An in-situ detection device and method for grinding wheel wear condition

Abstract

This invention relates to an in-situ detection device and method for the wear state of a grinding wheel. The device includes a grinding wheel, an optical camera, and a camera bracket. The optical camera is fixed on the camera bracket, which is mounted on a machine tool and can move laterally, longitudinally, and vertically, as well as adjust the shooting angle. The lateral movement direction is perpendicular to the end face of the grinding wheel. The in-situ detection method for the wear state of a grinding wheel of this invention involves: firstly, using the optical camera to capture the three-dimensional microstructure of the grinding wheel; then, after image processing, obtaining a digitized three-dimensional microstructure of the grinding wheel; next, based on the interference depth between the abrasive grains of the grinding wheel and the workpiece under actual processing conditions, extracting a two-dimensional image of the grinding wheel surface at a specific depth; calculating the fractal dimension of the two-dimensional image based on fractal theory; and finally, determining the wear state of the grinding wheel by using the calculated fractal dimension of the grinding wheel surface.

Description

Technical Field

[0001] This invention relates to a precision grinding process inspection device and method, and more particularly to an in-situ inspection method and device for grinding wheel wear condition. Background Technology

[0002] In industrial manufacturing, grinding is an indispensable part of many machining processes, and the grinding wheel is the most important tool in grinding. During the grinding process, the wear condition of the grinding wheel directly affects the machining quality and efficiency. Therefore, the detection of the wear condition of the grinding wheel is particularly important.

[0003] Traditional methods for detecting grinding wheel wear rely primarily on worker experience, judging by the sounds heard during processing and the surface quality of the workpiece. This requires highly experienced workers, is subjective, and increases labor costs. Furthermore, current methods for detecting grinding wheel wear also utilize signals such as acoustic emission, electric current, and force; however, these methods are qualitative and cannot provide quantitative detection, leading to inaccuracies. Therefore, developing a highly accurate and easily implemented detection device and method for in-situ wear detection is a pressing issue in the current technological field.

[0004] During grinding, wear of the grinding wheel leads to gradual dulling of the grinding edges. Some dulled abrasive grains may detach or break, resulting in a self-sharpening effect. The resulting grinding wheel debris and swarf remain on the grinding wheel surface, clogging the pores and increasing the solid area within the area measurement scale. Consequently, the calculated fractal dimension of the grinding wheel surface also increases. The calculated fractal dimension of the grinding wheel surface can be used to quantitatively determine the wear state of the grinding wheel. By comparing the calculated fractal dimension with a calibrated threshold, it can be determined whether the grinding wheel needs dressing. Summary of the Invention

[0005] In view of the above-mentioned technical shortcomings, the technical problem to be solved by the present invention is that the existing technology has low detection efficiency, low detection accuracy and cannot achieve quantitative detection. The present invention provides an in-situ detection device and method for grinding wheel wear state.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is: an in-situ detection device for the wear state of a grinding wheel, comprising a grinding wheel, an optical camera with depth-of-field function, a camera bracket, and a moving platform capable of lateral movement, wherein the camera bracket is installed at one end of the moving platform and the moving direction of the camera bracket is parallel to the working surface of the grinding wheel; the optical camera is installed on the camera bracket and its angle can be adjusted to keep the optical camera facing the working surface of the grinding wheel.

[0007] Furthermore, the camera bracket includes a camera box, an electric actuator, a motor, and a ball screw. The camera box is used to fix the optical camera. The bottom of the camera box is hinged to the screw nut of the ball screw. An electric actuator is also connected between the camera box and the screw nut. The electric actuator is used to adjust the shooting angle of the optical camera. The motor is connected to the ball screw and is used to drive the ball screw so that the optical camera can move parallel to the working surface of the grinding wheel.

[0008] A method for in-situ detection of grinding wheel wear condition, employing an in-situ detection device for grinding wheel wear condition, comprising the following steps:

[0009] S1. The three-dimensional shape of the grinding wheel is captured by an optical camera with depth of field function. The data information of the photo is read by the calculation software, and the three-dimensional shape of the grinding wheel is constructed in the Cartesian coordinate system after spectral analysis.

[0010] S2, based on the interference depth between the abrasive grains of the grinding wheel and the workpiece under actual processing conditions, a two-dimensional cross-section of the grinding wheel topography at an appropriate depth is selected, and the total area S of the solid phase of the grinding wheel within the cross-section is calculated using calculation software. s ;

[0011] S3. The fractal dimension of the grinding wheel is determined using the scale method. First, it is assumed that the grinding wheel is composed of several cubic microstructures uniformly distributed throughout the space. The microstructures include the solid phase and pores of the grinding wheel. On any cross section of the microstructure of the grinding wheel, the solid phase area S changes with the area measurement scale X, exhibiting self-similarity. Thus, the fractal dimension of the grinding wheel surface can be calculated.

[0012] S4, during the grinding process, the fractal dimension of the grinding wheel under different conditions is calculated by taking in-situ photos of the grinding wheel morphology with an optical camera and then calibrated. The analytical dimension threshold standard for the grinding wheel that needs to be dressed is given, so as to accurately and quantitatively determine the wear state of the grinding wheel.

[0013] Further, in step S1, spectral analysis calculation is performed, that is, the image information captured by the camera is transformed from the spatial domain to the frequency domain using Fourier transform, and then the three-dimensional surface of the grinding wheel is represented by the function Z(x, y) in the Cartesian coordinate system, where the value of Z is the height value at position (x, y). For a three-dimensional surface digital M×N array Z(x... i y i ), 1≤i≤M, 1≤i≤N, its two-dimensional discrete Fourier transform is

[0014]

[0015] Where p = 0, 1, ..., M-1, q = 0, 1, ..., N-1; and the spatial frequency u along the x and y directions. p v q They are respectively

[0016]

[0017] In equation (2), Δx and Δy are the sampling intervals of discrete points; the function Z(x i y i The Fourier transform of is a complex quantity, denoted as

[0018] F(u p v q )=R(u p v q )+jL(u p v q (3)

[0019] Therefore, the three-dimensional surface is decomposed into a series of sine waves.

[0020]

[0021] The frequency of the sine wave is .

[0022]

[0023] Furthermore, in step S2, according to the definition of fractal dimension, the fractal dimension of a grinding wheel is related to the metric scale of the calculated area and the average area of ​​the solid phase of the grinding wheel within that scale. The grinding wheel will have different fractal dimensions under different wear states, as defined in the following formula:

[0024] S(X)∝X D (6)

[0025] Where X is the area measurement scale; S(X) is the average area of ​​the solid phase of the grinding wheel under the measurement scale X; and D is the fractal dimension of the solid phase of the grinding wheel cross section.

[0026] Furthermore, in step S2, the two-dimensional image is imported into the drawing software, and many square grids are drawn on the image. Since the grid side length δ i It is variable, the area measurement scale Xi = δ i *δ i The average area S of the solid phase in the grinding wheel i Equal to the total area S of the solid phase in the grinding wheel s Divide by the number of grids, then change the side length δ of the square grid. i This yields a series of corresponding area measurement scales X. i The average area S of the solid phase of the grinding wheel i Substituting the data of X and S into equation (6), and taking the logarithm of both sides, we obtain equation (7).

[0027] lnS=C+DlnX (7)

[0028] Where C is a constant.

[0029] Furthermore, in step S3, the ruler method is a method that uses geometric figures with characteristic lengths, such as squares, line segments, circles, and spheres, to approximate fractal figures, thereby achieving approximate measurement of the figures. Based on the ruler method, the box dimension method is derived. The measurement results of the research object need to satisfy formula (8).

[0030] N(l)∝l D (8)

[0031] Where N(l) is the measurement result of l when the metric scale is l, l is the metric scale; D is the fractal dimension of the research object.

[0032] The beneficial effects of this invention are:

[0033] This invention comprehensively utilizes experimental testing and theoretical analysis. Starting from the microscopic morphology and based on fractal theory, it analyzes the internal composition and structure of the grinding wheel and calculates its fractal dimension to determine the wear state of the grinding wheel. The device and method are simple and accurate to operate, and can quantitatively determine the wear state of the grinding wheel, providing guidance for optimizing the grinding process. Attached Figure Description

[0034] Figure 1 This is a flowchart of the in-situ detection method for the wear state of the grinding wheel according to the present invention;

[0035] Figure 2 This is a schematic diagram of the in-situ imaging process implemented by the in-situ detection device for the wear state of the grinding wheel according to the present invention;

[0036] Figure 3 This is a schematic diagram of the camera bracket structure;

[0037] Figure 4 , Figure 5 This is a cross-sectional view of a normal 80# resin diamond grinding wheel with a particle size of 20μm. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0039] like Figure 2 As shown, an embodiment of the present invention provides an in-situ detection device for the wear state of a grinding wheel, including a grinding wheel 1, an optical camera 2 with a depth-of-field function, a camera bracket 3, and a moving platform 4 capable of lateral movement. The camera bracket 3 is mounted on one end of the moving platform 4, and the moving direction of the camera bracket 3 is parallel to the working surface of the grinding wheel 1. The optical camera 2 is mounted on the camera bracket 3, and its angle can be adjusted to keep the optical camera 2 facing the working surface of the grinding wheel 1.

[0040] like Figure 3As shown, the camera bracket 3 includes a camera housing 31, an electric actuator 32, a motor 33, and a ball screw 34. The camera housing 31 is used to fix the optical camera 2. The bottom of the camera housing 31 is hinged to the screw nut of the ball screw 34. The electric actuator 32 is also connected between the camera housing 31 and the screw nut. The electric actuator 32 is used to adjust the shooting angle of the optical camera 2. The motor 33 is connected to the ball screw 34 and is used to drive the ball screw 34 so that the optical camera 2 can move parallel to the working surface of the grinding wheel 1.

[0041] like Figure 1 As shown in the figure, an embodiment of the present invention provides an in-situ detection method for the wear state of a grinding wheel, which employs an in-situ detection device for the wear state of a grinding wheel, and the steps are as follows:

[0042] S1 uses an optical camera with depth-of-field function to capture the three-dimensional shape of the grinding wheel, uses calculation software to read the data information of the photo, and after spectrum analysis, constructs the three-dimensional shape of the grinding wheel in the Cartesian coordinate system.

[0043] The optical camera 3 captures the three-dimensional morphology of a normal grinding wheel and a grinding wheel that needs to be repaired after wear. The MATLAB software is used to read the image information, and the spatial domain signal is converted into a frequency domain signal through spectrum analysis. Then, the three-dimensional morphology of the grinding wheel is represented in the Cartesian coordinate system.

[0044] Example: Figure 4 , Figure 5 The image shows the import of 3D geomorphological data of the grinding wheel into MATLAB. Using MATLAB's numerical calculation capabilities, a 400×400 pixel 2D image of the grinding wheel cross-section at a depth of 20 μm is obtained. The black areas represent the solid phase structure of the grinding wheel, and the white areas represent pores. The total area S of the solid phase within the cross-section is then calculated. s ;

[0045] The obtained two-dimensional image is imported into drawing software, and a square grid is drawn on the image. The side length (δi) of the grid is variable. The area measurement scale Xi = δikδi. The average area Si of the solid phase of the grinding wheel is equal to the total area Ss of the solid phase of the grinding wheel divided by the number of grids. By changing the side length δi of the square grid, a series of corresponding area measurement scales Xi and the average area Si of the solid phase of the grinding wheel can be obtained. Substituting the data of X and S into the formula lnS = C + DlnX, where C is a constant, then in the two-dimensional plane, the larger the solid phase area within the area measurement scale, the larger the fractal dimension, with a maximum value of 2.

[0046] In this example, we take f(x) = lnS and x = lnX respectively. Substituting the values ​​of S and X measured by the grinding wheel under two different conditions into the equation lnS = C + DlnX, we fit a straight line. The straight line expression for the normal grinding wheel is f(x) = 0.8815x + 0.05602, and the straight line expression for the grinding wheel that needs dressing is f(x) = 1.2143x - 0.08509. The grinding wheel surface has good self-similarity. The slopes of the straight lines, 0.8815 and 1.2143, are the fractal dimensions D1 and D2 of the normal grinding wheel and the grinding wheel that needs dressing, respectively. 0.05602 and -0.08509 are constants C1 and C2.

[0047] S12 involves spectrum analysis calculation, which uses Fourier transform to convert the image information captured by the camera from the spatial domain to the frequency domain, and then uses the function Z(x, y) to represent the three-dimensional surface of the grinding wheel in the Cartesian coordinate system, where the value of Z is the height value at position (x, y).

[0048] For a three-dimensional surface digital M×N array Z(x) i y i ), 1≤i≤M, 1≤i≤N, its two-dimensional discrete Fourier transform is

[0049] Where p = 0, 1, ..., M-1, q = 0, 1, ..., N-1; and the spatial frequency u along the x and y directions. p v q They are respectively

[0050]

[0051] In equation (2), Δx and Δy are the sampling intervals of discrete points; the function Z(x i y i The Fourier transform of is a complex quantity, which can be represented as

[0052] F(u p v q )=R(u p v q )+jL(u p v q (3)

[0053] Therefore, a three-dimensional surface can be decomposed into a series of sine waves.

[0054]

[0055] The frequency of the sine wave is .

[0056]

[0057] Based on the interference depth between the abrasive wheel and the workpiece under actual processing conditions, S2 selects a two-dimensional cross-section of the abrasive wheel topography at an appropriate depth, and uses calculation software to calculate the total area S of the abrasive wheel solid phase within the cross-section. s ;

[0058] According to the definition of fractal dimension, the fractal dimension of a grinding wheel is related to the metric scale of the calculated area and the average area of ​​the solid phase of the grinding wheel within that scale. Therefore, a grinding wheel will have different fractal dimensions under different wear conditions. The definition of fractal is as follows:

[0059] S(X)∝X D (6)

[0060] Where X is the area measurement scale; S(X) is the average area of ​​the solid phase in the grinding wheel under the measurement scale X; and D is the fractal dimension of the solid phase in the cross section of the grinding wheel.

[0061] S21 imports the two-dimensional image into the drawing software and draws many square grids on the image. Since the grid side length (δ) i The area measurement scale is variable, Xi = δ i *δ i The average area S of the solid phase in the grinding wheel i Equal to the total area S of the solid phase in the grinding wheel s Divide by the number of grids, then change the side length δ of the square grid. i This allows us to obtain a series of corresponding area measurement scales X. i The average area S of the solid phase of the grinding wheel i Substituting the data of X and S into equation (6), and taking the logarithm of both sides, we obtain equation (7).

[0062] lnS=C+DlnX (7)

[0063] Where C is a constant;

[0064] S3 uses the scale method to determine the fractal dimension of the grinding wheel. First, it is assumed that the grinding wheel is composed of several cubic microstructures uniformly distributed throughout the space. The microstructures include the solid phase and pores of the grinding wheel. On any cross section of the microstructure of the grinding wheel, the solid phase area S changes with the area measurement scale X, which has self-similarity, thus calculating the fractal dimension of the grinding wheel surface.

[0065] The ruler method uses geometric figures with characteristic lengths, such as squares, line segments, circles, and spheres, to approximate fractal figures, thereby achieving approximate measurement of the figures. Based on the ruler method, other methods such as the box dimension method (covering method) have been derived. Generally speaking, if the measurement results of the research object need to satisfy formula (8)

[0066] N(l)∝l D (8)

[0067] Where N(l) is the measurement result when the metric scale is l, l is the metric scale; D is the fractal dimension of the research object;

[0068] During the grinding process, S4 uses an optical camera to capture the morphology of the grinding wheel in situ, calculates the fractal dimension of the grinding wheel under different conditions, and then calibrates it to give the analytical dimension threshold standard for the grinding wheel to be dressed, thereby enabling accurate quantitative judgment of the wear state of the grinding wheel.

Claims

1. A method for in-situ detection of grinding wheel wear condition, employing an in-situ detection device for grinding wheel wear condition, the device comprising a grinding wheel, an optical camera with depth-of-field function, a camera bracket, and a laterally movable platform, the camera bracket being mounted at one end of the movable platform, and the movement direction of the camera bracket being parallel to the working surface of the grinding wheel; the optical camera being mounted on the camera bracket and adjustable in angle to maintain the optical camera facing the working surface of the grinding wheel; the camera bracket comprising a camera housing, an electric actuator, a motor, and a ball screw, the camera housing being used to fix the optical camera, the bottom of the camera housing being hinged to the screw nut of the ball screw, the electric actuator being connected between the camera housing and the screw nut, the electric actuator being used to adjust the shooting angle of the optical camera, and the motor being connected to the ball screw to drive the ball screw so that the optical camera can move parallel to the working surface of the grinding wheel, characterized in that… The steps of this method are as follows: S1. The three-dimensional shape of the grinding wheel is captured by an optical camera with depth of field function. The data information of the photo is read by the calculation software, and the three-dimensional shape of the grinding wheel is constructed in the Cartesian coordinate system after spectral analysis. S2, based on the interference depth between the abrasive grains of the grinding wheel and the workpiece under actual processing conditions, a two-dimensional cross-section of the grinding wheel morphology at an appropriate depth is selected, and the total area S of the solid phase of the grinding wheel within the cross-section is calculated using calculation software. s ; According to the definition of fractal dimension, the fractal dimension of a grinding wheel is related to the metric scale of the calculated area and the average area of ​​the solid phase of the grinding wheel within that metric scale. Grinding wheels will have different fractal dimensions under different wear conditions, as defined in the following formula: (1) in, It is a scale for measuring area; For measurement scale Below, the average area of ​​the solid phase in the grinding wheel; The solid-phase fractal dimension of the grinding wheel cross-section; Import the 2D image into the drawing software, and draw many square grids on the image. Due to the side length of the grid... It is variable, the area measurement scale. The average area of ​​the solid phase in the grinding wheel Equal to the total area of ​​the solid phase in the grinding wheel Divide by the number of grids, then change the side length of the square grid. This yields a corresponding series of area measurement scales. and the average area of ​​the solid phase of the grinding wheel ,Will and Substituting the data into equation (1) and taking the logarithm of both sides, we obtain equation (2). (2) Where C is a constant; S3. The fractal dimension of the grinding wheel is determined using the scale method. First, it is assumed that the grinding wheel is composed of several uniformly distributed cubic microstructures throughout the entire space. The microstructures include the solid phase and pores of the grinding wheel. On any cross-section of the microstructure of the grinding wheel, the solid phase area S changes with the area measurement scale X, exhibiting self-similarity, thereby calculating the fractal dimension of the grinding wheel surface. The scale method uses geometric figures with characteristic lengths, such as squares, line segments, circles, and spheres, to approximate fractal figures, thereby achieving approximate measurement of the figures. Based on the scale method, the box dimension method is derived. The measurement results of the research object need to satisfy formula (3). (3) in, The metric is The measurement results As a measurement scale; D The fractal dimension of the object under study; S4, during the grinding process, the fractal dimension of the grinding wheel under different conditions is calculated by taking in-situ photos of the grinding wheel morphology with an optical camera and then calibrated. The analytical dimension threshold standard for the grinding wheel that needs to be dressed is given, so as to accurately and quantitatively determine the wear state of the grinding wheel.

2. The in-situ detection method for grinding wheel wear condition according to claim 1, characterized in that: In step S1, spectrum analysis calculation involves using Fourier transform to convert the image information captured by the camera from the spatial domain to the frequency domain, and then applying a function in the Cartesian coordinate system. To represent the three-dimensional surface of the grinding wheel, where Z The value is the position. The height value for a three-dimensional surface digital M×N Array , , Its two-dimensional discrete Fourier transform is (4) in p=0,1,…,M-1, q=0,1,…,N-1; along x, y Spatial frequency of direction u p 、v q They are respectively (5) In formula (5) The sampling interval for discrete points; function The Fourier transform of is a complex quantity, denoted as (6) Therefore, the three-dimensional surface is decomposed into a series of sine waves. (7) The frequency of the sine wave is . (8)。

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