JP2003057073A - Interpolation error estimating method, its device, and interpolation error correcting apparatus using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an interpolation error estimating method capable of easily and correctly estimating encoder interpolation error. SOLUTION: The interpolation error estimating method for estimating interpolation error when A-phase and a B-phase sine waves outputted from an encoder are interpolated by an interpolation means is provided with both an offset detection process (s10) for obtaining each offset of the sine waves when the sine waves includes offset error and the sine waves including the error are expressed by an expression (37): A-phase sine wave = As1 sin(2πx/λ)+Vs, B-phase sine wave = Ac1 cos(2πx/λ)+Vc}, and an arithmetic process (s12) for obtaining the interpolation error E due to the offset by substituting each offset obtained in the offset detection process (s10) in an expression: (38) [interpolation error E=(λ/2π) (-Vs/As1 )cos u+(Vc/Ac1 )sin u}].

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an interpolation error estimation method and apparatus, and an interpolation error correction apparatus using the method, and more particularly to modeling of an interpolation error of an encoder.

[0002]

2. Description of the Related Art Conventionally, in order to obtain high resolution phase angle data by digitally interpolating a two-phase sinusoidal signal of an encoder for detecting position, angular velocity, angular velocity, etc., an encoder output signal A processor is used. Since there is a processing limit on the spacing of the grating formed on the scale of the encoder, in order to measure a finer spacing than the scale grating, the spatial period of the phase change of the sinusoidal signal output by the encoder is further subdivided and interpolated. There is a need.

Therefore, various interpolation circuits have been conventionally used. For example, an interpolation circuit based on digital processing is an analog / digital converter (hereinafter, referred to as “analog / digital converter” that samples a sine wave-shaped signal and a cosine wave-shaped signal, which may be 90 degrees out of phase from an encoder, at a predetermined frequency and converts the sampled signal into digital data. Phase angle data at each sampling point is obtained based on each digital data obtained by ADC).

By the way, in the interpolation of the two-phase sinusoidal signal, it is assumed that the signal is a sinusoidal signal having no error.
There are errors such as an offset, a difference in amplitude between the two phases, and an error in a phase difference that is originally 90 degrees, which causes an interpolation error. To avoid this, manual or automatic signal adjustment is performed. However, an adjustment error occurs because the signal cannot be perfectly adjusted. In order to obtain the desired interpolation accuracy, it is desired to optimize the adjustment man-hours and the accuracy of the adjustment parts, but since the relationship between the two has not always been clear, it was estimated by the following simulation by a computer. Two-phase sinusoidal signal including error A = cosx, B = sin
Calculate x. Calculate the ratio (B / A) between the two phases. The arctangent operation x '= ATAN (B / A) is calculated. The difference x′−x between the results obtained by and is taken as the interpolation error E.

[0005]

However, there are a plurality of parameters for the error of the two-phase sinusoidal signal as described above, and the interaction between them has not been clear so far. Therefore, the maximum error is estimated by trial and error in which each parameter is calculated at a plurality of levels, the error is calculated, and the maximum error is calculated from the calculated error. This method has a problem that it takes a long time for simulation and the estimated value of the error is inaccurate.
Conventionally, there is a method described in Japanese Patent Application Laid-Open No. 11-316137 as a method of encoder interpolation error correction, but there is a problem that Fourier transform is required, signal processing is complicated, and processing takes time. There is. For this reason,
Conventionally, it has been strongly desired to develop a technique capable of easily and accurately estimating an interpolation error, but conventionally, there is no suitable modeling technique for estimating the interpolation error.

Further, as described above, since there is no appropriate modeling technique for estimating the interpolation error, there is no appropriate technique that can easily and accurately correct the interpolation error. The present invention has been made in view of the above-mentioned problems of the prior art, and an object thereof is an interpolation error estimation method and apparatus capable of easily and accurately estimating an interpolation error of an encoder, and an interpolation error using the same. It is to provide a correction device.

[0007]

In order to achieve the above object, an interpolation estimation method according to the present invention is an interpolation method for interpolating A-phase and B-phase sine waves output from an encoder by an interpolation means. In the interpolation error estimation method for estimating the error, when the A-phase and B-phase sine waves input from the encoder to the interpolation means include an offset error, and the sine wave including the error can be represented by the following formula 13, It is characterized by comprising an offset detection step and a calculation step.

Here, in the offset detection step, each offset of the A-phase and B-phase sine waves input from the encoder to the interpolation means is obtained. Further, in the calculating step, the respective offsets of the A-phase and B-phase sine waves obtained in the offset detecting step are substituted into the following formula 14, and an interpolation error E due to the offset is obtained.

[0009]

## EQU13 ## A-phase sine wave = As ₁ sin (2πx / λ) + Vs B-phase sine wave = Ac ₁ cos (2πx / λ) + Vc (13)

[Equation 14] Interpolation error E = (λ / 2π) {(− Vs / As ₁ ) cosu + (Vc / Ac ₁ ) sinu} (14) where λ: period u of the sine wave: 2πx / λ x: Positions of the encoder As ₁ and Ac ₁ : Amplitudes Vs and Vc of the A-phase and B-phase sine waves respectively offsets of the A-phase and B-phase sine waves obtained in the offset detection step

The term "interpolation" used herein means that, for example, a sine-wave signal having two or more phases is output from a photoelectric type, an electromagnetic induction type, a laser interference type, or another device, and a two-phase sine-wave type signal is obtained by calculation. It means that the ratio is arctangent to improve the minimum resolution. Also, the offset referred to here is
This is the deviation of the central value of the amplitude of the general sine wave from the reference value.

In the present invention, the A-phase and B-phase sine waves input from the encoder to the interpolation means include offset and amplitude ratio errors, and the sine wave including the errors can be expressed by the following formula 15. In this case, an amplitude ratio detecting step of obtaining an amplitude ratio of the A-phase and B-phase sine waves input from the encoder to the interpolation means is provided. Then, in the calculation step, the respective offsets of the A-phase and B-phase sinusoidal waves obtained in the offset detection step and the amplitude ratio obtained in the amplitude ratio detection step are substituted into the following formula 16 to obtain the offset and the amplitude. It is preferable to find the interpolation error E by the ratio.

[0012]

[Equation 15] A-phase sine wave = As ₁ sin (2πx / λ) + Vs B-phase sine wave = Ac ₁ cos (2πx / λ) + Vc (15)

[Equation 16] Interpolation error E = (λ / 2π) {(− Vs / As ₁ ) cosu + (Vc / Ac ₁ ) sinu + (Ac ₁ / As ₁ −1) sinucosu} (16) where λ : Cycle of the sine wave u: 2πx / λ x: Encoder positions As ₁ and Ac ₁ : Amplitudes Vs and Vc of the A phase and B phase sine waves: A phase and B obtained in the offset detection step Each offset of phase sine wave Ac ₁ / As ₁ : Amplitude ratio obtained in the amplitude ratio detecting step

Further, according to the present invention, the A-phase and B-phase sine waves input from the encoder to the interpolation means include offset and phase difference errors, and the sine wave including the errors can be expressed by the following formula 17. At this time, there is provided a phase difference detecting step of obtaining a phase difference between the A-phase and B-phase sine waves input from the encoder to the interpolation means. Then, in the calculation step, the respective offsets of the A-phase and B-phase sine waves obtained in the offset detection step and the phase difference obtained in the phase difference detection step are substituted into the following formula 18, and the offset and position are calculated. It is preferable to find the interpolation error E due to the phase difference.

[0014]

## EQU17 ## A-phase sine wave = As ₁ sin (2πx / λ) + Vs B-phase sine wave = Ac ₁ cos (2πx / λ + ε) + Vc (17)

[Equation 18] Interpolation error E = (λ / 2π) {(− Vs / As ₁ ) cosu + (Vc / Ac ₁ ) sinu −εsin ² u} (18) where λ: period u of the sine wave : 2πx / λ x: Positions of the encoder As ₁ , Ac ₁ : Amplitudes Vs and Vc of the A-phase and B-phase sine waves: Offsets ε of the A-phase and B-phase sine waves obtained in the offset detection step : Phase difference obtained in the phase difference detection step

Further, in order to achieve the above-mentioned object, the interpolation error estimating apparatus according to the present invention outputs A from an encoder.
In the interpolation error estimation device for estimating the interpolation error when the phase and B-phase sine waves are interpolated by the interpolation means, the A-phase and B-phase sine waves input from the encoder to the interpolation means have an offset error. The sine wave containing the error is
When it can be represented by, it is characterized by including an offset detection unit and a calculation unit.

Here, the offset detecting means obtains each offset of the A-phase and B-phase sine waves input from the encoder to the interpolating means. Further, the calculating means substitutes the respective offsets of the A-phase and B-phase sine waves obtained by the offset detecting means into the following formula 20, and obtains an interpolation error E due to the offsets.

[0017]

## EQU19 ## A-phase sine wave = As ₁ sin (2πx / λ) + Vs B-phase sine wave = Ac ₁ cos (2πx / λ) + Vc (19)

[Equation 20] Interpolation error E = (λ / 2π) {(− Vs / As ₁ ) cosu + (Vc / Ac ₁ ) sinu} (20) where λ: period u of the sine wave: 2πx / λ x: Positions of the encoder As ₁ , Ac ₁ : Amplitudes Vs and Vc of the A-phase and B-phase sine waves respectively: Offsets of the A-phase and B-phase sine waves obtained by the offset detecting means

In the present invention, the A-phase and B-phase sine waves input from the encoder to the interpolation means include offset and amplitude ratio errors, and the sine wave including the errors can be expressed by the following equation 21. At this time, an amplitude ratio detecting means for obtaining an amplitude ratio of the A-phase and B-phase sine waves input from the encoder to the interpolation means is provided. Then, the calculating means substitutes the respective offsets of the A-phase and B-phase sine waves obtained by the offset detecting means and the amplitude ratio obtained by the amplitude ratio detecting means into the following formula 22, and the offset and the amplitude are calculated. It is preferable to find the interpolation error E by the ratio.

[0019]

[Equation 21] A-phase sine wave = As ₁ sin (2πx / λ) + Vs B-phase sine wave = Ac ₁ cos (2πx / λ) + Vc (21)

[Equation 22] Interpolation error E = (λ / 2π) {(− Vs / As ₁ ) cosu + (Vc / Ac ₁ ) sinu + (Ac ₁ / As ₁ −1) sinucosu} (22) where λ : Cycle of the sine wave u: 2πx / λ x: Positions of the encoder As ₁ , Ac ₁ : Amplitudes Vs and Vc of the A phase and B phase sine waves: A phase and B obtained by the offset detecting means Each offset Ac ₁ / As _{1 of the} phase sine wave: Amplitude ratio obtained by the amplitude ratio detecting means

Further, according to the present invention, the A-phase and B-phase sine waves input from the encoder to the interpolation means include offset and phase difference errors, and the sine wave including the errors can be expressed by the following formula 23. At this time, phase difference detecting means for obtaining the phase difference between the A-phase and B-phase sine waves input from the encoder to the interpolating means is provided. Then, the calculating means substitutes the respective offsets of the A-phase and B-phase sine waves obtained by the offset detecting means and the phase difference obtained by the phase difference detecting means into the following formula 24 to calculate the offset and the position. It is preferable to find the interpolation error E due to the phase difference.

[0021]

(23) A-phase sine wave = As ₁ sin (2πx / λ) + Vs B-phase sine wave = Ac ₁ cos (2πx / λ + ε) + Vc (23)

Interpolation error E = (λ / 2π) {(− Vs / As ₁ ) cosu + (Vc / Ac ₁ ) sinu −εsin ² u} (24) where λ: period u of the sine wave : 2πx / λ x: Positions of the encoder As ₁ , Ac ₁ : Amplitudes Vs and Vc of the A-phase and B-phase sine waves: Offsets ε of the A-phase and B-phase sine waves obtained by the offset detecting means : Phase difference obtained by the phase difference detecting means

In order to achieve the above object, the interpolation error correction device according to the present invention is characterized by including a correction data generating means and an adjusting means. Here, the correction data generation means generates correction data at each position of the encoder based on the interpolation error E obtained by the interpolation error estimation device. Further, the adjusting means corrects the output of the interpolation means with the correction data generated by the correction data generating means.

In the present invention, the correction data generating means sequentially generates the correction data for each position of the encoder, and the adjusting means uses the correction data sequentially output from the generating means, and the interpolation means. It is preferable to correct the post-interpolation data sequentially output from the.

Also, in the present invention, a look-up table memory for storing the correction data from the correction data generating means in a look-up table is provided, and the adjusting means has the correction data stored in the look-up table memory. Therefore, it is preferable to correct the data after the interpolation, which is sequentially output from the interpolation means.

Further, in the present invention, it is preferable to newly create or update the lookup table in real time. Performing in real time here means performing each time the encoder is used, for example.

Further, in the present invention, it is also preferable to newly create or update the lookup table in advance. The term "preliminary" as used herein means not only each time the encoder is used, but also at a specific time such as factory shipment or maintenance after shipment.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As a result of the inventor's extensive studies on modeling of interpolation error of an encoder, the A-phase and B-phase sine waves input from the encoder to the interpolation means are, for example, offset, amplitude ratio and When the sine wave including the error of the phase difference is represented by the following formula 25, the interpolation error of the encoder due to the offset, the amplitude ratio and the phase difference should be modeled by the approximate formula of the following formula 26. You can It was found that this makes it possible to easily and accurately estimate the interpolation error due to a single parameter such as offset, and the interpolation error due to the interaction of each parameter.
The present invention has been completed.

[0028]

## EQU25 ## A-phase sine wave = As ₁ sin (2πx / λ) + Vs B-phase sine wave = Ac ₁ cos (2πx / λ + ε) + Vc (25)

Interpolation error E = (λ / 2π) {(− Vs / As ₁ ) cosu + (Vc / Ac ₁ ) sinu + (Ac ₁ / As ₁ −1) sinucosu−εsin ² u} (26) Here, λ: cycle of the sine wave u: 2πx / λ x: positions of the encoder As ₁ , Ac ₁ : amplitudes Vs and Vc of the A-phase and B-phase sine waves: the obtained A-phase and B-phase Each offset of sine wave Ac ₁ / As ₁ : Amplitude ratio of determined A-phase and B-phase sine wave ε: Determined phase difference between A-phase and B-phase sine wave Become.

[0029]

[Table 1]

As is clear from Table 1, the interpolation error cycle differs depending on the parameter of the input signal error. For the same interpolation error period, vector sum (functions are orthogonal
sinu and cosu are taken as the square root of the sum of squares), and then a simple sum is taken between different interpolation error periods to obtain the total amount of interpolation error. By the method of estimating the interpolation error according to the present embodiment, the total size of the error can be known, and the contribution rate of each input signal error can be obtained. The relationship between the input signal and the interpolation error is shown in Table 2 below.

[0031]

[Table 2] Input error parameter Interpolation error magnitude Interpolation error due to sine wave DC offset Evs = ± (Vs / As₁) (λ / 2π) Interpolation error due to cosine wave DC offset Evc = ± (Vc / Ac₁) (λ / 2π) Interpolation error due to amplitude ratio Edr = ± ((As₁/ Ac₁) -1) (λ / 4π) Interpolation error due to phase difference Eε = ± ε (λ / 4π) Then, a more accurate estimate can be made by the above-mentioned formula 26.
However, in Equation 27 below, the total interpolation error and the input signal
The size of each parameter can be estimated.

[0032]

[Equation 27] Overall interpolation error ≤ ± {√ (Evs ² + Evc ² ) + √ (Edr ² + Eε ² )} (27) If the contribution rate of the parameter is small, the parameter is omitted. You may. Hereinafter, a preferred embodiment of the present invention will be described in detail for each parameter with reference to the drawings.

[0033]First embodiment FIG. 1 shows an interpolation error estimation device according to the first embodiment of the present invention.
Of the encoder output signal processing device
Success is shown. In this embodiment, the parameters
Assuming a DC offset as
An example of estimating the interpolation error based on Same figure
The output signal processing device shown in FIG.
The path (interpolation means) 12 and the interior characteristic of the present embodiment.
The insertion error estimation device 14 is provided. Where the encoder
10 is a sine wave for detecting the position of the encoder 10.
(A-phase sine wave) SA1 and cosine wave (B-phase sine wave) SB
1 is output.

The interpolation circuit 12 includes, for example, an analog / digital converter (not shown) and a look-up table memory (not shown).
The sine wave SA1 and the cosine wave SB1 output from are sampled at a predetermined frequency and converted into digital data by an analog / digital converter (ADC). The look-up table memory stores a look-up table (LUT) that obtains phase angle data at each sampling point based on the digital data, and interpolates the sine wave SA1 and cosine wave SB1 output from the encoder 10. Then, high-resolution phase angle data is obtained.

A feature of this embodiment is that the interpolation error estimation device 14 is provided, and the encoder 10
The sine wave SA1 and the cosine wave SB1 input from the to the interpolation circuit 12 include, for example, a DC offset error, and the sine wave SA1 and the cosine wave SB1 including the error are expressed by the following formula 28.
Then, the interpolation error estimation device 14 estimates the interpolation error due to the offset. In the present embodiment, the interpolation error estimation device 14 uses the offset detection means 16
And a calculation means 18.

From the encoder 10 to the interpolation circuit 12
Each signal line 11 for sending the sine wave SA1 and the cosine wave SB1 to the
The input side of the interpolation error estimation device 14 is connected to a and 11b via signal lines 13a and 13b. The output side of the interpolation error estimation device 14 is connected to the interpolation error correction device 20 via a signal line 15. Therefore, the offset detecting means 16 detects the maximum value and the minimum value of the sine wave SA1 and the cosine wave SB1 input from the encoder 10 to the interpolation circuit 12, and the averages thereof are respectively calculated as the sine wave SA1 and the cosine wave. The deviation of the center value of the amplitude of the wave SB1 from the reference value, that is, the sine wave DC offset and the cosine wave DC offset, is obtained.

Further, in the present embodiment, the encoder 10
From the maximum value and the minimum value of the sine wave SA1 and the cosine wave SB1 input to the interpolation circuit 12 from the sine wave SA
1 and cosine wave SB1 has twice the amplitude (2As ₁ , 2Ac ₁ ). Therefore, the interpolation error estimation device 14 determines the amplitude (A) of each of the sine wave SA1 and the cosine wave SB1 from the difference between the maximum value and the minimum value of the sine wave SA1 and the cosine wave SB1.
s ₁ , Ac ₁ ). The calculating means 18 substitutes each offset value of the sine wave SA1 and the cosine wave SB1 obtained by the offset detecting means 16 into the following formula 29 to obtain an interpolation error E due to the offset.

[0038]

Sine wave SA1 = As ₁ sin (2πx / λ) + Vs cosine wave SB1 = Ac ₁ cos (2πx / λ) + Vc (28)

[Equation 29] Interpolation error E = (λ / 2π) {(− Vs / As ₁ ) cosu + (Vc / Ac ₁ ) sinu} (29) where λ: the period of the sine wave SA1 and the cosine wave SB1 u: 2πx / λ x: Positions As ₁ and Ac _{1 of the} encoder 10: Amplitudes Vs and Vc of the sine wave SA1 and cosine wave SB1, respectively: Sine wave SA1 and cosine wave SB1 obtained by the offset detecting means 16 Each offset

In this embodiment, the calculation result S2 of the interpolation error E obtained by the interpolation error estimation device 14 is
It is sent to the interpolation error correction device 20. Interpolation error correction device 2
At 0, the outputs SA3, SB3 of the interpolation circuit 12 are adjusted by the interpolation error E obtained by the interpolation error estimator 14 and the adjusted outputs SA4, SB4 are output. The output signal processing device of the encoder 10 that employs the interpolation error estimation device 14 according to the present embodiment is roughly configured as described above, and its operation will be described below with reference to FIG.

First, the sine wave SA output from the encoder
1 and cosine wave SB1 are input to an interpolation circuit and an interpolation error estimation device. The interpolation error estimation device first performs a detection step. That is, in the detection step, first, the maximum value and the minimum value of the sine wave SA1 and the cosine wave SB1 are detected by the method described in any of the following, for example. (1) Compare the sampled point with the currently stored maximum value, and if the stored maximum value is smaller than the sampled point, replace the stored maximum value with the sampled point. (2) Described in Japanese Patent Laid-Open No. 10-311741,
The cosine wave is sampled at the zero cross of the sine wave, the sine wave is sampled at the zero cross of the cosine wave, and the maximum value and the minimum value are gradually approached.

When the maximum and minimum values of the sine wave SA1 and the cosine wave SB1 are obtained as described above, the offset detecting step (s10) is performed. That is, in the offset detection step, the offset detection means obtains the sine wave DC offset and the cosine wave DC offset from the average of the maximum value and the minimum value of the sine wave SA1 and the cosine wave SB1.

In this embodiment, the sine wave SA1 and
And the difference between the maximum and minimum values of cosine wave SB1
Twice the amplitude of the chord wave SA1 and the cosine wave SB1 (2As₁，
2 Ac ₁). Therefore, the sine wave SA1 and
And the cosine wave SB1 from the difference between the maximum and minimum values, the sine
Each amplitude of the wave SA1 and the cosine wave SB1 (As₁, Ac₁)
Ask. Then, after the offset is detected, the interpolation error E
The calculation step (s12) is performed.

Here, conventionally, there is no suitable technique for modeling the interpolation error of the encoder, and it takes time and the estimated error value is inaccurate if the conventional simulation is used. There was a problem like that. Therefore, a characteristic of the present embodiment is that the interpolation error due to the offset is modeled.

That is, in this embodiment, the sine wave SA1 and the cosine wave SB1 input from the encoder to the interpolation circuit.
Is, for example, including an offset error, and the sine wave SA1 and the cosine wave SB1 including the error can be expressed by the formula 28. At this time, in the present embodiment, in the calculation step, the calculation means causes the sine wave DC calculated by the offset detection means.
The offset value and the cosine wave DC offset value are substituted into the approximate expression of the interpolation error due to the offset, which is the characteristic of the present embodiment, that is, Expression 29, to obtain the interpolation error.

As described above, in the present embodiment, the modeling of the interpolation error due to the DC offset has succeeded. Therefore, the DC offset is detected, and this is substituted into the approximate expression of the interpolation error E characteristic of the present embodiment, That is, the interpolation error E can be accurately and easily obtained by substituting it in the equation (29). Then, in the present embodiment, the calculation result S2 of the interpolation error E thus estimated is output to the output SA3 of the interpolation circuit 12 by the interpolation error correction device 20 and the like described later.
By performing adjustment such as subtraction from SB3, the interpolation error of the encoder 10 will be corrected.

As described above, according to the output signal processing device of the encoder 10 which employs the interpolation error estimation device 14 according to the present embodiment, the interpolation error of the encoder 10 due to the offset is modeled by the mathematical expression 29. Was successful. As a result, in the present embodiment, the interpolation error due to the offset can be easily and accurately estimated.

In this embodiment, an example using the ADC and the LUT as the interpolation circuit 12 has been described.
In addition, an ADC and an ATAN arithmetic DSP or the like may be used. In addition, in the present embodiment, the mathematical expression 29 includes trigonometric functions sin and cos, and for this calculation, there is a method using a polynomial obtained by Taylor expansion. Since this polynomial is in the form of sum of products calculation, the digital signal processor (DS
P) is preferably used.

[0048]Second embodiment FIG. 3 shows an interpolation error estimation device according to the second embodiment of the present invention.
Of the encoder output signal processing device
Success is shown. In this embodiment, the parameters
Assuming offset and amplitude ratio as
Example of estimating interpolation error based on set and amplitude ratio
explain. In addition, the present embodiment is different from the first embodiment.
Reference numeral 100 is added to the corresponding portion. The output shown in the figure
The force signal processing device includes an encoder 110 and an interpolation circuit (internal
Insertion means) 112 and the interpolation error characteristic of the present embodiment.
A difference estimation device 114 is provided.

Here, the encoder 110 is a sine wave (A-phase sine wave) for detecting the position of the encoder 110.
SA1 and cosine wave (B-phase sine wave) SB1 are output.
The interpolation circuit 112 includes, for example, an analog / digital converter (not shown), a look-up table memory (not shown), and the like. For example, the sine wave SA1 and the cosine wave SB1 output from the encoder 110 have a predetermined frequency. Sampling with an analog / digital converter (AD
Converted to digital data by C). The look-up table memory stores a look-up table (LUT) that obtains phase angle data at each sampling point based on the digital data, and interpolates the sine wave SA1 and cosine wave SB1 output from the encoder 110. Then
Obtain high resolution phase angle data.

A feature of this embodiment is that the interpolation error estimation device 114 is provided.
The sine wave SA1 and the cosine wave SB1 input to the interpolation circuit 112 from 10 include, for example, an error in the offset and the amplitude ratio, and the sine wave SA1 and the cosine wave SB1 including the error are
When it can be expressed by the following formula 30, the interpolation error estimation device 1
14, the interpolation error due to the offset and the amplitude ratio is estimated. In the present embodiment, the interpolation error estimation device 114
Are offset detection means 116 and amplitude ratio detection means 12
2 and a calculation means 118.

Then, from the encoder 110 to the interpolation circuit 1
Signal line 1 for sending sine wave SA1 and cosine wave SB1 to 12
The input side of the interpolation error estimation device 114 is connected to 11a and 111b via signal lines 113a and 113b.
The output side of the interpolation error estimation device 114 is connected to the interpolation error correction device 120 by a signal line 115. For this reason,
The offset detecting means 116 detects the maximum value and the minimum value of the sine wave SA1 and the cosine wave SB1 input from the encoder 110 to the interpolation circuit 112, and takes their averages as the sine wave DC offset and the cosine wave DC offset, respectively. Ask.

Further, the amplitude ratio detecting means 122 uses the sine wave
The difference between the maximum and minimum values of SA1 and cosine wave SB1
The amplitude (2 times the amplitude of the sine wave SA1 and the cosine wave SB1 respectively)
As ₁, 2Ac₁). Therefore, the sine wave S
Before the difference between the maximum and minimum values of A1 and cosine wave SB1
Each amplitude of the sine wave SA1 and the cosine wave SB1 (As₁, Ac
₁), The amplitude ratio of the sine wave SA1 and the cosine wave SB1
(As₁, Ac₁). The computing means 118 is
The sine wave DC offset obtained by the offset detection means 116.
Fuss value and cosine wave DC offset value, and the vibration
The amplitude ratio obtained by the width ratio detecting means 122 is expressed by the following mathematical formula 31
To obtain the interpolation error E due to the offset and the amplitude ratio.
Meru.

[0053]

Sine wave SA1 = As ₁ sin (2πx / λ) + Vs cosine wave SB1 = Ac ₁ cos (2πx / λ) + Vc (30)

[Equation 31] Interpolation error E = (λ / 2π) {(− Vs / As ₁ ) cosu + (Vc / Ac ₁ ) sinu + (Ac ₁ / As ₁ −1) sinucosu} (31) where λ : Cycles of the sine wave SA1 and the cosine wave SB1 u: 2πx / λ x: Positions As ₁ and Ac _{1 of the} encoder 110: Amplitudes Vs and Vc of the sine wave SA1 and the cosine wave SB1: At the offset detecting means 116 Each offset Ac ₁ / As _{1 of} the sine wave SA1 and the cosine wave SB1 obtained: the amplitude ratio obtained by the amplitude ratio detecting means 122.

In the present embodiment, the calculation result S2 of the interpolation error E obtained by the interpolation error estimation device 114.
Is sent to the interpolation error correction device 120. In the interpolation error correction device 120, the outputs SA3 and SB3 of the interpolation circuit 112 are output.
Is the interpolation error E determined by the interpolation error estimation device 114.
And output as adjusted data SA4, SB4. Interpolation error estimation device 114 according to the present embodiment
The output signal processing device of the encoder 110 adopting
The configuration is roughly as described above, and its operation will be described below with reference to FIG.

First, the sine wave SA output from the encoder
1 and cosine wave SB1 are input to an interpolation circuit and an interpolation error estimation device. The interpolation error estimation device first performs a detection step. That is, in the detection step, first, the maximum value and the minimum value of the sine wave SA1 and the cosine wave SB1 are detected by the method described in any of the following, for example.

(1) The sampled point is compared with the currently stored maximum value, and if the stored maximum value is smaller than the sampled point, the stored maximum value is replaced with the sampled point. (2) Described in Japanese Patent Laid-Open No. 10-311741,
The cosine wave is sampled at the zero cross of the sine wave, the sine wave is sampled at the zero cross of the cosine wave, and the maximum value and the minimum value are gradually approached.

When the maximum and minimum values of the sine wave SA1 and the cosine wave SB1 are obtained as described above, the offset detection step and the amplitude ratio detection step (s110) are performed. That is,
In the offset detecting step, the offset detecting means obtains the sine wave DC offset and the cosine wave DC offset from the average of the maximum value and the minimum value of the sine wave SA1 and the cosine wave SB1.

In the amplitude ratio detecting step, the sine wave SA
1 and the difference between the maximum and minimum values of cosine wave SB1
Double the amplitude (2As) of the sine wave SA1 and the cosine wave SB1
₁, 2Ac₁). Therefore, the sine wave SA
1 and the difference between the maximum and minimum values of the cosine wave SB1
Each amplitude of the sine wave SA1 and the cosine wave SB1 (As₁, A
c ₁), The amplitude ratio of the sine wave SA1 and the cosine wave SB1
(As₁, Ac₁). And the offset and
And the amplitude ratio are detected, the interpolation error E is calculated (s112).
I do.

Here, as described above, there are a plurality of parameters of the error of the two-phase sine wave output from the encoder and input to the interpolation circuit, and their interaction was not clear. Therefore, each parameter is calculated at a plurality of levels to obtain the error. The maximum error was estimated by trial and error, such as finding the maximum error from them. With such a method, there is a problem that a simulation time is required and an estimated value of an error is inaccurate.

Therefore, what is special in this embodiment is that the interpolation error due to the interaction between the offset and the amplitude ratio is modeled. That is, in this embodiment,
It is assumed that the sine wave SA1 and the cosine wave SB1 input from the encoder to the interpolation circuit include, for example, an error in the offset and the amplitude ratio, and the sine wave SA1 and the cosine wave SB1 including the error can be represented by the mathematical expression 30. At this time, in the present embodiment, in the calculation step, the calculation means uses the sine wave DC offset value, the cosine wave DC offset value, and the amplitude ratio obtained by the offset detection means, which are characteristic of the present embodiment. And the approximation formula of the interpolation error due to the amplitude ratio, that is, the above formula 31 is substituted to obtain the interpolation error due to the interaction between the DC offset and the amplitude ratio.

As described above, in this embodiment, since the interpolation error due to the interaction of the DC offset and the amplitude ratio has been successfully modeled, the DC offset and the amplitude ratio are detected, and this is detected as a characteristic feature of the present embodiment. By substituting into the approximate expression of the insertion error E, that is, substituting into the above expression 31, the interpolation error E due to the interaction between the DC offset and the amplitude ratio can be accurately and easily obtained. Then, in the present embodiment, adjustment such as subtraction of the calculation result S2 of the interpolation error E thus estimated from the outputs SA3, SB3 of the interpolation circuit 112 by the interpolation error correction device 120 and the like, which will be described later. By doing so, the interpolation error of the encoder 110 will be corrected.

As described above, according to the output signal processing device of the encoder 110 which employs the interpolation error estimation device 114 according to the present embodiment, the interpolation error of the encoder 110 due to the interaction between the offset and the amplitude ratio is calculated as described above. We have succeeded in modeling with Equation 31. As a result, in the present embodiment, the interpolation error due to the interaction between the offset and the amplitude ratio can be estimated easily and accurately.

In this embodiment, the interpolation circuit 112 and
Then, the example using the ADC and the LUT was explained.
However, in addition to this, an ADC and any other ATAN arithmetic DSP
Can also be used. Further, in the present embodiment,
Equation 31 includes trigonometric functions sin and cos
However, for this operation, a polynomial
There is a way to do it. This polynomial has the form
Therefore, the digital signal processor whose calculation speed has been increased
It is preferable to use a DSP (DSP). In the formula 31
Be careful a = -λ / 2π · Vs / As₁ b = + λ / 2π · Vs / As₁ c = + λ / 4π · {(Ac₁/ As₁) -1} Then, if Taylor expansion is performed up to the n = 12th order,
Get 2.

[0064]

[Equation 32]   Interpolation error E = a + (b + 2c) u + (-a / 2) u² + (-b / 6-4c / 3) u³ + (a / 24) u^Four + (b / 12 0 + 4c / 15) u^Five+ (-a / 720) u⁶ + (-b / 5040-8c / 315) u⁷+ (a / 40320) u⁸ + (b / 3628 80 + 4c / 2835) u⁹+ (-a / 3628800) u^Ten + (-b / 39916800-8c / 155925) u¹¹+ (a / 4 79001600) u¹²                                                               … (32)

[0065]Third embodiment FIG. 5 shows an interpolation error estimation device according to the third embodiment of the present invention.
The schematic configuration of an encoder that employs a device is shown. Book
In the embodiment, the offset and the phase difference are used as parameters.
Based on the detected offset and phase difference,
An example of estimating the insertion error will be described. In addition, this embodiment
Then, a reference numeral 200 is given to a portion corresponding to the first embodiment.
Is added.

The output signal processing device shown in the figure comprises an encoder 210, an interpolation circuit (interpolation means) 212, and an interpolation error estimation device 214 characteristic of this embodiment.
Here, the encoder 210 is
The sine wave (A-phase sine wave) SA1 and the cosine wave (B-phase sine wave) SB1 for detecting the position of are output. The interpolation circuit 212 includes, for example, an analog / digital converter (not shown), a look-up table memory (not shown), and the like. For example, the sine wave SA1 and the cosine wave SB1 output from the encoder 210 have a predetermined frequency. The data is sampled by and converted into digital data by an analog / digital converter (ADC). The lookup table memory is
A sine wave SA output from the encoder 10 is stored by storing a look-up table (LUT) for obtaining the phase angle data of each sampling point based on the digital data.
1 and cosine wave SB1 are interpolated to obtain high resolution phase angle data.

A feature of this embodiment is that the interpolation error estimation device 214 is provided.
The sine wave SA1 and the cosine wave SB1 input to the interpolation circuit 212 from 10 include, for example, an error in offset and phase difference, and the sine wave SA1 and the cosine wave SB1 including the error are
When it can be expressed by the following formula 33, the interpolation error estimation device 2
14 estimates the interpolation error due to the interaction of offset and phase difference. In the present embodiment, the interpolation error estimation device 214 includes an offset detection means 216, a phase difference detection means 224, and a calculation means 218. Then, the signal lines 211a and 211b for sending the sine wave SA1 and the cosine wave SB1 from the encoder 210 to the interpolation circuit 212 are connected to the signal lines 213a and 213 at the input side of the interpolation error estimation device 214.
It is connected via b. The output side of the interpolation error estimation device 214 is connected to the interpolation error correction device 220 by a signal line 215.

Therefore, the offset detecting means 216
Detects the maximum value and the minimum value of the sine wave SA1 and the cosine wave SB1 input from the encoder 210 to the interpolation circuit 212, and obtains their averages as a sine wave DC offset and a cosine wave DC offset, respectively.

Further, in this embodiment, the difference between the maximum value and the minimum value of the sine wave SA1 and the cosine wave SB1 input from the encoder 210 to the interpolation circuit 212 is twice as large as the sine wave SA1 and the cosine wave SB1, respectively. Amplitude (2As ₁ , 2Ac
₁ ). Therefore, from the difference between the maximum value and the minimum value of the sine wave SA1 and the cosine wave SB1, the sine wave SA
1 and each amplitude (As ₁ , Ac ₁ ) of the cosine wave SB1 is obtained. The phase difference detecting means 224 rotates the coordinate axes of the sine wave SA1 and the cosine wave SB1 by, for example, 45 degrees, and calculates the phase difference from the ratio (k = b / a) of the major axis length b and the minor axis length a. (Ε = sin ⁻¹ ((1-k ² ) / (1 + k ² )) is calculated.
The offset values of the sine wave SA1 and the cosine wave SB1 obtained in 16 are substituted into the following formula 34, and the interpolation error E due to the offset is obtained.

[0070]

Sine wave SA1 = As ₁ sin (2πx / λ) + Vs cosine wave SB1 = Ac ₁ cos (2πx / λ + ε) + Vc (33)

[Equation 34] Interpolation error E = (λ / 2π) {(− Vs / As ₁ ) cosu + (Vc / Ac ₁ ) sinu −εsin ² u} (34) where λ: sine wave SA1 and cosine Cycle u of wave SB1: 2πx / λ x: Positions As ₁ and Ac _{1 of the} encoder 210: Amplitudes Vs and Vc of the sine wave SA1 and the cosine wave SB1: the sine wave SA1 and the sine wave SA1 obtained by the offset detecting means 216, respectively. Each offset ε of cosine wave SB1: phase difference obtained by the phase difference detecting means 224

In the present embodiment, the calculation result S2 of the interpolation error E obtained by the interpolation error estimation device 214 is calculated.
Is sent to the interpolation error correction device 220. In the interpolation error correction device 220, the outputs SA3, SB3 of the interpolation circuit 212
Is the interpolation error E determined by the interpolation error estimation device 214.
And output as adjusted data SA4, SB4. Interpolation error estimation device 214 according to the present embodiment
The output signal processing device of the encoder 210 that adopts
The configuration is roughly as described above, and its operation will be described below with reference to FIG.

First, the sine wave SA output from the encoder
1 and cosine wave SB1 are input to an interpolation circuit and an interpolation error estimation device. The interpolation error estimation device first performs a detection step. That is, in the detection step, first, the maximum value and the minimum value of the sine wave SA1 and the cosine wave SB1 are detected by the method described in any of the following, for example.

(1) The sampled point is compared with the currently stored maximum value, and if the stored maximum value is smaller than the sampled point, the stored maximum value is replaced with the sampled point. (2) Described in Japanese Patent Laid-Open No. 10-311741,
The cosine wave is sampled at the zero cross of the sine wave, the sine wave is sampled at the zero cross of the cosine wave, and the maximum value and the minimum value are gradually approached. When the maximum value and the minimum value of the sine wave SA1 and the cosine wave SB1 are obtained as described above, the offset detection step and the phase difference detection step (s210) are performed.

That is, in the offset detection process, it is turned off.
The set detection means controls the maximum of the sine wave SA1 and the cosine wave SB1.
From the average of the maximum and minimum values, the sine wave DC offset and
Find the cosine wave DC offset. Further, in this embodiment,
Maximum and minimum values of the sine wave SA1 and cosine wave SB1
Of the sine wave SA1 and cosine wave SB1
Amplitude of (2As₁, 2Ac ₁). Because of this, before
Of the maximum and minimum values of the sine wave SA1 and the cosine wave SB1
From the difference, each amplitude of the sine wave SA1 and the cosine wave SB1
(As₁, Ac₁).

Further, a phase difference detecting step is performed. In the phase difference detecting step, the coordinate axes of the sine wave SA1 and the cosine wave SB1 are rotated by, for example, 45 degrees, and the major axis length b and the minor axis length a are obtained.
From the ratio (k = b / a) of the phase difference (ε = sin ⁻¹ ((1-
k ² ) / (1 + k ² )) is calculated. Then, after detecting the offset and the phase difference, the step of calculating the interpolation error E (s2
12) is performed.

Here, as described above, there are a plurality of parameters of the error of the two-phase sine wave output from the encoder and input to the interpolation circuit, and their interaction was not clear. Therefore, each parameter is calculated at a plurality of levels to obtain the error. The maximum error was estimated by trial and error, such as finding the maximum error from them. With such a method, there is a problem that a simulation time is required and an estimated value of an error is inaccurate.

Therefore, the characteristic feature of this embodiment is that the interpolation error due to the interaction between the offset and the phase difference is modeled. That is, in this embodiment,
It is assumed that the sine wave SA1 and the cosine wave SB1 input from the encoder to the interpolation circuit include, for example, an error of offset and phase difference, and the sine wave SA1 and the cosine wave SB1 including the error can be represented by the above expression 33.

At this time, in the present embodiment, in the calculation step, the calculation means causes the sine wave DC offset value and the cosine wave DC offset value obtained by the offset detection means,
Further, the phase difference obtained by the phase difference detecting means is substituted into an approximate expression of the interpolation error due to the offset and the phase difference, that is, the equation 34, which is characteristic of the present embodiment, and the interpolation error is obtained.

As described above, in the present embodiment, the modeling of the interpolation error due to the interaction between the DC offset and the phase difference has succeeded. Therefore, the DC offset value and the phase difference are detected, which are characteristic of the present embodiment. The interpolation error E can be accurately and easily obtained by substituting it into the approximate expression of the interpolation error E, that is, by substituting it into the above-mentioned formula 34. Then, in the present embodiment, the calculation result S2 of the interpolation error E thus estimated is used as an interpolation error correction device 22 to be described later.
The interpolation error of the encoder 210 is corrected by adjusting the output SA3, SB3 of the interpolation circuit 212 by 0 or the like.

As described above, according to the output signal processing device of the encoder 210 that employs the interpolation error estimation device 214 according to the present embodiment, the interpolation error of the encoder 210 due to the offset and the phase difference can be calculated by the formula 34. Succeeded in modeling. As a result, in the present embodiment, it is possible to easily and accurately estimate the interpolation error due to the offset and the phase difference.

In the present embodiment, an example in which the ADC and the LUT are used as the interpolating circuit 212 has been described. However, in addition to this, an ADC and an ATAN arithmetic DSP or the like may be used. Further, in the present embodiment,
The formula 34 includes trigonometric functions sin and cos, and for this calculation, there is a method using a polynomial obtained by Taylor expansion. Since this polynomial is in the form of multiply-accumulate operation, it is preferable to use a digital signal processor (DSP) whose operation speed is high.

[0082]Fourth embodiment FIG. 7 shows an interpolation error estimation device according to the fourth embodiment of the present invention.
A schematic configuration of an encoder that employs a device is shown.
In addition, in the present embodiment, the offset as a parameter,
Assuming the amplitude ratio and phase difference, the detected offset and vibration
An example of estimating the interpolation error based on the width ratio and phase difference is explained.
Reveal In addition, in the present embodiment, it is not the same as the first embodiment.
Reference numeral 300 is added to the corresponding portion and description thereof is omitted.
It

The output signal processing device shown in the figure comprises an encoder 310, an interpolation circuit (interpolation means) 312, and an interpolation error estimation device 314 characteristic of this embodiment.
Here, the encoder 310 is
The sine wave (A-phase sine wave) SA1 and the cosine wave (B-phase sine wave) SB1 for detecting the position of are output. The interpolation circuit 312 includes, for example, an analog / digital converter (not shown), a look-up table memory (not shown), and the like. For example, the sine wave SA1 and the cosine wave SB1 output from the encoder 310 have a predetermined frequency. The data is sampled by and converted into digital data by an analog / digital converter (ADC). The lookup table memory is
A look-up table (LUT) for obtaining phase angle data at each sampling point based on the digital data is stored, and the sine wave S output from the encoder 310 is stored.
By interpolating A1 and cosine wave SB1, high-resolution phase angle data is obtained.

The feature of this embodiment is that the interpolation error estimation device 314 is provided.
The sine wave SA1 and the cosine wave SB1 input from 10 to the interpolation circuit 312 include, for example, an error of the offset, the amplitude ratio, and the phase difference, and the sine wave SA1 and the cosine wave S including the error.
When B1 can be represented by the following Expression 35, the interpolation error estimation device 314 estimates the interpolation error due to the offset.

In the present embodiment, the interpolation error estimation device 3
14 includes an offset detection unit 316, an amplitude ratio detection unit 322, a phase difference detection unit 324, and a calculation unit 318. Then, from the encoder 310 to the interpolation circuit 312
Each signal line 311 for sending the sine wave SA1 and the cosine wave SB1 to the
The input side of the interpolation error estimation device 314 is connected to a and 311b through signal lines 313a and 313b. The output side of the interpolation error estimation device 314 is connected to the interpolation error correction device 320 by a signal line 315. Therefore, the offset detecting means 316 is configured so that the sine wave SA1 and the cosine wave SB input from the encoder 310 to the interpolation circuit 312 are input.
The maximum value and the minimum value of 1 are detected, and their averages are obtained as a sine wave DC offset and a cosine wave DC offset, respectively.

In the amplitude ratio detecting means 322, the difference between the maximum value and the minimum value of the sine wave SA1 and the cosine wave SB1 input from the encoder 310 to the interpolation circuit 312 is calculated as the sine wave SA1 and the cosine wave SB1, respectively. The amplitude is twice as much (2As ₁ , 2Ac ₁ ). Therefore, from the difference between the maximum value and the minimum value of the sine wave SA1 and the cosine wave SB1, the amplitude (As) of the sine wave SA1 and the cosine wave SB1 is calculated.
₁ , Ac ₁ ) to obtain the sine wave SA1 and cosine wave SB
From each amplitude of _{1 (As 1, Ac 1)} , determine the amplitude ratio of the sine wave SA1 and cosine wave _{SB1 (As 1, Ac 1)} .

The phase difference detecting means 324 uses the sine wave SA
1 and the coordinate axis of the cosine wave SB1 are rotated by, for example, 45 degrees, and a phase difference (ε = sin ⁻¹ ((1- k ² ) / (1+
k ² )). The calculating means 318 detects the offset values of the sine wave SA1 and the cosine wave SB1 obtained by the offset detecting means 316, and the amplitude ratio detecting means 322.
Substituting the amplitude ratio obtained in step 1 and the phase difference obtained by the phase difference detecting means 324 into the following formula 36, the interpolation error E due to the offset, the amplitude ratio and the phase difference is obtained.

[0088]

Sine wave A = As ₁ sin (2πx / λ) + Vs cosine wave B = Ac ₁ cos (2πx / λ + ε) + Vc (35)

[Equation 36] Interpolation error E = (λ / 2π) {(− Vs / As ₁ ) cosu + (Vc / Ac ₁ ) sinu + (Ac ₁ / As ₁ −1) sinucosu −εsin ² u} (36) Here, λ: period u of the sine wave SA1 and cosine wave SB1 u: 2πx / λ x: positions As ₁ and Ac _{1 of the} encoder 310: amplitudes Vs and Vc of the sine wave SA1 and cosine wave SB1: the offset Offsets Ac ₁ / As _{1 of} sine wave SA1 and cosine wave SB1 obtained by detecting means 316: Amplitude ratio ε of sine wave SA1 and cosine wave SB1 obtained by amplitude ratio detecting means 322: Phase difference detecting means 324 Sine wave SA
1 and cosine wave SB1 phase difference

In the present embodiment, the calculation result S2 of the interpolation error E obtained by the interpolation error estimation device 314 is calculated.
Is sent to the interpolation error correction device 320. In the interpolation error correction device 320, the outputs SA3 and SB3 of the interpolation circuit 312 are output.
Is the interpolation error E determined by the interpolation error estimation device 314.
And output as adjusted data SA4, SB4. Interpolation error estimation device 314 according to the present embodiment
The output signal processing device of the encoder 310 adopting
The configuration is roughly as described above, and its operation will be described below with reference to FIG.

First, the sine wave SA output from the encoder
1 and cosine wave SB1 are input to an interpolation circuit and an interpolation error estimation device. The interpolation error estimation device first performs a detection step. That is, in the detection step, first, the maximum value and the minimum value of the sine wave SA1 and the cosine wave SB1 are detected by the method described in any of the following, for example.

(1) The sampled point is compared with the currently stored maximum value, and if the stored maximum value is smaller than the sampled point, the stored maximum value is replaced with the sampled point. (2) Described in Japanese Patent Laid-Open No. 10-311741,
The cosine wave is sampled at the zero cross of the sine wave, the sine wave is sampled at the zero cross of the cosine wave, and the maximum value and the minimum value are gradually approached.

When the maximum and minimum values of the sine wave SA1 and the cosine wave SB1 are obtained as described above, the offset detection step, the amplitude ratio detection step, and the phase difference detection step (s31
0) is performed. That is, in the offset detection step, the offset detection means obtains the sine wave DC offset and the cosine wave DC offset from the average of the maximum value and the minimum value of the sine wave SA1 and the cosine wave SB1.

In the amplitude ratio detecting step, the sine wave SA
1 and the difference between the maximum and minimum values of cosine wave SB1
Double the amplitude (2As) of the sine wave SA1 and the cosine wave SB1
₁, 2Ac₁). Therefore, the sine wave SA
1 and the difference between the maximum and minimum values of the cosine wave SB1
Each amplitude of the sine wave SA1 and the cosine wave SB1 (As₁, A
c ₁) Is obtained, and each of the sine wave SA1 and the cosine wave SB1 is obtained.
Amplitude (As₁, Ac₁) From the sine wave SA1 and cosine
Amplitude ratio of wave SB1 (As₁, Ac₁). In addition,
Perform the phase difference detection step.

In the phase difference detecting step, the coordinate axes of the sine wave SA1 and the cosine wave SB1 are rotated, for example, by 45 degrees, and the ratio of the major axis length b to the minor axis length a (k = b / a) is calculated. The phase difference (ε = sin ⁻¹ ((1−k ² ) / (1 + k ² )) is calculated, and after the offset, the amplitude ratio, and the phase difference are detected, the calculation step (s312) of the interpolation error E is performed. .

Here, as described above, there are a plurality of parameters of the error of the two-phase sine wave output from the encoder and input to the interpolation circuit, and their interaction was not clear. Therefore, each parameter is calculated at a plurality of levels to obtain the error. The maximum error was estimated by trial and error, such as finding the maximum error from them. With such a method, there is a problem that a simulation time is required and an estimated value of an error is inaccurate.

Therefore, what is special in this embodiment is that the interpolation error due to the interaction of the offset, the amplitude ratio, and the phase difference is modeled. That is, in the present embodiment, the sine wave SA1 and the cosine wave SB1 input from the encoder to the interpolation circuit include, for example, errors of offset, amplitude ratio, and phase difference, and the sine wave SA1 and cosine wave SB1 including the errors are It can be expressed by Equation 35.

At this time, in the present embodiment, in the calculation step, the calculation means causes the calculation means to detect each DC offset value, the amplitude ratio calculated in the amplitude ratio detection step, and the phase difference detection means. The phase difference obtained by the above equation is used as an approximate expression of the interpolation error due to the offset, the amplitude ratio, and the phase difference, that is, the above-mentioned expression 3
Substituting into 6, the interpolation error is obtained.

As described above, in the present embodiment, the offset,
Since the interpolation error due to the amplitude ratio and the phase difference has been successfully modeled, the offset value, the amplitude ratio and the phase difference are detected, and this is substituted into the approximate expression of the interpolation error E characteristic of the present embodiment, that is, By substituting in the formula 36, the interpolation error E can be accurately and easily obtained. And
In the present embodiment, the interpolation error E estimated in this way
The interpolation error of the encoder 310 is corrected by adjusting the calculation result S2 of (1) to be subtracted from the outputs SA3 and SB3 of the interpolation circuit 312 by an interpolation error correction device 320 described later.

As described above, according to the output signal processing device of the encoder 310 which employs the interpolation error estimation device 314 according to the present embodiment, the interpolation error of the encoder 310 due to the offset, the amplitude ratio and the phase difference is We have succeeded in modeling with Equation 36. As a result, in the present embodiment, the interpolation error due to the offset, the amplitude ratio and the phase difference can be easily and accurately estimated.

In this embodiment, an example in which the ADC and the LUT are used as the interpolating circuit 312 has been described, but in addition to this, an ADC and an ATAN arithmetic DSP or the like can be used. Further, in the present embodiment,
The formula 36 includes trigonometric functions sin and cos, and this calculation includes a method using a polynomial obtained by Taylor-expansion of these. Since this polynomial is in the form of multiply-accumulate operation, it is preferable to use a digital signal processor (DSP) whose operation speed is high.

[0101]Interpolation error correction In this way, the approximate expression of the interpolation error according to the present embodiment is used.
The interpolation error E is obtained by
Adjust the output by subtracting it from the output of the interpolation circuit.
U Here, conventionally, the method of encoder interpolation error correction and
And described in, for example, Japanese Patent Laid-Open No. 11-316137.
Signal processing
Is complicated and takes time to process.
is there. In addition, conventionally, it has been difficult to estimate the interpolation error of the encoder.
There was no suitable technique for
Positive, too, was difficult to do easily and accurately. There
In the interpolation error correction device according to the present embodiment,
Using the interpolation error E obtained by the interpolation error estimation device of
The output of the interpolation circuit is corrected. Below, the static of the interpolation error
Correction and dynamic correction will be described.

[0102]First embodiment FIG. 9 shows an interpolation error correction device according to the first embodiment of the present invention.
Of the encoder output signal processing device
Success is shown. In this embodiment, static correction is
I am assuming. Further, reference numerals are given to portions corresponding to those in FIG.
A description is omitted by adding 400. In this embodiment,
Of the present invention described in any one of FIGS.
An insertion error estimation device 414 is provided. And the interpolation of the present invention
Calculation result of the interpolation error E obtained by the error estimation device 414
S2 is sent to the interpolation error correction device 420 in the subsequent stage. same
The interpolation error correction device 420 shown in FIG.
It comprises a stage 450 and an adjusting means 452.

Here, the correction data generating means 450.
Is the position x of the encoder 414 based on the calculation result of the interpolation error E obtained by the interpolation error estimation device 414 of the present invention.
The correction data of is generated. Also, the adjusting means 452
Is the correction data generated by the correction data generating means 450, corrects the outputs SA3, SB3 of the encoder 414, and outputs the corrected data SA4, SB4.

The characteristic feature of this embodiment is that the adjusting means 452 causes the look-up table memory 454 to operate.
That is, the CPU 456 is provided. The memory 45
Reference numeral 4 denotes, for example, a non-volatile memory or the like, and stores a look-up table (hereinafter referred to as LUT). This L
The UT stores, for example, the correction data from the correction data generating means 450. For example, this LUT stores information necessary for correcting the interpolation error, such as the calculation result (offset value or the like) of the approximation formula of each parameter or the correction coefficient of the approximation formula of the interpolation error E.

The CPU 456 reads the LUT stored in the memory 454 when the power of the apparatus is turned on,
With the correction data of the LUT, the output SA3 of the interpolation circuit 412
Corrected SB3 and adjusted this data SA4, SB4
Output as. As described above, the present embodiment has the interpolation error E
Can be easily and accurately estimated by using the interpolation error estimation device of the present invention, the calculation result (offset value, etc.) of the approximation formula of each parameter, or the correction coefficient of the approximation formula of the interpolation error E, etc. Information necessary for correcting the interpolation error of
It is stored in the LUT 54.

As a result, the CPU 456 determines that the interpolation circuit 41
By correcting the outputs SA3 and SB3 of No. 2 with the correction data stored in the LUT of the memory 454, the interpolation error can be corrected easily and accurately. In the present embodiment, the new creation or update of the LUT may be performed in real time, for example, every time the encoder is used, or in advance of using the encoder, such as factory adjustment or maintenance adjustment.

[0107]Second embodiment FIG. 10 shows the interpolation error correction according to the second embodiment of the present invention.
Of encoder output signal processing device
The configuration is shown. In this embodiment, dynamic correction is
I am assuming. In addition, in the portion corresponding to the first embodiment
Is added with reference numeral 100 and its description is omitted. Shown in the figure
The interpolation error correction device 520 includes a correction data generation unit 550.
And adjusting means 552.

Here, the correction data generating means 550.
Generates the correction data of each position of the encoder 512 based on the interpolation error E obtained by the interpolation error estimation device 514 of the present invention. Further, the adjusting means 552 corrects the outputs SA3, SB3 of the interpolation circuit 512 with the correction data generated by the correction data generating means 550, and outputs the corrected data SA4, SB4.

The feature of this embodiment is that the correction data generated by the correction data generating means 550 is
That is, the dynamic correction is performed during the operation of the interpolation circuit 512, that is, the independent interpolation correction during the normal operation is performed without storing the data in the LUT of the non-volatile memory as described above. Therefore, in the present embodiment, the correction data generation means 550 is
Correction data for each position of the encoder is sequentially generated.
Further, the adjusting means 552 is composed of, for example, a CPU 556 or the like, and the CPU 556 corrects the data SA3, SB3 sequentially output from the interpolation circuit 512 with the correction data sequentially output from the generating means 552, and corrects this. It is output as the completed data SA4 and SB4.

As described above, according to the present embodiment, the correction data is generated based on the interpolation error obtained by using the interpolation error estimation device of the present invention which can easily and accurately estimate the interpolation error E,
This is not stored in the LUT of a non-volatile memory, but the output of the interpolation circuit is corrected by the interpolation error when the interpolation circuit operates. As a result, in the present embodiment, the correction data generation means calculates the correction data based on the interpolation error obtained by using the interpolation error estimation device of the present invention that can easily and accurately estimate the interpolation error E. By generating and by correcting the output of the interpolation circuit by the CPU with the correction data, the interpolation error can be corrected easily and accurately as in the interpolation error correction device of the first embodiment. In addition, in the said structure, although the example which performed the static correction or the dynamic correction was demonstrated, you may use both together.

As described above, according to the interpolation error correction device of this embodiment, the calculation of the interpolation error caused by the parameter such as the DC offset can be performed quickly and easily without any other position reference. The interpolation can be corrected even after the interpolation calculation. In this embodiment, as an example of the applied product,
In photoelectric type and electromagnetic induction type, there are linear scales, linear gauges, and equipment products using the linear scales. Laser interferometers include laser interferometers.

[0112]

As described above, according to the interpolation error estimation method and apparatus of the present invention, it is provided with the calculation step (means) capable of modeling the interpolation error by the approximate expression. , The estimation of the interpolation error of the encoder can be performed easily and accurately. Further, in the present invention, since the calculation step (means) capable of modeling the interpolation error due to a plurality of parameters by the approximate expression is provided, the estimation of the interpolation error due to the interaction between a plurality of parameters is performed. It can be done easily and accurately. Further, according to the interpolation error correction device of the present invention, the interpolation error is estimated by using the interpolation error estimation method (device) of the present invention.
The output of the interpolation means can be adjusted easily and accurately based on the calculated interpolation error.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a schematic configuration around an interpolation error estimation device according to a first embodiment of the present invention.

FIG. 2 is a flowchart showing a procedure of an interpolation error estimation method according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram of a schematic configuration around an interpolation error estimation device according to a second embodiment of the present invention.

FIG. 4 is a flowchart showing a procedure of an interpolation error estimation method according to the second embodiment of the present invention.

FIG. 5 is an explanatory diagram of a schematic configuration around an interpolation error estimation device according to a third embodiment of the present invention.

FIG. 6 is a flowchart showing a procedure of an interpolation error estimation method according to the third embodiment of the present invention.

FIG. 7 is an explanatory diagram of a schematic configuration around an interpolation error estimation device according to a fourth embodiment of the present invention.

FIG. 8 is a flowchart showing a procedure of an interpolation error estimation method according to the fourth embodiment of the present invention.

FIG. 9 is an explanatory diagram of a schematic configuration around an interpolation error correction device according to the first embodiment of the present invention.

FIG. 10 is an explanatory diagram of a schematic configuration around an interpolation error correction device according to a second embodiment of the present invention.

[Explanation of symbols]

10, 110, 210, 310, 410, 510 Encoder 12, 112, 212, 312, 412, 512 Interpolation circuit (interpolation means) 14, 114, 214, 314, 414, 514 Interpolation error estimation device 16, 116 , 216, 316 Offset detection means 18, 118, 218, 318 Calculation means 20, 120, 220, 320, 420, 520 Interpolation error correction device 122, 322 Amplitude ratio detection means 224, 324 Phase difference detection means 450, 550 Correction Data generators 452, 552 Adjusting means 454 Look-up table memories 456, 556 CPU (adjusting means)

Claims (11)

[Claims] 1. An interpolation error estimation method for estimating an interpolation error when the A-phase and B-phase sine waves output from an encoder are interpolated by the interpolation means, wherein A input from the encoder to the interpolation means is used. The phase and B-phase sine waves include an offset error, and assuming that the sine wave including the error can be expressed by the following equation 1, the respective offsets of the A-phase and B-phase sine waves input from the encoder to the interpolation means are An offset detecting step for obtaining and an arithmetic step for substituting each offset of the A-phase and B-phase sinusoidal waves obtained in the offset detecting step into the following formula 2 to obtain an interpolation error E due to the offset are provided. Characteristic interpolation error estimation method. [Equation 1] A-phase sine wave = As ₁ sin (2πx / λ) + Vs B-phase sine wave = Ac ₁ cos (2πx / λ) + Vc (1) [Equation 2] Interpolation error E = (λ / 2π) {(−Vs / As ₁ ) cosu + (Vc / Ac ₁ ) sinu} (2) where λ: cycle of the sine wave u: 2πx / λ x: position of the encoder As ₁ , Ac ₁ : Ac: Amplitudes Vs and Vc of phase and B phase sine waves: Offsets of A phase and B phase sine waves obtained in the offset detection step 2. The interpolation error estimation method according to claim 1, wherein the A-phase and B-phase sine waves input from the encoder to the interpolation means include offset and amplitude ratio errors, and a sine wave including the errors. Is represented by the following formula 3, an amplitude ratio detection step of obtaining an amplitude ratio of the A phase and B phase sine waves input from the encoder to the interpolation means is provided, and the calculation step is obtained in the offset detection step. It is characterized in that the respective offsets of the A-phase and B-phase sine waves thus obtained and the amplitude ratio obtained in the amplitude ratio detecting step are substituted into the following formula 4 to obtain an interpolation error E due to the offset and the amplitude ratio. Interpolation error estimation method. ## EQU3 ## A-phase sine wave = As ₁ sin (2πx / λ) + Vs B-phase sine wave = Ac ₁ cos (2πx / λ) + Vc (3) ## EQU3 ## Interpolation error E = (λ / 2π) _{{(-Vs / As 1) cosu} + (Vc / Ac 1) sinu + (Ac 1 / As 1 -1) sinucosu} ... (4) where, lambda: the period of the sine wave u: 2πx / λ x: the Encoder Positions As ₁ and Ac ₁ : Amplitudes Vs and Vc of the A-phase and B-phase sine waves: Offsets A ₁ / As _{1 of} the A-phase and B-phase sine waves obtained in the offset detection step: The amplitudes Amplitude ratio obtained in the ratio detection process 3. The interpolation error estimation method according to claim 1, wherein the A-phase and B-phase sine waves input from the encoder to the interpolation means include offset and phase difference errors, and a sine wave including the errors. Is expressed by the following Equation 5, a phase difference detection step of obtaining a phase difference between the A-phase and B-phase sine waves input from the encoder to the interpolation means is provided, and the calculation step is obtained by the offset detection step. It is characterized in that the respective offsets of the A-phase and B-phase sinusoidal waves obtained and the phase difference obtained in the phase difference detecting step are substituted into the following formula 6 to obtain an interpolation error E due to the offset and the phase difference. Interpolation error estimation method. [Equation 5] A-phase sine wave = As ₁ sin (2πx / λ) + Vs B-phase sine wave = Ac ₁ cos (2πx / λ + ε) + Vc (5) [Equation 6] Interpolation error E = (λ / 2π) {(−Vs / As ₁ ) cosu + (Vc / Ac ₁ ) sinu −εsin ² u} (6) where λ: period of the sine wave u: 2πx / λ x: positions of the encoder As ₁ , Ac ₁ : Amplitudes Vs and Vc of the A-phase and B-phase sine waves: Offsets of the A-phase and B-phase sine waves obtained in the offset detection step ε: Phase differences obtained in the phase difference detection step 4. An interpolation error estimation device for estimating an interpolation error when the A-phase and B-phase sine waves output from an encoder are interpolated by the interpolation means, wherein A input from the encoder to the interpolation means. The phase and B-phase sine waves include an offset error, and assuming that the sine wave including the error can be expressed by the following formula 7, the offsets of the A-phase and B-phase sine waves input from the encoder to the interpolation means are An offset detecting means to be obtained, and an arithmetic means for substituting each offset of the A-phase and B-phase sine waves obtained by the offset detecting means into the following formula 8 to obtain an interpolation error E due to the offset. Characteristic interpolation error estimation device. [Equation 7] A-phase sine wave = As ₁ sin (2πx / λ) + Vs B-phase sine wave = Ac ₁ cos (2πx / λ) + Vc (7) [Equation 8] Interpolation error E = (λ / 2π) {(−Vs / As ₁ ) cosu + (Vc / Ac ₁ ) sinu} (8) where λ: period of the sine wave u: 2πx / λ x: position of the encoder As ₁ , Ac ₁ : the above A Amplitudes Vs and Vc of phase and B phase sine waves: Offsets of phase A and B phase sine waves obtained by the offset detecting means 5. The interpolation error estimation device according to claim 4, wherein the A-phase and B-phase sine waves input from the encoder to the interpolation means include offset and amplitude ratio errors, and a sine wave including the errors. Is expressed by the following formula 9, an amplitude ratio detecting means for obtaining an amplitude ratio of the A-phase and B-phase sine waves input from the encoder to the interpolating means is provided, and the computing means is obtained by the offset detecting means. The respective offsets of the A-phase and B-phase sine waves thus obtained, and the amplitude ratio obtained by the amplitude ratio detecting means are substituted into the following formula 10 to obtain an interpolation error E due to the offset and the amplitude ratio. Interpolation error estimation device. [Equation 9] A-phase sine wave = As ₁ sin (2πx / λ) + Vs B-phase sine wave = Ac ₁ cos (2πx / λ) + Vc (9) [Equation 10] Interpolation error E = (λ / 2π) _{{(-Vs / As 1) cosu} + (Vc / Ac 1) sinu + (Ac 1 / As 1 -1) sinucosu} ... (10) where, lambda: the period of the sine wave u: 2πx / λ x: the position As ₁ of the encoder, Ac _1: each amplitude Vs of the a-phase and B-phase sine wave, Vc: wherein each offset of the offset a-phase obtained by the detection means and the B-phase sine wave Ac ₁ / As _1: the amplitude Amplitude ratio obtained by the ratio detection means 6. The interpolation error estimation device according to claim 4, wherein the A-phase and B-phase sine waves input from the encoder to the interpolation means include offset and phase difference errors, and a sine wave including the errors. Is represented by the following formula 11, the phase difference detection means for calculating the phase difference between the A-phase and B-phase sine waves input from the encoder to the interpolation means is provided, and the calculation means is calculated by the offset detection means. The respective offsets of the A-phase and B-phase sine waves thus obtained and the phase difference obtained by the phase difference detecting means are substituted into the following formula 12, and an interpolation error E due to the offset and the phase difference is obtained. Interpolation error estimation device. [Equation 11] A-phase sine wave = As ₁ sin (2πx / λ) + Vs B-phase sine wave = Ac ₁ cos (2πx / λ + ε) + Vc (11) [Equation 12] Interpolation error E = (λ / 2π) {(−Vs / As ₁ ) cosu + (Vc / Ac ₁ ) sinu −εsin ² u} (12) where λ: period of the sine wave u: 2πx / λ x: positions of the encoder As ₁ , Ac ₁ : Amplitudes Vs and Vc of the A-phase and B-phase sine waves: Offsets of the A-phase and B-phase sine waves obtained by the offset detecting means ε: Phase differences obtained by the phase difference detecting means 7. A correction data generation means for generating correction data for each position of the encoder based on the interpolation error E obtained by the interpolation error estimation device according to claim 4. An interpolation error correction device comprising: an adjusting unit that corrects an output of the interpolation unit with the correction data generated by the correction data generating unit. 8. The interpolation error correction device according to claim 7, wherein the correction data generation unit sequentially generates correction data at each position of the encoder, and the adjustment unit sequentially outputs from the correction data generation unit. An interpolating error correcting apparatus for correcting post-interpolation data sequentially output from the interpolating means with the corrected data. 9. The interpolation error correction device according to claim 7, further comprising a look-up table memory that stores the correction data from the correction data generation unit in a look-up table, and the adjustment unit includes the look-up table memory. An interpolation error correction device for correcting post-interpolation data sequentially output from the interpolation means with the correction data stored in. 10. The interpolation error correction device according to claim 9, wherein the lookup table is newly created or updated in real time. 11. The interpolation error correction device according to claim 9, wherein the lookup table is newly created or updated in advance.