JPH06341854A - Position measuring apparatus - Google Patents

Abstract

PURPOSE:To measure a position with high accuracy by a method where the amplitude and the offset of a first sine signal and of a second sine signal are found on the basis of the maximum value and the minimum value of the first and second sine signals. CONSTITUTION:A first sine signal A and a second sine signal B which are output from a detector 1 are supplied to a maximum and minimum measuring circuit 6, and the maximum value and the minimum value of the signals A, B are found. Then, a processing circuit 7 finds amplitudes (a), (b) and offsets C1, C2 of the signals A, B, and it sends them to a correction circuit 10. The circuit 10 corrects them, it then normalizes the signals A, B, it obtains a third sine signal A' and a fourth sine signal B', and it supplies them to an addition and subtraction circuit 5. The circuit 5 generates a fifth sine signal HA and a sixth sine signal HB, and it supplies them to the circuit 6, and their maximum value and their minimum value are found. In addition, the circuit 7 finds amplitudes La, Lb of the signals HA, HB, and the circuit 6 supplies the signals HA, HB directly to the circuit 7. The circuit 7 finally performs a prescribed computation, and it computes a theta corresponding to a position.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position measuring apparatus for processing two sinusoidal signals having phases different by 90.degree.

[0002]

2. Description of the Related Art A conventional device of this type, as shown in FIG.
The two sine signals are amplified by the amplifier 3, and the waveform shaper 3
Is converted into a rectangular wave signal by the counter circuit 4 and the number of rectangular wave signals is counted by the counter circuit 4 to obtain rough position information and supply it to the processing circuit 20, while the phase amplified by the amplifier 3 differs by 90 °. Two sine signals are applied to the A / D converter 19, digitized respectively, and then supplied to the processing circuit 20. The processing circuit 20 inputs two digitized sine signals having 90 ° different phases to a tan ^-1 table stored in the ROM to obtain fine position information, and adds the coarse position information to the fine position information. Then, the position information is derived, displayed on the display 21, and output to the external output unit 22. The details of the conventional position measuring device shown in FIG. 3 are disclosed in Japanese Patent Laid-Open No. 56-96213.

[0003]

However, the above-mentioned conventional position measuring device has a problem that the measuring accuracy is deteriorated due to the fluctuation of the accuracy of the input sine signal.

That is, the phase of 9 obtained from the detector 1
The first and second sinusoidal signals A and B differing by 0 ° have the amplitudes of these two signals a and b, respectively, and the phase error α,

A = a × COSθ + C1 (Equation 1)

B = b × SIN (θ + α) + C2 (Equation 2)

As shown in the above (Equation 1) and (Equation 2), in order to obtain the position represented by the angle θ, the first
And the second sine signal A and B to the A / D converter 19
When the angle θ is converted into a position from the tan ⁻¹ table of the processing circuit 20, a position error occurs due to the difference between the amplitudes a and b, the phase error α, and the difference between the offsets C1 and C2. If a, b, α, C1, and C2 are constant, processing conversion is possible as a correction constant,
This operation is impossible because it is not constant.

The present invention has been made in view of such a situation, and provides a position measuring device capable of measuring a position with high accuracy without being affected by the accuracy of the two sine signals output from the detector. The purpose is to do.

[0009]

A position measuring device of the present invention processes a first sine signal and a second sine signal, which are different in phase by 90 ° and are obtained from a detector according to a position change, to obtain position information. 1. A measuring device, comprising first maximum / minimum measuring means (for example, maximum / minimum measuring circuit 6 in FIG. 1) for measuring maximum and minimum values of the first and second sinusoidal signals, respectively.
First processing means for determining the amplitude and offset of the first and second sine signals based on the maximum and minimum values of the first and second sine signals measured by the first maximum / minimum measuring means (for example, the processing of FIG. 1). Circuit 7) and a first circuit based on the amplitude and offset determined by the first processing means.
And a correction means for normalizing the second sine signal to generate the third and fourth sine signals (for example, the correction circuit 1 of FIG. 1).
0) and a fourth sine signal from the third sine signal to generate a fifth sine signal, and add and subtract means for adding the third and fourth sine signals to generate a sixth sine signal. (For example, the addition / subtraction circuit 5 in FIG. 1), and second maximum / minimum measuring means (for example, maximum / minimum measurement circuit 6 in FIG. 1) for measuring the maximum and minimum values of the fifth and sixth sine signals, respectively. A fifth measured by the second maximum-minimum measuring means
And a fifth based on the ratio of the amplitudes of the fifth and sixth sine signals determined using the maximum and minimum values of the sixth sine signal.
And second processing means (for example, the processing circuit 7 in FIG. 1) that corrects the ratio of the sixth sine signal and obtains position information from the obtained correction value.

[0010]

In the position measuring device of the present invention, the maximum and minimum values of the first and second sine signals are measured, and based on the measured maximum and minimum values of the first and second sine signals. Amplitudes and offsets of the first and second sine signals are obtained, and the first and second sine signals are normalized based on the obtained amplitudes and offsets to obtain a third signal.
And a fourth sine signal is generated, the fourth sine signal is subtracted from the third sine signal to generate a fifth sine signal, and the third and fourth sine signals are added to generate a sixth sine signal. A maximum and minimum value of each of the generated fifth and sixth sinusoidal signals is measured and a fifth value determined using the measured maximum and minimum values of the fifth and sixth sinusoidal signals.
And the ratio of the fifth and sixth sine signals is corrected based on the ratio of the amplitudes of the sixth sine signal, and the position information is obtained from the obtained correction value.

There is no phase error between the fifth and sixth sine signals, and there is a phase error between the first sine signal and the second sine signal, that is, a phase error between the third sine signal and the fourth sine signal. Is absorbed by the amplitudes of the fifth and sixth sinusoidal signals, but the ratio of the fifth and sixth sinusoidal signals is corrected based on the ratio of the amplitudes of the fifth and sixth sinusoidal signals. Can be measured.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the configuration of an embodiment of the position measuring device of the present invention. In FIG. 1, the detector 1, the amplifier 2, the waveform shaper 3, and the counter circuit 4 are the same as in the conventional example of FIG.

The first sine signal A represented by the above (formula 1) and the second sine signal B represented by the above (formula 2) output from the detector 1 are supplied to the maximum / minimum measurement circuit 6.
The maximum / minimum measurement circuit 6 is provided with a multiplexer 11 and an A / D converter 1 as shown in FIG.
2. Comprised of a comparison circuit 13 and a storage unit 14.

The first sine signal A and the second sine signal B are
The signals are alternately input via the multiplexer 11 and digitized by the A / D converter 12. Comparison circuit 13
Sequentially compares the digitized signal values of the first and second sine signals A and B with the maximum value and the minimum value stored in the storage unit 14, and when the signal value is larger than the maximum value, the Is stored in the storage unit 14 as a maximum value, and when the signal value is smaller than the minimum value, the storage unit 1 stores a new minimum value.
Store in 4.

The above operation for obtaining the maximum and minimum values of the first and second sine signals A and B is performed until the first and second sine signals A and B are input for at least one cycle or more. The cycle change of the first and second sine signals A and B can be obtained from the counter circuit 4. The maximum and minimum values obtained in this way are
Assuming A _MAX , A _MIN , B _MAX , and B _MIN , respectively, the storage unit 14 changes the storage location of these values in accordance with the information obtained from the counter circuit 4, and sets a plurality of maximum and minimum values. Remember. The operation of obtaining the maximum value and the minimum value is not performed when the movement of the detector 1 is stopped, that is, when there is no signal change.

Next, the processing circuit 7 calls the maximum value and the minimum value stored in the storage unit 14, and the following (Equation 3),
Based on (Equation 4), (Equation 5) and (Equation 6), the amplitudes a, b and the offsets C1, C2 of the first and second sine signals A, B are obtained.

A = (A _MAX −A _MIN ) / 2 (Equation 3)

B = (B _MAX −B _MIN ) / 2 (Equation 4)

C1 = (A _MAX + A _MIN ) / 2 (Equation 5)

C2 = (B _MAX + B _MIN ) / 2 (Equation 6)

The processing circuit 7 corrects the values of the amplitudes a and b and the offsets C1 and C2 thus obtained in the correction circuit 10.
Send to. The correction circuit 10 includes, for example, as shown in FIG. 3, a reference potential changing circuit 15 that changes the reference potential of the amplifier 2 and an amplification degree changing circuit 16 that changes the amplification degree of the amplifier 2. Input amplitude a, b
The reference potential and the amplification degree of the amplifier 2 are changed according to the values of the offsets C1 and C2, and the amplitudes a and b of the first and second sine signals A and B and the offset value C are changed.
1 and C2 are corrected so that a = b and C1 = C2, and as a result, the first and second sine signals A and B are normalized, and by (Equation 7) and (Equation 8), respectively, Obtain the third and fourth sine signals A ', B'shown.

A ′ = COS θ (Equation 7)

B ′ = SIN (θ + α) (Equation 8)

The third and fourth sine signals A ′ and B ′ are supplied to the adder / subtractor circuit 5. The adder / subtractor circuit 5 subtracts the fourth sine signal B'from the third sine signal A'to generate a fifth sine signal HA, and adds the third and fourth sine signals A'and B'to add Generate a sine signal HB of 6.
The fifth and sixth sine signals HA and HB are represented by the following (Equation 9) and (Equation 10).

[0025]

[Equation 1]

[0026]

[Equation 2]

Here,

[Equation 3]

[0028]

[Equation 4]

[0029]

[Equation 5] Is.

Therefore, the fifth and sixth sine signals HA and HB can be expressed by the following (Equation 14) and (Equation 15).

[0031]

[Equation 6]

[0032]

[Equation 7]

However,

[Equation 8]

[0034]

[Equation 9]

[0035]

[Equation 10] Is.

As is clear from (Equation 14) to (Equation 18), the fifth and sixth sine signals HA and HB are signals in which the phase error is eliminated, although there is an amplitude difference.

Next, the fifth and sixth sine signals HA and HB are supplied to the maximum / minimum measuring circuit 6 and, like the above-mentioned first and second sine signals A and B, their respective maximum and minimum values. Is required. Then, the processing circuit 7
Assuming that the maximum and minimum values of the fifth and sixth sine signals HA and HB are HA _MAX , HA _MIN , HB _MAX , and HB _MIN , the fifth and sixth sine signals are calculated according to the following (Equation 19) and (Equation 20). The amplitudes La and Lb of the signals HA and HB are obtained.

La = (HA _MAX −HA _MIN ) / 2 (Equation 19)

Lb = (HB _MAX −HB _MIN ) / 2 (Equation 20)

When calculating the amplitudes La and Lb, the processing circuit 7 uses a plurality of maximum values and minimum values and averages them. Using the amplitudes La and Lb thus obtained, (Equation 1
4) and (Equation 15), the following (Equation 21) and (Equation 22) are obtained, and the simple ta
ψ can be obtained from the n ⁻¹ table.

HA ′ = COS (ψ) (Equation 21)

HB ′ = SIN (ψ) (Equation 22)

Here, the maximum / minimum measuring circuit 6 is the detector 1
The 5th and 6th sine signals HA and HB at the time of stop of A / D
After passing through the converter 12, it is directly supplied to the processing circuit 7 without passing through the comparison circuit 13. The processing circuit 7 finally performs the calculation of the following (Equation 23) to obtain θ corresponding to the position.
To calculate.

Θ = tan ⁻¹ (HB ′ / HA ′) − φB = tan ⁻¹ {(HB / HA) × F (α)} − tan ⁻¹ {1 / F (α)} (Expression 23)

Here, F (α) = La / Lb (equation 24).

The position information obtained by the calculation of (Equation 23) is fine position information within one cycle of the first and second sine signals A and B, and the processing circuit 7 is obtained from the counter circuit 4. The final position is obtained by adding the coarse information and this fine position information. Thus, the original first and second sine signals A, B
, There are different amplitudes a and b, and there is a phase error α between both signals.
Is present, different offsets C1 and C2 are present in both signals, and even if these amounts show fluctuations, the position can be calculated regardless of the fluctuations. The processing circuit 7
The calculated result is displayed on the display unit 8, converted into a numerical value suitable for it and output to the external output unit 9.

The processing circuit 7 can be realized by a combination of a CPU and a ROM that defines a program that defines its operation, but can also be realized by a hard-wired logic.

Since such a position measuring device can measure the position with high accuracy, for example, a rotary encoder is used,
It is effective for surveying instruments that measure angles with high accuracy.
Of course, the same applies to various measuring devices using a linear encoder.

[0049]

According to the position measuring device of the present invention, the maximum and minimum values of the first and second sine signals are measured, and the measured maximum and minimum values of the first and second sine signals are obtained. Based on the obtained amplitude and offset, the first and second sine signals are normalized to generate the third and fourth sine signals, and the third and fourth sine signals are generated. Subtracting the fourth sine signal from the signal to generate a fifth sine signal,
A sine signal is added to generate a sixth sine signal, maximum and minimum values of the fifth and sixth sine signals are measured, and maximum and minimum values of the measured fifth and sixth sine signals are measured. Since the ratio of the fifth and sixth sinusoidal signals is corrected based on the ratio of the amplitudes of the fifth and sixth sinusoidal signals obtained by using, the position information is obtained from the obtained correction value. There is no phase error between the fifth and sixth sine signals, and the phase error between the first sine signal and the second sine signal, that is, the phase error between the third sine signal and the fourth sine signal is And the amplitude of the sixth sinusoidal signal is absorbed, but the ratio of the fifth and sixth sinusoidal signals is corrected based on the ratio of the amplitudes of the fifth and sixth sinusoidal signals, so that the signal state obtained from the detector is Even if it is bad, the signal changes due to temperature changes. Without being to be affected by the signal state of the detector in case, you can measure the position with high accuracy.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a position measuring device of the present invention.

FIG. 2 is a block diagram showing a configuration example of the maximum / minimum measurement circuit of FIG.

FIG. 3 is a block diagram showing a configuration example of a correction circuit 10 in FIG.

FIG. 4 is a block diagram showing an example of a conventional position measuring device.

[Explanation of symbols]

 1 detector 2 amplifier 3 waveform shaper 4 counter circuit 5 adder / subtractor circuit 6 maximum / minimum measuring circuit 7 processing circuit 10 correction circuit 11 multiplexer 12 A / D converter 13 comparison circuit 14 storage unit 15 reference potential changing circuit 16 amplification degree changing circuit

Claims (1)

[Claims] 1. A position measuring device for processing position information obtained by processing first and second sine signals having phases different from each other by 90 ° obtained from a detector according to a position change, wherein the first and second sine signals are provided. First maximum / minimum measuring means for measuring respective maximum value and minimum value, and the first maximum / minimum measuring means
And first processing means for obtaining the amplitude and offset of the first and second sine signals based on the maximum value and the minimum value of the second sine signal, and the first processing means based on the amplitude and offset obtained by the first processing means. Correcting means for normalizing the first and second sine signals to generate third and fourth sine signals, and subtracting the fourth sine signal from the third sine signal to generate a fifth sine signal. Along with the addition and subtraction means for adding the third and fourth sine signals to generate a sixth sine signal, a second maximum and minimum for measuring the maximum and minimum values of the fifth and sixth sine signals, respectively. Measuring means, and the fifth measured by the second maximum / minimum measuring means
And correcting the ratio of the fifth and sixth sinusoidal signals based on the ratio of the amplitudes of the fifth and sixth sinusoidal signals determined using the maximum and minimum values of the sixth sinusoidal signal, and the resulting correction And a second processing unit that obtains position information from the value.