A method for measuring the diameter of a cylindrical battery core

Abstract

This invention relates to the field of battery core measurement technology, specifically to a method for measuring the diameter of cylindrical battery cores. In use, this invention employs a 360° uniform 9-point sampling mode with static pauses to capture the entire circumference of the core without blind spots. This solves the problems of insufficient coverage and missed defects in traditional single-point measurements. Through multi-point uniform sampling, the maximum and minimum diameter data of the core can be completely captured, providing a complete data foundation for subsequent contour deviation analysis and significantly improving the comprehensiveness of defect identification. A four-parameter linkage judgment system based on average diameter, diameter range, extreme dimensions, and ellipticity is constructed, breaking through the industry's reliance on a single diameter dimension to determine good products. By independently constructing a proprietary ellipticity verification formula, the digitization, standardization, and quantification of core elliptic deformation are achieved, accurately identifying minor ellipticity, local diameter deviations, and local bulges that traditional methods cannot detect.

Description

Technical Field

[0001] This invention relates to the field of battery core measurement technology, and specifically to a method for measuring the diameter of cylindrical battery cores. Background Technology

[0002] After the cylindrical lithium battery core is wound and formed, its outer diameter and roundness accuracy directly determine the subsequent cell assembly accuracy and battery safety performance. If the core has defects such as out-of-tolerance outer diameter, elliptical deformation, local bulges, or local diameter deviation, it can easily cause cell jamming during assembly, casing deformation, and electrode misalignment. In severe cases, it can lead to quality problems such as micro-short circuits and excessive self-discharge. Therefore, the inspection of the core's outer diameter and contour accuracy is an indispensable key process in battery production.

[0003] Currently, the industry commonly uses single-point laser ranging or single-scan visual diameter measurement for cylindrical core size inspection. This method can only obtain the cross-sectional diameter data of a single angle of the core and uses this single point data as the basis for judging the entire roll. This type of traditional inspection method has obvious technical defects: First, single-point measurement cannot cover the 360° full circumference of the core, resulting in extremely poor identification of non-uniform deformation defects such as slight ellipticity, local bulges, and local diameter deviations commonly found in production, leading to a high rate of missed defects. Second, traditional measurement methods cannot quantify the degree of ellipticity of the core, relying solely on a fixed diameter tolerance for single-dimensional judgment, which cannot characterize the overall roundness quality of the core. Third, the production line presents complex interference conditions such as equipment vibration, dust obstruction, and significant differences in reflectivity between copper foils and the black film on the core surface, resulting in poor imaging stability of traditional acquisition methods and further reducing detection accuracy.

[0004] Traditional testing methods can only determine the size at a single point and cannot quantify the uniformity of the core outline. As a result, a large number of cores with qualified apparent dimensions but hidden outline defects flow into the assembly process, causing quality problems such as poor batch packaging and micro short circuits in the battery cells. As a result, it is difficult to improve the product yield and production stability. Summary of the Invention

[0005] This invention addresses the industry pain points of existing laser beam measurement and perimeter conversion measurement methods, such as inaccurate measurement of elliptical cells, missed detection of local defects, large interference under working conditions, and poor stability, through a complete set of technical solutions including core lifting to isolate vibration, V-groove centering positioning, equal-angle step-pause shooting, multi-parameter algorithm calculation, ellipticity verification, and four-parameter linkage judgment. It effectively improves the accuracy and reliability of cylindrical battery core diameter and roundness detection.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a method for measuring the diameter of cylindrical battery cores. This method utilizes a specialized measuring mechanism assembled from a measuring bracket, a lifting cylinder, a support base, a cylindrical battery core, a CCD industrial camera, a rotary motor, and a fixed rotating roller to automate the inspection process. The method includes the following steps: S1. Precise positioning and lifting: The cylindrical battery core to be inspected flows to the fixed inspection station along the production line. The lifting cylinder vertically drives the support base to lift upward, lifting the cylindrical battery core as a whole off the production line conveyor surface, preventing inspection interference caused by vibration and running deviation of the conveying equipment. S2, Full-circumferential equal-angle stepping imaging and positioning: The rotary motor provides rotational power, driving the fixed rotary roller to rotate synchronously. Relying on the friction of the roller surface, the cylindrical battery core placed in contact with the roller is driven to perform a 360° circumferential equal-angle stepping rotational motion. After the core completes a precise rotation of a preset angle, it pauses briefly. The CCD industrial camera maintains a fixed shooting angle and height to perform fixed-point high-definition image acquisition of the radial contour of the outer circumference of the core, completing multiple sets of contour image sampling of the entire circumference of the core without dead angles. S3. Multi-dimensional intelligent data processing: High-precision visual edge recognition and contour fitting processing are performed on the multi-frame core outline images acquired by the CCD industrial camera to accurately extract the core cross-sectional diameter value corresponding to each frame image. S4. Four-parameter linkage comprehensive good product judgment: The four parameters obtained by calculation, namely the average diameter of the core, the diameter range, the maximum diameter and the minimum diameter, are compared with the corresponding core process threshold preset by the system. Combined with the dual judgment logic of size deviation and elliptical deformation, the system comprehensively judges whether the outer diameter accuracy and circular forming status of the current cylindrical battery core are qualified.

[0007] Furthermore, in step S1, a V-shaped limiting groove structure is provided on the top of the bearing base, which, together with the fixed rotating rollers arranged symmetrically and parallel on the left and right sides, performs bidirectional bonding and limiting of the core, thereby realizing automatic centering and correction of the cylindrical battery core and limiting radial offset and horizontal movement during the core detection process.

[0008] Furthermore, in step S2, the single step rotation angle of the core is set to 36°, which corresponds to the core completing 9 fixed-point image acquisitions evenly in the 360° full circumference, i.e., the effective number of acquisitions n=9; the 9 sampling points are evenly distributed on the entire outer periphery of the core, with no acquisition blind spots and no point offset, realizing full coverage data acquisition of elliptical cores and locally bulging cores; After each equiangular step rotation, the core is forced to pause for 0.2s to 0.5s. Once the cylindrical battery core is completely still and the slight swaying and positional shift caused by rotational inertia are eliminated, the CCD industrial camera is triggered to perform the image acquisition action. This effectively avoids image ghosting and blurring caused by dynamic shooting during rotation, ensuring that the edge contours of each acquired image are clear and complete, providing a reliable image basis for high-precision diameter measurement.

[0009] Furthermore, this method incorporates a dedicated intelligent algorithm for core ellipticity verification, used to quantitatively determine the degree of core elliptic deformation and accurately identify minor deformation defects that cannot be detected by traditional single diameter measurement methods. The formula for calculating the ellipticity E is as follows: , In the formula, The average diameter, This represents the maximum diameter of the core. The minimum diameter is used to determine the ellipticity value by matching it with a preset ellipticity threshold. When the ellipticity E is less than or equal to the preset threshold, the roundness of the core is deemed to be qualified. When the ellipticity E exceeds the preset threshold, the core is accurately determined to have elliptical deformation, local thickening or thinning forming defects.

[0010] Furthermore, the fixed rotating roller adopts a left-right symmetrical double roller parallel limiting structure. The distance between the double rollers is adapted to the outer diameter of the corresponding cylindrical core. During the detection process, the double rollers simultaneously adhere to the outer walls on both sides of the core to form a stable support structure. During the core's stepping rotation, the position of the core's center is always constrained to remain constant, preventing radial runout and eccentric offset problems generated during the core's rotation, and ensuring the consistency and accuracy of the sampling data.

[0011] Furthermore, in step S3, four detection parameters are calculated based on multiple sets of effective diameter data: maximum diameter, minimum diameter, average diameter, and diameter range. The formulas for calculating the average diameter and diameter range are as follows: , In the formula, Where n is the average diameter, and n is the total number of effective shots taken in the 360° circumference of the core. Let be the diameter value of the core cross-section obtained from the i-th fixed-point acquisition. Diameter range This represents the maximum diameter of the core. To minimize the diameter, the measuring bracket (1) is used to fix and support the CCD industrial camera (5), so that the camera lens is directly facing the axial center of the cylindrical battery core (4), and the image collected is the standard radial section of the core, thus avoiding the diameter measurement error caused by the shooting angle deviation.

[0012] Furthermore, the judgment logic in step S4 is as follows: when the maximum and minimum diameter values ​​fall within the preset diameter tolerance range, and the diameter range and core ellipticity are both less than or equal to the corresponding preset thresholds, the core size and forming state are judged to be qualified; if any parameter exceeds the preset threshold, the core is judged to have dimensional deviation, elliptic deformation or local bulging defects, and is judged to be a defective product.

[0013] Furthermore, the rotary motor is a stepper servo motor with a repeatability control accuracy of ≤±0.5°. The rotary motor precisely controls the rotation stroke and start / stop position of the fixed rotary roller, ensuring that the core rotates at the same angle each time. The sampling points are evenly distributed on the outer periphery of the core, preventing data distortion caused by concentrated or missing points.

[0014] Furthermore, in step S3, the original diameter data is preprocessed by using median filtering to remove noise and outliers, and abnormal data caused by workshop vibration, dust, and image noise are screened out, thereby improving the stability and accuracy of the diameter detection data.

[0015] Furthermore, the CCD industrial camera is equipped with an adaptive auxiliary light source, which is a ring light source or a coaxial light source. The light source adaptively adjusts the brightness, exposure time and contrast according to the reflective characteristics of the cylindrical battery core surface material, overcoming the interference of workshop dust, high reflectivity of copper foil and low reflectivity of black film, ensuring clear imaging of the core outline and improving the accuracy of visual recognition and diameter measurement. Beneficial effects

[0016] Compared with known public technologies, the technical solution provided by this invention has the following beneficial effects: This invention employs a 360° uniform 9-point sampling and static pause sampling mode to achieve blind-spot-free acquisition of the entire circumference contour of the roll core. This solves the problems of insufficient coverage and missed detection of local defects inherent in traditional single-point measurements. Through multi-point uniform sampling, it can completely capture the maximum and minimum diameter data of the roll core, providing a complete data foundation for subsequent contour deviation analysis and significantly improving the comprehensiveness of defect identification. It constructs a four-parameter linkage judgment system based on average diameter, diameter range, extreme dimensions, and ellipticity, breaking through the industry's single-criteria judgment logic that relies solely on diameter size to determine good products. By independently developing a proprietary ellipticity verification formula, it achieves digital, standardized, and quantitative judgment of roll core elliptic deformation, accurately identifying minor ellipticity, local diameter deviation, and local bulges that traditional methods cannot detect. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the diameter measuring mechanism in the cylindrical battery core diameter measuring method of the present invention.

[0018] Figure 2This is a schematic diagram of the angle measurement structure in the cylindrical battery core diameter measurement method of the present invention.

[0019] Figure 3 This is a line graph comparing the defective core rounding rate in the embodiments.

[0020] Explanation of the labels in the diagram: 1. Measuring bracket; 2. Lifting cylinder; 3. Support base; 4. Cylindrical battery core; 5. CCD industrial camera; 6. Rotary motor; 7. Fixed rotating roller. Detailed Implementation

[0021] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0022] Example Please see Figures 1-2 This invention discloses a method for measuring the diameter of cylindrical battery cores, which is suitable for online inspection scenarios in automated production lines. The inspection operation is completed by a dedicated measuring mechanism consisting of a measuring bracket 1, a lifting cylinder 2, a bearing base 3, a cylindrical battery core 4, a CCD industrial camera 5, a rotary motor 6, and a fixed rotating roller 7.

[0023] Please see Figures 1-2 In one embodiment, S1, precise positioning and lifting: the cylindrical battery core 4 to be inspected flows to the fixed inspection station along the production line, the lifting cylinder 2 vertically drives the bearing base 3 to lift upward, lifting the cylindrical battery core 4 as a whole away from the production line conveyor surface, preventing inspection interference caused by vibration and running deviation of the conveying equipment.

[0024] Furthermore, the top of the support base 3 is equipped with a V-shaped limiting groove structure, which, together with the fixed rotating rollers 7 arranged symmetrically and parallel on the left and right sides, performs bidirectional bonding and limiting of the core, realizing automatic centering and correction of the cylindrical battery core 4, and limiting radial offset and horizontal movement during the core detection process.

[0025] S2, Full-circumferential equal-angle stepping imaging and positioning: The rotary motor 6 provides rotational power, driving the fixed rotary roller 7 to operate synchronously. Relying on the friction of the roller surface, the cylindrical battery core 4 placed in contact with the roller is driven to perform a 360° circumferential equal-angle stepping rotational motion. After the core completes a precise rotation of a preset angle, it pauses briefly. The CCD industrial camera 5 maintains a fixed shooting angle and height to perform fixed-point high-definition image acquisition of the radial contour of the outer circumference of the core, completing multiple sets of contour image sampling of the entire circumference of the core without dead angles.

[0026] Furthermore, the single-step rotation angle of the core is set to 36°, corresponding to 9 fixed-point image acquisitions uniformly completed in the 360° full circumference of the core, that is, the effective number of acquisitions n=9; the 9 sampling points are evenly distributed on the entire outer perimeter of the core, with no acquisition blind spots and no point offset, realizing full coverage data acquisition of elliptical cores and locally bulging cores.

[0027] Furthermore, after each equiangular step rotation, the core is forced to pause for 0.2s to 0.5s. Once the cylindrical battery core 4 is completely still and the slight shaking and positional shift caused by rotational inertia are eliminated, the CCD industrial camera 5 is triggered to perform the image acquisition action. This effectively avoids image ghosting and blurring caused by rotational dynamic shooting, ensuring that the edge contours of each acquired image are clear and complete, providing a reliable image basis for high-precision diameter measurement.

[0028] Specifically, the CCD industrial camera 5 is equipped with an adaptive auxiliary light source, which is either a ring light source or a coaxial light source. The light source adaptively adjusts the brightness, exposure time and contrast according to the reflective characteristics of the surface material of the cylindrical battery core 4, overcoming the interference of workshop dust, high reflectivity of copper foil and low reflectivity of black film, ensuring clear imaging of the core outline and improving the accuracy of visual recognition and diameter measurement.

[0029] S3. Multi-dimensional intelligent data processing: High-precision visual edge recognition and contour fitting processing are performed on the multi-frame core outline images acquired by the CCD industrial camera 5 to accurately extract the core cross-sectional diameter value corresponding to each frame image.

[0030] Furthermore, before data processing, the system first performs median filtering and outlier removal on the original diameter data to eliminate abnormal data caused by slight vibrations, dust, and image noise in the workshop, thereby improving the stability of the detection data. Then, the system uses a built-in statistical algorithm to calculate and obtain the four core detection parameters: maximum diameter, minimum diameter, average diameter, and diameter range. The calculation formulas are as follows: , In the formula, Where n is the average diameter, and n is the total number of effective shots taken in the 360° circumference of the core. Let be the diameter value of the core cross-section obtained from the i-th fixed-point acquisition. Diameter range This represents the maximum diameter of the core. This is the minimum diameter.

[0031] This method incorporates a proprietary intelligent algorithm for core ellipticity verification, used to quantitatively determine the degree of core elliptic deformation and accurately identify minor deformation defects that cannot be detected by traditional single diameter measurement methods. The formula for calculating ellipticity E is as follows: , In the formula, The average diameter, This represents the maximum diameter of the core. The minimum diameter is used to determine the ellipticity value by matching it with a preset ellipticity threshold. When the ellipticity E is less than or equal to the preset threshold, the roundness of the core is deemed to be qualified. When the ellipticity E exceeds the preset threshold, the core is accurately determined to have elliptical deformation, local thickening or thinning forming defects.

[0032] Specifically, relying on a single point diameter value to determine whether a product is good or not is insufficient because single-point data cannot characterize the overall outline of the core. It cannot identify minor defects such as slight ellipticity, local bulges, and local diameter deviations that are common in production. This results in a large number of cores with acceptable apparent dimensions but out-of-tolerance actual outlines flowing into the assembly process, causing quality hazards such as jamming during casing insertion, casing deformation due to compression, and micro-short circuits in the battery cells. By statistically solving the average diameter and range parameters through multiple sets of sampling data, the overall dimensional deviation and outline unevenness of the core can be fully quantified. Compared with single-point measurement methods, it has the advantage of comprehensive detection.

[0033] S4. Four-parameter linkage comprehensive good product judgment: The four parameters obtained by calculation, namely the average diameter of the core, the diameter range, the maximum diameter and the minimum diameter, are compared with the corresponding core process threshold preset by the system. Combined with the dual judgment logic of size deviation and elliptical deformation, the outer diameter accuracy and circular forming status of the current cylindrical battery core 4 are comprehensively judged to determine whether they are qualified.

[0034] The further judgment logic is as follows: when the maximum and minimum diameter values ​​fall within the preset diameter tolerance range, and the diameter range and core ellipticity are both less than or equal to the corresponding preset thresholds, the core size and forming state are judged to be qualified; if any parameter exceeds the preset threshold, the core is judged to have dimensional deviation, elliptic deformation or local bulging defects, and is judged to be a defective product.

[0035] It should be noted that the single-step rotation angle of 36° and the number of sampling steps n=9 set in this embodiment are only preferred options. In practical applications, the step angle can also be set to 18°, 10° or other angles according to different detection accuracy requirements, and the corresponding number of sampling steps n will also be adjusted accordingly. Any detection logic that uses a rotating roller to drive the core to perform multi-angle pause sampling falls within the protection scope of this invention.

[0036] To verify the actual detection effect of this method, two production lines were selected for comparative testing under the same batch and process conditions: Line C used the equal-angle CCD detection + four-parameter linkage judgment method of this invention, while Line D used the traditional single-point laser diameter detection method. The defective core roundness rate was continuously counted for 30 shifts, and the comparison results are as follows: Figure 3 As shown in the figure, the defect rate of line D, which uses the traditional detection method, has been consistently low, even reaching 0% in some shifts. It cannot identify hidden contour defects such as ovals and localized bulges, resulting in a large number of defective cores flowing into subsequent assembly processes. In contrast, line C, which uses the method of this invention, has a slightly higher defect rate during the initial equipment debugging phase. After the equipment stabilizes, the defect rate is consistently controlled within the range of 0.5% to 1.0%, indicating that this method can effectively identify contour defects that traditional methods cannot detect, intercepting and removing hidden defective cores in advance.

[0037] Subsequent assembly process verification showed that the C line using the method of this invention had a core insertion defect rate that was more than 90% lower than that of the D line, and a cell micro-short circuit defect rate that was more than 85% lower. This achieved unexpected technical results that exceeded conventional testing methods, fully demonstrating the significant advantages of the method of this invention in terms of the comprehensiveness of defect identification and the accuracy of detection.

[0038] In the above embodiments, the lifting cylinder 2 can also be replaced by other linear drive mechanisms such as electric push rods or lead screw modules; the CCD industrial camera 5 can also be replaced by a CMOS camera or other high-resolution vision sensors. These simple replacements of conventional technical means do not affect the implementation of the core measurement method of this invention and are also within the protection scope of this invention.

[0039] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for measuring the diameter of a cylindrical battery core, characterized in that, This method relies on a dedicated measuring mechanism assembled from a measuring bracket (1), a lifting cylinder (2), a bearing base (3), a cylindrical battery core (4), a CCD industrial camera (5), a rotary motor (6), and a fixed rotating roller (7) to complete automated testing operations, including the following steps: S1. Precise positioning and lifting: The cylindrical battery core (4) to be inspected is transferred to the fixed inspection station along with the production line. The lifting cylinder (2) vertically drives the bearing base (3) to lift upward, lifting the cylindrical battery core (4) as a whole away from the production line conveyor surface. S2, Full Circumferential Equal Angle Stepping Shooting and Positioning: The rotary motor (6) provides rotational power to drive the fixed rotary roller (7) to operate synchronously. Relying on the friction of the roller surface, the cylindrical battery core (4) placed in contact with the roller is driven to perform a 360° circumferential equal angle stepping rotation. After the core completes a precise rotation of a preset angle, it pauses briefly. The CCD industrial camera (5) maintains a fixed shooting angle and height to perform fixed-point high-definition image acquisition of the radial contour of the outer circumference of the core, and completes multiple sets of contour image sampling of the entire circle of the core without dead angles. S3, Multi-dimensional data intelligent operation and processing: High-precision visual edge recognition and contour fitting processing are performed on the multi-frame core outline images acquired by the CCD industrial camera (5) to accurately extract the core cross-sectional diameter value corresponding to each frame image. S4. Four-parameter linkage comprehensive good product judgment: The four parameters obtained by calculation, namely the average diameter of the core, the diameter range, the maximum diameter and the minimum diameter, are compared with the corresponding core process threshold preset by the system. Combined with the dual judgment logic of size deviation and elliptical deformation, the outer diameter accuracy and circular forming state of the current cylindrical battery core (4) are comprehensively judged to determine whether they are qualified.

2. The method for measuring the diameter of a cylindrical battery core according to claim 1, characterized in that, In step S1, the top of the bearing base (3) is provided with a V-shaped limiting groove structure, which, together with the fixed rotating rollers (7) arranged symmetrically on the left and right sides, performs bidirectional bonding and limiting of the core, thereby realizing the automatic centering and correction of the cylindrical battery core (4) and limiting the radial offset and horizontal movement during the core detection process.

3. The method for measuring the diameter of a cylindrical battery core according to claim 1, characterized in that, In step S2, the single step rotation angle of the roll core is set to 36°, which corresponds to the roll core completing 9 fixed-point image acquisitions evenly in the 360° full circumference, that is, the effective number of acquisitions n=9; the 9 sampling points are evenly distributed on the entire outer periphery of the roll core, with no acquisition blind spots and no point offset, realizing full coverage data acquisition of elliptical roll cores and locally bulging roll cores; After the core completes one equal-angle step rotation, it is forced to pause for 0.2s to 0.5s. After the cylindrical battery core (4) is completely still and the slight shaking and positional shift caused by rotational inertia are eliminated, the CCD industrial camera (5) is triggered to perform the photo acquisition action. This effectively avoids the image ghosting and outline blurring problems caused by rotational dynamic shooting, and ensures that the edge outline of each acquired image is clear and complete, providing a reliable image basis for high-precision diameter measurement.

4. The method for measuring the diameter of a cylindrical battery core according to claim 1, characterized in that, This method incorporates a proprietary intelligent algorithm for core ellipticity verification, used to quantitatively determine the degree of core elliptic deformation and accurately identify minor deformation defects that cannot be detected by traditional single diameter measurement methods. The formula for calculating the ellipticity E is as follows: ， In the formula, The average diameter, This represents the maximum diameter of the core. The minimum diameter is used to determine the ellipticity value by matching it with a preset ellipticity threshold. When the ellipticity E is less than or equal to the preset threshold, the roundness of the core is deemed to be qualified. When the ellipticity E exceeds the preset threshold, the core is accurately determined to have elliptical deformation, local thickening or thinning forming defects.

5. The method for measuring the diameter of a cylindrical battery core according to claim 1, characterized in that, The fixed rotating roller (7) adopts a left-right symmetrical double roller parallel limiting structure. The distance between the double rollers is adapted to the outer diameter of the corresponding cylindrical core. During the detection process, the double rollers simultaneously adhere to the outer walls on both sides of the core to form a stable support structure. During the core's step-rotation process, the core's center position is always constrained to remain constant.

6. The method for measuring the diameter of a cylindrical battery core according to claim 1, characterized in that, In step S3, four detection parameters are calculated based on multiple sets of effective diameter data: maximum diameter, minimum diameter, average diameter, and diameter range. The formulas for calculating the average diameter and diameter range are as follows: ， In the formula, Where n is the average diameter, and n is the total number of effective shots taken in the 360° circumference of the roll core. The value of the core cross-section diameter obtained from the i-th fixed-point acquisition is [value missing]. Diameter range This represents the maximum diameter of the core. To minimize the diameter, the measuring bracket (1) is used to fix and support the CCD industrial camera (5), so that the camera lens is directly facing the axial center of the cylindrical battery core (4), and the image collected is the standard radial section of the core, thus avoiding the diameter measurement error caused by the shooting angle deviation.

7. The method for measuring the diameter of a cylindrical battery core according to claim 1, characterized in that, The judgment logic in step S4 is as follows: when the maximum and minimum diameter values ​​fall within the preset diameter tolerance range, and the diameter range and core ellipticity are both less than or equal to the corresponding preset thresholds, the core size and forming state are judged to be qualified; if any parameter exceeds the preset threshold, the core is judged to have dimensional deviation, elliptic deformation or local bulging defects, and is judged to be a defective product.

8. The method for measuring the diameter of a cylindrical battery core according to claim 1, characterized in that, The rotary motor (6) is a stepper servo motor with a repeatability control accuracy of ≤ ±0.5°. The rotary motor (6) precisely controls the rotation stroke and start / stop position of the fixed rotary roller (7) to ensure that the core rotates at the same angle each time. The sampling points are evenly distributed on the outer periphery of the core to prevent data distortion caused by concentrated or missing points.

9. The method for measuring the diameter of a cylindrical battery core according to claim 1, characterized in that, In step S3, the original diameter data is preprocessed by using median filtering to remove noise and outliers, and abnormal data caused by workshop vibration, dust, and image noise are screened out, thereby improving the stability and accuracy of the diameter detection data.

10. The method for measuring the diameter of a cylindrical battery core according to claim 1, characterized in that, The CCD industrial camera (5) is equipped with an adaptive auxiliary light source, which is a ring light source or a coaxial light source. The light source adaptively adjusts the brightness, exposure time and contrast according to the reflective characteristics of the surface material of the cylindrical battery core (4), overcomes the interference of workshop dust, high reflectivity of copper foil and low reflectivity of black film, ensures clear imaging of the core outline, and improves the accuracy of visual recognition and diameter measurement.

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