Absolute angular displacement sensor based on photoelectric coding and working method

Abstract

The invention relates to the technical field of precision measurement sensors, in particular to an absolute angular displacement sensor based on photoelectric coding and a working method, and the sensor comprises an excitation module, a sensor body, a signal processing circuit and a control module; the excitation module is used for generating an excitation signal and inputting the excitation signal into the sensor body; the sensor body is used for generating a displacement signal according to the excitation signal and generating a coding signal according to the light emitting signal; the sensor body comprises a fixed ruler and a movable ruler; the fixed ruler comprises a first base body, and at least one photoelectric sensor is further arranged between the edges of the first base body. The movable ruler comprises a second base body, the upper surface of the second base body is covered with a light absorption insulating layer, and the upper surface of the light absorption insulating layer is covered with at least one reflective coding block; the signal processing circuit is used for performing signal enhancement processing on the displacement signal and the coded signal; the control module is used for obtaining an absolute bit value according to the processed displacement signal and the coded signal; the precision is high and the size is small.

Description

Technical Field

[0001] This invention relates to the field of precision measurement sensor technology, and in particular to an absolute angular displacement sensor based on photoelectric encoding and its working method. Background Technology

[0002] High-precision absolute angular displacement sensors are widely used in precision equipment, such as precision machine tools, military weapons, automobiles, medical devices, and high-precision worktables, serving as key functional units in these devices. Using absolute sensors enables absolute displacement measurement, effectively solving the problem of data loss during power outages. Furthermore, it allows for fully closed-loop control and feedback, reducing interference from external factors such as temperature, and improving the sensor's measurement accuracy, thus broadening its application range.

[0003] However, at present, sensors mainly achieve absolute measurement by using differential or coprime methods. Although absolute measurement is achieved, there are also drawbacks.

[0004] (1) When using differential or coprime to achieve absolute positioning, two rows of sensors need to be set up. The two rows of sensors have crosstalk between them, which is not conducive to high-precision measurement. At the same time, it increases the size of the sensors, which is not conducive to miniaturization. (2) In applications with larger diameters, the difficulty of achieving absolute measurement with an angular displacement sensor will increase significantly, mainly due to positioning errors. Where L is the sensor length, and N and N-1 are the number of cycles for the two rows of sensors, respectively. The larger the diameter of the angular displacement sensor, the more cycles are required, and the more difficult it is to achieve absolute positioning. Summary of the Invention

[0005] To address the problem of large measurement errors in high-precision absolute angular displacement sensors due to mutual interference in existing technologies, this invention proposes an absolute angular displacement sensor and its working method based on photoelectric coding. By using coding, the absolute angular displacement periodic positioning is achieved. Coding positioning only requires positioning to the period value of the incremental time grating sensor, without the need for fine scribing lines. The coding method is simple, the coding scribing lines are easy to implement, the error is reduced, and the accuracy of high-precision measurement is improved.

[0006] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides an absolute angular displacement sensor based on photoelectric encoding, comprising an excitation module, a sensor body, a signal processing circuit, and a control module; The excitation module is used to generate excitation signals and input them to the sensor body; The sensor body is used to generate displacement signals based on excitation signals and to generate encoded signals based on light emission signals. The sensor body includes a fixed scale and a movable scale; The measuring device includes a first substrate (1), and an excitation electrode (1-1) is provided on the upper surface of the first substrate (1). The excitation electrode (1-1) includes 4P first electrode plates arranged at equal intervals in a circle. A sensing signal receiving ring (1-2) is provided on the outside of the excitation electrode (1-1). At least one photoelectric sensor (1-3) is also provided between the sensing signal receiving ring (1-2) and the edge of the first substrate (1). The moving ruler includes a second base (2), and a sensing electrode (2-1) is disposed on the upper surface of the second base (2). The sensing electrode (2-1) includes 2P second electrodes of the same size. A sensing signal reflection ring (2-2) is disposed on the outside of the sensing electrode (2-1). The upper surfaces of the sensing electrode (2-1) and the sensing signal reflection ring (2-2) are covered with a light-absorbing insulating layer (2-3), and the upper surface of the light-absorbing insulating layer (2-3) is covered with at least one reflective coding block (2-4). Signal processing circuitry is used to enhance displacement signals and coded signals. The control module is used to obtain the absolute position value based on the processed displacement signal and the encoded signal.

[0007] Optionally, the excitation module generates four excitation signals, and each excitation signal is 90° out of phase.

[0008] Optionally, the sensor body includes a fixed scale and a movable scale, which are installed parallel to each other with a distance of d between them.

[0009] Optionally, the 4p+1th first electrode piece along the clockwise direction of the circumference is connected to form a first group via the first excitation signal connection line, thus forming a... Excitation phase, input the first excitation signal The 4p+2 first electrode plates, arranged clockwise along the circumference, are connected to form a second group via the second excitation signal connection line, thus constituting... Excitation phase, input the second excitation signal The first electrode plate, numbered 4p+3, is connected to the third group via the third excitation signal connection line in a clockwise direction along the circumference, forming a third group. Excitation phase, input third excitation signal The 4p+4th first electrode plates, arranged clockwise along the circumference, are connected to form the fourth group via the fourth excitation signal connection line, thus forming... Excitation phase, input the fourth excitation signal p takes integer values ​​from 0 to P-1.

[0010] Optionally, the sensing signal receiving loop (1-2) has two loops.

[0011] Optionally, the size of the induction signal reflection ring (2-2) is the same as the size of the induction signal receiving ring (1-2) on the fixed scale, and they are directly opposite each other and parallel.

[0012] Optionally, the reflective coding block (2-4) uses k-1 code channels of alternating black and white stripes to perform k-bit binary reticular code encoding, with the black and white stripes corresponding to the code "0" and code "1" respectively, and each coding segment corresponding to a unique number of cycles.

[0013] Secondly, the present invention provides a method for operating an absolute angular displacement sensor based on photoelectric encoding, specifically including the following steps: A: The excitation control module on the control module generates a series of digital signals. After processing by the signal processing circuit, four excitation signals with a 90° phase difference are obtained and sent to the sensor body. Through the mutual movement between the moving scale and the fixed scale, an induced traveling wave signal is generated on the sensing electrode (2-1) on the moving scale, and a traveling wave signal is generated on the sensing signal reflection ring (2-2) and transmitted to the sensing signal receiving ring (1-2) on the fixed scale. The signal processing circuit amplifies and filters the traveling wave signal and the reference signal of the same frequency. After the traveling wave signal and the reference signal are shaped into a square wave by the zero-crossing comparator, the data is output to the control module to obtain the precise angle measurement. ; B: First, accurately position the reflective photoelectric sensor (1-3) on the ruler onto the reflective coding block (2-4); then, the light emission control module of the control module sends a light emission signal to the light emission module of the signal processing circuit. The light emission module controls the light emission part of the reflective photoelectric sensor (1-3) to emit invisible light to illuminate the reflective coding block (2-4). The reflective coding block (2-4) returns the invisible light to the receiving part of the reflective photoelectric sensor (1-3). The receiving part of the reflective photoelectric sensor (1-3) inputs the received light signal into the signal processing circuit for processing. Then, the signal processing circuit performs signal enhancement processing on the coded signal converted by the reflective photoelectric sensor, converts the processed analog signal into a digital signal through analog-to-digital conversion, and then inputs it into the control module for decoding to obtain the absolute number of cycles N; C: The absolute position is obtained by combining the precise and coarse angle measurements. In formula (1), X represents the absolute position measured; Indicates the absolute number of periods; Indicates the period width; This indicates a coarsely measured angle value; This indicates the measured angle value.

[0014] In summary, by adopting the above technical solution, the present invention has at least the following beneficial effects compared with the prior art: This invention employs an encoding method to achieve periodic positioning of absolute angular displacement. Encoded positioning only requires locating the period value of the incremental time-grid sensor, eliminating the need for fine scribe lines. The encoding method is simple, and the scribe lines are easy to implement.

[0015] The structure of the photoelectric encoder and the incremental time grating angular displacement sensor is combined. Since the thickness of the light-absorbing insulating layer and the reflective encoder line is only on the micrometer level, the size of the sensor is reduced, making it easy to achieve compactness and miniaturization.

[0016] The two different measurement methods, coarse measurement and fine measurement, do not have mutual interference between signals, and can ensure high accuracy while achieving absolute positioning.

[0017] The coding positioning error limit is relatively large, and the coarse measurement can achieve absolute positioning without affecting the high-precision measurement of the fine measurement.

[0018] Meanwhile, the precise displacement value adopts a signal reflection structure, the absolute encoding period value adopts a reflection encoding structure, all signals on the fixed scale are passive signals, and the moving scale has a single-sided cable output, which avoids wear and maintenance of the cable during the sensor's movement. Attached image description: Figure 1 This is a schematic diagram of an absolute angular displacement sensor based on photoelectric encoding according to an exemplary embodiment of the present invention.

[0019] Figure 2 This is a schematic diagram of a sensor mounting structure according to an exemplary embodiment of the present invention.

[0020] Figure 3 This is a schematic diagram of a fixed-length structure according to an exemplary embodiment of the present invention.

[0021] Figure 4 This is a schematic diagram of a movable ruler structure according to an exemplary embodiment of the present invention.

[0022] Figure 5 This is a schematic diagram illustrating the encoding setting principle according to an exemplary embodiment of the present invention.

[0023] Figure 6 This is a schematic diagram of the working circuit of an absolute angular displacement sensor based on photoelectric encoding according to an exemplary embodiment of the present invention. Detailed Implementation

[0024] The present invention will be further described in detail below with reference to embodiments and specific implementation methods. However, this should not be construed as limiting the scope of the above-described subject matter of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.

[0025] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0026] like Figure 1 As shown, the present invention provides an absolute angular displacement sensor based on photoelectric encoding, including an excitation module, a sensor body, a signal processing circuit, and a control module.

[0027] Excitation module, used to generate 4-channel phase ( Mutually, Mutually, Harmony Excitation signals with a 90° phase difference (first excitation signal) Second excitation signal Third excitation signal and the fourth excitation signal ), and input to the sensor body; The sensor body is used to generate displacement signals based on excitation signals and to generate encoded signals based on light emission signals. A signal processing circuit is used to perform signal enhancement processing on displacement signals and encoded signals, including amplification, shaping and filtering, for example, shaping the displacement signals and encoded signals into square waves through a zero-crossing comparator; The control module is used to obtain the absolute position value based on the processed displacement signal and the encoded signal.

[0028] In this embodiment, as Figure 2 As shown, the sensor body includes a fixed scale and a moving scale, which are installed parallel to each other with a spacing of d, for example, d is usually 0.4mm.

[0029] like Figure 3 As shown, the fixed size includes a first base 1, which can be circular and made of PCB or glass.

[0030] In this embodiment, an excitation electrode 1-1 is disposed on the upper surface of the first substrate 1. The excitation electrode 1-1 includes 4P first electrode plates (which can be rectangular) arranged at equal intervals in a circle. The first electrode plates can be numbered sequentially. Each first electrode plate has the same structure and can be a rectangular electrode plate with an electrode spacing of [missing information]. .

[0031] The first electrode plates can be combined to obtain four excitation phases, including Incentive phase, Incentive phase, Incentive Synergy The excitation phase. Specifically, the 4p+1th first electrode plate, moving clockwise along the circumference, is connected to form the first group via the first excitation signal connection line, constituting... Excitation phase, input the first excitation signal The 4p+2 first electrode plates, arranged clockwise along the circumference, are connected to form a second group via the second excitation signal connection line, thus constituting... Excitation phase, input the second excitation signal The first electrode plate, numbered 4p+3, is connected to the third group via the third excitation signal connection line in a clockwise direction along the circumference, forming a third group. Excitation phase, input third excitation signal The 4p+4th first electrode plates, arranged clockwise along the circumference, are connected to form the fourth group via the fourth excitation signal connection line, thus forming... Excitation phase, input the fourth excitation signal p takes integer values ​​from 0 to P-1.

[0032] The first electrode plates 4p+1, 4p+2, 4p+3, and 4p+4 are called a pair of electrodes, i.e., one cycle; then the excitation electrodes on the fixed length have a total of P cycles.

[0033] In this embodiment, two sensing signal receiving rings 1-2 are provided on the outside of the excitation electrode 1-1 (because a first sensing group and a second sensing group are provided on the moving ruler, two sensing signal receiving rings need to be provided accordingly), which can be made of a metal conductive material; at least one photoelectric sensor 1-3 is also provided between the sensing signal receiving ring 1-2 and the edge of the first substrate 1, and the photoelectric sensor is an invisible light reflective photoelectric sensor.

[0034] like Figure 4 As shown, the moving ruler includes a second base 2, and a sensing electrode 2-1 is disposed on the upper surface of the second base 2. The sensing electrode 2-1 includes 2P identical electrodes with a spacing of 2. The second electrode is a double sinusoidal shape; and the induction electrode 2-1 and the excitation electrode 1-1 on the fixed scale are directly opposite and parallel.

[0035] The second electrode combination can obtain two sensing groups, including a first sensing group and a second sensing group. Specifically, the 2m+1th second electrode in the clockwise direction along the circumference is connected to form a fifth group through the fifth signal connection line to obtain the first sensing group; the 2m+2th second electrode in the clockwise direction along the circumference is connected to form a sixth group through the sixth signal connection line to obtain the second sensing group; m takes integer values ​​from 0 to P-1.

[0036] In this embodiment, two sensing signal reflection rings 2-2 (made of conductive metal material) are provided on the outer side of the sensing electrode 2-1. The size of the sensing signal reflection rings 2-2 is the same as the size of the sensing signal receiving rings 1-2 on the fixed ruler, and they are directly opposite each other and parallel.

[0037] Since the second electrode is a differential structure, the generated induced signal is a differential signal; at the same time, since the second electrode is connected to two induced signal reflection rings 2-2 respectively, the induced signals generated on the two induced signal reflection rings 2-2 are differential signals.

[0038] The upper surfaces of the sensing electrode 2-1 and the sensing signal reflection ring 2-2 are covered with a light-absorbing insulating layer 2-3, and the upper surface of the light-absorbing insulating layer 2-3 is covered with at least one reflective coding block 2-4. Since the thickness of the light-absorbing insulating layer and the reflective coding block is only 20 micrometers, the size of the sensor is reduced, making it easy to achieve compactness and miniaturization.

[0039] In this embodiment, as Figure 5 As shown, every two second electrodes on the moving ruler constitute one cycle, with an angle of θ. Encoding is performed once per cycle, resulting in a k-bit code. A total of k bits can be encoded. One cycle. For example, taking the first second electrode as the starting point and the second second electrode as the ending point, we set it as a coding segment, which corresponds to one cycle of the electric field type grating angular displacement sensor.

[0040] A k-bit binary Gray code is used (arranged from the outside to the inside) with alternating black and white stripes of k-1 code channels. The black and white stripes correspond to codes "0" and "1" respectively. Each code segment uniquely determines the number of cycles of the time grating sensor. The black part of the code "0" is light-absorbing material, and the reflective part of the code "1" is reflective material.

[0041] In this embodiment, the encoding method adopts natural binary encoding, which is encoded according to the number of bits and consists of binary symbols "0" and "1". Each binary symbol represents one bit. The absolute position of the sensor can be known by reading the encoding on the code track.

[0042] For example, the innermost lane 1 is... Periodic white stripes and The periodic black stripes are arranged periodically and are collected and encoded by the first photoelectric sensor; the second code track is... Periodic white stripes and The periodic black stripe pattern is collected and encoded by the second photoelectric sensor; and so on, the (k-1)th code track, i.e., the outermost ring code track, is... Periodic white stripes The periodic black stripes are arranged periodically and are encoded by the (k-1)th photoelectric sensor. The (k-1)th photoelectric sensor is arranged radially on the stator, with the kth photoelectric sensor located in the (k-1)th code track, spatially lagging behind the (k-1)th photoelectric sensor. One cycle.

[0043] In this embodiment, a method for operating an absolute angular displacement sensor based on photoelectric encoding is also provided, specifically including the following steps: like Figure 6 As shown, the excitation control module on the control module (FPGA) generates a series of digital signals by looking up a table. After digital-to-analog conversion, amplification, and filtering by the signal processing circuit, four phase signals are obtained. Mutually, Mutually, Harmony Excitation signals with a 90° phase difference (first excitation signal) Second excitation signal Third excitation signal and the fourth excitation signal The signal is sent to the sensor body. Through the mutual movement between the moving and fixed scales, an induced traveling wave signal is generated on the induction electrode 2-1 of the moving scale. The induction electrode 2-1 on the moving scale is connected to the induction signal reflection ring 2-2, thus generating a traveling wave signal on the induction signal reflection ring 2-2. The induction signal receiving ring 1-2 on the fixed scale is installed parallel to and directly opposite the induction signal transmitting ring 2-2. The induction signal receiving ring 1-2 receives the traveling wave signal (i.e., the induction signal) generated by the induction electrode of the moving scale. The signal processing circuit amplifies and filters the traveling wave signal and the reference signal of the same frequency. After the traveling wave signal and the reference signal are shaped into a square wave by a zero-crossing comparator, the data is output to the control module for phase comparison processing. Then, after high-frequency phase counting (existing technology), the precise angle is obtained. .

[0044] Because of the presence of the induction signal receiving ring 1-2 and the induction signal transmitting ring 2-2, no cable connection is needed between the fixed scale and the moving scale, thus avoiding wear on the cable when the moving scale and the fixed scale move relative to each other.

[0045] In this embodiment, the reflective photoelectric sensor 1-3 on the fixed scale is first accurately positioned (both the fixed and moving scales of the sensor have an integer number of cycles, and the number of cycles of the fixed and moving scale sensors corresponds one-to-one; the photoelectric sensor only needs to be aligned with one of the cycles) onto the reflective coding block 2-4 to ensure that the pixel array of the sensor is aligned with the coding mark; then, the light emission control module of the control module (FPGA) sends a light emission signal to the light emission module of the signal processing circuit, and the light emission module controls the light emission part of the reflective photoelectric sensor 1-3 to emit invisible light to illuminate the reflective coding block 2-4. The reflective coding block 2-4 returns the invisible light to the receiving part of the reflective photoelectric sensor 1-3, thereby converting it into a coding signal. The bright area corresponds to a higher voltage, and the dark area corresponds to a lower voltage.

[0046] Then, the signal processing circuit performs signal enhancement processing on the coded signal converted by the reflective photoelectric sensor to improve the signal-to-noise ratio and ensure a clear signal. The signal enhancement includes filtering, amplification and noise reduction. The processed analog signal is converted into a digital signal by analog-to-digital conversion and then input to the control module for decoding.

[0047] Secondly, when processing digital signals, the control module needs to select a suitable threshold voltage to divide the digital signal into bright and dark parts. It checks each pixel's value against the threshold voltage, checking each pixel's value individually. If the digital signal value is greater than the threshold voltage, it is interpreted as 1; if the value is less than the threshold voltage, it is interpreted as 0. The parsed binary bit sequence is then combined to obtain the complete binary code, resulting in the absolute number of cycles N.

[0048] The absolute position is obtained by combining the precise and coarse angle measurements, and then forwarded to the external device via the protocol module. The absolute position is calculated as follows: In formula (1), X represents the absolute position measured; Indicates the absolute number of periods; Indicates the period width; This indicates a coarsely measured angle value; This indicates the measured angle value.

[0049] This application achieves absolute measurement of the time grating angle sensor by combining absolute encoding of photoelectric signals with an incremental time grating angle displacement sensor. Absolute positioning can be achieved without using a double-row structure. After the coded image is acquired by the reflective photoelectric sensor, the coarse angle value is obtained through encoding recognition and decoding, and the encoding and decoding are simple. The displacement data of the incremental time grating angle displacement sensor is used as the fine angle value. The combination of the two can realize the absolute position measurement of the time grating.

[0050] Those skilled in the art will understand that the above embodiments are specific examples of implementing the present invention, and in practical applications, various changes in form and detail may be made without departing from the spirit and scope of the present invention.

Claims

1. An absolute angular displacement sensor based on optoelectronic coding, characterized in that, The sensor comprises an excitation module, a sensor body, a signal processing circuit and a control module. The excitation module is used for generating an excitation signal and inputting the excitation signal to the sensor body. The sensor body is used for generating a displacement signal according to the excitation signal and generating an encoding signal according to a light-emitting signal. The sensor body comprises a fixed scale and a movable scale. The fixed scale comprises a first base body (1), an upper surface of the first base body (1) is provided with an excitation electrode (1-1), the excitation electrode (1-1) comprises 4P first electrode pieces arranged at equal intervals in a circle, an inductive signal receiving ring (1-2) is arranged outside the excitation electrode (1-1), and at least one photoelectric sensor (1-3) is further arranged between the inductive signal receiving ring (1-2) and an edge of the first base body (1). The movable scale comprises a second base body (2), an upper surface of the second base body (2) is provided with an inductive electrode (2-1), the inductive electrode (2-1) comprises 2P second electrodes of the same size, an inductive signal reflecting ring (2-2) is arranged outside the inductive electrode (2-1), and an upper surface of the inductive electrode (2-1) and the inductive signal reflecting ring (2-2) is covered with a light-absorbing insulating layer (2-3), and an upper surface of the light-absorbing insulating layer (2-3) is covered with at least one reflective encoding block (2-4). The signal processing circuit is used for signal enhancement processing of the displacement signal and the encoding signal. The control module is used for obtaining an absolute position value according to the processed displacement signal and the encoding signal.

2. An absolute angular displacement sensor based on opto-electronic coding as claimed in claim 1, characterized in that, The excitation signal generated by the excitation module is 4-way, and the phases of each excitation signal are different by 90°.

3. An absolute angular displacement sensor based on opto-electronic coding according to claim 1, characterized in that, The sensor body comprises the fixed scale and the movable scale, the fixed scale and the movable scale are installed in parallel and opposite directions, and the interval is d.

4. An absolute angular displacement sensor based on opto-electronic encoding according to claim 1, characterized in that, The 4p+1th first electrode piece in the clockwise circumferential direction is connected into a first group through a first excitation signal connecting line, to form an excitation phase, inputting a first excitation signal ; the 4p+2th first electrode piece in the clockwise circumferential direction is connected into a second group through a second excitation signal connecting line, to form an excitation phase, inputting a second excitation signal ; the 4p+3th first electrode piece in the clockwise circumferential direction is connected into a third group through a third excitation signal connecting line, to form an excitation phase, inputting a third excitation signal ; the 4p+4th first electrode piece in the clockwise circumferential direction is connected into a fourth group through a fourth excitation signal connecting line, to form an excitation phase, inputting a fourth excitation signal ; and p is an integer from 0 to P-1.

5. An absolute angular displacement sensor based on opto-electronic coding according to claim 1, characterized in that, The inductive signal receiving ring (1-2) is two circles.

6. An absolute angular displacement sensor based on opto-electronic encoding according to claim 1, characterized in that, The inductive signal reflecting ring (2-2) is of the same size as the inductive signal receiving ring (1-2) on the fixed scale, and is in parallel and opposite directions.

7. An absolute angular displacement sensor based on opto-electronic coding according to claim 1, characterized in that, The reflective encoding block (2-4) adopts black and white stripes of k-1 code channels to perform k-bit binary Rieg code encoding, the black and white stripes correspond to encoding "0" and encoding "1" respectively, and each encoding section corresponds to a unique period number.

8. A method of operating an absolute angle displacement sensor based on opto- electric encoding according to any one of claims 1 to 7, characterized in that Specifically, the following steps are included: A: control module on the excitation control module to produce column digital signal, after signal processing circuit processing get 4 way phase difference 90 ° of excitation signal and send to sensor body, through the mutual movement between the moving ruler and the fixed ruler, the induction electrode (2-1) on the moving ruler generates induction traveling wave signal, and the induction signal receiving ring (1-2) on the fixed ruler generates traveling wave signal on the induction signal reflection ring (2-2) and transmits to the fixed ruler; the signal processing circuit amplifies and filters the traveling wave signal and the reference signal of the same frequency, and forms a square wave through the zero-crossing comparator, and then outputs the data to the control module to obtain the fine measurement angle ; B: Firstly, the reflective photoelectric sensor (1-3) on the fixed scale is accurately positioned on the reflective encoding block (2-4); then the light-emitting control module of the control module sends a light-emitting signal to the light-emitting module of the signal processing circuit, the light-emitting module controls the light-emitting part of the reflective photoelectric sensor (1-3) to emit invisible light to the reflective encoding block (2-4), the reflective encoding block (2-4) returns the invisible light to the receiving part of the reflective photoelectric sensor (1-3), and the receiving part of the reflective photoelectric sensor (1-3) inputs the received light signal to the signal processing circuit for processing; Then, the signal processing circuit performs signal enhancement processing on the encoding signal converted by the reflective photoelectric sensor, converts the processed analog signal into a digital signal through analog-digital conversion, and then inputs the digital signal to the control module for decoding to obtain an absolute period number N; C: The absolute position is obtained by combining the fine measurement angle and the coarse measurement angle. In Equation (1), X represents the measured absolute position; represents the absolute number of cycles; represents the cycle width; represents the coarse angle value; represents the fine angle value.

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