阅读说明：本技术 一种电缆导体截面积测量方法 (Cable conductor sectional area measuring method ) 是由 刘毅 沈尹扩 林福昌 李化 于 2019-09-04 设计创作，主要内容包括：本发明公开了一种电缆导体截面积测量方法,包括：采用相同放大比,分别拍摄电缆和标准棒的横截面彩色图像；采用超像素分割法,对每张图像聚类分割,得到多个超像素；基于每张图像的多个超像素,采用区域合并法,确定该张图像中的导体轮廓；清点每个导体轮廓中像素点的个数,并基于标准棒对应的横截面中导体区域面积,计算电缆的导体截面积,完成测量。本发明首先采集相同大小的电缆和标准棒横截面彩色图像,然后根据电缆导体和导体间缝隙以及包覆层材料颜色存在差异,引入一套利用颜色差异信息来区分电缆导体与非导体的数字图像处理方式,整个处理过程操作便捷、精确度高且不会对被检测对象造成损伤,具有较高的经济效益,实用性较强。(The invention discloses a method for measuring the sectional area of a cable conductor, which comprises the following steps: respectively shooting cross-section color images of the cable and the standard rod by adopting the same magnification ratio; clustering and segmenting each image by adopting a super-pixel segmentation method to obtain a plurality of super-pixels; determining conductor outlines in each image by adopting a region merging method based on a plurality of super pixels of each image; counting the number of pixel points in each conductor contour, calculating the conductor sectional area of the cable based on the conductor area in the cross section corresponding to the standard rod, and finishing the measurement. According to the invention, the color images of the cross sections of the cable and the standard rod with the same size are firstly collected, then a set of digital image processing mode for distinguishing the cable conductor and the nonconductor by using color difference information is introduced according to the difference of the gaps between the cable conductor and the color of the coating layer material, the whole processing process is convenient and fast to operate, has high accuracy, cannot damage the detected object, and has higher economic benefit and stronger practicability.)

1. A method for measuring the sectional area of a cable conductor is characterized by comprising the following steps:

step 1, respectively shooting cross-section color images of a cable and a standard rod by adopting the same magnification ratio;

step 2, clustering and segmenting each image by adopting a super-pixel segmentation method to obtain a plurality of super-pixels;

step 3, determining conductor outlines in each image by adopting a region merging method based on the multiple super pixels of each image;

and 4, counting the number of pixel points in each conductor contour, and calculating the conductor sectional area of the cable based on the conductor area in the cross section corresponding to the standard rod to finish measurement.

2. A method of measuring a cross-sectional area of a conductor of an electrical cable according to claim 1, the method further comprising:

step 0, cutting the cable perpendicular to the central axis of the cable, and exposing the cross section of the cable; and cutting the standard rod perpendicular to the central axis of the standard rod, and exposing the cross section of the standard rod.

3. A method as claimed in claim 2, wherein the lengths of the cuts are less than 3 cm.

4. The method for measuring the sectional area of the cable conductor according to claim 1, wherein the same amplification ratio is specifically adopted: the same camera is used at a fixed object distance.

5. A cable conductor cross-sectional area measuring method according to claim 1, wherein the step 2 comprises:

s2.1, initializing an initial superpixel and a clustering center of each initial superpixel for each image;

s2.2, determining a calculation area of each clustering center, which is larger than the size of the corresponding initial superpixel, and calculating and updating the superpixels based on the distance from each pixel in each calculation area to the clustering center;

and S2.3, calculating the mass center of each updated super pixel, taking the mass center as a new clustering center of the super pixel, and repeatedly starting to execute the S2.2 until the iteration times are reached to obtain a plurality of super pixels.

6. A method as claimed in claim 5, wherein each of the initial super pixels is a square with equal size, and in S2.2, each of the calculation regions is a square with a side length 2 times as long as that of each of the initial super pixels.

7. The cable conductor cross-sectional area measuring method according to claim 5, wherein each pixel in each image is represented by a five-dimensional vector consisting of R, G, B channel information and pixel coordinates;

the distance is the distance between the five-dimensional vectors and the centroid of each superpixel is calculated based on the five-dimensional vectors of all pixels in that superpixel.

8. A cable conductor cross-sectional area measuring method according to claim 1, wherein the step 3 comprises:

extracting a gray value matrix of a preset color of each super pixel, and calculating a gray value average value under the gray value matrix of the super pixel, wherein preferably, the preset color is the color of a conductor;

traversing the gray value of the preset color of each pixel in each image, if the gray value is greater than the gray threshold of the image, updating the gray value of the pixel corresponding to the gray value to be a non-zero value, otherwise, updating the gray value to be zero, wherein the gray threshold of each image is a preset multiple of the maximum average value, and preferably, the preset multiple is one fourth;

and determining the conductor outline in the image based on the updated gray value distribution corresponding to the preset color in the image.

9. The method as claimed in claim 1, wherein in S4, the calculating the conductor cross-sectional area of the cable based on the conductor area in the cross-section corresponding to the standard bar includes:

calculating the occupied area of each pixel point based on the conductor area in the cross section corresponding to the standard rod and the number of the pixel points in the conductor outline, and obtaining the conductor sectional area in the cable based on the occupied area of each pixel point and the number of the pixel points in the conductor outline corresponding to the cable.

10. A method as claimed in any one of claims 1 to 9, wherein the number of pixels per image is greater than 800 ten thousand; the ratio of the conductor profile diameter corresponding to the cable to the image shortest side length of the cable is 1/2-2/3.

Technical Field

The invention belongs to the field of cable detection, and particularly relates to a method for measuring the sectional area of a cable conductor.

Background

The development of the cable industry is closely related to the major engineering construction of China, the application of the cable is wide, and the application of the cable has the following advantages: 1. the power transmission line of the power cable needs small space, the requirement on the laying path is low, and the power cable cannot occupy valuable urban space. 2. The cable laying is underground engineering, and the cable line can be finally covered by roads and buildings, so that the urban landscape cannot be interfered. 3. The same underground passage can accommodate multiple cable lines, and the load capacity of the power line can be greatly improved.

However, the cable industry is still faced with a number of problems, mainly with more rejected cables and difficulty in troubleshooting. Therefore, the cable pre-inspection has great significance for engineering construction.

An important index of the cable detection link is the cross-sectional area of the conductor, which is related to the direct current resistance and the current-carrying capacity of the cable. The traditional means mainly comprise three types: diameter measuring method, weighing method and method for measuring direct current resistance. The diameter measurement method calculates the sectional area of the conductor by measuring the diameter of a single copper wire, and the method has large error and is not suitable for cables made of compacted stranded conductors; the weighing method needs to intercept the power cable with the length of several meters, is accurate in measurement, is a method adopted by the national standard GB-T3048.2-2007, and is less in use in consideration of high cost of the power cable and serious influence on the sale and use of the power cable after cutting; the direct current resistance measurement method adopts direct current resistance to reversely push the cross section area of a conductor, the method is small in damage to a cable, but the direct current resistance of the conductor is also related to the length of the cable, some manufacturers make a false on the cross section area of the conductor and the length of the conductor at the same time, and the method can miss detection under the condition.

Disclosure of Invention

The invention provides a method for measuring the sectional area of a cable conductor, which is used for solving the technical problem that the method is low in practicability due to low precision and/or high cost in the conventional method for measuring the sectional area of the cable conductor.

The technical scheme for solving the technical problems is as follows: a method for measuring the sectional area of a cable conductor comprises the following steps:

step 1, respectively shooting cross-section color images of a cable and a standard rod by adopting the same magnification ratio;

step 2, clustering and segmenting each image by adopting a super-pixel segmentation method to obtain a plurality of super-pixels;

step 3, determining conductor outlines in each image by adopting a region merging method based on the multiple super pixels of each image;

and 4, counting the number of pixel points in each conductor contour, and calculating the conductor sectional area of the cable based on the conductor area in the cross section corresponding to the standard rod to finish measurement.

The invention has the beneficial effects that: the method comprises the steps of firstly, shooting high-definition color images of the cable and the standard rod by adopting the same magnification ratio in a direction perpendicular to the sections of the cable and the standard rod so as to ensure that the sizes of the two images are equal. Then, according to the difference of the colors of the gaps between the cable conductors and the color of the coating material, a digital image processing mode is introduced, wherein the cable conductors and the nonconductors are distinguished by using color difference information, specifically, each color image is subjected to super-pixel segmentation, and then, a region merging method is introduced to determine the boundary of the conductors and the nonconductors, so that the conductor contour determined by the boundary is clear, coherent and gapless, and the existence of noise points is greatly reduced. And finally, the conductor area of the cable can be determined by counting and calculating because the two images have the same size. The whole treatment process is convenient to operate, high in accuracy, free of damage to the detected object, high in economic benefit and high in practicability.

On the basis of the technical scheme, the invention can be further improved as follows.

Further, the method further comprises:

step 0, cutting the cable perpendicular to the central axis of the cable, and exposing the cross section of the cable; and cutting the standard rod perpendicular to the central axis of the standard rod, and exposing the cross section of the standard rod.

The invention has the further beneficial effects that: perpendicular to the central axis of the cable and the standard rod to provide more accurate cross section and further improve the accuracy of measuring the cross section area of the cable conductor.

Further, the lengths of the truncations are all less than 3 cm.

The invention has the further beneficial effects that: the method disclosed by the invention can be used for cutting off a small section perpendicular to the central axis of the cable to be detected to expose the cross section, and does not need to cut off a longer section, so that the problem that the sale and use of the power cable are seriously influenced after cutting is avoided, and therefore, the method is low in cost and high in practicability.

Further, the step of using the same amplification ratio specifically includes:

the same camera is used at a fixed object distance.

The invention has the further beneficial effects that: the same camera is adopted, and the sizes of two color images obtained by shooting can be accurately ensured to be equal under the fixed object distance, so that the two color images are mutually referred, and the area measurement accuracy is improved.

Further, the step 2 comprises:

s2.1, initializing an initial superpixel and a clustering center of each initial superpixel for each image;

s2.2, determining a calculation area of each clustering center, which is larger than the size of the corresponding initial superpixel, and calculating and updating the superpixels based on the distance from each pixel in each calculation area to the clustering center;

and S2.3, calculating the mass center of each updated super pixel, taking the mass center as a new clustering center of the super pixel, and repeatedly starting to execute the S2.2 until the iteration times are reached to obtain a plurality of super pixels.

The invention has the further beneficial effects that: according to the super-pixel segmentation method, the image is initially segmented through the distance measurement among the pixel points to obtain a plurality of super-pixels, the mass center of each super-pixel is calculated based on the super-pixels obtained through each iteration, next iteration is carried out based on the mass center, the difference of color information can be effectively utilized, the iteration times are reduced, the optimal super-pixel segmentation effect is obtained, and the segmentation reliability is improved.

Further, each initial super pixel is a square with the same size, and in S2.2, each calculation region is a square, and the side length of each calculation region is 2 times the side length of each super pixel.

Further, each pixel in each image is represented by a five-dimensional vector composed of R, G, B channel information and pixel coordinates;

the distance is the distance between the five-dimensional vectors and the centroid of each superpixel is calculated based on the five-dimensional vectors of all pixels in that superpixel.

The invention has the further beneficial effects that: the method combines RGB color channels and pixel coordinates of the color image to form a five-dimensional vector, performs distance measurement calculation through the five-dimensional vector of each pixel, fully considers the color difference between a conductor and a nonconductor and the difference of a space direction, and can greatly improve the extraction accuracy of the conductor outline.

Further, the step 3 comprises:

extracting a gray value matrix of a preset color of each super pixel, and calculating a gray value average value under the gray value matrix of the super pixel, wherein the preset color is the color of a conductor;

traversing the gray value of the preset color of each pixel in each image, if the gray value is greater than the gray threshold of the image, updating the gray value of the pixel corresponding to the gray value to be a non-zero value, otherwise, updating the gray value to be zero, wherein the gray threshold of each image is a preset multiple of the maximum mean value;

and determining the conductor outline in the image based on the gray value distribution corresponding to the preset color in the image.

The invention has the further beneficial effects that: the color of the conductor to be separated is set to be a preset color, the gray value matrix of the conductor color is extracted, the outline of the conductor can be conveniently marked off, and the method is convenient, rapid and accurate.

Further, in S4, the calculating a conductor sectional area of the cable based on the conductor region area in the cross section corresponding to the standard bar specifically includes:

calculating the occupied area of each pixel point based on the conductor region area in the cross section corresponding to the standard rod and the number of the pixel points in the conductor outline, and obtaining the conductor sectional area in the cable based on the occupied area of each pixel point and the number of the pixel points in the conductor outline corresponding to the cable.

The invention has the further beneficial effects that: the amplification ratios of the two color images are the same, the actual areas corresponding to the single pixels in the two images are the same, therefore, the area occupied by each pixel point of the conductor can be calculated through the conductor cross section area of the standard rod and the number of the pixel points of the conductor cross section obtained through counting, on the basis, the number of the pixel points of the cable conductor obtained through counting can be used for obtaining the area of the cable conductor cross section, and the method is high in accuracy, low in cost, easy to operate and high in practicability.

Further, the number of pixels of each image is more than 800 ten thousand; the ratio of the conductor profile diameter corresponding to the cable to the image shortest side length of the cable is 1/2-2/3.

Drawings

Fig. 1 is a flow chart of a method for measuring a cross-sectional area of a cable conductor according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of a ratiometric imaging apparatus provided by an embodiment of the present invention;

FIG. 3 is a schematic diagram of an initialization image of a cluster center of a cross section of a cable conductor according to an embodiment of the present invention;

FIG. 4 is a schematic image of a cable conductor cross-section after super-pixel segmentation according to an embodiment of the present invention;

fig. 5 is a schematic image of a cross section of a cable conductor after area threshold merging according to an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.