High overfill encoder

Abstract

The application provides a high-calibration-amount encoder, comprising a scale grating, an indicating grating, a photoelectric receiver and a light source; the scale grating is provided with a vernier code channel group for single-turn counting and a Gray code channel group for multi-turn counting, and the Gray code channel group comprises at least two Gray code channels; the application increases the number of Gray code channels to increase the calibration amount of the encoder, thereby improving the fault tolerance of the encoder and ensuring that the encoder can normally work under different working conditions; and the application also adopts a blue light source, increases the effective light-emitting radius of the light source, improves the light-emitting efficiency and improves the reliability of the encoder.

Description

Technical Field

[0001] This invention relates to the field of encoders, and particularly to an encoder with high calibration margin. Background Technology

[0002] An optical encoder is a digital inspection device integrating optics, mechanics, and electronics. It is a sensor that converts the mechanical or geometric displacement input to a shaft into pulse or digital quantities through a photoelectric conversion circuit. It is mainly used for speed or position detection. It has advantages such as high accuracy, fast response, and stable and reliable performance.

[0003] Photoelectric encoders can use vernier encoding, which is based on the principle of vernier calipers. That is, three tracks are engraved on the scale grating, which are marked as N (vernier track), M (main track) and S (segment track), and the tracks are staggered by a certain phase.

[0004] When using vernier encoding, theoretically the zero positions of the three code tracks M, S, and N are at the same fixed position. During the rotation of the scale grating, the zero positions of the three code tracks start and end together. However, due to the existence of part processing errors, installation errors, and scale grating deformation caused by temperature, the three code tracks cannot be guaranteed to be at the same position. Therefore, it is necessary to perform synchronous calculation on the three code tracks. The synchronous calculation process is the calibration process. The maximum allowable range for calibration is the calibration tolerance. As the number of bits in the encoder increases, the range of calibration tolerance will decrease. The larger the calibration margin, the more reliable the encoder performance.

[0005] Therefore, with the increasing market demand for miniaturized and high-precision encoders, improving the calibration margin range is a technical problem that needs to be solved by those skilled in the art.

[0006] Existing encoders based on the transmission principle use infrared or red light as their LED light source. These light sources have a long emission wavelength and low luminous efficiency. When the width of the window etched on the grating is less than 0.025 mm, the signal will be unstable due to the low photoelectric conversion efficiency.

[0007] Existing small-packaged LEDs use tubes with a standard size of φ4.7mm. When the internal light-emitting chip emits infrared or red light, the effective radius of the emitted light is only φ2.9mm to 3mm, which limits the area of ​​the effective grating area.

[0008] Existing high-resolution optical systems all rely on dual-emission systems and large-package LEDs (φ6mm, φ7mm, etc.), which results in larger product sizes and makes miniaturization impossible. Summary of the Invention

[0009] To solve the above problems, the present invention provides a high calibration margin encoder.

[0010] To achieve the above objectives, the present invention adopts the following specific technical solution:

[0011] A high calibration margin encoder includes: a scale grating, an indicator grating, a photoelectric receiver, and a light source; the scale grating is provided with a vernier code track group for single-turn counting and a Gray code track group for multi-turn counting;

[0012] The vernier code track group includes M-track, N-track, and S-track. Each of the M-track, N-track, and S-track has multiple light-transmitting areas regularly distributed along the code track. The Gray code track group includes at least two Gray code tracks, each of which consists of regularly distributed alternating light and dark stripes. The indicator grating has at least five code tracks corresponding to the vernier code track group and the Gray code track group. Each code track of the indicator grating has multiple light-transmitting areas regularly distributed along the code track.

[0013] The calibration margin of an encoder is inversely proportional to the number of bits used by the N-track in the binary signal output by the encoder. By increasing the number of Gray tracks, the number of bits used by the N-track in the binary signal output by the encoder can be reduced, thereby increasing the calibration margin of the encoder.

[0014] Preferably, the light source is a blue light source.

[0015] Preferably, the N code channel, M code channel, and S code channel are arranged in order from the outside to the inside, and at least two Gray code channels are respectively placed between the M code channel and the N code channel, between the M code channel and the S code channel, outside the N code channel, or inside the S code channel.

[0016] Preferably, the geometric centers of the M-track, N-track, S-track, and all Gray tracks on the scale grating coincide; the geometric centers of all tracks on the indicator grating coincide.

[0017] Preferably, the geometric center of the smallest circumcircle of all the code tracks of the indicator grating coincides with the geometric center of the M code track.

[0018] Preferably, the diameter of the smallest circumscribed circle is smaller than the effective luminous diameter of the light source.

[0019] Preferably, the radial dimension of each code track of the indicator grating is smaller than the radial dimension of the corresponding code track on the scale grating.

[0020] Preferably, it also includes an optical system for converting light emitted from the light source into parallel light, the optical system being positioned between the light source and the scale grating.

[0021] The present invention can achieve the following technical effects:

[0022] (1) By increasing the number of Gray code tracks, the calibration margin of the encoder is increased, thereby improving the fault tolerance of the encoder and ensuring that the encoder can work normally under different working conditions;

[0023] (2) Blue light source is used to increase the effective light-emitting radius of the light source, improve the light-emitting efficiency, and improve the reliability of the encoder. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of a high calibration margin encoder according to an embodiment of the present invention;

[0025] Figure 2 This is a schematic diagram of the scale grating according to an embodiment of the present invention;

[0026] Figure 3 This is a schematic diagram of the structure of the indicator grating according to an embodiment of the present invention;

[0027] Figure 4 This is a schematic diagram of the structure of a photoelectric receiver according to an embodiment of the present invention.

[0028] The reference numerals in the accompanying drawings include: scale grating 1, indicator grating 2, photodetector 3, light source 4, rotating shaft 5, M-channel 101, N-channel 102, S-channel 103, first Gray code channel 104, second Gray code channel 105, third Gray code channel 106, fourth Gray code channel 107, indicator grating M-channel 201, indicator grating N-channel 202, indicator grating S-channel 203, indicator grating first Gray code channel 204, and indicator grating second Gray code channel 205. 05. Third Gray code channel of indicator grating 206. Fourth Gray code channel of indicator grating 207. M code channel optical signal receiving window 301. N code channel optical signal receiving window 302. S code channel optical signal receiving window 303. First Gray code channel optical signal receiving window 304. Second Gray code channel optical signal receiving window 305. Third Gray code channel optical signal receiving window 306. Fourth Gray code channel optical signal receiving window 307. Minimum circumscribed circle 6. Effective emitting diameter 7. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not constitute a limitation thereof.

[0030] like Figure 1 As shown, the high calibration margin encoder provided in this embodiment of the invention includes: a scale grating 1, an indicator grating 2, a photoelectric receiver 3, and a light source 4; the scale grating 1 is provided with a vernier code track group for single-turn counting and a Gray code track group for multi-turn counting;

[0031] The light emitted by the light source 4 passes through the light-transmitting area of ​​the scale grating 1 and the light-transmitting area of ​​the indicator grating 2 in sequence and is received by the photoelectric receiver 3. After amplification, shaping, filtering and other processing, it is converted into an electrical signal for output. The rotation angle of the encoder-mounted shaft 5 is obtained according to the output electrical signal.

[0032] like Figure 3 As shown, the lower surface of the photodetector 3 is provided with multiple optical signal receiving windows, which correspond to the vernier code channel group and the Gray code channel group, respectively, including M code channel optical signal receiving window 301, N code channel optical signal receiving window 302, S code channel optical signal receiving window 303, first Gray code channel optical signal receiving window 304, second Gray code channel optical signal receiving window 305, third Gray code channel optical signal receiving window 306, and fourth Gray code channel optical signal receiving window 307.

[0033] When the scale grating 1 rotates, the occlusion of the light source 4 by the vernier code track group and the Gray code track group changes, cutting the incident light signal into signals with varying intensity, causing the intensity of the light received by the photodetector 3 to change, and thus causing the electrical signal output by the photodetector 3 to change.

[0034] like Figure 2 As shown, the vernier code track group includes M code track 101, N code track 102, and S code track 103. Each of the M code track 101, N code track 102, and S code track 103 has multiple light-transmitting areas regularly distributed along the code track, making each of the M code track 101, N code track 102, and S code track 103 a stripe of alternating light and dark. The light-transmitting areas are light stripes, and the opaque areas are dark stripes. The Gray code track group includes at least two Gray code tracks, each of which is a stripe of alternating light and dark that is regularly distributed. In this embodiment, the Gray code track group includes four Gray code tracks, namely the first Gray code track 104, the second Gray code track 105, the third Gray code track 106, and the fourth Gray code track 107.

[0035] The indicator grating 2 has at least five code tracks corresponding to the vernier code track group and the Gray code track group. Each code track of the indicator grating 2 is engraved with multiple light-transmitting areas regularly distributed along the code track, so that each code track of the indicator grating 2 is also a stripe of alternating light and dark. The light-transmitting areas are light stripes, and the opaque areas are dark stripes.

[0036] like Figure 3 As shown, in this embodiment, the indicator grating 2 has seven code channels, namely indicator grating M code channel 201, indicator grating N code channel 202, indicator grating S code channel 203, indicator grating first Gray code channel 204, indicator grating second Gray code channel 205, indicator grating third Gray code channel 206, and indicator grating fourth Gray code channel 207.

[0037] The calibration margin of the encoder is inversely proportional to the number of bits used by the N-track 102 in the binary signal output by the encoder. That is, the fewer bits used by the N-track 102 in the binary signal output by the encoder, the larger the calibration margin of the encoder. The calibration margin of the encoder can be increased by increasing the number of Gray tracks to reduce the number of bits used by the N-track 102 in the binary signal output by the encoder.

[0038] When the encoder output is obtained by performing vernier operations based on M track 101, N track 102 and S track 103, the encoder is an absolute encoder. When the encoder output is obtained based on any one of M track 101, N track 102 and S track 103, the encoder is an incremental encoder.

[0039] In one embodiment of the present invention, the light source 4 is a blue light source. Compared with infrared light or red light, the luminous efficiency of the blue light source is increased by 10-15%, and the luminous radius is increased to 3.3-3.4 mm.

[0040] In one embodiment of the present invention, N code track 102, M code track 101 and S code track 103 are arranged sequentially from the outside to the inside, and at least two Gray code tracks are placed between M code track 101 and N code track 102, between M code track 101 and S code track 103, outside of N code track 102 or inside of S code track 103; the position of the Gray code track has no effect on the function of the Gray code and can be set according to the actual situation of the scale grating 1.

[0041] In one embodiment of the present invention, the geometric centers of the M-track 101, N-track 102, S-track 103 and all Gray tracks on the scale grating 1 coincide, indicating that the geometric centers of all tracks on the indicator grating 2 coincide; each track is a circular track, and the geometric center of the circular track is the center of a circle, that is, the centers of all tracks on the scale grating 1 coincide, indicating that the centers of all tracks on the indicator grating 2 coincide.

[0042] In one embodiment of the present invention, the geometric center of the smallest circumcircle 6 of all code tracks of the indicator grating 2 coincides with the geometric center of the M code track 101, that is, the center of all code tracks on the scale grating 1 coincides with the center of all code tracks on the indicator grating 2.

[0043] In one embodiment of the present invention, the diameter of the smallest circumcircle 6 is smaller than the effective light-emitting diameter 7 of the light source 4; ensuring that all code tracks on the indicator grating 2 are within the illumination range of the light source 4.

[0044] In one embodiment of the present invention, the radial dimension of each code track of the indicator grating 2 is smaller than the radial dimension of the corresponding code track on the scale grating 1.

[0045] In one embodiment of the present invention, an optical system for converting light emitted from the light source 4 into parallel light is further included. The optical system is placed between the light source 4 and the scale grating 1. By converting the light into parallel light for uniform light distribution, the light intensity of the light illuminating the scale grating 1 is made uniform.

[0046] The advantages of the present invention will be described in detail below:

[0047] The encoder calibration value is calculated using a vernier based on the phase deviation of S-track 103 and N-track 102 relative to M-track 101. The larger the phase deviation of S-track 103 and N-track 102 relative to M-track 101, the larger the calibration value. Under the premise that the overall structure of the encoder remains unchanged, the material expands and contracts with temperature changes, that is, the relative position of the scale grating 1 and the photoelectric receiver 3 shifts, resulting in an increase in the encoder calibration value. When the calibration value is greater than or equal to the calibration tolerance, the encoder alarms and cannot operate normally. Therefore, increasing the encoder calibration margin can improve the encoder's temperature adaptability.

[0048] When the encoder counts a single turn, the N track 102 and S track 103 need to be synchronized with the M track 101. Therefore, synchronization bits need to be set. The more synchronization bits there are, the easier it is to synchronize. However, the encoder accuracy decreases as the number of synchronization bits increases. In this invention, the number of synchronization bits is set to c = 4.

[0049] The required number of physical strokes for M-channel 101 is 2. a That is, the physical number of bits output by the encoder is 'a' bits, and the number of pulses in channel M101 within each electrical cycle is 2. n+s The pulse count for channel N, 102 is 2. n+s -1, the pulse count for S-code channel 103 is 2. n+s -2 s Based on the encoder principle, equation (1) can be obtained:

[0050] a = n + s + b (1)

[0051] Where n is the number of bits used in the N code channel 102 of the output electrical signal, s is the number of bits used in the S code channel 103 of the output electrical signal, and b is the number of Gray code channels included in the Gray code channel group; since the bits used in the N code channel 102 are the high bits of the encoder, in order to reduce the probability of encoder reading errors, n = s or n = s + 1 is usually used.

[0052] The formula for calculating the encoder calibration margin is as shown in formula (2):

[0053] K = ±7(360° / 2) n+c (2)

[0054] Where K is the encoder's calibration margin;

[0055] As can be seen from equations (1) and (2), when the number of markings of M-track 101, N-track 102 and S-track 103 remains unchanged, increasing the number of Gray tracks can effectively increase the calibration margin of the encoder.

[0056] This invention can be applied to the development of high-resolution, high-precision encoders. In one embodiment of this invention, the number of markings on the M-track 101 of the scale grating 1 is 2048P / r, that is, the number of bits of the electrical signal output by the encoder is a = 11 bits.

[0057] Choosing n = s = 4, the number of pulses in M-code channel 101 is 2 in each electrical cycle of scale grating 1. 4+4 The pulse count for channel N, 102 is 2. 4+4 -1, the pulse counts for S-code channel 103 are 2 respectively. 4+4 -2 4 According to the calculation, the number of Gray code channels is b = 3.

[0058] The encoder calibration margin K = ±9.84° is calculated to be twice the calibration margin of current transmissive encoders.

[0059] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0060] Although embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

[0061] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A high calibration margin encoder, characterized in that, include: The system includes a scale grating, an indicator grating, a photoelectric receiver, and a light source; the scale grating is provided with a vernier code track group for single-turn counting and a Gray code track group for multi-turn counting. The vernier code track group includes an M code track, an N code track, and an S code track. Each of the M code track, the N code track, and the S code track has multiple light-transmitting areas regularly distributed along the code track. The Gray code track group includes at least two Gray code tracks, each of which is a regularly distributed pattern of alternating light and dark stripes. The indicator grating has at least five code tracks corresponding to the vernier code track group and the Gray code track group. Each code track of the indicator grating has multiple light-transmitting areas regularly distributed along the code track. The calibration margin of the encoder is inversely proportional to the number of bits used in the binary signal output by the N-track. By increasing the number of Gray tracks, the number of bits used in the binary signal output by the N-track is reduced, thereby increasing the calibration margin of the encoder. The Gray code channel group includes four Gray code channels, namely the first Gray code channel, the second Gray code channel, the third Gray code channel, and the fourth Gray code channel; the first Gray code channel is located between the M code channel and the N code channel, the second Gray code channel is located between the M code channel and the S code channel, the third Gray code channel is located outside the N code channel, and the fourth Gray code channel is located inside the S code channel.

2. The high calibration margin encoder as described in claim 1, characterized in that, The light source is a blue light source.

3. The high calibration margin encoder as described in claim 1, characterized in that, The N-code channel, the M-code channel, and the S-code channel are arranged sequentially from the outside to the inside, and the at least two Gray code channels are respectively placed between the M-code channel and the N-code channel, between the M-code channel and the S-code channel, outside the N-code channel, or inside the S-code channel.

4. The high calibration margin encoder as described in claim 1, characterized in that, The geometric centers of the M-track, N-track, S-track, and all Gray tracks on the scale grating coincide; the geometric centers of all tracks on the indicator grating coincide.

5. The high calibration margin encoder as described in claim 1, characterized in that, The geometric center of the smallest circumcircle of all the code tracks of the indicator grating coincides with the geometric center of the M code track.

6. The high calibration margin encoder as described in claim 5, characterized in that, The diameter of the smallest circumcircle is smaller than the effective luminous diameter of the light source.

7. The high calibration margin encoder as described in claim 1, characterized in that, The radial dimension of each code track of the indicator grating is smaller than the radial dimension of the corresponding code track on the scale grating.

8. The high calibration margin encoder as described in claim 1, characterized in that, It also includes an optical system for converting the light emitted by the light source into parallel light, the optical system being positioned between the light source and the scale grating.

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