JPH0337519A - Method and apparatus for detecting position - Google Patents

Abstract

PURPOSE:To obtain two-phase sine waves whose accuracy is positively improved and to enhance the accuracy in detecting the position of a moving body by directly taking fundamental wave components out of electric signals outputted from a plurality of detecting elements. CONSTITUTION:A constant voltage power source is supplied from the outside through a wiring harness 109, and a rotor 103 is rotated together with a rotary shaft 102. Then, six-phase wave signals are outputted from Hall elements 21a - 21f. When the intervals between the rotor 103 and the elements 21a - 21f are sufficiently far, the waveforms from the elements 21f - 21f become multi phase sine waves whose phases are shifted by 60 degrees. The output signals from the elements 21a - 21f undergo operations in weighting and adding circuits and subtracting circuits. The output signals from the elements 21a - 21f are multiplied by the sine coefficients and the cosine coefficients based on the phase differences of the respective output signals, and the results are added. Thus, the fundamental wave components of the output signals from the elements 21a - 21f are taken out.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a position detection method and device for detecting the position of a moving body that performs rotational motion or linear motion [Prior Art] Conventionally, magnetic type Or phase difference 9 from optical encoder
2. Description of the Related Art A position detection device is known that detects the position of a moving body that performs rotational motion or linear motion based on two 0 degree sine wave signals. In this position detection device, the accuracy of position detection of a moving body depends on the accuracy of two sine wave signals. For this reason, for example, in Japanese Patent Application Laid-Open No. 63-225124, the distance between the magnetic medium and the magnetic sensor changes due to the eccentricity of the magnetic medium as a moving body that performs rotational motion, and the signal output from the magnetic sensor changes. A position detection device is shown that is capable of creating a highly accurate sinusoidal signal even when the amplitude changes or is distorted.

[Problems to be Solved by the Invention] However, in the above-mentioned position detection device, a plurality of magnetoresistive element groups are provided so that the harmonic components with respect to the output fundamental wave are in opposite phases and cancel each other out. It is configured to extract only the fundamental wave component having a waveform. For this reason, it is necessary to install magnetoresistive elements with high precision at a special pitch, and the output fundamental wave is obtained by attenuating harmonic components. The ingredients must be removed, which is extremely difficult in practice.

The present invention has been made in view of the above points, and it reliably improves the accuracy of two-phase sine waves by extracting the fundamental wave component directly from the signal output from each detection element, thereby improving position detection. It is an object of the present invention to provide a position detection method and its position with improved accuracy.

[Means to solve the problem]

In order to achieve the above object, a position detection method and a device thereof according to the present invention include a movable body and a fixed body, and a position detection method according to the position of the movable body.
In a position detection device that generates two sine wave signals having a phase difference of 0 degrees and detects the position of the movable body using these sine wave signals, a multipolar magnet having a plurality of magnetic poles magnetized with opposite polarities at predetermined intervals; and a multipolar magnet disposed opposite to the multipolar magnet on either the moving body or the fixed body; a plurality of detection elements that detect the magnetic field generated by the multipolar magnet and convert it into an electric signal; and a sine coefficient and a cosine of the electric signals outputted from the plurality of detection elements based on the phase difference of these electric signals. and calculation means for calculating the two sine wave signals having the 90 degree phase difference by multiplying by coefficients and adding these, respectively.

[Effect]

With the above-described configuration, the present invention outputs periodic electrical signals from each detection element as the moving object moves. These electrical signals are multiplied by a sine coefficient and a cosine coefficient based on the phase difference of each electrical signal, and a signal multiplied by the sine coefficient and a signal multiplied by the cosine coefficient are added, respectively. Such processing is equivalent to performing discrete Fourier transform on the magnetic flux density distribution obtained from the output signal of each detection element to obtain the fundamental wave component. Therefore, the fundamental wave component can be directly extracted from the signal output from each detection element, and the accuracy of the two-phase sine wave can be improved.

[Embodiment] The configuration of a first embodiment of the position detection device of the present invention will be described below with reference to the drawings.

In FIG. 3, reference numeral 101 is a cylindrical housing made of metal, for example, aluminum, with only the lower end surface open. A donut-shaped bearing 100 made of copper-based metal is press-fitted into the center of the upper surface of the housing 101.

A metal rotating shaft 1 is inserted into the hole in the center of this bearing 100.
02 is inserted in a rotatable state.

A rotor 103 fixed at right angles to the rotating shaft 102 is provided inside the housing 101.

On the outer circumference of the rotor 103, a multi-pole magnet, which is more powerful than ferrite, in which magnetic poles of opposite polarity are alternately formed at equal pitches, is press-fitted or bonded.

Further, a circuit board 104 is fixedly disposed inside the housing 101, facing the rotor 103 and parallel to the rotor 103. At the outer end of this circuit board 104, a rotor 10 is placed on the surface facing the rotor 103.
A Hall element array 21 consisting of six Hall elements 21a to 21f is provided at a position that coincides with the center of the multipolar magnet 1 on the diametrical width thereof. Also,
Each Hall element 21 forming this Hall element array 21
a to 21f are times If! , are arranged to detect magnetic flux in a direction perpendicular to the surface of the substrate 64.

Note that the circuit board 104 is positioned by the protrusion 110 provided inside the housing 101 so that the gap between the detection surface of the Hall element array 21 and the multipolar magnet 1 on the rotor 103 is about 0.5 mm.

Here, the arrangement of the multipolar magnet l of the rotor 103 and the Hall element array 21 is shown in FIG. In Figure 1,
The Hall element array 21 is arranged so that the magnetic pole pitch l of the multipolar magnet 1, which is a moving body, is divided into six Hall elements 21a to 21f at equal intervals.

In this embodiment, the center circle of the magnet width of the multipolar magnet 1 is 22+
+++n, and the multipolar magnet 1 has a configuration of 20 magnetic poles (N pole x 20, S pole x 20).

Furthermore, while the magnetic pole pitch of the multipolar magnet 1 is approximately 3.46 mm, the six Hall elements are approximately 0.58 mm.
They are arranged in an arc shape along the center circle of the magnet width at intervals.

The lower end surface of the housing 101 is closed by a cover 105 that contacts the inside of the housing 101. The circuit board 104 is held between the cover 105 and the protrusion 110 of the housing 101. Also, cover 10
A hole is provided in the center of the cord bush 1.
07 passes through this hole, and fixes a wire harness 109 that supplies power to the circuit board 104 and outputs a detection signal via the lead wire 106.

The lower end of the rotating shaft 102 is configured to be positioned in the vertical direction by a thrust bearing (not shown) provided at the center of the circuit board 1.4.

Further, the cover 105 is fixed to the housing 101 by four screws 108 provided around the circumference of the housing 101.

Next, the configuration of the detection circuit formed on the circuit board 104 will be explained according to FIG. 2.

In FIG. 2, 320 is a constant voltage power supply, which is supplied with power from the outside via the wire harness 109 described above. The Hall elements 21a to 21f receive power from a constant voltage power supply 320, and their output terminals are connected to differential amplifiers 301 to 306, respectively.

An adder 307 is provided on the output side of the differential amplifiers 301 to 306.
, 308, 310, 311 are provided, and resistors Ll to R
S6+ Rc, ~Rc6. A weighted addition circuit is formed by Rs.

Here, these resistors Rs l”” Rs 6+ R
c + ~Rc b are each represented by RSn + RCn,
And the magnetic column pinoch l of the multipolar magnet 1 is set to one period (0 to 360d
eg), the position of each Hall element 21a to 21f is set at an angle (0°60.180, 240, 300deg-θn
), each resistance RsI-R, 6, Rc1 to Rc6
The resistance value of Rs n = Rs / S I n θn-(+
) Rcn=Rs/cos θn...Set to the value shown in (2). In other words, the value of resistance RS is lOkΩ
Then, the values of the resistors Rsr to Rsbr Rc+ to Rc6 are set as shown in Table 1.

(Left below) Table 1 Based on formulas (1) and (2), each resistor Rs+””RS6
1 Rcl"" When calculating the resistance value of RC6, si
When n θn or cos θn has a (-) sign,
Each adder 3o8. and 311, (+)
The codes are connected to adders 307 and 310, respectively.

In addition, the resistance RSI + R is the result of calculating the resistance value.
, , 4 are not added. (For example, stop the connection itself, or connect a resistor with a very large resistance value, etc.)

) and each resistor Rs + ~Rs 6+ Rc + ~R
The weighted L-J is performed by the resistance value of cb, and the added signals added by each sign by each adder 307, 308, 310, 311 are sent to differential amplifiers 309, 31.
2, the one-symbol addition signal is subtracted from the ten-symbol addition signal. The result of this subtraction is
1. It is output from T 2 via the Riet wire 1.06 and the wire harness 109.

The operation of the first embodiment configured as above will be explained with reference to each figure.

When a constant voltage power supply is supplied from the outside via the wire harness 109 and the rotor 103 rotates together with the rotating shaft 102, six phases are generated from each Hall element 21a to 21f, dividing the space between the magnetic pole pinches 1 into six equal parts, as shown in FIG. Wave signal SHI~S
H6 is output.

Here, when the distance between the rotor 103 and each Hall element 21a to 21f is sufficiently far, the waveform of the signals SHI to S1-16 output from each Hall element 21a to 21f is a waveform close to a sine wave, or a waveform close to a sine wave. This results in a polyphase sine waveform with a phase shift of 60 degrees. And, each of these Hall elements 2] a to 21
Output signals SH1 to SH6 from f are amplified by differential amplifiers 301 to 306, respectively, and then connected to resistors Rs+
~R-6. Rc~Rc5. Rs and differential amplifier 307,3
The weighting configured by 08, 310, and 311 is performed by the addition circuit and the subtraction circuit by the differential amplifiers 309 and 312 as shown in equations (3) and (4).

K・Σ SHn・R5,... (3) K・Σ
5lln・R... (4) However, K is a constant, that is, in equations (3) and (4), each Hall element 21
The sine and cosine coefficients R9I'l+RCn corresponding to the arranged positions of a to 21f, that is, the phase difference of each output signal SHI to SH6, are applied to each Hall element 21a to 21r.
The output signals SHI to SH6 are multiplied and added.

By the way, the above equations (3) and (4) can be transformed as shown in ■. That is, (3), (
The calculation in equation 4) calculates the magnetic flux density distribution obtained from the output signals of each Hall element 21a to 21f by changing the magnetic pole pitch l.
This is equivalent to performing a discrete Fourier transform with a period of , and obtaining the fundamental wave component. In this way, by multiplying the output signals SHI to SH6 of each of the Hall elements 21a to 2]f by the sine and cosine coefficients R3I'l+PCll based on the phase difference of the respective output signals SH1 to SH6 and adding them, each hall Since the fundamental wave components of the signals SHI to SH6 output from the elements 21a to 21f can be extracted, for example, the rotor 103 and each Hall element 21a to 2
Even if waveform distortion occurs due to a change in the distance from φ1.1f, the accurate two-phase sine wave φ1.1 as shown in FIG. φ2 can be output.

Therefore, this two-phase sine wave φ1. Highly accurate interpolation is possible from φ2. Incidentally, in this embodiment, the rotor 103
By interpolating between the magnetic pole pitches of 1 with 212 (4 (196)), a resolution of 4/1000 degrees could be obtained.

Further, this embodiment has the effect of reducing the influence of variations in unbalanced voltages, etc. of each Hall element 21a to 21f.

That is, for example, the Hall elements 21b and 21e in FIG.
Assuming that the same degree of unbalanced voltage is generated in the Hall elements 21b and 21e, the sine and cosine coefficients RSr1. RC11 has the same value, and only the sign is reversed.

Therefore, those Hall elements 2 are connected to the output terminals T, , T2.
1b, 2]e unbalanced voltage component does not appear.

In other words, if the number of Hall elements is about 20 or more and the unbalanced voltage of each Hall element is normally distributed or randomly distributed around O, then the unbalanced voltage component of each Hall element is It is possible to almost eliminate the influence of

In the first embodiment, a multipolar magnet 1 in which magnetic poles of opposite polarity are alternately formed at a predetermined magnetic pole pitch l is used as a moving body, but in addition to this, for example, a ferromagnetic gear known as a reluctance type may be used. and a permanent magnet for bias may be used. In addition to the Hall element, the detection element may be a ferromagnetic thin film resistance element, a magnetoresistive element, or the like. Furthermore, the moving body is not limited to a rotating body such as the rotor 103, but can also be configured as a known linear encoder that is linearly displaced.

Further, in the first embodiment described above, each Hall element 21a to 21
Although the example in which f is arranged at equal intervals has been described, some positional errors may occur during actual manufacturing. In such a case, while continuously rotating the rotor 103, the signals SHI~ outputted from each Hall element 21a~21f.
What is necessary is to measure the phase of SH6 and appropriately change the sine and cosine coefficients R3ゎ1Rcn based on this phase difference.

That is, in this embodiment, there is no restriction on the position where the Hall elements are arranged, and the sine and cosine coefficients RSn+Rcn are determined based on the positional difference of the electric signal corresponding to the magnetic field detected at the position where each Hall element is arranged. All you have to do is determine.

Next, the structure and operation of a second embodiment of the position detection device of the present invention will be explained with reference to FIG. Incidentally, since the difference between the first embodiment described above and this embodiment is only in the method of arranging the Hall elements, this point will be explained below.

In FIGS. 6(a), (b), and (C), for the magnetic pole bit i of the multipolar magnet 1, Hall elements 71a to 71d,
The element size of 72a to 72f, 73a to 73f or the mounting area on a substrate etc. is relatively large, and all the necessary Hall elements 71a to 71d are included within the magnetic pole pitch l of the multipolar magnet 1.
, 72a to 72f, and 73a to 73f cannot be arranged.

That is, in FIG. 6(a), the Hall elements 71a to 71d are arranged such that the element arrangement pitch ls is poor +- (n: number of elements) with respect to the magnetic pole pitch l. In this case, as in the first embodiment described above, multiphase signals corresponding to the number of Hall elements can be obtained from each Hall element 71a to 71d. Therefore, by inputting the output signals of each Hall element 71a to 71d to a detection circuit similar to that of the first embodiment described above, an accurate two-phase sine wave corresponding to the magnetic pole pitch l of the multipolar magnet 1 is generated. can be detected.

After all, it is sufficient that the phases of the detection signals obtained from a large number of Hall elements are separated by 360°/number of elements.
It is possible to arrange two Hall elements in one set at equal intervals as shown in FIG. 6(2), or to arrange three Hall elements in one set at equal intervals as shown in FIG. 6(C).

In addition, in the example of FIG. 6(C), the Hall elements 73a to 73
The phase order of the signals output from f and the order of element arrangement are different.

Next, a third embodiment of the present invention will be described with reference to FIGS. 7 and 8.

In this embodiment, after the output signals of the Hall elements 8a to 8f are amplified by differential amplifiers 801 to 806, the amplified signals are selectively sent to an analog-to-digital (A/D) converter 808 by a multiplexer (MPX) 807. The input signal is converted into a digital signal, and a central processing unit (CPU) 809 performs a predetermined calculation on the output signal of each Hall element 8a to 8f converted into the digital signal.

The calculation contents of this CPU 809 are shown in Fig. 8 (a) and (b).
This is shown in the flowchart below.

In FIGS. 8(a) and 8(b), after the initialization process is performed in step 910, the MPX8
07 is performed, and the signal to be subjected to A/D conversion is selected. In step 930, the A/D converter 808
A command is issued to start the A/D conversion process, and it is determined in step 940 whether the A/D conversion process has ended. and,
When the A/D conversion processing is completed, the process advances to step 950 and the A/D converted signal is temporarily stored in the RAM of the CPU 809. At step 960, each Hall element 8a-8
All signals output from f are A/D converted, and it is determined whether the signals have been input manually to the CPU 809. As a result of this determination, if all the signals have not yet been input to the CPU 809, the process returns to step 920, and on the other hand, if all the signals have been input, the process proceeds to step 970. In step 970, the following calculation is performed based on the manually input data Di, where i: data number (element number), n: total number of elements (8). After similar weighting is performed, in step 980,
The sign determination of the calculation results V, , V2 is executed.

That is, when the signs of the calculation results V, , V2 are both tens signs, when they are both one sign, (1) when 1 is a 1-sign and V2 is one sign, and () when 1 is one sign and V2 is a tens sign. Determine which of the four cases applies. In step 990, the absolute values of the calculation results V, , V2 are calculated. Then, in step 1000, the calculation results V, , V2 determined in step 980
Step 1 is to calculate the angle based on the sign of
Selected from 010-1040. In this example, the magnetic pole pitch l of the multipolar magnet 1 is set for one cycle (0 to 3
60°), the position of the magnetic pole is expressed in terms of angle. In order to calculate the angle corresponding to this position in the range of 0 to 360 degrees, the angle is divided into four cases depending on the sign of the calculation result V, V2, and the angle calculation is executed in steps 1010 to 1040. be done.

As described below, in this embodiment, by converting the output signals of each Hall element 8a to 8f into decile signals, the CPU
809, it is possible to directly obtain the angle corresponding to the position of the magnetic pole, and various signal processing to remove noise and the like is possible. However, on the other hand, since calculation processing and the like require time, a certain amount of response time is required for position detection.

〔Effect of the invention〕

As explained above, the present invention includes a plurality of detection elements that detect the magnetic field of a multipolar magnet and converts it into an electrical signal, and also extracts the fundamental wave component directly from the electrical signal output from each detection element. 2, which has definitely improved accuracy.
A phase sine wave can be obtained. Therefore, by performing known interpolation calculations using this highly accurate two-phase sine wave, the accuracy of position detection of the moving body can also be improved.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the arrangement of the Hall element with respect to the multipolar magnet in the first embodiment of the present invention, FIG. 2 is a circuit diagram showing the configuration of the detection circuit of the first embodiment, and FIG. A configuration diagram showing the overall configuration of the first embodiment, FIG. 4 is a waveform diagram showing signal waveforms output from each Hall element, and FIG. 5 is a two-phase sine wave output from the detection circuit in FIG. 2. A waveform diagram showing FIG. 6(a). (b) and (C) are explanatory diagrams showing the arrangement of the Hall elements with respect to the multipolar magnet in the second embodiment of the present invention, and FIG. 7 is a circuit diagram showing the detection circuit of the third embodiment of the present invention. 8(a) and 8(b) are flowcharts 1 to 8 showing the control procedure 2 executed by the CPU of FIG. 1... Multipolar magnet, 21... Hall element array, 21
a to 21f... Hall element, 301 to 312... Differential amplifier, 320... Constant voltage power supply.

Claims (2)

[Claims] (1) In a position detection method that detects the position of a moving object using two sine wave signals having a phase difference of 90 degrees, a plurality of signals that are periodically output every time the moving object moves a predetermined distance. On the other hand, by multiplying these plurality of signals by a sine coefficient and a cosine coefficient based on the phase difference, and then adding the plurality of signals multiplied by the sine coefficient and the plurality of signals multiplied by the cosine coefficient, the 90 A position detection method characterized by generating two sinusoidal signals having a phase difference of degrees. (2) It has a moving body and a fixed body, and generates two sine wave signals having a phase difference of 90 degrees depending on the position of the moving body, and uses these sine wave signals to determine the position of the moving body. a multipolar magnet disposed on either the movable body or the fixed body and having a plurality of magnetic poles magnetized with opposite polarities at predetermined intervals; a plurality of detection elements that are arranged on either the moving body or the fixed body to face the polar magnets and detect the magnetic field generated by the multipolar magnet and convert it into an electric signal; and a plurality of detection elements that are output from the plurality of detection elements For electrical signals,
Calculating means for calculating two sine wave signals having a phase difference of 90 degrees by multiplying the sine coefficient and cosine coefficient based on the phase difference of these electric signals and adding these, respectively. position detection device.