JPS6244207B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a direction measuring device for measuring the traveling direction of a moving object such as an automobile or a small boat.

[Conventional technology]

Conventionally, so-called compasses that utilize the rotation of magnets due to the earth's magnetic field have been used for the above purposes, but these conventional compasses have drawbacks such as slow response speed and decreased accuracy due to increased mechanical friction. ing.

Therefore, an electronic compass that electronically detects the direction of the earth's magnetic field has been proposed, but when using this electronic compass to electronically detect the direction of the earth's magnetic field on a moving object such as a small boat or car, there is no way to do that. However, since it is affected by the magnetism of the moving body itself, it is necessary to compensate for this by some means.

[Problem that the invention seeks to solve]

In order to achieve the above purpose, there is a method of arranging multiple permanent magnets around the part that detects geomagnetism, but this method has drawbacks such as difficulty in completely compensating and requiring a long time for adjustment. . Therefore, in a conventional electronic compass, two windings are wound perpendicularly to include the geomagnetic sensing part, and the measurement result is determined to be true north (or true south) when the moving object is facing true north (or true south). Adjust the current supplied to one winding so that the winding is facing due east (or due west), then adjust the current supplied to the other winding so that the measurement result is due east (or due west) with the moving object facing due east (or due west). By adjusting the current supplied to the line,
A method is used to cancel the error magnetic field. This method allows for almost perfect correction, but it has drawbacks such as the need to know the true north, south, east, west, and east directions before making adjustments, and the fact that adjustments are made while checking the measurement results manually, so it takes time to make adjustments. It was hot.

The present invention was made in view of such conventional problems, and an object of the present invention is to provide a simple direction measuring device that automatically compensates for error magnetic fields caused by the moving object itself and does not require human operations during adjustment. shall be.

[Means to solve the problem]

Here, when a magnetic sensor (moving body) is rotated and output signals corresponding to two-direction U and V components obtained from the magnetic sensor at a plurality of rotational positions are plotted, the locus becomes a circle or an ellipse. In this case, the influence of the moving body's own error magnetic field is
This corresponds to the amount of shift of the center of the circle or ellipse from the origin of the detection reference axis of the bidirectional outputs EU _{and EV} . The direction measuring device according to the present invention has been developed with this point in mind, and is designed to calculate a signal to compensate for the influence of the magnetic field of the moving object itself.

That is, a detection unit that detects the horizontal components of the magnetic field of the mobile body itself and the earth's magnetism, and detects the respective components _EU and _EV in the traveling direction of the mobile body and in the direction perpendicular thereto;
A _{circle or} Find the intersection of the elliptical locus and the detection reference axes of the components _EU and _EV , find the center positions of the circle or ellipse E _UO and E _VO , and determine whether the center position is the intersection of the detection reference axes (origin)
, and an output terminal for outputting a magnetic detection signal with the error magnetic field compensated for.

[Effect]

In this invention, a coil for applying a correction magnetic field is provided to the magnetic detection section, and a current for error magnetic field correction obtained according to the procedure below is supplied to this coil, and the error magnetic field generated by the moving object itself is Correct.

That is, the moving body is rotated and magnetic sensor outputs E _Ui and E _Vi at a plurality of rotational positions are obtained. Then, the intersection point between the locus of the circle or ellipse drawn by this sensor output and the detection reference axis is determined, and the center position of the circle or ellipse is determined from these points. Next, a current for error magnetic field correction is supplied to the coil so that this center position coincides with the intersection (origin) of the detection reference axis.

After the error magnetic field caused by the moving body itself is corrected in this way, accurate direction measurement becomes possible using the two-directional component output from the magnetic sensor.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a direction measuring device according to an embodiment of the present invention. In the figure, 1 is a magnetic sensor attached to a moving body and outputs two signals corresponding to the applied magnetic field, and a magnetic sensor 10 and It is composed of correction magnetic field generating sections 11 and 12. The correction magnetic field generating sections 11 and 12 are a pair of coils wound around the detection section 10 so as to be orthogonal to each other. 2
Reference numerals 0 and 21 are amplifiers that respectively amplify the two signals obtained from the magnetic sensor 1 and output a DC signal, and 200 and 210 are output terminals from which the outputs of the amplifiers 20 and 21 appear. A main body 5 is configured.

Further, 3 calculates at least two signals for compensating for the influence of the magnetic field on the earth's magnetic field by the moving body itself from a plurality of sets of signals obtained from the amplifiers 20 and 21 at a plurality of rotational positions of the magnetic sensor 1. An arithmetic circuit 4 converts the output of the arithmetic circuit 3 into correction magnetic field generating coils 11 and 12 of the magnetic sensor 1.
This is a conversion circuit that converts the signal into a signal suitable for application to the

Next, the basic principle of arithmetic processing in the arithmetic circuit 3 will be explained.

FIG. 2 is a diagram showing the relative relationship between the magnetic sensor 1, the earth's magnetism H, and the error magnetic field H _E , and shows 1U and 1V.
indicates the detection reference axis of the magnetic sensor 1. In FIG. 2, consider a state in which the error magnetic field H _E due to the magnetism of a moving body (not shown) is zero. In other words, consider a state in which a magnetic field of strength H is applied to the magnetic sensor 1 at an angle θ with one detection reference axis 1U.

In this case, the output terminals 10U, 1 of the magnetic sensor 1
When the signals obtained at 0V are ev and eu, respectively, ev and eu are given by the following equations.

eu=K ₁ H·cosθ (1) ev=K ₂ H·sinθ (2) Here, K ₁ and K ₂ are constants related to the sensitivity of the magnetic sensor 1 to each detection reference direction. The above eu and ev are amplified by amplifiers 20 and 21, and output terminals 200 and 210 of the amplifiers 20 and 21
The outputs _EU and _EV are obtained. In this case, the amplifier 20,
Letting the amplification degrees of 21 be G ₁ and G ₂ respectively, the outputs E _U and _EV are E _U =G ₁ eu=K ₁ G ₁ cosθ…(3) _EV =G ₂ ev=K ₂ G ₂ sinθ… (4) is given by Here, if K ₁ G ₁ = K _U and K ₂ G ₂ = K _V , then E _U = K _U H·cosθ (5) E _V = K _V H·sinθ (6). Therefore, the angle θ between the detection reference axis 1U of the magnetic sensor 1 and the earth's magnetism is θ=tan ^-1 (sinθ/cosθ)=tan ^-1 (K _U E _V /K
_V E _U ). Here, since the constants K _U and K _V are known, the output signals EU and K _V of the amplifiers 20 and 21 are
It can be seen that the angle θ can be obtained from _EV . Therefore, by aligning the detection reference axis 1U with the moving direction of the moving object, the moving direction of the moving object can be measured.

The above explanation has been made for the case where the error magnetic field H _E is zero in FIG. 2. The case where the error magnetic field H _E is not zero will be described next.

As shown in FIG. 2, when the error magnetic field H _E is applied at an angle φ with respect to the detection reference axis 1U of the magnetic sensor 1, similar calculations are performed to obtain E _U =K _U (Hcosθ+H _E cosφ ) ...(8) E _V =K _V (Hsinθ+H _E sinφ) ...(9) is obtained. In this case, generally tan ^-1 (K _U E
Since _V /K _{V EU} ) is not equal to θ, an error occurs when the moving direction of the moving body is measured using the method described above. In order to eliminate this error, as shown in FIG.
2 are provided. That is, this correction magnetic field generation section is a pair of coils 11 and 12 wound around the detection section 10 of the magnetic sensor 1 so as to be perpendicular to each other (see FIG. 3), as described above. When currents I _V and I _U are applied to the detectors 11 and 12, respectively, magnetic fields H _U and H _V are applied to the detection unit 10 as shown in FIG. At this time, the magnetic fields H _U and H _V can be expressed as follows using constants L _U and L _V.

H _U = L _U I _U …(10) H _V = L _V I _V …(11) Now, when we assume the composite vector H _C of the magnetic fields H _U and H _V , the magnitudes of H _C and H _E are equal, If the direction is reversed, the error magnetic field can be effectively canceled. Therefore, in order to cancel the error magnetic field, the following equation needs to hold true.

H _U =-H _E cosφ (12) H _V =-H _E sinφ (13) Conventionally, the error magnetic field H _E was canceled by manually adjusting the currents I _U and _IV .

Now, in the state where the error magnetic field H _E exists, as mentioned above, equations (8) and (9) hold, so (E _U /K _U −H _E cosφ) ² + (E _V /K _V −H _E sinφ) ² = H ² (cos ² θ + sin ² θ) = H ² (14) holds. By rearranging the above equation, we get the following equation.

(E _U −K _U H _E cosφ) ² /K _U ² +(E _V −K _V
H _E sinφ) ² /K _V ² = H ² (15) When considering the outputs _{EU and EV} of the amplifiers 20 and 21 as variables, the above equation is a circular equation if K _U =K _V. , K _U ≠ K _V , it is an elliptic equation.
In this case, the influence of the error magnetic field H _E corresponds to the amount of shift from the center of the circle or ellipse.

Therefore, the center (E _UO , E _VO ) of the circle or ellipse can be found by appropriately rotating the moving body and finding the outputs EU and _EV for _a plurality of values of θ. Once the center of the circle or ellipse (E _UO , E _VO ) is found, E _UO = K _U H _E cosφ…(16) E _VO = K _V H _E sinφ…(17) Therefore, we can apply the error magnetic field H _E. Current I _U for extinguishing,
I _V is determined by the following formula.

I _U =-H _E cosφ/L _U =-E _UO /K _U L _U …
(18) I _U =-H _E sinφ/L _V =-E _VO /K _V L _V …
(19) Here, the constants L _U and L _V are known, and in many cases the constants K _U and K _V are also known, so the correction can be made by finding the coordinates E _UO and E _VO of the center of the circle or ellipse. The required currents I _U and I _V can be found by simple calculations as described above. In addition, even if the constants K _U and K _V are not known, by selecting the measurement points appropriately, the constant K
_U and _KV can be found.

FIG. 4 is a diagram explaining the simplest calculation method, in which the horizontal axis E _U and the vertical axis E _V are taken, and the width scales 20, 21 are
The signals _EU obtained at the output terminals 200, 210 of
The locus of the point ( _EU , _EV ) determined from _EV is shown by an ellipse. Points P, Q, where the ellipse intersects the horizontal and vertical axes,
Let the coordinates of R and S be P(E _U1 , 0) and Q
(0, E _V1 ), R (E _U2 , 0), S (0, E _V2 ), the coordinate components of the center O (E _UO , E _VO ) are E _UO = (E _U1 +E _U2 )/2 ...(20) E _VO = (E _V1 + E _V2 )/2 ...(21) It is obtained as follows.

The procedure for executing the above-mentioned correction using the apparatus shown in FIG. 1 is shown below. First, when an instruction to perform correction is given to the device shown in Figure 1 from the outside,
The arithmetic circuit 3 has input terminals 200 and 210 at that time.
Output terminals 300, 310 regardless of the voltage of
The voltages R _U and R _V of both are set to zero. As a result, the signals I _U , 410 at the output terminals 400 and 410 of the conversion circuit 4
I _V also becomes zero, and the correction becomes zero, that is, the state is uncorrected.

Next, when the moving object to which the magnetic sensor 1 is attached is rotated at a suitable time by human operation, the signal voltages E _Ui and E _Vi input to the arithmetic circuit 3 will be shaped like an ellipse or an ellipse as shown in FIG. Draw a circle. At this time, _the intersection point P ₍ E _U
1 , 0), Q (0, E _V1 ), R (E _U2 , 0), S
From the values of (0, E _V2 ), the center position O (E _UO , E _VO ) is determined according to equations (20) and (21). Accordingly, the signal voltages of the output terminals 300 and 310 of the arithmetic circuit 3 are set such that the center position O coincides with the intersection (origin) of the detection reference axes EU _{and EV} , R _U =-E _UO /K _U L _U M _U ...(22) R _V =-E _VO /K _V L _V M _V ... (23) is output. Here, M _U and M _V are the conversion coefficients of the conversion circuit 4, and from this, as mentioned above, I _U = M _U R _U = -E _UO / K _U L _U (18) I _V = M _V R _V =−E _VO /K _{V LV} (19), and the correction is completed by flowing these currents I _U and _IV to the correction coils 11 and 12 of the magnetic sensor.

After the error magnetic field is corrected in this way, the output of the magnetic sensor 1 becomes one in which the magnetism caused by the moving body itself is compensated, and therefore the output terminals 200, 21
The correct direction can be measured by calculating the angle θ using the two signals obtained at 0 according to the above-mentioned equation (7). For example, the detection output (E
When either _U , _EV ) is zero, that is, (0, +E _Vi )
If it is east, if (0, -E _Vi ), it is west, (-E _Ui ,
0), it is south, and (+E _Ui , 0), it is north.

Since the calculation is simple, the calculation circuit 3 can be implemented using an analog circuit, but considering the necessity of storing the data necessary for calculation and the storage of calculation results, it is possible to implement the calculation circuit 3 using a digital method, especially a microcomputer. method is optimal.

FIG. 5 is a block diagram of an arithmetic circuit using a microcomputer, in which 30 is an AD converter for converting the output signals _EU and _EV of the amplifiers 20 and 21 into digital signals, 31 is an arithmetic control circuit; A microcomputer 32 that holds data is a DA converter that converts a signal output from the microcomputer 31 into an analog signal. As the conversion circuit 4, a voltage-current converter is required for the magnetic sensor 1 having the structure shown in FIG. 3, but when the resistance of the coils 11 and 12 is low in FIG. As shown in Fig. 6, the resistor 40,
A circuit consisting only of 41 is sufficient.

If the magnetic sensor 1 is corrected in this way, the error magnetic field H _E caused by the moving object itself is replaced by the magnetic fields H U , H _V generated by the currents I _U , IV flowing through the coils 11 and 12 of the magnetic _{sensor 1.} Therefore, the magnetic field H can be accurately measured, and the traveling direction of the moving body can be accurately measured. Here, the direction may be measured by inputting the signals obtained at the output terminals 200 and 210 to other equipment, or
Alternatively, it may be determined by the arithmetic circuit 3.

Note that once the procedure for correcting the error magnetic field is performed, it is not necessary to perform it every time the direction is measured. However, if the magnetization of a moving object such as a car body changes for some reason, errors will appear in the direction measurement results. The advantage of the present invention is that it can be done automatically without much need.

〔Effect of the invention〕

As described above, according to the present invention, an arithmetic circuit is added to the main body of a measuring device equipped with a magnetic sensor and an amplifier, and the influence of the magnetic field of the moving body itself is determined from multiple sets of signals obtained at multiple rotational positions of the magnetic sensor. Since we have determined a signal to compensate for the above effects and added it to the measurement device itself to compensate for the above effects, it is possible to cancel the error magnetic field without having to perform troublesome manual corrections, making it suitable for automobiles and small boats. It is extremely useful as a direction measurement device.

[Brief explanation of the drawing]

Fig. 1 is a circuit configuration diagram of a direction measuring device according to an embodiment of the present invention, Fig. 2 is a diagram showing the relative relationship between a magnetic sensor, the earth's magnetism, and an error magnetic field, and Fig. 3 is a diagram showing a magnetic sensor equipped with a correction magnetic field generating coil. A perspective view showing the structure of the sensor, Fig. 4 is a diagram for explaining the correction calculation method, Fig. 5 is a circuit configuration diagram of an arithmetic circuit using a microcomputer, and Fig. 6 is a circuit showing an example of a conversion circuit. It is a diagram. 1... Magnetic sensor, 20, 21... Amplifier, 3
...Arithmetic circuit, 5...Measuring device main body, 60, 61
...Adder. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Scope of Claims] 1. A direction measuring device that outputs a signal for measuring the traveling direction of a moving body by compensating for the influence of the magnetic field of the moving body itself, which is attached to the moving body and is attached to the moving body. a detection unit that detects horizontal components of its own magnetism and geomagnetism, and outputs a signal corresponding to a component in the traveling direction of the moving body and a signal corresponding to a component in a direction perpendicular to the traveling direction, and this detection unit a magnetic sensor consisting of a pair of correction magnetic field generating coils wound perpendicularly around the sensor to apply a correction magnetic field to the detection section; and a magnetic sensor that amplifies two signals obtained from the magnetic sensor. An amplifier that outputs a DC signal, and the intersection of the detection reference axes in the two directions with the circular or elliptical locus drawn by a plurality of sets of signals obtained from the amplifier at a plurality of rotational positions of the magnetic sensor, and the Find the center position of the circle or ellipse,
computing means for supplying a current for error magnetic field correction to the correction magnetic field generation coil so that the center position coincides with the intersection of the two detection reference axes; 1. A direction measuring device comprising: an output terminal for outputting two signals obtained from the method.