A method for measuring the geometry of a ground high voltage cable joint

Abstract

The application discloses a kind of grinding high-voltage cable joint geometry size measurement method, comprising: S1, obtains the point cloud data of grinding high-voltage cable joint, and carries out pre-processing;S2, point cloud data is divided, and the centroid coordinate is calculated;S3, according to the distance between centroid coordinate and axis vector, the ratio of distance variance is calculated, cable joint structure segmentation is carried out and the length of axle section is measured;S4, according to the position of the surface element after division, the centroid point is matched, and the outer diameter and XY axis outer diameter deviation of each area measurement position of cable joint are measured.The application obtains the point cloud data of cable joint using three-dimensional laser scanner, can realize non-contact measurement, avoid damage to workpiece surface;Through point cloud preprocessing, the precision of subsequent segmentation and measurement is improved;Original polishing shape and defect characteristics are retained, the algorithm accuracy for actual polishing cable joint is improved, and the algorithm speed is improved using centroid as surface element key point to complete measurement.

Description

Technical Field

[0001] This invention belongs to the field of three-dimensional machine vision and non-contact measurement technology, specifically relating to a method for measuring the geometric dimensions of a polished high-voltage cable joint. Background Technology

[0002] With the rapid development of the power industry, the application scope of high-voltage cables is expanding, with increasing demand in scenarios such as new energy, high-speed railways, and smart grids. High-voltage cables play an indispensable role in power systems, crucial for their stable operation. However, due to limitations in manufacturing, transportation, and laying, the maximum manufacturing length of a single high-voltage cable is currently limited, typically to 10km. Therefore, to achieve long-distance power transmission, technicians need to remove the armor on-site and grind the main insulation and semi-conductive parts to create cable joints, connecting cables and between cables and electrical equipment. Since cable joints are often manually made outdoors, the grinding quality varies considerably, making them weak points in cable insulation and typical sites of operational failure. Currently, it is difficult to accurately measure the relevant geometric dimensions of on-site ground cable joints, leading to the connection of non-standard cable joints into the power system. These substandard joints, under prolonged exposure to high voltage, can cause insulation breakdown due to uneven current distribution, overheating, or discharge, resulting in power failures. Therefore, measuring the relevant parameters of laid ground high-voltage cable joints is crucial and of great significance for ensuring the safe and reliable operation of power systems.

[0003] Traditionally, the power industry uses contact tools such as steel rulers and vernier calipers to measure cable joint dimensions. This method generally suffers from low accuracy and efficiency, and is prone to damaging the cable joint surface, failing to meet measurement requirements. Therefore, to address the numerous problems associated with manual measurement, non-contact parameter measurement of cable joints based on machine vision technology is gaining increasing attention. This includes measurement technologies based on 2D machine vision, laser projection, and 3D point clouds, each with its own advantages and disadvantages.

[0004] (1) An automatic measurement algorithm for the diameter, thickness, and eccentricity of power cable cross-sections based on monocular vision is proposed. First, a camera captures the cross-sectional image. Then, edge contour detection and hierarchical segmentation are performed, and a fracture detection, grouping, and linear trend-based correction (LTBC) algorithm is proposed to refine the contour. Finally, the cross-sectional dimensions are measured by placing the image on a checkerboard plane with the cable cross-section plane. This measurement method has relatively fast camera capture and algorithm processing speed, but the accuracy may be affected by factors such as viewing angle, lens distortion, and ambient lighting.

[0005] (2) Based on two-dimensional vision measurement, the edge information of the image is first obtained through morphological operations, then the center of the circle is located by the tangent method, and then the measurement of parameters such as the cross-sectional diameter and insulation thickness of the cable is realized according to the linear mapping relationship. However, the measurement accuracy is affected by the limited field of view, and the algorithm is highly complex.

[0006] (3) Using a laser source and a charge-coupled device, an offset compensation measurement system is constructed through analytical geometry and spatial coordinate transformation to measure cable diameter parameters. This method using a laser source provides high-precision measurement of outer diameter, but it cannot measure length parameters.

[0007] (4) Use binocular reconstruction to obtain cable point cloud. Based on the three-dimensional laser point cloud, use the least squares method to perform cylindrical fitting to complete the axial segment measurement, cross-sectional roundness detection and outer diameter measurement of the cable joint. However, since the polished cable joint is usually not a standard cylinder, this fitting-based measurement algorithm will lose some accuracy.

[0008] (5) Based on the cable shape characteristics, the RANSAC algorithm is used to fit the regional point cloud to the cylindrical surface to determine the radius of the corresponding position. However, the measurement process uses multiple point clouds to fit the cylindrical surface, resulting in low measurement efficiency and low measurement accuracy for the polished cable joint.

[0009] In summary, current non-contact measurement algorithms based on machine vision have certain limitations, low efficiency, and insufficient robustness in measuring the geometric dimensions of cable joints. The main reason is that manually polished cable joints not only have various polishing defects and unclear area boundaries, making segmentation more difficult, but also the cable joints polished by different technicians vary greatly. Insufficient polishing results in an excessively large outer diameter, while excessive polishing results in an excessively small outer diameter, or even poor polishing quality leads to irregular shapes, affecting the algorithm's measurement of the true outer diameter. Summary of the Invention

[0010] In view of the above-mentioned shortcomings in the prior art, the method for measuring the geometric dimensions of grinding high-voltage cable joints provided by the present invention solves the problem of low measurement accuracy of existing non-contact measurement methods.

[0011] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows: a method for measuring the geometric dimensions of a high-voltage cable joint after grinding, comprising the following steps:

[0012] S1. Obtain point cloud data of the high-voltage cable joint being polished and preprocess it;

[0013] S2. Based on the radial and axial orientation of the cable axis, the preprocessed point cloud data is divided, and the centroid coordinates of the elements after division are calculated.

[0014] S3. Based on the distance between the centroid coordinates and the axis vector, calculate the ratio of the distance variance between the point of maximum distance jump and each centroid point, perform cable joint structure segmentation and measure the shaft segment length;

[0015] S4. Match the centroids based on the positions of the divided surface elements, and measure the outer diameter and XY axis outer diameter deviation of each area of ​​the cable joint by calculating the distance between the centroids.

[0016] Further, step S1 specifically includes:

[0017] S11. Use a 3D laser scanner to scan and obtain point cloud data of the high-voltage cable joint for grinding;

[0018] S12. Use statistical filters to filter out outliers during the scanning process;

[0019] S13. Extract the point cloud data of the main area of ​​the cable joint after outlier filtering and perform cylinder fitting;

[0020] S14. Use the cylindrical axis of the fitted cylinder as the axis of the cable connector;

[0021] S15. Perform a rotation and translation operation on the cable joint axis to make the cable joint axis coincide with the z-axis of its coordinate system. Then, perform a rotation and translation operation on the point cloud data and sort it by z-value to obtain the preprocessed point cloud data.

[0022] Furthermore, in step S12, the method for filtering out outliers is specifically as follows:

[0023] S12-1. Perform statistical analysis on the distances from each point to the point in its neighborhood k;

[0024] S12-2. Based on the distance statistical analysis, calculate the mean μ and standard deviation σ, set the standard deviation threshold std, and determine whether the average distance between a point and all points in its neighborhood k is within the range (μ–σ·std, μ+σ·std).

[0025] If so, then keep the point;

[0026] If not, then filter it out as an outlier.

[0027] Further, step S2 specifically includes:

[0028] S21. Starting from the XOZ plane of the cable axis, set the rotation angle increment Δθ, and divide and number the preprocessed point cloud data by determining the dividing point counterclockwise around the axis.

[0029] S22. Traverse the point cloud data within each numbered region and extract the point cloud of the arc region between the segmentation points;

[0030] S23. Using a plane perpendicular to the axis, set the sliding distance Δh to slide and divide the point cloud of the arc region in the axial direction, save the region point cloud, and calculate the centroid coordinates of the segmented surface elements.

[0031] Furthermore, in step S22, the formula for extracting the point cloud of the arc region between the segmentation points is:

[0032]

[0033]

[0034] In the formula, π represents the radian angle, n represents the segmentation number, and α i C represents the angle between the target point cloud and the axis. pi This represents the point cloud region that meets the conditions, (x i ,y i ,z i () represents the original point cloud coordinates;

[0035] In step S23, the formula for calculating the centroid coordinates of the surface element is:

[0036]

[0037]

[0038] In the formula, (x p ,y p ,z p W represents the point cloud coordinates of the segmented surface elements. l and W r C represents the z-coordinate values ​​of the starting and ending points corresponding to the sliding distance, respectively. (i,j) P represents the element number. c Indicates the coordinates of the centroid.

[0039] Further, step S3 specifically includes:

[0040] S31. Based on the standard parameters of the cable joint structure, extract the centroid points of the corresponding area, group the extracted centroid points according to the radial division angle using an axis-based rotation method, and calculate the distance from each centroid point p to the axis.

[0041] S32. Calculate the ratio of the distance variances corresponding to each centroid point in each group;

[0042] S33. Take the ratio of the minimum distance variance in each group as the segmentation position of the current group, traverse all groups, and sort them from smallest to largest to obtain the range of all segmentation positions to represent the overall axial segmentation, and segment the cable structure.

[0043] Furthermore, in step S31, the formula for calculating the distance d from the centroid p to the axis is:

[0044]

[0045] (a,b,c)=(x p -x0,y p -y0,z p -z0)

[0046] In the formula, (a,b,c) represents any centroid point (x) p ,y p ,z p The vector between (x0, y0, z0) and a point (x0, y0, z0) on the axis, where (m, n, p) represents the direction vector of the axis;

[0047] In step S33, the calculation formula for axial segmentation using a set of centroid points is as follows:

[0048]

[0049]

[0050]

[0051] In the formula, Seg1 represents the Z-coordinate value of the point where the distance jump is the largest corresponding to a set of centroid points in the structural region, and d p This represents the distance from the current centroid to the axis. and σ represents the average distance from the current centroid p to the axis of mass n points before and after it. s 2 (p) and σ e 2 (p) represents the distance variance of n points before and after the current centroid, and Seg2 represents the Z coordinate value when the ratio of the distance variances of a set of centroids in the corresponding structural region is minimized.

[0052] Further, step S4 specifically includes:

[0053] S41. Determine the measurement location and extract all slices along the corresponding axial direction.

[0054] S42. Select a face element as the initial block, find the corresponding face element that is rotated 180° counterclockwise in the radial direction and combine it with the face element. Calculate the Euclidean distance between the centroids of the two face elements. Traverse the remaining face elements to obtain the distance values ​​of all centroid pairs. Calculate the average value as the outer diameter of the current measurement position.

[0055] S43. Extract two pairs of mutually perpendicular centroid points based on the angular relationship, calculate their deviation values, traverse the remaining surface elements and sort them from smallest to largest, and take the maximum deviation value as the XY axis outer diameter deviation of the current measurement position.

[0056] Further, in step S42, the outer diameter at the current measurement position The calculation formula is:

[0057]

[0058] In the formula, n represents the number of face elements, (x i ,y i ,z i () represents the coordinates of the centroid of the surface element;

[0059] In step S43, the formula for calculating the XY axis outer diameter deviation at the current measurement position is:

[0060]

[0061] In the formula, n represents the number of face elements, p i Represents the coordinates of the centroid, |p i p i+(n / 2) | and |p i+(n / 4) p i+(n*3 / 4) | represents the distance between the centroids.

[0062] The beneficial effects of this invention are as follows:

[0063] (1) This invention uses a three-dimensional laser scanner to acquire point cloud data, realizing non-contact measurement of grinding high-voltage cable joints, avoiding damage to the workpiece surface.

[0064] (2) This invention designs filtering and point cloud ordering preprocessing modules to improve the efficiency and accuracy of subsequent 3D point cloud processing. This invention performs equal-angle radial segmentation and equal-distance axial segmentation based on the cable axis, preserving the defect information and features of the original point cloud, and can obtain data that is closer to reality.

[0065] (3) This invention uses the centroid of the segmented element to perform point-to-axis calculation and matching between centroids, which improves the efficiency of the algorithm and is applicable to cables with different polishing qualities, and has high robustness. Attached Figure Description

[0066] Figure 1 A flowchart of the method for measuring the geometric dimensions of a high-voltage cable joint for grinding, provided by the present invention.

[0067] Figure 2 This is an image showing the effect of point cloud ordering provided by the present invention.

[0068] Figure 3 A schematic diagram of the cable connector measurement parameters provided by the present invention.

[0069] Figure 4 A schematic diagram illustrating the splitting effect of a standard cable connector provided by this invention.

[0070] Figure 5 This is a schematic diagram illustrating the actual grinding joint segmentation effect provided by the present invention.

[0071] Figure 6 This is a schematic diagram of the measurement of outer diameter parameters provided by the present invention. Detailed Implementation

[0072] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0073] This invention provides a method for measuring the geometric dimensions of a high-voltage cable joint after grinding, such as... Figure 1 As shown, it includes the following steps:

[0074] S1. Obtain point cloud data of the high-voltage cable joint being polished and preprocess it;

[0075] S2. Based on the radial and axial orientation of the cable axis, the preprocessed point cloud data is divided, and the centroid coordinates of the elements after division are calculated.

[0076] S3. Based on the distance between the centroid coordinates and the axis vector, calculate the ratio of the distance variance between the point of maximum distance jump and each centroid point, perform cable joint structure segmentation and measure the shaft segment length;

[0077] S4. Match the centroids based on the positions of the divided surface elements, and measure the outer diameter and XY axis outer diameter deviation of each area of ​​the cable joint by calculating the distance between the centroids.

[0078] Step S1 in this embodiment of the invention is specifically as follows:

[0079] S11. Use a 3D laser scanner to scan and obtain point cloud data of the high-voltage cable joint for grinding;

[0080] S12. Use statistical filters to filter out outliers during the scanning process;

[0081] S13. Extract the point cloud data of the main area of ​​the cable joint after outlier filtering and perform cylinder fitting;

[0082] S14. Use the cylindrical axis of the fitted cylinder as the axis of the cable connector;

[0083] S15. Perform a rotation and translation operation on the cable joint axis to make the cable joint axis coincide with the z-axis of its coordinate system. Then, perform a rotation and translation operation on the point cloud data and sort it by z-value to obtain the preprocessed point cloud data.

[0084] In step S12 of this embodiment, the method for filtering out outliers is as follows:

[0085] S12-1. Perform statistical analysis on the distances from each point to the point in its neighborhood k;

[0086] S12-2. Based on the distance statistical analysis, calculate the mean μ and standard deviation σ, set the standard deviation threshold std, and determine whether the average distance between a point and all points in its neighborhood k is within the range (μ–σ·std, μ+σ·std).

[0087] If so, then keep the point;

[0088] If not, then filter it out as an outlier.

[0089] Specifically, in this embodiment, the three-dimensional point cloud data of the cargo is preprocessed. Due to factors such as equipment errors and changes in the surrounding environment, some noise points will inevitably appear, which will have a significant impact on the accuracy of subsequent parameter measurements. Therefore, filtering preprocessing is required before measurement. Since the filtered point cloud still has the characteristic of permutation invariance in the spatial coordinate system, that is, the point set is unordered, the cable joint point cloud also needs to be aligned after the filtering operation to facilitate the subsequent division of the effective area of ​​the point cloud. The basic principle is to perform a rotation and translation operation on the axis of the cable joint, that is, coordinate transformation, to make the axis coincide with the z-axis of its coordinate system.

[0090] In this embodiment, in step S12, when filtering out outliers, the number of neighboring points is set to 50, and the standard deviation factor is 1.0. First, the distance from each point to its neighboring points is calculated, and statistical analysis is performed to calculate the average μ and standard deviation σ of the distance from each point to its neighboring points. Then, the standard deviation factor is set to calculate the threshold D. th Determine the average distance d from any point to its neighboring points. p Is it less than D? th If the value is greater than 0, the point is considered an outlier and deleted. Finally, the above steps are repeated to traverse all points.

[0091] In this embodiment, during the point cloud ordering process in steps S13 to S15, the schematic diagram is as follows. Figure 2As shown, firstly, the point cloud of the insulation region is extracted and fitted into a cylinder. Then, the rotation vector R between the direction vector of the cylinder's axis and the unit direction vector of the z-axis of the spatial coordinate system is calculated, and the translation matrix T is calculated. The rotated axis is translated through the origin of the spatial coordinate system. Then, the point cloud coordinates are transformed to a new spatial coordinate system using the R and T matrices. Finally, the point cloud is sorted from smallest to largest according to the z-coordinate values ​​of the points, and the highest point of the cable joint is obtained.

[0092] Step S2 in this embodiment of the invention is specifically as follows:

[0093] S21. Starting from the XOZ plane of the cable axis, set the rotation angle increment Δθ, and divide and number the preprocessed point cloud data by determining the dividing point counterclockwise around the axis.

[0094] S22. Traverse the point cloud data within each numbered region and extract the point cloud of the arc region between the segmentation points;

[0095] S23. Using a plane perpendicular to the axis, set the sliding distance Δh to slide and divide the point cloud of the arc region in the axial direction, save the region point cloud, and calculate the centroid coordinates of the segmented surface elements.

[0096] In step S21 of this embodiment, when performing axial-based region segmentation, this embodiment sets the rotation angle increment to 5° and the sliding distance to 1mm. The axial vector of the cable connector is extracted, and a rotation angle increment is set in the radial direction of the axis. The segmentation is then performed by rotating counterclockwise around the axis. Next, the point cloud of the arc region between the segmentation points is extracted based on the judgment conditions. Then, a height threshold is set in the axial direction of the axis, and equidistant sliding segmentation is performed. Finally, all surface elements are obtained, and the centroid coordinates are obtained by averaging the coordinates of the point cloud on the surface element, replacing the entire surface element.

[0097] In step S22 of this embodiment, the formula for extracting the point cloud of the arc region between the segmentation points is:

[0098]

[0099]

[0100] In the formula, π represents the radian angle, n represents the segmentation number, and α i C represents the angle between the target point cloud and the axis. pi This represents the point cloud region that meets the conditions, (x i ,y i ,z i () represents the original point cloud coordinates;

[0101] In step S23 of this embodiment, the formula for calculating the centroid coordinates of the surface element is:

[0102]

[0103]

[0104] In the formula, (x p ,y p ,z p W represents the point cloud coordinates of the segmented surface elements. l and W r C represents the z-coordinate values ​​of the starting and ending points corresponding to the sliding distance, respectively. (i,j) P represents the element number. c Indicates the coordinates of the centroid.

[0105] Step S3 in this embodiment of the invention is specifically as follows:

[0106] S31. Based on the standard parameters of the cable joint structure, extract the centroid points of the corresponding area, group the extracted centroid points according to the radial division angle using an axis-based rotation method, and calculate the distance from each centroid point p to the axis.

[0107] S32. Calculate the ratio of the distance variances corresponding to each centroid point in each group;

[0108] S33. Take the ratio of the minimum distance variance in each group as the segmentation position of the current group, traverse all groups, and sort them from smallest to largest to obtain the range of all segmentation positions to represent the overall axial segmentation, and segment the cable structure.

[0109] In step S31 of this embodiment, according to the standard parameters of the cable connector structure, such as... Figure 3 As shown, the centroids of the corresponding regions are extracted. Based on the angle set by the radial division, the extracted centroids are grouped using an axis-based rotation method. The distance from each group of centroids to the axis is calculated. The formula for calculating the distance d from centroid p to the axis is:

[0110]

[0111] (a,b,c)=(x p -x0,y p -y0,z p -z0)

[0112] In the formula, (a,b,c) represents any centroid point (x) p ,y p ,z p The vector between (x0, y0, z0) and a point (x0, y0, z0) on the axis, where (m, n, p) represents the direction vector of the axis.

[0113] In step S32 of this implementation, the distance variances of the first n points and the last n points of each centroid point p in each group are calculated, and the ratio of the distance variances before and after is calculated.

[0114] In step S33 of this embodiment, the calculation formula for axial segmentation using a set of centroid points is as follows:

[0115]

[0116]

[0117]

[0118] In the formula, Seg1 represents the Z-coordinate value of the point where the distance jump is the largest corresponding to a set of centroid points in the structural region, and d p This represents the distance from the current centroid to the axis. and σ represents the average distance from the current centroid p to the axis of mass n points before and after it. s 2 (p) and σ e 2 (p) represents the distance variance of n points before and after the current centroid, and Seg2 represents the Z coordinate value when the ratio of the distance variances of a set of centroids in the corresponding structural region is minimized.

[0119] In this embodiment, based on the above segmentation method, the segmentation effect is as follows: Figure 4 and Figure 5 As shown,

[0120] like Figure 6 As shown, step S4 in this embodiment of the invention specifically includes:

[0121] S41. Determine the measurement location and extract all slices along the corresponding axial direction.

[0122] S42. Select a face element as the initial block, find the corresponding face element that is rotated 180° counterclockwise in the radial direction and combine it with the face element. Calculate the Euclidean distance between the centroids of the two face elements. Traverse the remaining face elements to obtain the distance values ​​of all centroid pairs. Calculate the average value as the outer diameter of the current measurement position.

[0123] S43. Extract two pairs of mutually perpendicular centroid points based on the angular relationship, calculate their deviation values, traverse the remaining surface elements and sort them from smallest to largest, and take the maximum deviation value as the XY axis outer diameter deviation of the current measurement position.

[0124] In step S42 of this embodiment, the outer diameter at the current measurement position... The calculation formula is:

[0125]

[0126] In the formula, n represents the number of face elements, (x i ,y i ,z i () represents the coordinates of the centroid of the surface element;

[0127] In step S43 of this embodiment, the formula for calculating the XY axis outer diameter deviation at the current measurement position is:

[0128]

[0129] In the formula, n represents the number of face elements, p i Represents the coordinates of the centroid, |p i p i+(n / 2) | and |p i+(n / 4) p i+(n*3 / 4) | represents the distance between the centroids.

[0130] Specific embodiments have been used to illustrate the principles and implementation methods of this invention. The descriptions of the embodiments above are only for the purpose of helping to understand the method and core ideas of this invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this invention. Therefore, the content of this specification should not be construed as a limitation of this invention.

[0131] Those skilled in the art will recognize that the embodiments described herein are intended to help the reader understand the principles of the invention, and should be understood that the scope of protection of the invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the technical teachings disclosed in this invention without departing from the spirit of the invention, and these modifications and combinations are still within the scope of protection of this invention.

Claims

1. A method for measuring the geometric dimensions of a high-voltage cable joint after grinding, characterized in that, Includes the following steps: S1. Obtain point cloud data of the high-voltage cable joint being polished and preprocess it; S2. Based on the radial and axial orientation of the cable axis, the preprocessed point cloud data is divided, and the centroid coordinates of the elements after division are calculated. S3. Based on the distance between the centroid coordinates and the axis vector, calculate the ratio of the distance variance between the point of maximum distance jump and each centroid point, perform cable joint structure segmentation and measure the shaft segment length; S4. Match the centroids based on the positions of the divided surface elements, and measure the outer diameter and XY axis outer diameter deviation of each area of ​​the cable joint by calculating the distance between the centroids. Step S1 specifically involves: S11. Use a 3D laser scanner to scan and obtain point cloud data of the high-voltage cable joint being polished; S12. Use statistical filters to filter out outliers during the scanning process; S13. Extract the point cloud data of the main area of ​​the cable joint after outlier filtering and perform cylinder fitting; S14. Use the cylindrical axis of the fitted cylinder as the axis of the cable connector; S15. Perform a rotation and translation operation on the cable joint axis to make the cable joint axis coincide with the z-axis of its coordinate system. Then, perform a rotation and translation operation on the point cloud data and sort it by z-value to obtain the preprocessed point cloud data. Step S2 specifically involves: S21. Taking the XOZ plane of the cable axis as the starting position, set the rotation angle increment Δ θ The preprocessed point cloud data is divided and numbered by determining the segmentation points counterclockwise around the axis; S22. Traverse the point cloud data within each numbered region and extract the point cloud of the arc region between the segmentation points; S23. Set the sliding distance using a plane perpendicular to the axis. The point cloud of the circular arc region is slidably segmented along the axial direction, the region point cloud is saved, and the centroid coordinates of the segmented surface elements are calculated. Step S3 specifically involves: S31. Based on the standard parameters of the cable joint structure, extract the centroids of the corresponding area. Group the extracted centroids according to the radial division angle using an axis-based rotation method, and calculate the centroids of each area. k Distance to the axis; S32. Calculate the ratio of the distance variances corresponding to each centroid point in each group; S33. Take the ratio of the minimum distance variance in each group as the segmentation position of the current group, traverse all groups, and sort them from smallest to largest to obtain the range of all segmentation positions to represent the overall axial segmentation, and segment the cable structure. Step S4 specifically involves: S41. Determine the measurement location and extract all slices along the corresponding axial direction. S42. Select a face element as the initial block, find the corresponding face element that is rotated 180° counterclockwise in the radial direction and combine it with the face element. Calculate the Euclidean distance between the centroids of the two face elements. Traverse the remaining face elements to obtain the distance values ​​of all centroid pairs. Calculate the average value as the outer diameter of the current measurement position. S43. Extract two pairs of mutually perpendicular centroid points based on the angular relationship, calculate their deviation values, traverse the remaining surface elements and sort them from smallest to largest, and take the maximum deviation value as the XY axis outer diameter deviation of the current measurement position.

2. The method for measuring the geometric dimensions of a high-voltage cable joint after grinding, as described in claim 1, is characterized in that... In step S12, the method for filtering out outliers is as follows: S12-1, Neighborhood of each point k Statistical analysis was performed on the distances from points in the array to this point. S12-2. Calculate the mean based on the distance statistical analysis. μ and standard deviation σ Set standard deviation threshold std Judgment point and its domain k Is the average distance of all points within the range ( μ – σ•std , μ + σ•std )Inside; If so, then keep the point; If not, then filter it out as an outlier.

3. The method for measuring the geometric dimensions of a high-voltage cable joint after grinding, as described in claim 1, is characterized in that... In step S22, the formula for extracting the point cloud of the arc region between the segmentation points is: In the formula, Indicates an angle in radians. Indicates the segmentation number, α i This represents the angle between the target point cloud and the axis. This represents the point cloud region that meets the criteria. x i , y i , z i () represents the original point cloud coordinates; x 0 and y 0 represents the intersection of the slice and the cable axis. x and y Coordinates of direction; In step S23, the formula for calculating the centroid coordinates of the surface element is: In the formula, ( x p , y p , z p () represents the point cloud coordinates of the segmented face elements. W l and W r These represent the z-coordinate values ​​of the starting and ending points corresponding to the sliding distance, respectively. C (i, j) Indicates the element number. P c Indicates the coordinates of the centroid.

4. The method for measuring the geometric dimensions of a high-voltage cable joint after grinding, as described in claim 1, is characterized in that... In step S31, the centroid point k Distance to the axis The calculation formula is: In the formula, ( a, b, c ) represents any centroid point ( x k , y k , z k ) and a point on the axis ( x 0, y 0, z Vectors between 0 and 0, ( m, l, k ) represents the direction vector of the axis; In step S33, the calculation formula for axial segmentation using a set of centroid points is as follows: In the formula, Seg 1 represents the location of the maximum distance jump corresponding to a set of centroids in the corresponding structural region. Z Coordinate values d p This represents the distance from the current centroid to the axis. and These represent the current centroid points. p front and back n The average distance from each point to the axis. and These represent the points before and after the current centroid. n The variance of the distance to each point Seg 2 indicates that the ratio of the distance variances corresponding to a set of centroids in the corresponding structural region is at its minimum. Z Coordinate values.

5. The method for measuring the geometric dimensions of a high-voltage cable joint by grinding according to claim 1, characterized in that, In step S42, the outer diameter at the current measurement position The calculation formula is: In the formula, n Indicates the number of face elements, ( x i , y i , z i ) represents the coordinates of the centroid of the surface element. x i+(n / 2) , y i+(n / 2) , z i+(n / 2) ) Surface element centroid i+(n / 2) The coordinates; In step S43, the formula for calculating the XY axis outer diameter deviation at the current measurement position is: In the formula, n Indicates the number of face elements. p i Indicates the coordinates of the centroid. and This represents the distance between the centroids. Represents the centroid of a surface element. i and center of mass i+(n / 2) distance, Represents the centroid of a surface element. i+(n / 4) and center of mass i + (n * 3 / 4) The correct distance.

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