CN108106646B - Reflection type absolute value photoelectric encoder - Google Patents
Reflection type absolute value photoelectric encoder Download PDFInfo
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- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
- G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
- G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
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Abstract
A reflection type absolute value photoelectric encoder mainly comprises a support, a reflection type coded disc, a circuit board and a shell; the reflective code disc comprises two incremental code channels; the number of the reflective stripes of the outer ring code channel of the reflective code disc is 2nThe number of the reflective stripes of the inner ring code track is 2n-1 group; the circuit board used by the encoder comprises a reading head, the reading head comprises a diffuse reflection light source, a slit disc and a photoelectric detector, and sine and cosine signals output by the photoelectric detector can be used for calculating a phase angle through a processing circuit and a microprocessor
、
、
M-bit binary code signal, the microprocessor will transmit the m-bit binary code signal
And m bit binary code signal
Error correction and combination are carried out, and the absolute mechanical angle with n + m bit resolution ratio can be output
. The absolute position output of the reflective encoder is realized, and the reflective coded disc is only composed of two circles of coded discs, so that the coded disc is small in size; the light source of the reading head is a diffuse reflection light source and is positioned between the two code channels, so that the reading head is easy to assemble.
Description
Technical Field
The invention belongs to the technical field of optical, mechanical and electrical integration, and particularly relates to a reflective absolute value encoder.
Background
The photoelectric encoder is mainly based on the moire fringe principle, the moire fringes are formed by overlapping a coded disc and a slit disc in the traditional transmission type photoelectric encoder, the transmission type photoelectric signal acquired by adopting the transmission type photoelectric encoder is required to be reduced along with the reduction of the width of a coded disc reticle, and the square reduction of the gap between the coded disc and the slit disc is required, so that the assembly difficulty of the high-resolution transmission type photoelectric encoder is improved in a multiplied mode. The reflective photoelectric encoder forms moire fringes by overlapping the image of the code disc and the slit disc, so that the reflective photoelectric encoder is insensitive to the gap change of the code disc and the slit disc and can use diffused light for illumination. However, since the absolute value code channel of the conventional encoding method is more than ten circles, the reflection angle is not easy to control by using the reflection method to obtain the moire fringes, and the volumes of the code wheel and the slit disc are multiplied, so that the reflection-type photoelectric encoder only has the incremental application and does not have the absolute application.
Disclosure of Invention
The invention aims to solve the technical problem of providing a reflective absolute value photoelectric encoder adopting double code channels aiming at the defects of the traditional reflective absolute value photoelectric encoder, and realizing the absolute position output of the reflective encoder.
The technical problem to be solved by the present invention is achieved by the following technical means. The invention relates to a reflection type absolute value photoelectric encoder, which is characterized in that: the encoder mainly comprises a support, a reflective coded disc, a circuit board and a shell; the reflective code disc comprises two incremental code channels; the number of the reflective stripes of the outer ring code channel of the reflective code disc is 2nThe number of the reflective stripes of the inner ring code track is 2n-1 group, n being a positive integer;
the circuit board used by the encoder comprises a reading head, wherein the reading head comprises a diffuse reflection light source, a slit disc and m photoelectric detectors, and m is more than or equal to n + 2; light emitted by a diffuse reflection light source in the reading head is reflected to a slit disc through a reflection type coded disc to form moire fringes, and a photoelectric detector detects the change of the moire fringes to generate an electric signal;
when the support rotates for one circle, m/2 photoelectric detectors receive the optical signals reflected by the outer ring and generate 2nOne period of sine and cosine signals, and the other m/2 photodetectors receive the light signals reflected by the inner ringAnd generate 2n-1 cycle of sine and cosine signals;
the sine and cosine signals output by the photoelectric detector can be used for obtaining a phase angle through a processing circuit and a microprocessor
、
、
The m-bit binary code signal of (a),
is the phase angle of the current period of the outer sine and cosine signal,
is the phase angle of the current period of the inner circle sine and cosine signal,
sine and cosine signal phase angles of inner and outer circles
、
A difference of (d); the microprocessor will convert the m-bit binary code signal
And m bit binary code signal
Error correction and combination are carried out, and the absolute mechanical angle with n + m bit resolution ratio can be output
。
The invention relates to a reflection type absolute value photoelectric encoder, which further adopts the preferable technical scheme that:
the reading head is provided with eight photoelectric detectors; eight photoelectric detectors detect the change of moire fringes to generate an electric signal, when the support rotates for one circle, four photoelectric detectors receive an optical signal reflected by an outer ring and generate sine and cosine signals with 64 periods, the other four photoelectric detectors receive an optical signal reflected by an inner ring and generate sine and cosine signals with 63 periods, 8-bit digital angles of the current periods of the inner ring and the outer ring are obtained through the sine and cosine signals through a processing circuit and a microprocessor, 8-bit digital signals of the absolute value position of the encoder are obtained through the difference value of the digital angles of the inner ring and the outer ring, in order to further improve the resolution of the encoder, the 8-bit digital signals of the absolute value position are used as coarse angle data, the 8-bit digital angles of the outer ring are used as fine angle data, and the microprocessor is used for data combination and error correction to obtain 14-bit digital signals of the absolute position of the encoder.
The invention relates to a reflection type absolute value photoelectric encoder, which further adopts the preferable technical scheme that: the starting points of the inner and outer circles of stripes of the reflective code disc are consistent.
The invention relates to a reflection type absolute value photoelectric encoder, which further adopts the preferable technical scheme that: the reading head is positioned above the reflective coded disc, the slit disc consists of an inner circle of slits and an outer circle of slits, and each circle of slits consists of a plurality of groups of slits; the photoelectric detectors are divided into two groups and are respectively positioned below the inner circle of slit and the outer circle of slit, the diffuse reflection light source is positioned between the two groups of photoelectric detectors, and a partition board is arranged between the diffuse reflection light source and the photoelectric detectors to prevent light from directly transmitting to the photoelectric detectors from the light source.
Compared with the prior art, the invention has the following remarkable advantages: (1) and realizing absolute position output of the reflective encoder. (2) The reflective coded disc of the encoder only consists of two circles of coded discs, and the coded discs are small in size; (3) the light source of the reading head is a diffuse reflection light source and is positioned between the two code channels, so that the reading head is easy to assemble.
Drawings
FIG. 1 is a schematic diagram of an encoder according to the present invention;
FIG. 2 is a reflective optical code wheel diagram of the present invention;
FIG. 3 is a schematic view of the reading head structure of the present invention;
FIG. 4 is a view of a slit disk of the present invention;
FIG. 5 is a schematic front view of a readhead according to this invention;
FIG. 6 is a schematic view of the light propagation in the present invention;
FIG. 7 is a graph showing the relationship between the output waveform of the photoelectric sensor and the mechanical angle in the present invention;
FIG. 8 is a conversion circuit of the present invention;
FIG. 9 is a block diagram of a 14-bit resolution combination;
FIG. 10 is a block diagram of an n + m bit resolution combination.
Detailed Description
The following further describes particular embodiments of the present invention to facilitate further understanding of the present invention by those skilled in the art, and does not constitute a limitation to the right thereof.
the circuit board 3 used by the encoder comprises a reading head 5, wherein the reading head 5 comprises a diffuse reflection light source 6, a slit disc 7 and m photoelectric detectors 8, and m is more than or equal to n + 2; light emitted by a diffuse reflection light source 6 in the reading head 5 is reflected to a slit disc 7 through a reflection type coded disc 2 to form moire fringes, and a photoelectric detector 8 detects the change of the moire fringes to generate an electric signal;
when the support 1 rotates one circle, m/2 photoelectric detectors 8 receive the light signals reflected by the outer circle and generate 2nSine and cosine signals of one period, and m/2 photodetectors 8 for receiving the light signals reflected by the inner ring and generating 2n-1 cycle of sine and cosine signals;
sine and cosine signals output by the photoelectric detector 8 pass through a processing circuitAnd the microprocessor can calculate the phase angle
、、
The m-bit binary code signal of (a),
is the phase angle of the current period of the outer sine and cosine signal,
is the phase angle of the current period of the inner circle sine and cosine signal,
is the sine and cosine signal phase angles of the inner and outer circles,
A difference of (d); the microprocessor will convert the m-bit binary code signal
And m bit binary code signal
Error correction and combination are carried out, and the absolute mechanical angle with n + m bit resolution ratio can be output
。
the circuit board 3 comprises a differential signal processing circuit, a microprocessor and a reading head 5; the reflective code wheel 2 is fixed on the support 1, the circuit board 3 is positioned above the reflective code wheel 2, and the reading head 5 is arranged on one side of the circuit board 3 close to the reflective code wheel 2, as shown in fig. 2. 64 groups of light and shade intersected reflective stripes are carved on the code track on the outer ring of the reflective coded disc 2, 63 groups of light and shade intersected reflective stripes are carved on the code track on the inner ring of the coded disc, and the starting points of the inner and outer stripes are consistent.
The circuit board 3 used by the encoder contains a read head 5, which read head 5 comprises a diffuse reflection light source 6, a slit disc 7 and 8 photo detectors 8, see fig. 3. The slit disc 7 is composed of an inner circle of slits A, B and an outer circle of slits A, B, each circle of slits is composed of four groups of slits, and the four groups of slits are arranged according to a four-split phase indication grating, as shown in fig. 4. The 8 photodetectors 8 are divided into two groups, which are respectively located below the inner circle slit A, B and the outer circle slit A, B, and the front schematic view of the reading head 5 is shown in fig. 5. The diffuse reflection light source 6 is located in the middle of the two groups of the photodetectors 8, and a partition 9 is arranged between the diffuse reflection light source 6 and the photodetectors 8 to prevent light from directly passing from the diffuse reflection light source 6 to the photodetectors 8.
When the support 1 rotates, light emitted by the diffuse reflection light source 6 of the reading head 5 is reflected to the slit disc 7 through the reflective coded disc 2 to form moire fringes with the slit disc 7, and the light propagation schematic diagram is shown in fig. 6. The two groups of photodetectors 8 respectively generate eight paths of sine and cosine changed voltage signals according to the periodic change of the moire fringes.
The relationship between the output waveform of the photodetector 8 and the mechanical angle is shown in FIG. 7, when the rotating shaft rotates
At an angle, the 4 paths of sine and cosine signals output by the outer ring photoelectric detector are respectively,
、
、
The 4 paths of sine and cosine signals output by the inner ring photoelectric detector are respectively
、
、
、
Wherein
In order to be the amplitude of the signal,U 1、U 2at a dc level. The schematic diagram of the conversion circuit of the encoder is shown in FIG. 8, 8 paths of sine and cosine signals are converted into 4 paths of sine and cosine signals after passing through a differential processing circuit, wherein the outer ring is
And
inner ring signal sum
. Because the sine and cosine signals are a function with 360 degrees as a period, the phase angle has the following relation:
in the formula:
the phase angle of the current cycle of the outer ring;
Thus, the outer ring sine and cosine signals are transformed
、
Inner ring sine and cosine signal transformation
、
。
The turns of the inner ring and the outer ring have the following relations:
the angle α the encoder has rotated is:
the schematic diagram of the encoder conversion circuit is shown in figure 8, the difference processing circuit outputs 4 paths of sine and cosine signals, and the signals are subjected to AD conversion and calculation by the microprocessor to obtain an outer ring 8-bit digital angle
And an inner ring 8-bit digital angle
By calculating the numerical angles of the inner and outer rings
、
To obtain an 8-bit digital signal of the encoder absolute position signal
。
To increase the resolution of the encoder, an 8-bit digital signal is applied
As coarse angle data, 8-bit digital angle
As fine angle data, a 14-bit digital angle of an encoder absolute position signal is combined by coarse and fine combining and error correction
The combined block diagram is shown in fig. 9.
Claims (3)
1. A reflective absolute value photoelectric encoder, characterized in that: the encoder mainly comprises a support, a reflective coded disc, a circuit board and a shell; the reflective code disc comprises two incremental code channels; the number of the reflective stripes of the outer ring code channel of the reflective code disc is 2nThe number of the reflective stripes of the inner ring code track is 2n-1 group, n being a positive integer;
the circuit board used by the encoder comprises a reading head, wherein the reading head comprises a diffuse reflection light source, a slit disc and m photoelectric detectors, and m is more than or equal to n + 2; light emitted by a diffuse reflection light source in the reading head is reflected to a slit disc through a reflection type coded disc to form moire fringes, and a photoelectric detector detects the change of the moire fringes to generate an electric signal;
when the support rotates for one circle, m/2 photoelectric detectors receive the optical signals reflected by the outer ring and generate 2nOne period of sine and cosine signals, and the other m/2 photodetectors receive the light signals reflected by the inner ring and generate 2n-1 cycle of sine and cosine signals;
the sine and cosine signals output by the photoelectric detector can be processed by the processing circuit and the microprocessor to obtain a phase angle theta1、θ2、θ3Of m-bit binary code signals, theta1Is the phase angle, theta, of the outer ring sine and cosine signal in the current period2Is the phase angle, theta, of the current cycle of the inner sine and cosine signal3Sine and cosine signal phase angles theta of inner and outer circles1、θ2A difference of (d); the microprocessor will convert the m-bit binary code signal theta1And m bit binary code signal theta3Error correction and combination are carried out, and then the n + m bit resolution absolute mechanical angle α can be output;
the reading head is provided with eight photoelectric detectors; eight photoelectric detectors detect the change of moire fringes to generate an electric signal, when a support rotates for one circle, four photoelectric detectors receive an optical signal reflected by an outer ring and generate sine and cosine signals with 64 periods, the other four photoelectric detectors receive an optical signal reflected by an inner ring and generate sine and cosine signals with 63 periods, 8-bit digital angles of the current periods of the inner ring and the outer ring are obtained through the sine and cosine signals through a processing circuit and a microprocessor, 8-bit digital signals of the absolute value position of an encoder are obtained through the difference value of the digital angles of the inner ring and the outer ring, in order to further improve the resolution of the encoder, the 8-bit digital signals of the absolute value position are used as coarse angle data, the 8-bit digital angles of the outer ring are used as fine angle data, and the microprocessor is used for data combination and error correction to obtain 14-bit digital signals of the absolute position of the encoder;
when the rotating shaft rotates α degrees, the output 4 paths of sine and cosine signals of the outer ring photoelectric detector are respectively V1sin64α+U1、V1sin(64α+π)+U1、V1cos64α+U1、V1cos(64α+π)+U1The 4 paths of sine and cosine signals output by the inner ring photoelectric detector are respectively V2sin63α+U2、V2sin(63α+π)+U2、V2cos63α+U2、V2cos(63α+π)+U2In which V is1、V2Being the amplitude of the signal, U1、U2Is a direct current level; 8 paths of sine and cosine signals are converted into 4 paths of sine and cosine signals after passing through a differential processing circuit, wherein the outer ring is 2V1sin64 α and 2V1cos64 α, inner coil signal 2V2sin63 α and2V2cos63 α, because the sine and cosine signals are a function with 360 degrees as the period, the phase angle has the following relation:
in the formula: theta1The phase angle of the current cycle of the outer ring;
θ2the phase angle of the current period of the inner ring;
k1the number of turns of the outer ring is;
k2the number of turns of the inner ring is;
outer ring sine and cosine signal is converted into 2V1sinθ1、2V1cosθ1Inner ring sine and cosine signal conversion to 2V2sinθ2、2V2cosθ2；
The turns of the inner ring and the outer ring have the following relations:
the angle α the encoder has rotated is:
the difference processing circuit outputs 4 paths of sine and cosine signals, and the signals are subjected to AD conversion and calculation by the microprocessor to obtain an outer ring 8-bit digital angle theta1And an inner ring 8-bit digital angle theta2By calculating the inner and outer ring numerical angles theta1、θ2To obtain an 8-bit digital signal theta of the encoder absolute position signal3；
Combining an 8-bit digital signal theta3As coarse angle data, 8-bit digital angle θ1As the fine angle data, a 14-bit digital angle α of the encoder absolute position signal is combined by coarse-fine combining and error correction.
2. A reflective absolute value photoelectric encoder according to claim 1, wherein: the starting points of the inner and outer circles of stripes of the reflective code disc are consistent.
3. A reflective absolute value photoelectric encoder according to claim 1, wherein: the reading head is positioned above the reflective coded disc, the slit disc consists of an inner circle of slits and an outer circle of slits, and each circle of slits consists of a plurality of groups of slits; the photoelectric detectors are divided into two groups and are respectively positioned below the inner circle of slit and the outer circle of slit, the diffuse reflection light source is positioned between the two groups of photoelectric detectors, and a partition board is arranged between the diffuse reflection light source and the photoelectric detectors to prevent light from directly transmitting to the photoelectric detectors from the light source.
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| CN108827351B (en) * | 2018-06-28 | 2021-07-06 | 广东工业大学 | Rotary encoder and measuring method thereof |
| CN108731710A (en) * | 2018-07-11 | 2018-11-02 | 上海市雷智电机有限公司 | A kind of encoder |
| CN110864711B (en) * | 2018-08-27 | 2022-03-11 | 台达电子工业股份有限公司 | Encoder and position detection method thereof |
| CN109099944B (en) * | 2018-09-21 | 2024-05-24 | 上海市雷智电机有限公司 | Encoder for stepping motor and initial phase identification method of stepping motor |
| CN109217743B (en) * | 2018-11-23 | 2020-12-22 | 成都芯进电子有限公司 | Output voltage control system and method for absolute magnetic angle encoder |
| CN110736486B (en) * | 2019-09-27 | 2022-03-15 | 连云港杰瑞电子有限公司 | Compact dual-redundancy absolute encoder |
| CN110940361A (en) * | 2019-12-04 | 2020-03-31 | 北京科技大学 | Magnetic sensitive multi-circle absolute value encoder |
| CN114485745A (en) * | 2022-02-11 | 2022-05-13 | 靖江市宇其光电科技有限公司 | Small-size high reliability blue light reflective encoder |
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| CN1020956C (en) * | 1990-08-25 | 1993-05-26 | 中国科学院长春光学精密机械研究所 | Absolute type shaft-position encoder and its designing method |
| CN1027397C (en) * | 1991-03-20 | 1995-01-11 | 中国科学院长春光学精密机械研究所 | Photoelectric shaft encoder and signal extraction method |
| US5774074A (en) * | 1997-01-21 | 1998-06-30 | Hewlett-Packard Company | Multi-track position encoder system |
| GB0127491D0 (en) * | 2001-11-16 | 2002-01-09 | Trw Lucas Varity Electric | Angular position sensor |
| KR101184129B1 (en) * | 2008-06-05 | 2012-09-18 | 미쓰비시덴키 가부시키가이샤 | Optical encoder |
| CN102261927A (en) * | 2011-04-28 | 2011-11-30 | 南京中科天文仪器有限公司 | Single code channel grating encoder for outputting monocyclic position type sine wave signal |
| CN102564308B (en) * | 2011-12-29 | 2013-09-25 | 中国科学院长春光学精密机械与物理研究所 | Device for detecting eccentricity of interference type high-density round grating |
| JP5999584B2 (en) * | 2013-11-05 | 2016-09-28 | 株式会社安川電機 | Encoder, motor with encoder, servo system |
| CN105627921B (en) * | 2015-12-18 | 2018-08-21 | 佛山轻子精密测控技术有限公司 | A kind of the subdivision acquisition system and its measurement method of absolute type encoder |
| CN106767962A (en) * | 2016-12-16 | 2017-05-31 | 凌子龙 | Differential type photoelectric encoder and position judging method |
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