JP3075452B2 - 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 Prior Art As shown in FIG.
The two sine signals are amplified by the amplifier 2 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 2 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 two digitized sine signals having a phase difference of 90 ° into a tan ^-1 table stored in the ROM to obtain a fine displacement, and adds the coarse position information to the fine displacement to obtain a position. The information is derived, displayed on the display unit 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, in the above-described conventional position measuring device, there is 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
When the sine signals different from each other by 0 ° are A and B, if the phase error between these two signals is α, A = COS θ and B = SIN
(Θ + α), these two sine signals are converted to an A / D converter 19 to obtain a position represented by the angle θ.
When the angle θ, that is, the position is obtained from the tan ^-1 table, a position error occurs due to the above α. If α is constant, processing conversion can be performed as a correction constant, but this operation is impossible because it is not constant.

[0005] The present invention has been made in view of such a situation, and a position measurement method capable of obtaining highly accurate displacement, that is, position information without being affected by the accuracy of a signal output from a detector. It is intended to provide a device.

[0006]

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 in accordance with a change in position to measure a position. A measuring device, comprising:
Adding and subtracting means (for example, the adding and subtracting circuit 5 in FIG. 1) for generating a third sine signal by subtracting the sine signal of FIG. 1 and generating a fourth sine signal by adding the first and second sine signals.
Maximum and minimum measuring means (for example, the maximum and minimum measuring circuit 6 in FIG. 1) for measuring the maximum and minimum values of the third and fourth sine signals, respectively, and the maximum value measured by the maximum and minimum measuring means Processing means for correcting the ratio of the third and fourth sine signals based on the ratio of the amplitudes of the third and fourth sine signals obtained based on the minimum value and the position thereof from the obtained correction value (for example, , The processing circuit 7) of FIG.

[0007]

In the position measuring device of the present invention, the third sine signal is generated by subtracting the second sine signal from the first sine signal, and the first and second sine signals are added to produce the fourth sine signal.
Are generated, the maximum and minimum values of the third and fourth sine signals are measured, and the third and fourth sine signals are determined based on the measured maximum and minimum values.
The ratio of the third and fourth sine signals is corrected based on the ratio of the amplitudes of the sine signals, and the position is obtained from the obtained correction value. There is no phase difference between the third sine signal and the fourth sine signal, and the phase difference existing between the first sine signal and the second sine signal is based on the amplitude of the third sine signal and the fourth sine signal. It is all absorbed by the amplitude. Therefore, the position information can be obtained with high accuracy by determining the ratio between the third and fourth sine signals and correcting the ratio based on the ratio between the amplitudes of the third and fourth sine signals.

[0008]

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 addition / subtraction circuit 5 adds the first and second sine signals having a phase difference of 90 ° obtained from the detector 1 according to the position change and amplified by the amplifier 2 to generate a fourth sine signal. The third sine signal is generated by subtracting the second sine signal from the one sine signal. The maximum / minimum measurement circuit 6 measures the maximum value and the minimum value of each of the third and fourth sine signals. The processing circuit 7 calculates the ratio between the third and fourth sine signals based on the ratio between the amplitudes of the third and fourth sine signals determined based on the maximum and minimum values measured by the maximum and minimum measurement circuit 6. The correction is performed, a fine displacement is obtained from the obtained correction value, coarse position information from the counter circuit 4 is added to the fine displacement to derive position information, and this is displayed on the display 8 and displayed on the external output unit 9. Output to

Next, the operation of the embodiment of FIG. 1 will be specifically described. The first and second sine signals output from the detector 1 are A = COS θ and B = SIN (θ + α), respectively.
Then, in the addition / subtraction circuit 5, the third sine signal HA = A−
B, create the fourth sine signal HB = A + B. The third sine signal HA and the fourth sine signal HB are represented by the following (Equation 1) and (Equation 2).

[0010]

(Equation 1)

[0011]

(Equation 2)

Here,

(Equation 3)

[0013]

(Equation 4)

[0014]

(Equation 5) It is.

Accordingly, the third sine signal HA and the fourth sine signal HB can be expressed as the following (Equation 6) and (Equation 7).

[0016]

(Equation 6)

[0017]

(Equation 7)

However,

(Equation 8)

[0019]

(Equation 9)

[0020]

(Equation 10)

As is apparent from (Equation 6) and (Equation 7), the third sine signal HA and the fourth sine signal HB obtained from the addition / subtraction circuit 5 have the amplitude difference, but have the first sine signal A and the fourth sine signal HB. These are two signals from which the phase error α of the two sine signals has been eliminated.

Next, the third sine signal HA and the fourth sine signal HB obtained from the addition / subtraction circuit 5 are supplied to a maximum / minimum measurement circuit 6. This maximum / minimum measurement circuit 6 is, for example,
As shown in FIG. 2, the multiplexer 11, A /
It comprises a D converter 12, a comparison circuit 13, and a storage unit 14.

The multiplexer 11 outputs the third sine signal HA
And the fourth sine signal HB alternately with the A / D converter 12
To supply. The A / D converter 12 outputs the third input signal.
The sine signal HA and the fourth sine signal HB are digitized. The comparison circuit 13 sequentially compares the maximum value and the minimum value stored in the storage unit 14 and the digitized values of the third sine signal HA and the fourth sine signal HB, and outputs the third sine signal HA and the fourth sine signal HB. When the value of the sine signal HB is larger than the maximum value, it is stored in the storage unit 14 as a new maximum value, and when the values of the third sine signal HA and the fourth sine signal HB are smaller than the minimum values, they are set as new minimum values. The information is stored in the storage unit 14.

The third sine signal HA and the fourth sine signal HB
Are performed until the first sine signal A and the second sine signal B are input for at least one cycle or more. The period change of the first and second sine signals A and B can be obtained from the counter circuit 4.

The third sine signal H obtained by the above operation
The maximum value and the minimum value of A and the maximum value and the minimum value of the fourth sine signal HB are defined as HA _MAX , HA _MIN , HB _MAX , and HB _MIN.
Then, 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 sets of HA _MAX , HA _MIN , HB _MAX , and HB _MIN . This operation 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 HA _MAX , HA _MIN , HB _MAX , and HB _MIN stored in the storage unit 14 when necessary, and converts the amplitudes La and Lb in (Equation 6) and (Equation 7). It is determined by the following (Equation 11) and (Equation 12).

La = (HA _MAX −HA _MIN ) / 2 (Equation 11)

Lb = (HB _MAX −HB _MIN ) / 2 (Equation 12)

The processing circuit 7 includes a plurality of sets of HAs.
_{Using MAX} , HA _MIN , HB _MAX , and HB _MIN , average the amplitudes La and Lb. Using the amplitudes La and Lb obtained in this manner, HA and H in (Equation 6) and (Equation 7) are used.
Removing the amplitude term from B gives

HA ′ = COS (ψ) (Expression 13)

HB ′ = SIN (ψ) (Equation 14), and ψ is obtained from a simple tan ⁻¹ table.

The maximum / minimum measuring circuit 6 outputs the third sine signal HA supplied from the adding / subtracting circuit 5 when the detector 1 is stopped.
After the A / D converter 12 digitizes the fourth sine signal HB and the fourth sine signal HB, the digital signal is sent to the processing circuit 7 without being supplied to the comparison circuit 13.

The processing circuit 7 finally obtains the following (Equation 15)
Is calculated, and θ corresponding to the position is calculated.

Θ = tan ⁻¹ (HB ′ / HA ′) − φB = tan ⁻¹ {(HB / HA) × F (α)} − tan ⁻¹ {1 / F (α)} (formula 15)

Here, F (α) = La / Lb (Equation 16).

As described above, even if the phase error α exists between the original first sine signal A and the second sine signal B, and this phase error shows a change, the position is independent of the amount of the change. Can be calculated. The processing circuit 7 adds the coarse position information obtained from the counter circuit 4 and the fine displacement, that is, the fine position information obtained from (Equation 15), to obtain a final position, and displays the final result on the display unit 8. Then, the data is output to the external output unit 9.

It should be noted that the processing circuit 7 of the above-described embodiment
It can be implemented by a combination of U, a ROM that defines a program that defines the operation of the CPU, and a RAM that is a work area of the CPU, 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.

[0039]

As is apparent from the above description, according to the position measuring apparatus of the present invention, the first and second sine signals whose phases are different from each other by 90.degree. A third sine signal is generated by subtracting the second sine signal from the first sine signal, and a fourth sine signal is generated by adding the first and second sine signals. Are measured, and the third and fourth sine signals are determined based on the ratio of the amplitudes of the third and fourth sine signals determined based on the measured maximum and minimum values. Is corrected and the position is obtained from the obtained correction value. Therefore, even when the signal state obtained from the detector is bad, or when the signal fluctuates due to a temperature change, etc. Increase location information without being affected by signal condition It is possible to obtain every time.

[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 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 11 Multiplexer 12 A / D converter 13 Comparison circuit 14 Storage part

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-96131 (JP, A) JP-A-4-96130 (JP, A) JP-A-5-231879 (JP, A) JP-A-5-231879 26686 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G01D 5/00-5/62

Claims (1)

(57) [Claims] 1. A position measuring device for processing a first and a second sine signal having a phase difference of 90 ° obtained from a detector according to a position change and measuring a position, wherein: Adding / subtracting means for subtracting the second sine signal to generate a third sine signal, and adding the first and second sine signals to generate a fourth sine signal; Maximum and minimum measuring means for measuring respective maximum and minimum values of the sine signal; and the amplitudes of the third and fourth sine signals obtained based on the maximum and minimum values measured by the maximum and minimum measuring means. Processing means for correcting the ratio of the third and fourth sine signals based on the ratio and obtaining a position from the obtained correction value.