JP2011185861A - Geomagnetism detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a geomagnetism detector for highly accurately calculating a rotating position and angular velocity with noises removed by using a triaxial sensor for detecting geomagnetism. <P>SOLUTION: A coordinate point of a geomagnetism vector is computed based on detection outputs from three magnetic sensors for detecting the geomagnetic vector. If next coordinate point data D3 are contained in an area A1 of a radius r1 centering on an extension L1, the area A1 containing coordinate point data D1 and D2 computed, the data are extracted as normal coordinate point data while coordinate point data falling outside the area A1 are ignored as noise. By using a plurality of sets of normal coordinate point data, a locus circle along which coordinate point data move is found to determine the motion of the geomagnetic detector. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a geomagnetism detection device that detects geomagnetism with magnetic sensors directed in three orthogonal directions, and in particular, when a magnetic detection unit equipped with a magnetic sensor is rotated in a three-dimensional space, the rotation is performed. The present invention relates to a geomagnetic detection device that can know the movement.

  A geomagnetism detection device that detects geomagnetism using a triaxial magnetic sensor that detects magnetic field strengths in three directions orthogonal to each other is used as an orientation detection device, a rotation detection device, an attitude detection device, and the like.

  The magnetic gyro described in Patent Document 1 has a three-axis magnetic sensor that detects geomagnetism arranged on three-axis orthogonal coordinates. When this magnetic gyroscope is rotated in a three-dimensional space, a difference vector between two different time points is obtained using output data of three axes, and the difference vector becomes smaller than a predetermined threshold value. It is determined whether or not one of the three axes is rotating as a center.

  The magnetic gyro described in Patent Document 1 can detect the rotation state when rotating around any of the three axes determined by the orientation of the magnetic sensor. When it is rotated about the rotation axis, the rotation axis cannot be recognized, and it cannot be specified in which rotation plane it is rotating. That is, the angular velocity when rotating around an arbitrary axis in the three-dimensional space cannot be detected with only one magnetic gyro described in Patent Document 1.

  Patent Document 2 discloses an attitude sensor mounted on an airplane or the like. This attitude sensor has a geomagnetic detection device, and is provided with a load weight and a force detection device that detects gravity acting on the load weight. When the attitude sensor is tilted with an airplane, etc., the inclination with respect to the direction of gravity is detected by the detection output of the force detection device, and the azimuth output obtained by the geomagnetic detection device is used as information on the inclination posture obtained by the force detection device. To correct.

  Since the posture sensor described in Patent Document 2 includes not only a geomagnetic detection device but also a load weight and a force detection device that detects the gravity acting on the load weight, the device becomes large and heavy. It is difficult to install in small equipment for the purpose.

  The three-axis attitude detection device described in Patent Document 3 detects the attitude of a target object, and is equipped with both a magnetic sensor capable of detecting in three directions and a gyro sensor capable of detecting in three directions. Has been. For this reason, it is not suitable for mounting on a portable small device or the like, and both the magnetic sensor and the gyro sensor are mounted.

  In addition, when weak geomagnetism is detected by the magnetic sensor, it is inevitable that noise is superimposed on the detection output. The geomagnetism detection devices described in Patent Documents 1 to 3 disclose means for using the detected geomagnetism, but do not describe how to deal with noise.

JP 2008-224642 A JP-A-2-238336 JP 11-248456 A

  The present invention solves the above-mentioned conventional problems, detects geomagnetism with a magnetic sensor oriented in three orthogonal axes, and can identify the locus of rotational motion from the detection output of the magnetic sensor. The object is to provide a detection device.

  Another object of the present invention is to provide a geomagnetism detection device that can minimize the influence of detection noise of the magnetic sensor and reduce the calculation error of the locus of rotational movement.

The present invention includes a magnetic detection unit in which the X direction, the Y direction, and the Z direction orthogonal to each other are determined as reference directions, and a calculation unit.
An X-axis sensor in which the absolute value of the detection output becomes a maximum value when the X direction is directed to the geomagnetism direction and the absolute value of the detection output when the Y direction is directed to the geomagnetism direction. Is mounted as a Y-axis sensor having a maximum value, and a Z-axis sensor having a maximum detection output when the Z direction is directed in the direction of geomagnetism. It is rotatable in a three-dimensional direction while maintaining the orthogonal relationship between the Y-axis sensor and the Z-axis sensor,
The arithmetic unit converts the direction of the geomagnetic vector obtained from the detection output into coordinate point data on three-dimensional coordinates, and enters an area around the extension line connecting the two coordinate point data. The obtained coordinate point data is used as normal coordinate point data obtained next, and a trajectory circle along which the coordinate point data moves is obtained from a plurality of normal coordinate point data obtained by repeating this. It is.

  The present invention acquires a plurality of pieces of information on geomagnetic vectors specified by detection outputs of the X-axis sensor, the Y-axis sensor, and the Z-axis sensor as coordinate point data on three-dimensional coordinates, and uses the plurality of coordinate point data, The locus circle along which the coordinate point data moves is calculated. Therefore, it is possible to obtain an absolute rotational motion when the magnetic detection unit performs an arbitrary rotational operation.

  Further, since coordinate point data determined to be greatly deviated from the locus is excluded from the calculation among coordinate point data obtained continuously, the influence of noise and the like can be minimized.

  That is, the present invention ignores the coordinate point data out of the range as noise, and when the coordinate point data within the range is obtained thereafter, the coordinate point data is determined as the normal coordinate point data. Is.

  When the locus circle is specified, the present invention finds the moving angular velocity from the opening angle of the plurality of regular coordinate point data from the center of the locus circle and the time when the coordinate point data is obtained. Can do.

  As described above, when the magnetic detection unit is freely rotated in the space, the angular velocity of the movement can be accurately known. Further, according to the present invention, the angular acceleration can be obtained by differentiating the calculated angular velocity with respect to the time.

  The present invention can cancel the setting of the trajectory circle and calculate a new trajectory circle from the obtained coordinate point data when the number of coordinate point data out of the range reaches a predetermined number. It is.

  In the above calculation, when the radius of the trajectory circle changes greatly, an operation following the change can be performed.

  For example, according to the present invention, data in a circle with a certain radius on the extension line is used as normal coordinate point data.

  Alternatively, the present invention exists within the range of R / L, the ratio of the distance L from the previously obtained coordinate point data to a certain point on the extension line and the radius R from the extension line at that point in time. The coordinate point data being used may be regular coordinate point data.

  In addition, a range of a shape obtained by rotating a quadric curve with the coordinate point data obtained previously as the origin around the extension line is set, and the coordinate point data existing in the range is set as normal coordinates. It may be point data.

  The present invention can obtain the trajectory of an arbitrary motion of the magnetic detection unit using the detection output of the magnetic sensor directed in the three axial directions orthogonal to each other. In addition, the influence of detection noise of the magnetic sensor can be reduced, and a highly accurate calculation result can be obtained.

The circuit block diagram of the geomagnetism detection device of the embodiment of the present invention, The block diagram explaining the function of the calculating part provided in the geomagnetic detection apparatus shown in FIG. Explanatory drawing showing the processing operation of the data buffer, Explanatory drawing of the X-axis sensor, the Y-axis sensor and the Z-axis sensor provided in the geomagnetism detection unit, Explanatory diagram of 3D coordinates showing the principle of geomagnetic vector detection operation, Explanatory drawing of three-dimensional coordinates showing the detection operation of the geomagnetic vector when the magnetic detection unit is rotating around an arbitrary axis, Explanatory drawing explaining an example of the extraction method of coordinate point data, Explanatory drawing explaining the extraction method of coordinate point data when a movement locus | trajectory changes greatly, Explanatory drawing explaining the other example of the extraction method of coordinate point data, Explanatory drawing explaining the other example of the extraction method of coordinate point data, An explanatory view showing an example of a method of calculating a locus circle,

  A geomagnetic detection device 1 according to the embodiment of the present invention shown in FIG. As shown in FIG. 4, in the geomagnetic detection device 1, the X axis, the Y axis, and the Z axis, which are reference axes orthogonal to each other, are determined as fixed axes. The intersection of the X axis, the Y axis, and the Z axis is the reference origin O. The geomagnetism detection device 1 is mounted on a portable device or the like, and the magnetic detection unit 2 can freely move in space while maintaining the orthogonal relationship between the X axis, the Y axis, and the Z axis.

  As shown in FIG. 4, the X-axis sensor 3 is fixed along the X-axis, the Y-axis sensor 4 is fixed along the Y-axis, and the Z-axis sensor is fixed along the Z-axis. Has been. The X-axis sensor 3, the Y-axis sensor 4, and the Z-axis sensor 5 are all composed of GMR 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 under the pinned magnetic layer, and the magnetization of the pinned magnetic layer is pinned by antiferromagnetic coupling between the antiferromagnetic layer and the pinned magnetic layer.

  The X-axis sensor 3 detects a component of the geomagnetism facing in the X direction, and the magnetization direction of the pinned magnetic layer is fixed in the PX direction along the X 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 an X axis detection output. When a magnetic field directed in the X direction is not applied to the X-axis sensor 3, or when a magnetic field orthogonal to PX is applied, the X-axis detection output becomes a midpoint potential.

  When the entire magnetic detection unit 2 is tilted and the fixed direction PX of the magnetization of the fixed magnetic layer of the X-axis sensor 3 is set in the same direction as the geomagnetic vector V, the magnetic field component applied to the X-axis sensor 3 becomes a maximum value. The X-axis detection output at this time has 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 detected output of the X 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 Y-axis or Z-axis detection output.

  When the fixed direction PY of the magnetization of the fixed magnetic layer of the Y-axis sensor 4 is set to the same direction as the geomagnetic vector V, the Y-axis detection output becomes a maximum value on the plus side with respect to the midpoint potential. When 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 detection output of the Y-axis becomes a negative maximum value with respect to the midpoint potential. Similarly, if the fixed direction PZ of the magnetization of the fixed magnetic layer of the Z-axis sensor 5 is set in the same direction as the geomagnetic vector V, the Z-axis detection output becomes a maximum value on the plus side with respect to the midpoint potential. When the fixed direction PZ of the magnetization of the fixed magnetic layer of the Z-axis sensor 5 is directed opposite to the geomagnetic vector V, the detection output of the Z-axis becomes a negative maximum value 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 magnetic 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 X 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 respective directions 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 magnetic components of the X axis, the Y axis, and the Z axis detected by the magnetic field data detection unit 6 are sampled intermittently in a short cycle, and the calculation unit 10 Is read out. 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.

  As shown in FIG. 2, the arithmetic unit 10 performs a plurality of stages of arithmetic processing based on software. The X-axis detection output, the Y-axis detection output, and the Z-axis detection output converted into digital data are arithmetically processed by the main calculation unit 15, and the coordinates on the three-dimensional coordinates of XYZ shown in FIG. Converted to point data D.

  Each axis of XYZ of the three-dimensional coordinates shown in FIG. 5 is fixed to the geomagnetic detection device 1, and as shown in FIG. 4, the X-axis sensor 3 is fixed along the X-axis, and the Y-axis The sensor 4 is fixed along the Y axis, and the Z axis sensor 5 is fixed along the Z axis.

  As shown in FIG. 5, when the geomagnetic detection device 1 is placed anywhere on the earth, the magnetic field data detection unit 6 detects the detection output xb in the X-axis direction, the detection output yb in the Y-axis direction, and Z An axial detection output zb is obtained. In the main calculation unit 15 of the calculation unit 10 shown in FIG. 2, the coordinate point data D (xb, yb, zb) is calculated from the three-dimensional detection output. Since the detection output detected by the magnetic field data detection unit 6 is sampled at a constant cycle, the coordinate point data D is calculated one after another from this detection output.

  As shown in FIG. 5, the coordinate point data D (xb, yb, zb) is represented as a point on the spherical surface G set on three-dimensional coordinates. Here, assuming that the center of the spherical surface G coincides with the reference origin O of the three-dimensional coordinates of XYZ set in the geomagnetic detection device 1, the coordinate point data D and the reference origin O are The connecting line is the geomagnetic vector V, and the distance between the coordinate point data D and the reference origin O is the absolute value of the geomagnetic vector V. The absolute value of the geomagnetic vector V is proportional to the absolute value of the maximum value of each detection output in the X-axis direction, the Y-axis direction, and the Z-axis direction obtained by the magnetic field data detection unit 6. The radius R of the spherical surface G is proportional to the absolute value of the geomagnetic vector V.

  Here, if it is assumed that the Z axis set in the geomagnetic detection device 1 is directed in the direction of gravity, the geomagnetic dip angle can be obtained from the angle formed by the XY coordinate plane and the geomagnetic vector V. The dip changes depending on the location on the earth.

  When the magnetic detection unit 2 is rotated around the Z axis while the Z axis of the magnetic detection unit 2 is accurately fixed in the direction of gravity, the coordinate point data Ha calculated from the detection output sampled at regular intervals is obtained. And move along the locus circle H0. Assuming that the center of the spherical surface G coincides with the reference origin O of the three-dimensional coordinates set in the geomagnetic detection device 1, the locus circle H0 defines the reference origin O of the three-dimensional coordinates of XYZ. It coincides with the latitude line of the spherical surface G as the center.

  However, the magnetic detection unit 2 is affected by a magnetic generation source existing in the vicinity, the X-axis sensor 3, the Y-axis sensor 4, and the Z-axis sensor 5 have variations in sensitivity, and the magnetic field data detection unit 6 and the like. Noise is superimposed on this circuit. In actuality, each detection output obtained from the magnetic field data detection unit 6 includes not only the geomagnetic detection output but also other detection values and noise. Accordingly, at the stage where the main calculation unit 15 calculates the coordinate point data D, the relationship between the obtained coordinate point data D and the reference origin O of the three-dimensional coordinates of XYZ is unknown. That is, the center of the spherical surface G on which the coordinate point data D moves does not necessarily match the reference origin O of the X axis, Y axis, and Z axis set in the magnetic detection unit 2.

  In this case, when the geomagnetic detection device 1 moves and obtains a plurality of coordinate point data D, the locus of the coordinate point data D moves on the three-dimensional coordinates set in the magnetic detection unit 2. As a result, there is a problem that the locus during rotation cannot be specified and the angular velocity cannot be calculated.

  Therefore, in the calculation unit 10 shown in FIG. 2, by executing the following software, when the geomagnetism detecting device 1 is moved in an arbitrary direction, it is determined which direction and what type of movement is being performed. It can be calculated.

  FIG. 6 shows coordinate point data D1, D2,..., Dn obtained when the geomagnetism detection device 1 is rotating around an arbitrary axis other than XYZ.

  In the data extraction unit 12 shown in FIG. 2, when the coordinate point data D calculated by the main calculation unit 15 is obtained, the coordinate point data is distinguished from those having continuity and those having no continuity. The coordinate point data with the is extracted as normal coordinate point data. The latest extracted regular coordinate point data is stored in the storage unit 11a of the data buffer 11 shown in FIG. At this time, the past normal coordinate point data is sequentially shifted and stored in the storage units 11b, 11c,. The data storage location moves sequentially each time new regular coordinate point data is obtained, and the oldest coordinate point data is discarded from the storage unit 11m.

  FIGS. 7 and 8 show a calculation method for extracting normal coordinate point data having continuity in the data extraction unit 12. As shown in FIG. 7, in the data extraction unit 12, when the coordinate point data D1 and D2 calculated by the main calculation unit 15 are obtained, the line connecting the coordinate point data D1 and D2 is calculated as the extension line L1. Is done. Since the coordinate point data D1 and D2 are obtained as coordinate points on the three-dimensional coordinates, the equation of the extension line L1 can be calculated from the coordinate point data D1 and D2.

For example, if the coordinates of the coordinate point data D1 are (x1, y1, z1) and the coordinates of the coordinate point data D2 are (x2, y2, z2), the coordinates (x, y, z) of the points on the extension line L1 Where T is a variable x = x1 + T × (x1−x2)
y = y1 + T × (y1-y2)
z = z1 + T × (z1-z2)
It can be expressed as

  As shown in FIGS. 7 and 8, the data extraction unit 12 sets a cylindrical area A1 having a radius r1 centered on the calculated extension line L1. Then, when it is determined that the coordinate point data D3 obtained from the main calculation unit 15 is within the area A1, the coordinate point data D3 is extracted as normal coordinate point data, and FIG. Are stored in the storage unit 11a of the data buffer 11 shown in FIG. At this time, the coordinate point data D2 is sent to the storage unit 11b, and the coordinate point data D1 is sent to the storage unit 11c.

  In FIG. 7, the coordinate point data D3, D4, D5, D6, D7, and D8 obtained thereafter are all determined to be normal coordinate point data that falls within the area A1, and are sequentially stored in the data buffer 11. However, in FIG. 7, the subsequent coordinate point data D9, D10, D11, and D12 deviate from the area A1 having the radius r1 centered on the extension line L7 connecting the normal coordinate point data D7 and the normal coordinate point data D8. The coordinate point data D9, D10, D11, and D12 are not extracted as normal coordinate point data and are not stored in the data buffer 11.

  The coordinate point data D9, D10, D11, and D12 do not return to the area A1 having the radius r1 centered on the extension line L6 that connects the coordinate point data D7. It is determined that the point data has been interrupted. Further, the coordinate point data D9, D10, D11, and D12 are close to each other in coordinate positions. Therefore, the main calculation unit 15 obtains coordinate point data D8 by the rotational motion of the geomagnetism detecting device 1. Judged to have stopped at the time.

  That is, when the distance between the two coordinate point data is equal to or longer than a preset length like the coordinate point data D1 and D2, an extension line L1 connecting the two coordinate point data D1 and D2 is calculated, and this extension An area A1 having a radius r1 including the line L1 is set, and it is determined whether or not the next coordinate point data D3 is within the area A1. However, when the distance on the coordinates of the coordinate point data obtained continuously, such as the coordinate point data D9, D10, D11, D12, is less than the set length, the extension line L1 and the area A1 It is determined that the movement of the geomagnetism detection device 1 is stopped without setting.

  In the example shown in FIG. 8, the coordinate point data D1, D2, D3, and D4 are extracted as normal coordinate point data and sequentially stored in the data buffer 11. Here, the coordinate point data Dj obtained next to the coordinate point data D4 is out of the area A1 having the radius r1 centered on the extension line L3 obtained from the normal coordinate point data D3 and D4. Accordingly, the coordinate point data Dj is determined as noise, and is not extracted by the data extraction unit 12 and is not stored in the data buffer 11. However, since the coordinate point data D5 obtained thereafter is within the range of the area A1 having the radius r1 centered on the extension line L3, the coordinate point data D5 is extracted as normal coordinate point data. . Since the subsequent coordinate point data D6 is also in the area A1 with the radius r1 centered on the extension line L4, it is also extracted as normal coordinate point data.

  As described above, when any coordinate point data deviates from the area A1, when the coordinate point data obtained thereafter returns to the range of the area A1, the coordinate point data is a continuous normal coordinate. Extracted as point data.

  In the example shown in FIG. 8, the coordinate point data Da, Db, Dc,... Obtained after the normal coordinate point data D6 are all radii centered on the extension line L5 extending from the coordinate point data D5, D6. It is out of the area A1 of r1. However, the coordinate point data Da, Db, Dc,... Are more than a predetermined distance on the three-dimensional coordinates. In the data extraction unit 12, when no coordinate point data exceeding the preset number enters the area A1, and the distance between these coordinate point data is more than a predetermined value, the geomagnetic detection device 1 is stopped. It is determined that the motion has changed along a motion track different from the motion track when the coordinate point data D1 to D6 are obtained. Then, the process proceeds to data extraction using the coordinate point data Da, Db, Dc,.

  When it is determined that the movement has changed to a new movement locus, as shown in FIG. 8, an extension line La connecting the coordinate point data Da and Db and an area Aa having a radius ra centered on the extension line La are set. Is done. When the coordinate point data Dc obtained thereafter enters the area Aa, the coordinate point data Da is extracted as normal coordinate point data and stored in the data buffer 11. In FIG. 8, coordinate point data Dc, Dd, De,... Are extracted as normal coordinate point data appearing within the area Aa and stored in the data buffer 11.

  Here, the radius r1 of the area A1 and the radius ra of the area Aa are set in the data extraction unit 12 as follows. As shown in FIGS. 7 and 8, when coordinate point data D spaced apart by a predetermined distance or more on three-dimensional coordinates is obtained one after another, the data extraction unit 12 uses the geomagnetic detection device 1. Is determined to be continuously exercising. Then, an area A having a radius r centered on the extension line L calculated from the two coordinate point data D is set. At this time, a minimum value is selected as the radius r. When the coordinate point data D obtained thereafter does not enter the area A having the radius r, the radius r is slightly increased. By repeating this, when a predetermined number of coordinate point data D1, D2, D3,... Enters the area, the radius r1 of the area A1 is fixed.

  Even when the coordinate point data Da, Db, Dc,... Shown in FIG. 8 are obtained, the coordinate point obtained by first setting the area A having the minimum radius r and then leaving a certain distance or more. The radius r of the area Aa is fixed by changing the radius r until a predetermined number or more of data enters the area.

  The data extraction unit 12 and the main calculation unit 15 determine that the motion trajectory of the geomagnetic detection device 1 has changed when the radius r1 of the area A1 is switched to the radius ra of the area Aa.

  In the locus circle calculation unit 13 provided in the operation unit 10 of FIG. 2, the locus circle is calculated using data extracted as normal coordinate point data and stored in the data buffer 11.

  As shown in FIGS. 7 and 8, when the normal coordinate point data D1, D2, D3,... Are extracted and stored in the data buffer 11, the trajectory circle calculation unit 13 performs a certain point in time. The normal coordinate point data and the normal coordinate point data obtained before that are called to obtain reference coordinate point data.

  For example, coordinate point data D1 and previously obtained coordinate point data Dn are set as reference coordinate point data. A plurality of coordinate point data D2, D3, D4,... Positioned between the reference coordinate point data D1 and the reference coordinate point data Dn are set as intermediate coordinate point data. All of the normal coordinate point data located between the reference coordinate point data D1 and the reference coordinate point data Dn may be used as the intermediate coordinate point data D2, D3, D4,. Some of a plurality of normal coordinate point data located between the reference coordinate point data D1 and the reference coordinate point data Dn are extracted and used as intermediate coordinate point data D2, D3, D4,. May be.

  As shown in FIG. 11, the locus circle calculation unit 13 obtains a virtual circle Ha including two reference coordinate point data D1, reference coordinate point data Dn, and one intermediate coordinate point data D2. Since the reference coordinate point data D1, Dn and the intermediate coordinate point data D2 are all expressed by coordinates (x, y, z) on the three-dimensional coordinates of XYZ, a circle including three coordinate point data The virtual circle Ha is specified by obtaining the above equation. Further, a virtual circle Hb including the reference coordinate point data D1, the reference coordinate point data Dn, and the intermediate coordinate point data D3 is calculated, and similarly includes the reference coordinate point data D1, the reference coordinate point data Dn, and the intermediate coordinate point data D4. A virtual circle Hd including the virtual circle Hc, the reference coordinate point data D1, the reference coordinate point data Dn, and the intermediate coordinate point data D5 is calculated, and other virtual circles are also calculated for each intermediate coordinate point data.

  Next, the distance between the arc of the virtual circle Ha and all the intermediate coordinate point data D2, D3, D4,. Alternatively, the distance between the center point of the virtual circle Ha and all the intermediate coordinate point data D2, D3, D4,. The virtual circle Ha can be expressed as an equation on the three-dimensional coordinates of XYZ, and each intermediate coordinate point data is also expressed as a point on the three-dimensional coordinates of XYZ. The distance can be obtained by calculating by the least square method using the equation of the circle and the coordinate data of the intermediate coordinate point data.

  For every virtual circle Ha, Hb, Hc, Hd,..., The distance to the intermediate coordinate point data D2, D3, D4,. The virtual circle with the shortest calculated distance is specified as the locus circle H1 in which the coordinate point is moving. In the example of FIG. 11, the virtual circle Hc including the reference coordinate point data D1, the reference coordinate point data Dn, and the intermediate coordinate point data D4 is specified as the locus circle H1.

  By specifying the trajectory circle H1, it is possible to know what trajectory the geomagnetic detection device 1 is moving.

  As shown in FIGS. 7 and 8, while it is detected that coordinate point data D1, D2, D3,... Having continuity are in the same area A1, the trajectory circle calculation unit 13 performs geomagnetism. It is determined that the detection device 1 is moving along a constant locus circle H1. Then, as shown in FIG. 8, when the radius of the area for determining whether or not coordinate point data is entered is switched from r1 to ra, it is updated to a new locus circle H2 calculated by the method shown in FIG. It is determined that the geomagnetic detection device 1 is moving along the new locus circle H2.

  As shown in FIG. 6, the locus circle calculation unit 13 obtains the center O1 of the locus circle H1 calculated and set, and the axis perpendicular to the plane including the locus circle H1 and passing through the center O1 is the rotation axis. It is obtained as S0. Then, any coordinate point data from the reference coordinate point data D1 to the reference coordinate point data Dn is extracted, and the opening angle from the center O1 of the coordinate point data is obtained. The rotational angular velocity of the geomagnetism detecting device 1 is obtained by differentiating the opening angle with the time when two coordinate point data are obtained. Similarly, when the locus circle is updated to H2, the rotational angular velocity is obtained.

  After calculating a certain locus circle H1 and its rotation axis S0, normal coordinate point data Da, Db, Dc,... Shown in FIG. 8 are obtained, and another locus circle H2 and its rotation axis S1 are obtained. When it is obtained, as shown in FIG. 6, the center of the spherical surface Ga on which the coordinate point data D moves can be obtained by obtaining the intersection point Oa of the two rotation axes S0 and S1. Calibration for obtaining the center of the spherical surface on which the coordinate point data moves by updating the coordinates of the intersection Oa as the coordinates of the reference origin O of the three-dimensional coordinates of XYZ set in the geomagnetic detection device 1 Action can be performed.

  Since the center of the spherical surface can be made coincident with the reference origin O by the calibration operation, thereafter, the coordinate position of the coordinate point data can be accurately grasped as data on the XYZ coordinates.

  Further, if an acceleration sensor or the like that detects the direction of gravity is provided in the geomagnetic detection device 1 and correction is performed so that the detected direction of gravity coincides with the Z-axis, the orientation of the spherical Ga obtained by the calibration operation is changed to X Can be specified on -YZ coordinates. Therefore, it is possible to obtain the azimuth and dip angle of the geomagnetic vector V.

FIG. 9 shows another data extraction method executed by the data extraction unit 12.
In this data extraction method, an extension line L1 connecting the coordinate point data D1 and the coordinate point data D2 is obtained, and when the next coordinate point data D3 is obtained, the coordinate line data D2 and the coordinate point data D3 are on the extension line. The cone-shaped area A3 is set so that the distance L1 at this time and the radius R1 at that time have a constant ratio R / L. If coordinate data D3 is within this area A3, it is extracted as normal coordinate point data.

  This setting method of the area A3 is effective when the angular velocity of the motion of the geomagnetic detection device 1 is changing. In FIG. 9, the angular velocity is substantially constant from the coordinate point data D1 to the coordinate point data D4, but the angular velocity is increased after the coordinate point data D4 is obtained. Since the sampling period of the coordinate point data is constant, when the angular velocity increases, the distance of the coordinate point data on the three-dimensional coordinates increases.

  As shown in FIG. 9, when the distance between the coordinate point data D5 and the coordinate point data D6 is greatly widened, the coordinate point data D5 is obtained on the extension line including the coordinate point data D4 and D5 and then the coordinate point data D5 is obtained. The conical area A3 is set so that the distance L4 on the extension line until the data D6 is obtained and the radius R4 at that time have the same ratio R / L as described above. If the coordinate point data D6 is within the area A3, it is extracted as normal coordinate point data.

  In this extraction method, if the geomagnetic detection device 1 is moving in a circle and the coordinate point data is moving on the same locus circle on the three-dimensional coordinates, the angular velocity changes, and the distance between the coordinate point data Even if changes, normal coordinate point data can always be extracted based on the same standard.

FIG. 10 shows another data extraction method executed by the data extraction unit 12.
In this data extraction method, when an extension line L1 connecting the coordinate point data D1 and the coordinate point data D2 is obtained, an area obtained by rotating a quadratic curve having the coordinate point D2 as the origin about the extension line L1 Set A4. A quadratic curve is, for example, a parabola. This area A4 can be easily set using a quadratic equation.

  Further, in the area A4, as in the area A3 shown in FIG. 9, the radius of the area A4 increases as the distance between the coordinate point data increases. Therefore, even if the angular velocity changes and the distance of the coordinate point data changes, normal coordinate point data can always be extracted based on the same reference.

  The geomagnetic detection device of the present invention can calculate an angular velocity by specifying a three-dimensional rotational motion. Therefore, it can be used for a portable game device or an input device of a game device. It can also be used as a detection unit that detects changes in posture of the robot's arms and joints.

DESCRIPTION OF SYMBOLS 1 Geomagnetism detection apparatus 2 Magnetic 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 11 Data buffer 12 Data extraction part 13 Trajectory circle calculation part 14 Angular velocity calculation part 15 Main calculation part A Area D1, D2, D3, D4, ... Coordinate point data L Extension line r Radius V Geomagnetic vector

Claims (7)

A magnetic detection unit in which the X direction, the Y direction, and the Z direction orthogonal to each other are determined as reference directions, and a calculation unit;
An X-axis sensor in which the absolute value of the detection output becomes a maximum value when the X direction is directed to the geomagnetism direction and the absolute value of the detection output when the Y direction is directed to the geomagnetism direction. Is mounted as a Y-axis sensor having a maximum value, and a Z-axis sensor having a maximum detection output when the Z direction is directed in the direction of geomagnetism. It is rotatable in a three-dimensional direction while maintaining the orthogonal relationship between the Y-axis sensor and the Z-axis sensor,
The arithmetic unit converts the direction of the geomagnetic vector obtained from the detection output into coordinate point data on three-dimensional coordinates, and enters an area around the extension line connecting the two coordinate point data. The obtained coordinate point data is used as normal coordinate point data obtained next, and a trajectory circle along which the coordinate point data moves is obtained from a plurality of normal coordinate point data obtained by repeating this data. Detection device.   2. The geomagnetism according to claim 1, wherein the coordinate point data outside the range is ignored as noise, and when the coordinate point data within the range is obtained thereafter, the coordinate point data is determined as normal coordinate point data. Detection device.   The moving angular velocity is obtained from an opening angle of a plurality of regular coordinate point data from the center of the locus circle and a time when the coordinate point data is obtained when the locus circle is specified. The geomagnetic detection device described.   4. The method according to claim 1, wherein when a predetermined number of coordinate point data is out of the range, the setting of the locus circle is canceled and a new locus circle is calculated from the coordinate point data obtained thereafter. The geomagnetic detection device according to the above.   The geomagnetic detection device according to claim 1, wherein normal coordinate point data is included in a circle having a certain radius on the extension line.   The ratio of the distance L from the previously obtained coordinate point data to a certain point on the extension line and the radius R from the extension line at that point, the coordinate point data existing within the range of R / L The geomagnetism detecting device according to any one of claims 1 to 4, wherein is a normal coordinate point data.   A range of a shape obtained by rotating a quadric curve with the coordinate point data obtained previously as the origin around the extension line is set, and the coordinate point data existing in the range is set as normal coordinate point data The geomagnetic detection device according to any one of claims 1 to 4.

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