JPS59100812A - Device for detecting bearing - Google Patents

Abstract

PURPOSE:To compensate bearing drift by simple operation by adding a value smaller than the radius of a vector circle to the vector component of detected earth magnetism and making a straight line intersect with the vector circle to determine the center of the vector circle from the coordinates of the intersecting point. CONSTITUTION:When a switch 70 is turned on, a microcomputer 50 adds a fixed value smaller than the radius of earth magnetism vector circle to the detected components of the intersecting directions of two axis x, y of the earth magnetism vectors corresponding to the bearing of a car which is outputted from a bearing detecting sensor 10. At least one straight line out of two straight lines parallel with the axis x, y passing through the added coordinate value intersects with the vector circle. Consequently, the center coordinates to the vector circle is determined simply without using the coordinates of three points on the circumference by operating a mean value of these intersecting coordinates. The detected earth magnetism vector component is compensated in accordance with the center coordinate value corresponding to the drift due to magnetization to the car body and the correct bearing of the car body is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a direction detection device used for detecting the direction of movement of an automobile or the like.

Conventionally, as a sensor for measuring a magnetic field vector due to the earth's magnetic field, there are, for example, a flux gate valve, a Franks meter using a Hall element, or the like. This is a method in which two of these detection elements are used, arranged for example in two directions (X-axis, Y-axis directions) orthogonal to each other on one plane, and the magnetic field components of each are determined. When the signals detected from these two detection elements are processed by an appropriate circuit and then extracted as a voltage signal, the locus of the signal generally has an elliptical shape. When one output component is Vx and the other output component is vy, Vx and Vy can be written as the following equation.

Vx=Kx-Bcosθ V)'=Ky-Bs inθ However, Vx is the output of the first magnetic detection element, and Vy is the output of the second magnetic detection element.
The outputs of the magnetic detection elements, Kx and Ky are coefficients depending on the output systems of the first and second magnetic detection elements, and B is the horizontal component of the earth's magnetic field. θ is the angle between the horizontal component B and the central axis of the second magnetic sensing element. Here, if the output circuits for Kx and Ky are opened equally, the magnetic field vector locus represented by the measured voltage output will be a circle. FIG. 1 shows this vector locus. In this way, when the magnetic field vector is only due to the earth's magnetic field, the detected vector locus becomes a circle 1 centered on the origin.

However, in reality, as described above, the origin of this vector trajectory is not necessarily the origin due to the influence of magnetization in the vehicle body. The value of this magnetization vector is measured in a coordinate system fixed to the vehicle body. Therefore, even if the vehicle rotates with respect to its orientation, the magnetization vector rotates together with the vehicle body, so the output of the orientation detection sensor fixed to the vehicle body does not vary with the rotation of the vehicle body.

That is, the influence of the magnetization vector on the orientation detection sensor with respect to the rotation of the vehicle is the influence as a direct current component. Therefore, as shown in FIG. 1, a circular vector locus is drawn centered on a point that is A vector away from the origin. Therefore, if the direction is influenced by magnetization when determining the orientation from this vector locus, it cannot be determined simply as the arctangent of the ratio of the X-direction or Y-direction components of the measured magnetic field vector. That is, the direction must be determined using the following formula.

θ-tan' ((Vx-Box) / (Vy
-Boy) Here, 13ox, Boy is due to the X and Y direction components of the magnetization vector. In this way, the output signal detected from the direction detection sensor mounted on the vehicle must be corrected by the amount of the magnetization vector. And, this magnetization vector amount changes the vehicle body from 0 to 36
It is given by the vector amount at the center of the circle of the vector locus drawn by the output signal when it is rotated once in the range of 0 degrees. Therefore, after finding the center of the vector locus, it is necessary to correct it as in the above equation to find the orientation θ.

Therefore, there is a "direction detecting device" disclosed in Japanese Patent Application Laid-open No. 148210/1983, which performs correction by finding the center of the circle of the vector locus described above. This direction detection device detects the maximum value Xm in each of the X direction and Y direction when the moving object is rotated one rotation or more at the timing of the Swiss-Sochi operation.
a x, Ymax and the minimum values Xm1n, Ymin are calculated, (Xmax+Ymin)/2, (
The correction value is obtained by calculating Ymax+Yrnin)/2.

However, since this device requires two switch operations to indicate that the moving object has rotated one turn or more, if the moving object has not rotated one turn or more between the two switch operations, ff12 is activated. As shown by the solid line in the figure, the vector locus does not draw a perfect circle, so
The maximum and minimum values of the direction are different from the true ones,
(Xmax 10Xm1n)/2, (Ymax 10Ymin)
There is a problem that the correction value obtained by calculating /2 becomes incorrect. For the one in Figure 2, Xm1
n, Ymin are true values, but Xmax.

Since Ym a x is smaller than the true value, the center of the circle is closer to the origin than the true center.

The present invention has been made in response to the above problem, and its purpose is to obtain data necessary to find the true center of the circle when a timing instruction is generated from a timing means such as a switch, It is an object of the present invention to provide an orientation detecting device that determines the true center of the circle, that is, the correction value, when all such data are collected. In other words, the present invention eliminates the need to rotate the moving body more than once in order to find the center of the circle of the vector locus, and the data necessary to find the center of the circle, that is, a straight line parallel to the X-axis and the vector locus, are not required. The center of the circle is determined when the average value of the two points where the vector locus intersects with the line parallel to the Y axis and the average value of the two points where the vector locus intersects with a straight line parallel to the Y axis are obtained. Therefore, when the timing of output correction is given by a switch operation, it is not necessary to perform the switch operation twice, but only once, and the cumbersomeness of the input operation can be eliminated.

The present invention will be described below with reference to embodiments shown in the drawings.

FIG. 3 is a block diaphragm showing one embodiment thereof. In this FIG. 3, lO is an orientation detection sensor. The orientation detection sensor 1o has an annular core 14, and an excitation winding 11 is provided around the core 14. Both ends of the excitation winding 11 are connected to an oscillator 21. On the other hand, the output winding 12 is wound around the opposing body portions of the annular core 14, and the annular core 1 is similarly wound in a direction orthogonal thereto.
An output winding 13 wound around 4 is arranged. The output of the output winding 12 passes through a filter 25a and is input to an amplifier 23a, and the output of the other output winding 13 passes through a filter 25b and then input to an amplifier 23b. The outputs of these amplifiers 23a and 23b are input to sample and hold circuits 24a1 and 24b, respectively.
The hexagonal gates of these sample and hold circuits 24a and 24b are connected to input a signal from the timing generation circuit 22. And sample hold circuit 2
The outputs of 4a and 24b are respectively input to an A/D converter 60, converted into digital quantities, and sent to a microcomputer 5.
It is entered as 0. The output of the microcomputer 50 (
The direction signal) is output to the display drive circuit 40, and the display drive circuit 40 drives the display device 30 to display the traveling direction of the vehicle.

Further, the switch 70 is set by the user to the microcomputer 5.
This is for causing the 0 to execute correction, and constitutes a timing means that generates a timing instruction when it is turned on.

Note that the A/D converter 60 and the microcomputer 50 constitute a calculation means, and the part indicated by the reference numeral 100 constitutes an azimuth detection section. In such a configuration, the operation will be explained as follows.

Since the annular core 14 is made of a magnetically hard material, it can be easily saturated.

The alternating current of frequency F applied to the excitation winding 11 saturates the magnetic flux within the annular core 14. and,
Since the earth's magnetic field, which is a DC magnetic field, penetrates the annular core 14, the magnetic field created inside becomes high-frequency vibrations biased by the earth's magnetic field component. The high frequency vibration of the saturated magnetic flux modulated by the earth's magnetic field component causes electromagnetic induction in the two output windings 12, 13, and output signals are generated at both ends thereof. The amplitude of the second harmonic component of the excitation frequency F of the output signal is proportional to the magnitude of the earth's magnetic field, which is the DC component. Therefore, only the second harmonic is amplified in the amplifiers 23a and 23b via the filters 25a and 25b, and the sample and hold circuit 24a
, 24b sample and hold the peak value. The locus of the vector whose X and Y components are the output signals (Vx, Vy) detected by the output winding 12 and the output winding 13 perpendicular thereto is shown in FIG. 7 when the car rotates once as described above. Draw a circle like this.

Next, the arithmetic processing of the microcomputer 50 will be explained. FIG. 4.5.6 is a flowchart showing the calculation process. Step 100 is a step for so-called data initialization. In step 200, the digitized sensor outputs Vx and Vy are converted into A/D
It is taken in from the converter 60. In step 300, it is determined whether the user has pressed the switch 70 to perform correction.

If the switch 70 is pressed, the process proceeds to step 310, where calculation is performed using the formula shown in FIG. 4 based on the sensor outputs Vx and Vy at that time, and CV X + +CVx is calculated.
-+ CVy+, CV)'- value is stored.

This CV X + , CV X −, CV )T +
, CV y- value and sensor output Vx, V at that time
The relationship with y (point P on the output circle) is as shown in FIG. Note that r shown in the calculation formula of FIG. 4 is the radius of the output circle. Furthermore, the value of 0.625 is not limited to this value; when the switch 70 is pressed, no matter where the sensor output is on the sensor output circle, the output circle and the straight line X = CVx + or X = CVx - has two intersections and is perpendicular to the output circle iM Y = CV y + or y
=cvy- may also be a value that has two points of intersection. Then, in step 320, FO is set to 1 without indicating that the correction is in progress, and the process returns to step 400. step 400
Then, from the sensor output ■x+V)', the correction values xc, yc
(previously determined and stored) is subtracted, and the vehicle traveling direction θ is calculated from the result using the formula shown in FIG. In step 500, the display drive circuit 40 is driven to display θ obtained in step 400 on the display 3o. In step 600, it is determined based on the FOO value whether correction is being performed or not. If correction is not being performed (FO=0), the process returns to step 200. If correction is in progress (FO=1), the process advances to step 700 in FIG. At step 700, the process branches depending on the value of Fl, which indicates whether two intersections between the output circle and the straight line X=CVx+ or X=CVx- have been found. If two points of intersection have been found (F1=1), the process proceeds to step 100 in FIG. 6, or if two points of intersection have not been found (F1=0), the process proceeds to step 800. In step 800, the sensor
Determine whether the output Vx is equal to CVx+ (determine whether the sensor output circle intersects the straight line X = CV x + +7). If they are not equal, the process advances to step 900.

If they are equal, the process proceeds to step 810, if F2=1, the process proceeds to step 812, and if F2=0, the process proceeds to step 811. F2=1 means that one intersection between the output circle and the straight line X=CVx+ has been found, and F2=O means that no intersection has been found. In step 811, the Y output vy of the intersection point found is stored as YCI, and since one intersection point has been found, F2=1 is set.

Further, when the process proceeds to step 812, it is determined whether the Y output ``y'' of the intersection of the output circle and the straight line X=CVx+ found this time is greater than the Y output YCI of the intersection found previously. This is because the sensor output changes due to disturbance, and the straight line
This is to avoid capturing the Y output when it intersects with CVx+.

If the difference between YCI and vy is less than , it is determined that they are the same intersection. If the difference between YCI and vy is R or more, step 813
Then, the sensor Y output correction expected value YC' is obtained by calculating (YCl +V y) /2. Also, steps 900, 910, 911, 912, and 913 are X=CVx
Steps 800, 810 . as described above. ．． 811,
The same processing as 812 and 833 is performed. moreover,
Steps 1100, 1110, 1111, 11 in Figure 6
12.1113 and steps 1200, 1210, 121
Also for 1.1212.1213, y=cvy+ and Y=
A similar process was performed for cVy-.

At step 1300, it is determined whether or not the sensor output correction scheduled values XC' and YC' have been determined, respectively, based on the values of Fl and F4. If they have been determined, the process advances to step 1310, and the sensor output correction scheduled values Xc' and YC' are determined. Sensor output correction value xc
, yc. Also, flags FO to F6 are cleared.

As a result, the sensor output correction values xc, yc to be used in step 400 of FIG. 4 from the next time onwards are newly determined and become the correct values, so that the vehicle traveling direction θ can be determined accurately.

In the above embodiment, the switch 70 operated by the user is used as the timing means, but the timer uses a timer to control the timing when the driving time of the vehicle reaches a predetermined time or the distance traveled by the vehicle reaches a predetermined distance. Means for automatically generating timing instructions may be used.

[Effects of the present invention]

Generally, to find the center of a circle from a point on its circumference,
Mathematically, all you need to know is the different points on the circumference. However, this requires complex calculation processing such as multiplication, and if a microcomputer is used for this processing, a large amount of programs will be required. In contrast, the calculation of the present invention simply calculates the average value of two points where a straight line parallel to the X-axis intersects with the vector locus, and the average value of two points where a straight line parallel to the Y-axis intersects with the vector locus. The center of the circle can be found through arithmetic processing. Also, when the vector locus is not a perfect circle but an ellipse, the center of the circle that is found using the three points mentioned above will deviate from the true center as the oblateness of the ellipse increases. In contrast, according to the present invention, the center of the circle can be determined without being influenced much by the magnitude of the aspect ratio.

Furthermore, the two straight lines parallel to the X-axis and the two straight lines parallel to the Y-axis are set based on the electrical signals in the X and Y directions from the direction detection section at the time when the timing instruction is generated from the timing means. , among the above-mentioned straight lines, there are two straight lines parallel to the X-axis and Y-axis that always intersect the vector locus at two points, and the center of the circle of the vector locus must be determined using the two intersections of each straight line. You can ask for it. (The straight line used to find the intersection with the vector locus is fixed, e.g.
If the axis is the Y axis, the straight line and the vector locus may not intersect, and in that case, the center of the circle cannot be found. )

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the vector locus of the signal from the direction detection unit 100, FIG. 2 is an explanatory diagram for explaining the problems of the conventional device, and FIG. 3 is a block diaphragm showing an embodiment of the present invention. , FIG. 4, FIG. 5, and FIG. 6 are flowcharts showing the arithmetic processing of the microcomputer 50 in FIG. 3, and FIG. 7 is an explanatory diagram for explaining the operation. 10... Direction detection sensor, 100... Direction detection section. 50...Microcomputer, 60...A/D converter/IA device, 70...Switch. Representative Patent Attorney Takashi Okabe

Claims (1)

[Claims] The device is attached to a moving body and configured to separate and detect the direction of the earth's magnetic field into two orthogonal directions (X and Y directions),
An azimuth detecting section configured such that the electrical signal output in the X and Y directions draws a circular vector locus, a timing means for generating a timing instruction for output correction, and an electrical signal in the x and Y directions from the azimuth detecting section. Input the X, Y
The previously determined X and Y direction correction values are each subtracted from the electrical signal in the direction, the direction of travel of the moving object is determined using the signal resulting from the subtraction, and a direction signal is generated. When a timing instruction is generated from the means, and when a timing instruction is further generated from the timing means, electric signals in the X and Y directions from the direction detecting section determine the center of a circle of a vector locus drawn by the electric signals in the X and Y directions. The above-mentioned X is determined by the values in the X and Y directions that define the center. In an orientation detection device having a calculation means configured to obtain a correction value in the Y direction, when a timing instruction is generated from the timing means, the calculation means calculates the electricity in the X and Y directions input from the orientation detection unit at that time. By the signal
A predetermined value smaller than the radius of the circle of the vector locus is added or subtracted to the electric signal in the X direction and the electric signal in the Y direction, and
Form two parallel straight lines in each direction and Y direction,
Electrical signals in the x and y directions from the direction detection section are used to find the intersection points of the vector locus of the circle and the straight lines in the x and y directions, so that one of the two straight lines in the x direction intersects the vector locus of the circle at two points, and determines that one of the two straight lines in the Y direction intersects the vector locus of the circle at two points, then the straight line in the X direction and the vector locus intersect at two points. A direction detection device characterized in that the correction values in the X and Y directions are determined by an average value of two points where the straight line in the Y direction intersects with the vector trajectory.