JPS6230364B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an output correction device for a direction detection device used to detect the direction of movement of an automobile, etc. The present invention relates to a method and device for correcting the output of a direction detection device that detects direction.

In a car direction meter that detects the magnetic flux in the air due to the earth's magnetic field and displays the direction of travel of the vehicle, the direction detecting device that detects the earth's magnetic field, that is, the earth's magnetic field, should be installed as close to the earth as possible inside the vehicle. A body steel plate, for example, for the central part of the roof, is sometimes selected due to the constraint that there is little disturbance in the magnetic field and that the orientation detection device must be relatively easy to install and fix. In general, body steel plates are made of ferromagnetic material such as iron, and are hard and relatively prone to residual magnetism, so even if they are completely demagnetized initially, During long-term use of a vehicle, the body steel plate becomes magnetized by magnetic fields from outside the vehicle, vehicle wire harness current, body surface current, or magnetic fields from magnets, etc., resulting in the formation of residual magnetism. In other words, it is often considered that the magnet is magnetized. In this case, not only the magnetic flux due to the earth's magnetic field but also the extra magnetic flux due to the magnetization of the body steel plate acts on the azimuth detecting device, so that the azimuth detecting device cannot accurately detect the azimuth.

As a technique for preventing the extra magnetic flux caused by the magnetization of the body steel plate as described above from acting on the orientation detection device, the following method can be considered. One method is to magnetically demagnetize the body rigid plate at predetermined intervals during the use of the vehicle by using an AC demagnetization method or the like. However, this method has the disadvantage that demagnetization requires time and effort, and also requires demagnetization equipment. Another method is to incorporate a compensation winding near the azimuth detection device or into the azimuth detection device itself, and apply an appropriate DC current to create a compensation magnetic field, thereby reducing the residual magnetic flux caused by the body's magnetization. This is a way to cancel it. In this method, it is necessary to add a compensation winding, and each time the magnitude of magnetization changes, the compensation current must be precisely adjusted to adjust the magnitude of the compensation magnetic field. The drawback is the complexity of adjustment.

By the way, as a magnetic detection device that generates an output voltage in proportion to the amount of magnetic flux generated in the air due to the earth's magnetic field interlinking with a detection element, for example, a magnetic modulation type flux gate valve, a magnetic flux gate valve using a Hall element, etc. There are tsukusumeters, etc. Two such detection elements are used, for example, in a magnetic modulation type flux gate valve, the first and second magnetic detection elements are arranged on the same plane with a phase angle of 90° from each other. When placed horizontally in the earth's magnetic field, if the angle between the central axis of the winding of the first magnetic sensing element and the horizontal component Beh of the air magnetic field density due to the earth's magnetic field is θ, then the following equation ( It is possible to extract outputs as shown in 1) and (2).

X=KxBeh cos θ (1) Y=KyBeh cos (θ−90°) =KyBeh sin θ (2) Here, X is the output of the first magnetic sensing element, Y is the output of the second magnetic sensing element, Kx and Ky are coefficients that depend on the output gains of the first and second magnetic sensing elements, and if the outputs of the first and second magnetic sensing elements are perfectly balanced, Kx and Ky will be They are equal to each other and Kx=Ky=K.

The X and Y outputs shown in equations (1) and (2) are Kx=Ky
= K, if θ is changed from 0 to 360 degrees, for example, in the case of a vehicle, if the vehicle makes one rotation or one turn in the earth's magnetic field, equations (1) and (2) If we eliminate θ from , we get the following formula (3), as is well known mathematically
The radius centered on the origin of the XY coordinates as shown by
It becomes a circular trajectory of KBeh.

X ² + Y ² = (KBeh) ² (3) In addition, when Kx≠Ky, the X and Y outputs are calculated using the following formula.
As shown in (4), the trajectory is an ellipse centered on the origin of the XY coordinates.

X ² /(KxBeh) ² +Y ² /(KyBeh) ² =
1(4) In the above case, only the magnetic flux density Beh due to the earth's magnetic field exists at the location where the magnetic sensing element is installed, but there is a magnetic flux density Beh due to the earth's magnetic field at the location where the magnetic sensing element is installed. If there are extra magnetic flux densities Bsx, Bsy due to magnetization, etc., the outputs X, Y of the first and second magnetic sensing elements
changes. The outputs of the first and second magnetic detection elements in this case were found to be expressed by the following equations (5) and (6) from the results of experimental research conducted by the present inventors.

X=KxBsx+KxBehcos θ (5) Y=KyBsy+KyBehsin θ (6) As is clear from equations (5) and (6), when disturbance magnetism Bsx and Bsy act on a magnetic detection element, the output of that element will be Just by adding DC bias,
It was found that when θ was varied from 0 to 360°, the AC component of the output still became a sine wave.
In other words, even when there is magnetization due to a disturbance magnetic field, it is sufficient to consider the magnetic flux density caused by the magnetization and the magnetic flux density caused by the earth's magnetic field, and if the amount of magnetization changes, the detection element The experimental research conducted by the present inventors revealed that the output of the sine wave changes only in the DC level, and the sine wave does not change in phase or amplitude and is preserved.

Note that the horizontal component Beh of the magnetic flux density in the air due to the earth's magnetic field is 0.26 to 0.33 Gauss (in Japan).
According to the results of experimental research conducted by the present inventors, even when the magnetic detection element is mounted quite close to the body steel plate, the magnetic flux density Bsx, Bsy due to the magnetization component that acts on it is at most 2 Gauss. It is usually less than 1 Gauss, and the magnetization component is rarely an order of magnitude larger than the earth's magnetic component while the vehicle is in use.

When Kx=Ky=K, the outputs X and Y of the first and second magnetic detection elements shown by equations (5) and (6) are calculated by rotating the vehicle one rotation or one turn and changing θ from 0 to 360°. When it is changed, it becomes a circular locus whose center moves from the origin of the XY coordinates to the point (KBsx, KBsy), as shown by the following equation (7).

(X-KxBsx) ² + (Y-KyBsy) ² = (KBeh) ² (7) Also, the outputs X of the first and second magnetic detection elements,
When Kx≠Ky, the center of Y is a point (KxBsx,
The trajectory traces an ellipse moving to KyBsy).

(X-KxBsx) ² / (KxBeh) ² + (Y-K
yBsy) ² /(KyBeh) ² = 1(8) As is clear from Figure 1, which illustrates general equations (4) and (8), including the case where Kx≠Ky, body magnetization depends on In this case, it can be considered that the center point of the ellipse has moved vectorially on the XY coordinate plane by this amount of magnetization. Since the magnetic detection element is fixed to the vehicle body, there is no relative displacement between the body magnetization and the magnetic detection element, and they are always in a constant positional relationship, so the amount of center point movement is uniquely determined once the amount of magnetization is determined. be done.

Based on the above facts, the outputs X, Y of the first and second magnetic detection elements when there is body magnetization
According to FIG. 2, it is clear that the biases Xd and Yd of the outputs X and Y due to magnetization are related by the following equations (9) and (10).

Xd=Xmax+Xmin/2=KxBsx (9) Yd=Ymax+Ymin/2=KyBsx (10) The present invention provides a correction device for calculating the output correction of the magnetic detection element due to body magnetization based on the above-mentioned relational expression. is intended to provide.

In the following, the invention will be explained in detail by way of example embodiments with reference to the accompanying drawings.

FIG. 3 is a block diagram showing the output correction device according to the present invention for one channel of the X output of the first magnetic detection element of the azimuth detection device. The X output generated by the first magnetic detection element included in the orientation detection device 10 is input to the maximum/minimum output value detection device 11 and the arithmetic device 12 . The maximum/minimum output value detection device 11 detects outputs X=X1, X2, . . . input during a period commanded by the control device 13.
Find the maximum value Xmax and minimum value Xmin from the value of Xn. The maximum output value Xmax and minimum output value Xmin are stored in the storage device 14.

The output X of the first magnetic detection element input to the calculation device 12 is corrected by performing the calculation shown in the following equation (11) based on the maximum output value Xmax and minimum output value Xmin stored in the storage device 14. Outputs the output value X′.

X'=X-Xmax+Xmin/2 (11) The control device 13 is the maximum/minimum output value detection device 11
and controlling the operation of the storage device 14, during a data sampling period for determining the maximum output value and minimum output value, and when determining new maximum output values and minimum output values from the magnetic detection element and storing them in the storage device 14,
This is a device that issues control signals and the like for resetting the maximum and minimum output values previously stored in the storage device 14 to zero.

Correction of the output of the second magnetic detection element of the orientation detection device 10 is performed by a device substantially similar to that shown in FIG. In this case, the arithmetic device performs the arithmetic operation shown in the following equation and outputs the corrected output value of the second magnetic detection element.

Y'=Y-Ymax+Ymin/2 (12) FIG. 4 is a block diagram showing another embodiment of the output correction device according to the present invention.

The outputs X and Y of the first and second magnetic detection elements of the direction detection device 10 are inputted as digital values to the maximum/minimum output value detection device 17 via the multiplexer 15 and the A/D converter, and are input to the maximum/minimum output value detection device 17 for the first magnetic detection. Maximum output value Xmax and minimum output value Xmin of the element and maximum output value Ymax and minimum output value of the second magnetic detection element
Ymin is required. These maximum output values and minimum output values are stored in the storage device 18. The pushbutton switch 19 is operated manually when determining the above-mentioned maximum output value and minimum output value, which are calibration data.
The signal from the pushbutton switch 19 is given to the calibration signal generator 20, and the calibration signal generator 20 that receives this signal detects the first and second magnetic detection elements while the pushbutton switch 19 is in the on state. The maximum output value and the minimum output value are determined from the outputs X and Y of the , respectively, and the operation of the maximum/minimum output value detection device 17 and the control device 18 is controlled so that these calibration data are newly stored in the storage device 18. .

The outputs X and Y of the first and second magnetic detection elements are input to the arithmetic unit 21, and the above-mentioned formula (11) is calculated based on the maximum output value and minimum output value stored in the storage device 18.
The calculations shown in (12) and (12) are performed to correct the output of each detection element, and output correction values X' and Y' are output.

In the embodiment shown in FIG. 4, digital signal processing is performed using a multiplexer and an A/D converter for the two output parts of the first and second magnetic detection elements. It is not necessarily necessary to perform digital signal processing, and analog signal processing may be used as long as the function of determining the maximum output value and minimum output value and the calculation function are achieved.

FIG. 5 is a flowchart illustrating the operation of the apparatus shown in FIG. First of all, when the push button switch for calibration is turned on, this on signal causes the previous maximum output value of each of the first and second magnetic sensing elements stored in the storage device 18 and The minimum output value is reset to zero. Then, while this pushbutton switch is in the on state, the vehicle is rotated 360 degrees in a place where there is no disturbance in the earth's magnetic field, or the vehicle is rotated in a circle. Outputs generated by the first and second magnetic detection elements during this period
2. Read...Xn, Y=Y1, Y2,...Yn. Then, the maximum output value Xmax and minimum output value Xmin of X1 to n, and the maximum output value Ymax and minimum output value Ymin of Y1 to n are determined and newly stored in the storage device 18. This completes the operation of obtaining correction data by turning on the pushbutton switch 19.

Next, when the pushbutton switch 19 is not on, that is, when the vehicle is running normally, the outputs X and Y of the first and second magnetic detection elements are read, and this is used as the correction data stored in the storage device 18 as described above. Xmax,
Using Xmin, Ymax, and Ymin, perform the calculations shown in equations (11) and (12) above to calculate the corrected output value of each magnetic detection element.
Calculate and output X' and Y'. This corrected output value
X' and Y' are input to an arithmetic unit (not shown) for determining the vehicle's heading.

Although the present invention has been described in detail with respect to specific embodiments above, it will be understood by those skilled in the art that the present invention is not limited thereto and that various embodiments can be made within the scope of the present invention. It should be obvious.

[Brief explanation of the drawing]

Figure 1 is a graph showing the trajectory of the output of the magnetic detection element in the presence and absence of body magnetization, and Figure 2 is a graph showing the output of the magnetic detection device when body magnetization is present. 3 and 4 are block diagrams each showing an embodiment of the output correction device according to the present invention, and FIG. 5 is a graph showing the output of each magnetic detection device with the angle as the horizontal axis 3 is a flowchart showing the operation of the output correction device shown in FIG. 10-Direction detection device, 11-Maximum/minimum output value detection device, 12-Arithmetic device, 13-Control device, 1
4~Storage device, 15~Multiplexer, 16~
A/D converter, 17~maximum/minimum output value detection device, 18~storage device, 19~push button switch,
20~ Calibration signal generator, 21~
Computing device.

Claims (1)

[Scope of Claims] 1. First and second magnetic detection elements that detect earth's magnetism with a phase angle of 90 degrees to each other on the same plane, each of the first and second magnetic detection elements An output correction device for a direction detection device that detects the direction from the output, and a maximum/minimum device that receives the output signals of the first and second magnetic detection elements and detects the maximum output value and minimum output value of each magnetic detection element. an output value detection device; a control device that controls a period during which the output signals of the first and second magnetic detection elements are input to the maximum/minimum output value detection device; and a control device that controls the maximum output value and the minimum output value. 1. An output correction device comprising: an arithmetic device that calculates a corrected output value of each magnetic detection element by performing the arithmetic operation shown in the following formula. X'=X-Xmax+Xmin/2 Y'=Y-Ymax+Ymin/2 However, X': Corrected output value of the first magnetic sensing element, X: Output value of the first magnetic sensing element, Xmax:
Maximum output value of the first magnetic sensing element, Xmin: Minimum output value of the first magnetic sensing element, Y': Corrected output value of the second magnetic sensing element, Y: Output value of the second magnetic sensing element, Ymax: Maximum output value of the second magnetic detection element, Ymin: Minimum output value of the second magnetic detection element.