JP3277771B2 - Direction detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an azimuth detecting device which is mounted on an automobile or the like to detect a traveling azimuth and can be used for navigation, for example.

[0002]

2. Description of the Related Art Conventionally, a magnetic sensor such as a flux gate is provided to obtain an azimuth signal to a navigation display or the like mounted on a moving body such as an automobile so that the traveling direction can be grasped in comparison with the azimuth. , And measures the magnetic field vector of the running area.

Since the azimuth detecting device including such a magnetic sensor is affected by the magnetization specific to the vehicle body of the vehicle in which the azimuth sensor is mounted, the detection output is corrected to eliminate the influence of the magnetization specific to the vehicle body. The magnetic field vector is obtained. For example, Japanese Patent Publication No. Sho 62-30364,
As proposed in Japanese Patent No. 14125, the center of a circular vector obtained by the rotation of a car is obtained, and the center coordinate is subtracted from the detected coordinates to correct the error due to the body-specific magnetization. I have.

Such an error correction method by calculating the center of a circular vector has the advantage that the magnetic sensor can be used as it is by a simple method by calculation, and the method of calculating the center from the circular vector directly determines the accuracy of azimuth detection. Affects the simplification of the calculation step.

[0005]

In such a correction method, in the above-mentioned conventional configuration, a method of detecting four points intersecting the X-axis and the Y-axis on the coordinates of the circular vector and obtaining the center from the four points. However, in the former method, Xmin, Xmax, Ymin, and Ymax must be sequentially calculated and calculated during the measurement of the circular vector. The deviation of the measurement points causes the measurement points to jump, and particularly when the vehicle turns at high speed, high speed is required to follow such measurement fluctuations, and a high-performance microcomputer is required, which is expensive. Also in the latter case, four X-intersection calculation steps are required to prepare predetermined X-axis lines and Y-axis lines, obtain intersection coordinates of these axes and circular vectors, and calculate the center from the coordinates of the four points thus obtained. The calculation data is calculated by taking in these four points, so that the processing becomes complicated.

[0006]

SUMMARY OF THE INVENTION The present invention provides a detecting device which can obtain the center of the circular vector by simple arithmetic processing, and has a phase angle of approximately 90 degrees on the same plane. Receives an output signal from a magnetic sensor that outputs a detection signal corresponding to terrestrial magnetism, detects an azimuth based on this signal, and detects a variation error from terrestrial magnetism due to a magnetizing characteristic inherent to a moving body on which the magnetic sensor is mounted. And a control unit for correcting a center point from a circular vector obtained by rotation of the magnetic sensor. The control unit includes an arbitrary start point (X1, Y1) on the circular vector and coordinates of the start point. The center of the circular vector is defined as (X1 + X) based on the data of (X1, Y2) and (X2, Y1) on the other two points on the circular vector having one of the coordinates in common.
2) / 2 and (Y1 + Y2) / 2, and the variation error is corrected by subtracting the center data from each data of the detected coordinates (X, Y) on the circular vector. Furthermore, the start point is selected such that one of the other two points (X1, Y2) and (X2, Y1) with respect to the arbitrary start point (X1, Y1) is the same as the start point coordinates. And

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A circular vector corresponding to the geomagnetism obtained by rotating a magnetic sensor has an arbitrary starting point (X
1, Y1) and the other two points that share the coordinates of one of the start point coordinates, (X1, Y2) and (X2, Y1), and define the center of the circular vector as (X1 + X2), (Y1,
Y2), the control means for subtracting the center data from the coordinate data of the detected coordinates (X, Y) and correcting the error is provided, so that calculation based on a small amount of detected point data becomes possible. And a low-cost device can be provided.

[0008]

FIG. 1 is a block diagram of a typical apparatus applied to the present invention. A magnetic sensor 1 of a so-called flux gate type is used, and an excitation coil 3 wound around an annular core 2 is provided with an oscillator 4. And an output signal having a phase angle of about 90 degrees corresponding to terrestrial magnetism is obtained from output windings 5 and 6 wound substantially orthogonally to the annular core.

An output signal from the magnetic sensor 1 is input to a control means 9 comprising a microcomputer via a signal amplifying circuit 7 including a noise filter and an A / D converter 8 for converting into a digital signal for digital processing. Then, the azimuth signal calculated by the control means 9 is supplied to a display device 10 used for, for example, navigation.

The azimuth detecting device is mounted on a mobile body such as an automobile which is easily magnetized together with the magnetic sensor 1, and detects the terrestrial magnetism at a traveling point of the automobile as the mobile body to calculate and display the azimuth. However, since the output signal of the magnetic sensor 1 includes an error due to the magnetization characteristics unique to the mounted vehicle, the control means 9 performs an operation to correct the error.

In the present invention, the control means 9 corrects the output signal of the A / D converter 8 including an error due to the magnetizing characteristics inherent in the vehicle to obtain a faithful azimuth by geomagnetism. As for the method, the execution programming of the control means 9 is set so as to execute the typical vector detection shown in FIG.

That is, when the vehicle is turned on the spot while traveling in the traveling area, the magnetic sensor 1 mounted on the vehicle also rotates in the geomagnetic field in the area and outputs a coordinate output corresponding to the geomagnetism. However, the detection output characteristic based on only the true geomagnetism which is not affected by the magnetization characteristics of the vehicle can be obtained as a circular vector locus centered on the origin coordinate O, whereas the magnetization characteristic unique to the vehicle is not sufficient. Since the detection component is added as an error to the detection component, the detection output is largely shifted from the center of the circular vector as shown in FIG. 2. For example, a circular vector output centered on the coordinate (X0, Y0) is sent to the control means 9. Is entered.

The control means 9 first determines an operation start point in the circular vector output data (X, Y) of FIG. 2, and this operation start point is determined by adopting a turn start initial value when turning the vehicle. Good. For example, the turning start initial value issues a correction value determination command to the control means 9 at the time of a turning operation for determining a correction value, and the initial input value of a detection signal fetching operation for a correction value determination calculation process based on this command is a starting point ( X1, Y1). As for the execution of the correction value determination calculation process, for example, a switch operable by the driver is prepared in advance, and the control means 9 can perform the correction value calculation by operating this switch. After that, the magnetic sensor 1
Correction calculation based on this correction value is performed on the detection output including the error in the above, and the correct azimuth data corresponding to the geomagnetism can be obtained and output. The azimuth display device can also display the azimuth using the correct azimuth data. Becomes

In the process of determining the correction value, that is, the center coordinates (X0, Y0) of the circular vector, as shown in FIG.
In this case, the detection output (X, Y) obtained when the vehicle is turned around from the starting point is obtained as a circular vector centered on the center (X0, Y0). The other two points (X1, Y2) and (X2, Y1) which share the coordinates of one of the starting point (X1, Y1) and one of the coordinates are selected, and the center coordinates of the circular vector are determined based on these data, respectively. X0 = (X1 + X2) / 2, Y0 = (Y1 + Y2)
/ 2.

In this manner, the center of the circular vector (X0, Y0) can be easily determined only by the coordinate data of the starting point (X1, Y1) and the other two points (X1, Y2) and (X2, Y1). After that, the detection data (X, Y)
By subtracting the center data (X0, Y0), which is the correction value from the above, it is possible to obtain azimuth data faithful to geomagnetism in which errors due to the magnetization characteristics unique to the vehicle have been corrected. That is, assuming that the azimuth data is (XM, YM), the azimuth correction calculation in the control means 9 becomes XM = X−
(X1 + X2) / 2, YM = Y- (Y1 + Y2) / 2.

The azimuth data corresponding to the geomagnetism obtained in this way is output, for example, to the display device 10 in FIG. 1 so that the traveling direction can be correctly displayed with respect to the azimuth of the running area of the automobile. The detection and calculation of the coordinates of three points by the detection device of the present invention are represented by the calculation of the start point in the circular vector locus shown in FIG. 2 and the selection of the other two points. Is the same as the center coordinate X0 or Y0 of the circular vector as shown in FIG. 3, the coordinates (X1, Y1) are obtained as the starting point (X0, Y1). The coordinates corresponding to (X2, Y1) are common coordinates (X0, Y
1), and in this case, the center of the X coordinate is immediately obtained by setting X1 = X0.

Therefore, the calculation of the X coordinate such as XM = X- (X1 + X2) / 2 is not required, and the calculation step is further simplified. Therefore, taking advantage of these features, the starting point of at least one of the coordinates is previously set to this coordinate. A similar calculation can be reduced by selection. That is, the MIN coordinate or MAX of the circular vector is obtained from the detection signal taken from the magnetic sensor 1 in the correction value determination process.
By detecting the coordinates and determining the coordinates as the starting point a, the number of subsequent detection points can be reduced, and the number of calculation steps including the correction value can be reduced.

[0018]

As described above, according to the azimuth detecting apparatus according to the present invention, the starting point coordinates and the coordinates of one of the other two points are coincidently compared, and only the center coordinates as the correction value are obtained. Since it is only necessary to execute the operation in simple operation steps, even when the control means is constituted by a microcomputer, the number of operation processes can be reduced, and the current consumption can be reduced by lowering the clock frequency or using a low bit processor. The simplification of the peripheral circuit and the cost reduction can be realized.

[0019]

[Brief description of the drawings]

FIG. 1 is a typical circuit block diagram of an azimuth detecting device to which the present invention is applied.

FIG. 2 is an explanatory view of detection output for calculating a correction value in the azimuth detecting device of the present invention.

FIG. 3 is an explanatory view of a detection output showing another embodiment of a detection output in the azimuth detecting device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magnetic sensor 2 Annular core 5, 6 Output winding 8 A / D converter 9 Control means 10 Display device

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01C 17/38 G01R 33/02 G01R 33/04 G01V 3/40

Claims (2)

(57) [Claims] An output signal is received from a magnetic sensor that outputs a detection signal corresponding to terrestrial magnetism having a phase angle of about 90 degrees with each other on the same plane, and based on this signal, an azimuth is detected and the magnetic field is detected. A control unit for correcting a variation error from terrestrial magnetism due to a magnetizing characteristic inherent to the moving body on which the sensor is mounted by correcting a center point from a circular vector obtained by rotation of the magnetic sensor; An arbitrary start point (X1, Y1) on the circular vector and the other two points on the circular vector sharing the coordinates of one of the start point coordinates, (X1, Y2) and (X2, Y1). The center of the circular vector is expressed as (X1 + X
2) / 2 and (Y1 + Y2) / 2, and the variation error is corrected by subtracting the center data from each data of the detected coordinates (X, Y) on the circular vector. Direction detection device. 2. The starting point is selected such that one of the other two points (X1, Y2) and (X2, Y1) with respect to the arbitrary starting point (X1, Y1) is the same as the starting point coordinates. The azimuth detecting device according to claim 1, wherein: