JPH063148A - Setting method for initial azimuth of azimuth detector - Google Patents

Abstract

PURPOSE:To hold the calculating accuracy of an azimuth before switching to the output of a gyro by setting the initial azimuth without using the output of a terrestrial magnetism sensor if the power source is shut while the magrnetization is not completely corrected yet. CONSTITUTION:A terrestrial magnetic azimuth sensor 1 is a terrestrial magnetism sensor of a flux gate type to detect the horizontal component of force of the terrestrial magnetism by dissolving tone same into components in the Z direction orthogonal to each other. An optical gyro 2 is a highly accurate rate sensor. The optical gyro 2 is so set as to detect the angular velocity in the yaw direction of a vehicle, and calculates the turning angle of the vehicle by integrating the outputs. A/D converters 31-33 are provided with a microcomputer 4 and a memory 5 such as an SRAM etc., backed up by a battery or the like. Therefore, even if the power source of the system is shut, the stored content, can be retained. The accuracy of the azimuth of the terrestrial magnetism is detected by confirming the correcting state of the magnetization when the power source of the vehicle is turned ON. At this time, in the case where the accuracy of the azimuth of the terrestrial magnetism is detected to be low, the initial azimuth is set without using the azimuth of the terrestrial magnetism, so that the accuracy of the azimuth 1 obtained by the optical gyro is not deteriorated.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Conventionally, in a vehicle-mounted navigation system, a plurality of azimuth sensors are used to determine the azimuth in order to improve the calculation accuracy of the traveling azimuth. For example, it is a combination of a geomagnetic direction sensor which is an absolute direction sensor and a two-wheel speed sensor which is a turning angle sensor. Focusing on the turning angle sensor in particular, the development of rate-type gyroscopes has progressed in recent years, and high-precision yaw rate sensors such as optical fiber gyros and gas rate gyros can be used as direction sensors for in-vehicle navigation systems. The direction calculation accuracy has improved. As an example of calculating the direction by combining a geomagnetic direction sensor and a highly accurate yaw rate sensor, there is a current position display device for a moving body disclosed in Japanese Patent Laid-Open No. 58-33283. In this example, a gas rate gyro is used as the yaw rate sensor.However, considering the output stability after the power of the gas rate gyro is turned on, the direction is detected by the geomagnetic sensor when the power is turned on, and the gyro direction is detected after the gyro rise time has elapsed. The direction calculation accuracy was improved by switching to detection.

[0003]

When a high-accuracy yaw rate gyro (hereinafter referred to as a gyro) and a geomagnetic direction sensor (hereinafter referred to as a geomagnetic sensor) are used,
In order to take advantage of the highly accurate trajectory reproducibility of the gyro, it is general to determine the traveling direction of the vehicle by utilizing the gyro output. This means that the azimuth calculated by the geomagnetic sensor includes an error of about ± 5 ° even when the azimuth is stable. On the other hand, the accuracy of turning angle calculation by the high-precision gyro causes, for example, a sensitivity error of about 1% but an offset error. 1-2 ° per hour
This is because the trajectory of the gyro is more stable in the normal traveling state.

However, as in the conventional example, if the orientation is calculated from the geomagnetic sensor only when the power is turned on considering only the stability of the gyro output and the gyro output is switched to the orientation calculation when the gyro output becomes stable, If the previous geomagnetic orientation is not stable, the correct orientation cannot be calculated. For example, the geomagnetic sensor is not susceptible to magnetic disturbances such as elevated roads and bridges, and it is not only necessary to consider the effect of magnetizing the vehicle body, but the accuracy of azimuth calculation is ± 5 ° when compared to a highly accurate gyro. Therefore, there is a problem that the azimuth calculation accuracy before switching to the gyro output cannot be sufficiently secured only by the geomagnetic direction.

[0005]

In order to solve the above problems, the present invention detects a magnetization correction step for correcting the center coordinates of the geomagnetic output circle, a change in the magnetization state of the vehicle, and the end of the magnetization correction. Magnetization determination process, the vehicle state storage process that stores the state of magnetization correction when the vehicle is powered off, and the magnetization correction state that was backed up when the vehicle was powered on The present invention is characterized in that an initial azimuth setting step is provided for setting the initial azimuth without using the output of the geomagnetic sensor when the power is cut off without completing the correction.

As a second means, a post-magnetization elapsed time determination step for determining the elapsed time from the latest change in the magnetized state of the vehicle is provided, and is calculated in the post-magnetization elapsed time determination step when the vehicle power is turned on. When the elapsed time is less than a predetermined value, an initial azimuth setting step for setting an initial azimuth without using the output of the geomagnetic sensor is provided.

Further, as a third means, an azimuth convergence determination step is provided for determining the calculation accuracy of the traveling azimuth initial value and distinguishing the azimuth calculation state into the initial state and the normal state, and it is determined that the azimuth calculation is in the initial state. In this case, a traveling azimuth correction step is provided which takes a larger amount of correction of the traveling azimuth than in the normal state.

[0008]

According to the first means, it can be confirmed when the power is turned on whether or not the magnetization correction is completed when the power of the vehicle is turned off. Therefore, even if the vehicle power is cut off with the magnetization correction unfinished and the center coordinates of the geomagnetic output circle are erroneously stored, and the geomagnetic direction is calculated from the incorrect geomagnetic center when the vehicle is powered on. It is possible to determine whether or not the magnetization correction has been completed, and it is possible to prevent the initial orientation from being set using an incorrect geomagnetic orientation.

According to the second means, it is possible to know the elapsed time from the latest magnetization. Therefore, it becomes possible to determine whether or not the vehicle power was turned on with the geomagnetic center immediately after magnetization being unstable, and it is possible to prevent the initial direction from being set using the unreliable geomagnetic direction. It will be possible.

Further, according to the third means, it is possible to determine the azimuth calculation accuracy after setting the initial azimuth which is a reference for obtaining the traveling azimuth of the vehicle from the high precision gyro. Therefore, when there is some error in the setting of the initial azimuth and the calculation accuracy of the azimuth is low, the correction amount of the azimuth can be increased to make it closer to the true azimuth, and the accuracy of calculation of the traveling azimuth can be improved. It will be possible.

[0011]

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

FIG. 1 shows the basic structure of the azimuth detecting apparatus according to the first embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a fluxgate-type geomagnetic direction sensor, which decomposes and detects horizontal component forces of the geomagnetism into components in 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 integrates the outputs thereof to calculate the turning angle of the vehicle. Reference numerals 31, 32 and 33 are A / D converters, and 4 is a microcomputer. Reference numeral 5 denotes a memory such as SRAM backed up by a battery such as a battery, and the stored contents can be retained even when the system power is turned off. 6 is a CRT
And the like are output means.

The operation of the initial azimuth setting method of the azimuth detecting apparatus of the first embodiment of the present invention constructed as above will be described below. The purpose of the first embodiment is to determine the accuracy of the geomagnetic orientation by checking the state of the magnetization correction when the vehicle power is turned on, and when the accuracy of the geomagnetic orientation is determined to be low, the initial geomagnetic orientation is not used. By setting the azimuth, the accuracy of the azimuth obtained by the optical gyro is not reduced.

FIG. 3 is a flow chart of the azimuth calculation method of the azimuth detecting apparatus in the first embodiment. It is assumed that each variable is initialized before entering this flowchart. First, the outline of the calculation method of the direction using the geomagnetic sensor will be described. The geomagnetic direction is calculated by using a circle in which the geomagnetic output draws a constant radius when the vehicle makes one revolution (this circle is hereinafter referred to as the output circle of the geomagnetic sensor), and is calculated from the angle viewed from the center coordinate of the output circle. At this time, the radius of the output circle represents the magnitude of the horizontal component force of the geomagnetism, and in Japan, it is generally a value of about 300 mGauss (1 G
(Auss is equivalent to 300 mV for a sensor with a sensitivity of 1 V)
Becomes The azimuth is 90 degrees north, with 0 degrees east.
°, west 180 °, south 270 °. Further, the optical gyro output can be converted into a turning angular velocity by multiplying the voltage value acquired by the microcomputer by a predetermined conversion coefficient. By integrating the angular velocity per unit time, the turning angle of the vehicle can be calculated.

First, in step 301, whether or not the contents such as the traveling direction when the vehicle is powered on after the power is turned on, the flag indicating the state of magnetization correction, and the central coordinates of the geomagnetic output circle are stored (backed up) in the memory 5 or not. Find out. Actually, since the memory 5 is a battery-backed SRAM, it can be checked only by looking at the memory contents at a predetermined address. Step 30 if you have a backup
2, and if not, the process proceeds to step 305. In the next step 302, the state of the magnetization correction when the vehicle is powered off is confirmed from the backup contents. If the power is off with the magnetization correction completed, step 30
However, if the power supply is cut off and the accuracy of the geomagnetic direction is lowered while the magnetization correction is not completed, the process unconditionally moves to step 304 and the initial value of the traveling direction is backed up. Adopt the traveling direction. On the other hand, if the magnetization correction is completed when the vehicle is powered off, step 3
However, the geomagnetic direction and the backup direction when the power is turned on are further compared here. This is because the accuracy of the geomagnetic orientation is about ± 5 ° even in a good state, and when the backup orientation is normal, prioritizing the backup orientation improves the orientation accuracy. However, if the geomagnetic direction is calculated from only one sampling data, the accuracy will decrease. Therefore, the direction accuracy will be maintained by statistically (for example, averaging) from a plurality of data when the vehicle is stopped or going straight. Further, for example, 30 ° is adopted as the azimuth comparison reference in step 303, and if the azimuth difference between the two is less than 30 °, the process proceeds to step 304 and the backup azimuth is adopted as the initial value of the azimuth. If the distance is more than 0 °, the reliability of the backup azimuth is low and the geomagnetic azimuth is adopted as the initial value of the traveling azimuth in step 305.
The above steps 301 to 305 correspond to the initial direction setting step.

Next is a process of calculating the traveling direction. Step 3
At 06, the turning direction of the vehicle calculated from the optical gyro is added to the traveling direction to calculate the traveling direction of the vehicle. It is assumed that the calculated traveling direction is stored in the memory in step 307 and that the latest traveling direction is backed up whenever the vehicle is powered off. In the next step 308, it is confirmed whether or not it is the timing of the magnetization correction, and if it is the timing of the magnetization correction, the process proceeds to step 309 to perform the correction, but if not, the process returns to step 306 and the traveling direction The calculation of is repeated. Although the azimuth calculation cycle differs depending on the system, it may be set to a value of, for example, about 100 msec, and the magnetization correction will be advanced in the azimuth calculation cycle.
Whether or not it is the timing of the magnetization correction may be determined by whether or not the vehicle is in a straight traveling state. This has the meaning of improving the calculation accuracy of the geomagnetic data used for the magnetization correction. The above steps 306 to 309 are the traveling direction calculation step.

FIG. 4 is a flow chart showing the detailed processing contents of the magnetization correction in step 309. Note that the magnetization correction in this embodiment uses a magnetization state flag indicating the state of the magnetization correction, and when the center coordinates of the geomagnetic output circle are accurately obtained, the flag (Fmg) is 0 and the magnetization state is If the calculation of the center coordinates is incorrect, the flag (Fm
Let g) represent 1.

First, in step 401, since the vehicle moves straight ahead, the geomagnetic output collected during straight running is averaged to obtain one representative value (representative value of geomagnetism). At that time, the traveling direction is also stored together.
At the next step 402, the magnetizing state flag is confirmed and Fm
If g is 0, the process proceeds to step 403, and if Fmg is 1, the process proceeds to step 407. Step 403,
Reference numeral 404 corresponds to the magnetization determination process.

Although various methods for determining the magnetization have been considered, in this embodiment, the determination is made by utilizing the magnetization tendency of the vehicle body. For example, when the geomagnetic direction sensor 22 is installed on the vehicle body 21 as shown in FIG. 2, when the magnetic field applied in the front-rear direction (travel direction) of the vehicle is detected on the Y axis and the magnetic field applied in the left-right direction of the vehicle is detected on the X axis. To do. Since the geomagnetic direction sensor is fixed to the vehicle body, the positional relationship between the magnetic field detection coil of the geomagnetic direction sensor and the overhead wire does not change, for example, even when passing the railroad crossing, regardless of the road direction. When passing the railroad crossing, the vehicle crosses the overhead wire almost vertically, so that a magnetic field due to the overhead wire is superimposed in the Y-axis direction. The change in the magnetized state of the vehicle body occurs due to 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 in terms of the center coordinates of the geomagnetic output circle, the center coordinates should move in the direction close to the Y axis. become.
From this tendency, when the geomagnetic output is represented on a plane with the two outputs of the geomagnetic direction sensor as two axes, the direction in which the output fluctuates when a magnetic field is applied in the front-back direction of the vehicle on the output plane should be measured beforehand. For example, it is possible to determine whether the magnetized state of the vehicle body has changed.

First, at step 403, the geomagnetic output expected from the traveling direction of the vehicle is calculated. Assuming that the predicted geomagnetic output P is located on the geomagnetic output circle, it is calculated from the center coordinates (Cx, Cy) of the geomagnetic output circle, the radius R of the output circle, and the traveling direction Ac as Mxp = Cx + R × cosAc Myp = Cy + R × sinAc. . Here, since the traveling direction is obtained using the turning angle of the vehicle obtained from the output of the optical gyro, the expected geomagnetic output obtained is not subject to magnetic disturbance. Next, the projection error amount ΔEp is obtained by setting Am (hereinafter, referred to as an expected magnetization direction) to the direction in which the geomagnetic output changes due to the magnetic field applied in the front-rear direction of the vehicle. ΔEp is calculated by the following formula.

ΔEp = (Mx−Mxp) × cosAm +
(My-Myp) × sinAm This projection error amount represents the error amount in the direction in which the center coordinates of the geomagnetic output circle are expected to move due to changes in the magnetization amount of the vehicle body. Details are as shown in FIG. Here, 51 is the output circle of the geomagnetic direction sensor, 52 is the center coordinate of the output circle, 53 is the measured geomagnetic output, and 54 is the predicted geomagnetic output obtained from the traveling direction. At the next step 404, the absolute value of ΔEp is a predetermined value C (for example, 0.2).
It is determined whether the value is larger than R), and when it is larger, it is determined that the magnetized state has changed, the process proceeds to step 405, the magnetized state flag Fmg is set to 1, and the flag is stored. Then, in step 406, the magnetizing correction geomagnetic data and the traveling direction collected when the magnetization state flag Fmg is 0 are deleted, and the process proceeds to step 407. When ΔEp is smaller than the predetermined value C, the magnetization state flag is not changed (Fmg remains 0), and the magnetization correction subroutine is ended. In addition,
Step 405 corresponds to the vehicle state storage process.

At step 407, the representative value of the geomagnetism for magnetization correction is selected. This is a process to be performed because the geomagnetic data used for the magnetization correction will be better if the correction accuracy is improved if the geomagnetic data are gathered evenly in all directions. For example, all directions (360 °) are divided into 8 sections and You only have to select one representative value. As a selection method, the variation of data is statistically obtained from the geomagnetic output when traveling straight, which was used to obtain the geomagnetic representative value in step 401,
The one with the least variation is selected as the representative value. In the next step 408, it is determined whether the magnetization correction is possible. This is determined by, for example, whether the number of azimuth sections for which the representative value has been obtained in step 407 has reached a predetermined number (for example, 4 sections). When the number of azimuth sections is small (for example, when there is only one azimuth section), the accuracy of the magnetization correction does not improve, so the correction is not performed and the magnetization correction subroutine is ended. If the number of azimuth sections has reached a predetermined value or more, it is possible to correct the magnetization, and the process proceeds to step 409 to calculate the geomagnetic center. In this embodiment, a candidate for center coordinates is calculated from the representative value of geomagnetism selected in step 407 and the traveling direction.

Cx '(i) = Mx (i) -Rx cosAc (i) Cy' (i) = My (i) -Rx sinAc (i) The new center coordinates are the candidates (Cx '(i)). , Cy '(i))
It is calculated as the average value of. Above, steps 401 to 4
02, 406 to 409 correspond to the magnetization correction process.

In the next steps 410 and 411, the accuracy of the magnetization correction is determined. First, in step 410, the projection error amount ΔEp (i) is calculated from the geomagnetic representative value used for calculating the new center coordinates and the traveling direction in the same manner as in step 403. Then, ΔEp (i) is signed and averaged to calculate ΔEp-ave. At step 411 Δ
Absolute value of Ep-ave and predetermined value e (for example, 0.1R)
If the absolute value of the average value of the projection error amounts is smaller than a predetermined value, it is determined that the center coordinates have been accurately calculated, and the process proceeds to step 412. However, if it is larger than the predetermined value, Since the magnetization correction has not been completed, the value of the magnetization state flag (Fmg) remains 1 and the correction subroutine is ended. As described above, steps 410 and 411 also correspond to the magnetization determination step like steps 403 and 404.

Finally, in step 412, it is determined that the magnetization correction is completed, the magnetization state flag is reset to 0, Fmg is stored, and the magnetization correction subroutine is ended. Similar to step 405, step 412 corresponds to the vehicle state storage step.

As described above, according to the first embodiment, it is confirmed whether or not the backup information exists when the vehicle is powered on. Then, the flag indicating the magnetization correction state when the power supply was turned off last time is checked, and when the magnetization correction is not completed, the initial value of the traveling direction is determined using only the backup direction without using the geomagnetic direction. Therefore, the accuracy of the geomagnetic direction can be determined when the power is turned on, and the initial value of the traveling direction can be determined without using the geomagnetic direction in which the direction accuracy has deteriorated. Becomes

According to the present embodiment, the magnetized state is determined by using only one representative value of the geomagnetic field. In this case, the projection error amount is calculated by using two or more geomagnetic outputs, and the same projection is performed. It may be determined that the magnetized state has changed only when the error amount is large. Further, the method of calculating the center coordinates of the geomagnetic output circle is not limited to the method of this embodiment, and other methods may be used. For example, a candidate for a new center coordinate is set in the vicinity of the geomagnetic center that has been used until then, and the distance between the geomagnetic output circle and the representative value of each magnetic field when each center candidate is set as a virtual center is obtained. Then, the center candidate having the smallest total sum may be set as a new geomagnetic center. Further, in order to further improve the calculation accuracy of the traveling direction, the traveling direction may be corrected while correlating the traveling locus with the map data.

Next, a second embodiment of the present invention will be described. FIG. 6 shows the basic configuration of the azimuth detecting apparatus according to the second embodiment of the present invention. The basic configuration is almost the same as that of the first embodiment, except that a calendar IC 7 for detecting the time is provided. The calendar IC is backed up by a battery so that the accurate time can be obtained even when the power of the system is turned on.

The operation of the initial azimuth setting method of the azimuth detecting apparatus of the second embodiment of the present invention constructed as above will be described below. Note that the purpose of the second embodiment is to determine the accuracy deterioration of the geomagnetic direction due to the temporal fluctuation immediately after magnetization when the vehicle is powered on, and when it is determined that the accuracy of the geomagnetic direction is low, the initial value is set without using the geomagnetic direction. The purpose is not to reduce the calculation accuracy of the traveling azimuth obtained by setting the azimuth and using the optical gyro.

FIG. 7 is a flow chart of the azimuth calculation method of the azimuth detecting apparatus in the second embodiment. It is almost the same as the flowchart in the first embodiment (see FIG. 3), but steps 702 to 704 are different.
In this embodiment, after confirming in step 702 whether or not the magnetization correction is completed when the power is turned off, if it is completed, the elapsed time from the latest magnetization is obtained in step 703, and the elapsed time is calculated in step 704. Is compared with a predetermined value (for example, 2 weeks). If it is less than the predetermined value, it is determined that the geomagnetic direction is unreliable and the step 7
06, the backup azimuth is adopted as the initial value of the traveling azimuth. This is for the following reason.

FIG. 9 shows an example of changes in the center coordinates of the geomagnetic output circle before and after the vehicle body is largely magnetized. This shows an example in which the magnetic field is magnetized in the Y-axis direction only once under the influence of a large external magnetic field. However, after magnetized, the geomagnetic center is not affected by the external abnormal magnetic field. Often returns to coordinates (hereinafter referred to as demagnetization). The change is exponential as shown in FIG. 9, and the movement converges after a certain amount of time has passed. The method of moving the center coordinates (rate of change, amount of change) varies depending on the vehicle body, but changes greatly immediately after magnetization (for example, 2 to 3 days after magnetization), and the geomagnetic direction is determined using the backup geomagnetic center. When calculated, the geomagnetic orientation will be less accurate. Step 70 to avoid this effect
In Fig. 3, the elapsed time from the latest magnetization time is confirmed when the vehicle power is turned on. Along with this, the processing contents of the magnetization correction subroutine are somewhat changed from the case of the first embodiment shown in FIG. The flowchart is as shown in FIG. 8, and after it is confirmed that the magnetized state is magnetized in step 804, the magnetized state flag is updated and stored in step 805, and then the magnetized time is rewritten to the latest value. The other processing procedure is the same as that of the first embodiment.

As described above, according to the second embodiment, it is confirmed at the time of turning on the power of the vehicle whether or not there is backup information, and if the backup information exists, the time from the latest magnetization time at the time of turning on the power. Ask for time. Therefore, if the elapsed time from the latest magnetization is short, it can be determined that the accuracy of the geomagnetic orientation is likely to have deteriorated due to demagnetization. Since the traveling azimuth of the optical gyro can be determined, it is possible to prevent deterioration of the azimuth accuracy of the azimuth detecting device.

In this embodiment, the magnetizing time is backed up by using the calendar IC and the elapsed time after magnetization is calculated by comparing with the time when the vehicle power is turned on. It is also possible to start the counter backed up by the battery, read the value of the counter when the power of the vehicle is turned on again, and multiply the value by a predetermined conversion coefficient to obtain the elapsed time after magnetization.

Next, a third embodiment of the present invention will be described. The basic structure of the azimuth detecting apparatus of the third embodiment of the present invention is the same as that of the first embodiment and is as shown in FIG.
An object of the present embodiment is to maintain the vehicle traveling azimuth with high accuracy by determining the azimuth setting precision in the initial state particularly when calculating the traveling azimuth of the vehicle using a highly accurate gyro.

FIG. 10 is a flow chart of the initial azimuth setting method of the azimuth detecting apparatus in the third embodiment. Step 1001 is an initial azimuth calculation step. This may be set as in the first embodiment, for example. Next step 1
Although the process proceeds to 002, the traveling azimuth of the vehicle is calculated by integrating the turning angle of the vehicle calculated by the optical gyro with the traveling azimuth initial value set in step 1001 as a reference. This step 1002 corresponds to the traveling direction calculation step.

Next step 1003 and step 1007
From step 1012 to step 1012 correspond to the azimuth convergence determination step. First, in step 1003, it is determined whether the vehicle is in a straight traveling state. This is to judge that the vehicle is in a traveling state from the state of dispersion of the output of the distance sensor or the optical gyro, and if the section turning angle of the optical gyro in the traveling state is within a certain value, it is judged to be a straight traveling state. If the vehicle is in the straight traveling state, the process proceeds to the traveling direction correction process from step 1004 to step 1006, but if it is not the straight traveling state, the process returns to the traveling direction calculation process in step 1002. Here, the azimuth convergence determination process after step 1007 will be described assuming that the correction of the traveling azimuth is completed in the straight ahead state. In step 1007, first, a geomagnetic direction is calculated from a geomagnetic output collected during straight traveling by a statistical method such as an average, a traveling direction during straight traveling is determined, and a straight traveling direction is subtracted from the calculated geomagnetic direction to obtain a direction difference. Remember that value. In the next step 1009, it is determined whether or not the number of stored straight-ahead data is larger than a predetermined value n. If n or less, it is determined that the convergence state of the traveling direction cannot be determined, and the process returns to step 1002. If it is more than n, step 10 is performed.
Move to 09. In step 1009, the average value ΔD of the azimuth difference is calculated from the latest n azimuth differences when going straight. Then, in the next step 1010, it is determined whether or not the absolute value of ΔD is smaller than a predetermined value d.
When it is determined that the traveling azimuth has changed from the initial state to the stable state by moving to 011 and when it is large, the process proceeds to step 1012 and it is determined that the traveling azimuth is still in the initial state. Then, the process returns to step 1002. This criterion is based on the following reasons. When the error of the initial value of the traveling azimuth is larger than a certain amount, it is difficult to return to the true traveling azimuth because the azimuth correction amount is set small because the accuracy of calculating the turning angle of the optical gyro is high. However, since the geomagnetic sensor can calculate the absolute azimuth, it is possible to determine the value of the azimuth error offset to the advancing azimuth by obtaining the difference between the geomagnetic azimuth and the advancing azimuth and observing the transition of the value. At this time, the geomagnetic azimuth has a calculation accuracy of about ± 5 ° even in a straight traveling state, but the accuracy can be improved as the number n of straight traveling data is increased if statistically the error transition is observed over various straight traveling directions. Therefore, as a result, it becomes possible to judge the stability of the traveling direction obtained from the highly accurate gyro.

Finally, the process of correcting the traveling direction will be described. Step 100 is to correct the traveling direction when the vehicle is in a straight traveling state.
It is performed when it is judged in 3. First, in step 1004, it is determined whether the traveling direction is the initial state or the normal state. For this, the results of steps 1011 and 1012 may be used. In the initial state, the process moves to the direction correction I in step 1005, and in the stable state, the direction correction II in step 1006.
Move to. The difference between azimuth correction I and II is the correction amount of the traveling azimuth. Since the traveling azimuth obtained from the optical gyro has a high accuracy in calculating the turning angle, it is better that the correction amount is smaller as it is in the normal state (stable state). However, in the initial state (unstable state), the error cannot be corrected without some correction. Here, it is supposed to be corrected to the geomagnetic direction,
In the normal state, the traveling direction is attracted to the geomagnetic direction by a small amount a in step 1006, and the process returns to step 1002. On the other hand, when the traveling direction is unstable in the initial state, a small amount a
In addition to this, in step 1005, the traveling direction is corrected to the geomagnetic direction by the amount obtained by multiplying the absolute value of ΔD obtained in step 1009 and the difference between d by a constant ratio (1 or less).
Move to 007.

As described above, according to the third embodiment, the traveling direction of the vehicle is obtained by integrating the turning angle of the vehicle obtained by the post-light gyro after setting the initial value of the traveling direction. The setting accuracy of the initial azimuth can be determined based on the difference in the azimuth. Therefore, when the initial azimuth includes a setting error, the azimuth correction amount can be changed to speed up the convergence to the true traveling azimuth, so that it is possible to prevent the azimuth accuracy of the azimuth detection device from deteriorating. .

In this embodiment, the traveling direction and the geomagnetic direction are compared to determine the convergence of the traveling direction, but this is not limited to the comparison with the geomagnetic direction. For example, since this type of azimuth detection device is used to detect the current position of the vehicle using map matching technology or the like, the calculation accuracy of the initial azimuth is determined by comparing the road azimuth in which the vehicle is currently traveling and the traveling azimuth. Alternatively, the history of the vehicle position may be obtained using a positioning means such as GPS, the azimuth of the vehicle may be calculated from the history, and the calculation accuracy of the initial azimuth may be determined by comparing the azimuth obtained from the GPS with the traveling azimuth. .

[0040]

As described above, according to the present invention, when the traveling azimuth is calculated using a high-accuracy gyro, the factor of degrading the accuracy at the time of determining the initial azimuth is eliminated and the calculation accuracy of the initial azimuth is determined. If the accuracy is low, the correction amount of the azimuth can be large. Therefore, it is possible to maintain the traveling azimuth with high accuracy by utilizing the highly accurate turning angle calculation ability.

[Brief description of drawings]

FIG. 1 is a block diagram of a vehicle heading detection device according to a first means of the present invention.

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

FIG. 3 is a flowchart for explaining an azimuth calculating method of the azimuth detecting apparatus according to the first means of the present invention.

FIG. 4 is a flowchart for explaining a magnetization correction method for the geomagnetic direction sensor according to the first means of the present invention.

FIG. 5 is an explanatory diagram of a projection error amount of a geomagnetic direction sensor output in the first means of the present invention.

FIG. 6 is a block diagram of a vehicle azimuth detecting device according to a second means of the present invention.

FIG. 7 is a flowchart for explaining an azimuth calculation method of the azimuth detection apparatus according to the second means of the present invention.

FIG. 8 is a flow chart for explaining a magnetization correction method for the geomagnetic direction sensor according to the second means of the present invention.

FIG. 9 is an explanatory view of the tendency of variation in the center coordinates of the geomagnetic output circle before and after magnetization of the vehicle body in the second means of the present invention.

FIG. 10 is a flowchart illustrating an azimuth calculating method of the azimuth detecting apparatus according to the third means of the present invention.

[Explanation of symbols]

 1 Geomagnetic Direction Sensor 2 Optical Gyro 4 Microcomputer 5 Memory 6 Output Means 7 Calendar IC 21 Car Body 22 Geomagnetic Direction Sensor 31, 32, 33 A / D Converter 51 Geomagnetic Output Circle 52 Geomagnetic Output Circle Center Coordinate 53 Geomagnetic Direction Sensor Output value 54 Expected geomagnetic output

Claims (6)

[Claims] 1. An azimuth detecting apparatus for detecting a traveling azimuth of a vehicle, comprising a yaw rate sensor for calculating a turning angle of the vehicle and a geomagnetic azimuth sensor for decomposing and detecting a horizontal component force of the geomagnetism into components in two directions orthogonal to each other. A traveling direction calculation step of calculating the traveling direction of the vehicle, a magnetization correction step of correcting the center coordinates of the geomagnetic output circle, a magnetization determination step of detecting a change in the magnetization state of the vehicle and the end of the magnetization correction. A vehicle state storage step of storing a state of magnetization correction when the vehicle is powered off detected by the magnetization determination step; and a state of magnetization correction stored in the vehicle state storage step when the vehicle power is turned on. ,
An initial azimuth setting method for an azimuth detecting device, comprising an initial azimuth setting step of setting an initial azimuth without using the output of the geomagnetic azimuth sensor when the magnetization correction is not completed. 2. A post-magnetization elapsed time determination step for determining the elapsed time from the latest change in the magnetized state of the vehicle, wherein the initial azimuth setting step is calculated in the post-magnetization elapsed time determination step when the vehicle power is turned on. The initial azimuth setting method according to claim 1, wherein the initial azimuth is set without using the output of the geomagnetic azimuth sensor when the elapsed time is less than a predetermined value. 3. An azimuth detecting device for detecting an advancing azimuth of a vehicle, comprising a yaw rate sensor for calculating a turning angle of the vehicle, and an initial azimuth setting step for setting an initial value of the advancing azimuth of the vehicle, and calculating an advancing azimuth of the vehicle. And a traveling direction calculation step,
The azimuth convergence determination step of determining the calculation accuracy of the traveling azimuth initial value to distinguish the azimuth calculation state into the initial state and the normal state, and the azimuth convergence determination step in which the calculation accuracy of the traveling azimuth initial value is low and the azimuth calculation is in the initial state. A method for setting an initial azimuth of an azimuth detecting apparatus, comprising a traveling azimuth correcting step for making a larger correction amount of the traveling azimuth when it is determined to be present than in a normal state. 4. The initial azimuth setting method for an azimuth detecting apparatus according to claim 3, wherein the azimuth convergence determining step determines the calculation accuracy of the initial azimuth value by comparing the traveling azimuth and the geomagnetic azimuth. 5. The initial azimuth setting method for an azimuth detecting apparatus according to claim 3, wherein the azimuth convergence determining step determines the calculation accuracy of the initial azimuth value by comparing the traveling azimuth and the road azimuth. 6. The azimuth detection according to claim 3, wherein the azimuth convergence determination step determines the calculation accuracy of the initial azimuth value by comparing the azimuth of the vehicle obtained from the history of GPS positioning positions with the azimuth. How to set the initial orientation of the device.