CN108303130B - Calibration Method of Grating Moiré Signal Subdivision Error Based on Laser Interference Principle - Google Patents

Abstract

The invention discloses a calibration method for the subdivision error of a grating Moiré signal, which solves the problem of incomplete calibration of the subdivision error at present. The present invention uses a laser interferometer to measure the initial displacement l ₀ ; controls the grating to move with a step distance of h, and sets the displacement corresponding to a subdivision value as X; records the jump of each subdivision value of the n-rate subdivision circuit within a grating distance displacement The displacement measurement result l _i of the variable time laser interferometer; the displacement measurement result difference l _i -l ₀ of the laser interferometer is compared with the grating subdivision displacement measurement value iX as a reference value, and the displacement deviation of each subdivision value is obtained Δ _i ; perform data processing on the displacement deviation of each subdivision value within a grating pitch to obtain the subdivision error; repeat the measurement, and use the average value of multiple groups as the subdivision error of the grating moire signal. The method of the invention has short calibration time, simple data processing and high test efficiency.

Description

Calibration Method of Grating Moiré Signal Subdivision Error Based on Laser Interference Principle

technical field

The invention relates to the technical field of grating moire fringe subdivision, in particular to a method for calibrating the subdivision error of grating moiré signals.

Background technique

Grating measurement technology has always been an important part of the measurement field. The signal processing method of subdividing the grating moire signal to improve the measurement resolution and accuracy is widely used in the field of high-precision measurement. The error introduced by grating moire signal subdivision during grating measurement needs to be evaluated.

At present, the calibration method of subdivision error in China is not perfect. Most of the studies only consider part of the error caused by the non-standard output signal of the grating, but do not include the error introduced by the subdivision algorithm and the realization of the subdivision function. For example, in the invention patent "Detection Device for Subdivision Error of Photoelectric Shaft Angle Encoder" (Patent Application No. 200910066979.1), a device for detecting encoder subdivision error is proposed. Two-way orthogonal precision code signal, calculate the waveform parameters and compare with the standard sine and cosine signal to get the subdivision error. This method considers that the non-standard output signal caused by factors such as code disc scribing, eccentricity, and adjustment process is the main source of error, and the result obtained by analyzing the non-standard signal is regarded as the subdivision error. The errors generated in other links are discussed, so the accurate calibration of the subdivision error has not been achieved.

SUMMARY OF THE INVENTION

In order to solve the problem of incomplete calibration of the subdivision error of the grating moiré signal at present, the invention proposes a calibration method of the subdivision error of the grating moire signal based on the principle of laser interference.

The present invention includes the following steps:

Step 1. Install the measuring device correctly, and connect the grating moire signal to the n-magnification subdivision circuit.

Step 2. The subdivision circuit is reset, and the raster subdivision output is adjusted to zero.

Step 3. Record the displacement measurement result l ₀ of the laser interferometer at the zero point position.

Step 4. Use the displacement generating device to control the grating to perform continuous displacement movement with a step distance h, h<<X.

Step 5. Within one grating pitch, record the displacement measurement result l _i (i=1,2...,n) of the laser interferometer at each subdivision value transition time of the n-magnification subdivision circuit.

Step 6: Calculate the actual displacement L _i =l _i -l ₀ corresponding to each subdivision value according to the recorded data.

Step 7: Calculate the displacement deviation corresponding to each subdivision value.

Step 8. Obtain the subdivision error value from the mean square value of the displacement deviation of each subdivision value

Step 9. Repeat steps 1-8 to obtain multiple sets of subdivision error values, and use the average value of the multiple sets of subdivision error values as the subdivision error of the grating moire signal.

The beneficial effect of the invention is that a subdivision error calibration method is established to obtain the subdivision error of the grating moire signal, so as to facilitate the evaluation of the subdivision error of the grating moire signal.

Description of drawings

1 is a schematic diagram of a grating ranging subdivision error calibration device based on the principle of laser interference;

FIG. 2 is a schematic diagram of a grating angle measurement subdivision error calibration device based on the principle of laser interference.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings.

Figure 1 is a schematic diagram of a grating ranging subdivision error calibration device based on the principle of laser interference. The calibration principle is as follows:

重复测量可得多组细分误差值，采用平均值作为光栅莫尔信号的细分误差。Fix the reflecting mirror on one side of the moving part of the grating ruler, so that its reflecting surface is perpendicular to the moving direction, as shown in position 1 in Figure 1. Adjust the position of the laser interferometer so that its optical path is perpendicular to the mirror surface. The displacement is measured with a laser interferometer, and when the mirror is at the starting position (position 1), the displacement measured by the laser interferometer is l ₀ . The grating performs continuous displacement movement with a step distance h. When the subdivision value jumps for the first time, the moving part moves to position 2. At this time, the distance measured by the laser interferometer is l ₁ , from which the actual moving distance of the moving part can be obtained. is L ₁ =l ₁ -l ₀ . Comparing it with the displacement X corresponding to one subdivision value, the displacement deviation Δ ₁ =L ₁ -X of the first subdivision value can be obtained. The actual grating displacement l ₁ , l ₂ , l ₃ ...... l _n corresponding to the transition time of each subdivision value within one grating pitch is sequentially recorded. Similarly, the displacement deviation Δ _i =L _i -iX of each subdivision value is calculated. The subdivision error is obtained from the mean square value of the displacement deviation of each subdivision value

Repeated measurements can be multiple sets of subdivision error values, and the average value is used as the subdivision error of the grating moiré signal.

Therefore, the laser interferometer can be used to measure the moving distance of the moving part of the grating ruler when the subdivision system changes by one subdivision value, and use it as a reference value to compare and analyze the displacement measurement value corresponding to a subdivision value, and then the grating can be obtained. Moiré signal subdivision error.

FIG. 2 is a schematic diagram of a grating angle measurement subdivision error calibration device based on the principle of laser interference. The calibration principle is as follows:

将其与一个细分值对应旋转角θ′进行对比可得第一个细分值的位移偏差Δ₁＝θ₁-θ′。依次记录一个栅距内每个细分值跳变时刻对应的光栅实际位移l₁,l₂,l₃......l_n。同理计算每个细分值的位移偏差Δ_i＝θ_i-iθ′。由各个细分值的位移偏差均方值得到细分误差

重复测量可得多组细分误差值，采用平均值作为光栅莫尔信号的细分误差。Fix the mirror on one side of the turntable so that its reflective surface is on the extension line connecting the contact point and the center of the code disc, as shown in position 1 in Figure 2. Adjust the position of the laser interferometer so that its optical path is perpendicular to the mirror surface. Measure distance with a laser interferometer. When the mirror is at the starting position (position 1), record the current measured value of the laser interferometer as l ₀ . The grating performs continuous displacement movement with a step distance h. When the subdivision value jumps for the first time, the moving part moves to position 2. At this time, the distance measured by the laser interferometer is l ₁ , from which the actual moving distance of the moving part can be obtained. For L ₁ =l ₁ -l ₀ , the rotation angle is obtained by calculation

Comparing it with the rotation angle θ' corresponding to a subdivision value, the displacement deviation Δ ₁ =θ ₁ -θ' of the first subdivision value can be obtained. The actual grating displacement l ₁ , l ₂ , l ₃ ...... l _n corresponding to the transition time of each subdivision value within one grating pitch is sequentially recorded. Similarly, the displacement deviation Δ _i =θ _i -iθ' of each subdivision value is calculated. The subdivision error is obtained from the mean square value of the displacement deviation of each subdivision value

Repeated measurements can be multiple sets of subdivision error values, and the average value is used as the subdivision error of the grating moiré signal.

Therefore, when the radius R of the code disc is known, the laser interferometer can be used to measure the angle value actually rotated by the grating disc when the subdivision system changes a subdivision value, and use it as a standard value corresponding to a subdivision value The angle value of the grating can be compared and analyzed to obtain the subdivision error of the grating Moiré signal.

It is worth pointing out that subdivision error is common in all subdivision systems. As long as it is based on the basic technical concept of the present invention, the embodiments that those of ordinary skill in the art can think of without creative work all belong to the protection scope of the present invention.

Claims (1)

1. a grating moire signal subdivision error calibration method based on the principle of laser interference, is characterized in that the method comprises the following steps: Step 1, install the measuring device, connect the grating moire signal to the n-magnification subdivision circuit, and the grating moire signal comes from the grating ruler or the grating disc; The measuring device corresponding to the grating ruler includes a reflecting mirror, and the reflecting mirror is fixed on one side of the moving part of the grating ruler, so that the reflecting surface is perpendicular to the moving direction, and the position of the laser interferometer is adjusted so that the optical path of the laser interferometer is perpendicular to the reflecting mirror surface; The measuring device corresponding to the grating disk includes a reflector, the reflector is fixed on one side of the turntable, so that the reflecting surface is on the extension line connecting the contact point and the center of the code disk, and the position of the laser interferometer is adjusted to make the laser interferometer. The optical path is perpendicular to the mirror surface; Step 2. Reset the subdivision circuit and zero-adjust the grating subdivision output; Step 3, record the displacement measurement result l ₀ of the laser interferometer at the zero point position; Step 4. Use the displacement generating device to control the grating to perform continuous displacement movement with a step distance h, h<<X, X is a subdivision value corresponding to the displacement; Step 5. Within one grating pitch, record the displacement measurement result l _i of the laser interferometer at each subdivision value transition time of the n-fold subdivision circuit, i=1,2...,n; Step 6: Calculate the actual displacement L _i =l _i -l ₀ corresponding to each subdivision value through the recorded data; Step 7. Calculate the displacement deviation corresponding to each subdivision value, specifically: When the calibration object is a grating ruler, compare L ₁ with the displacement X corresponding to a subdivision value, and obtain the displacement deviation of the first subdivision value Δ ₁ =L ₁ -X; record each subdivision in a grating pitch in turn Calculate the actual displacement l ₁ , l ₂ , l ₃ ...... l _n of the grating corresponding to the value jump moment, and calculate the displacement deviation Δ _i =L _i -iX of each subdivision value; When the calibration object is a raster disk, calculate the rotation angle when the subdivision value jumps for the first time

Among them, R is the radius of the code disc. Comparing θ ₁ with the rotation angle θ' corresponding to a subdivision value, the displacement deviation of the first subdivision value Δ ₁ =θ ₁ -θ' is obtained; record each grid pitch in turn. Calculate the actual displacement l ₁ , l ₂ , l ₃ ...... l _n of the grating corresponding to the subdivision value transition moment, and calculate the displacement deviation of each subdivision value Δ _i =θ _i -iθ′; Step 8. Obtain the subdivision error value from the mean square value of the displacement deviation of each subdivision value

Step 9. Repeat steps 1-8 to obtain multiple sets of subdivision error values, and use the average value of the multiple sets of subdivision error values as the subdivision error of the grating moire signal.

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