JP2870258B2 - Magnetization correction method for geomagnetic bearing sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an in-vehicle navigation system for determining a current position of a vehicle and guiding a route to a destination.

[0002]

2. Description of the Related Art As a conventional magnetization correction method for a geomagnetic direction sensor, there is a data processing method for a geomagnetic sensor disclosed in Japanese Patent Application Laid-Open No. 63-158408. In the conventional example, first, an expected geomagnetic output is obtained on the output circle of the geomagnetic azimuth sensor from the traveling azimuth, and an allowable range of the geomagnetic output is set with an error in the angular direction and the radial direction based on the coordinates. When the geomagnetic output does not fall within the allowable range for a predetermined period of time, the center coordinates of the geomagnetic output circle are corrected using the geomagnetic output and the traveling direction.

[0003]

However, in the above configuration, the cause of the geomagnetic output being out of the allowable range is a magnetic disturbance such as an elevated road or a bridge, or a change in the magnetized state of the vehicle. Therefore, when the center coordinates of the geomagnetic output circle are corrected based on the geomagnetic output that is out of the allowable range due to the magnetic disturbance, the calibration accuracy of the center coordinates does not increase.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and to selectively detect a change in a magnetized state of a vehicle and maintain a high accuracy in calculating the center coordinates of an output circle of a geomagnetic direction sensor.

[0005]

In order to solve the above-mentioned problems, the present invention estimates the output of a geomagnetic azimuth sensor from the traveling azimuth of a vehicle, and shortens the output in the direction of the magnetic field applied in the left and right direction of the vehicle with the estimated geomagnetic output as the center. An abnormal data removing step of setting an allowable range of the geomagnetic output long in the direction of the magnetic field applied in the front-back direction and deleting the output when the output of the geomagnetic azimuth sensor is out of the allowable range is provided.

As a second means, an error amount of a geomagnetic output in a direction of a magnetic field applied in the front-rear direction of the vehicle with reference to a geomagnetic output estimated from a traveling direction of the vehicle is calculated.
When the error amount is larger than a predetermined value, a magnetizing determination step is provided for determining that the magnetized state has changed, and when the magnetized state has changed, the output of the geomagnetic azimuth sensor is obtained using only the geomagnetic output obtained after the change. A center coordinate calculation step for calculating the center coordinates of the circle is provided.

As a third means, the output of the geomagnetic direction sensor and the traveling direction of the vehicle are stored in combination, and the geomagnetic output is estimated from the simultaneously stored geomagnetic output and the traveling direction of the vehicle for each stored data. Calculate the error amount in the direction of the magnetic field applied in the front-rear direction of the vehicle based on the estimated output of the vehicle and calculate the average value. It is characterized by including a correction accuracy determining step of determining that the calculated value is calculated.

[0008]

According to the first means, an allowable range is set shorter in the direction of the magnetic field applied in the left-right direction than in the front-rear direction of the vehicle. It is possible to remove the disturbance of the terrestrial magnetism output due to the influence or the elevated road, and to calculate the center coordinates of the output circle of the terrestrial magnetism sensor with high accuracy.

According to the second means, an error amount of the output of the geomagnetic sensor in the direction of the magnetic field applied in the longitudinal direction of the vehicle is calculated based on the geomagnetic output estimated from the traveling direction. Therefore, it is possible to accurately calculate the change in the magnetized state of the vehicle and to extract only the output of the geomagnetic direction sensor collected after the change in the magnetized state. Coordinates can be calculated.

According to the third means, an error amount in the direction of the magnetic field applied in the front-rear direction of the vehicle is calculated for each geomagnetic output used for calculating the center coordinates of the geomagnetic output circle, and the geomagnetic output is calculated from the error amount. Since the calculation accuracy of the center coordinates of the circle can be determined, the center coordinates of the output circle of the geomagnetic azimuth sensor can be calculated with high accuracy.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a basic configuration of an azimuth detecting device common to the embodiments of the present invention. In FIG. 1, reference numeral 1 denotes a fluxgate type terrestrial magnetism azimuth sensor which detects a horizontal component of terrestrial magnetism by decomposing the component into two directions orthogonal to each other. 2 is an optical gyro. This is a high-accuracy rate sensor, which is installed so as to detect the angular velocity of the vehicle in the yaw direction, and calculates the turning angle of the vehicle by integrating its output. Reference numerals 31, 32, and 33 denote A / D converters, 4 denotes a microcomputer, 5 denotes a memory, and 6 denotes output means such as a CRT.

The operation of the method for correcting the magnetization of the terrestrial magnetism sensor according to the first embodiment of the present invention will be described below. The purpose of the first embodiment is to store the output of the geomagnetic azimuth sensor while eliminating the influence of the abnormal magnetic field, and to accurately determine the center coordinates of the geomagnetic output circle.

FIG. 3 is a flowchart of a method for correcting magnetization of the geomagnetic bearing sensor according to the first embodiment. It is assumed that each variable has been initialized before entering this flowchart. First, in step 301, the outputs of the geomagnetic direction sensor and the optical gyro are obtained. In practice, a geomagnetic azimuth sensor outputs two orthogonal components of the horizontal component of the geomagnetism in the form of a voltage value proportional to the strength of the magnetic field, and an optical gyro measures the rotational angular velocity of the vehicle in the yaw direction. Are output as voltage values proportional to the above, the output is obtained by reading the three voltage values into the microcomputer by the A / D converter at predetermined time intervals. The geomagnetic azimuth is calculated using an angle viewed from the center coordinates of the output circle by utilizing the fact that the geomagnetic output draws a circle having a constant radius when the vehicle makes one revolution (this circle is hereinafter referred to as the output circle of the geomagnetic azimuth sensor). . At this time, the radius of the output circle indicates the magnitude of the horizontal component of terrestrial magnetism. The direction is 0 in the east direction, for example.
The degree may be obtained as follows: 90 ° in the north, 180 ° in the west, and 270 ° in the south. The optical gyro output can be converted into a turning angular velocity by multiplying a voltage value acquired by a microcomputer by a predetermined conversion coefficient. Next, at step 302, the traveling direction Ac of the vehicle is calculated. In the initial state, the traveling azimuth of the vehicle may be obtained by accurately obtaining the center coordinate of the geomagnetic output circle by a method such as one round turn and matching with the azimuth obtained from the geomagnetic azimuth sensor, or providing an appropriate initial azimuth. . After that, it is obtained by adding the turning angle obtained by the optical gyro to the traveling direction obtained at that stage. Although the output of the optical gyro is an angular velocity, the turning angle can be calculated by integrating the angular velocity per unit time.
Steps 301 and 302 correspond to the traveling direction calculating step.

Next is an abnormal data removing step. Before that, the tendency of magnetic disturbance to the geomagnetic direction sensor will be described. Suppose that a geomagnetic azimuth sensor 22 is installed on the vehicle body 21 as shown in FIG. 2, and a magnetic field applied in the front-rear direction (traveling direction) of the vehicle is detected on the Y-axis, and a magnetic field applied in the left-right direction of the vehicle is detected on the X-axis. There are many things that give a magnetic disturbance to the geomagnetic direction sensor, but the tendency of the disturbance differs depending on the cause. For example, in the case of running in parallel with a tram, a magnetic field is generated by the current flowing through the overhead wire of the tram, so that the geomagnetic direction sensor detects the sum of the horizontal component force of the geomagnetism and the magnetic field generated by the overhead wire. However, the geomagnetic azimuth sensor is fixed to the vehicle body, and the positional relationship between the magnetic field detection coil of the geomagnetic azimuth sensor and the overhead wire does not change irrespective of the road azimuth as long as the vehicle runs parallel to the tram. That is, since the positional relationship between the overhead wire and the geomagnetic azimuth sensor is constant, in this example, the effect of the magnetic field due to the overhead wire appears in a form in which the magnetic field in the X-axis direction is added to the output due to the horizontal component force of the earth magnetism. Also, in the case of an elevated road, it appears as a phenomenon that the output in the X-axis direction decreases. In the case of a subway, the output often changes in the X-axis direction. On the other hand, when the vehicle crosses a railroad crossing, the vehicle crosses the overhead line vertically, so that a magnetic field due to the overhead line is superimposed in the Y-axis direction. The change in the magnetized state of the vehicle body is caused by the strong magnetic field when passing through the railroad crossing, and occurs almost in the direction in which the strong magnetic field is applied. Therefore, when viewed from the center coordinates of the geomagnetic output circle, the center coordinates move in a direction close to the Y axis. become.

From these tendencies, when the geomagnetic output is expressed on a plane with the two outputs of the geomagnetic azimuth sensor as two axes, the direction in which the output fluctuates when a magnetic field is applied in the front-rear direction of the vehicle on the output plane, If the direction in which the output fluctuates when a magnetic field is applied in the left and right direction is measured in advance, geomagnetic output that has been subjected to magnetic disturbance in a direction perpendicular to the magnetization direction due to factors other than a change in the magnetization state can be eliminated. Become. In the present invention,
Abnormal data is deleted using this tendency.

First, in step 303, the terrestrial magnetic output expected from the heading is calculated using the heading of the vehicle.
Assuming that the predicted geomagnetic output P is located on the geomagnetic output circle, Mxp = Cx + R × cosAc Myp = Cy + R × sinAc from the center coordinates (Cx, Cy) of the geomagnetic output circle, the radius R of the output circle, and the traveling direction Ac. . Here, since the traveling azimuth is obtained using the turning angle of the vehicle obtained from the output of the optical gyro, the obtained predicted geomagnetic output is not subjected to magnetic disturbance. Next, in step 304, an allowable range is set. In the present embodiment, the direction in which the major axis changes with the magnetic field applied in the front-rear direction of the vehicle around the predicted geomagnetic output P calculated from the traveling direction (the direction is assumed to be Am, hereinafter referred to as the predicted magnetization direction). The rectangle should be Details are as shown in FIG. Here, 41 is the output circle of the geomagnetic bearing sensor, 4
2 is the center coordinate of the output circle, 43 is the measured geomagnetic output,
Reference numeral 44 denotes an expected geomagnetic output obtained from the traveling direction. As for Am, an appropriate value may be selected by, for example, previously measuring characteristics when the combination of the vehicle and the geomagnetic azimuth sensor is determined as described above. Assuming that the lengths of one side of the short axis and the long axis of the allowable range are La and Lb, for example, La = 0.4
R and Lb may be set to 3R. In step 305, it is determined whether or not the geomagnetic output M is included in the rectangular allowable area set in step 304. This determination may be made in a coordinate system in which the anti-magnetization output P is used as the center and the anti-magnetization direction is rotated in the reverse direction (clockwise rotation). Actually, ΔX = (Mx−Mxp) × cosAm + (My−Myp) × sinAm ΔY = − (Mx−Mxp) × sinAm + (My−Myp) × cosAm, and abs (ΔX) <Lb and abs (ΔY ) If <La, it is determined that it is included in the area. If the geomagnetic output M is within the allowable range, the process proceeds to step 306. If not, the geomagnetic output M is determined to be abnormal data and is deleted, and the process returns to step 301. Steps 303 to 305 are the abnormal data removal process.

In step 306, the output coordinates and traveling direction of the geomagnetic output M determined to be not abnormal data are stored. This step 306 corresponds to an output value storage step.

Finally, in step 307, the center coordinates of the geomagnetic output circle are calculated. In this embodiment, first, step 306 is executed.
A candidate for the center coordinate is calculated from each of the geomagnetic outputs and the traveling azimuths stored in step (1).

Cx ′ (i) = Mx (i) −R × cosAm (i) Cy ′ (i) = My (i) −R × sinAm (i) The new center coordinates are those candidates (Cx ′ (i) , Cy '(i))
Calculated as the average value of When the center coordinates are updated, the process returns to step 301 to repeat the processing.

As described above, according to this embodiment, the heading is calculated using the turning angle of the vehicle obtained from the optical gyro which is not affected by magnetic disturbance, and the geomagnetic output expected from the heading is calculated. Is estimated. Then, a rectangular geomagnetic output allowable range that is long in the magnetization direction expected from the estimated output and short in the direction perpendicular to the magnetization direction is set.
Therefore, in a section where geomagnetic disturbance is large, such as a case where an elevated road continues or parallel to a tram, data can be deleted by regarding the geomagnetic output as abnormal. Therefore, since the center coordinates of the geomagnetic output circle are calculated only from geomagnetic data having no bias, the center coordinates of the geomagnetic output circle can be maintained with high accuracy.

In this embodiment, the traveling azimuth of the vehicle is obtained by adding the optical gyro turning angle to the reference azimuth utilizing the accuracy of the optical gyro turning angle calculation accuracy, but the traveling azimuth accuracy is further improved. Therefore, the traveling direction may be corrected while correlating the traveling locus with the map data. Also, the allowable range of the geomagnetic output is a rectangle whose major axis is parallel to the expected magnetization direction with the geomagnetic output expected from the traveling direction as the center, but this may be made such that the length of one side can be changed depending on the traveling direction, Instead of a rectangle, it may be an ellipse whose major axis is parallel to the expected magnetization direction.

Next, a second embodiment of the present invention will be described. FIG. 5 is a flowchart of a magnetization correction method for the geomagnetic azimuth sensor according to the second embodiment. The purpose of this embodiment is to accurately maintain the center coordinates of the geomagnetic output circle by accurately determining the change in the magnetized state of the vehicle body.

Steps 501 and 502 are equivalent to steps 301 and 302 of the first embodiment, and correspond to a traveling azimuth calculation step of calculating the traveling azimuth of the vehicle by obtaining the outputs of the geomagnetic azimuth sensor and the optical gyro. If the geomagnetic output can be obtained and the heading can be calculated, the next step 50
Then, the process goes to 3 to store the geomagnetic output M and the traveling direction Ac.

In the next step 504, a projection error amount ΔEp as a guide for determining whether or not the magnetized state of the vehicle has changed.
Is calculated. The method of calculating the projection error amount ΔEp is as shown in FIG. First, the center coordinates (Cx, Cx) of the geomagnetic output circle
The predicted geomagnetic output P is calculated from y), the radius R of the output circle, and the traveling direction Ac.

Mxp = Cx + R × cosAc Myp = Cy + R × sinAc Then, the projection error amount ΔEp is obtained from the stored geomagnetic output M (Mx, My) and the expected magnetization direction Am as follows.

ΔEp = (Mx−Mxp) × cosAm + (My−Myp) × sinAm The projection error amount is an error amount in a direction in which the center coordinate of the geomagnetic output circle is expected to move due to a change in the magnetization amount of the vehicle body. Represents In the next step 505, it is determined whether or not the absolute value of ΔEp is larger than a predetermined value C (for example, 0.2R). When it is larger, it is determined that the magnetization state has changed, and in step 506 old storage data is deleted. The process proceeds to step 507 assuming that the magnetized state does not change. Then, the center coordinates are calculated from the geomagnetic output and the traveling direction stored in step 507. The calculation method is the same as step 307 of the first embodiment. When the new center coordinates have been calculated, the process returns to step 501 to repeat the processing. Steps 503 and 506 correspond to the output value storage step, steps 504 and 505 correspond to the magnetization determination step, and
7 corresponds to a center coordinate calculation step.

As described above, according to this embodiment, the vehicle is magnetized based on the magnitude of the error amount of the collected geomagnetic output in the expected magnetization direction with reference to the center coordinates of the geomagnetic output circle that is currently obtained. Detect changes in state. Therefore, it is possible to accurately determine the change in the magnetized state, and when the magnetized state changes, it is possible to extract only the geomagnetic output collected after the change, so that the output of the highly accurate geomagnetic direction sensor can be obtained. The center coordinates of the circle can be calculated.

According to the present embodiment, the determination of the magnetized state is performed using only one geomagnetic output, but this is done by calculating the projection error using two or more geomagnetic outputs, and similarly calculating the projection error. It may be determined that the magnetized state has changed only when the amount is large.

Next, a third embodiment of the present invention will be described. FIG. 7 is a flowchart of a magnetization correction method for a geomagnetic bearing sensor according to the third embodiment. An object of the present embodiment is to determine the calculation accuracy of the center coordinates of the geomagnetic output circle and maintain the center coordinates with high accuracy.

Steps 701 to 703 are the same as steps 501 to 503 of the second embodiment.
3 corresponds to an output value storage step. In the next step 704, the center coordinates of the geomagnetic output circle are calculated from the stored geomagnetic output and traveling direction. This is step 3 of the first embodiment.
Same as 07.

In the next steps 705 and 706, the accuracy of magnetization correction for calibrating the center coordinates of the geomagnetic output circle is determined using the newly obtained center coordinates of the geomagnetic output circle and the stored data. First, in step 705, the projection error amount ΔEp (i) is calculated for each of the combinations of all stored geomagnetic outputs and traveling azimuths in the same manner as in step 504 of the second embodiment. Then, the average value ΔEp-ave is calculated from the obtained projection error amounts. In the next step 706, the absolute value of the average value is compared with a predetermined value (for example, 0.1R), and if the absolute value of the average value of the projection error is smaller than the predetermined value, the center coordinate is calculated with high accuracy. The process returns to step 701, but if it is larger than the predetermined value, the process proceeds to step 707 to correct the center coordinates. Correction of the center coordinates is performed in step 70
Center coordinates (Cx, Cy) of the geomagnetic output circle obtained in 4
And the average value ΔE of the projection error amounts obtained in step 705
This is performed as follows using p-ave.

Cx ← Cx + ΔEp−ave × cosAm Cy ← Cy + ΔEp−ave × sinAm After the center coordinates are corrected, the process returns to step 701 to repeat the process. Steps 704 and 707 correspond to a center coordinate calculation step, and steps 705 and 706 correspond to a correction accuracy determination step.

As described above, according to the third embodiment, a projection error amount of each geomagnetic output in the expected magnetization direction is obtained by using the stored geomagnetic output and the traveling direction at the time of collecting the geomagnetic output. It is determined whether or not the center value of the geomagnetic output circle has been calculated with high accuracy using the average value. When the accuracy is not sufficient, the center coordinates can be corrected, so that the accuracy of calculating the center coordinates of the geomagnetic output circle can be kept high.

[0035]

As described above, according to the present invention, the correlation between the direction of the magnetic disturbance determined by the state of attachment of the geomagnetic direction sensor to the vehicle and the moving direction of the geomagnetic output circle due to the change in the state of magnetization is used. The change of the magnetized state of the vehicle and the magnetic disturbance are selected, and the center coordinates of the output circle of the geomagnetic azimuth sensor are automatically corrected on the basis thereof, so that the calculation accuracy of the center coordinates can be maintained with high accuracy. .

[Brief description of the drawings]

FIG. 1 is a block diagram of a vehicle direction detecting device common to the present invention.

FIG. 2 is an explanatory diagram of the installation relationship between a vehicle and a geomagnetic direction sensor.

FIG. 3 is a flowchart illustrating a method for correcting magnetization of a geomagnetic azimuth sensor according to a first embodiment of the present invention;

FIG. 4 is an explanatory diagram of an allowable range of an output of a geomagnetic direction sensor in the first means

FIG. 5 is a flowchart for explaining a magnetization correction method for a geomagnetic azimuth sensor according to a second means of the present invention;

FIG. 6 is an explanatory diagram of a projection error amount of an output of a geomagnetic azimuth sensor in the second means.

FIG. 7 is a flowchart illustrating a method for correcting magnetization of a geomagnetic bearing sensor according to a third means of the present invention.

[Explanation of symbols]

 Reference numerals 1, 22 Geomagnetic direction sensor 2 Optical gyro 4 Microcomputer 5 Memory 6 Output means 21 Body 31, 32, 33 A / D converter 41 Geomagnetic output circle 42 Center coordinate of geomagnetic output circle 43 Output value of geomagnetic direction sensor 44 Expected geomagnetism Output 45 Allowable range of geomagnetic output

Claims (4)

(57) [Claims] An azimuth detecting device for detecting a traveling azimuth of a vehicle, comprising a geomagnetic azimuth sensor for decomposing and detecting the intensity of terrestrial magnetism into components in two directions orthogonal to each other, and calculating a traveling azimuth of the vehicle. The calculating step, the output of the geomagnetic direction sensor is estimated from the traveling direction of the vehicle obtained in the traveling direction calculating step, and an allowable range of the geomagnetic output is set centering on the estimated geomagnetic output, and the output of the geomagnetic direction sensor is calculated. An abnormal data removing step of removing the output when the output is outside the allowable range; an output value storing step of storing the geomagnetic direction sensor output determined to be included in the allowable range of the geomagnetic output in the abnormal data removing step; A center coordinate calculating step of calculating center coordinates of a geomagnetic output circle from the geomagnetic direction sensor output stored in the value storage step. Magnetized correction method of the capacitor. 2. The method according to claim 1, wherein the allowable range of the abnormal data removing step is a rectangle in which the direction of the magnetic field applied in the left-right direction is shorter than the front-rear direction of the vehicle. 3. An output of a geomagnetic azimuth sensor is estimated from a traveling azimuth of a vehicle instead of an abnormal data removing step, and an output of the geomagnetic azimuth sensor in a direction of a magnetic field applied in the front-rear direction of the vehicle based on the estimated geomagnetic output is used. The apparatus further includes a magnetization determination step of calculating an error amount and determining a change in a magnetization state of the vehicle based on the magnitude of the error amount, and the output value storage step determines that the magnetization state of the vehicle has changed in the magnetization determination step. 2. The method according to claim 1, wherein the stored data before the change of the magnetized state is deleted. 4. The output value storing step is for storing the output of the geomagnetic direction sensor and the traveling direction of the vehicle. In place of the abnormal data removing step, the output value storing step is performed based on the traveling direction of the vehicle stored in the output value storing step. The output of the azimuth sensor is estimated, and the accuracy of calculating the center coordinates of the output circle of the azimuth azimuth sensor is determined from the error amount of the stored terrestrial magnetic sensor output in the direction of the magnetic field applied in the front-rear direction of the vehicle based on the estimated terrestrial magnetic output. 2. The method according to claim 1, further comprising the step of determining a correction accuracy.