An instrument and method for detecting needle-like and flaky particles in sand and gravel aggregates.

Abstract

This invention provides a detector and method for detecting needle-like and flaky aggregates in sand and gravel, belonging to the field of concrete materials engineering technology. It solves the problem of detection errors in traditional methods for flaky aggregates. In the detector, a light box is placed at the bottom of the machine housing, containing an LED light source. A flat or corrugated transparent tray is horizontally placed on the upper surface of the light box, both types of trays being used to support the sand and gravel aggregates to be tested. A camera is located on the top of the machine housing, shooting vertically downwards, and is communicatively connected to a computer. The camera captures images of the sand and gravel aggregates to be tested on the two trays and transmits them to the computer. The computer, based on the received images, calculates and compares the roundness of the two images to obtain the aggregate thickness coefficient, thus realizing the detection of needle-like and flaky content in the sand and gravel aggregates. This invention has the advantages of being unaffected by the aggregate's own color and having high detection accuracy.

Description

Technical Field

[0001] This invention belongs to the field of concrete material engineering technology and is applied to the detection process of sand and gravel aggregates during concrete production. Specifically, it is a sand and gravel aggregate needle-like and flaky detector and detection method. Background Technology

[0002] During concrete production and construction, the content of flaky and needle-like particles in the sand and gravel aggregates significantly affects the strength and workability of the concrete. Excessive flaky and needle-like particle content increases the risk of pump blockage during construction. Therefore, accurate detection of the flaky and needle-like particle content in sand and gravel aggregates is crucial. Currently, the mainstream method for this type of detection involves screening using mechanical devices combined with manual labor. This method is inefficient, and manual identification is prone to errors and missed detections.

[0003] Using computer vision technology for this type of inspection offers significant advantages, including high efficiency, low energy consumption, minimal pollution, and quick and easy operation. However, existing computer vision inspection methods have a significant drawback: during inspection, the aggregates are laid flat under gravity. While this method is relatively accurate for detecting needle-shaped aggregates, it often misidentifies coin-shaped or flaky aggregates as spheres, leading to a substantial system detection error. This error affects the material adjustment process during concrete production, resulting in concrete that fails to meet construction quality requirements. Summary of the Invention

[0004] The purpose of this invention is to solve the problems mentioned in the background art and to provide a detection method that can measure the thickness of flaky particles in sand and gravel aggregates, quickly perform the detection process of needle-like and flaky particles, and distinguish between flaky and spherical particles; this invention has the advantages of being unaffected by the color of the aggregate itself and having high detection accuracy.

[0005] The present invention employs the following technical solutions to achieve its objective:

[0006] A needle-like and flaky particle detector for sand and gravel aggregates includes a chassis, a camera, a light box, a computer, a flat transparent tray, and a corrugated transparent tray. The light box is placed at the bottom of the chassis and contains an LED light source. The flat transparent tray or the corrugated transparent tray is placed horizontally on the upper surface of the light box, and both trays are used to hold the sand and gravel aggregates to be tested. The camera is located on the top of the chassis, with its shooting direction vertically downward. The camera is communicatively connected to the computer. The camera is used to capture images of the sand and gravel aggregates to be tested on the two trays and transmit them to the computer. The computer is used to detect the needle-like and flaky particle content of the sand and gravel aggregates based on the received images.

[0007] Further, the included angle between every two corrugated sheets in the corrugated transparent tray is 60 degrees; the computer is configured to analyze three-dimensional features by comparing the circularity based on images of the same sand and gravel aggregate sample in a flat state and a 60-degree inclined state, calculate the flaky content and the overall flaky feature value, and realize the detection process of the needle-like and flaky content of sand and gravel aggregates.

[0008] Preferably, a light source switch is provided on the light box, and the light source switch is exposed on the side surface of the chassis for switching control of the LED light source.

[0009] The present invention also provides a method for detecting needle-like and flaky sand and gravel aggregates, including the following steps:

[0010] S1. Turn on the light source switch to light up the LED light source in the light box;

[0011] S2. Place the sand and gravel aggregates to be detected on the flat transparent tray, shake and disperse them, and then place them together with the tray on the upper surface of the light box in the chassis; then close the chassis to prevent external light from entering; control the camera on the top of the chassis through the computer to obtain the first projection image of the sand and gravel aggregates to be detected.

[0012] S3. Take out the flat transparent tray from the chassis, pour the sand and gravel aggregates to be detected on the corrugated transparent tray, shake and disperse them, and then place them together with the tray on the upper surface of the light box in the chassis; then close the chassis to prevent external light from entering; control the camera on the top of the chassis through the computer to obtain the second projection image of the sand and gravel aggregates to be detected.

[0013] S4. According to the first projection image and the second projection image automatically imported into the computer, calculate the circularity r of the aggregates in the two images in the computer through a program, obtain the sphericity index p based on the circularity, and through mathematical relationship transformation, obtain the thickness coefficient t of the aggregates. The value of t ranges from 0 to 1, where 0 represents that the aggregate is flaky and 1 represents that the aggregate is spherical, thereby realizing the detection of needle-like and flaky sand and gravel aggregates.

[0014] Among them, the aggregate is simplified as an ellipsoid for analysis. The projection of the ellipsoid is an ellipse. Let the relative length of the long semi-axis of the ellipse be 1 and the relative length of the short semi-axis be t, then 0 < t ≤ 1; t is also the final target calculation result, that is, the thickness coefficient of the aggregate.

[0015] In the flat state, the projection area of the ellipsoid is S1 and the relative projection total length is 2; in the 60-degree inclined state, the projection area of the ellipsoid is S2, and the relative projection total length is set as l.

[0016] After derivation, the mathematical relationship between l and t is:

[0017]

[0018] Based on this mathematical relationship, the thickness coefficient t of the aggregate is obtained.

[0019] Furthermore, the mathematical relationship between the aggregate thickness coefficient t and the sphericity index p can be derived as follows:

[0020]

[0021] Based on this mathematical relationship, after the camera captures the first and second projected images, the computer performs calculations through a program to detect the needle-like and flaky texture of the sand and gravel aggregate.

[0022] In summary, due to the adoption of this technical solution, the beneficial effects of this invention are as follows:

[0023] The detector of this invention obtains images unaffected by the color of the aggregate itself, thus solving the problem of color difference in aggregates. The detection method, combined with a corrugated transparent tray, addresses the difficulties and low accuracy in detecting spherical aggregates. Furthermore, this invention also has the following advantages:

[0024] High efficiency: It can quickly process large amounts of image data, greatly improving processing speed and efficiency;

[0025] Accuracy: Compared to manual processing, computer vision inspection technology can more accurately identify and extract information about target objects, reducing errors and missed detections;

[0026] Automation: The computer vision detection and calculation process can automatically process and analyze image and video data. This part does not require human intervention. Obtaining the image is equivalent to obtaining the detection result, thereby greatly reducing labor costs.

[0027] Reliability: Computer vision inspection can perform continuous monitoring and data acquisition over long periods of time, thereby improving the reliability and stability of the data.

[0028] The testing instrument and accompanying testing method of this invention have good scalability to meet the testing needs of similar application scenarios; at the same time, the testing process is green and environmentally friendly, without wasting production materials and producing no dust or noise pollution. Therefore, the testing instrument and testing method of this invention can be widely used in the self-inspection of sand and gravel aggregate production and the design and adjustment process during concrete mixing, improving the strength and workability of concrete and reducing the risk of concrete pump blockage. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the basic structure of the detector of the present invention;

[0030] Figure 2A schematic diagram of a planar transparent support plate supporting sand and gravel aggregate;

[0031] Figure 3 A schematic diagram of a corrugated transparent support plate supporting sand and gravel aggregate;

[0032] Figure 4 A schematic diagram illustrating the mathematical derivation principle of aggregate under a 60-degree inclination.

[0033] Figure 5 A schematic diagram illustrating the mathematical derivation principle of aggregates in a flat-lay state;

[0034] Figure 6 This is an auxiliary diagram illustrating the relevant parameters in the mathematical derivation process of aggregates in a flat-lay state.

[0035] The meanings of the markings in the attached diagram are as follows:

[0036] 1-Chassis, 2-Camera, 3-Lightbox, 4-Light source switch, 5-LED light source, 6-Computer, 7-Sand and gravel aggregate, 8-Flat transparent tray, 9-Corrugated transparent tray. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0038] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0039] Example 1

[0040] like Figures 1 to 3As shown, a needle-like and flaky aggregate detector for sand and gravel includes a chassis 1, a camera 2, a light box 3, a computer 6, a flat transparent tray 8, and a corrugated transparent tray 9. The light box 3 is placed at the bottom of the chassis 1 and has an LED light source 5. The flat transparent tray 8 or the corrugated transparent tray 9 is placed horizontally on the upper surface of the light box 3, and both trays are used to support the sand and gravel aggregate 7 to be tested. The camera 2 is set on the top of the chassis 1, and the shooting direction of the camera 2 is vertically downward. The camera 2 is communicatively connected to the computer 6. The camera 2 is used to capture images of the sand and gravel aggregate 7 to be tested in the two trays and transmit them to the computer 6. The computer 6 is used to detect the needle-like and flaky content of the sand and gravel aggregate 7 based on the received images.

[0041] In this embodiment, the light box 3 serves as the background for image capture. Clear projected images of the sand and gravel aggregate 7 under two different conditions can be obtained through the chassis 1 and camera 2. These images are unaffected by the aggregate's own color, thus solving the color difference problem. The images can be automatically transmitted to the computer 6 for analysis. The detection method employs image processing technology, which can accurately measure the sphericity of the aggregate. Additionally, it can measure multiple indicators such as particle size distribution and particle count.

[0042] like Figure 3 As shown, the included angle between each pair of corrugated pieces in the corrugated transparent tray 9 is 60 degrees; the computer 6 is used to analyze the three-dimensional features by comparing the circularity of the same sand and gravel aggregate 7 sample in a flat state and a 60-degree tilt state, based on the images of the same sample in a flat state and a 60-degree tilt state, to calculate the flaky content and the overall flaky feature value, thus realizing the detection process of flaky content of sand and gravel aggregate 7.

[0043] In this embodiment, a light source switch 4 is provided on the light box 3. The light source switch 4 is exposed on the side of the chassis 1 and is used to switch and control the LED light source 5, which facilitates the operation of the light during the detection process.

[0044] Example 2

[0045] This embodiment uses the detector from Embodiment 1 to detail a method for detecting needle-like and flaky particles in sand and gravel aggregates. The method specifically includes the following steps:

[0046] S1. Turn on the light source switch to illuminate the LED light source inside the light box;

[0047] S2. Place the sand and gravel aggregate to be tested on a flat transparent tray, shake it to disperse it, and then place it together with the tray on the upper surface of the light box inside the machine; then close the machine to prevent external light from entering; use a computer to control the camera on the top of the machine to take a picture and obtain the first projected image of the sand and gravel aggregate to be tested.

[0048] S3. Take out the flat transparent pallet from the chassis, pour the sand and gravel aggregates to be detected onto the corrugated transparent pallet, shake and disperse them, and then place them together with the pallet on the upper surface of the light box in the chassis. Then close the chassis to prevent external light from entering. Control the camera on the top of the chassis through the computer to take a second projection image of the sand and gravel aggregates to be detected.

[0049] S4. Based on the first projection image and the second projection image automatically communicated and imported into the computer, calculate the roundness r of the aggregates in the two images through a program in the computer. Obtain the sphericity index p based on the roundness. After transformation through mathematical relationships, obtain the thickness coefficient t of the aggregates. The value of t ranges from 0 to 1, where 0 represents flaky aggregates and 1 represents spherical aggregates, thereby realizing the detection of needle-like and flaky sand and gravel aggregates.

[0050] In step S4, the specific method for the computer program to calculate and realize the detection of needle-like and flaky sand and gravel aggregates includes:

[0051] Simplify the aggregate into an ellipsoid for analysis. The projection of the ellipsoid is an ellipse. Let the relative length of the long semi-axis of the ellipse be 1 and the relative length of the short semi-axis be t, then 0 < t ≤ 1. Refer to Figure 5 for the schematic; t is also the final target calculation result, that is, the thickness coefficient of the aggregate.

[0052] In the flat state, the projection area of the ellipsoid is S1, and the relative total projection length is 2; in the 60-degree inclined state, the projection area of the ellipsoid is S2, and the relative total projection length is set as l. Refer to Figure 4 for the schematic;

[0053] According to the sphericity index formula, it can be obtained that: the ratio of the relative total projection lengths in the two states is equal to the ratio of the projection areas, and also equal to the ratio of the roundness r in the two states, that is, the sphericity index. The formula is as follows:

[0054]

[0055] In the formula, r1 is the roundness of the sand and gravel aggregates in the first projection image; r2 is the roundness of the sand and gravel aggregates in the second projection image.

[0056] 8]At this time, the goal of deriving the problem in the method can be clearly defined as: determining the relationship between t and p.

[0057] In the 60-degree inclined state, the relative total projection length l of the ellipsoid is related to the total length of the short axis 2t of the elliptical projection of the ellipsoid at this time, that is, related to the thickness of the ellipsoid. By determining the mathematical relationship between t and p, and based on the obtained sphericity index p, obtain the thickness coefficient t of the aggregate to realize the detection of needle-like and flaky sand and gravel aggregates.

[0058] The original definition of circularity was: e = (4π * area) / (perimeter * perimeter). However, since different pixel sizes can lead to errors in perimeter measurement, in this embodiment, the circularity r is obtained using the following definition:

[0059]

[0060] For a circular sheet with a thickness of 0, p = 0.5; for a sphere, p = 1. For an ellipsoid, which lies between a sheet and a sphere, the value of p is between 0.5 and 1, and increases with increasing sphericity.

[0061] Based on the above definition, the roundness r1 of the sand and gravel aggregate in the first projected image and the roundness r2 of the sand and gravel aggregate in the second projected image are directly obtained through a computer program; then, according to the sphericity index formula, the sphericity index p of the sand and gravel aggregate to be tested is obtained; based on the sphericity index p, the relative total projection length l under a 60-degree tilt state is obtained, and the mathematical relationship between l and t can be derived as follows:

[0062]

[0063] The derivation of the mathematical relationship between l and t is as follows; relevant parameters can be found in [reference needed]. Figure 6 The illustration:

[0064] For the elliptic projection of an ellipsoid, the formula for the ellipse is:

[0065]

[0066] In the formula, point (x, y) is a point on the ellipse corresponding to the vertical projection boundary line under a 60-degree tilt; the slope formula on the ellipse is:

[0067]

[0068] The slope at the point of tangency of the ellipse is It can be concluded that:

[0069]

[0070]

[0071] In the formula, such as Figure 6 As shown, α is the angle between the line connecting point (x,y) to the origin and the x-axis; the total length L of the elliptical projection axis passing through point (x,y) and the origin is:

[0072]

[0073] Furthermore, we can deduce:

[0074]

[0075] This completes the derivation process.

[0076] Based on the mathematical relationship between l and t obtained through derivation, since the ratio of the total relative projection length l in the 60-degree tilt state to the total relative projection length 2 in the tiling state is equal to the ratio of the circularity of the two images, that is:

[0077]

[0078] The mathematical relationship between the aggregate thickness coefficient t and the sphericity index p is derived as follows:

[0079]

[0080] Based on this mathematical relationship, after the camera captures the first and second projected images, the computer performs calculations through a program to detect the needle-like and flaky texture of the sand and gravel aggregate.

Claims

1. A needle-like and flaky particle detector for sand and gravel aggregates, characterized in that: The system includes a chassis (1), a camera (2), a light box (3), a computer (6), a flat transparent tray (8), and a corrugated transparent tray (9); the light box (3) is placed at the bottom of the chassis (1) and has an LED light source (5); the flat transparent tray (8) or the corrugated transparent tray (9) is placed horizontally on the upper surface of the light box (3), and the two trays are used to carry the sand and gravel aggregate (7) to be tested; the camera (2) is set on the top of the chassis (1), and the shooting direction of the camera (2) is vertically downward, and the camera (2) is communicatively connected to the computer (6); the camera (2) is used to take pictures of the sand and gravel aggregate (7) to be tested in the two trays and transmit them to the computer (6), and the computer (6) is used to detect the needle-like and flaky content of the sand and gravel aggregate (7) based on the two images received; The included angle between each pair of corrugated pieces in the corrugated transparent tray (9) is 60 degrees; The computer (6) is also used to perform the following program calculation process: The image captured by the planar transparent tray (8) is recorded as the first projected image, and the image captured by the corrugated transparent tray (9) is recorded as the second projected image. The aggregate is simplified into an ellipsoid for analysis. The projection of the ellipsoid is an ellipse. Let the relative length of the major semi-axis of the ellipse be 1, and the relative length of the minor semi-axis be... ,but ; This also serves as the final calculation result for the target, namely the aggregate thickness coefficient; Define roundness The calculation method is as follows: The following formula for the sphericity index is determined: In the formula, The roundness of the sand and gravel aggregate in the first projected image; The roundness of the sand and gravel aggregate in the second projected image; The projected area of ​​the ellipsoid in its flat state is 2, and its total relative projected length is 2. This represents the projected area of ​​the ellipsoid at a 60-degree tilt. This represents the total relative projection length under this condition; Based on roundness and sphericity index This allows us to obtain the total relative projection length under a 60-degree tilt. Then and The mathematical relationship is determined as follows: Based on this mathematical relationship, the thickness coefficient of the aggregate is derived. ; The thickness coefficient of the aggregate Sphericity index The mathematical relationship is determined as follows: Based on this mathematical relationship, after the camera (2) captures the first and second projected images, the needle-like and flaky detection of the sand and gravel aggregate (7) is realized.

2. The sand and gravel aggregate needle-like and flaky particle detector according to claim 1, characterized in that: The light box (3) is equipped with a light source switch (4), which is exposed on the side of the chassis (1) and is used to switch and control the LED light source (5).

3. A method for detecting needle-like and flaky particles in sand and gravel aggregates, characterized in that, Includes the following steps: S1. Turn on the light source switch (4) to light up the LED light source (5) inside the light box (3); S2. Place the sand and gravel aggregate (7) to be tested on a flat transparent tray (8), shake it to disperse it, and then place it together with the tray on the upper surface of the light box (3) inside the machine box (1); then close the machine box (1) to prevent external light from entering; control the camera (2) on the top of the machine box (1) through the computer (6) to take a picture and obtain the first projection image of the sand and gravel aggregate (7) to be tested; S3. Take the flat transparent tray (8) out of the machine box (1), pour the sand and gravel aggregate (7) to be tested onto the corrugated transparent tray (9), shake it to disperse it, and place it together with the tray on the upper surface of the light box (3) inside the machine box (1); then close the machine box (1) to prevent external light from entering; control the camera (2) on the top of the machine box (1) through the computer (6), and the photographer obtains the second projection image of the sand and gravel aggregate (7) to be tested; S4. Based on the first and second projection images imported into the computer (6) via automatic communication, the roundness of the aggregate in the two images is calculated by a program in the computer (6). The sphericity index is derived from the roundness. After transformation through mathematical relationships, the thickness coefficient of the aggregate is obtained. , The value is between 0 and 1, where 0 represents that the aggregate is flaky and 1 represents that the aggregate is spherical, thereby realizing the needle-like and flaky detection of sand and gravel aggregate (7); In step S4, the aggregate is simplified into an ellipsoid for analysis. The projection of the ellipsoid is an ellipse. Let the relative length of the major semi-axis of the ellipse be 1, and the relative length of the minor semi-axis be... ,but ; This also serves as the final calculation result for the target, namely the aggregate thickness coefficient; In the tiling state, the projected area of ​​the ellipsoid is The total relative projection length is 2; the projected area of ​​the ellipsoid at a 60-degree tilt is The total relative projection length is set as ,and The total length of the minor axis of the ellipsoid's elliptical projection at this time That is, it is related to the thickness of the ellipsoid; at the same time, the circularity is defined. The calculation method is as follows: Subsequently, based on the following sphericity index formula, it can be concluded that the ratio of the total relative projected lengths in the two states is equal to the ratio of the projected areas, and also equal to the circularity in the two states. The ratio, i.e., the sphericity index The formula for the sphericity index is as follows: In the formula, The roundness of the sand and gravel aggregate in the first projected image; The roundness of the sand and gravel aggregate in the second projected image; Therefore, based on roundness and sphericity index This allows us to obtain the total relative projection length under a 60-degree tilt. Then and The mathematical relationship is determined as follows: Based on this mathematical relationship, the thickness coefficient of the aggregate is derived. ; Finally, the thickness coefficient of the aggregate is... Sphericity index The mathematical relationship is determined as follows: Based on this mathematical relationship, after the camera (2) captures the first and second projected images, the computer (6) calculates through the program to realize the needle-like and flaky detection of the sand and gravel aggregate (7).

4. The method for detecting needle-like and flaky particles in sand and gravel aggregates according to claim 3, characterized in that: and The derivation process of the mathematical relationship is as follows: For the elliptic projection of an ellipsoid, the formula for the ellipse is: In the formula, point Let be a point on the ellipse corresponding to the vertical projection boundary line under a 60-degree tilt; the formula for the slope of the ellipse is: The slope at the point of tangency of the ellipse is From this, we can conclude that: In the formula, For point The line connecting to the origin and The angle between axes; passing through point The total length of the elliptical projection axis relative to the origin for: Furthermore, we can deduce: This completes the derivation process.

5. The method for detecting needle-like and flaky textures in sand and gravel aggregates according to claim 4, characterized in that: Based on the derivation process and The mathematical relationship, due to the total relative projection length under a 60-degree tilt state. The ratio of the total relative projection length 2 in the tiled state to the ratio of the circularity of the two images is equal to the ratio of the circularity of the two images, i.e., the following formula: The thickness coefficient of the aggregate can then be obtained. Sphericity index The mathematical relationship.

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