained from the detection output of the magnetic detection unit has a center at a position away from the origin of the three-dimensional detection coordinates, and the detection error coefficients a, b, c for the X axis, the Y axis, and the Z axis, respectively. Appears as points on aspherical coordinates such as ellipsoidal spheres and ellipsoids. Therefore, unless the offset distance from the origin of the three-dimensional detection coordinates to the center of the aspherical coordinates and the detection error coefficients a, b, and c are obtained, the direction and motion of the magnetic vector cannot be accurately grasped. Therefore, when a plurality of coordinate point data is obtained, it is necessary to obtain an error between the coordinate surface on which the coordinate point data appears and the aspherical coordinates.

  Therefore, assuming that the coordinate point data appears in the provisional spherical coordinates, only the offset distance from the origin of the three-dimensional detection coordinates to the center of the aspherical coordinates among the unknowns is obtained, and the detection error coefficients a, b, and c are determined. Finds the smallest combination of a plurality of constants set in advance with the smallest error from the actual coordinate plane. Thereby, a highly accurate calibration process can be performed with the minimum number of operations.

  In the present invention, the equation of the provisional spherical coordinate in (b) is expressed by Equation 1. Further, the equation of the aspherical coordinate in (c) is expressed by Equation 2. However, xc, yc, zc are the coordinates of the center of the provisional spherical coordinates on the three-dimensional detection coordinates.

  In the present invention, the direction of the magnetic vector can be obtained from the corrected coordinate point data on the corrected spherical coordinate. Alternatively, the rotation angle of the magnetic detection unit can be obtained from the opening angle of a plurality of correction coordinate point data with respect to the center of the correction spherical coordinate, and the opening of the plurality of correction coordinate point data with respect to the center of the correction spherical coordinate can be obtained. The angular velocity of the magnetic detection unit can be obtained from the angle and the time when the plurality of correction coordinate data are obtained.

  The present invention calculates only the offset distance from the origin of the three-dimensional detection coordinates among the unknowns to be calculated by the calibration processing, and the three-axis detection error coefficients a, b, and c are determined from predetermined constants. select.

  For this reason, the number of unknowns to be obtained by calculation is reduced, and calculation processing in the calculation unit can be performed in a short time.

The circuit block diagram of the magnetic detection apparatus of embodiment of this invention, Explanatory drawing showing the processing operation of the data buffer, Explanatory drawing of the X-axis sensor, Y-axis sensor, and Z-axis sensor provided in the magnetic detection unit An explanatory diagram showing aspherical coordinates, provisional spherical coordinates and coordinate point data on the three-dimensional detection coordinates, Explanatory drawing showing the calculation of the dip angle, Explanatory drawing which shows the correction spherical coordinate and correction coordinate point data which have a center in the origin of a three-dimensional detection coordinate,

  A magnetic detection device 1 according to an embodiment of the present invention shown in FIG. 1 is mainly used as an orientation sensor, and includes a geomagnetic detection unit 2 and a three-axis acceleration sensor 8.

  As shown in FIG. 3, in the magnetic detection device 1, the X1, Y1, and Z1 axes, which are reference axes orthogonal to each other, are determined as fixed axes. Three-dimensional detection coordinates are determined by the X1 axis, the Y1 axis, and the Z1 axis. The magnetic detection device 1 is mounted on a portable device or the like, and can freely move in space while maintaining the orthogonal relationship between the X1 axis, the Y1 axis, and the Z1 axis of the three-dimensional detection coordinates.

  As shown in FIG. 3, the X-axis sensor 3 is fixed along the X1 axis, the Y-axis sensor 4 is fixed along the Y1 axis, and the Z-axis sensor is fixed along the Z1 axis. Has been. The X-axis sensor 3, the Y-axis sensor 4, and the Z-axis sensor 5 are all configured by GMR elements (giant magnetoresistance effect elements). The GMR element is composed of a pinned magnetic layer and a free magnetic layer made of a soft magnetic material such as a Ni—Co alloy or a Ni—Fe alloy, and a nonmagnetic material such as copper sandwiched between the pinned magnetic layer and the free magnetic layer. And a conductive layer. An antiferromagnetic layer is laminated below the pinned magnetic layer, and the magnetization of the pinned magnetic layer is pinned by exchange coupling between the antiferromagnetic layer and the pinned magnetic layer.

  The X-axis sensor 3 detects a component of the geomagnetic vector facing the X1 direction, and the magnetization direction of the pinned magnetic layer is fixed in the PX direction along the X1 axis. The direction of magnetization of the free magnetic layer responds to the direction of geomagnetism. When the magnetization direction of the free magnetic layer is parallel to the PX direction, the resistance value of the X-axis sensor 3 is minimized, and when the magnetization direction of the free magnetic layer is opposite to the PX direction, the resistance value of the X-axis sensor 3 is maximized. become. Further, when the magnetization direction of the free magnetic layer is orthogonal to the PX direction, the resistance value is an average value of the maximum value and the minimum value.

  In the magnetic field data detection unit 6 shown in FIG. 1, the X-axis sensor 3 and the fixed resistance are connected in series, and a voltage is applied to the series circuit of the X-axis sensor 3 and the fixed resistance. The voltage between the resistors is taken out as the detection output of the X1 axis. When a magnetic field directed in the X1 direction is not applied to the X-axis sensor 3, or when a magnetic field orthogonal to PX is applied, the detection output of the X1-axis becomes a midpoint potential.

  When the entire geomagnetism detector 2 is tilted and the fixed direction PX of the magnetization of the pinned magnetic layer of the X-axis sensor 3 is set to the same direction as the geomagnetic vector V, the magnetic field component applied to the X-axis sensor 3 becomes a maximum value. The detected output of the X1 axis at this time becomes a maximum value on the plus side with respect to the midpoint potential. Conversely, when the fixed direction PX of the magnetization of the fixed magnetic layer of the X-axis sensor 3 is directed opposite to the geomagnetic vector V, the reverse magnetic field component applied to the X-axis sensor 3 has a maximum value. At this time, the detection output of the X1 axis has a maximum value on the minus side with respect to the midpoint potential.

  Each of the Y-axis sensor 4 and the Z-axis sensor 5 is also connected to a fixed resistor in series, and a voltage is applied to the Y-axis sensor 4 or a series circuit of the Z-axis sensor 5 and the fixed resistor. Is taken out as a detection output of the Y1 axis or the Z1 axis.

  When the fixed direction PY of the magnetization of the fixed magnetic layer of the Y-axis sensor 4 is set in the same direction as the geomagnetic vector V, the Y1-axis detection output has a maximum value on the plus side with respect to the midpoint potential. If the fixed direction PY of the magnetization of the fixed magnetic layer of the Y-axis sensor 4 is directed opposite to the geomagnetic vector V, the Y1-axis detection output becomes a maximum value on the minus side with respect to the midpoint potential. Similarly, when the fixed direction PZ of the magnetization of the fixed magnetic layer of the Z-axis sensor 5 is set to the same direction as the geomagnetic vector V, the detection output of the Z1-axis becomes a maximum value on the plus side with respect to the midpoint potential. When the pinned direction PY of the magnetization of the pinned magnetic layer of the Z-axis sensor 5 is directed opposite to the geomagnetic vector V, the detection output of the Z1-axis becomes a maximum value on the minus side with respect to the midpoint potential.

  If the magnitude of the geomagnetic vector V is constant, the detection outputs from the X-axis sensor 3, the Y-axis sensor 4, and the Z-axis sensor 5 are all of the absolute value of the plus side maximum value and the minus side maximum value. The absolute value is the same.

  As the X-axis sensor 3, a positive detection output and a negative detection output are obtained depending on the direction of the geomagnetic vector, and the absolute value is the same between the maximum value of the positive detection output and the maximum value of the negative detection output. If it becomes, it can also be comprised with geomagnetic sensors other than a GMR element. For example, a Hall element or MR element that can detect only the positive magnetic field intensity along the X1 axis and a Hall element or MR element that can detect only the negative magnetic field intensity may be combined and used as the X-axis sensor 3. Good. The same applies to the Y-axis sensor 4 and the Z-axis sensor 5.

  As shown in FIG. 1, the detection outputs of the X axis, the Y axis, and the Z axis detected by the magnetic field data detection unit 6 are given to the calculation unit 10. The arithmetic unit 10 includes an A / D converter, a CPU, a clock circuit, and the like. According to the measurement time of the clock circuit of the calculation unit 10, the detection outputs of the X axis, the Y axis, and the Z axis detected by the magnetic field data detection unit 6 are intermittently sampled in a short cycle and read out to the calculation unit 10. . Each detection output is converted into a digital value by the A / D conversion unit provided in the calculation unit.

  A memory 7 is connected to the CPU constituting the arithmetic unit 10. In the memory 7, software for arithmetic processing is programmed and stored. The arithmetic processing of the arithmetic unit 10 is executed by the software.

  The arithmetic unit 10 performs arithmetic processing based on software. The X1 axis detection output, the Y1 axis detection output, and the Z1 axis detection output converted into digital data are subjected to calculation processing by the calculation unit 10, and the coordinates on the three-dimensional detection coordinates of X1-Y1-Z1 shown in FIG. It is converted into point data Di (xi, yi, zi) and stored in the data buffer (buffer memory) 11 shown in FIG. 2 (i is an integer from 1 to N, which is the same hereinafter). . The coordinate point data Di sampled and calculated in a short cycle in synchronization with the clock circuit is given to the storage unit 11a of the data buffer 11. Each time the coordinate point data Di is given to the storage unit 11a, the coordinate point data Di obtained before that is sequentially sent from the storage unit 11a to 11m, and the coordinate point data Di of the storage unit 11m at the final stage is discarded. While the magnetic detection device 1 is operating, the latest data is continuously read from the magnetic field data detection unit 6 at regular intervals, and the coordinate point data Di after calculation is sequentially stored in the data buffer 11.

  As shown in FIG. 1, the magnetic detection device 1 is provided with a triaxial acceleration sensor 8. The triaxial acceleration sensor 8 detects accelerations in directions along the X1 axis, the Y1 axis, and the Z1 axis, and the detection output is given to the posture detection unit 9. In the posture detection unit 9, the gravitational acceleration vector A shown in FIG. 5 is calculated from the accelerations in the directions along the X1 axis, the Y1 axis, and the Z1 axis, and the information is given to the calculation unit 10.

  As shown in FIG. 4, when the geomagnetism detection unit 2 is placed anywhere on the earth, the detection output xi is obtained from the X-axis sensor 3 of the geomagnetism detection unit 2, and the detection output yi is obtained from the Y-axis sensor 4. Thus, a detection output zi is obtained from the Z-axis sensor 5. In the calculation unit 10 shown in FIG. 1, coordinate point data Di (xi, yi) indicating the direction of the geomagnetic vector V on the three-dimensional detection coordinates of the X1-Y1-Z1 axes from the detection outputs xi, yi, zi of the respective axes. , Zi) is calculated.

  When the measurement location is the northern hemisphere, the geomagnetic vector V is incident at a predetermined dip angle toward the horizon. As shown in FIG. 4, in the three-dimensional detection coordinates having the X1-Y1-Z1 axes, the geomagnetic vector V faces the center Oc of the aspherical coordinate Ga before calibration, and the orientation of the geomagnetic vector V is the aspherical coordinate Ga. It is expressed as the upper coordinate point data Di (xi, yi, zi).

  As shown in FIG. 4, immediately after the power is turned on and the detection of geomagnetism is started, the center Oc of the aspherical coordinate Ga in which the coordinate point data Di (xi, yi, zi) appears is the origin O of the three-dimensional detection coordinate. The distance between the center Oc and the origin O is an offset amount when the magnetic field strength of the geomagnetism is detected by the X-axis sensor 3, the Y-axis sensor 4, and the Z-axis sensor 5.

  The origin O of the three-dimensional detection coordinates X1-Y1-Z1 is the origin to which the geomagnetic vector V is directed when there is no magnetic noise or the like, and only the geomagnetism can be detected purely by the sensors 3, 4 and 5. However, there are other electronic circuits that generate magnetic noise in the housings of various electronic devices in which the magnetic detection device 1 is built. In an environment in which geomagnetism is to be detected, there are magnets nearby or large magnetic materials such as steel frames, which also cause magnetic noise. When a bias magnetic field caused by magnetic noise or the like acts on each of the sensors 3, 4, 5, as shown in FIG. 4, the center Oc toward the geomagnetic vector V exists at a position away from the origin O of the three-dimensional detection coordinates. It becomes like this.

  Further, when detecting the geomagnetism, the sensitivities of the X-axis sensor 3, the Y-axis sensor 4, and the Z-axis sensor 5 match, and the magnetic field data detection unit 6 detects the magnetic fields of the X-axis, Y-axis, and Z-axis. When the circuit characteristics match and there is no magnetic material nearby, the coordinate point data Di (xi, yi, zi) indicating the direction of the geomagnetic vector V has a true spherical shape having the center Oc. Appears on spherical coordinates. However, in reality, there is a difference in the sensitivity of the sensor when detecting the geomagnetic intensity on the X axis, the Y axis, and the Z axis, and the circuit of the magnetic field data detection unit 6 also has variations in characteristics. Furthermore, even if there is a magnetic sheet for absorbing noise in the vicinity of the geomagnetism detection unit 2, there is an error in the detection output of the X axis, the Y axis, and the Z axis depending on the environment in which the geomagnetism detection unit 2 is installed. Occurs.

  In FIG. 4, the detection error coefficient for the X axis is indicated by a, the detection error coefficient for the Y axis is indicated by b, and the detection error coefficient for the Z axis is indicated by c. The three-dimensional shape of the aspherical coordinates Ga changes according to the detection error coefficients a, b, and c as shown in Equation 3 below. Unless the detection error coefficients a, b, and c of the X axis, the Y axis, and the Z axis coincide with each other, the aspherical coordinate Ga does not become a true spherical surface but an elliptical sphere or an oval sphere. The detection error coefficients a, b, and c are generated due to the above-described various magnetic noises when the geomagnetism measurement is started, and the detection error coefficients a, b, and c start the geomagnetism measurement. It is different every time it is done, and also varies in the environment where the geomagnetism detector 2 is used.

  Therefore, when the power is turned on and the detection operation is disclosed, the coordinate point data Di (xi, yi, zi) appears on the surface of the aspherical coordinate Ga. The coordinates (xc, yc, zc) are unknown, and the shape of the aspherical coordinates Ga is also unknown.

Therefore, the arithmetic unit 10 obtains a plurality of coordinate point data Di (xi, yi, zi) and sequentially stores them in the data buffer 11 shown in FIG. xc, yc, zc) is obtained, and a calibration process for obtaining the shape of the aspherical coordinate Ga is performed.
The equation of the aspherical coordinate Ga before calibration is as shown in Equation 3 below.

  The calibration process is performed in order to obtain the values of xc, yc, zc and a, b, c in Equation 3. If a plurality of obtained coordinate point data Di (xi, yi, zi) are not varied and each coordinate point data Di appears on the same aspherical coordinate Ga, a plurality of obtained xi, yi, zi (i = 1). , 2, 3, 4,...) Are substituted for x, y, z in Equation 3, and the simultaneous equations are solved to obtain the values of xc, yc, zc and a, b, c. be able to.

  However, actually, there is a variation in each coordinate point data Di (xi, yi, zi), and it does not always appear on the surface of the same aspherical coordinate Ga. Therefore, by substituting xi, yi, zi of the plurality of coordinate point data Di into x, y, z of the equation (3), an elliptic sphere having the smallest error from the plurality of coordinate point data Di is obtained by the least square method. By determining, xc, yc, zc and a, b, c of the equation shown in Equation 3 are determined. However, in this calculation method, since six unknowns xc, yc, zc and a, b, c must be obtained, the amount of calculation becomes very large.

  Therefore, in the following calibration process, only three unknowns xc, yc, and zc are obtained by calculation using the least square method. For a, b, and c, a combination of a plurality of numbers is prepared in advance, and the shape of the aspheric surface (a, b, c) that is most approximate to the variation of the actual coordinate point data Di (xi, yi, zi) is prepared. Instead of calculating the value), a method of selecting from a predetermined combination of numbers a, b, and c is used.

  First, in order to calculate an unknown amount of offset amounts xc, yc, zc, as shown in FIG. 4, a geometrically accurate sphere having a radius R sharing the same center Oc as the aspherical coordinates Ga is used. Assuming the provisional spherical coordinate G1, the provisional spherical coordinate G1 having the smallest error from a plurality of coordinate point data Di (xi, yi, zi) is obtained by calculation. The equation of the provisional spherical coordinate G1 is as shown in Equation 4 below, and there are only four unknowns xc, yc, zc and radius R to be obtained by calculation, and include detection error coefficients a, b, c. Absent. Since it is not necessary to calculate the detection error coefficients a, b, and c, the amount of calculation can be reduced.

  In the calculation process of the calculation unit 10, the equation of the provisional spherical coordinate G1 of Expression 4 is represented by Fi as described in Expression 5 below, and further obtained for each of a plurality of coordinate point data Di (xi, yi, zi). J is obtained by squaring Fi to be squared and a value obtained by cumulative addition. Obtaining xc, yc, zc, and R that minimizes J is obtained by calculating the equation of provisional spherical coordinate G1 that minimizes an error from a plurality of obtained coordinate point data Di (xi, yi, zi). Is equivalent to

  In order to obtain xc, yc, zc and R when J is minimum, as shown in the following Equation 6, a value obtained by partially differentiating J by the unknowns of xc, yc, zc and R is 0. Find simultaneous equations. By solving these simultaneous equations, xc, yc, zc and R when J is minimized can be obtained.

ただし、

However,

である。

It is.

  Since Equation 6 is a nonlinear simultaneous equation, it cannot be solved by a general solution, but can be solved by performing iterative calculation by a numerical solution method such as the Gauss-Newton method.

  However, it is also possible to obtain the values of xc, yc, zc, and R after transforming Fi in Formula 5 into the linear equation shown in Formula 8 below without using the above iterative calculation.

  The unknown numbers a1, a2, and a3 and the unknown number equation a4 in Formula 8 are as shown in Formula 9 below.

  Therefore, when the simultaneous equations equivalent to the simultaneous equations shown in Equation 6 are expressed using Equation 8, the following Equations 10 are obtained.

  When Expression 10 is expressed by a determinant, the following Expression 11 is obtained.

  Since the determinant is a linear simultaneous equation including unknown numbers a1, a2, a3, and a4, it can be solved by numerical analysis such as Gaussian elimination. In this numerical analysis, it is not necessary to perform iterative calculation as in the case of solving the nonlinear equation shown in Equation 6, so that a solution can be obtained in a relatively short time in a CPU or the like.

  By solving the unknown numbers a1, a2, a3, and a4, xc, yc, zc, and R can be obtained as shown in the following formula 12.

  Next, the detection error coefficients a, b, and c are held in the memory in the calculation unit 10 as data of a combination of a plurality of numbers. Xc, yc, zc obtained by the above calculation is substituted into an elliptic sphere equation shown in Equation 3, and any one of a plurality of combinations of detection error coefficients a, b, c determined as constants in advance is used. By substituting this into the equation of Equation 3, various shapes of elliptic spheres having the center Oc at the coordinate point (xc, yc, zc) shown in FIG. 4 can be set.

  A plurality of combinations of numbers of the detection error coefficients a, b, and c are based on measured values of characteristics of the X-axis sensor 3, the Y-axis sensor 4, and the Z-axis sensor 5, or of an electronic device in which the magnetic detection device 1 is mounted. Assuming the range of distortion of spherical coordinates that will occur in advance according to other electronic circuits and magnetic shields arranged inside the case, predict the shape of many elliptical spheres that fall within that range. Can be decided.

  Then, the errors of the plurality of coordinate point data Di (xi, yi, zi) obtained so far and the ellipsoidal spheres having a plurality of shapes are obtained by the least square method, etc. The point data Di (xi, yi, zi) is selected and specified as the aspherical coordinate Ga on which the point data Di (xi, yi, zi) appears.

  The calibration process is performed when the power is turned on and the magnetic detection apparatus 1 is started, and then a predetermined number of coordinate point data Di (xi, yi, zi) is obtained. Or it is performed regularly.

  When the elliptical sphere having the center Oc at the coordinate point (xc, yc, zc) shown in FIG. 4 is specified as the aspherical coordinate Ga by the calibration process, the specified coordinate value xc, yc, zc and the specified coordinate value are specified. The detected error coefficients a, b, and c are held as constants in the memory of the arithmetic unit 10. Then, the coordinate point data Di (xi, yi, zi) obtained after the calibration process is substituted into the equation 13 to obtain corrected coordinate point data Di ′ (xi ′, yi ′, zi ′). It is done.

  That is, as shown in FIG. 6, the coordinate point data Di (xi, yi, zi) has a center at the origin O of the three-dimensional detection coordinates, and a true value obtained by correcting distortion caused by the detection error coefficients a, b, c. It can be converted into corrected coordinate point data Di ′ (xi ′, yi ′, zi ′) on the corrected spherical coordinate G0 having a spherical shape.

(Equation 13)
xi ′ = a · (xi−xc)
yi '= b. (yi-yc)
zi ′ = c · (zi−zc)

  Since the center of the corrected spherical coordinate G0 coincides with the origin O of the three-dimensional detection coordinates of the X1-Y1-Z1 axes, the corrected coordinate point data Di ′ (xi ′, yi ′, zi) appearing in the corrected spherical coordinate G0. ′) And the detection output of the triaxial acceleration sensor 8 shown in FIG. 1, the dip angle I of the geomagnetic vector can be obtained.

  FIG. 5 shows a gravitational acceleration vector A detected by the triaxial acceleration sensor 8. In addition, M represents the geomagnetic vector obtained from the corrected coordinate point data Di ′ (xi ′, yi ′, zi ′) when the magnetic detection device 1 is stopped in the same posture in space.

  As shown in the following Equation 13, the relative angle α of both vectors can be obtained from the inner product of the gravitational acceleration vector A and the geomagnetic vector M at rest, and by subtracting 90 degrees from α, the geomagnetic vector M The dip angle I can be obtained.

  FIG. 6 shows the three-dimensional correction coordinates of the X0-Y0-Z0 axis corrected so that the gravitational acceleration vector A is directed to the negative of the Z axis. In the three-dimensional correction coordinates, the X0-Y0 plane coincides with the direction of the horizontal plane. When the measurement location is the northern hemisphere, the geomagnetic vector M is shown in an orientation having an angle I (positive angle) I on the plus side from the X0-Y0 plane.

  Further, by projecting the geomagnetic vector M onto the reference horizontal plane H0 passing through the equator of the three-dimensional correction coordinates, the azimuth angle β indicating the attitude of the geomagnetic detection device 1 on the earth can be obtained.

  When the magnetic detection device 1 is mounted on a portable device, when the magnetic detection device 1 is rotated, the corrected coordinate point data Di ′ (xi ′, yi ′, zi ′) moves on the corrected spherical coordinate G0. . By measuring the movement trajectory, the rotation direction and rotation angle of the portable device can be known. Further, the angular velocity of the portable device can be obtained from the opening angle of the plurality of correction coordinate point data Di ′ (xi ′, yi ′, zi ′) with respect to the origin O and the sampling time when the data is obtained.

DESCRIPTION OF SYMBOLS 1 Magnetic detection apparatus 2 Geomagnetic detection part 3 X-axis sensor 4 Y-axis sensor 5 Z-axis sensor 6 Magnetic field data detection part 7 Memory 10 Calculation part 8 3-axis acceleration sensor 11 Data buffer Ga Aspherical coordinate G1 Provisional spherical coordinate G0 Correction spherical coordinate X1-Y1-Z1 Three-dimensional detection coordinates X0-Y0-Z0 Three-dimensional correction coordinates Di Coordinate point data Di 'Correction coordinate point data a, b, c Detection error coefficients xc, yc, zc Center coordinates of aspherical coordinates

Claims (7)

A magnetic detection unit and a calculation unit having a magnetic sensor for detecting magnetic field strength in three orthogonal directions perpendicular to each other;
(A) From the detected value of the magnetic field strength in the three axis directions, the direction of the magnetic vector is obtained as coordinate point data on the three-dimensional detection coordinates,
(B) When a plurality of coordinate point data is obtained, a provisional spherical coordinate that minimizes an error from the plurality of coordinate point data and a coordinate of the center of the provisional spherical coordinate on the three-dimensional detection coordinates are obtained,
(C) A plurality of combinations of detection error coefficients a, b, and c in the three-axis directions, each of which is a constant, are set in advance, and coincide with the center of the provisional spherical coordinate and have a plurality of sets of detection error coefficients a, b. Among the plurality of aspherical coordinates obtained by applying any of c, c, the one having the smallest error from the plurality of coordinate point data is specified as the aspherical coordinate where the coordinate point data is located.
A magnetic detection device characterized by that. (D) The correction of the coordinate point data on the corrected spherical coordinate from the detection error coefficients a, b, c of the aspherical coordinate with the least error from a plurality of coordinate point data and the coordinates of the center of the provisional spherical coordinate. The magnetic detection device according to claim 1, wherein the magnetic detection device is converted into coordinate point data. 3. The magnetic sensing device according to claim 1, wherein the provisional spherical coordinate equation in (b) is expressed by the following equation (1).

However, xc, yc, zc are the coordinates of the center of the provisional spherical coordinates on the three-dimensional detection coordinates. The magnetic sensing device according to any one of claims 1 to 3, wherein the equation of the aspherical coordinate in (c) is expressed by the following equation (2).

However, xc, yc, zc are the coordinates of the center of the provisional spherical coordinates on the three-dimensional detection coordinates.   The magnetic detection device according to claim 1, wherein an orientation of a magnetic vector is obtained from corrected coordinate point data on the corrected spherical coordinate.   The magnetic detection device according to claim 1, wherein a rotation angle of the magnetic detection unit is obtained from an opening angle of a plurality of correction coordinate point data with respect to the center of the correction spherical coordinate.   5. The magnetism according to claim 1, wherein an angular velocity of the magnetic detection unit is obtained from an opening angle of a plurality of correction coordinate point data with respect to a center of the correction spherical coordinate and a time when the plurality of correction coordinate data are obtained. Detection device.

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