JPS6319515A - Azimuth detector - Google Patents

Abstract

PURPOSE:To obtain an accurate azimuth even if the detected azimuth of a direction sensor includes distortion, by storing the degree of influence of a magnetic body upon the detected azimuth of the azimuth sensor in an optional direction. CONSTITUTION:A moving body has the magnetic body whose permeability is different from that of air. The azimuth sensor is attached in a prescribed position to the magnetic body and detects the azimuth of terrestrial magnetism as decomposed components in two directions orthogonal to each other. The detected azimuth indicated by output values of these two-direction components of the azimuth sensor includes the distortion due to the magnetic body. The degree of influence of the magnetic body upon the detected azimuth of the azimuth sensor is changed in accordance with the angle formed between the magnetic body and the magnetic field due to the terrestrial magnetism, and the change of this degree of influence is invariable on prescribed position relations between the magnetic body and the azimuth sensor. The degree of influence of the magnetic body upon the detected azimuth of the azimuth sensor in an optional azimuth is stored in a storage means, and a correcting means corrects the detected azimuth, which is indicated with output values of two-direction components of the azimuth sensor, on a basis of this stored degree of influence.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an output correction device for an orientation detection device that detects orientation using earth's magnetism. In particular, it corrects errors caused by magnetic field distortion caused by magnetic bodies provided on the moving body.

[Conventional technology]

Conventionally, as such a device, Japanese Patent Application Laid-Open No. 57-14821
There is a No. 0 "azimuth detection device" that manually calculates the traveling direction of a moving body using two orthogonal electric signals (X, Y directions) from the direction detection section, generates a direction signal, and also calculates the amount of distortion. When the detection switch is turned on and the mobile body rotates one or more revolutions, the maximum and minimum values in each direction are determined from the electric signals in the X and Y directions from the direction detection section, and based on these values, the X, A device is disclosed in which the electric signal in the X and Y directions from the direction detection section is corrected by determining the amount of movement of the center of the vector locus of a circle, that is, the origin, in which the electric signal in the Y direction is drawn. As another embodiment, when the distortion amount detection switch is turned on, gain data is obtained by taking the ratio of the maximum values in the respective directions instead of correcting the movement of the origin, and using this gain data, the A system has been disclosed that corrects an electric signal in the Y direction so that its vector locus draws a perfect circle.

This device is effective in correcting errors caused by magnetization of vehicle bodies and other iron parts.

[Problem that the invention seeks to solve]

The above-mentioned conventional techniques are effective in correcting errors caused by magnetization of vehicle body shelves and other iron parts.

However, the above-mentioned conventional technology cannot correct errors in orientation caused by magnetic field distortion caused by magnetic bodies including body steel plates and other iron parts.

In other words, if a substance (such as a magnetic material) with a magnetic permeability different from that of the air is placed in the uniform earth's magnetic field generated in the air, the earth's magnetic field will become non-uniform around it due to the difference in magnetic permeability.
The tangential direction of the magnetic field lines is also deflected. If there are magnetic bodies near or around the orientation sensor, the earth's magnetic field detected by the orientation sensor will naturally be distorted by these magnetic bodies, so the orientation indicated by the output of the orientation sensor will be
The value will be different from the actual direction.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an azimuth detection device that can obtain an accurate azimuth even when the installation of an azimuth sensor causes distortion in the earth's magnetic field at the location.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention is configured to be attached to a moving body including a magnetic body at a predetermined position with respect to the magnetic body, and to orthogonal to the direction of the earth's magnetic field. an azimuth sensor that separates and detects components in two directions; and a storage means that stores the degree of influence of the magnetic body on the detected azimuth indicated by the output values of the components in the two directions of the azimuth sensor in any given azimuth. and a correction means for correcting the detected orientation indicated by the output values of components in two directions of the orientation sensor based on the degree of influence stored in the storage means.

[Effect]

Next, the operation of the above-described configuration of the present invention will be explained.
The moving body of the present invention includes a magnetic body having a magnetic permeability different from that of air. A uniform magnetic field exists in the air due to the earth's magnetism. This magnetic field becomes nonuniform around the magnetic material due to differences in magnetic permeability, causing magnetic flux to become denser and denser around the magnetic material, and the tangential direction of the magnetic lines of force is also deflected.

The orientation sensor detects the geomagnetic orientation by decomposing it into components in two orthogonal directions. The geomagnetic direction detected by this direction sensor is a magnetic field distorted by the above-mentioned magnetic material, and the detected direction indicated by the output values of components in two directions of this direction sensor includes distortion caused by the magnetic material. Here, since the magnetic material and the orientation sensor have a predetermined positional relationship, the degree of influence that the magnetic material has on the detected orientation of the orientation sensor changes depending on the angle between the magnetic material and the magnetic field caused by the earth's magnetism, and this influence The change in degree remains unchanged under a predetermined positional relationship between the magnetic body and the orientation sensor.

The storage means stores the degree of influence of the magnetic body on the detected orientation indicated by the output values of components in two directions of the orientation sensor in any orientation.

The correction means corrects the detected orientation indicated by the output values of the two-direction components of the orientation sensor, based on the degree of influence stored in the storage means.

〔Effect of the invention〕

In the device of the present invention, the degree of influence of the magnetic body on the detected direction of the direction sensor in a given direction is stored in the storage means, and the direction detected by the direction sensor is corrected by the correction means based on this degree of influence. Accurate orientation can be obtained even if the orientation of the orientation sensor includes distortion depending on the body.

〔Example〕

An embodiment in which the present invention is applied to a device for detecting the straight direction direction of a vehicle will be described.

First, the configuration of this embodiment will be explained based on the drawings.

FIG. 2 is a block configuration diagram showing the configuration of this embodiment. Reference numeral 1 denotes an orientation detection section, and the orientation sensor 10 includes an excitation winding ID and output windings IA and 1B wound orthogonally to each other on a magnetic core IC made of a ferromagnetic material. Reference numeral 11 denotes an oscillation circuit which outputs a rectangular wave signal A (FIG. 3 (1)) in order to excite the excitation winding ID at a frequency f. The magnetic field inside the magnetic core IC changes according to the sum of the horizontal component force H of the earth's magnetism applied to the orientation sensor 10 and the horizontal component force of the earth's magnetic distortion, H + h, and an output proportional to the magnetic field inside the magnetic core IC is output. A filter 12A is taken out from the windings IA and IB and has the same configuration as that of a capacitor and a resistor.

12B, the outputs X, Y ((21, 31) of the frequency 2f component are obtained. After amplifying these outputs X, Y using the amplifier circuits 13A and 13B, the signal C from the timing circuit 14 (Fig. 3 (4)), if the hold circuits 15A and 15B sample and hold, the point 15a, 1
Direct current outputs χ and y are obtained at point 5b.

These outputs χ and y are input to the control unit 2, A/D converted by the A/D converter 21 into data that can be input to the microcomputer 22, and input to the microcomputer 22.

This microcomputer 22 includes a ROM 23 that is a read-only memory and a RAM 24 that is a writable and readable memory. Further, the microcomputer 22 receives a signal from the magnetization correction switch 3 and is connected to a liquid crystal drive circuit 25 that drives the liquid crystal display device 4 .

FIG. 4 is a diagram showing the arrangement of the direction detection section 1 and the control section 2 in the vehicle, and the direction detection section 1 and the control section 2 are
It is fixed inside the dash board of the vehicle M in the straight forward direction of the vehicle M (arrow F).

Since the magnetization correction switch 3 is operated by the driver,
It is provided at a position where the driver can operate it, and the liquid crystal display device 4 is also provided at a position where the driver can easily see it.

Next, the operation of this embodiment will be explained based on the drawings.

The output of output winding IA in FIG. 2 corresponds to the χ axis in FIG. 5, and the output of output winding IB corresponds to the y axis in FIG. Note that the y-axis direction in FIG. 5 is the direction of magnetic north, and for convenience, the description will be made assuming that magnetic north and the geographic north pole coincide.

When there is no error due to magnetization of the body or other iron parts of vehicle M, the output of each output winding IA and IB is +1), +2
) can be expressed by the formula.

To X=, Bs1n θ ・−・・
・(11Y=, Bcos θ ・
...(2)(1), (In formula 21, θ is the angle that each output winding makes with the magnetic field caused by the earth's magnetism, and K,..., depends on the output gain of each output winding. B is the magnetic flux density due to the earth's magnetism.

These χ-axis components and y-axis components are shown in Figure 4, X and Y, respectively.
is shown by the curve.

The figure shows the case of a circle.

Next, by magnetizing the body and other iron parts, the magnetic flux density Be
is superimposed on the magnetic flux density from the earth's magnetism as an error, the output of each of the output windings IA and IB becomes +31. (51
It is expressed by the formula.

X' =, Bs1n θ0, Be5in ψ
・・・・・・(3) Y' = K, Bcos θ+
Becos ψ Old... (4) Here, Be is the magnetic flux density due to magnetization, and ψ is the angle formed by the magnetic field due to magnetization and the straight vehicle traveling direction F.

The above equation (3) is shown by the curve X', and the equation (4) is shown by the curve L'
Indicated by NY'. And these +31. +41
The error component KXBe of the above equation (31, (41)
sinψ.

The vector {circle around (2)} shown by K, 13esin ψf is the azimuth vector (error vector) in which the azimuth sensor 10 detects magnetization.

As shown in the above, the trajectory drawn by the force vector indicated by the output of the direction sensor +10 becomes a circle or an ellipse, and when the body steel plate or other iron part hole of the vehicle M is magnetized, the magnetic flux caused by the magnetization causes the trajectory drawn by the direction vector to become a circle or an ellipse. remains a circle or ellipse and its center moves.

As a method for correcting such an error caused by magnetization, a method is conventionally known in which the center of a magnetized circle or ellipse is found and the center is filled in to correct the output of the orientation sensor 10.

The above is the operation when the magnetic field is uniform because it is a geomagnetic vertical direction that detects orientation + lO. Below, orientation sensor 1
A case where a magnetic substance exists near 0 will be explained.

As mentioned in the above-mentioned configuration, the direction sensor 10 detects the straight direction F of the vehicle M and the output winding Ll I of the direction sensor +10.
It is attached so that it is parallel to A.

@Figure 6 shows the positional relationship between the position P and the magnetic ball B nearby when the orientation sensor 10 is installed in a vehicle.

Note that the magnetic material near the orientation sensor 10 is assumed to be a sphere, but this is an approximation of the magnetic material to a sphere to simplify the explanation. In addition to having one magnetic body as shown in FIG. 6, there are countless magnetic bodies such as holes in the body steel plate and other iron parts on the open surface of the orientation sensor IT.

Now, when the vehicle M rotates in all directions while maintaining the relative positional relationship between the magnetic ball B and the position P of the orientation sensor IO in FIG. 6 and the attachment of the orientation sensor +10 in the vehicle M, As shown in FIG. 6, the orientation sensor 10 rotates around the circumferential surface of the magnetic ball. Since the magnetic field caused by the earth's magnetism around the magnetic sphere B is distorted by the magnetic sphere B, the orientation sensor 10 detects this magnetic field. When such a distorted magnetic field is detected, the force position vector s< Book # h< indicated by the two-direction component values X and Y of the orientation sensor 10 is Direction Monsa 10 position P
It changes depending on the positional relationship with the magnetic sphere B, and becomes an ellipse distorted in the direction of the magnetic sphere B.

FIG. 7 shows the locus drawn by the azimuth vector in each positional relationship and the azimuth vector corresponding to east, west, north, south (w, a, s, N) by changing the positional relationship between the magnetic sphere B and the azimuth sensor 10. This is what is illustrated.

As shown in FIG. 7, the trajectory drawn by the orientation vector of the orientation sensor 10 becomes a distorted ellipse, and the way the ellipse is distorted changes depending on the positional relationship and distance between the orientation sensor 10 and the magnetic sphere B. In addition, the direction that Kiri should point and the direction sensor 1
0 is different from the detected direction. For example, when the azimuth sensor 10 is fixed at the position P shown in FIG. 6, the locus drawn by the azimuth vector of the azimuth sensor 10 becomes an ellipse Pc in FIG. 7. Also, the direction sensor 10 when pointing north (N)
The force position vector of is directed to the west (W).

The ellipse drawn by the directional vector is the ellipse of the azimuth sensor 10.
It is determined by the positional relationship between the
However, when the orientation sensor 10 is mounted on a vehicle, the positional relationship between the orientation sensor 10 and the surrounding magnetic material is fixed, so the orientation vector of the orientation sensor 10 is drawn, and the deviation between the trajectory and the orientation is constant. Become.

Therefore, the present invention measures this azimuth deviation in advance, and
The output of the direction sensor 10 is corrected based on this.

FIG. 8 shows a flowchart showing the operation of the microcomputer 22 of this embodiment.

The microcomputer 22 of this embodiment starts executing the flowchart shown in FIG. 8 when the power is turned on.

In step 801, memory initialization is performed.

In step 801, it is determined whether the magnetization correction switch 3 is open or closed. If this is open (if OFF) “No”
If it is closed (ON), it branches to "Yes". If it branches to “Yes”, the process advances to step 803.

In step 803, an error in the detected orientation of the orientation sensor 10 due to the magnetization of the body EL and other bolt parts is calculated.

This is calculated, for example, by approximately rotating the vehicle M and based on a predetermined azimuth vector during this rotation. Upon completion of the process in step 803, the process advances to step 804. Also, if the branch is “No” at step 802, step 800
Proceed to step 4.

In step 804, output values χ and y of components in two directions of the orientation sensor 10 are input. Here, digital values Aχ and Ay that have been A/D converted by the A/D converter 21 are input.

In step 805, magnetization correction is performed. That is, based on the magnetization error calculated in step 803, Aχ is corrected to Aχ' and Ay is corrected to Ay'.

In step 806, the detected azimuth DC is calculated based on the magnetization-corrected Aχ' and Ay'.

This Dt is calculated by the following (5) 2, 1, -
In step 807, distortion caused by the magnetic material is corrected. That is, the true azimuth Dr is determined from the detected azimuth Dt using the Dt-Dr table shown in FIG.

The Dt-Dr child table shown in FIG. 9 is stored in the ROM 23 in advance. In this embodiment, a table of the detected azimuth Dt and the true azimuth Dr was created with the azimuth detecting device shown in FIG. 2 mounted on the vehicle M. 9th
In the diagram, all directions are divided into 16, and the detected azimuth Dt and true azimuth Dr in each direction are made to correspond. Then, the true azimuth Dr is obtained from the detected azimuth Dt by approximating a straight line between each of the 16 divided azimuths by linear interpolation.

In step 808, the azimuth is displayed on the liquid crystal display device 4 based on the true azimuth Dr obtained in step 807. Then, the process returns to step 802 and repeats the above-described flowchart.

With the configuration and operation of this embodiment as described above, the azimuth detection device of this embodiment corrects the error in the detected azimuth angle of the azimuth sensor 10 due to the distortion of the earth's magnetic field generated by the magnetic material mounted on the vehicle M. , the true azimuth that should originally be indicated can be found.

The configuration of this embodiment is as described above, but
Various other embodiments can be applied to each of these configurations. For example, the orientation sensor 10 of the orientation detection device 1 of this embodiment is a Franks gate type in which a toroidal core is wound. A direction sensor can be configured. Further, although the orientation in this embodiment is displayed on the liquid crystal display device 4 as a 16-division orientation, it is also possible to display the orientation steplessly using a dot matrix type liquid crystal display device, a CRT display device, etc. The orientation obtained by the device of this embodiment may be output to a vehicle navigation device that provides travel guidance for the vehicle.

In the above embodiment, a t-Dr child table as shown in FIG. 9 is created and stored in advance, and linear interpolation is performed between each of the 16 divided directions, but the direction display is limited to the 16 divided display. Then, as shown in Figure 10, G Dr
Child tables are also good. This stores the detected azimuth Dt, which is the boundary between each of the 16 divided azimuths, and the azimuth to be displayed in association with each other. In such a case, N is determined by determining in which range the detected azimuth Dt falls.

16 directions of NNE, NE to NNW can be determined. For example, when the detected azimuth angle Dt=15 ('), the azimuth is "N".

In the example described above, the increments of the table are the true azimuth angle Dr
is evenly spaced every 22.5°, but the detected azimuth angle Dt
Alternatively, if the major and minor axes of the ellipse of the azimuth circle are included in the points of the table, the azimuth accuracy can be ensured even if the increments are wider (fewer points).

The increments of this table, that is, the number of points, affect the accuracy when converting the detected azimuth Dt to the true azimuth Dr, so it is appropriate to consider both the memory capacity of the ROM 23 required for the table and the azimuth accuracy. must be selected.

Furthermore, in the above embodiment, the detected azimuth Dt and the true azimuth D
Although the conversion of r was performed using a table, it is also possible to convert this using an approximate expression.

11 and 12 show examples of approximation using trigonometric functions, and the difference between the detected azimuth Dt and the true azimuth Dr is Dt-
Since it can be approximated by Dr#ΔDsin (2Dt-φ), the true azimuth Dr is calculated by Dr';Dt-ΔDsin (2Dt-φ). This can be applied when the magnetic body can be regarded as one, and moreover, can be regarded as a substantially spherical body.

When there are clearly multiple magnetic bodies or their shape cannot be considered as a sphere or spheroid, Dt and Dr
The conversion of the difference between is a complex function. But in this case too,
Since the function of the difference between Dt and Dr remains unchanged based on the positional relationship between the magnetic body and the orientation sensor, this function may be approximated by a polynomial.

If the true azimuth Dr is determined from the detected azimuth Dt using an approximate expression in this way, there is no need for memory capacity for storing a table.

Furthermore, although the azimuth angle conversion table or approximate expression is created by experimentally measuring the relationship between the true azimuth angle Dr and the detected azimuth angle Dt, the mounting of the azimuth sensor 10 is based on the electromagnetic theory of the earth's magnetic field at the position. It may be created by analysis.

In addition, instead of creating an azimuth angle conversion table in advance before it is installed on a vehicle,
The table may be created by the operator inputting several reference directions and determining the direction detected by the direction sensor at that time. In this way, distortions in the earth's magnetic field, which vary from vehicle to vehicle, can be corrected by various devices mounted on the vehicle.

[Brief explanation of drawings]

FIG. 1 is a diagram corresponding to the claims of the present invention, and FIG. 2 is a block configuration diagram of a direction detecting device that is an embodiment of the present invention.
Figure 3 is a waveform diagram of each part of the direction detection device shown in Figure 2.
The figure is a perspective view showing the mounting state of the direction detection device on a vehicle, FIGS. 5 to 7 are illustrations of the operation of the direction detection device shown in FIG. 2, and FIG. A flowchart showing the operation of the microcomputer 22, FIG. 9 is an azimuth conversion table stored in the ROM 23 of the azimuth detection device shown in FIG. 2, FIG. 10 is an azimuth conversion table as another embodiment, and FIG. FIG. 12 is an explanatory diagram of another embodiment in which the true azimuth angle is determined from the detected azimuth angle using an approximation formula. 1... Orientation detection unit, IA... Output winding (χ axis), I
B...Output winding mCy axis), 2...Control unit, 3...
Magnetization correction switch, 4...Liquid crystal display device 221...
A/D converter, 22... microcomputer,
23...ROM, 24...RAM, 25...Liquid crystal drive circuit.

Claims (3)

[Claims] (1) An azimuth sensor that is attached to a moving object including a magnetic material at a predetermined position relative to the magnetic material and detects the direction of the earth's magnetic field by decomposing it into components in two orthogonal directions; a storage means for storing the degree of influence of the magnetic body on the detected direction indicated by the output values of the components in the two directions of the direction sensor; An azimuth detecting device comprising: a correction means for correcting a detected azimuth indicated by an output value of a component. (2) The storage means stores a relationship between an arbitrary direction and a detected direction indicated by output values of components in two directions of the direction sensor in this arbitrary direction. The direction detection device according to item 1. (3) The correction means corrects the detected orientation to the arbitrary orientation based on the relationship between the arbitrary orientation stored in the storage means and the detected orientation. The direction detection device according to item 2.