Code disc, encoder and method for automatically compensating for eccentricity errors

Abstract

The present application relates to the technical field of encoder, and particularly provides a code disc for automatically compensating eccentric error, an encoder and a compensation method, a set of radial code tracks is engraved on the periphery of the sector code track of the traditional encoder code disc, the radial code track is composed of a plurality of concentric circle engraved lines with light and dark alternation; the radial Moire fringe signal is acquired by using the radial code track reading head during the rotation of the code disc, the distance change relation between the radial code track reading head and the rotation center of the code disc is obtained according to the interval of the concentric circle engraved lines, and the eccentric error is calculated according to the distance change relation; the eccentric error compensation data table is made according to the eccentric error and the maximum eccentric position, and the error compensation is performed on the output angle. The present application can eliminate or reduce the error caused by the eccentricity of the code disc, can improve the accuracy of the encoder as a whole, and can reduce the requirement for the installation accuracy of the encoder code disc and improve the adjustment efficiency of the code disc.

Description

Technical Field

[0001] This invention relates to the field of encoder technology, specifically providing a code disk, encoder, and compensation method for automatically compensating for eccentricity errors. Background Technology

[0002] An optoelectronic shaft angle encoder, also known as an optoelectronic angle position sensor, is a precision digital angle measuring device integrating optics, mechanics, and electronics. An optoelectronic shaft angle encoder generally consists of a shaft system, light-emitting diodes (LEDs), a code disk, slits, a receiving diode, and processing circuitry. The encoder's circular code disk has several concentric code tracks, each track composed of transparent and opaque sector-shaped areas. On one side of the code disk is a light-emitting element, and on the other side, corresponding to each code track, is a photosensitive element. Each pair of light-emitting and photosensitive elements forms a reading head, and several reading heads are combined to form a set of reading heads. The code disk (moving grating) and the slit (stationary grating) overlap to form moiré fringes. When light emitted by the light-emitting element passes through the code disk and slits and illuminates the receiving element, a moiré fringe signal is formed. When the code disk is in different positions, each photosensitive element outputs a different moiré fringe current signal depending on whether it is illuminated and the intensity of the illumination. This current signal is connected in series with a resistor, which converts the current signal into a voltage signal. This voltage signal is called the encoder's original moiré fringe input signal.

[0003] When the encoder code disk is etched, the center point of all sector code tracks is the same point, namely the center point of the code disk. When the encoder rotates, if the center point of the code disk does not coincide with the center point of the encoder's rotating shaft, code disk eccentricity occurs. This eccentricity affects the encoder's accuracy; the error caused by eccentricity is called code disk eccentricity error. During encoder assembly and adjustment, efforts are made to ensure that the center point of the code disk coincides with or is sufficiently close to the center point of the rotating shaft. The assembly and adjustment of the encoder code disk requires experienced technicians to perform under a microscope. During assembly and adjustment, the encoder shaft system is first rotated, causing the code disk to rotate as well. The fluctuation of the fine code track edge is observed under a microscope. The magnitude of the fluctuation determines the eccentricity of the code disk. Then, the position of the code disk is adjusted until the fluctuation of the fine code track edge is within the allowable range. However, due to limitations of current assembly and adjustment processes, after the encoder is assembled and adjusted, the center of the code disk and the rotation center of the shaft will not perfectly coincide; the code disk will always have a certain amount of eccentricity. The magnitude of this eccentricity is closely related to the skill level of the assembly and adjustment worker. After an encoder has been used for a period of time, or when the external environment changes, the encoder's code disk eccentricity will change to varying degrees. Since code disk eccentricity error is a non-negligible part of encoder error, and even a major part, when the code disk eccentricity error becomes large enough, it will seriously affect the encoder's output accuracy, and may even cause the encoder to produce incorrect codes and become unusable. Therefore, it is necessary to find ways to eliminate code disk eccentricity or compensate for the code disk eccentricity error. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a code disk, encoder, and compensation method for automatically compensating for eccentricity errors. This method can compensate for code disk eccentricity errors, eliminate or reduce encoder errors caused by code disk eccentricity, thereby improving the encoder's measurement accuracy.

[0005] The code disk for automatically compensating for eccentricity error provided by the present invention has fan-shaped code tracks engraved on it, and radial code tracks engraved around the fan-shaped code tracks. The radial code tracks are composed of multiple concentric circles of alternating light and dark engraving lines, and the engraving direction of the radial code tracks is perpendicular to the engraving direction of the fan-shaped code tracks.

[0006] Preferably, the concentric circles of the radial code track are equidistantly engraved.

[0007] Preferably, the radial code track is used to acquire the radial moiré fringe signal of the code disk rotation, and the eccentricity error can be obtained based on the spacing of the concentric circle markings and the radial moiré fringe signal.

[0008] An encoder that automatically compensates for eccentricity error includes a code disk for automatically compensating for eccentricity error, a slit, a radial code track reading head, and a shaft system. The slit has a slit code track that is identical to the radial code track. The positions of the slit code track and the radial code track reading head correspond to the radial code track.

[0009] The code disk that automatically compensates for eccentricity error is mounted on a rotating shaft in the shaft system and rotates with the rotating shaft.

[0010] Preferably, the radial code track reading head consists of a light-emitting diode, a receiving diode, and an amplifier circuit, with the light-emitting diode and the receiving diode respectively located on both sides of the radial code track.

[0011] An automatic compensation method for eccentricity error is provided. After the code disk for automatic eccentricity error compensation rotates at least one revolution, the radial code track reading head outputs a radial moiré fringe signal. Based on the spacing of the concentric circle marking lines, the distance change relationship between the radial code track reading head and the rotation center of the code disk can be obtained. The eccentricity error is calculated based on the distance change relationship. An eccentricity error compensation data table is created based on the eccentricity error and the maximum eccentricity position.

[0012] The output angle value is obtained by adding the angle data calculated from the sector code track to the corresponding angle compensation data in the eccentricity error compensation data table.

[0013] Preferably, the eccentricity error is measured in real time, and when the distance relationship changes, the eccentricity error is recalculated and the eccentricity error compensation data table is updated.

[0014] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0015] This invention can eliminate or reduce the error caused by code disk eccentricity, thereby improving the overall accuracy of the encoder; it can also reduce the requirements for encoder code disk installation accuracy and improve the efficiency of code disk assembly and adjustment.

[0016] Furthermore, this invention is applicable to various code disks and encoders, and has broad application prospects. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of an encoder disk that automatically compensates for eccentricity errors according to an embodiment of the present invention;

[0018] Figure 2 This is a framework diagram for compensating for eccentricity errors according to an embodiment of the present invention;

[0019] Figure 3 This is a schematic diagram of the eccentricity of the code disk that automatically compensates for eccentricity error according to an embodiment of the present invention;

[0020] Figure 4 This is a schematic diagram of the angle error caused by the eccentric installation of the encoder disk according to an embodiment of the present invention;

[0021] Figure 5 This is a flowchart of measuring eccentricity error according to an embodiment of the present invention;

[0022] Figure 6 This is a flowchart of compensation for eccentricity error provided according to an embodiment of the present invention.

[0023] The reference numerals in the figures include:

[0024] Radial code track 1, fine code track 2, coarse code track 3. Detailed Implementation

[0025] In the following description, embodiments of the invention will be described with reference to the accompanying drawings. In the description below, the same modules are denoted by the same reference numerals. Where the same reference numerals are used, their names and functions are also the same. Therefore, their detailed description will not be repeated.

[0026] 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.

[0027] like Figure 1As shown, the automatic eccentricity compensation code disk provided in this embodiment of the invention is designed based on a traditional encoder code disk. A set of radial code tracks 1 is etched around the periphery of the fan-shaped code tracks. The fan-shaped code tracks typically include fine code tracks 2 and coarse code tracks 3. The radial code tracks 1 are composed of multiple concentric circles of alternating light and dark lines, and these concentric circles are equidistantly etched. The etched direction of the radial code tracks 1 is perpendicular to the etched direction of the fine code tracks 2. The working principle of radial code tracks 1 is the same as that of fine code tracks 2 and coarse code tracks 3, differing only in the information acquired and their placement. Radial code tracks 1 are used to acquire the radial moiré fringe signal of the code disk rotation. The eccentricity error can be obtained based on the spacing of the concentric circles and the radial moiré fringe signal. The key design feature of this invention in achieving eccentricity compensation lies in the radial code tracks 1, which is applicable to any encoder code disk and can be widely used in different encoders.

[0028] like Figure 2 As shown, based on the aforementioned code disk for automatically compensating for eccentricity error, it is applied to an encoder for automatically compensating for eccentricity error. Furthermore, the encoder for automatically compensating for eccentricity error also needs to include a slit, a radial code track reading head, and a shaft system. The slit also has a slit code track identical to radial code track 1. The code disk for automatically compensating for eccentricity error is a moving grating, mounted on a rotating shaft in the shaft system and rotating synchronously with the rotating shaft. The slit is a stationary grating, relatively stationary. The positions of the code disk and the slit correspond to each other. The slit is located on one side of the code disk for automatically compensating for eccentricity error, and when the two are combined and move relative to each other, they form a moiré fringe signal. The combination of the radial code track and the slit code track forms the radial moiré fringe signal used to calculate and compensate for eccentricity error.

[0029] Compared to traditional encoders, a radial code track reading head is required. This head consists of a light-emitting diode (LED), a receiving diode, and an amplifier circuit. The LED and receiving diode are positioned on opposite sides of the code disk that automatically compensates for eccentricity errors. The light emitted by the LED passes through the radial code track and the slit code track and is received by the receiving diode. As the code disk rotates, a radial moiré fringe signal is formed. Each radial code track reading head outputs four quasi-sine signals with a 90° phase difference, denoted as J0, J90, J180, and J270. The signals output by the radial code track reading heads are amplified by a differential amplifier and converted into two orthogonal sine wave signals. The differentially amplified signals J0 and J180 are denoted as J-SIN, and the differentially amplified signals J90 and J270 are denoted as J-COS. These signals, along with the signals originally obtained by the encoder through the fan-shaped code track, enter the AD converter controlled by the data processor. Typically, the original moiré fringe signal of a set of precision code reading heads is divided into four channels, designated C0, C90, C180, and C270. These are four approximately sinusoidal signals with a 90-degree phase difference. Specifically, C0 and C180 have a 180-degree phase difference; the sinusoidal signal obtained after amplification and shaping by the C0 and C180 signals is denoted as the SIN signal. Similarly, C90 and C270 have a 180-degree phase difference; the sinusoidal signal obtained after amplification and shaping by the C90 and C270 signals is denoted as the COS signal. The SIN and COS signals have a 90-degree phase difference. Based on the values ​​of the SIN and COS signals, the formula is used:

[0030]

[0031] The subdivision angle value θ of one fine code cycle of the encoder can be obtained. Since the formula (1) may have a negative value in actual calculation, a certain angle will be added to the θ value according to the quadrant in actual calculation, so as to ensure that the subdivision value is positive and continuous within one moiré fringe signal cycle.

[0032] Based on the above-mentioned code disk and encoder with automatic eccentricity compensation, a method for automatic eccentricity compensation is proposed, the specific process of which is as follows:

[0033] like Figure 3 and Figure 4As shown, the reasons for the eccentricity error in the angle output value obtained from the fan-shaped code track are first analyzed, and the eccentricity error is calculated. Since the code disk and the rotating shaft of the axis system are manually installed later, the geometric center of the code disk does not coincide with the rotation center of the code disk, that is, the eccentricity error is unavoidable. Assuming that the distance between the geometric center and the rotation center of the code disk is ε (also called eccentricity), the angle measured based on the output information of the fan-shaped code disk is α0, the actual rotation angle of the measured rotating shaft is α1, and the measurement radius of the reading head is r, then the difference β between α0 and α1 is the eccentricity error generated during the installation process. Figure 4 From geometric relationships, we know that:

[0034]

[0035] available:

[0036]

[0037] but:

[0038]

[0039]

[0040] Formula (5) is the formula for calculating the eccentricity error. As can be seen from Formula (5), the larger the eccentricity, the larger the eccentricity error; the smaller the measuring radius of the reading head, the larger the eccentricity error. When α0 is 0° or 180°, the eccentricity error is 0; when α0 is between 0° and 180°, the eccentricity error is positive; and when α0 is between 180° and 360°, the eccentricity error is negative.

[0041] The measurement angle α0 shown in formula (5) is calculated based on the fact that the output angle value is 0 when the center point of the code disk, the rotation center, and the reading head are on a straight line. That is, this position is the 0-degree reference of the encoder. The eccentricity error will be distributed in an approximately sinusoidal wave. Since the eccentricity ε is much smaller than the measurement radius r, in order to reduce the computational load of the processor in actual calculation, formula (5) can be simplified to:

[0042]

[0043] Normally, the difference between formulas (5) and (6) is very small and can be ignored. In special cases, formula (5) can be used without simplification.

[0044] After analyzing the causes of the eccentricity error, radial code track 1 is used to compensate for the eccentricity error, such as... Figure 5As shown, when the code disk with automatic eccentricity compensation rotates, the J-SIN and J-COS signals output by the radial reading head are collected in real time, and the collected signals are subdivided using formula (1). The subdivided values ​​should be displacement values. Assuming the spacing between the concentric circles of radial code track 1 is P, the distance corresponding to a complete radial moiré fringe signal cycle is P. During the rotation, the encoder processor will calculate the radial displacement value in real time. When the radial moiré fringe signal crosses the cycle in the positive direction, the radial displacement value increases by P; when the radial moiré fringe signal crosses the cycle in the reverse direction, the radial displacement value decreases by P. After one rotation, a maximum radial displacement value P can be obtained. MAX And a minimum radial displacement value P MIN , by the largest P MAX and P MIN The eccentricity ε can be obtained:

[0045]

[0046] Based on the known eccentricity ε and the measurement radius r, the eccentricity error β corresponding to each actual measured angle α0 position can be calculated by formula (6). An eccentricity error compensation data table is made based on the eccentricity errors of all positions, and then the eccentricity error compensation data table is stored in the processor's FLASH to achieve automatic compensation.

[0047] However, when the radial displacement of the radial moiré fringe signal is at its maximum value P MAX At this time, the eccentricity error is 0, but the actual measured encoder angle value α0 may not be 0. It is necessary to set the radial displacement to the maximum value P. MAX The encoder displacement value measured over time is denoted as α. P When performing angle calculations, the actual calculated angle values ​​α0 and α P The difference is used as the address to look up the eccentricity error compensation data table, and β′ represents the eccentricity error after the address is supplemented. The correspondence between the value β′ in the eccentricity error compensation data table and the actual calculated angle value α0 is as follows:

[0048]

[0049] As shown in formula (8), the value obtained by adding the angle value β′ obtained by looking up the table to the calculated angle value α0 is used as the compensated value output.

[0050] The relationship between the compensated output angle value and the uncompensated angle value α0 is as follows:

[0051] Formula (9): α1=α0+β';

[0052] As can be seen from the above, when an encoder that automatically compensates for eccentricity error performs eccentricity error compensation, such as... Figure 6As shown, firstly, the original data obtained by the encoder based on the sector code track is collected and the angle α0 before compensation is calculated. Then, the eccentricity error compensation data β′ is obtained by looking up the eccentricity error compensation data table. Then, the angle data α1 after compensation is calculated according to formula (9). Finally, the angle data α1 is output according to the protocol. This process can be implemented by Shenjiang Network. By designing matching software or algorithms for the encoder, fully automatic compensation can be achieved.

[0053] like Figure 5 As shown, during the rotation of the encoder with automatic eccentricity compensation, the eccentricity error is measured in real time. After the encoder has been running for a period of time, a new eccentricity value ε or α is calculated. P If the deviation from the previously stored value exceeds a certain threshold, the new ε value and α will be... P The value is stored in FLASH, and the eccentricity error β′ is recalculated, updating the value and address in the eccentricity error compensation data table; no data update is performed when the threshold is not exceeded. The threshold here is a manually set value, which can be set according to the required encoder accuracy and other actual conditions.

[0054] In addition to the embodiments shown, the present invention can also be used in various angular displacement measuring devices, such as shaft angle encoders, image encoders, etc., and can also be used in linear displacement measuring devices, such as grating rulers. The working principle is the same: by measuring the radial deviation of the grating ruler during its movement, error compensation for the radial deviation of the grating ruler can be achieved.

[0055] 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.

[0056] 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 method for automatically compensating for eccentricity error, characterized in that, Readings are taken using an encoder that automatically compensates for eccentricity errors. The encoder that automatically compensates for eccentricity errors includes a code disk that automatically compensates for eccentricity errors, a slit, a radial code track reading head, and a shaft system. The code disk that automatically compensates for eccentricity error is engraved with fan-shaped code tracks. Radial code tracks are engraved around the fan-shaped code tracks. The radial code tracks are composed of multiple concentric circles of alternating light and dark lines. The engraving direction of the radial code tracks is perpendicular to the engraving direction of the fan-shaped code tracks. The slits are engraved with the same slit code track as the radial code track, and the positions of the reading heads of the slit code track and the radial code track correspond to the radial code track; the code disk that automatically compensates for eccentricity error is mounted on the rotating shaft in the shaft system and rotates with the rotating shaft. After the code disk with automatic eccentricity compensation has rotated at least one revolution, the radial code track reading head outputs a radial moiré fringe signal. Based on the spacing of the concentric circle markings, the distance change between the radial code track reading head and the rotation center of the code disk can be obtained. The eccentricity error is then calculated based on this distance change. The calculation of the eccentricity error based on the distance change includes: calculating the eccentricity ε based on the distance change. ； Among them, P MAX The maximum radial displacement value, P MIN This represents the minimum radial displacement value. Calculate the eccentricity error corresponding to each actual measured angle α0 position. β for: ； Where α0 represents the angle measured based on the output information of the fan-shaped encoder disk, α1 represents the actual rotation angle of the measured rotating shaft, and r is the measurement radius of the reading head; An eccentricity error compensation data table is created based on the eccentricity error and the position of maximum eccentricity, including: Calculate the compensation data in the eccentricity error compensation data table according to the following formula. β 'for: ； Where α0 represents the angle measured based on the output information of the fan-shaped encoder disk, α P This indicates that the radial displacement is at its maximum value. P MAX The encoder displacement value measured at time, where r is the measurement radius of the reading head; The output angle value is obtained by adding the angle data calculated from the sector code track to the corresponding angle compensation data in the eccentricity error compensation data table.

2. The method for automatically compensating for eccentricity error as described in claim 1, characterized in that, The eccentricity error is measured in real time. When the distance relationship changes, the eccentricity error is recalculated and the eccentricity error compensation data table is updated.

3. The method for automatically compensating for eccentricity error as described in claim 1, characterized in that, The concentric circles of the radial code track are equidistantly engraved.

4. The method for automatically compensating for eccentricity error as described in claim 3, characterized in that, The radial code track is used to obtain the radial moiré fringe signal of the code disk rotation. The eccentricity error can be obtained from the spacing of the concentric circle markings and the radial moiré fringe signal.

5. The method for automatically compensating for eccentricity error as described in claim 1, characterized in that, The radial code track reading head consists of a light-emitting diode, a receiving diode, and an amplifier circuit. The light-emitting diode and the receiving diode are respectively located on both sides of the radial code track.

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