A method and device for measuring the size and detecting defects of a ring-shaped workpiece

Abstract

The present invention discloses a method and device for measuring the size and detecting defects of annular workpieces. After the system is started, the annular workpiece enters the rotating disk; the fiber optic sensor monitors the rotating disk, and a trigger signal is generated when a workpiece passes through; the trigger signal is sent to the corresponding imaging and image acquisition stations respectively; after the imaging and image acquisition stations obtain the images, the original images are sent to the software platform, and the software platform uses the respective algorithm detection modules to perform detection based on the images of each station, etc. The detection speed of the present invention is relatively fast, the working speed can reach 500 per minute, the detection results have good robustness and strong stability, and it can work continuously for more than 12 hours. Currently, on the annular workpiece production line, this detection method can realize the size measurement of annular workpieces and the detection of annular workpieces at a relatively fast speed, and its detection speed, accuracy, stability, and repeatability have great advantages in the market.

Description

Technical Field

[0001] The present invention relates to the field of workpiece manufacturing and processing, and specifically, to a method and device for measuring the size and detecting defects of a ring-shaped workpiece. Background Art

[0002] For the existing related detection methods in the market, the detection speed for ring-shaped workpieces is relatively low, or the detection speed is sufficient but the measurement accuracy is not high. It is impossible to accurately identify a circle, and the accuracy rate is insufficient, so it cannot be applied to an automated production line. This method uses image processing technology to better achieve the accurate measurement of the surface size, height measurement, and surface defect detection of ring-shaped workpieces in a fast production scenario. Summary of the Invention

[0003] In view of the technical problems of the existing technology, the present invention discloses a method and device for measuring the size and detecting defects of a ring-shaped workpiece, and the present invention is realized through the following technical solutions:

[0004] The present invention discloses a method for quickly measuring the size and detecting defects of a ring-shaped workpiece, including the following steps:

[0005] 1) After the system is started, the ring workpiece enters the rotating disk;

[0006] 2) The fiber optic sensor monitors the rotating disk, and a trigger signal is generated when a workpiece passes through;

[0007] 3) The trigger signal is respectively sent to the corresponding imaging and image acquisition workstations;

[0008] 4) After the imaging and image acquisition workstation obtains an image, the original image is sent to the software platform, and the software platform uses the respective algorithm detection modules to detect according to the images of each workstation;

[0009] 5) After the result is fed back to the software platform, the data is recorded and the detection result is displayed in real time;

[0010] 6) After leaving the detection platform, the result is processed. If it is unqualified, it is blown off by a blowing nozzle; if the detection result is qualified, it is transferred to the subsequent workstation, and a single detection is completed.

[0011] As a further improvement, in step 4) of the present invention, the respective algorithm detection modules for the images of each workstation are a surface size measurement detection module, a height measurement detection module, and a surface defect detection module.

[0012] As a further improvement, the surface dimension measurement and detection module of the present invention captures images through backlight illumination, performs circle detection using the iteratively optimized least squares method, and calculates the center of the circle and the inner and outer diameters; the height measurement and detection module captures images through backlight illumination, separates the base through morphological processing to obtain a circular ring contour, sets the lower surface as the reference line, and measures the height range; the surface defect detection module captures images through high-angle illumination, and designs detection indexes for different forms of each defect to judge the defects.

[0013] As a further improvement, the specific algorithm of the surface dimension measurement and detection module of the present invention is as follows:

[0014] 1) Perform a general image processing process on the image, including filtering and denoising, image segmentation, and edge detection;

[0015] 2) To accelerate the detection speed, use the boundary tracking algorithm to extract contour points, and the search strategy is eight-connected boundary search;

[0016] 3) Use the contour points for iterative least squares circle detection to achieve center positioning and measure the inner and outer diameters of the annular workpiece;

[0017] 4) Utilize the fact that the random error is normally distributed and the setting of the error distance to perform formula derivation and calculation to obtain the center of the circle and its inner and outer diameters.

[0018] As a further improvement, the specific algorithm of the height measurement and detection module of the present invention is as follows:

[0019] 1) Utilize the gray information to separate the background and extract the overall contour;

[0020] 2) Remove the base through morphological processing of the contour to obtain a circular ring contour;

[0021] 3) Select appropriate upper and lower edges to calculate the height. Considering the large depth of field on the side and the uneven height of the upper surface, obtain the height range of the circular ring, and as long as it is within the allowable error range, it can be regarded as a qualified product.

[0022] As a further improvement, the specific algorithm of the surface defect detection module of the present invention is as follows:

[0023] 1) Perform surface defect detection on the annular workpiece to be measured, and capture images using high-angle illumination;

[0024] 2) For flattened and scratched defects: Use morphological processing to perform dilation and erosion on them, close small holes, and then judge whether there are defects by detecting the size and number of bright spots;

[0025] 3) For corrosion defects: Extract the edge points with gray level mutation and statistically analyze the distribution of their distances relative to the center of the circle; Judge whether there are defects by whether the peak value of the number of edge points exceeds the set threshold.

[0026] 4) For misalignment defects: Design an index for the change rate of the curvature radius of the inner and outer contours; at the contour misalignment, there will be an obvious peak in the change rate of the curvature radius, and it can be judged whether there is a defect by whether the peak value of the change rate of the curvature radius exceeds the set threshold.

[0027] 5) For burr defects and missing defects: Use the iterative erosion technique to process the circular ring contour to enhance the difference of the contour, and then use the index of the change rate of the curvature radius, and use a detection scheme similar to that for misalignment to make a judgment.

[0028] As a further improvement, in step 4) of the present invention, an index for the change rate of the curvature radius of the inner and outer contours is designed, and this index is defined as where point c is the center coordinate, points p1 and p2 are the coordinates of two adjacent points on the contour, traverse the entire contour to calculate the change rate of the curvature radius, statistically analyze and draw its broken line change diagram, △r is the radius difference, r1 and r2 are the radius values of adjacent points, s is the arc length, and d represents the distance between two points.

[0029] The present invention also discloses a device for rapid dimensional measurement and defect detection of annular workpieces. The device includes a frustum of a cone, and a fiber optic sensor, a surface dimensional measurement device, a height measurement device, and a surface defect detection device are sequentially arranged above the periphery of the frustum of a cone.

[0030] As a further improvement, a camera is provided on the surface dimensional measurement device of the present invention, and the camera is located directly above the workpiece.

[0031] As a further improvement, a telecentric lens is provided on the height measurement device of the present invention, and the telecentric lens is located on the side of the workpiece.

[0032] As a further improvement, the surface defect detection device of the present invention includes a camera and an annular LED light source located in front of the camera. The camera faces the central through hole of the annular light source, and the LED light source is red.

[0033] The beneficial effects of the present invention are as follows:

[0034] 1. The detection speed is relatively fast, and the working speed can reach 500 per minute;

[0035] 2. At a speed of 500 per minute, the measurement accuracy is high and the defect detection accuracy is high;

[0036] 3. The detection result has good robustness, strong stability, and can continuously work for more than 12 hours.

[0037] 4. Currently, in the annular workpiece production line, this detection method can realize the dimensional measurement of circular ring workpieces and the detection of annular workpieces at a relatively fast speed. Its detection speed, accuracy, stability, and repeatability have great advantages in the market. Brief Description of the Drawings

[0038] Figure 1 is the device detection flow chart of the present invention;

[0039] Figure 2 is the schematic diagram of the station layout device of the present invention.

[0040] In the figure, 1 - fiber optic sensor, 2 - surface dimension measuring device, 3 - height measuring device, 4 - telecentric lens, 5 - surface defect detection device, 6 - annular LED. Detailed Embodiments

[0041] The present invention discloses a method and device for rapid dimension measurement and defect detection of annular workpieces, Figure 1 is the device detection flow chart of the present invention, as shown in the figure:

[0042] Step 1: After the system is started, the annular workpiece enters the rotating disk;

[0043] Step 2: The fiber optic sensor (1) monitors the rotating disk, and a trigger signal is generated when a workpiece passes through;

[0044] Step 3: The trigger signal is sent to three imaging and image acquisition stations respectively, Figure 2 is the schematic diagram of the station layout device of the present invention, and the devices of each station are shown as Figure 2 shown.

[0045] Step 4: After the imaging and image acquisition station obtains the image, the original image is sent to the software platform, and the software platform uses different algorithm detection modules to detect according to the images of different stations. The main detection principle is as follows:

[0046] 1) At station one, the surface dimensions of the annular workpiece to be measured are measured, and backlight illumination is used for image acquisition. First, a general image processing process is performed on the image, including filtering and denoising, image segmentation, and edge detection. Then, to speed up the detection, a boundary tracking algorithm is used to extract contour points, and the search strategy is an eight-connected boundary search. Finally, an iterative least squares circle detection is performed using the contour points to achieve center positioning and measure the inner and outer diameters of the annular workpiece. By using the fact that the random error is normally distributed and setting the error distance, formula derivation and calculation are carried out to obtain the center and its inner and outer diameters.

[0047] 2) At station two, the height of the annular workpiece to be measured is measured, and backlight illumination is used for image acquisition. First, the background is separated using the gray information, and the overall contour is extracted. Then, the base is removed from the contour through morphological processing to obtain the annular contour. Finally, appropriate upper and lower edges are selected to calculate the height. Considering that the depth of field on the side is relatively large and the height of the upper surface is uneven, the height range of the obtained ring is obtained, and as long as it is within the allowable error range, it can be regarded as a qualified product.

[0048] 3) Station 3: Perform surface defect detection on the ring-shaped workpiece to be measured and capture images using high-angle illumination. The ring-shaped workpiece mainly has defects such as flattening, corrosion, misalignment, burrs, and missing parts. The detection principles for each defect are different. Integrate and optimize them to accelerate the detection speed. For flattening and scratch defects, use morphological processing, perform dilation and erosion on them to bridge small holes, and then judge whether there are defects by detecting the size and quantity of bright spots. For corrosion defects, extract the edge points with gray-scale mutation and statistically analyze the distribution of their distances relative to the center of the circle. Judge whether there are defects by whether the peak value of the number of edge points exceeds the set threshold. For misalignment defects, design an index for the change rate of the curvature radius of the inner and outer contours. Design an index for the change rate of the curvature radius of the inner and outer contours, which is defined as where point c is the center coordinate, points p1 and p2 are the coordinates of two adjacent points on the contour. Traverse the entire contour to calculate the change rate of the curvature radius, statistically analyze and draw its broken-line change graph. △r is the radius difference, r1 and r2 are the radii of adjacent points, s is the arc length, and d represents the distance between two points. At the misaligned part of the contour, there will be an obvious peak in the change rate of the curvature radius. It can be judged whether there are defects by whether the peak value of the change rate of the curvature radius exceeds the set threshold. For burr and missing defects, use iterative erosion technology to process the ring contour to enhance the difference of the contour. Then use the index of the change rate of the curvature radius and use a detection scheme similar to misalignment to make a judgment. Finally, comprehensively process all detection results to judge whether the ring-shaped workpiece to be measured is qualified.

[0049] Step 5: After the result is fed back to the software platform, record the data and display the detection result in real time.

[0050] Step 6: Leave the detection platform and process the result. If it is unqualified, blow it off using a blowing nozzle.

[0051] Step 7: If the detection result is qualified, transfer it to the subsequent station, and a single detection is completed.

[0052] The present invention also discloses a device for rapid dimensional measurement and defect detection of a ring-shaped workpiece, including a surface dimension measurement device, a height measurement device (3), and a surface defect detection device (5). A camera is provided on the surface dimension measurement device (2), and the camera is located directly above the workpiece. The surface dimension detection device detects the surface dimension of the workpiece through a surface dimension detection module; a telecentric lens (4) is provided on the height measurement device (3), and the telecentric lens (4) is located on the side of the workpiece. The height of the workpiece is measured through a height detection module; the surface defect detection device (5) includes a camera and an annular LED (6) light source located in front of the camera. The camera faces the central through-hole of the annular light source. The LED light source is red, and the defects of the workpiece are detected through a surface defect detection module.

[0053] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for measuring the size and detecting defects of a ring-shaped workpiece, characterized in that, It includes the following steps: 1) After the system starts, the ring workpiece enters the rotating disc; 2) The fiber optic sensor (1) monitors the rotating disc, and a trigger signal is generated when a workpiece passes through; 3) The trigger signal is sent to the corresponding imaging and image acquisition stations respectively; 4) After the imaging and image acquisition stations obtain the images, the original images are sent to the software platform, and the software platform uses the respective algorithm detection modules for detection according to the images of each station; 5) After the results are fed back to the software platform, the data is recorded and the detection results are displayed in real time; 6) Leave the detection platform, process the results. If unqualified, blow it off with a blowing nozzle; if the detection result is qualified, transfer it to the subsequent station, and a single detection is completed; In step 4) above, the images of each station use the respective algorithm detection modules, namely the surface dimension measurement detection module, the height measurement detection module, and the surface defect detection module; The specific algorithm of the surface defect detection module is as follows: 1) Conduct surface defect detection on the ring workpiece to be measured, and use high-angle illumination for image acquisition; 2) For flattening and scratching defects: Use morphological processing, perform dilation and erosion on it, close small holes, and then judge whether there are defects by detecting the size and quantity of bright spots; 3) For corrosion defects: Extract the edge points with gray level mutation, and statistically analyze the distribution of their distances relative to the center of the circle; 4) For misalignment defects: Design the curvature radius change rate index of the inner and outer contours; 5) For burr defects and missing defects; Use iterative erosion technology to process the ring contour, enhance the difference of the contour, and then use the curvature radius change rate index and the detection scheme for misalignment to make a judgment; In step 4) of the specific algorithm of the surface defect detection module, a curvature radius change rate index for the inner and outer contours is designed, and this index is defined as where point c is the center coordinate, points p1 and p2 are the coordinates of two adjacent points on the contour. Traverse the entire contour to calculate the curvature radius change rate, statistically analyze and draw its broken line change diagram. △r is the radius difference, r1 and r2 are the radii of adjacent points, s is the arc length, and d represents the distance between two points.

2. The method for measuring the size and detecting the defects of the ring-shaped workpiece according to claim 1, characterized in that, The surface dimension measurement detection module performs image acquisition through backlight illumination, uses the least squares method with iterative optimization for circle detection, and calculates the center of the circle and the inner and outer diameters; the height measurement detection module performs image acquisition through backlight illumination, uses morphological processing to separate the base, obtains the ring contour, sets the lower surface as the reference line, and measures the height range; the surface defect detection module performs image acquisition through high-angle illumination, and designs detection indexes for different forms of each defect to judge the defects.

3. The method for measuring the size and detecting the defects of the ring workpiece according to claim 1 or 2, characterized in that The specific algorithm of the surface dimension measurement detection module is as follows: 1) Perform an image processing process on the image, filter and denoise, image segmentation, and edge detection; 2) To speed up the detection speed, use the boundary tracking algorithm to extract contour points, and the search strategy is eight-connected boundary search; 3) Use the contour points for iterative least squares circle detection to achieve center positioning and measure the inner and outer diameters of the ring workpiece; 4) Utilize that the random error is normally distributed and the setting of the error distance to perform formula derivation and calculation to obtain the center of the circle and its inner and outer diameters.

4. The method for measuring the size and detecting the defects of the annular workpiece according to claim 3, wherein The specific algorithm of the height measurement detection module is as follows: 1) Utilize the gray level information to separate the background and extract the overall contour; 2) Remove the base through morphological processing of the contour to obtain the ring contour; 3) Select appropriate upper and lower edges to calculate the height.

5. A device for measuring the size and detecting defects of a ring-shaped workpiece, which is used to perform the method for measuring the size and detecting defects of the ring-shaped workpiece according to any one of claims 1-4, characterized in that, The device includes a frustum, and a fiber optic sensor (1), a surface dimension measurement device (2), a height measurement device (3), and a surface defect detection device (5) are sequentially arranged above the periphery of the frustum.

6. The annular workpiece size measuring and defect detecting device according to claim 5, characterized in that, A telecentric lens (4) is provided on the height measuring device (3), and the telecentric lens (4) is located on the side of the workpiece.

7. The annular workpiece size measuring and defect detecting device according to claim 5 or 6, characterized in that, The surface defect detection device (5) includes a camera and an annular LED (6) light source located in front of the camera. The camera faces the central through hole of the annular LED (6) light source, and the LED light source is red.

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