Plate punching control method and system using heat treatment punch

Abstract

The invention relates to the technical field of metal stamping, in particular to a plate stamping control method and system using a heat treatment punch, and the method comprises the steps: collecting a surface grayscale image of a stamping part after each time of stamping in a plate stamping process, and determining the shape approximation degree of each edge contour in the surface grayscale image after each time of stamping; determining a form evaluation value of each edge contour in the surface gray level image after each time of stamping; determining a wrinkling cross coefficient of each edge contour in the surface grayscale image after each time of stamping; determining a wrinkling change coefficient of each edge contour in the surface grayscale image after each time of stamping, and determining a wrinkling interference coefficient of each edge contour in the surface grayscale image after each time of stamping; and the wrinkling judgment coefficient of the surface gray level image after each time of punching is determined, and a punching machine in the punching process is controlled and adjusted. The accuracy of detecting the edge contour formed by the wrinkling phenomenon on the surface of the stamping part is improved, and then accurate control over the stamping machine by a stamping control system is improved.

Description

Technical Field

[0001] The present application relates to the field of metal stamping technology, and in particular to a plate stamping control method and system using a heat-treated punch. Background Art

[0002] Stamping is to apply external force to the sheet by the punching machine and the die to make it plastically deform or separate, so as to obtain the stamped workpiece of the required shape and size. Hot stamping forming technology, which uses the principle of metal thermoplastic forming and the stamping process of special heat-treated punches, can achieve quenching heat treatment of the sheet while forming, improve the forming performance of the material, and greatly expand the application range of high-strength and ultra-high-strength steel.

[0003] During the stamping process, the control system of the stamping machine usually needs to pre-set stamping parameters. However, there are many materials that are processed by stamping, and there are certain differences in strength, thickness, and processing environment between the materials. The pre-set stamping parameters may not match the actual stamping situation, causing some materials to have defects such as cracking, wrinkling, and rebound during the stamping process, affecting the quality of the stamped parts. Therefore, the quality of the stamped parts is inspected by visual means, and then the stamping parameters of the stamping control system are adjusted to ensure the overall stamping quality of the stamped parts. However, during the production and processing of stamped parts, there will be many stripes on its surface, and when the surface wrinkles, there will be more stripes on the surface of the stamped parts. It is difficult to detect whether the surface of the stamped parts is wrinkled during the visual inspection, resulting in errors in the quality inspection of the stamped parts, affecting the production quality. Summary of the invention

[0004] In order to solve the above technical problems, a plate stamping control method and system using a heat-treated punch are provided to solve the existing problems.

[0005] The solution to the technical problem of the present application is to provide a plate stamping control method and system using a heat-treated punch, comprising the following steps: In a first aspect, an embodiment of the present application provides a plate stamping control method using a heat-treated punch, the method comprising the following steps: Collect the grayscale image of the stamped part surface after each stamping process in the sheet metal stamping process, and extract each edge contour in the grayscale image of the surface after each stamping process; According to the main extension direction of any edge contour in the surface grayscale image after each stamping, determine the direction characterization line of any edge contour; analyze the difference in direction and length of the direction characterization line of each edge contour and the other edge contours, and determine the morphological similarity of each edge contour in the surface grayscale image after each stamping; according to the density of distribution between different edge contours and the fluctuation of the grayscale value of the pixel points around each edge contour, determine the density fluctuation coefficient of each edge contour in the surface grayscale image after each stamping, and combine the morphological similarity and the density fluctuation coefficient to determine the morphological evaluation value of each edge contour in the surface grayscale image after each stamping; According to the discreteness of the distance between the endpoint and the intersection point on the skeleton extracted from each edge contour, and the number of the endpoint and the intersection point, the wrinkle cross coefficient of each edge contour in the surface grayscale image after each stamping is determined; the difference in the number of edge contours in the surface grayscale image after two adjacent stampings, and the difference in the number of edge pixels on the edge contours at the same position are analyzed to determine the wrinkle variation coefficient of each edge contour in the surface grayscale image after each stamping, and the wrinkle cross coefficient is combined to determine the wrinkle interference coefficient of each edge contour in the surface grayscale image after each stamping; Based on the morphological evaluation values ​​and the wrinkle interference coefficients of all edge contours in the surface grayscale image after each stamping, the wrinkle discrimination coefficient of the surface grayscale image after each stamping is determined; based on the wrinkle discrimination coefficient of the surface grayscale images after all stampings before the current stamping, the stamping machine of the stamping process is controlled and adjusted.

[0006] Preferably, determining the direction characterizing line of any edge contour comprises: The line between the edge pixel point with the smallest horizontal coordinate and the edge pixel point with the largest horizontal coordinate on any edge contour is recorded as a horizontal line; The line between the edge pixel point with the smallest ordinate and the edge pixel point with the largest ordinate on any edge contour is recorded as a vertical line; Counting the number of all pixels on the horizontal line, and recording it as the horizontal length; counting the number of all pixels on the vertical line, and recording it as the vertical length; If the horizontal length is greater than or equal to the vertical length, the horizontal connection line is used as the direction characterizing line of any edge contour; otherwise, the vertical connection line is used as the direction characterizing line of any edge contour.

[0007] Preferably, the determining of the morphological similarity of each edge contour in the surface grayscale image after each punching comprises: Obtaining the slope of the direction characterization line of any edge contour and the number of all pixel points on the direction characterization line; The average of the differences in the slopes between any one edge profile and all other edge profiles in the surface grayscale image after each punching is used as the direction difference coefficient of any one edge profile; The average of the differences in the number between any one edge contour and all other edge contours in the surface grayscale image after each punching is used as the length difference coefficient of any one edge contour; The reciprocal of the sum of the direction difference coefficient and the length difference coefficient is used as the morphological approximation of each edge contour in the surface grayscale image after each punching.

[0008] Preferably, the determining of the dense fluctuation coefficient of each edge contour in the surface grayscale image after each punching, combining the morphological similarity and the dense fluctuation coefficient, and determining the morphological evaluation value of each edge contour in the surface grayscale image after each punching, comprises: The average of the distances between the centroid of each edge contour and the centroids of all other edge contours in the surface grayscale image after each punching is taken as the distribution coefficient of each edge contour; Calculate the discrete degree of the grayscale values ​​of all pixels within the minimum circumscribed rectangle of each edge contour in the surface grayscale image after each punching; The ratio of the discrete degree to the distribution coefficient is used as the intensive fluctuation coefficient of each edge contour in the surface grayscale image after each punching; The product of the morphological similarity and the dense fluctuation coefficient is used as the morphological evaluation value of each edge contour in the surface grayscale image after each punching.

[0009] Preferably, the wrinkle cross coefficient of each edge contour in the surface grayscale image after each punching is determined, comprising: The grayscale values ​​of edge pixels in the surface grayscale image after each punching are assigned to 1, and the grayscale values ​​of non-edge pixels are assigned to 0, to obtain a binary image, and the skeletons of all edge contours in the binary image are extracted, and the pixels on the skeletons are recorded as skeleton pixels; If there is only one skeleton pixel point in the eight-neighborhood of any skeleton pixel point on the skeleton corresponding to each edge contour, the any skeleton pixel point is recorded as a skeleton endpoint; if there are multiple skeleton pixels in the eight-neighborhood of any skeleton pixel point on the skeleton corresponding to each edge contour, the any skeleton pixel point is recorded as a skeleton intersection point; Count the number of all skeleton endpoints and skeleton intersections on the skeleton corresponding to each edge contour, and record it as the number of bifurcations; The minimum value of the distance between each skeleton endpoint and all skeleton intersection points on the skeleton corresponding to each edge contour is recorded as the closest distance; Calculate the discrete degree of the nearest distances of all skeleton endpoints on the skeleton corresponding to each edge contour, recorded as distance discreteness; The ratio of the number of bifurcations to the distance dispersion is used as the wrinkle cross coefficient of each edge contour in the surface grayscale image after each punching.

[0010] Preferably, the step of determining the wrinkle variation coefficient of each edge contour in the surface grayscale image after each punching comprises: The difference between the number of all edge contours in the grayscale image of the surface after each punching and the number of all edge contours in the grayscale image of the surface after the adjacent punching is recorded as a first quantity difference; The centroid coordinates of each edge contour in the grayscale image of the surface after each punching and the edge contour with the same centroid coordinates in the grayscale image of the surface after the adjacent punching are recorded as the relative edge contour of each edge contour; Recording the difference between the number of all edge pixels on each edge contour and the number of all edge pixels on the relative edge contour as a second quantity difference; The sum of the first quantity difference and the second quantity difference is used as the wrinkle variation coefficient of each edge contour in the surface grayscale image after each punching.

[0011] Preferably, the wrinkle interference coefficient of each edge contour in the surface grayscale image after each punching is the product of the wrinkle cross coefficient and the wrinkle variation coefficient.

[0012] Preferably, the step of determining the wrinkle discrimination coefficient of the surface grayscale image after each punching comprises: The product of the morphological evaluation value and the wrinkling interference coefficient is used as a discriminant factor of each edge contour in the surface grayscale image after each punching; The average value of the discrimination factors of all edge contours in the surface grayscale image after each punching is used as the wrinkle discrimination coefficient of the surface grayscale image after each punching.

[0013] Preferably, the control and adjustment of the punching machine in the punching process includes: Performing threshold segmentation on the wrinkle discrimination coefficient of the surface grayscale image after all punchings before the current punching to obtain a segmentation threshold; If the wrinkle discrimination coefficient of the current stamping surface grayscale image is less than the segmentation threshold, the stamping machine is not adjusted. Otherwise, the stamping machine is controlled and adjusted through the PLC controller.

[0014] In the second aspect, an embodiment of the present application also provides a sheet metal stamping control system using a heat treatment punch, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, wherein when the processor executes the computer program, the steps of a sheet metal stamping control method using a heat treatment punch as described above are implemented.

[0015] This application has at least the following beneficial effects: The present application determines the direction characterization line of any edge contour in the grayscale image of the surface after each stamping according to the main extension direction of the edge contour in the grayscale image of the surface after each stamping; analyzes the difference in direction and length of the direction characterization line of each edge contour and the other edge contours, and determines the morphological similarity of each edge contour in the grayscale image of the surface after each stamping. The beneficial effect is that the morphological similarity between different edge contours is taken into account, and then the possibility that the corresponding edge contour is a wrinkle contour formed by the wrinkling phenomenon caused by stamping is reflected; according to the density of the distribution between different edge contours and the fluctuation of the grayscale value of the pixel points around each edge contour The morphological evaluation value of each edge contour in the grayscale image of the surface after each stamping is determined in combination with the morphological approximation. The beneficial effect is that the distribution of different edge contours and the change of pixel points in the area around the edge contour are taken into account to reflect the possibility that the corresponding edge contour is a wrinkle contour formed by wrinkling of the stamped part due to stamping; the wrinkle cross coefficient of each edge contour in the grayscale image of the surface after each stamping is determined according to the number of the upper endpoints and the intersection points extracted from each edge contour and the discreteness of their distances. The beneficial effect is that the degree of intersection of the edge contours when wrinkling occurs is taken into account, thereby reflecting the edge contour. The wrinkle intersection of the edge contour may exist; the difference in the number of edge contours in the grayscale image of the surface after two adjacent stampings and the difference in the number of edge pixel points on the edge contour at the same position are analyzed to determine the wrinkle change coefficient of each edge contour in the grayscale image of the surface after each stamping; combined with the wrinkle intersection coefficient, the wrinkle interference coefficient of each edge contour in the grayscale image of the surface after each stamping is determined, which has the beneficial effect of considering the change in the number of edge contours in the grayscale image of the surface after two adjacent stampings and the change in the number of pixel points of the same edge contour in the two images, reflecting the possibility of wrinkling of the corresponding edge contour; based on each stamping The wrinkle discrimination coefficient of the surface grayscale image after each stamping is determined based on the morphological evaluation value and the wrinkle interference coefficient of all edge contours in the grayscale image of the surface after stamping, which has the beneficial effect of further reflecting the possibility that the edge contour is a wrinkle edge caused by wrinkling on the surface of the stamped part; based on the wrinkle discrimination coefficient of the surface grayscale image after all stampings before the current stamping, the stamping machine in the stamping process is controlled and adjusted, which has the beneficial effect of improving the accuracy of edge contour detection formed on the surface of the stamped part due to wrinkling, thereby improving the precise control of the stamping machine by the stamping control system, which can improve the production quality and production efficiency of stamped parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] A plate stamping control method using a heat-treated punch of the present application is further described in detail below in conjunction with the accompanying drawings.

[0017] Figure 1 A flow chart of the steps of a plate stamping control method using a heat-treated punch provided in an embodiment of the present application; Figure 2 A flowchart of the steps of a method for obtaining the morphological similarity of each edge contour in a surface grayscale image after each stamping provided in an embodiment of the present application; Figure 3 A flowchart of the steps of a method for obtaining the wrinkle cross coefficient of each edge contour in a surface grayscale image after each stamping provided in an embodiment of the present application. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the following is a further detailed description of a plate stamping control method and system using a heat-treated punch proposed in the present application in conjunction with the accompanying drawings and implementation examples. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0019] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0020] See also Figure 1 , which shows a flow chart of a plate stamping control method using a heat-treated punch provided by an embodiment of the present application, the method comprising the following steps: Step 1: collect the surface grayscale image of the stamped part after each stamping in the sheet metal stamping process, and extract each edge contour in the surface grayscale image after each stamping.

[0021] A CMOS high-definition industrial camera is placed above the workbench of the stamping equipment. After each stamping is completed, the surface image of the stamped part is collected, and the collected image is grayed to obtain the surface gray image of each stamping. The surface gray image is then subjected to edge detection processing, and each edge contour in the surface gray image is extracted through the erosion and dilation algorithm.

[0022] Preferably, in this embodiment, the Canny edge detection algorithm is used for edge detection, wherein the Canny edge detection algorithm and the erosion and expansion algorithm are well-known technologies and are not described in detail here. As other implementation methods, the implementer may adopt other methods of the prior art, such as the Sobel operator, etc. This embodiment does not impose any special restrictions on this.

[0023] At this point, each edge contour in the grayscale image of the surface after each punching is obtained.

[0024] Step 2, according to the main extension direction of any edge contour in the surface grayscale image after each stamping, determine the direction characterization line of any edge contour; analyze the difference in direction and length of the direction characterization line of each edge contour and the other edge contours, and determine the morphological similarity of each edge contour in the surface grayscale image after each stamping; according to the density of distribution between different edge contours and the fluctuation of the grayscale values ​​of the pixels around each edge contour, combined with the morphological similarity, determine the morphological evaluation value of each edge contour in the surface grayscale image after each stamping.

[0025] During the stamping process, the sheet undergoes physical deformation and becomes a stamped part with a specific shape and function. Under normal circumstances, when no wrinkling occurs after the sheet is stamped, the texture formed on the surface of the stamped part is mainly affected by the mold setting, causing the sheet to bend during stamping, thereby forming texture in the surface grayscale image of the stamped part. Such texture formed on the surface of the stamped part is usually wider and longer in overall length, and the direction of the edge contour corresponding to such texture in the surface grayscale image is inconsistent, and there is no obvious regularity. When wrinkling occurs after the sheet is stamped, wrinkles will appear in local areas of the surface of the stamped part, which appear as edge contours with similar morphology in the collected surface grayscale image, and these edge contours are usually along the same direction with obvious regular characteristics.

[0026] Based on the above analysis, the position coordinates of the edge pixels on each edge contour are analyzed to determine the direction characterization line of each edge contour to reflect the overall extension direction of the corresponding edge contour, specifically: The connecting line between the edge pixel point corresponding to the minimum horizontal coordinate and the edge pixel point corresponding to the maximum horizontal coordinate on each edge contour in the surface grayscale image after each punching is recorded as a horizontal connecting line; The connecting line between the edge pixel point corresponding to the minimum ordinate and the edge pixel point corresponding to the maximum ordinate on each edge contour in the surface grayscale image after each punching is recorded as the longitudinal connecting line; Counting the number of all pixels on the horizontal line, and recording it as the horizontal length; counting the number of all pixels on the vertical line, and recording it as the vertical length; If the horizontal length is greater than or equal to the longitudinal length, the horizontal connection line is used as the direction characterizing line of each edge contour in the surface grayscale image after each punching; if the horizontal length is less than the longitudinal length, the longitudinal connection line is used as the direction characterizing line of each edge contour in the surface grayscale image after each punching; Furthermore, the flowchart of the method for obtaining the morphological similarity of each edge contour in the surface grayscale image after each stamping provided by this embodiment is as follows: Figure 2 shown.

[0027] First, based on the differences in the corresponding slopes of the direction characterization lines of different edge profiles and the differences in the lengths of the direction characterization lines, the morphological similarity is determined to reflect the similarity of the extension directions between the different edge profiles, and further reflect the possibility that the edge profile is a wrinkle profile caused by wrinkling during stamping, specifically: Obtaining the slope of any direction characterizing line of the edge contour in the surface grayscale image after each punching, and the number of all pixel points on the direction characterizing line; The difference in the slope between any one edge contour and the other edge contours in the surface grayscale image after each punching is recorded as a first difference; Preferably, in this embodiment, the difference in slope between any one edge contour and the remaining edge contours in the surface grayscale image after each punching is recorded as the first difference.

[0028] taking the average of the first difference between any one edge contour and all other edge contours in the surface grayscale image after each punching as the direction difference coefficient of any one edge contour; The difference in the number between any one edge contour and the remaining edge contours in the surface grayscale image after each punching is recorded as a second difference; Preferably, in this embodiment, the difference in number between any one edge contour and the remaining edge contours in the surface grayscale image after each punching is recorded as the second difference.

[0029] taking the average of the second difference between any one edge contour and all other edge contours in the surface grayscale image after each punching as the length difference coefficient of any one edge contour; The reciprocal of the sum of the direction difference coefficient and the length difference coefficient is used as the morphological approximation of each edge contour in the surface grayscale image after each punching; Preferably, in this embodiment, the morphological similarity of each edge contour in the surface grayscale image after each punching is calculated as follows: ,in, For the The grayscale image of the surface after the first punching The morphological similarity of the strip edge contour, For the The grayscale image of the surface after the first punching The directional difference coefficient of the edge profile of the strip, For the The grayscale image of the surface after the first punching The length difference coefficient of the edge profile of the strip, To preset a value greater than 0 to avoid the denominator being 0, the value range is , in this embodiment, The value is 0.1. As other implementation methods, the implementer can set it according to the actual situation.

[0030] It should be noted that, the smaller the directional difference coefficient is, the more consistent the direction of the corresponding edge contour is with the other edge contours, the smaller the length difference coefficient is, the closer the length of the corresponding edge contour is with the other edge contours, and the greater the obtained morphological similarity is, the more similar the morphology of the corresponding edge contour is with the other edge contours, reflecting the greater possibility that the corresponding edge is a wrinkle contour formed by wrinkling caused by stamping.

[0031] Furthermore, as the punching force continues to increase during the stamping process, axial stress is generated during the movement of the sheet driven by the punch. The axial stress will produce axial strain and radial strain, causing deformation of this part of the sheet. When wrinkling occurs, the wrinkles will be mainly concentrated at the punch position of the mold, and the corresponding edge contour will appear in the surface grayscale image. The local distribution of dense features, and because the wrinkled area will increase the undulation of the stamped part surface, the grayscale changes of the pixels in the corresponding area of ​​the wrinkled area in the image will fluctuate greatly.

[0032] Based on the above analysis, based on the density of different edge contour distributions and the grayscale changes of pixels around the edge contours, the density fluctuation coefficient is determined, specifically: The average of the distances between the centroid of each edge contour and the centroids of all other edge contours in the surface grayscale image after each punching is taken as the distribution coefficient of each edge contour; Preferably, in this embodiment, the mean of the Euclidean distances between the centroid of each edge contour and the centroids of all other edge contours in the surface grayscale image after each stamping is used as the distribution coefficient of each edge contour, wherein the calculation of the Euclidean distance is a well-known technology and will not be described in detail here. As other implementation methods, the implementer may adopt other methods of the prior art, such as Manhattan distance, etc., and this embodiment does not impose any special restrictions on this.

[0033] Calculate the discrete degree of the grayscale values ​​of all pixels within the minimum circumscribed rectangle of each edge contour in the surface grayscale image after each punching; Preferably, in this embodiment, the variance of the grayscale values ​​of all pixels within the minimum circumscribed rectangle of each edge contour in the surface grayscale image after each stamping is calculated. As other implementation methods, the implementer may adopt other methods of the prior art to measure the degree of discreteness, such as standard deviation, coefficient of variation, etc. This embodiment does not impose any special restrictions on this.

[0034] The ratio of the discrete degree to the distribution coefficient is used as the intensive fluctuation coefficient of each edge contour in the surface grayscale image after each punching; Preferably, in this embodiment, the calculation method of the dense fluctuation coefficient of each edge contour in the surface grayscale image after each punching is: ,in, For the The grayscale image of the surface after the first punching The intensive fluctuation coefficient of the strip edge profile, For the The grayscale image of the surface after the first punching The discreteness of the edge contour of the strip, For the The grayscale image of the surface after the first punching The distribution coefficient of the strip edge profile, To preset a value greater than 0, in order to avoid the denominator being 0, The value range is , in this embodiment, The value is 0.1. As other implementation methods, the implementer can set it according to the actual situation.

[0035] It should be noted that, if the distribution coefficient is smaller, it means that the distance between the corresponding edge contour and the other edge contours is closer, which means that the edge contour distribution is denser; the greater the degree of discreteness, the more drastic the fluctuation of the grayscale value of the pixel points in the surrounding area of ​​the corresponding edge contour; the larger the obtained intensive fluctuation coefficient, the more likely the corresponding edge contour is to be a wrinkle contour caused by wrinkling due to deformation of the stamping part during the stamping process.

[0036] Further, based on the morphology similarity and the intensive fluctuation coefficient, a morphology evaluation value is determined, specifically: The product of the morphological similarity and the intensive fluctuation coefficient is used as the morphological evaluation value of each edge contour in the surface grayscale image after each punching; It should be noted that, the larger the morphological evaluation value is, the more likely the corresponding edge profile is a wrinkle profile formed by wrinkling of the stamped part due to stamping.

[0037] At this point, the morphological evaluation value of each edge contour in the surface grayscale image after each punching is obtained.

[0038] Step 3, according to the discreteness of the distance between the endpoint and the intersection point on the skeleton extracted from each edge contour, and the number of the endpoints and the intersection points, determine the wrinkle cross coefficient of each edge contour in the surface grayscale image after each stamping; analyze the difference in the number of edge contours in the surface grayscale image after two adjacent stampings, and the difference in the number of edge pixels on the edge contours at the same position, determine the wrinkle variation coefficient of each edge contour in the surface grayscale image after each stamping, and determine the wrinkle interference coefficient of each edge contour in the surface grayscale image after each stamping in combination with the wrinkle cross coefficient.

[0039] Furthermore, due to the different shapes of sheet metal molds, the sheets may be stamped into different shapes due to actual production needs. Therefore, a large edge contour may be formed on the surface of the stamped part. This large edge contour may intersect with edge contours formed by other stamping processes, that is, the edge contour crossing phenomenon occurs. When wrinkling occurs, the wrinkle contour may also appear in the large edge contour and intersect with the large edge contour. Since this large edge contour is usually longer and thicker, when the wrinkle contour intersects with it, the large edge contour becomes bifurcated. The wrinkle contour and the large edge contour may be identified as one edge contour through the edge detection method, and it is impossible to distinguish them based on the characteristics of the wrinkle contour in the image, resulting in a smaller morphological evaluation value calculated above, and then deviations in the detection of the wrinkle contour occur.

[0040] When there is a large edge profile on the surface of a stamped part, the bifurcation phenomenon in the large edge profile is usually mild, which is manifested as fewer branches on the edge and a greater difference in the lengths of the branches. However, when wrinkling occurs, the intersection of the wrinkled edge and the large edge profile will generate a large number of branches on the large edge profile, and because the wrinkled edges are highly similar, the lengths of the branches generated on the large edge profile are similar.

[0041] Further, the flowchart of the method for obtaining the wrinkle cross coefficient of each edge contour in the surface grayscale image after each punching provided by this embodiment is as follows: Figure 3 shown.

[0042] Based on the above analysis, the intersection of different edge profiles is analyzed and the wrinkle cross coefficient is determined to reflect the degree of intersection of the corresponding edge profiles, specifically: The grayscale values ​​of edge pixels in the surface grayscale image after each punching are assigned to 1, and the grayscale values ​​of non-edge pixels are assigned to 0, so as to obtain a binary image; Using a skeleton extraction algorithm, the skeleton of all edge contours in the binary image is extracted, and the pixel points on the skeleton are recorded as skeleton pixel points; It should be noted that the skeleton extraction algorithm and binarization processing are well-known technologies and will not be described in detail here.

[0043] If there is only one skeleton pixel point in the eight neighborhoods of any skeleton pixel point on the skeleton corresponding to each edge contour, the said any skeleton pixel point is recorded as a skeleton endpoint; if there are more than two skeleton pixels points in the eight neighborhoods of any skeleton pixel point on the skeleton corresponding to each edge contour, the said any skeleton pixel point is recorded as a skeleton intersection point; Count the number of all skeleton endpoints and skeleton intersections on the skeleton corresponding to each edge contour, and record it as the number of bifurcations; The minimum value of the distance between each skeleton endpoint and all skeleton intersection points on the skeleton corresponding to each edge contour is recorded as the closest distance; Preferably, in this embodiment, the minimum Euclidean distance between each skeleton endpoint and all skeleton intersection points on the skeleton corresponding to each edge contour is recorded as the closest distance. As other implementation methods, implementers can use other methods of the prior art to measure the distance, such as Manhattan distance, etc. This embodiment does not impose any special restrictions on this.

[0044] Calculate the discrete degree of the nearest distances of all skeleton endpoints on the skeleton corresponding to each edge contour, recorded as distance discreteness; Preferably, in this embodiment, the variance of the nearest distances of all skeleton endpoints on the skeleton corresponding to each edge contour is calculated. As other implementation methods, the implementer can adopt other methods of the prior art, such as standard deviation, coefficient of variation, etc. This embodiment does not impose any special restrictions on this.

[0045] The ratio of the number of bifurcations to the distance dispersion is used as the wrinkle cross coefficient of each edge contour in the surface grayscale image after each punching; It should be noted that when calculating the ratio of the number of bifurcations to the distance discreteness, in order to avoid the denominator being 0, a preset value greater than 0 is added to the denominator. In the present embodiment, the preset value greater than 0 is 0.1. As for other implementation modes, the implementer may set it according to the actual situation. Secondly, when an edge contour intersects with an edge contour formed by wrinkling, the bifurcation on the edge contour is more serious. The larger the number of endpoints on the edge contour and the smaller the degree of discreteness, the more consistent the bifurcation lengths of the corresponding edge contours are, and the larger the obtained wrinkling intersection coefficient is, which means that the edge contour is more likely to have wrinkling intersection.

[0046] Furthermore, usually the same batch of stamped parts will use the same mold, and the edges formed by each stamping are relatively similar. When wrinkles appear on the surface of the stamped part, the number of edge contours in the image will increase, and they may intersect with the original edge contours in the image, which increases the number of pixels contained in the detected edge contours. Secondly, the position of the edge contours on the surface of the stamped part is the same after each stamping. When the centroid of each edge contour in the surface grayscale image after each stamping coincides with the centroid of the edge contour in the surface grayscale image after the previous stamping, it means that the two edge contours are the same edge contour.

[0047] Based on the above analysis, the change in the number of edge contours on the grayscale image of the surface after two stampings and the change in the number of pixels on the edge contours are analyzed to determine the wrinkle change coefficient, which is: The difference between the number of all edge contours in the surface grayscale image after each punching and the number of all edge contours in the surface grayscale image after the previous punching is recorded as a first quantity difference; Preferably, in this embodiment, the absolute value of the difference between the number of all edge contours in the surface grayscale image after each punching and the number of all edge contours in the surface grayscale image after the previous punching is recorded as the first quantity difference.

[0048] The centroid coordinates of each edge contour in the surface grayscale image after each punching and the edge contour with the same centroid coordinates in the surface grayscale image after the previous punching are recorded as the relative edge contour of each edge contour; The difference between the number of all edge pixel points on each edge contour in the surface grayscale image after each punching and the number of all edge pixel points on the relative edge contour is recorded as a second quantity difference; Preferably, in this embodiment, the absolute value of the difference between the number of all edge pixels on each edge contour in the surface grayscale image after each punching and the number of all edge pixels on the relative edge contour is recorded as the second quantity difference.

[0049] taking the sum of the first quantity difference and the second quantity difference as the wrinkle variation coefficient of each edge contour in the surface grayscale image after each punching; It should be noted that if a certain edge contour does not have a corresponding edge contour in the surface grayscale image of the previous stamping, the number of all edge pixel points of the corresponding edge contour is 0, that is, the second quantity difference of each edge contour is the number of all edge pixel points on the corresponding edge contour.

[0050] It should be noted that if the difference in the first quantity is larger and the difference in the second quantity is also larger, that is, the wrinkling variation coefficient is larger, it means that the edge contour is more likely to intersect with the wrinkle edge due to the wrinkling phenomenon generated on the surface of the stamping part, resulting in a larger change, reflecting that the corresponding edge contour is more likely to be a wrinkled edge generated by wrinkling on the surface of the stamping part.

[0051] Further, based on the wrinkling cross coefficient and the wrinkling variation coefficient, a wrinkling interference coefficient is determined, specifically: The product of the wrinkle cross coefficient and the wrinkle variation coefficient is used as the wrinkle interference coefficient of each edge contour in the surface grayscale image after each punching; It should be noted that the larger the obtained wrinkling interference coefficient is, the more likely the corresponding edge profile is to be a wrinkled edge due to the intersection of the wrinkled edge generated when the wrinkling phenomenon occurs on the surface of the stamping part.

[0052] At this point, the wrinkling interference coefficient of each edge contour in the surface grayscale image after each punching is obtained.

[0053] Step 4, based on the morphological evaluation values ​​of all edge contours in the surface grayscale image after each stamping and the wrinkle interference coefficient, determine the wrinkle discrimination coefficient of the surface grayscale image after each stamping, and based on the wrinkle discrimination coefficient of the surface grayscale images after all stampings before the current stamping, control and adjust the stamping machine during the stamping process.

[0054] Further, based on the morphology evaluation value and the wrinkling interference coefficient, a discrimination factor is determined, specifically: The product of the morphological evaluation value and the wrinkling interference coefficient is used as a discriminant factor of each edge contour in the surface grayscale image after each punching; It should be noted that if the shape of each edge contour is closer to that of the other edge contours, the distribution is denser and the grayscale changes of the pixels in the surrounding area are larger, or there are more branches in the edge contour, and the difference in the number of edge contours and the number of edge pixels compared with the surface grayscale image of the previous stamping is greater, the obtained discrimination factor is larger, which means that the edge contour is more likely to be a wrinkle edge caused by wrinkling on the surface of the stamped part.

[0055] Furthermore, based on the discriminant factors, the wrinkling phenomenon on the surface of the stamped part is evaluated and the stamping process is controlled, specifically: The average value of the discrimination factors of all edge contours in the surface grayscale image after each punching is used as the wrinkle discrimination coefficient of the surface grayscale image after each punching; Performing threshold segmentation on the wrinkle discrimination coefficient of all the surface grayscale images after stamping before the current stamping to obtain a segmentation threshold; Preferably, in this embodiment, the wrinkle discrimination coefficient of all surface grayscale images after stamping before the current stamping is cross-validated to obtain a segmentation threshold, wherein the cross-validation method is a well-known technology and will not be described in detail here. As other implementation methods, implementers can adopt other methods of the prior art, such as the Otsu threshold segmentation method, etc. This embodiment does not impose any special restrictions on this.

[0056] If the wrinkle discrimination coefficient of the current stamping surface grayscale image is less than the segmentation threshold, the stamping machine in the stamping process is not adjusted; if the wrinkle discrimination coefficient of the current stamping surface grayscale image is greater than or equal to the segmentation threshold, the stamping control system controls and adjusts the stamping machine through a PLC (Programmable Logic Controller); It should be noted that when the wrinkle discrimination coefficient is greater than or equal to the segmentation threshold, the stamping control system outputs a control signal, the PLC controller controls the motor according to the control signal, and the motor adjusts the output power according to the actual control, so that the stamping speed and stamping force of the stamping machine are reduced, thereby reducing the overall stress on the sheet during the stamping process and reducing the possibility of wrinkling.

[0057] Based on the same inventive concept as the above method, an embodiment of the present application also provides a sheet metal stamping control system using a heat treatment punch, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, wherein when the processor executes the computer program, the steps of any one of the above-mentioned sheet metal stamping control methods using a heat treatment punch are implemented.

[0058] It should be understood that although Figure 1 The steps in the flowchart are shown in sequence as indicated by the arrows, but these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified in this document, there is no strict order restriction for the execution of these steps, and these steps can be executed in other orders. Moreover, Figure 1 At least part of the steps may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily executed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be executed in turn or alternately with other steps or at least part of the sub-steps or stages of other steps.

[0059] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0060] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the present application. It should be pointed out that, for those of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present application. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present application without departing from the content of the technical solution of the present application, shall fall within the protection scope of the technical solution of the present application.

Claims

1. A plate stamping control method using a heat-treated punch, characterized in that: The method comprises the following steps: Collect the grayscale image of the stamped part surface after each stamping process in the sheet metal stamping process, and extract each edge contour in the grayscale image of the surface after each stamping process; According to the main extension direction of any edge contour in the surface grayscale image after each stamping, determine the direction characterization line of any edge contour; analyze the difference in direction and length of the direction characterization line of each edge contour and the other edge contours, and determine the morphological similarity of each edge contour in the surface grayscale image after each stamping; according to the density of distribution between different edge contours and the fluctuation of the grayscale value of the pixel points around each edge contour, determine the density fluctuation coefficient of each edge contour in the surface grayscale image after each stamping, and combine the morphological similarity and the density fluctuation coefficient to determine the morphological evaluation value of each edge contour in the surface grayscale image after each stamping; According to the discreteness of the distance between the endpoint and the intersection point on the skeleton extracted from each edge contour, and the number of the endpoint and the intersection point, the wrinkle cross coefficient of each edge contour in the surface grayscale image after each stamping is determined; the difference in the number of edge contours in the surface grayscale image after two adjacent stampings, and the difference in the number of edge pixels on the edge contours at the same position are analyzed to determine the wrinkle variation coefficient of each edge contour in the surface grayscale image after each stamping, and the wrinkle cross coefficient is combined to determine the wrinkle interference coefficient of each edge contour in the surface grayscale image after each stamping; Based on the morphological evaluation values ​​and the wrinkle interference coefficients of all edge contours in the surface grayscale image after each stamping, the wrinkle discrimination coefficient of the surface grayscale image after each stamping is determined; based on the wrinkle discrimination coefficient of the surface grayscale images after all stampings before the current stamping, the stamping machine of the stamping process is controlled and adjusted.

2. A plate stamping control method using a heat-treated punch as claimed in claim 1, characterized in that: The step of determining a direction characterizing line of any edge contour comprises: The line between the edge pixel point with the smallest horizontal coordinate and the edge pixel point with the largest horizontal coordinate on any edge contour is recorded as a horizontal line; The line between the edge pixel point with the smallest ordinate and the edge pixel point with the largest ordinate on any edge contour is recorded as a vertical line; Counting the number of all pixels on the horizontal line, and recording it as the horizontal length; counting the number of all pixels on the vertical line, and recording it as the vertical length; If the horizontal length is greater than or equal to the vertical length, the horizontal connection line is used as the direction characterizing line of any edge contour; otherwise, the vertical connection line is used as the direction characterizing line of any edge contour.

3. A plate stamping control method using a heat-treated punch as claimed in claim 1, characterized in that: Determining the morphological similarity of each edge contour in the surface grayscale image after each punching includes: Obtaining the slope of the direction characterization line of any edge contour and the number of all pixel points on the direction characterization line; The average of the differences in the slopes between any one edge profile and all other edge profiles in the surface grayscale image after each punching is used as the direction difference coefficient of any one edge profile; The average of the differences in the number between any one edge contour and all other edge contours in the surface grayscale image after each punching is used as the length difference coefficient of any one edge contour; The reciprocal of the sum of the direction difference coefficient and the length difference coefficient is used as the morphological approximation of each edge contour in the surface grayscale image after each punching.

4. A plate stamping control method using a heat-treated punch as claimed in claim 1, characterized in that: The step of determining the dense fluctuation coefficient of each edge contour in the surface grayscale image after each punching, and combining the morphological approximation and the dense fluctuation coefficient to determine the morphological evaluation value of each edge contour in the surface grayscale image after each punching comprises: The average of the distances between the centroid of each edge contour and the centroids of all other edge contours in the surface grayscale image after each punching is taken as the distribution coefficient of each edge contour; Calculate the discrete degree of the grayscale values ​​of all pixels within the minimum circumscribed rectangle of each edge contour in the surface grayscale image after each punching; The ratio of the discrete degree to the distribution coefficient is used as the intensive fluctuation coefficient of each edge contour in the surface grayscale image after each punching; The product of the morphological similarity and the dense fluctuation coefficient is used as the morphological evaluation value of each edge contour in the surface grayscale image after each punching.

5. A plate stamping control method using a heat-treated punch as claimed in claim 1, characterized in that: The method of determining the wrinkle cross coefficient of each edge contour in the surface grayscale image after each punching comprises: The grayscale values ​​of edge pixels in the surface grayscale image after each punching are assigned to 1, and the grayscale values ​​of non-edge pixels are assigned to 0, to obtain a binary image, and the skeletons of all edge contours in the binary image are extracted, and the pixels on the skeletons are recorded as skeleton pixels; If there is only one skeleton pixel point in the eight-neighborhood of any skeleton pixel point on the skeleton corresponding to each edge contour, the any skeleton pixel point is recorded as a skeleton endpoint; if there are multiple skeleton pixels in the eight-neighborhood of any skeleton pixel point on the skeleton corresponding to each edge contour, the any skeleton pixel point is recorded as a skeleton intersection point; Count the number of all skeleton endpoints and skeleton intersections on the skeleton corresponding to each edge contour, and record it as the number of bifurcations; The minimum value of the distance between each skeleton endpoint and all skeleton intersection points on the skeleton corresponding to each edge contour is recorded as the closest distance; Calculate the discrete degree of the nearest distances of all skeleton endpoints on the skeleton corresponding to each edge contour, recorded as distance discreteness; The ratio of the number of bifurcations to the distance dispersion is used as the wrinkle cross coefficient of each edge contour in the surface grayscale image after each punching.

6. A plate stamping control method using a heat-treated punch as claimed in claim 1, characterized in that: The method of determining the wrinkle variation coefficient of each edge contour in the surface grayscale image after each punching comprises: The difference between the number of all edge contours in the grayscale image of the surface after each punching and the number of all edge contours in the grayscale image of the surface after the adjacent punching is recorded as a first quantity difference; The centroid coordinates of each edge contour in the grayscale image of the surface after each punching and the edge contour with the same centroid coordinates in the grayscale image of the surface after the adjacent punching are recorded as the relative edge contour of each edge contour; Recording the difference between the number of all edge pixels on each edge contour and the number of all edge pixels on the relative edge contour as a second quantity difference; The sum of the first quantity difference and the second quantity difference is used as the wrinkle variation coefficient of each edge contour in the surface grayscale image after each punching.

7. A plate stamping control method using a heat-treated punch as claimed in claim 1, characterized in that: The wrinkle interference coefficient of each edge contour in the surface grayscale image after each punching is the product of the wrinkle cross coefficient and the wrinkle variation coefficient.

8. A plate stamping control method using a heat-treated punch as claimed in claim 1, characterized in that: Determining the wrinkle discrimination coefficient of the surface grayscale image after each punching includes: The product of the morphological evaluation value and the wrinkling interference coefficient is used as a discriminant factor of each edge contour in the surface grayscale image after each punching; The average value of the discrimination factors of all edge contours in the surface grayscale image after each punching is used as the wrinkle discrimination coefficient of the surface grayscale image after each punching.

9. A plate stamping control method using a heat-treated punch as claimed in claim 1, characterized in that: The control and adjustment of the punching machine in the punching process includes: Performing threshold segmentation on the wrinkle discrimination coefficient of the surface grayscale image after all punchings before the current punching to obtain a segmentation threshold; If the wrinkle discrimination coefficient of the current stamping surface grayscale image is less than the segmentation threshold, the stamping machine is not adjusted. Otherwise, the stamping machine is controlled and adjusted through the PLC controller.

10. A sheet metal stamping control system using a heat-treated punch, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that: When the processor executes the computer program, the steps of a sheet metal stamping control method using a heat-treated punch as described in any one of claims 1 to 9 are implemented.

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