JP4988170B2 - Azimuth measuring apparatus and azimuth measuring method - Google Patents

Description

  The present invention relates to an azimuth measuring device and an azimuth measuring method. In particular, the present invention relates to an azimuth measuring device for an automobile and an azimuth measuring method for measuring geomagnetism while installed in a car and calculating an offset and an azimuth calculated from data obtained by the measurement.

  In recent years, an azimuth measuring device for measuring geomagnetism and calculating the azimuth angle, so-called electronic compass, has been actively developed, and a small one has been developed, such as a mobile phone and a PDA (Personal Digital Assistance). There is an example that is installed in equipment. Displaying the current position and traveling direction of the terminal owner by linking with a GPS (Global Positioning System) device that can also be used in mobile devices, and a map distribution / display application using a local or mobile phone network or wireless WAN (Wide Area Network) network Thus, there is an application example for performing pedestrian navigation.

  As an electronic compass used for a portable device, a three-axis electronic compass capable of detecting a magnetic field in the three-axis directions of X, Y, and Z and calculating an azimuth angle is advantageous.

  The first reason is that if it is a three-axis electronic compass, set the handheld angle of the mobile device or obtain the current handheld tilt angle information from the tilt angle sensor, etc., and perform the tilt angle correction calculation using that value Thus, even if the portable device is tilted, the correct orientation can be calculated, which increases convenience for the user.

  The second reason is that, for example, by applying a technique as disclosed in Patent Document 1 by the applicant's invention, the three-axis magnetic sensor output obtained from the natural movement of the user can be used to detect the interior of the portable device or magnetic field. This is because the offset of the sensor itself can be calculated and corrected, so that the user need not be aware of the calibration operation.

  Disclosed in Patent Document 1 is that the locus of the outputs of the three-axis magnetic sensors orthogonal to each other when the portable device is freely moved is distributed on the surface of the sphere, This is a method of estimating by deriving a point where the distance from the output point of the magnetic sensor is equal.

  On the other hand, car navigation devices installed in automobiles are well known. This displays the current position and traveling direction of a vehicle based on information such as a GPS device, an on-vehicle angular velocity sensor (gyroscope), and an axle rotation angle sensor. Thus, car navigation devices for automobiles are expensive, and although the penetration rate is growing, the rate of non-mounted vehicles is still high. Therefore, if a mobile device that performs pedestrian navigation is installed in an automobile, if it is possible to navigate for an automobile, it is possible to easily obtain similar functions without purchasing and installing a car navigation device. This is an advantage for the user.

  In addition, as a technique for obtaining an offset when a portable device is fixedly installed in an automobile, there is one disclosed in Patent Document 2. This patent document 2 discloses that since an automobile travels on a substantially horizontal plane, the measured values of geomagnetism are not distributed on the spherical surface but distributed on the circumference in the space that is the intersection of the spherical surface and the plane. This is a method of estimating an offset using. Calculate the distance between the measured geomagnetic data group and the plane determined by the installation posture of the mobile device in the car. If the distance variation is within a specific range, calculate the offset. The offset is not calculated as data containing a lot of. The plane determined by the installation posture of the mobile device may be obtained from an acceleration sensor mounted on the mobile device, or the plane is estimated so that the sum from the measured geomagnetic data group is minimized, An estimated plane may be used.

  In addition to the method disclosed in Patent Document 1, the offset when the pedestrian has a portable device can further improve the offset estimation accuracy by the method applied in Patent Document 3. In this Patent Document 3, data suitable for calculation for offset estimation is intentionally selected from the measured geomagnetic data group, or the reliability of the estimated offset is calculated, depending on the reliability. By discarding the offset, it is possible to calculate the offset according to the situation. In this case, if you want to obtain the offset with priority over accuracy, such as when the offset has not been obtained or when the amount of magnetization of the mobile device has changed in advance, the data selection criteria and reliability If you want to set the sex criteria softly and want to obtain a high-precision offset, make the criteria stricter.

  Even when a mobile device is set inside a car and a 3-axis electronic compass is used, the above method can basically be used. However, it can be used inside a car by considering the environment unique to the car. In this case, the accuracy can be improved.

International Publication No. WO2004 / 003476 Pamphlet Japanese Patent Application No. 2004-235608 PCT / 2004/009324 PCT / 2004/018888

  In order to use an azimuth measuring apparatus using a three-axis electronic compass designed for portable equipment in a state where it is installed in an automobile, the following problems are known (for example, see Patent Document 2).

  In other words, since the interior of an automobile is generally a magnetic body and is magnetized, the magnetic field environment when a human is carrying a portable device and the internal magnetic field environment of the automobile are significantly different. The offset magnetic field sensed by the angle sensor is different, and the azimuth angle display error becomes large. In order to display an accurate azimuth, it is necessary to correct the offset inside the automobile.

  The amount of magnetization of the vehicle body, that is, the offset magnetic field changes by passing through a place where a large current flows such as a railroad crossing or a place where the magnetic strength is strong such as near an iron structure.

  In addition, when navigation is performed with a portable device, it is often installed in a place where the temperature changes drastically, such as on the front panel. For this reason, the offset of the portable device or the sensor itself changes every moment depending on the temperature.

  In addition, even if the amount of magnetization does not change, it may be caused by various magnetic noises generated inside the automobile, or a place where a large current flows, such as a railroad crossing or near an iron structure, or a structure that is magnetized during traveling. In many cases, the trajectory of the output of the magnetic sensor is greatly separated from the spherical surface.

  Therefore, in the case where an azimuth measuring device using a three-axis electronic compass designed for portable devices is used in an automobile, the estimation accuracy of the offset magnetic field and the calculation accuracy of the azimuth cannot be improved. As a result, there is a problem that an accurate azimuth angle cannot be obtained.

  Therefore, an object of the present invention is to improve the estimation accuracy of the offset magnetic field and the calculation accuracy of the azimuth angle even when the electronic compass mounted on the portable device is used in an automobile, and to increase the azimuth angle. The present invention relates to an azimuth measuring device and an azimuth measuring method that can be calculated with high accuracy.

The present invention corrects the three-dimensional data obtained based on the geomagnetism data of each axis of the three axes detected by the geomagnetism detection means for detecting the geomagnetism of each axis of the three axes based on a predetermined reference, An offset filter means for outputting the offset three-dimensional correction data obtained by the correction, and the three-dimensional data obtained based on the geomagnetic data of each of the three axes detected by the geomagnetism detection means based on a predetermined reference. An azimuth filter unit that corrects and outputs three-dimensional correction data for azimuth obtained by the correction, and an offset that calculates an offset based on the three-dimensional correction data for offset output from the offset filter unit Output from the calculating means, the offset calculated by the offset calculating means, and the azimuth angle filter means Based on the serial azimuth 3-D for angle correction data, comprising an azimuth calculating means for calculating an azimuth angle, the filter means and / or azimuth filter means for the offset, the change amount limiting means, the first region Inner averaging means, second intra-area averaging means, means comprising both the change amount limiting means and the first intra-area averaging means, the change amount limiting means, and the second area. And means for selecting from the group consisting of both means, and the change amount limiting means, the change amount limiting means, the three-dimensional data newly input to the change amount limiting means, Means for determining whether or not the distance from the three-dimensional data output immediately before the change amount limiting means is within a predetermined threshold; and if the distance is less than or equal to the predetermined threshold, the newly input Means to output 3D data as next output When the distance exceeds the predetermined threshold, the intermediate point between the immediately preceding three-dimensional data and the latest three-dimensional data, and the distance from the immediately preceding three-dimensional data being a predetermined value The first intra-region averaging means determines whether or not the three-dimensional data newly input to the intra-region averaging means exists in a specific region. And an average of the three-dimensional data when the newly input three-dimensional data is determined to exist outside the specific area and continuously exists within the specific area until it is outside the specific area. The value or median is calculated, and the value obtained by the calculation is output as three-dimensional correction data, and the three-dimensional data when it is continuously present in the specific area is discarded, and the specific area is changed to the new value. Based on the 3D data input to And means for constant, the second region averaging means, three-dimensional data newly inputted to within that region averaging means includes means for determining whether present in a particular area When it is determined that the newly input three-dimensional data exists in the specific area, an average value or median value of the three-dimensional data in the specific area is calculated, and a value obtained by the calculation is calculated as 3 Means for outputting as dimension correction data, and when determining that the newly input three-dimensional data does not exist in the specific region, the newly input three-dimensional data is output as three-dimensional correction data; discard three-dimensional data to be present in a particular area, the specific area, wherein the chromatic child and means for resetting on the basis of the three-dimensional data input newly said.

The offset filter means and / or the azimuth angle filter means reduce noise included in the geomagnetic data of each of the three axes .

The specific area is a closed area centered on a predetermined center point, and the center point is changed by three-dimensional data newly input to the offset filter means and / or the azimuth filter means. It is characterized by.

  The specific area may be an area surrounded by a cube or an octahedron.

According to the present invention, the step of detecting the geomagnetism of each of the three axes and the three-dimensional data obtained based on the detected geomagnetism data of each of the three axes is corrected based on a predetermined standard, and the correction is obtained. An offset filter step for outputting corrected three-dimensional data for offset, and three-dimensional data obtained based on the detected geomagnetic data of each axis of the three axes are corrected based on a predetermined reference, and the orientation obtained by the correction An azimuth filter step for outputting three-dimensional correction data for corners, an offset calculation step for calculating the offset based on the outputted three-dimensional correction data for offset, the calculated offset, and the output An azimuth angle calculating step for calculating the azimuth angle based on the three-dimensional correction data for the azimuth angle, and the offset filtering step and / or Azimuth filter step includes a variation limiting step, a first region averaging process, and a second region averaging process, and the said variation limiting step first region averaging step And a step consisting of both the change amount limiting step and the second in-region averaging step, and the change amount limiting step is selected from the group consisting of: , the three-dimensional data newly input to the filter, the steps of the distance between the three-dimensional data in which the filter has been output immediately before it is determined whether or not within the predetermined threshold value, the distance is the predetermined threshold value In the following cases, the step of setting the newly input three-dimensional data as the next output, and if the distance exceeds the predetermined threshold, the immediately preceding three-dimensional data and the latest three-dimensional data Is the 3D data just before the intermediate point? Or a point distance is a predetermined value and a step of the next output, the first region averaging step, 3-dimensional data newly input to the filter is present in a particular area A step of determining whether or not, and when the newly input three-dimensional data is determined to exist outside the specific area, 3 when the data is continuously within the specific area until it is outside the specific area The average value or median value of the dimensional data is calculated, and the value obtained by the calculation is output as corrected three-dimensional data, and the three-dimensional data when continuously present in the specific area is discarded, and the specified A step of resetting a region based on the newly input three-dimensional data, and the second intra-region averaging step is configured such that the three-dimensional data newly input to the filter is within a specific region. Determining whether it exists, and When it is determined that the inputted three-dimensional data exists in the specific area, the average value or median value of the three-dimensional data in the specific area is calculated, and the value obtained by the calculation is corrected three-dimensionally. A step of outputting as data, and when it is determined that the newly input three-dimensional data does not exist in the specific region, the newly input three-dimensional data is output and the three-dimensional data existing in the specific region is output. discard the dimension data, characterized that you and a step of re-set based on the specific area in the three-dimensional data input newly said.

The plane data selection means is characterized in that the oldest three-dimensional data among the three-dimensional data group composed of the predetermined number N of three- dimensional data is used as the next output.

According to the present invention, the step of detecting the geomagnetism of each of the three axes and the three-dimensional data obtained based on the detected geomagnetism data of each of the three axes is corrected based on a predetermined standard, and the correction is obtained. An offset filter step for outputting corrected three-dimensional data for offset, and three-dimensional data obtained based on the detected geomagnetic data of each axis of the three axes are corrected based on a predetermined reference, and the orientation obtained by the correction An azimuth filter step for outputting three-dimensional correction data for corners, an offset calculation step for calculating the offset based on the outputted three-dimensional correction data for offset, the calculated offset, and the output based on the three-dimensional correction data the azimuth angle that is, comprising a azimuth calculation step of calculating the azimuth angle, the filter process and / or for the offset The azimuth filter step is a step of determining whether or not a distance between the three-dimensional data newly input to the filter and the three-dimensional data output immediately before the filter is within a predetermined threshold; When the distance is less than or equal to the predetermined threshold value, the step of setting the newly input three-dimensional data as the next output; and when the distance exceeds the predetermined threshold value, the immediately preceding three-dimensional data and the A change amount limiting step including a step of outputting a point that is an intermediate point with the latest three-dimensional data and the distance from the previous three-dimensional data is a predetermined value, and is newly input to the filter A step of determining whether or not three-dimensional data exists in a specific area; and when it is determined that the newly input three-dimensional data exists outside the specific area, Continuously in a specific area The average value or median value of the three-dimensional data is calculated, and the value obtained by the calculation is output as corrected three-dimensional data, and the three-dimensional data when continuously present in the specific area is discarded. A first in-region averaging process including a step of resetting the specific region based on the newly input three-dimensional data, and the three-dimensional data newly input to the filter And determining whether or not the newly input 3D data exists in the specific area, the average value or median value of the 3D data in the specific area is determined. A step of calculating and outputting the value obtained by the calculation as three-dimensional correction data, and when the newly input three-dimensional data is determined not to exist in the specific area, the newly input 3 Dimensional data And a step of discarding the three-dimensional data existing in the specific area, and resetting the specific area based on the newly input three-dimensional data. It comprises at least one process selected from the group consisting of .

  According to the present invention, the detected geomagnetic data is guided and corrected to the offset filter and the azimuth filter, respectively, and based on the corrected offset correction data and azimuth correction data, the offset magnetic field is estimated and Since the calculation of the azimuth angle is performed, the estimation accuracy of the offset magnetic field and the calculation accuracy of the azimuth angle are improved even when the three-axis electronic compass mounted on the portable device is installed and used in a car. Accordingly, the azimuth angle can be calculated with high accuracy.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[First example]
A first embodiment of the present invention will be described with reference to FIGS.

<Configuration>
FIG. 1 shows the configuration of the azimuth measuring apparatus 100.

  The apparatus 100 includes a three-axis geomagnetism detection unit 1 including a geomagnetic sensor that detects geomagnetic data, an offset calculation filter unit 2, a data sorting selection unit 3, an offset calculation unit 4, and an azimuth calculation filter unit. 5, an azimuth angle calculation unit 6, a geomagnetic offset storage unit 7, and a portable terminal installation posture storage unit 8. The portable terminal installation posture storage unit 8 stores installation posture data measured by the tilt angle sensor 9 or a predetermined installation posture.

<Operation>
The operation of this apparatus will be described.

<Offset estimation during walking>
FIG. 2 shows a flowchart of offset estimation during walking.

  In step S1, the triaxial geomagnetism detector 1 measures the geomagnetism and detects it as triaxial geomagnetic data.

  In step S2, the detected three-axis magnetic data is stored in the data sorting / selecting unit 3 serving as an offset calculation data buffer. This data buffer does not store all the measured data. For example, the distance between the newly measured data and the data in the stored data buffer is compared. Stores measured data.

In step S3, when a predetermined number of data is accumulated in the data buffer, offset candidates are estimated using the accumulated data group.
In step S4, the reliability of the estimated offset candidate is evaluated. The offset candidates are evaluated by, for example, the variation of the estimated predetermined number of offset candidate groups.
If the variation of the offset candidate group is less than or equal to the predetermined number, the process proceeds to step S5, and if it exceeds the predetermined number, the offset is not updated. For the variation, an index that can express the data distribution may be used. For example, the difference between the maximum value and the minimum value of each axis of the offset candidate group, or the standard deviation of each axis, or the like can be used.
In step S5, the latest offset candidate is adopted as a new offset, and the offset is updated.

  In step S6, when the offset is estimated, geomagnetic data is obtained by subtracting the offset from the measured magnetic data. The azimuth angle is calculated from the geomagnetic data and the installation posture of the mobile device. As the installation posture, a value measured by the inclination angle sensor 9 mounted on the portable device may be used, or a predetermined installation posture such as horizontal may be used.

<Offset estimation when installed in a car>
FIG. 3 shows a flowchart of offset estimation at the time of installation in an automobile.
In this processing, processing by the offset calculation filter unit 2 and the azimuth calculation filter unit 5 is added as compared with the above-described flowchart of offset estimation during walking in FIG.

  In step S10, the offset calculation filter unit 2 in FIG. 1 corrects the triaxial geomagnetic data detected by the triaxial geomagnetic detection unit 1 based on a predetermined reference to obtain offset correction data relating to the offset. Correction data is output to the data sorting selection unit 3.

  In step S11, the azimuth angle calculation filter unit 5 corrects the triaxial geomagnetic data detected by the triaxial geomagnetism detection unit 1 based on a predetermined reference to obtain azimuth angle correction data related to the azimuth. The angle correction data is output to the azimuth calculation unit 6.

  In step 6, the azimuth calculation unit 6 receives the offset stored in the geomagnetic offset storage unit 7, the mobile terminal installation posture data stored in the mobile terminal installation posture storage unit 8, and the azimuth calculation filter unit 5. An azimuth angle is calculated based on the output azimuth angle correction data.

  The other steps can be considered in the same manner as in FIG. 2, and will not be described here.

  Hereinafter, processing by the offset calculation filter, processing by the azimuth calculation filter, and calculation of the azimuth will be further described.

(Processing by offset calculation filter)
The interior of a car is much noisy and large compared to the magnetic environment when walking (depending on the location where the mobile terminal is installed, the car itself is usually located near the instrument panel where a car navigation system is installed. Noise generated to 10 uT (reference value), disturbance noise due to crossing and structures to 100 uT (reference value)). In the method disclosed in Patent Document 1, it is more accurate to estimate the offset using a data group acquired when the mobile terminal moves a large solid angle.

  For this reason, when calculating the offset during walking, the distance between the newly measured data and the data in the offset estimation data buffer is checked before adding the newly measured data to the offset estimation data buffer. As long as the distance is not greater than a predetermined reference value, no new data is added to the data buffer. On the other hand, if the reference value is increased, it becomes difficult to collect data in the data buffer, and it takes time to estimate the offset, and it becomes impossible to follow the offset change due to the magnetization amount of the portable device and the temperature change.

  However, in the case of automobiles, large noise is frequently applied, so even if the automobile does not change its direction, the above-mentioned distance is apparently increased, and only data including noise is stored in the data buffer. An erroneous offset is estimated.

  For the reasons described above, in the case of an automobile, when obtaining an offset, the measured value is not used as it is, but some processing correction (that is, processing by the filter for offset calculation according to the present invention) is performed to remove noise. Is preferably used to estimate the offset.

(Processing by azimuth calculation filter)
Once the offset is calculated, the geomagnetism can be calculated by subtracting the offset from the measured value. The azimuth angle is calculated from the calculated geomagnetism, but for the same reason as the offset calculation, if the measurement value is used as it is, the azimuth angle calculation value fluctuates unnecessarily due to noise.

  Therefore, similarly to the offset calculation filter, noise can be reduced by using some kind of processing correction (that is, processing by the azimuth angle calculation filter according to the present invention).

(Calculation of azimuth)
An example of the calculation of the azimuth will be described.

  FIG. 4 shows a portable device as the azimuth measuring device 100 equipped with the geomagnetic sensor 1 and the tilt angle sensor (acceleration sensor) 9.

  The measurement axis of this portable device is the geomagnetic measurement value (Mx, My, Mz) when the portable device is installed horizontally and northward (measurement X-axis is northward and measurement Z-axis is vertically upwardly aligned). (Obtained by subtracting the offset from the output) is (McosI, 0, −MsinI), where M is the magnitude of geomagnetism and I is the dip angle.

  From this position, as shown in FIG. 5, the measurement Z axis was rotated as θ, and then the measurement Y axis was rotated as α (note that θ and α are in opposite directions). When Mm is measured,

If α is measured by the tilt angle sensor 9, θ can be obtained as follows.
By convention, the azimuth angle is given by -θ.

(Distribution of geomagnetic measurements when installed in a car)
The measured value Mm when the mobile device is installed horizontally (measurement Z-axis coincides vertically upward)

That is, it is distributed in a circle in a plane.
The distribution of the geomagnetic measurement value Mm when the mobile device is installed with a pitch angle φ and a roll angle η and the automobile travels on a horizontal plane is

And distributed on a plane whose normal is (−sin φ, cos φ sin η, cos φ cos η).

The plane may be obtained by measuring φ and η with the tilt angle sensor 9, and if the installation posture in the automobile is determined in advance, the plane may be determined using those values. To determine the plane from the geomagnetic measurements may Atehamere measurements in plane by least squares method.

[Second example]
A second embodiment of the present invention will be described with reference to FIGS. In addition, about the same part as the 1st example mentioned above, the description is abbreviate | omitted and the same code | symbol is attached | subjected.

  This example shows an application example of the above-described offset calculation filter unit 2 of FIG. Here, when a portable device as the azimuth measuring device 100 is installed in an automobile and geomagnetism is measured, three examples are shown as filters suitable for obtaining an offset. Note that the basic configuration of the azimuth measuring apparatus 100 is the same as that shown in FIG. 1, and a description thereof will be omitted here.

  The example of the three filters shown below may be constituted independently or may be arranged in an arbitrary order. In the following description, all the filter inputs are values measured by the geomagnetic sensor 1, but when a plurality of filters are used, the next filter input is the output of the previous filter.

(Change amount limiting filter for offset)
FIG. 6 shows a flowchart of filter processing when the offset calculation filter unit 2 is configured by an offset change amount limiting filter.

  Here, a supplementary explanation of the offset variation limiting filter will be given.

  Unlike walking, it is difficult for a car to change its course rapidly, so the amount of change in geomagnetic measurement values when installed in a car should be small.

  For example, a portable terminal is installed horizontally in an automobile, and the horizontal component of geomagnetism is 30 uT. At this time, if it takes 3 seconds for the car to rotate 90 degrees, it changes only about 10 uT per second. If the measurement period of geomagnetism is set to 100 ms, only about 1 uT changes at successive measurement intervals. The magnetic noise in the automobile in question is 10 uT or more, and if the measurement time interval is not large, the measured magnetic change is much smaller than the noise. Using this, if the measured value fluctuates more than a predetermined value between consecutive measured values, a new measured value is determined by the following formula. If the measured value does not exceed the predetermined value, the measured value is used as it is. . That is,

  When the above method is used, sudden large noise can be eliminated, and there is no output delay unlike a normal linear digital filter. In this case, the filter output changes at the same time when the vehicle changes its course. The absence of output delay is important in azimuth calculation.

FIG. 7 shows changes in the geomagnetic measurement values and the geomagnetic data after filtering.
The actual geomagnetic measurement value is represented as a locus indicated by a solid line connecting the points A1, A2, A3, and A4. On the other hand, the filtered geomagnetic data is represented as a restricted locus indicated by a broken line connecting points B1, B2, and B3.

(Average filter in offset area)
FIG. 8 shows a flow chart of the filter processing when the offset calculation filter unit 2 is configured by an offset intra-area average filter.

  Assume that N representing the number of data input to the filter is initialized to 0 before the measurement is started (before the flow of FIG. 8 is first executed).

  Further, the area defined by the offset average filter threshold dp may be an area surrounded by a cube or an octahedron.

  Here, a supplementary explanation will be given of the offset intra-area average filter.

  In a car, even if the car goes straight or stops, random noise of several μT or more is measured. In order to eliminate such noise, an area having a specific size (hereinafter referred to as a specific area) is set in the measurement value space, and the data in the specific area is averaged and used as one measurement value. . As long as the car is moving straight and the noise is in a specific area, the filter will not output data, the car will bend and the measured value will exit the specific area, and at the same time it will calculate the average value of the data that was in the specific area. Output.

  If a specific area is set to an arbitrary area (for example, a sphere), it is necessary to check whether the measured value is in the specific area, and to calculate the average value, all measured data must be stored. This method requires a large amount of calculation and storage area, and is not suitable for a small system such as a cellular phone.

  An effective and simple method that can avoid the problem of the calculation amount and the storage area is, for example, to make the specific area a cube on the measurement value space (flow of FIG. 8). That is, the maximum value (Xmax, Ymax, Zmax), minimum value (Xmin, Ymin, Zmin) and sum (Xsum, Ysum, Zsum) of each measured value axis (x, y, z) and data existing in a specific area Store the number (N). The new measurement value is compared with the maximum and minimum values, and the maximum and minimum values are updated depending on the result.

  If the difference between the updated maximum value and minimum value is less than or equal to a predetermined value, the measured value is added to the sum and 1 is added to the number of measured values. If the difference between the updated maximum value and minimum value exceeds a predetermined value, that is, the measurement value outside the specific area is acquired, the value obtained by dividing the previous sum by the number of measurement values is used as the filter output. To do.

  Even if the specific region is a cube on the measurement value space, a sufficient effect can be obtained in most cases. However, in order to improve the symmetry in the space, for example, the following 18-hedron may be adopted.

  For the cube, the width of the measured values on the X, Y, and Z axes was examined. In addition, the XY coordinate system was rotated 45 degrees with the Z axis as the rotation axis, and the YZ coordinate system was rotated on the X axis. The coordinate range of the coordinate system rotated 45 degrees as the axis, the coordinate axis of the ZX coordinate system rotated 45 degrees with the Y axis as the rotation axis, and the width of the measured value above are examined. FIG. 10 shows this area. In particular,

Store the maximum value, minimum value, sum, and the number of data existing in a specific area, store the sum until each value exceeds the range of the specified value, If even one is exceeded, the sum may be divided by the number of measured values to calculate the average value and use it as the filter output.

  Alternatively, the widths of the measured values X, Y, and Z and √3 / 3 (X + Y + Z), √3 / 3 (X + Y−Z), √3 / 3 (−X + Y + Z), √3 / 3 (−X + Y−Z) You may examine the width of. FIG. 9 shows this area.

  The output of the filter is not an average value, and any value that represents a specific area may be used. For example, the measurement values may be arranged in order of magnitude for each axis, and the value in the middle rank may be used as the output value (that is, the median value for each axis is the output value).

  The specific area 200 is obtained by first rotating the X axis of the XYZ coordinate system by 45 degrees or 135 degrees about the Z axis as a rotation axis, and arctan (1 / √2) and arctan (-1 / √2) Corresponds to examining the width of the measured values on a total of seven axes, four axes rotated and three axes X, Y, and Z.

In the example of FIG. 9, when the specific region 200 is set to X, Y, Z as the triaxial geomagnetic measurement values,
−D ≦ X, Y, Z, √3 / 3 (X + Y + Z), √3 / 3 (X + Y−Z), √3 / 3 (−X + Y + Z), √3 / 3 (−X + YZ) ≦ D, D > 0
It is an area that satisfies

In the example of FIG. 10, the specific region 201 has a triaxial geomagnetic measurement value of X, Y, and Z.
−D ≦ √2 / 2 (X + Y), √2 / 2 (−X + Y), √2 / 2 (Z + Y), √2 / 2 (−Z + Y), √2 / 2 (Y + Z), √2 / 2 ( −Y + Z) ≦ D, D> 0
It is an area that satisfies

  In an actual application example, the relationship of the above formula is sufficient, but if a more complicated area is to be set, the number of axes for examining the width of the measured value may be increased.

(Plane data selection filter for offset)
FIG. 11 shows a flowchart of filter processing when the offset calculation filter unit 2 is configured by an offset plane data selection filter.

  In step S41, a variation in the distance from a predetermined plane of a data group composed of a predetermined number N (where N is a positive integer) of geomagnetic data continuously detected by the triaxial geomagnetism detection unit 1 is predetermined. It is determined whether it exists within the range, that is, within the plane data selection filter threshold dd.

In step S42, when it is determined that the variation in the distance from the predetermined plane is within the predetermined plane data selection filter threshold dd, the Mth (however, M is a positive integer), and the old data is used as the next output.
In this case, the oldest data in the data group composed of a predetermined number N of geomagnetic data may be used as the next output.

  Here, the offset plane data selection filter will be supplementarily described.

  Since the automobile travels on a substantially horizontal plane, when the geomagnetism is measured with a portable device installed in the automobile, the measured data group is distributed on the plane determined by the installation posture. However, this plane moves in parallel when the magnitude of the geomagnetism and the dip angle fluctuate (the normal direction of the plane does not change). The geomagnetism measured in an area where the magnitude and dip angle (more precisely, declination) is distributed in the same plane, and the data jumping out of the plane can be regarded as data containing noise.

  Using the above processing by the filter, the distance between the predetermined number (N) of measured values and the plane determined by the installation posture is calculated. If the variation in the distance is within a certain value, the predetermined number Assume that the measured value of (N) is reliable. All of a predetermined number (N) of measured values that can be trusted may be output as a filter, or a smaller number of measured values than N may be output.

  For example, one of the oldest data among N reliable measurement values or one of the data corresponding to the median on the time axis is output. The plane determined by the installation posture may be determined from the measurement value of the tilt angle sensor 9 mounted on the portable device, or the measured value may be applied to the plane and the fitted plane may be used. Further, if the installation posture in the automobile is predetermined in use, the plane may be determined from the predetermined installation posture.

[Third example]
A third embodiment of the present invention will be described with reference to FIGS. In addition, about the same part as each example mentioned above, the description is abbreviate | omitted and the same code | symbol is attached | subjected.

  This example shows an application example of the azimuth angle calculation filter unit 5 of FIG. Here, when a portable device as the azimuth measuring device 100 is installed in an automobile and geomagnetism is measured, two examples are shown as filters suitable for obtaining the azimuth. Note that the basic configuration of the azimuth measuring apparatus 100 is the same as that shown in FIG. 1, and a description thereof will be omitted here.

  The examples of the two filters shown below may be configured singly or may be configured in an arbitrary order. In the following description, all the filter inputs are values measured by the geomagnetic sensor 1, but when a plurality of filters are used, the next filter input is the output of the previous filter.

(Azimuth angle variation limiting filter)
FIG. 12 shows a flowchart of the filter process when the azimuth angle calculation filter unit 5 is configured by an azimuth angle variation limiting filter.

(Azimuth angle average filter)
FIG. 13 shows a flow chart of the filter processing when the azimuth angle calculation filter unit 5 is constituted by an azimuth angle area average filter.

  Assume that N representing the number of data input to the filter is initialized to 0 before the measurement is started (before the flow of FIG. 8 is first executed).

  Here, a supplementary description will be given of the azimuth angle average filter.

  The azimuth is usually calculated regularly (usually every geomagnetic measurement period or an integer multiple thereof). If a specific area averaging filter for offset calculation is used, the output does not come out unless the measurement value jumps out of a specific range, so the algorithm needs to be slightly modified. The specific area averaging filter for calculating the azimuth angle outputs the average of the data in the specific area at that time when the geomagnetic measurement value is in the specific area, and when the measurement value pops out, The measured value is output as it is. By applying the above-described filter, an output with reduced noise can be obtained for each measurement of geomagnetism. Also, the output follows the change in the measured value.

It is a block diagram which shows the structure of the azimuth measuring device which is the 1st Embodiment of this invention. It is a flowchart which shows the offset estimation process at the time of a walk. It is a flowchart which shows the offset estimation process at the time of installation in a motor vehicle. It is a perspective view at the time of comprising an azimuth angle measuring device as a portable apparatus carrying a geomagnetic sensor and an inclination angle sensor. It is explanatory drawing which shows the attitude | position with respect to the rotating shaft of a portable apparatus. It is a flowchart which shows the filter process at the time of comprising by the offset variation restriction filter which is the 2nd Embodiment of this invention. It is explanatory drawing which shows the mode of the variation | change_quantity of a geomagnetic measurement value and the geomagnetic data after a filter process. It is a flowchart which shows the filter process at the time of comprising by the area | region average filter for offsets. It is explanatory drawing which shows the area setting example of a specific area. It is explanatory drawing which shows the area setting example of a specific area. It is a flowchart which shows the filter process at the time of comprising by the plane data selection filter for offsets. It is a flowchart which shows the filter process at the time of comprising with the variation | change_quantity restriction | limiting filter for azimuths which is the 3rd Embodiment of this invention. It is a flowchart which shows the filter process at the time of comprising by the area | region average filter for azimuths.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 3-axis geomagnetism detection part 2 Offset calculation filter part 3 Data selection part 4 Offset calculation part 5 Azimuth angle calculation filter part 6 Direction calculation part 7 Geomagnetic offset storage part 8 Portable terminal installation attitude storage part 9 Tilt angle sensor 100 Azimuth Angle measuring device 200, 201 Specific area

Claims (12)

A geomagnetism detecting means for detecting the geomagnetism of each of the three axes;
An offset filter that corrects three-dimensional data obtained based on geomagnetic data of each of the three axes detected by the geomagnetism detecting means based on a predetermined reference and outputs the three-dimensional correction data for offset obtained by the correction. Means,
An azimuth angle obtained by correcting the three-dimensional data obtained based on the geomagnetic data of each of the three axes detected by the geomagnetism detecting means based on a predetermined reference and outputting the three-dimensional correction data for the azimuth angle obtained by the correction. Filter means,
Offset calculating means for calculating an offset based on the offset three-dimensional correction data output from the offset filter means;
Azimuth angle calculating means for calculating an azimuth angle based on the offset calculated by the offset calculation means and the three-dimensional correction data for azimuth angle output from the azimuth angle filter means,
The offset filter means and / or azimuth filter means are:
Change amount limiting means;
First in-region averaging means;
A second in-region averaging means;
Means comprising both the change amount limiting means and the first in-region averaging means;
Means comprising both the change amount limiting means and the second in-region averaging means;
Composed of being selected from the group consisting of
The change amount limiting means determines whether the distance between the three-dimensional data newly input to the change amount limiting means and the three-dimensional data output immediately before by the change amount limiting means is within a predetermined threshold value. Means for determining whether the distance is equal to or less than the predetermined threshold value, and means for outputting the newly input three-dimensional data as the next output; and if the distance exceeds the predetermined threshold value, Means for outputting the next point which is an intermediate point between the three-dimensional data and the latest three-dimensional data and the distance from the immediately preceding three-dimensional data is a predetermined value ,
The first intra-area averaging means includes means for determining whether or not the three-dimensional data newly input to the intra-area averaging means exists in a specific area; and the newly input 3 When it is determined that the dimensional data exists outside the specific area, the average value or median value of the three-dimensional data when the dimensional data exists continuously within the specific area until it is outside the specific area is calculated by the calculation The obtained value is output as three-dimensional correction data, and the three-dimensional data when it is continuously present in the specific area is discarded, and the specific area is regenerated based on the newly input three-dimensional data. Means for setting ,
The second intra-area averaging means includes means for determining whether or not the three-dimensional data newly input to the intra-area average means exists in a specific area, and the newly input 3 Means for calculating an average value or a median value of the three-dimensional data in the specific region when the dimension data is determined to exist in the specific region, and outputting the value obtained by the calculation as three-dimensional correction data; When it is determined that the newly input three-dimensional data does not exist in the specific area, the newly input three-dimensional data is output as three-dimensional correction data, and the three-dimensional data existing in the specific area discards data, the specific region azimuth measuring device comprising a and chromatic child means for resetting on the basis of the three-dimensional data the newly enter.   2. The azimuth angle measuring apparatus according to claim 1, wherein the offset filter means and / or the azimuth angle filter means reduce noise included in the geomagnetic data of the three axes.   The specific area is a closed area centered on a predetermined center point, and the center point is changed by three-dimensional data newly input to the offset filter means and / or the azimuth filter means. The azimuth angle measuring device according to claim 1 or 2.   The azimuth measuring apparatus according to claim 1, wherein the specific region is a region surrounded by a cube or an octahedron. The offset filter means and / or azimuth filter means are:
A predetermined plane of a three-dimensional data group composed of a predetermined number N (where N is a positive integer) of three-dimensional data newly continuously input to the offset filter means and / or azimuth angle filter means Means for determining whether or not the variation in the distance from within a predetermined range;
When it is determined that the variation in distance is within a predetermined range, the Mth (where M is a positive integer) oldest three-dimensional data among the predetermined number N of three-dimensional data groups. 5. The azimuth angle measuring apparatus according to claim 1, further comprising plane data selecting means having means for outputting the following as output. The plane data selection means includes:
6. The azimuth measuring apparatus according to claim 5, wherein the oldest three-dimensional data among the three-dimensional data group composed of the predetermined number N of three-dimensional data is used as the next output. Detecting the geomagnetism of each of the three axes;
An offset filter step of correcting the three-dimensional data obtained based on the detected three-axis geomagnetic data on the basis of a predetermined reference and outputting the corrected three-dimensional data for offset obtained by the correction;
An azimuth filter step for correcting the three-dimensional data obtained based on the detected geomagnetic data of each of the three axes based on a predetermined reference, and outputting the three-dimensional correction data for azimuth obtained by the correction; ,
An offset calculating step of calculating the offset based on the output three-dimensional correction data for offset;
An azimuth calculation step for calculating the azimuth based on the calculated offset and the output three-dimensional correction data for the azimuth;
The offset filter step and / or the azimuth filter step are:
A variation limiting process;
A first in-region averaging step;
A second in-region averaging step;
A step consisting of both the change amount limiting step and the first in-region averaging step;
A step consisting of both the change amount limiting step and the second in-region averaging step;
Composed of being selected from the group consisting of
The change amount limiting step determines whether a distance between the three-dimensional data newly input to the filter and the three-dimensional data output immediately before the filter is within a predetermined threshold; When the distance is less than or equal to the predetermined threshold value, the step of outputting the newly input three-dimensional data as the next output; and when the distance exceeds the predetermined threshold value, the immediately preceding three-dimensional data and the latest And a step of outputting the next point which is an intermediate point with respect to the three-dimensional data and the distance from the immediately preceding three-dimensional data is a predetermined value ,
The first intra-region averaging step includes the step of determining whether or not the three-dimensional data newly input to the filter exists in a specific region; and the newly input three-dimensional data When it is determined that it exists outside the specific area, the average value or median value of the three-dimensional data when it exists in the specific area continuously until it is outside the specific area is calculated, and the value obtained by the calculation is calculated Outputting the corrected three-dimensional data, discarding the three-dimensional data when continuously existing in the specific area, and resetting the specific area based on the newly input three-dimensional data; Have
In the second region averaging step, the step of determining whether or not the three-dimensional data newly input to the filter exists in a specific region; and the newly input three-dimensional data A step of calculating an average value or median value of the three-dimensional data in the specific area when it is determined to exist in the specific area, and outputting the value obtained by the calculation as three-dimensional correction data; When the determined three-dimensional data does not exist in the specific area, the newly input three-dimensional data is output, the three-dimensional data existing in the specific area is discarded, and the specific area is azimuth measuring method characterized that you and a step of re-set based on the newly input three-dimensional data.   8. The azimuth angle measuring method according to claim 7, wherein the offset filter step and / or the azimuth angle filter step is to reduce noise of geomagnetic data of each of the three axes.   The specific area is a closed area centered on a predetermined center point, and the center point changes according to three-dimensional data newly input to the filter. Azimuth measurement method.   The azimuth angle measuring method according to claim 7, wherein the specific area is an area surrounded by a cube or an octahedron. The offset filter step and / or the azimuth filter step are:
Variation in the distance from a predetermined plane of a three-dimensional data group composed of a predetermined number N (where N is a positive integer) of three-dimensional data newly continuously input to the filter is within a predetermined range. Determining whether it exists,
When it is determined that the variation in distance is within a predetermined range, the Mth (where M is a positive integer) oldest three-dimensional data among the predetermined number N of three-dimensional data groups. The azimuth angle measuring method according to claim 7, further comprising a plane data selecting step including: The plane data selection step includes:
12. The azimuth measuring method according to claim 11, wherein the oldest three-dimensional data among the three-dimensional data group including the predetermined number N of three-dimensional data is used as the next output.

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