A method and apparatus for encoder calibration data amplification and error compensation

Abstract

This invention discloses a method and apparatus for encoder calibration data amplification and error compensation. It utilizes multiple evenly arranged reading heads to measure angles and collect angular measurement and calibration data. A motion control system is used to rotate a prism, amplifying the calibration data. Based on the harmonic characteristics of the angular measurement data, the calibration data is integrated to establish an angular encoder angular measurement error compensation model. The integrated error data is then fed into the established angular encoder angular measurement error compensation model for angular measurement error compensation, achieving encoder angular measurement error compensation based on a multi-reading head arrangement. This invention employs a high-precision autocollimator to calibrate the circular grating encoder and acquire corresponding calibration data. A data integration algorithm is used to integrate the error data, and finally, an angular measurement error compensation model is established using the error data, achieving high-precision compensation of angular measurement errors under a multi-reading head layout.

Description

Technical Field

[0001] This invention belongs to the field of precision measurement technology, specifically relating to a method and apparatus for encoder calibration data amplification and error compensation. Background Technology

[0002] High-precision angle measuring devices are widely used in aerospace, military industry, precision instruments, microelectronics, and many other high-tech fields. Circular grating angle encoders are widely used due to their simple structure, small size, and ease of automation and digitization. With the continuous improvement of productivity, various industries are placing higher demands on the angle measurement accuracy of circular gratings. The angle measurement error of a circular grating angle encoder mainly includes installation error, grating manufacturing error, signal processing error, and errors caused by environmental and human factors. Due to the self-enclosing characteristic of the circular grating, most of these errors exhibit periodicity. Based on this property, the harmonic error theory of circular grating encoders has become the main means of describing the angle measurement error of circular gratings. Extensive research has been conducted both domestically and internationally on this property, and different angle measurement error compensation schemes for circular grating angle encoders have been proposed.

[0003] Currently, extensive research has been conducted both domestically and internationally on hardware and software compensation techniques for the angle measurement accuracy of circular gratings. This has led to the development of hardware compensation schemes utilizing multiple readheads and software compensation schemes employing compensation algorithms based on error compensation models. However, hardware compensation schemes are often limited by cost and readhead installation constraints, preventing unlimited expansion. Furthermore, installation deviations between readheads cannot completely eliminate harmonic errors of corresponding orders. Software compensation, by fitting error curve characteristics, performs online error compensation, overcoming the limitations of hardware compensation and further eliminating residual errors in the device, thus improving the angle measurement accuracy of the angle encoder. However, using only software compensation methods for single-readhead angle encoders often results in insufficient accuracy due to environmental factors. Moreover, software compensation for angle measurement errors requires a higher-precision angle measurement reference as a calibration value; currently, high-precision grating angle encoders or photoelectric autocollimators are commonly used. However, the accuracy level of most high-precision grating angle encoders is currently around ±1″, which cannot meet the requirements for a sub-arcsecond encoder calibration device. In contrast, a calibration device composed of a multifaceted prism and an opto-autocollimator has achieved an angle measurement accuracy of ±0.1″, which is sufficient for studying the angle measurement error of circular grating angle encoders. However, due to the limitation on the number of faces of the multifaceted prism, this calibration device often only yields a limited amount of discrete data. This results in the inability to fully represent the characteristics of the error curve, especially when higher-order harmonic errors have a significant impact on the angle measurement error. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide an encoder calibration data amplification and error compensation method and device to address the shortcomings of the prior art, and to solve the technical problem that residual errors caused by installation errors and environmental factors cannot be further eliminated in high-precision angle measurement using a multi-reading head layout hardware compensation method.

[0005] The present invention adopts the following technical solution:

[0006] A method for encoder calibration data amplification and error compensation includes the following steps:

[0007] S1. Use multiple evenly arranged reading heads to measure angles and collect angle measurement data and calibration data;

[0008] S2. Use the motion control system to complete the rotation of the prism and amplify the calibration data obtained in step S1.

[0009] S3. Based on the harmonic characteristics of the angle measurement data, integrate the calibration data obtained in step S2 to establish an angle encoder angle measurement error compensation model.

[0010] S4. The error data integrated in step S3 is brought into the angle encoder angle measurement error compensation model established in step S3 to perform angle measurement error compensation, thereby realizing encoder angle measurement error compensation based on multi-reading head arrangement.

[0011] Specifically, in step S1, multiple reading heads are evenly arranged on the circumference of the encoder. The multifaceted prism and the encoder grating code disk are coaxially mounted with the shaft system and rotate at intervals on the air-bearing shaft system. The eccentricity of the multifaceted prism is controlled within 2μm. The encoder angle measurement data is synthesized and output by multiple evenly distributed reading heads. The calibration data is read and output by a calibration device composed of an autocollimator and the multifaceted prism.

[0012] Specifically, in step S2, after completing a set of calibrations, the motor is controlled to rotate. The motor is then locked, and the polyhedron is readjusted. The polyhedron is rotated to 1 / 3 of the rotation interval so that it is aligned with the photoelectric autocollimator. After the rotation is completed, the eccentricity of the polyhedron is adjusted to control it within 2μm. The prism rotation angle is then re-aligned with the autocollimator and calculated. The angle value is read by a high-precision grating. The rotation calibration step is performed again to complete the acquisition and calculation of multiple sets of error data.

[0013] Specifically, in step S3, data integration involves:

[0014] The average of multiple sets of data before and after rotating the polyhedron is performed to obtain the mean value of the calibration data after each rotation of the polyhedron. The amplitude and phase of the 0th harmonic error of each set of data are extracted by Fourier transform. By eliminating the 0th harmonic error, the multiple sets of angle measurement error data are merged into the same coordinate system to complete the processing and integration of error data.

[0015] Furthermore, the radial runout of the polyhedron is readjusted each time it is rotated, and the horizontal axis reading of the autocollimator is kept within ±10″ during calibration.

[0016] Furthermore, the relative angular measurement error of the angle encoder in the absolute coordinate system after data integration. for:

[0017]

[0018] in, The magnitude of the DC component in the harmonic components of the encoder angle measurement error. The phase magnitude of the DC component. For a certain coordinate system, the lower angle encoder is in The relative angular measurement error when the measurement is taken at the starting point. This refers to the random error in angle measurement error.

[0019] Specifically, in step S3, the angle encoder angle measurement error compensation model adopts the angle measurement error linear interpolation compensation model, as follows:

[0020]

[0021] in, In the coordinate system after data integration The location is the angular position, and N is the sequence number of the data point after data integration. For the first N The corner positions of the data points.

[0022] Specifically, in step S3, the angle encoder angle measurement error compensation model adopts the angle measurement error harmonic error compensation model, as follows:

[0023]

[0024] in, Let k be the angular position in the coordinate system after data integration, and k be the harmonic order of the angular measurement error. The phase angle of each harmonic error, The amplitude of each harmonic error is given.

[0025] Specifically, in step S4, the integrated error compensation data is input into the angle encoder angle measurement error compensation model. The error curve is fitted according to the input error data to obtain the corresponding angle-relative error relationship. By inputting the corresponding angles measured by multiple reading heads, the error values ​​near the angle position are obtained. The error values ​​are compensated and corrected to obtain the circular grating angle measurement value.

[0026] In a second aspect, embodiments of the present invention provide an encoder calibration data amplification and error compensation device, comprising:

[0027] The data module uses multiple evenly arranged reading heads to measure angles and collect angle measurement data and calibration data;

[0028] The amplification module uses a motion control system to rotate the prism and amplify the calibration data obtained from the data module.

[0029] The integration module integrates the calibration data obtained from the amplification module based on the harmonic characteristics of the angle measurement data, and establishes an angle encoder angle measurement error compensation model.

[0030] The compensation module takes the error data integrated by the integration module and inputs it into the angle encoder angle measurement error compensation model established by the integration module to perform angle measurement error compensation, thereby realizing encoder angle measurement error compensation based on multi-reading head arrangement.

[0031] Compared with the prior art, the present invention has at least the following beneficial effects:

[0032] A method for encoder calibration data amplification and error compensation is proposed. By evenly distributing multiple reading heads on the circumference and utilizing the coupling effect between these reading heads, the method reduces periodic error components such as angle measurement errors caused by grating disk installation errors, grating manufacturing errors, and signal processing errors, thus achieving high-precision angle measurement for circular grating angle encoders. Using an opto-collimator and a multi-faceted prism, along with a motion control system composed of a high-precision grating and a servo motor, automatic calibration of the circular grating angle encoder's angle measurement error is achieved. Simultaneously, the high-precision grating is used to accurately measure the rotational position of the multi-faceted prism, providing a phase relationship for calibration data amplification. Furthermore, by rotating the multi-faceted prism, the angle between two prism faces can be subdivided.

[0033] Furthermore, by utilizing multiple evenly distributed reading heads, the periodic error components caused by grating disk installation errors, grating manufacturing errors, and signal processing errors are reduced, eliminating the vast majority of angle measurement errors and achieving high-precision angle measurement for the circular grating angle encoder. The eccentricity of the multifaceted prism is controlled within 2μm, ensuring good concentricity between the prism and the shaft system, reducing the decrease in calibration system accuracy caused by misalignment during rotation, and further stabilizing the calibration system accuracy within ±0.1″. Simultaneously, consistent prism installation conditions are maintained across several iterations to ensure a single variable during measurement and data integration.

[0034] Furthermore, to obtain more calibration data to reconstruct the angle measurement error, a group calibration method is used. Due to the inherent characteristics of the air-bearing shaft, the shaft system will wobble during the adjustment of the polyhedron, thus affecting subsequent test results. Therefore, a motor is used to lock the shaft system, which can keep the shaft system stationary during the rotation and adjustment of the polyhedron, ensuring that the shaft system is in a static state when the prism is readjusted. At the same time, through the high-precision positioning of the motor, it is possible to achieve precise positioning on two adjacent prism faces. The angle is subdivided into 1 / 3.

[0035] Furthermore, to further eliminate random errors in the angle measurement data, a method of averaging multiple measurements was adopted, which further reduced the random errors in the angle measurement data. Due to the harmonic characteristics of circular grating angle measurement errors, the angle measurement error manifests as the result of the superposition of harmonics with different periods and phases over an integer cycle, where the 0th harmonic contains error information relative to the starting point of the angle measurement. By performing a Fourier transform on the angle measurement data, the harmonic information of the angle measurement data can be extracted. Then, the angle measurement data can be integrated based on the harmonic information, ultimately making the originally single... N After amplification, the angle measurement data from 3 data points were obtained as 3 N The angle measurement data from each data point makes the angle measurement error curve more detailed and the error characteristics more accurate, providing a prerequisite for error prediction and high-precision compensation of angle measurement data.

[0036] Furthermore, the angular measurement error of the diagonal encoder is calibrated using a multifaceted prism and an optoelectronic autocollimator. During the calibration process, the X-axis reading of the optoelectronic collimator is controlled within ±10″ using motor fine-tuning, ensuring the calibration accuracy of the angular measurement error is within ±0.1″. Simultaneously, the same sampling point in multiple sets of calibration data fluctuates within a small range; the angular measurement error caused by this small fluctuation is negligible, further guaranteeing the consistency of the calibration data.

[0037] Furthermore, due to the relative measurement characteristics of incremental encoders, when any point within the circumference is selected as the starting point for angle measurement error, since that point itself has an angle measurement error in the fixed coordinate system for error restoration, there is a DC component in the angle measurement data obtained with that point as the test starting point. The magnitude of this component is the angle measurement error value of that point in the fixed coordinate system. This DC component will seriously affect the compensation of angle measurement error, causing the angle measurement data to shift. By removing the DC component, an unbiased error compensation model can be obtained, thereby improving the angle measurement accuracy.

[0038] Furthermore, in the angle measurement error after hardware compensation, the proportion of higher-order harmonic errors increases significantly. For even higher-order harmonic errors, although the data points are subdivided, it is still impossible to extract all higher-order harmonic errors using a limited number of data points. Therefore, by using the averaging effect of linear interpolation, the influence of the unextracted higher-order harmonic errors can be reduced as much as possible, thereby improving the compensation accuracy of angle measurement error.

[0039] Furthermore, as the subdivision factor of the angle measurement data increases, more harmonic components of higher orders can be extracted by Fourier transforming the angle measurement data. The harmonic components of order 100 and above have a very small impact on the angle measurement error and can be ignored. At this time, using harmonic error compensation to restore the angle measurement error data is more in line with the error characteristics of the circular grating angle encoder itself, and the compensation effect is better.

[0040] Furthermore, by using a multi-reading head evenly distributed scheme to obtain the relative rotation angle of the shaft system, the angle can be substituted into the error compensation model to achieve higher precision angle measurement.

[0041] It is understandable that the beneficial effects of the second aspect mentioned above can be found in the relevant descriptions in the first aspect mentioned above, and will not be repeated here.

[0042] In summary, this invention uses a high-precision autocollimator to perform error calibration on the circular grating encoder and obtain the corresponding calibration data. The error data is integrated through a data integration algorithm. Finally, an angle measurement error compensation model is established using the error data, which realizes high-precision compensation of angle measurement error under multiple reading head layout.

[0043] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0044] Figure 1 A simplified structural diagram of the calibration compensation device;

[0045] Figure 2 This is a distribution map of the starting points for data amplification.

[0046] Figure 3This is a diagram showing the evenly distributed installation of the reading heads;

[0047] Figure 4 The following is a comparison of the error curves of the multi-reading head layout under data amplification, where (a) is the angle measurement error curve of a single reading head, and (b) is the angle measurement error curve of eight reading heads.

[0048] Figure 5 The graphs show the angle measurement error curves under a multi-reading head layout, where (a) is the angle measurement error curve under a layout with four reading heads evenly distributed, and (b) is the angle measurement error curve under a layout with eight reading heads evenly distributed.

[0049] Figure 6 The graphs show the angle measurement error curves after linear interpolation compensation for a single set of calibration data. (a) shows the angle measurement error compensation under a uniform layout of four reading heads, and (b) shows the angle measurement error compensation under a uniform layout of eight reading heads.

[0050] Figure 7 The angle measurement error curves after data amplification and linear interpolation compensation are shown in Figure 1. (a) shows the angle measurement error compensation under a uniform layout of four reading heads, and (b) shows the angle measurement error compensation under a uniform layout of eight reading heads.

[0051] Figure 8 The angle measurement error curves after data amplification harmonic error compensation are shown in the figure. (a) shows four-reading head compensation, and (b) shows eight-reading head compensation. Detailed Implementation

[0052] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0053] In the description of this invention, it should be understood that the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0054] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0055] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes such combinations. For example, A and / or B can represent three cases: A alone, A and B simultaneously, and B alone. Additionally, the character " / " in this document generally indicates that the preceding and following objects have an "or" relationship.

[0056] It should be understood that although terms such as first, second, third, etc., may be used in the embodiments of the present invention to describe the preset range, these preset ranges should not be limited to these terms. These terms are only used to distinguish the preset ranges from one another. For example, without departing from the scope of the embodiments of the present invention, the first preset range may also be referred to as the second preset range, and similarly, the second preset range may also be referred to as the first preset range.

[0057] Depending on the context, the word "if" as used here can be interpreted as "when," "when," "in response to determination," or "in response to detection." Similarly, depending on the context, the phrase "if determination" or "if detection (of the stated condition or event)" can be interpreted as "when determination," "in response to determination," "when detection (of the stated condition or event)," or "in response to detection (of the stated condition or event)."

[0058] The accompanying drawings illustrate various structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0059] This invention provides a method for encoder calibration data amplification and error compensation. Based on the harmonic properties of circular grating angle measurement errors, the angle measurement information from multiple reading heads is synthesized and calibrated, and the data is amplified and synthesized to obtain more angle measurement error data. Using the amplified calibration data, combined with the periodicity and harmonic properties of circular grating angle measurement errors under a multi-readhead layout, a linear interpolation model and a harmonic error compensation model for circular grating angle measurement errors are established, thereby achieving further compensation for residual device errors in the angle measurement device.

[0060] Please see Figure 1 The present invention provides a method for encoder calibration data amplification and error compensation, comprising the following steps:

[0061] S1. Multiple reading heads are evenly arranged on the circumference of the circular grating. NThe faceted prism and grating code disk are coaxially mounted with the shaft system and rotate at intervals on the air-bearing shaft system. The eccentricity of the faceted prism is controlled within 2μm. The encoder angle measurement data is synthesized and output by multiple evenly distributed reading heads. The calibration data is read and output by a calibration device composed of an autocollimator and a faceted prism, thus completing the angle measurement and data calibration.

[0062] By synchronously acquiring angular data from multiple reading heads evenly distributed on the circumference, angular measurement information at different phases at the same time can be obtained. By averaging the angular measurement information from multiple reading heads, some periodic errors generated during the rotation of the encoder can be eliminated, and random errors are also suppressed to a certain extent. This improves the angular measurement accuracy of the shaft system, eliminates most of the device errors, further reduces the repeatability of the angle encoder, and provides more accurate angular position information for software compensation of angular measurement errors.

[0063] Please see Figure 3 Angle measurements are performed using a scheme with multiple reading heads evenly distributed, eliminating the influence of factors such as installation errors on angle measurement. Using a multi-faceted prism and an autocollimator as the calibration system, high-precision calibration of ±0.1″ angle measurement error can be achieved within a range of ±100″ facing the prism face. By sequentially calibrating using the 24 faces of the 24-faceted prism, 24 calibration values ​​for angle measurement error can be obtained for each test group.

[0064] S2. After completing a set of calibrations, control the motor to rotate. The motor is then locked, and the polyhedron is readjusted. The polyhedron is rotated to 1 / 3 of the rotation interval so that it is aligned with the photoelectric autocollimator again. After the rotation is completed, the eccentricity of the polyhedron is adjusted to control it within 2μm. The rotation angle of the prism is then re-aligned with the autocollimator and calculated. The specific angle value is read by the high-precision grating in the test device. The rotation calibration step is executed again to acquire and calculate more sets of error data.

[0065] The angle measurement error of the angle encoder is calibrated using a multifaceted prism and an optoelectronic autocollimator. During the calibration process, the X-axis reading of the optoelectronic collimator is controlled within ±10″, and the Y-axis reading is within ±10″ within the field of view. This ensures that the same sampling point of multiple sets of calibration data fluctuates within a small range, thus ensuring the consistency of the sampling point coordinates in the calibration data.

[0066] The polyhedron is rotated, and the self-locking function of the motor is used to lock the shaft system. The polyhedron is rotated, and the radial runout of the polyhedron as it rotates with the shaft system is adjusted. At the same time, a high-precision grating is used to record the difference in readings before and after the rotation adjustment of the polyhedron, and then the precise value of the rotation angle of the polyhedron is calculated.

[0067] By using the precise positioning motion of the motor, the angle range between two adjacent faces of the multifaceted prism can be subdivided during calibration to obtain more sets of calibration data at different angular positions within the entire circle.

[0068] The calibration process involves relative angular measurement error. For different sets of calibration data, each set is in a different coordinate system due to the different starting points. In order to integrate the three sets of calibration data, it is necessary to unify the coordinate system based on the harmonic properties of the angular measurement error.

[0069] S3. Combining the harmonic characteristics of the angle measurement error of the circular grating angle encoder, multiple sets of angle measurement error calibration results are integrated, and then multiple sets of relative error calibration data from different starting points are integrated into the same starting point to obtain more accurate angle measurement error compensation data of the circular grating encoder at this starting point, and an accurate angle encoder angle measurement error compensation model is established.

[0070] Angular measurement error of circular grating angle encoder Considering the angle measurement error as being composed of harmonic errors of different orders, since the direction of installation errors and the starting point of the grating will not be exactly the same during the grating installation process, and since incremental grating angle encoders perform relative measurements, the magnitude of the phase directly affects the distribution of the angle measurement error curve. Therefore, the harmonic error relationship of the angle measurement error of a circular grating angle encoder is established. This is a prerequisite for the integration of calibration data and the compensation of angle measurement errors.

[0071] The principle of integrating multiple sets of calibration data is as follows:

[0072]

[0073] in, The magnitude of the DC component in the harmonic components of the encoder angle measurement error. The phase magnitude of the DC component. For a certain coordinate system, the lower angle encoder is in The relative angular measurement error when the measurement is taken at the starting point. This refers to the random error in angle measurement error. To set the relative angular measurement error of the angle encoder in the absolute coordinate system.

[0074] The specific steps for processing and integrating calibration data are as follows:

[0075] Multiple sets of data before and after rotating the polyhedron are averaged to obtain the mean of the calibration data after each rotation. Fourier transform is then used to extract the amplitude and phase of the 0th harmonic error for each set of data. By eliminating the 0th harmonic error, multiple sets of angle measurement error data are merged into the same coordinate system to complete the processing and integration of error data.

[0076] Each time the polyhedron is rotated, the radial runout of the polyhedron needs to be readjusted. During calibration, the horizontal axis reading of the autocollimator should be controlled within ±10″, so that each point is taken fluctuating within a small range.

[0077] The established error compensation linear interpolation model and harmonic error compensation model are as follows:

[0078] Based on the processed and integrated angle measurement error data, the angle measurement error curve is fitted using linear interpolation and harmonic fitting algorithms. To ensure the accuracy of harmonic information extraction, the sampling points are first divided equally using linear interpolation, and then the interpolation error results are subjected to Fourier transform to obtain the harmonic information of the angle measurement error.

[0079] Linear interpolation compensation model for angle measurement error:

[0080]

[0081] in, for Dot at The relative error value at the point, In the coordinate system after data integration The position is the angular position, and N is the sequence number of the data point after data integration.

[0082] Angle measurement error harmonic error compensation model:

[0083]

[0084] in, for Dot at The relative error value at the point, Let k be the angular position in the coordinate system after data integration, and k be the harmonic order of the angular measurement error. The phase angle of each harmonic error, The amplitude of each harmonic error is given.

[0085] S4. Input the integrated error compensation data into the angle encoder angle measurement error compensation model, fit the error curve according to the input error data, and obtain the corresponding angle-relative error relationship. By inputting the corresponding angles measured by the eight reading heads, the error value near the angle position is obtained. By compensating for this error value, the angle measurement value of the circular grating with the multi-reading head layout is corrected.

[0086] Please see Figure 5The system performs online compensation for angle measurement errors. It utilizes the rotation information measured by multiple evenly distributed reading heads and combines it with the angle measurement error compensation model. The rotation information and initial phase angle information during the rotation of the shaft system are incorporated into the compensation model. By correcting the angle measurement information, the final high-precision angle measurement output is achieved.

[0087] In another embodiment of the present invention, an encoder calibration data amplification and error compensation device is provided. This device can be used to implement the above-mentioned encoder calibration data amplification and error compensation method. Specifically, the encoder calibration data amplification and error compensation device includes a data module, an amplification module, an integration module, and a compensation module.

[0088] The data module utilizes multiple evenly arranged reading heads to measure angles and collect angle measurement and calibration data.

[0089] The amplification module uses a motion control system to rotate the prism and amplify the calibration data obtained from the data module.

[0090] The integration module integrates the calibration data obtained from the amplification module based on the harmonic characteristics of the angle measurement data, and establishes an angle encoder angle measurement error compensation model.

[0091] The compensation module takes the error data integrated by the integration module and inputs it into the angle encoder angle measurement error compensation model established by the integration module to perform angle measurement error compensation, thereby realizing encoder angle measurement error compensation based on multi-reading head arrangement.

[0092] In another embodiment of the present invention, a terminal device is provided, comprising a processor and a memory. The memory stores a computer program, which includes program instructions. The processor executes the program instructions stored in the computer storage medium. The processor may be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing and control core of the terminal, suitable for implementing one or more instructions, specifically suitable for loading and executing one or more instructions to achieve a corresponding method flow or corresponding function. The processor described in this embodiment can be used for the operation of encoder calibration data amplification and error compensation methods, including:

[0093] Angle measurement and calibration data are collected using multiple evenly arranged reading heads; the calibration data is amplified by using a motion control system to complete the rotation of the prism; the calibration data is integrated based on the harmonic characteristics of the angle measurement data to establish an angle encoder angle measurement error compensation model; the integrated error data is then fed into the established angle encoder angle measurement error compensation model to perform angle measurement error compensation, thus realizing encoder angle measurement error compensation based on multi-reading head arrangement.

[0094] In another embodiment of the present invention, a storage medium is provided, specifically a computer-readable storage medium (Memory). This computer-readable storage medium is a memory device in a terminal device used to store programs and data. It is understood that the computer-readable storage medium here can include both the built-in storage medium in the terminal device and extended storage media supported by the terminal device. The computer-readable storage medium provides storage space that stores the terminal's operating devices. Furthermore, this storage space also stores one or more instructions suitable for loading and execution by a processor. These instructions can be one or more computer programs (including program code). It should be noted that the computer-readable storage medium here can be high-speed RAM or non-volatile memory, such as at least one disk storage device.

[0095] One or more instructions stored in a computer-readable storage medium can be loaded and executed by a processor to implement the corresponding steps of the encoder calibration data amplification and error compensation method in the above embodiments; one or more instructions in the computer-readable storage medium are loaded and executed by the processor to perform the following steps:

[0096] Angle measurement and calibration data are collected using multiple evenly arranged reading heads; the calibration data is amplified by using a motion control system to complete the rotation of the prism; the calibration data is integrated based on the harmonic characteristics of the angle measurement data to establish an angle encoder angle measurement error compensation model; the integrated error data is then fed into the established angle encoder angle measurement error compensation model to perform angle measurement error compensation, thus realizing encoder angle measurement error compensation based on multi-reading head arrangement.

[0097] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0098] Example

[0099] (1) Eight reading heads are evenly arranged on the circumference of the code disk. The grating signals collected by the eight reading heads are averaged and synthesized to obtain the shaft rotation angle measurement value. At the same time, a multi-faceted prism is installed on the shaft system, and the rotation angle is calibrated using an optoelectronic collimator to obtain the measurement error of the circular grating angle encoder.

[0100] Angular measurement error of a circular grating angle encoder with a single reading head The expression for harmonics is:

[0101]

[0102] Where k is the order of the harmonic errors that make up the circular grating encoder, and n is the number of reading heads arranged, n=1, 2, 3... Let be the amplitude of the k-th harmonic component. The angle encoder follows the angle through which the shaft system rotates. The initial phase of each harmonic component.

[0103] By acquiring the grating signal through eight reading heads, and based on the harmonic characteristics of the circular grating's angle measurement error, the signal is evenly distributed on the circumference. n When reading a head, by... n The theoretical angle measurement error obtained by averaging the readings from each reading head is:

[0104] (1)

[0105] in, For the process n The angle measurement error of the signal synthesized from the reading heads n The number of reading heads is evenly distributed. The magnitude of the harmonic error is given by the value of each harmonic. k The order of each harmonic error is given. The angular position of the shaft system rotation.

[0106] For a certain order of harmonics k In other words, multiple reading heads are used in k The synthesis error under subharmonics is:

[0107] (2)

[0108] By performing trigonometric transformations on the above formula, the equation can be simplified to:

[0109] (3)

[0110] When eight reading heads are evenly distributed around the circumference of the circular grating, the angle calculated by averaging the test results from multiple reading heads can effectively eliminate angle measurement errors. The harmonic error is only one of the errors. Harmonic errors of the first order cannot be eliminated. By using this multi-readhead layout, on the one hand, the influence of random errors in a single readhead is reduced; on the other hand, the installation error, subdivision error, and manufacturing error of the grating code disk are all periodic errors of angle encoding angle measurement error. Therefore, this method can eliminate these periodic components to a certain extent, thereby improving the angle measurement accuracy.

[0111] (2) Collect the composite data of eight reading heads, calculate the relative rotation angle of the shaft system based on the composite data of the reading heads, and calculate the angle measurement error of the circular grating angle encoder using the calibration values ​​of the polyhedron and the autocollimator.

[0112] Because of the suppression effect of multiple reading heads on the harmonic components of the angle measurement error, the low-order harmonic components in the angle measurement error are well suppressed. The high-order harmonic components of the angle measurement error have a greater impact on the angle measurement error. This means that the 24 calibration points cannot fully characterize the error curve, and the calibration data needs to be expanded.

[0113] Please see Figure 2 Two additional starting points were added between two adjacent planes of the polyhedron. The starting points were aligned by rotating the polyhedron, and corresponding error calibrations were performed on each point. To ensure the consistency of the experimental environment and conditions, a motor-controlled shaft system was used to perform point-to-point motion, while the radial runout of the polyhedron as it rotated with the shaft system was controlled to be within 2 μm.

[0114] (3) The error calibration points obtained from different starting points are merged and integrated into the same coordinate system. The angle measurement error of each calibration point is the error generated relative to the zero point of the coordinate system. Then, the three sets of error values ​​are integrated into an error curve.

[0115] Suppose the angle measurement error is integrated into a certain fixed coordinate system. for:

[0116] (4)

[0117] in, Let k be the DC component of the angle measurement error in this coordinate system, and k be the order of each harmonic error that makes up the angle measurement error. The amplitudes of each harmonic component are given. Let n be the phase of each harmonic component, and n be the number of uniformly distributed reading heads. This represents the angular position in the coordinate system, i.e., the x-coordinate.

[0118] In this coordinate system, When measuring from a starting point, there is an angle measurement error. :

[0119] (5)

[0120] (6)

[0121] Performing a Fourier transform on equation (6), since For a fixed value, the amplitude of each harmonic component is then calculated as follows:

[0122] (7)

[0123] According to the equation:

[0124] (8)

[0125] The relationship between the integrated angle measurement error and the unintegrated angle measurement error can be obtained as follows:

[0126] (9)

[0127] Please see Figure 4 (a) and (b) By integrating the angle measurement error data, it can be clearly seen that the integrated error curve exhibits more features when the four and eight reading heads are evenly distributed. Furthermore, as the number of reading heads increases, the low-order harmonic components are greatly suppressed, and the features displayed by the data integration method are also increasing. The description of the angle measurement error curve is more accurate than that of a single set of calibration data.

[0128] (4) Based on the obtained integration results, an error compensation model is established using the integrated angle measurement error data.

[0129] The established error compensation linear interpolation model and harmonic error compensation model are as follows:

[0130] Linear interpolation compensation model for angle measurement error:

[0131] (10)

[0132] in, for Dot at The relative error value at the point, In the coordinate system after data integration The position is the angular position, and N is the sequence number of the data point after data integration.

[0133] Angle measurement error harmonic error compensation model:

[0134] (11)

[0135] in, for Dot at The relative error value at the point, Let k be the angular position in the coordinate system after data integration, and k be the harmonic order of the angular measurement error. The phase angle of each harmonic error, The amplitude of each harmonic error is given.

[0136] To establish a harmonic compensation model for angle measurement errors, it is first necessary to perform a Fourier transform on the angle measurement error to extract the amplitude and phase of each harmonic. Therefore, it is crucial to ensure the equal intervals of the data at each calibration point. However, after adjusting the eccentricity of the polyhedron, the angle often shifts slightly in the vicinity. In this case, a high-precision grating in the compensation device is needed to correct the starting point position value. Simultaneously, linear interpolation is used to set the x-coordinate values ​​of the calibration points to equal intervals, and the corresponding y-values ​​are obtained and substituted into the calibration data.

[0137] The circular grating angle encoder is compensated by a linear interpolation compensation model and a harmonic compensation model for the angle measurement error. The relative rotation angle of the shaft system is used as the x-value and substituted into the error compensation model. The measured relative rotation angle of the shaft system is then corrected, and the compensated angle measurement value is output.

[0138] Please see Figure 6 , Figure 7 and Figure 8 In experimental verification, eight reading heads were evenly distributed and installed on the circumference of a Renishaw RCDM series glass circular grating (nominal marking accuracy of ±2.78″). The shaft system was connected to a motor, and motion control was performed using a high-precision Heidenhain RON886 as feedback, enabling a positioning accuracy of ±1″. Calibration was performed using an Automer photoelectric autocollimator, and the angular measurement accuracy within the ±100″ range reached 0.1″.

[0139] Based on the experimental results, the PV value of the angle measurement error of the circular grating encoder without data amplification compensation is 2.37″, while the PV value of the circular grating encoder with data amplification compensation via linear interpolation is 0.89″. By adopting this data amplification and integration method, the error compensation effect is significantly increased by using linear interpolation. The PV value of the angle measurement error of the four-readhead layout encoder is compensated to 0.67″, an improvement of 1.7″; the PV value of the angle measurement error of the eight-readhead layout encoder is compensated to 0.52″, an improvement of 0.37″. Under the harmonic error compensation algorithm, the PV value of the angle measurement error of the four-readhead layout encoder is compensated to 1.08″, an improvement of 1.29″; and the PV value of the angle measurement error of the eight-readhead layout encoder is compensated to 0.67″, an improvement of 0.22″. In summary, based on the harmonic characteristics of the angle measurement error, error calibration is achieved using an opto-autocollimator and a multifaceted prism. By subdividing the calibration interval through rotation of the multifaceted prism, more error data is obtained within the entire circumference of the code disk. Combining the angle measurement error characteristics of the circular grating angle encoder, multiple sets of calibration data are integrated. Using the integrated data, high-precision compensation of the angle measurement error of the circular grating angle encoder under a multi-readhead layout is achieved through linear interpolation compensation and harmonic error compensation.

[0140] In summary, the present invention provides an encoder calibration data amplification and error compensation method and apparatus, which utilizes the harmonic characteristics of angle measurement error to improve the angle measurement accuracy of a circular grating with a multi-reading head evenly distributed layout, and establishes a method and compensation approach for integrating circular grating calibration data under a multi-reading head layout. A high-precision autocollimator was used to calibrate the circular grating encoder and acquire the corresponding calibration data. A data integration algorithm was then used to integrate the error data. Finally, an angle measurement error compensation model was established using the error data. Through error compensation, the uncompensated angle measurement error PV value of the circular grating encoder was 2.37″, while the uncompensated linear interpolation compensation value was 0.89″. This data amplification and integration method, using linear interpolation, significantly improved the error compensation effect. The angle measurement error PV value of the four-readhead encoder was compensated to 0.67″, an improvement of 1.7″; the angle measurement error PV value of the eight-readhead encoder was compensated to 0.52″, an improvement of 0.37″. Under the harmonic error compensation algorithm, the angle measurement error PV value of the four-readhead encoder was compensated to 1.08″, an improvement of 1.29″; and the angle measurement error PV value of the eight-readhead encoder was compensated to 0.67″, an improvement of 0.22″. In summary, based on the harmonic characteristics of angle measurement error, an encoder calibration data amplification and error compensation method based on harmonic analysis is adopted. An opto-collimator and a multifaceted prism are used to complete error calibration, and the calibration interval is subdivided by rotating the multifaceted prism, thus obtaining more error data within the entire circumference of the code disk. Combining the angle measurement error characteristics of the circular grating angle encoder, multiple sets of calibration data are integrated. Using the integrated data, through linear interpolation compensation and harmonic error compensation, high-precision compensation of the angle measurement error of the circular grating angle encoder in a multi-readhead layout can be achieved. This is of great significance for further improving the angle measurement accuracy of the circular grating angle encoder's angle measurement system.

[0141] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is merely an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit. Furthermore, the specific names of the functional units and modules are only for easy differentiation and are not intended to limit the scope of protection of this application. The specific working process of the units and modules in the above device can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0142] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0143] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0144] In the embodiments provided by this invention, it should be understood that the disclosed devices / terminals and methods can be implemented in other ways. For example, the device / terminal embodiments described above are merely illustrative. For instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another device, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0145] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0146] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0147] If the integrated module / unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the methods of the above embodiments can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or device capable of carrying the computer program code, a recording medium, a USB flash drive, a portable hard drive, a magnetic disk, an optical disk, a computer memory, or a read-only memory (ROM). Only memory (ROM), random access memory (RAM), electrical carrier signals, telecommunication signals, and software distribution media, etc.

[0148] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (devices), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0149] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0150] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1The steps of the function specified in one or more boxes.

[0151] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. An encoder calibration data augmentation and error compensation method, characterized in that, The method comprises the following steps: S1, angle measurement and collection of angle measurement data and calibration data are performed by using a plurality of uniformly arranged reading heads; S2, the calibration data obtained in step S1 is expanded by using a motion control system to complete the rotation of the prism; S3, the calibration data obtained in step S2 is integrated according to the harmonic characteristics of the angle measurement data, an angle encoder angle measurement error compensation model is established, and the angle encoder angle measurement error compensation model adopts an angle measurement error linear interpolation compensation model, and the specific process is as follows: wherein, is the angular position of the data point at the position in the coordinate system after data integration is completed, N is the data point number after data integration is completed, is the angular position of the data point at the position N in the coordinate system after data integration is completed. The angle encoder angle measurement error compensation model adopts an angle measurement error harmonic error compensation model, and the specific process is as follows: wherein, is the angular position in the coordinate system of the data integration completion, k is the harmonic order of the angle measurement error, is the phase angle of each harmonic error, is the amplitude of each harmonic error; S4, the error data integrated in step S3 is brought into the angle encoder angle measurement error compensation model established in step S3 to perform angle measurement error compensation, and encoder angle measurement error compensation based on a plurality of reading head arrangements is realized.

2. The encoder calibration data amplification and error compensation method of claim 1, wherein, In step S1, the plurality of reading heads are uniformly arranged on the circumference of the encoder, the multi-faceted prism and the encoder grating disc are coaxially installed with the shaft system and are spaced apart to rotate on the air floating shaft system, the eccentricity of the multi-faceted prism is controlled within 2μm, the encoder angle measurement data is output by the plurality of uniformly arranged reading heads, and the calibration data is output by reading of a calibration device composed of a collimator and the multi-faceted prism.

3. The encoder calibration data amplification and error compensation method of claim 1, wherein, In step S2, after completing a set of calibration, control motor rotation And lock the motor, re-adjust the polyhedral, turn the polyhedral to 1 / 3 of the rotation interval, make the polyhedral align with the photoelectric autocollimator, complete the rotation after adjusting the polyhedral eccentricity, control the polyhedral eccentricity within 2μm, re-align the autocollimator instrument to calculate the polyhedral rotation angle value, the angle value is read by high-precision grating, and the rotation calibration step is executed again to complete the acquisition and calculation of multiple sets of error data.

4. The encoder calibration data amplification and error compensation method of claim 1, wherein, In step S3, the data integration specifically includes: The plurality of groups of data before and after the rotation of the multi-faceted prism are averaged to obtain the average value of the calibration data after each rotation of the multi-faceted prism, and the amplitude and phase of the 0-order harmonic error of each group of data are extracted by using Fourier transform; The plurality of groups of angle measurement error data are combined in the same coordinate system to complete the processing and integration of the error data by eliminating the 0-order harmonic error.

5. The encoder calibration data amplification and error compensation method of claim 4, wherein, When the multi-faceted prism is rotated each time, the radial runout of the multi-faceted prism is adjusted again, and when the calibration is performed, the horizontal axis value of the collimator is controlled within the range of ±10″.

6. The encoder calibration data amplification and error compensation method of claim 4, wherein, Relative angle measurement error of angular encoder in absolute coordinate system after data integration is: Wherein, The DC component amplitude of the harmonic component of the angle encoder error, The phase size of the DC component, The relative angle error measured by the angle encoder in a certain coordinate system when taking The origin as the starting point, The random error in the angle error.

7. The encoder calibration data amplification and error compensation method of claim 1, wherein, In step S4, the integrated error compensation data is brought into the angle encoder angle measurement error compensation model, the error curve is fitted according to the error data, the corresponding rotation angle-relative error relationship is obtained, the corresponding rotation angles measured by the plurality of reading heads are input, the error values near the rotation angle position are obtained, the error values are compensated, and the circular grating angle value is obtained by correction.

8. An encoder calibration data augmentation and error compensation apparatus, characterized by, It comprises: a data module, which is configured to perform angle measurement and collect angle measurement data and calibration data by using a plurality of uniformly arranged reading heads; an expansion module, which is configured to complete the rotation of the prism by using a motion control system and expand the calibration data obtained by the data module; an integration module, which is configured to integrate the calibration data obtained by the expansion module according to the harmonic characteristics of the angle measurement data, establish an angle encoder angle measurement error compensation model, and adopt an angle measurement error linear interpolation compensation model for the angle encoder angle measurement error compensation model, and the specific process is as follows: wherein, is the angular position of the data point at position , N is the data point number after data integration is completed, is the angular position of the data point at position N . The angle encoder angle measurement error compensation model adopts an angle measurement error harmonic error compensation model, and the specific process is as follows: wherein, is the angular position in the coordinate system of the data integration completion, k is the harmonic order of the angle measurement error, is the phase angle of each harmonic error, is the amplitude of each harmonic error; a compensation module, which is configured to bring the error data integrated by the integration module into the angle encoder angle measurement error compensation model established by the integration module to perform angle measurement error compensation, and realize encoder angle measurement error compensation based on a plurality of reading head arrangements.

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