An algorithm for quickly and accurately calculating the roundness of sand and gravel

Abstract

The present invention relates to an algorithm for quickly and accurately calculating the roundness of sand and gravel. The contour line and two-dimensional coordinates of an image of a single sand and gravel particle are obtained; the area G of the sand and gravel particle is calculated; an arbitrary point inside the contour line is selected as the initial center coordinate, and the maximum distance from the initial center coordinate to the points on the contour line is used as the initial radius R0 to form a circumscribed circle, and several intersection points are formed between the circumscribed circle and the contour line; the vectors from the initial center to the intersection points of the circumscribed circle and the contour line are superimposed, and after unitization, a displacement vector is formed. The initial center moves along the direction of the displacement vector to obtain a new center, and a new circumscribed circle is formed according to the foregoing, and the iteration is repeated until the convergence speed of the radius R'0 of the circumscribed circle reaches a set value, and the roundness of the sand and gravel is calculated. Through the present invention, the radius of the minimum circumscribed circle of the sand and gravel particle can be accurately and quickly locked, and then a more accurate roundness of the sand and gravel particle can be obtained.

Description

Technical Field

[0001] The present invention relates to the field of building materials, and particularly to an algorithm for quickly and accurately calculating the roundness of sand and gravel. Background Art

[0002] The particle shape of sand and gravel has a certain impact on the workability of concrete. Especially in view of the current shortage of natural sand and gravel resources and the large-scale application of manufactured sand and recycled aggregates, the particle shapes of manufactured sand and recycled aggregates are more complex than those of natural sand and gravel. The evaluation of the particle shape of sand and gravel can be used as a basis for the selection of raw materials for high-performance concrete. The sphericity similarity is one of the indicators used to measure the particle shape of sand and gravel, and the roundness is the only parameter used to calculate the sphericity similarity. The "Technical Specification for High-Performance Concrete with Manufactured Sand in Highway" (T / CECS G:K50-30—2018) defines the roundness of manufactured sand as the ratio of the projected area of the same manufactured sand particle to the area of the minimum circumscribed circle. However, in the calculation process, the maximum particle size length is used to replace the diameter of the minimum circumscribed circle to calculate the roundness, which is an approximate calculation method adopted to simplify the calculation of roundness and has non-negligible calculation errors. Summary of the Invention

[0003] In order to solve the problems existing in the prior art, the present invention provides an algorithm for quickly and accurately calculating the roundness of sand and gravel, thereby realizing an accurate evaluation of the particle shape of sand and gravel, which can be used to guide the production of sand and gravel and the production and configuration of concrete.

[0004] The technical object of the present invention is achieved by the following technical solutions:

[0005] An algorithm for quickly and accurately calculating the roundness of sand and gravel, the method comprising the following steps:

[0006] Step 1, obtaining an image of a single sand and gravel particle;

[0007] Step 2, calculating the area G of the sand and gravel particle according to the number of image pixels, extracting the contour line of the sand and gravel particle image, and obtaining the two-dimensional coordinates of the contour line;

[0008] Step 3, selecting any point inside the contour line as the initial center coordinate, taking the maximum distance from the initial center coordinate to the points on the contour line as the initial radius R0, forming a circumscribed circle with the initial radius R0 with the initial center, and the circumscribed circle and the contour line form a number of intersection points;

[0009] Step 4, superimposing the vectors from the initial center to the intersection points of the circumscribed circle and the contour line, normalizing to form a displacement vector, moving the initial center along the direction of the displacement vector to obtain a new center, taking the maximum distance from the new center to the points on the contour line as the new radius R'0, forming a circumscribed circle with the new center with the initial radius R'0, and the circumscribed circle formed with the new center and the contour line form a number of intersection points;

[0010] Step 5: Repeat Step 4 for iteration until the convergence rate of the radius R’0 of the circumscribed circle reaches the set value, and calculate the circularity of the sand and gravel when the convergence rate of the radius R’0 of the circumscribed circle reaches the set value.

[0011] Furthermore, the abscissa and ordinate of the initial center coordinates selected in Step 3 are respectively the average value of the abscissa extreme values and the average value of the ordinate extreme values in the coordinates of the sand and gravel contour line. Calculating through the average value of the coordinate extreme values can make the position of the initial center closer to the center position of the minimum circumscribed circle than selecting any point inside the contour line as the initial center, and can significantly reduce the number of iterations.

[0012] Furthermore, before extracting the two-dimensional coordinates of the contour line of the sand and gravel particle image, the image of the sand and gravel particle is processed, and the processing includes binary processing of the sand and gravel image and noise reduction processing of the sand and gravel image after binary processing.

[0013] Furthermore, in Step 1, it also includes cleaning and drying a single sand and gravel particle, and then taking an image of the single sand and gravel particle.

[0014] Furthermore, when taking a photo of the sand and gravel particle, place the sand and gravel particle on a white diffuser plate for shooting.

[0015] Furthermore, the displacement vector where X0 is the abscissa of the initial center, Y0 is the ordinate of the initial center, X’ i is the abscissa of the i-th intersection point of the circumscribed circle formed by the initial center and the contour line, Y’ i is the ordinate of the i-th intersection point of the circumscribed circle formed by the initial center and the contour line, and k is the number of intersection points of the circumscribed circle formed by the initial center and the contour line.

[0016] Furthermore, the distance from the initial center to the contour line in the opposite direction of the displacement vector is L, and the initial center moves a distance of d along the direction of the displacement vector. where the initial value of n is 1. During the iteration process, if R’0 increases compared to the previous R’0, the value of n is incremented by 1, and the result of the previous iteration is maintained.

[0017] Furthermore, use MATLAB programming to process the image of the sand and gravel particle. Call the MATLAB function im2bw to perform binary processing on the sand and gravel particle image, call the MATLAB function regionprops to perform noise reduction on the binary processed image, and call the MATLAB function edge to extract the contour of the sand and gravel particle and obtain the two-dimensional coordinates of the contour line.

[0018] Furthermore, when calculating the circularity Y of the sand and gravel,

[0019] Compared with the prior art, the beneficial effects of the invention are as follows. Through the algorithm for quickly and accurately calculating the roundness of sand and gravel in the present invention, it has high precision and fast convergence speed. It can relatively accurately and quickly lock and obtain the radius of the minimum circumscribed circle of sand and gravel particles. By calculating the roundness of sand and gravel particles through this radius, a relatively accurate roundness of sand and gravel particles can be calculated. On the basis of calculating the roundness of sand and gravel particles, calculating the sphericity similarity of sand and gravel particles is more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the change in the sand and gravel image processing process in the present invention.

[0021] Figure 2 It is a schematic diagram of the process of the circumscribed circle radius R0 of sand and gravel converging with the number of iterations in the program coordinate system of the present invention.

[0022] Figure 3 It is a schematic diagram of the calculation results of the minimum circumscribed circle radius R and the center of the minimum circumscribed circle of sand and gravel in the program coordinate system of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] The technical solution of the present invention will be further described below in conjunction with the specific embodiments:

[0024] An algorithm for quickly and accurately calculating the roundness of sand and gravel, which changes the existing method of calculating roundness using the maximum particle size length as the diameter, relatively accurately locks the circumscribed circle closest to the roundness of sand and gravel, so as to obtain the best roundness calculation result. This method can be used for calculating the roundness of natural sand and gravel, manufactured sand, and recycled aggregates. The method of the present invention includes the following steps:

[0025] Step 1: Obtain an image of a single sand and gravel particle; in order to reduce the influence of sand and gravel particles on the calculation result, before obtaining the image, the sand and gravel particles can also be washed and dried first. Place the washed and dried sand and gravel particles on a white diffuser plate, and use a camera to take pictures of the sand and gravel particles to obtain an image of the sand and gravel particles.

[0026] Step 2: Process the taken image through MATLAB programming. Call the MATLAB function im2bw to perform binary processing on the sand and gravel particle image, and call the MATLAB function edge to extract the contour of the sand and gravel particles and obtain the two-dimensional coordinates of the contour line; there will be noise in the image after binary processing, and the noise will form interference. Therefore, before calling the MATLAB function edge to extract the contour of the sand and gravel particles and obtain the two-dimensional coordinates of the contour line, the noise needs to be processed. In this embodiment, the MATLAB function regionprops is called to perform noise reduction on the binary processed image; calculate the area G of the sand and gravel particles according to the number of pixels in the image after noise reduction processing; the image changes during the image processing process are asFigure 1 as shown

[0027] Step 3: Select any point inside the contour line as the initial center coordinate, and take the maximum distance from the initial center coordinate to the points on the contour line as the initial radius R0. The coordinate of the initial center is expressed as (X0, Y0); form a circumscribed circle with the initial center and the initial radius R0. The circumscribed circle and the contour line form k intersection points, and their coordinates are expressed as (X’ i , Y’ i );

[0028] Preferably, in order to improve the calculation speed, the abscissa and ordinate of the initial center coordinate are respectively the average value of the abscissa extreme values and the average value of the ordinate extreme values in the sand and gravel contour line coordinates. For example, the maximum value of the abscissa on the contour is X max , the minimum value of the abscissa is X min , the maximum value of the ordinate is Y max , the minimum value of the ordinate is Y min , where

[0029] Step 4: Superimpose the vectors from the initial center to the intersection points of the circumscribed circle and the contour line, and form a displacement vector after unitization. The displacement vector where X0 is the abscissa of the initial center, Y0 is the ordinate of the initial center, X’ i is the abscissa of the i-th intersection point of the circumscribed circle formed by the initial center and the contour line, Y’ i is the ordinate of the i-th intersection point of the circumscribed circle formed by the initial center and the contour line, and k is the number of intersection points of the circumscribed circle formed by the initial center and the contour line;

[0030] The initial center moves along the direction of the displacement vector to obtain a new center. The maximum distance from the new center to the points on the contour line is used as the new radius R’0. A circumscribed circle with the new center and the initial radius R’0 is formed, and several intersection points K’ are formed by the circumscribed circle formed by the new center and the contour line;

[0031] The distance of each movement is d, and the distance from the initial center to the contour line in the opposite direction of the displacement vector is L, where the initial value of n is 1, and the value of n changes with the change of R’0. If R’0 increases compared with the previous R’0, the value of n is incremented by 1, that is, n = n + 1, and then the result of the previous iteration is selected for iterative calculation; if R’0 decreases or remains unchanged compared with the previous R’0, n remains unchanged, and the current result is used for iterative calculation.

[0032] Step 5: Repeat Step 4 for iteration until the convergence speed of the radius R’0 of the circumscribed circle reaches the set value, such as Figure 2As shown, when the convergence rate reaches a certain value, the change in the radius of the circumscribed circle tends to be stable. For example, when the change amplitude of R’0 in the first 10 iterations before the current iteration compared to R’0 in the 100th current iteration is less than 0.001%, R’0 at this time can be considered as the closest radius R of the circumscribed circle, such as Figure 3 As shown, calculate the circularity according to this value

[0033] This embodiment is only a further explanation of the present invention and not a limitation thereof. Those skilled in the art can make non-creative modifications to this embodiment as needed after reading this specification, but as long as it is within the scope of the claims of the present invention, it is protected by the patent law.

Claims

1. An algorithm for quickly and accurately calculating the roundness of sand and gravel, characterized in that, The algorithm includes the following steps: Step 1: Obtain an image of a single sand and gravel particle; Step 2: Calculate the area G of the sand and gravel particle according to the number of pixel points in the sand and gravel particle image; Extract the contour line of the sand and gravel particle image and obtain the two-dimensional coordinates of the contour line; Step 3: Select any point inside the contour line as the initial center coordinate, take the maximum distance from the initial center coordinate to the points on the contour line as the initial radius R0, form a circumscribed circle with the initial radius R0 with the initial center, and the circumscribed circle and the contour line form several intersection points; Step 4: Superimpose the vectors from the initial center to the intersection points of the circumcircle and the contour line, unitize them to form a displacement vector, and move the initial center along the direction of the displacement vector to obtain a new center. The maximum distance from the new center to the points on the contour line is used as the new radius R , 0, and form a circumcircle with the new center and an initial radius of R , 0. The circumcircle formed with the new center and the contour line form several intersection points, and the displacement vector where X0 is the abscissa of the initial center, Y0 is the ordinate of the initial center, X i , is the abscissa of the i-th intersection point of the circumcircle formed by the initial center and the contour line, and Y i , is the ordinate of the i-th intersection point of the circumcircle formed by the initial center and the contour line, k is the number of intersection points of the circumcircle formed by the initial center and the contour line, the distance from the initial center to the contour line in the opposite direction of the displacement vector is L, and the distance that the initial center moves along the direction of the displacement vector is d where the initial value of n is 1. During the iteration process, if R , 0 is larger than the previous R , 0, the value of n is incremented by 1, and the previous iteration result is maintained Step 5. Repeat Step 4 for iteration until the radius R of the circumscribed circle , 0 converges to the set value, and the radius R of the circumscribed circle , 0 When the convergence speed reaches the set value, calculate the circularity of the sand and gravel based on the radius R.

2. The algorithm for quickly and accurately calculating the roundness of sand and gravel according to claim 1, characterized in that, In Step 3, the abscissa and ordinate of the selected initial center coordinate are respectively the average value of the abscissa extreme values and the average value of the ordinate extreme values in the sand and gravel contour line coordinates.

3. A method for quickly and accurately calculating the roundness of sand and gravel according to claim 1 or 2, characterized in that Before extracting the two-dimensional coordinates of the contour line of the sand and gravel particle image, the image of the sand and gravel particle is processed, and the processing includes binary processing of the sand and gravel image and noise reduction processing of the sand and gravel image after binary processing.

4. An algorithm for quickly and accurately calculating the roundness of sand and gravel according to claim 3, characterized in that, In Step 1, it also includes cleaning and drying a single sand and gravel particle, and then taking an image of the single sand and gravel particle.

5. The algorithm for quickly and accurately calculating the roundness of sand and gravel according to claim 4, characterized in that, When taking a photo of the sand and gravel particle, place the sand and gravel particle on a white diffuser plate for shooting.

6. A method for quickly and accurately calculating the roundness of sand and gravel according to claim 3, characterized in that Process the image of the sand and gravel particle through MATLAB programming, call the MATLAB function im2bw to perform binary processing on the sand and gravel particle image, call the MATLAB function regionprops to perform noise reduction on the binary processed image, and call the MATLAB function edge to extract the sand and gravel particle contour and obtain the two-dimensional coordinates of the contour line.

7. An algorithm for quickly and accurately calculating the roundness of sand and gravel according to claim 1, characterized in that When calculating the roundness Y of sand and gravel,

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