JP3208932B2 - Position measuring device - Google Patents

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 which obtains position information by processing two sine signals having a phase difference of 90.degree. Obtained from a detector in accordance with a position change.

[0002]

2. Description of the Related Art As shown in FIG.
The two sine signals are amplified by the amplifier 3 and the waveform shaper 3
The coarse position information is obtained by counting the number of the square wave signals by the counter circuit 4 and supplied to the processing circuit 20 while the phase amplified by the amplifier 3 is different by 90 °. The two sine signals are applied to the A / D converter 19, digitized, and supplied to the processing circuit 20. The processing circuit 20 inputs the two digitized sine signals having a phase difference of 90 ° into the 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 JP-A-56-96213.

[0003]

However, the conventional position measuring apparatus described above has a problem that the accuracy of the measurement is deteriorated due to the fluctuation of the accuracy of the input sine signal.

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

A = a × COSθ + C1 (Equation 1)

B = b × SIN (θ + α) + C2 (Equation 2)

The above equations (1) and (2) are used. In order to determine the position represented by the angle θ, the first
And the second sine signals 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 can be performed as a correction constant.
This operation is not possible because it is not constant.

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

[0009]

SUMMARY OF THE INVENTION A position measuring apparatus according to the present invention processes first and second sine signals having a phase difference of 90.degree. Obtained from a detector according to a position change to obtain position information. A measuring device, wherein first and minimum measuring means (for example, a maximum and minimum measuring circuit 6 in FIG. 1) for measuring respective maximum and minimum values of the first and second sine signals;
First processing means for obtaining 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 and minimum measurement means (for example, the processing of FIG. 1) Based on the amplitude and the offset determined by the circuit 7) and the first processing means.
And a correcting means for normalizing the second sine signal and generating the third and fourth sine signals (for example, the correction circuit 1 in FIG. 1).
0), an addition / subtraction means for subtracting the fourth sine signal from the third sine signal to generate a fifth sine signal, and adding the third and fourth sine signals to generate a sixth sine signal. (For example, the addition and subtraction circuit 5 in FIG. 1), and second maximum and minimum measurement means (for example, the maximum and minimum measurement circuit 6 in FIG. 1) for measuring the maximum and minimum values of the fifth and sixth sine signals, respectively. , The fifth measured by the second maximum-minimum measuring means.
Based on the ratio of the amplitudes of the fifth and sixth sine signals obtained using the maximum value and the minimum value of the sixth sine signal.
And a second processing means (for example, the processing circuit 7 in FIG. 1) for correcting the ratio of the sixth sine signal and obtaining position information from the obtained correction value.

[0010]

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

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

[0012]

FIG. 1 shows the configuration of an embodiment of the position measuring apparatus according to the present invention. 1, a detector 1, an amplifier 2, a waveform shaper 3 and a counter circuit 4 are the same as those in the conventional example of FIG.

The first sine signal A shown by the above (Equation 1) and the second sine signal B shown by the above (Equation 2) output from the detector 1 are supplied to a maximum / minimum measurement circuit 6.
The maximum / minimum measurement circuit 6 includes, for example, a multiplexer 11 and an A / D converter 1 as shown in FIG.
2. It comprises 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 a multiplexer 11 and digitized by an 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, a new The maximum value is stored in the storage unit 14, and when the signal value is smaller than the minimum value, the storage unit 1
4 is stored.

The above operation of 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. The period 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 that 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 stores a plurality of maximum values and minimum values. Remember. The operation for 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 obtains the following (Equation 3),
Based on (Equation 4), (Equation 5) and (Equation 6), the amplitudes a and b and the offsets C1 and C2 of the first and second sine signals A and 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)

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

The processing circuit 7 converts the values of the amplitudes a and b and the offsets C1 and C2 obtained in this manner into a correction circuit 10
Send to The correction circuit 10 includes, for example, a reference potential change circuit 15 that changes the reference potential of the amplifier 2 and an amplification degree change circuit 16 that changes the amplification degree of the amplifier 2, as shown in FIG. Input amplitudes a and b
The reference potential and the amplification 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
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 are respectively obtained by (Equation 7) and (Equation 8). Obtain the indicated third and fourth sine signals A ', B'.

A ′ = COS θ (Expression 7)

B ′ = SIN (θ + α) (Expression 8)

The third and fourth sine signals A ′ and B ′ are supplied to an addition / subtraction circuit 5. The addition / subtraction 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 generate a fifth sine signal HA ′. 6 is generated.
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) It is.

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

[0031]

(Equation 6)

[0032]

(Equation 7)

However,

(Equation 8)

[0034]

(Equation 9)

[0035]

(Equation 10) It is.

As is apparent from (Equation 14) to (Equation 18), the fifth and sixth sine signals HA and HB have a difference in amplitude but have a phase error from which the phase error has been eliminated.

Next, the fifth and sixth sine signals HA and HB are supplied to a maximum / minimum measuring circuit 6, and similarly to the first and second sine signals A and B, respectively, the maximum and minimum values thereof are set. 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 obtaining the amplitudes La and Lb, the processing circuit 7 calculates an average using a plurality of maximum values and minimum values. Using the amplitudes La and Lb thus obtained, (Equation 1)
By removing the amplitude term from 4) and (Equation 15), the following (Equation 21) and (Equation 22) are obtained, and a simple ta
ψ is obtained from the n ^-1 table.

HA ′ = COS (ψ) (Equation 21)

HB ′ = SIN (ψ) (Equation 22)

Here, the maximum / minimum measuring circuit 6 includes the detector 1
When the fifth and sixth sine signals HA and HB are A / D
After passing through the converter 12, the signal is directly supplied to the processing circuit 7 without passing through the comparison circuit 13. The processing circuit 7 finally calculates the following (Equation 23) and obtains θ corresponding to the position.
Is calculated.

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 obtains the position information from the counter circuit 4. The final position is obtained by adding the coarse information and the fine position information. Thus, the original first and second sine signals A, B
Have different amplitudes a and b, and a phase error α between the two signals.
Is present, different offsets C1 and C2 are present in both signals, and even if these amounts show fluctuation, the position can be calculated regardless of the fluctuation amount. The processing circuit 7
The calculated result is displayed on the display unit 8, converted into a numerical value corresponding to the calculated result, and output to the external output unit 9.

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

Since such a position measuring device can measure a 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 apparatus of the present invention, the maximum value and the minimum value of the first and second sine signals are measured, and the maximum value and the minimum value of the measured first and second sine signals are calculated. Determining the amplitudes and offsets of the first and second sine signals on the basis of the first and second sine signals, normalizing the first and second sine signals based on the determined amplitudes and offsets, generating third and fourth sine signals, Subtracting the fourth sine signal from the signal to generate a fifth sine signal;
The sine signals are added to generate a sixth sine signal, the maximum and minimum values of the fifth and sixth sine signals are measured, and the maximum and minimum values of the measured fifth and sixth sine signals are measured. Is used to correct the ratio of the fifth and sixth sine signals based on the ratio of the amplitudes of the fifth and sixth sine signals, and to obtain the position information from the obtained correction value. There is no phase error between the fifth and sixth sine signals, and the phase error between the first and second sine signals, ie, the phase error between the third and fourth sine signals, is And the amplitude of the sixth sine signal, the ratio of the fifth and sixth sine signals is corrected based on the ratio of the amplitudes of the fifth and sixth sine signals. Even in the bad case, the signal fluctuated due to temperature change etc. 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 the drawings]

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

FIG. 2 is a block diagram showing a configuration example of a maximum / minimum measurement circuit of FIG. 1;

FIG. 3 is a block diagram illustrating a configuration example of a correction circuit 10 of FIG. 1;

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Detector 2 Amplifier 3 Waveform shaper 4 Counter circuit 5 Addition / subtraction circuit 6 Maximum / minimum measurement circuit 7 Processing circuit 10 Correction circuit 11 Multiplexer 12 A / D converter 13 Comparison circuit 14 Storage unit 15 Reference potential change circuit 16 Amplification degree change circuit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01D 5/00-5/62

Claims (1)

(57) [Claims] 1. A position measuring apparatus for processing first and second sine signals having a phase difference of 90 ° obtained from a detector according to a position change to obtain position information, wherein the first and second sine signals are provided. First maximum-minimum measuring means for measuring the maximum value and the minimum value of the first, and the first maximum measured by the first maximum-minimum measuring means
And first and second processing means for determining 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 determining the amplitude and offset based on the amplitude and offset determined by the first processing means. Correction means for normalizing the first and second sine signals to generate third and fourth sine signals; and generating a fifth sine signal by subtracting the fourth sine signal from the third sine signal. An adding / subtracting means for adding the third and fourth sine signals to generate a sixth sine signal; and a second maximum and minimum for measuring respective maximum and minimum values of the fifth and sixth sine signals. Measuring means; and the fifth measuring means measured by the second maximum and minimum measuring means.
And correcting the ratio of the fifth and sixth sine signals based on the ratio of the amplitudes of the fifth and sixth sine signals obtained by using the maximum value and the minimum value of the sixth sine signal. And a second processing unit for obtaining position information from the value.