JPH02198314A - Magnetic-bearing detecting apparatus - Google Patents

Abstract

PURPOSE:To compute accurate magnetic bearings by providing a sampling-time operating means, a rotary-angle operating means and a magnetism correcting amount operating means. CONSTITUTION:Each pulse of a wheel speed signal which is detected with a wheel sensor is counted in counters 13 and 14. A sampling time operating means 151 generates a sampling signal for temporarily keeping the detected signal of a geomagnetism sensor in sample/hold circuits 16 and 17 for every time an automobile runs on a predetermined running distance. The counted values from the counters 13 and 14 are also inputted into a rotary-angle operating means 152. The changing amount of the angle in the advancing direction of the automobile is computed when the automobile runs on the predetermined distance. A rotary angle DELTAtheta counted in the means 152 is transferred into a magnetism-correcting-amount operating means 153 and compared with the minimum rotary angle which is a reference for judging the fact that the automobile starts turning. When the rotary angle DELTAtheta becomes higher than the minimum rotary angle, the running distance of the wheel is accumulated until the rotary angle which is transferred from the means 152 becomes less than the minimum value.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a magnetic orientation detection device that detects the direction of a magnetic field, and more specifically, it is capable of correcting detection errors caused by a magnetic field magnetized in a magnetic orientation detection device, etc. The present invention relates to a magnetic direction detection device.

A conventional magnetic direction detection device is suitably used in a navigation system for a car that guides a route from a starting point to a destination point, and detects the direction of the earth's magnetic field. As this magnetic detection device, for example, a fluxgate type geomagnetic sensor detects and outputs magnetic components of the geomagnetism in directions perpendicular to each other at an installed position. From the ratio of magnetic components in the perpendicular direction, the angle between magnetic north and the installation position of the geomagnetic sensor (
(hereinafter referred to as "magnetic azimuth") can be calculated. The navigation system determines the traveling direction of the vehicle corresponding to the magnetic azimuth based on the output signal of the geomagnetic sensor, and instructs the route to the destination point on a map displayed on a cathode ray tube, for example.

This geomagnetic sensor can accurately detect the direction of geomagnetism in an environment where there is no disturbance magnetic field. However, when this geomagnetic sensor is mounted on a vehicle or the like and used, disturbance magnetic fields caused by magnetic fields magnetized to the vehicle body etc. cause errors in the direction of the detected geomagnetism. When such errors exist, for example, in a navigation system, the errors are accumulated, making it difficult to accurately guide the vehicle to the destination point.

Therefore, when calculating the magnetic azimuth by detecting the disturbance magnetic field caused by the magnetic field magnetized by the geomagnetic sensor itself or the vehicle body, a correction calculation is performed to cancel the error caused by the disturbance magnetic field. , a means for calculating accurate magnetic azimuth has been proposed.

FIGS. 8 and 9 show omnidirectional detection reference patterns for explaining a method for correcting detection signals output from magnetized geomagnetic sensors according to the prior art. First, geomagnetic sensors in a non-magnetized environment The output state of the detection signal will be explained. Let the output voltages of the detection signals of mutually orthogonal magnetic components of the geomagnetic sensor be V and ■2, and the output voltages V, , V, when the geomagnetic sensor is rotated 360 degrees with the vertical direction as the center axis, are plotted on the coordinate axes. When plotted.

A trajectory 91 is obtained by rotating the vector A once on the coordinate axis.

However, if a magnetic field magnetized by a vehicle body or the like exists, an error occurs in the magnetic azimuth. If the magnetic vector of the disturbance magnetic field due to this magnetization is P, the detection signal output from the geomagnetic sensor is the composite vector B of vector A and vector P.
Then, if the geomagnetic sensor is rotated 360'' in the same way, the composite vector B becomes the locus 92. Therefore, the magnetic azimuth angle calculated from the composite vector B is θ6, and it is detected in an environment where there is no disturbance magnetic field. The azimuth deviates by an angle φ with respect to the magnetic azimuth θ found from the vector A.

Therefore, as a means for correcting the azimuth deviation angle φ due to this magnetization, Japanese Patent Laid-Open Nos. 58-135911 and 5
It is disclosed in Japanese Patent No. 9-451300. These publications state that a vehicle equipped with a geomagnetic sensor is rotated while driving or at an appropriate point, changing direction to the east, west, south, or north, and as a result, the geomagnetic sensor is rotated 360 degrees around the vertical direction. By using it as a correction value when calculating the trajectory position detected by the rotation,
A means for calculating accurate magnetic azimuth angles is disclosed.

Further, another means is disclosed in Japanese Patent Laid-Open No. 61-269014. According to the content disclosed in this publication, when magnetization is caused by one magnetization as shown in Figure 9, the output voltage of mutually orthogonal magnetic components output from the geomagnetic sensor is expressed by the first equation and the second equation. It will be done.

Next, by differentiating both sides of the first and second equations with respect to θ, we get the third
and the fourth equation are obtained.

Then, by taking the difference between both sides of the first equation and both sides of the fourth equation, the fifth equation is obtained, and by taking the sum of both sides of the second equation and both sides of the third equation, the sixth equation is obtained. .

As shown in the fifth and sixth equations, the vector G due to magnetization can be calculated based on the output voltage of the geomagnetic sensor and the value obtained by differentiating the output voltage with respect to the rotation angle θ. Therefore, by using the magnetic component based on the calculated magnetization as a correction amount in the calculation of the magnetic azimuth, it is possible to accurately calculate the magnetic azimuth.

Problems to be Solved by the Invention In the former magnetic correction described above, when a geomagnetic sensor is mounted on a car, it is necessary to rotate the direction of travel of the car by 360 degrees on the way from the starting point to the destination point. In order to constantly and accurately perform magnetic azimuth correction calculations, it is necessary to periodically repeat the above operations while driving toward the destination. It can be said that this is an extremely difficult task for many people and is unrealistic.

In addition, in the magnetic correction of the driver, it is necessary to differentiate the detection signal of the geomagnetic sensor with respect to the angle θ, which is the rotation angle of the car. There is a risk that an error may occur, and the error may actually increase the error in the magnetic azimuth angle. In particular, when a geomagnetic sensor is installed in a car, the angle θ is determined from the difference in the rotation amount of the wheel speed sensors attached to the left and right wheels of the car, so the error of one gear of the wheel speed sensor is In order to cause an error in the calculation of the above differential value,
This method has a problem in that it is not possible to calculate an accurate amount of magnetic correction.

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic azimuth detection device that can always detect an accurate magnetic azimuth angle by simple correction calculations.

Means for Solving the Problems The present invention provides magnetic detection means for detecting two magnetic components in directions perpendicular to each other; a rotation angle detection means for detecting that the rotation has been made by the above rotation angle; magnetic correction amount detection means for detecting a magnetic component that does not change due to rotation of the detection means; magnetic azimuth detection means for detecting a magnetic azimuth from an output of the magnetic correction amount detection means and an output of the magnetic detection means; A magnetic direction detection device characterized by including:

Function In the present invention, when the magnetic detection means divides the magnetic field in the space in which the magnetic detection means is placed into mutually perpendicular components, the zero rotation angle detection means detects these two magnetic components. It is detected that the sensor has rotated by a predetermined angle or more about the central axis in a direction perpendicular to any direction of the magnetic component to be detected. When the magnetic detection means is rotated by the rotation angle detection means beyond the predetermined angle,
The magnetic correction amount detection means detects a magnetic component that does not change due to the rotation of the magnetic detection means from the detection signal of the magnetic detection means before and after rotation by a predetermined angle. Then, the magnetic azimuth detecting means detects the magnetic azimuth of the magnetic detecting means from the magnetic component detected by the magnetic correction amount detecting means and the detection signal of the magnetic detecting means when rotated by a predetermined angle.

Embodiment FIG. 1 is a block diagram of a case where a magnetic direction detecting device according to an embodiment of the present invention is mounted on an automobile.

Hereinafter, a case will be described in which the traveling direction of a vehicle is detected by the magnetic direction detecting device. The processing circuit 1 calculates the magnetic azimuth, which is the traveling direction of the automobile, based on the detection signals of the geomagnetic sensor 2 and the wheel speed sensors 3 and 4, and displays the magnetic azimuth on the display device 5.

The right wheel speed sensor 3 and the left wheel speed sensor 4 output the rotation of a detection plate having a sawtooth circumference fixed to the axle as a wheel speed signal proportional to the rotational speed of the axle using an optical pickup or a magnetic pickup. Waveform shaping circuit 11.1
Output to 2. The detection signal from which noise components have been removed and whose signal waveform has been shaped by the waveform shaping circuit 11.12 is sent to a counter 13.14, where the number of revolutions of each axle is counted.

Arithmetic circuit 15 composed of a microcomputer, etc.
calculates the travel distance of the vehicle and the angular change in the direction of travel of the vehicle from the count values counted by the counters 13 and 14. From this calculated mileage of the car,
Every time the car travels a predetermined distance, the signal line s
11, the sampling signal is sent to a sample hold circuit 1617. The sample hold circuit 16°l7 temporarily holds the detection signal output from the geomagnetic sensor 2, and the detection signal converted from an analog signal to a digital signal by the A/D conversion circuit 18, 19 is sent to the arithmetic circuit 15. Ru.

The arithmetic circuit 15 calculates the relationship between the traveling direction of the vehicle and magnetic north based on the detection value detected by the geomagnetic sensor 2, the travel distance of the vehicle calculated from the wheel speed sensors 3 and 4, and the angle at which the traveling direction has changed. A magnetic azimuth, which is an angle, is calculated, and the magnetic azimuth is displayed on the display device 5.

The geomagnetic sensor 2 is, for example, a fluxgate type magnetic sensor, and has an excitation coil 21 wound around a doughnut-shaped core 22, as shown in FIG. Further, detection coils 23 and 24 are wound on the core 22 at right angles to each other.

The excitation coil 21 is given an excitation signal of several hundred kHz to the number output from the oscillation circuit 25 to generate an alternating magnetic field in the direction of the central axis of the core 22 . A voltage is induced in the detection coil 23.24 by this alternating magnetic field, and after the voltage is converted into a detection signal by the voltage detection circuit 26.27,
It is output to the sample and hold circuits 16 and 17 of the processing circuit 1.

When geomagnetism, which is an external magnetic field, exists in the geomagnetic sensor 2,
The mutually orthogonal component magnetic fields of the earth's magnetism are superimposed on the magnetic field generated by the excitation coil 21. Therefore, the voltage detection circuits 26 and 27 output detection signals V, , V, which are proportional to the strength of the superimposed magnetic field.

This detection voltage ■0. The magnetic azimuth angle θ can be calculated by calculating the seventh equation based on (2).

■.

θ=　arctan-・” (7) ■.

Next, a calculation for removing a signal component based on a magnetic field generated by magnetization of the vehicle body from the detection signal of the geomagnetic sensor 2 will be explained. FIG. 3 is an omnidirectional detection reference pattern for explaining the principle of magnetic correction in this embodiment. In FIG. 3, when the detected voltage 1 of the voltage detection circuit 26 is shown on the horizontal axis and the detected voltage 1 of the voltage detection circuit 27 is shown on the vertical axis,
Geomagnetic sensor 2 in the presence of a magnetic field caused by magnetization at 360
If the detected voltage when rotated by degrees is represented on a graph, it becomes a locus 31. Here, it is an amount that does not change due to the rotation of the air sensor 2 generated by magnetization.

The center S of the circle represented by the trajectory 31"C" is considered to be the amount by which the trajectory 31 is shifted by the magnetic field due to magnetization.

Therefore, in order to correct the magnetism due to magnetization, it is necessary to subtract each component of the center S, which is a magnetic field component due to magnetization, from the detection signal of the geomagnetic sensor 2.

Therefore, the magnetic correction amount is determined from the detection signals of the voltage detection circuits 26 and 27 at positions Ii indicating two different magnetic azimuths of the geomagnetic sensor 2. That is, in FIG. 3, the geomagnetic sensor 2 is at the position "IP+(V-+).

■, Assuming that the magnetic azimuth changes from 1) to P * (Vmx, VF2), the coordinates (V, , , V, ,) of the midpoint Q between position 1p+ and position it P2 can be found by equation 8. It will be done.

Furthermore, the slope a of the straight line connecting the midpoint Q and the center S is determined by Equation 9.

Vml V++1 ”” VFI-V,! ...
(9) Therefore, the angle θ. is obtained from Equation 10.

θ, = arctan (a)
-(10) Here, the length between the center S and the midpoint Q is α1, the length between the point P1 and the midpoint Q is β, and further l
When P IS P * is θ, the length α is obtained from Equation 11.

Furthermore, since the length β is half the distance between the points P1 and P2, it is calculated by Equation 12.

β=-・ (v,,-v,□) ”+ (Vy+-Vy
z) 2 ... (12) The locus of the midpoint Q calculated above all (V,..., Vyz), the length α, and the angle θ. The coordinates (V, , , V, .) of the center S of the trajectory 31 are calculated from Equation 13.

In this way, the geomagnetic sensor 2 is moved from the point P1 to the point P2.
The coordinate of the center S of the locus 31 (■□81 Vlm>m, that is, the magnetic correction amount) can be determined from the detection signal at that time.

Once the coordinates (V, , V□) of the center S are determined, the corrected magnetic azimuth angle θ is calculated from Equation 14.

Therefore, the corrected magnetic azimuth θ is the geomagnetic sensor 2
It is calculated by determining the respective detection signals and the angle change amount θ1 of the geomagnetic sensor 2 when indicating two different magnetic azimuth angles.

The calculation operation in the calculation circuit 15 that performs the correction calculation of the magnetic azimuth angle described above will be explained below.

FIG. 4 is a functional block diagram for explaining the processing contents in the arithmetic circuit 15 of this embodiment. Wheel speed sensor 3,
Each pulse of the wheel speed signal detected by 4 is counted by a counter 13,14. The sampling time calculation means 151 generates a sampling signal for temporarily holding the detection signal of the geomagnetic sensor 2 in the sample hold circuit 1617 every time the vehicle travels a predetermined distance Δ1rrl based on the counts of the counters 13 and 14. occurs.

The count values counted by the counters 13 and 14 are inputted to the rotation angle calculation means 152, and the amount of angular change (
Hereinafter referred to as "rotation angle". ) is calculated. Here, the principle of calculating the travel distance and rotation angle of the automobile based on the counts of the counters 13 and 14 will be explained with reference to FIG.

It is assumed that the right deciding wheel 3a and the left rear wheel 4a move forward and reach the positions of the right rear wheel 3b and the left rear wheel 4b. The distance traveled by a car is considered to be the distance traveled by the center between both wheels, so the distance Δ
l is the distance traveled by the car. Therefore, the traveling distance Δl of the car is the distance actually traveled by the right rear wheel 3a.
Assuming that the distance actually traveled by the left rear wheel 3a is ΔIL, it is calculated by Equation 15.

Δl=Δl・+Δp・2 (15) Also, regarding the rotation angle Δθ, the running radius of the right rear wheel 3a is R15,
If the running radius of the left rear wheel 4a is R2, the running distances of the right rear wheel 3a and the left rear wheel 4a are calculated using equations 16 and 17, respectively.

R1・Δθ=Δ18
...(16) R2・Δθ=ΔIL
(17) By subtracting both sides of Equation 16 from both sides of Equation 17, Equation 18 is obtained.

[2-Rl)・Δθ=ΔIL−Δ1. l
(18) (R2-R1) is the distance between both wheels, that is, the tread width, and if this distance is T, then the rotation angle Δθ is calculated from the 19th.

Δθ=ΔI・−Δl・T (19) As described above, the sampling time calculation means 151 calculates the formula 15, and when the predetermined travel distance reaches 1 m, it generates a sampling signal and also calculates the rotation angle. Arithmetic means 152
calculates the rotation angle Δθ from Equation 19.

The rotation angle Δθ calculated by the rotation angle calculation means 152 is transferred to the magnetic correction amount calculation means 153, and is used as the minimum rotation angle θII, which is a reference for determining that the automobile has started rotating.
One rotation angle Δθ compared with LIM is the minimum rotation angle θILL
When the value is 6 or more, calculation processing of the magnetic correction amount is started, and the mileage distance of the wheels 3a, 4a is accumulated until the rotation angle Δθ transferred from the rotation angle calculation means 152 becomes equal to or less than the minimum rotation angle θ#LIM. be exposed. That is, as shown in the vehicle travel trajectory 32 in FIG. 6, the vehicle starts turning to the right at time P, and when the vehicle travels a predetermined distance Δ/rn, the rotation angle θa1 reaches the predetermined minimum. Rotation angle θSLIM
If this is the case, the rotation angle θ, when the car starts accumulating the distance traveled by the car and reaches the point R21, is the minimum rotation angle θ, and if it becomes less than the calendar, the total distance traveled up to the point R2 becomes I.
i! The cumulative distance away from the vehicle is determined, and the rotation angle θyo of the vehicle from P to R2 is calculated according to Equation 19. This calculated rotation angle θ8 is a predetermined rotation angle θg1'lAX
When the above is true, the magnetic correction amount is calculated according to Equation 13. As this rotation angle θS□8, for example, 70”~
About 80° is selected.

The correction amount V calculated by the magnetic correction amount calculation means 153
m@, Vra are transferred to the magnetic azimuth calculation means 154,
The corrected magnetic azimuth angle θ is calculated according to Equation 14. This corrected magnetic azimuth angle is displayed on the display device 5.

The processing of the arithmetic circuit 15 explained above will be explained in more detail according to the flowchart of FIG. The process shown in the flowchart of FIG. 7 is a process that is executed every time the vehicle travels by Δ1 m.

In step rt1, a magnetic azimuth angle is calculated based on the detection signal of the geomagnetic sensor 2. If the amount of magnetic correction has already been calculated, calculation of magnetic correction is also performed. In step n2, the vehicle travels a predetermined travel distance Δ1.
The rotation angle Δθ when the vehicle travels m is calculated according to Equation 19. This rotation angle Δθ is determined by the minimum rotation angle θ in step n3.
#LfN, and if it is less than the minimum rotation angle θSLIM, step rs1 and step n2 are repeatedly executed.

If the rotation angle Δθ is greater than or equal to the minimum rotation angle θIILIF1, the process advances to step n4, and the detection signal V
Store l V y 1. Steps n5 to n7 are executed every time the vehicle travels 61 meters. That is, in step n5, similarly to step port 1, the magnetic azimuth angle when the traveling distance Δ1 rn has traveled is calculated, and in step n6, the rotation angle Δθ is calculated. Then, steps n5 and n6 are executed until the rotation angle Δθ becomes less than or equal to the minimum rotation angle θjLIN, and when the rotation angle becomes less than or equal to the minimum rotation angle θaLIN, the process proceeds from step rs7 to step n8.

In step n8, the rotation angle Δθ is the minimum rotation angle θaLIM
The detection signals V w 2 and V y 2 of the geomagnetic sensor 2 at the point P2 where the following values are met are stored. step r
In system 9, the rotation angle θB of the vehicle from point P1 to point P2 is calculated based on the cumulative travel distance of the wheels 3a and 4a, and once the rotation angle θ8 is calculated from Equation 19, The rotation angle θ8 is compared with a predetermined rotation angle θaNAX. If the zero rotation angle θ1 is less than the rotation angle θ□□, the magnetic correction amount calculation is not performed and the process returns to step nl.

If the rotation angle θ1 is greater than or equal to the reference rotation angle θ, . This magnetic correction amount is used in subsequent magnetic azimuth calculations.

As described above, in this embodiment, the magnetic correction amount is calculated every time a car equipped with a magnetic azimuth angle detection device turns by a predetermined rotation angle or more while driving, and automatically calculates the direction of travel of the car. Since magnetic correction is performed, an accurate magnetic azimuth angle is always calculated.

Effects of the Invention As described above, according to the present invention, by rotating the magnetic direction detecting device by a predetermined rotation angle or more, the magnetic correction amount is calculated from the detection signals before and after the rotation.
Even without rotating the magnetic orientation detection device 360°, correction for magnetization, which is a magnetic component that does not change due to rotation of the magnetic orientation detection device, can be easily performed with high accuracy.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a magnetic direction detection device that is an embodiment of the present invention, FIG. 2 is a diagram for explaining the configuration of a geomagnetic sensor 2 used in this embodiment, and FIG. 3 is a diagram of this embodiment. 4I21 is a functional block diagram for explaining the processing contents in the arithmetic circuit 15 of this embodiment, and FIG. 5 is a rotation angle detection pattern for explaining the principle of magnetic correction in this embodiment. FIG. 6 is a diagram for explaining the principle of detecting the traveling distance and rotation angle of an automobile. FIG. 7 is a processing flowchart in the calculation circuit 15 that performs magnetic correction in this embodiment. 8
9 and 9 are omnidirectional detection reference patterns for explaining a method of correcting a detection signal output from a conventional magnetized geomagnetic sensor. DESCRIPTION OF SYMBOLS 1... Processing circuit, 2... Geomagnetic sensor, 3... Right wheel speed sensor, 4... Left wheel speed sensor, 15... Arithmetic circuit, 152... Rotation angle computing means, 153. ...Magnetic correction amount calculation means, 154...Magnetic azimuth angle calculation means agent Patent attorney Kei Saikyo

Claims (1)

[Scope of Claims] Magnetic detection means for detecting two magnetic components in mutually orthogonal directions; and the magnetic detection means rotates by a predetermined angle or more about a central axis in a direction perpendicular to either of the orthogonal directions. a rotation angle detection means for detecting the rotation angle of the magnetic detection means; A magnetic correction amount detection means for detecting a magnetic component that does not change; and a magnetic azimuth detection means for detecting a magnetic azimuth from an output of the magnetic correction amount detection means and an output of the magnetic detection means. Magnetic direction detection device.