JPS6154163B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an azimuth meter mounted on an automobile, a ship, etc. that utilizes geomagnetism.

A compass that uses the earth's magnetic field is naturally affected by the magnetic field of the vehicle or ship. In other words, because the bodies of cars and ships are made of steel, they become magnetized, and this magnetism disturbs the direction of the earth's magnetic field.

First, a method for detecting geomagnetism, which is related to the present invention, will be described. The direction of the horizontal component of the geomagnetic field is used as a reference for the method, and various means have been considered for detecting the horizontal component direction of the geomagnetic field. I will explain how to find the direction from the alternating current electromotive force generated. In Figure 1,
Reference numeral 1 denotes a vertical rotation axis, which is rotated by a motor 14. A magnetic body 2 is fixed to the rotating shaft 1 and rotates, has wings 15 and 16 at both ends, and passes through the coil 4. Coil 4 is bobbin 3
The wire is wound around the wire, and both ends thereof are taken out to terminals 5 and 6. The coil 4 is placed concentrically with the rotating shaft 1 and fixed so as not to rotate. These magnetic bodies 2 and coils 4 constitute a geomagnetism detection section. 7 is a semicircular optical shutter that is fixed to the rotating shaft 1 and rotates, and 8 and 9 are photoelectric switches, each of which is shifted by 90 degrees with respect to the rotating shaft 1. 10 and 11 are output terminals of the photoelectric switch 8, and 12 and 13 are output terminals of the photoelectric switch 9. The magnetic body 2 and the optical shutter 7 rotate at the same time about the rotating shaft 1. The optical shutter 7 and photoelectric switches 8 and 9 constitute a synchronizing signal generating section.

Next, the outputs obtained from the coil 4 and photoelectric switches 8 and 9 will be described.

First, talking about the signal obtained from the coil 4, the magnetic body 2 passes through the coil 4 and is rotated by the shaft 1. At this time, the magnetic body 2
These wing parts 15 and 16 guide the horizontal component of the earth's magnetic field as shown in FIG. That is, when the horizontal component of the earth's magnetism is oriented from left to right in the paper, the magnetic flux is collected at the wings 15 and 16 of the magnetic body and flows vertically through the inside of the magnetic body 2. Therefore, a perpendicular magnetic flux passing through the center of the coil 4 is generated. Without the magnetic body 2, there would be no vertical magnetic flux passing through the center of the coil 4, and the magnetic body 2 with wings converts the horizontal component of the earth's magnetism into a vertical component. Therefore, when the magnetic body 2 is rotated by the vertical rotation axis 1, the horizontal component of the earth's magnetism passes through the magnetic body 2 while being converted into a vertical component while periodically changing its magnitude and direction. This situation is clear in Figure 3. FIG. 3 is a top view of FIG. The wing parts 15 and 16 of the magnetic body 2 form an angle wt with the horizontal component of the earth's magnetism. However, w is the rotational angular velocity of the magnetic body 2, and t is time. When t=0, that is, when the blade parts 15 and 16 are in the same direction as the horizontal component of the earth's magnetism, if the magnetic flux passing through the magnetic body 2 perpendicularly (at right angles to the paper) is F ₀ , then the direction in which the blade becomes wt , a magnetic flux of the magnitude F ₀ coswt naturally passes through the magnetic body 2. This magnetic flux passes through the coil 4, and therefore an electromotive force is generated in the coil 4 due to a change in the magnetic flux F ₀ coswt. That is, E∝d/dt(F ₀ coswt) ∝F ₀ sinwt, and an AC electromotive force having the same period as the rotation of the shaft 1 is generated in the coil 4. The moment when the wing parts 15 and 16 are oriented in the magnetic direction is the moment when the magnetic flux is the largest and the change is the smallest, so the electromotive force is zero. This also appears in the formula above. This is shown in Figure 5a.

Next, the signal output obtained by the synchronization signal generator will be described. Photoelectric switches 8 and 9, which are made up of a pair of light-emitting elements and light-receiving elements, can be turned on and off by an optical shutter 7.
It is possible to obtain ON-OFF output. Such photoelectric switches or photocouplers are arranged 90 degrees apart from each other about the rotation axis 1. On the other hand, a semicircular optical shutter 7 is fixed to the rotating shaft 1 and rotates together with the rotating shaft 1. Since the shutter 7 is semicircular, the optical path of the photo coupler is turned on and off every half rotation during one rotation. Therefore, the photo coupler's electrical output terminal is ON.
A rectangular wave with a duty ratio of 1 is obtained where the -OFF periods are equal. Since the positions of photo couplers 8 and 9 are shifted by 90 degrees, the phase of the square wave output obtained from each is 90 degrees.
It is shifted by °. These outputs are shown in Fig. 5b and c.

This completes the explanation of the signals obtained from each part in FIG. 1, and now we will discuss the direction signals obtained from these signals. Among the signals a, b, and c shown in Figure 5, the rectangular waves b and c are obtained repeatedly over time without any relation to the direction of the geomagnetic field, but the alternating current signal a is the horizontal component of the geomagnetic field. A change in phase appears depending on the direction of . That is, the wing portion 1 of the rotating magnetic body 2
This is because the timing at which the magnets 5 and 16 point in the direction of the horizontal component of the earth's magnetism differs depending on the direction of the earth's magnetism. As shown in FIG. 5, it is assumed that the phase difference between waveforms a and c is θ°, and the phase difference between waveforms b and c is 90°. When AC signal a is switched with synchronous signal b, the average DC voltage V _Y ∝∫〓 ⁺⁹⁰゜〓 _-90 sint・dt∝sinθ When AC signal a is switched with synchronous signal c, the average DC voltage V _X ∝∫〓 ⁺¹⁸⁰゜〓sint・dt∝cosθ is obtained.

From these V _X and V _Y , θ is determined as V _Y /V _X =tan θ, θ=tan ⁻¹ V _Y /V _X.

By the way, in the direction meter mentioned above, each a,
An example of the arrangement of the magnetic body 2, optical shutter 7, and photo couplers 8, 9 for realizing signals b and c including their phases is shown in FIG. 4 when viewed from the direction of the rotation axis. Here, the semicircular shutter 7
Assume that the magnetic body 2 is fixed to the rotation shaft 1 and rotates in the direction of the arrow, and that it has an angle of 0° with the X-axis with the direction of the horizontal component of the earth's magnetism in the direction of the photo coupler 9. The photo coupler 8 is provided at an angle of 9 and 90 degrees, and the Y axis is considered in that direction. In FIG. 4, the optical shutter 7 shows the moment when the photo coupler 9 is opened, that is, the moment when it is turned on, and the photo coupler 8 is already opened and turned on.
It is becoming. Furthermore, since the wing portions 15 and 16 of the magnetic body 2 have already turned by θ° from the position perpendicular to the magnetic flux, the electromotive force of the coil 4 is at the instant of the value of sin θ°. The output of the photo coupler 9 is the output c in FIG. 5, and the output of the photo coupler 8 is the output b in FIG. In FIG. 4, the blades 15 and 16 are fixed to the shaft 1 so that the direction of the shutter 7 and the diameter line of the shutter 7 are exactly perpendicular to each other.

By the means described above, the direction is determined from the phase difference between the phase of the AC electromotive force obtained by cutting the horizontal component of the earth's magnetism by a rotating magnetic sensing element and the phase of the synchronization signal obtained by the same rotational movement. can be found.

When trying to apply such a direction detection system to automobiles, ships, etc., a new problem arises due to the influence of magnetic materials in the car or ship's body. There are two problems here.

One is magnetism due to permanent magnetization of the car body, and the other is induced magnetization in the magnetic field of the car body. The former is an effect in which the body of a car acts as a magnet, adding another magnetic field to the earth's magnetic field, and the latter is the effect that the body of a car, etc., disturbs the earth's magnetic field. Induced magnetization depends on the shape of the vehicle body, etc., and the way it is disturbed changes depending on how the vehicle body is placed in relation to the earth's magnetism, so it cannot be said that there is a fixed effect. On the other hand, the influence of the inherent permanent magnetization of the vehicle body is constant. The present invention proposes a means for correcting the influence of this permanent magnetization.

First, the principle of the conventional method will be explained with reference to FIG.
In FIG. 6, the vector indicated by line segment OA is the horizontal component of the earth's magnetism, and the vector indicated by line segment OB is the magnetic vector due to permanent magnetization of the vehicle body, etc. At this time, the composite magnetic vector of the horizontal component vector of the earth's magnetism and the magnetism of the vehicle body becomes a line segment OC, and its direction deviates from the original direction of the earth's magnetism by an angle of Δθ, which causes an error. In order to avoid this error, a magnetic vector OB' having the same magnitude and opposite direction as the magnetic OB of the vehicle body can be added to cancel the magnetic vector OB. FIGS. 7 and 8 are examples of its implementation. Figure 7 shows a rotating magnetic body 2 and a coil 4 that are arranged close to each other on the coaxial line to obtain an alternating current electromotive force.
It is set so that the horizontal component of the leakage magnetism of the ring magnet 22 of the pole is exactly equal in magnitude to the horizontal component of the magnetic field of the car body, and the direction is opposite, so that the distance and direction of the magnet 22 from the power generation part can be freely adjusted. It is supported by pillars 21 so that it can be adjusted, and is fixed with screws 23 after adjustment. This method has a very simple structure because correction can be made with one magnet, but adjustment is a little troublesome. That is, it is necessary to adjust the distance and direction of the magnet while simultaneously changing it. In the example shown in FIG. 8, the adjustment can be performed in two separate and independent adjustments.

Figure 8 shows 2 wires wound in a crossed manner instead of a magnet.
An electromagnet is created by passing current through two coils 25 and 26.The positions of the coils are fixed, and the strength and direction of the magnetism required for correction can be freely created by changing the current. That is, in FIG. 6, the magnetic OB' required for correction can be considered by decomposing, for example, two orthogonal magnetic fields OD and OE, and these OD and OE can be produced separately by two coils. In accordance with this principle, FIG. 8 provides coils wound in directions perpendicular to each other. However, in general, it is natural that the coils are not necessarily orthogonal, but may be coils wound in two independent directions. The advantage of this method is that there is no need to adjust the size and direction at the same time.
If the magnitude of the excitation current is adjusted separately and independently in the two directions, the magnitude and direction will be determined as a result, making the adjustment easier. However, on the other hand, there are two drawbacks:
Two current sources are required to supply excitation current to one coil, and the current sources must be capable of arbitrarily varying the direction and magnitude of the current, resulting in a complex circuit.

The present invention eliminates the above-mentioned drawbacks and proposes a system that is simple in terms of structure and circuit.
First, the principle of the present invention will be described. In Figure 6, the AC electromotive force obtained by the composite magnetic field OC of the horizontal component OA of the earth's magnetism and the magnetic OB of the vehicle body can be broken down into the AC electromotive force due to the magnetic OA and the AC electromotive force due to the magnetic OB. It will be peace. Of course, this sum is a vector sum including magnitude and phase angle. This relationship is as shown in FIG. That is, in Fig. 9, the electromotive force a is the horizontal component OA of the earth's magnetism.
b is the electromotive force induced by the magnetic force of the car body.
In the electromotive force induced by OB, c is the electromotive force induced by the composite magnetic OC. The electromotive force that we actually obtain directly is c, while our desired electromotive force is a. Here, in order to obtain the electromotive force a, the electromotive force opposite to the electromotive force b must be
It is obvious that b' should be added to c. this
The electromotive force b' is equal to the AC electromotive force due to the correction magnetic field OB' in FIG.

Based on the above idea, the present invention, instead of creating a correction magnetism that cancels out the magnetism of the vehicle body as shown in FIGS. 7 and 8, obtains an AC electromotive force equivalent to that obtained by the correction magnetism by another means, and By adding the AC electromotive force to the AC electromotive force that includes the influence of the car body's magnetism, it is attempted to obtain an AC electromotive force that does not include the influence of the car body's magnetism.

The above correction AC electromotive force consists of two factors: phase and magnitude.
However, adjusting two factors generally requires two or more adjustment operations, and if the second adjustment is made after the first adjustment, the first adjustment If it is possible to perform a single independent adjustment that does not disrupt the adjustment, it is possible to complete the adjustment with only two adjustments. Assuming practical adjustment work in the case of a car, if you install a compass in the car and make adjustments, first place the car facing north and adjust it so that the compass indicates north, then It should be possible to position the car facing east and adjust the direction indicator so that it points east. At this time, it is fine if the initial northward adjustment does not change due to the eastward adjustment. However, the magnetism that disturbs the northbound direction is the left-right component of the vehicle body's magnetism, and the front-back component is irrelevant. Therefore, when adjusting northbound direction, only the left-right component of the vehicle body needs to be corrected. . Also, the magnetism that disturbs the eastbound direction is the front-rear component of the vehicle's magnetism, and has nothing to do with the left-right component. Therefore, when adjusting eastward, only the longitudinal component of the vehicle body needs to be corrected. For the above reason, it is possible to separately correct the longitudinal component and the lateral component of the vehicle body's magnetism. From this, we create an electromotive force due to the front-back magnetic field and an electromotive force due to the left-right magnetic field as corrected AC electromotive force, and adjust the level of the electromotive force due to the left-right magnetic field so that the north direction matches when facing north. Then, when the vehicle is facing east, the level of the electromotive force caused by the magnetic fields in the front and rear directions should be adjusted so that the east direction is matched. Above 2
The composite electromotive force of the AC electromotive force for each correction obtained by the two adjustments is an electromotive force that is equal in magnitude and opposite in phase to the magnetic electromotive force for correction.In other words, it is an electromotive force for correction. This is a correction alternating current electromotive force that matches the electromotive force caused by the magnetic field in both magnitude and phase. In this way, the two factors of correction electromotive force magnitude and phase can be replaced with two separate and independent adjustment levels. In the above explanation, north and east were selected as the adjustment directions, but it goes without saying that south and west may also be used.

If the correction AC electromotive force is divided into two AC electromotive forces as described above, the correction AC electromotive force b' in FIG. 9 can be decomposed into d and e as shown in FIG. 10.
Here, the two correction alternating current electromotive forces are out of phase by 90 degrees. This is because we have now considered the correction magnetism divided into two orthogonal directions: the front-rear direction and the left-right direction of the vehicle. Generally, any sinusoidal AC electromotive force can be decomposed into two orthogonal sinusoidal AC electromotive forces of the same frequency, so FIG. 10 shows a possible decomposition.

Next, the means for obtaining the electromotive force as described above will be described. FIG. 11 shows an example of its realization. FIG. 11 is the most fundamental one, and its rational development will be explained later.

In FIG. 11, component parts 1 to 16 and their roles are exactly the same as in FIG. 1. The parts for obtaining the corrected AC electromotive force related to the gist of the present invention are a magnet 30 and two coils 31 and 32. Reference numeral 30 is a ring magnet having two poles, N and S, which is fixed to the rotating shaft 1 and rotated by the motor 14 at the same time as the magnetic body 2 and shutter 7, which are other components. Coils 31 and 32 are provided close to the magnet 30, their axes are perpendicular to each other, and are held integrally with other components such as the coil 4, photo couplers 7 and 9, and motor 14. . As the magnet 30 rotates, an alternating current electromotive force is generated in the coils 31 and 32. One of the gist of the present invention is to apply this AC electromotive force as the correction electromotive force mentioned above.
Therefore, if the axes of the coils 31 and 32 are arranged so as to be orthogonal to each other, alternating current electromotive force having mutually orthogonal phases can be obtained. In order to apply the alternating current electromotive force obtained in these coils 31 and 32 as a correction electromotive force, the positions of the coils 31 and 32 must be set in advance to match the phases of the correction electromotive forces OD and OE in Fig. 6. For example, it should be installed at one location in each of the front-rear and left-right directions of the vehicle. This has the same meaning as setting the orientations of the correction magnetic field coils 24 and 25 in FIG. 8 in advance.

Two of the coils 31 and 32 obtained as above
Assuming that the two electromotive forces have phases d and e in FIG. 10, a correction alternating current electromotive force can be obtained by setting their levels to be equal to d and e. However, the fact that the phases are opposite is simply a phase inversion, and can be considered to be included in the level setting.

As described above, if these two corrected AC electromotive forces are added to the AC electromotive force that includes the influence of the magnetic force of the vehicle body, a corrected electromotive force can be obtained.

This addition is simply addition of alternating current signals, and may be performed using a circuit. FIG. 12 shows a simple implementation example.

In the circuit shown in FIG. 12, reference numeral 4 indicates a power generation coil based on the geomagnetic horizontal component, and 31 and 32 indicate coils for generating corrected alternating current electromotive force. Variable resistors 39 and 40 are connected to the coils 31 and 32. coil 31,
32 is provided with center taps 37 and 38,
By moving the sliders 41, 42 of the variable resistor, the alternating current electromotive force of the coils 31, 32 is adjusted between the center tap and the slider over a range from negative to positive. Therefore, in the connection shown in FIG. 12, the electromotive force of the coils 31 and 32 is added to the electromotive force of the coil 4 with its sign and magnitude adjusted.
With such a configuration, the corrected electromotive force can be combined and added without using an active circuit.

As described above, the present invention has the first feature that a current source for generating a static magnetic field is not required to perform magnetic correction of the vehicle body, and that adjustment can be performed by two single adjustments.

Next, we will discuss the development of this method.

In the implementation example shown in Fig. 11, an optical shutter 7 and two photo couplers 8 and 9 are provided in the synchronization signal generation section for phase detection, and the synchronization signals whose phases are shifted by 90 degrees from each other are generated. It has gained. However, on the other hand, if a correction alternating current electromotive force is separately obtained by the magnet 30 and coils 31 and 32, and these are also selected to be out of phase by 90 degrees, then this correction alternating current electromotive force is It can be used in place of the synchronization signal obtained from a photo coupler. This eliminates the need for a photo coupler and shutter. This is the second feature. However, in this case, with the connection shown in FIG. 12, the electromotive force of the coil 31 cannot be obtained independently of the ground potential, so a separate circuit connection is required. For example, the first
A configuration as shown in Figure 3 is required. In FIG. 13, the outputs of the correction AC electromotive force generation coils 31 and 32 are used as synchronization outputs, respectively, and are combined by an adder circuit 50 to form the final correction AC electromotive force, which output and the geomagnetic horizontal component power generation. The output of the coil 4 is combined in an adder circuit 51 to obtain an AC electromotive force corrected for the magnetism of the vehicle body.

Next, as another development, a method for obtaining the correction AC electromotive force without rotation will be described. As already mentioned, the AC electromotive force for correction can be obtained by rotation, and this AC electromotive force can be used as a synchronizing signal for phase comparison. In this case, the synchronizing signal for phase comparison is waveform b in FIG. , c is preferable, so when the correction AC electromotive force is used as a synchronization signal, the AC electromotive force is waveform-shaped and used as a rectangular wave.

Here, contrary to the above case, a means will be described in which the synchronizing signal for phase comparison also serves as the alternating current electromotive force for correction. That is, a rectangular wave synchronization signal is originally generated as a synchronization signal for phase comparison by the shutter and photo coupler shown at 7, 8, and 9 in Fig. 1, and if an alternating current signal is generated from this synchronization signal, the synchronization signal can be obtained. A correction alternating current signal that is in phase with is obtained.
As a means for this, for example, a PLL may be used to synchronize its phase with a rectangular wave signal. According to this means, although it is necessary to add a circuit such as a PLL, it can be realized using the conventional mechanism without newly providing an alternating current electromotive force generator for correction.

An example of this implementation is shown in FIG.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram of the compass, Figures 2 to 5 are illustrations of its operation, Figure 6 is an explanatory diagram of a conventional magnetic correction method for a compass, and Figures 7 and 8 are examples of the method. 9 and 10 are explanatory views of the magnetic correction method of the compass of the present invention, and FIG. 11 is a configuration diagram showing one embodiment of the compass of the present invention, and FIGS. 12 and 13.
14 are diagrams showing other embodiments of the compass. 1...Rotating shaft, 2...Magnet, 4...Coil, 7...Optical shutter, 8, 9...Photocoupler, 14...Motor, 30...Magnet, 3
1,32...Coil.

Claims (1)

[Scope of Claims] 1. A geomagnetism detection unit that obtains a first alternating current electromotive force by a magnetic sensing element that rotates around a vertical rotation axis and a horizontal component magnetic field of the earth's magnetism; a synchronization signal generation unit that obtains first and second synchronization signals having the same period as the AC electromotive force and a phase difference of 90 degrees; and the first AC electromotive force from the magnetic detection unit and the synchronization signal generation unit. a phase difference detection unit for detecting a phase difference between the first and second synchronization signals from the first and second synchronization signals; a means for determining the orientation based on the phase difference from the phase difference detection unit; It is equipped with an AC signal generation section that obtains first and second AC signals for correction having the same cycle as the AC electromotive force and different phases, and adjusts the amplitude of the AC signal from the AC signal generation section to an appropriate level. A direction meter characterized in that the geomagnetism detecting section is configured to cancel an error caused by the inherent magnetism of an object on which the geomagnetism detection section is installed by adding it to the first alternating current electromotive force. 2. The compass according to claim 1, wherein the first and second alternating current signals for correction are generated based on a synchronization signal. 3. The compass according to claim 1, characterized in that an alternating current signal generating section also serves as a synchronizing signal generating section. 4. The AC signal generator has a magnet that is fixed to a rotating shaft and rotates, and two coils that are placed close to the magnet, and the rotation of the magnet generates AC signals with different phases in the respective coils. The compass according to claim 1, characterized in that the compass is configured to obtain electric power.