An adaptive glue coating defect detection and PLC closed-loop control method

Abstract

The present application relates to the technical field of gluing, in particular to a self-adaptive gluing defect detection and PLC closed-loop control method, which adopts partition self-adaptive threshold detection, can automatically adapt to light changes, workpiece reflection, and glue line color difference fluctuations, does not need frequent manual parameter calibration, and has strong environmental adaptability; combined with segmented detection and multi-frame fault-tolerant verification mechanism, effectively filters field interference, greatly reduces the missed detection rate and the false detection rate, and significantly improves the detection stability; realizes glue width quantitative detection and PLC closed-loop automatic glue adjustment, solves the problem of poor consistency of traditional process gluing, and improves the product yield; the whole scheme relies on general industrial PLC, does not need high-end visual controller, has low modification cost, strong universality, and is easy to industrialize and popularize.

Description

Technical Field

[0001] This invention relates to the field of adhesive coating technology, and in particular to an adaptive adhesive coating defect detection and PLC closed-loop control method. Background Technology

[0002] Existing industrial adhesive coating production lines generally use fixed grayscale thresholds to identify adhesive lines, which have simple detection logic and poor adaptability. Interference factors in the production environment, such as light fluctuations, workpiece surface reflections, differences in adhesive color, and vibrations of conveyor machinery, can easily cause missed or false detections, resulting in defective products being shipped out or frequent erroneous rejections, thus affecting production efficiency.

[0003] Traditional testing equipment only outputs simple OK / NG switching signals, failing to achieve quantitative detection of adhesive width and real-time process correction. Adhesive coating consistency relies on frequent manual parameter calibration, resulting in low levels of automation, high production costs, and poor product stability. Currently, there is a lack of adhesive coating detection technology that can adapt to changing operating conditions, possess fault tolerance and anti-interference capabilities, and can be linked with a PLC for closed-loop process adjustment. Therefore, its shortcomings are significant, and a solution is urgently needed. Summary of the Invention

[0004] To address the aforementioned technical problems, the present invention aims to provide an adaptive glue coating defect detection and PLC closed-loop control method.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: An adaptive glue coating defect detection and PLC closed-loop control method is disclosed, based on the application of a glue coating production line. The glue coating production line includes a PLC controller, a human-machine interface terminal, a conveyor line for transporting workpieces, and, sequentially arranged along the conveyor line's transport direction, an incoming material sensor, a glue gun, a glue line detection sensor, and a defective product rejection mechanism. The specific method steps include: A. The conveyor line transports the workpieces; B. After the incoming material sensor identifies the workpiece being conveyed by the conveyor line, it sends a signal back to the glue gun. C. Apply glue to the workpiece using a glue gun to form glue lines on the workpiece; D. The glue line detection sensor continuously acquires grayscale images of the glue lines on the workpieces conveyed by the conveyor line. The single frame image is divided into multiple independent detection zones along the workpiece movement direction. Each detection zone is preprocessed with segmented mean filtering to remove image noise interference. E. The PLC controller collects the average grayscale value of the background of each detection zone in real time, and combines it with the preset glue line grayscale benchmark to dynamically generate an independent adaptive grayscale detection threshold for each detection zone. F. Based on the adaptive threshold, divide the glue line pixels and background pixels, extract the upper and lower edge coordinates of the glue line, and calculate the real-time glue width value and the continuous effective length of the glue line for each partition. G. Based on the preset upper and lower limits of glue width and the threshold of continuous glue application length, make preliminary judgments on glue width exceeding the standard and glue breakage / short glue defects respectively. H. Through continuous multi-frame image comparison and fault tolerance verification, the glue coating defect is finally confirmed only when the same defect is detected synchronously in multiple frames, thus filtering out single-frame misjudgment interference. I. The detection data is transmitted to the PLC controller. For qualified workpieces, the glue dispensing amount is finely adjusted in a closed loop by the glue application servo. For defective workpieces, the defective product rejection mechanism performs precise delay automatic rejection, realizing integrated closed-loop control of detection, glue application, and sorting.

[0006] Furthermore, in step E, the partitioned adaptive grayscale detection threshold is automatically and dynamically adjusted according to the ambient light intensity and the reflectivity of the workpiece.

[0007] Furthermore, in step H, a cross-validation mechanism of at least three consecutive images is employed to achieve interference-resistant and fault-tolerant detection.

[0008] Furthermore, in step I, the PLC controller combines the real-time conveyor line speed to complete the delayed positioning of defective workpieces, achieving precise rejection. At the same time, it dynamically corrects the glue application servo parameters according to the glue width deviation, achieving closed-loop stable control of the glue width.

[0009] Furthermore, the adhesive line detection sensor is a PJC-800 sensor.

[0010] Furthermore, the defective product rejection mechanism includes a mounting frame located on one side of the conveyor line, a cylinder mounted on the mounting frame, and a rejection head mounted on the piston rod of the cylinder.

[0011] Furthermore, the mounting bracket includes a fixed crossbar, a sliding sleeve slidably connected to the fixed crossbar laterally, a first locking fastener for locking the sliding sleeve to the fixed crossbar, an adjusting rod slidably connected to the sliding sleeve longitudinally, a second locking fastener for locking the adjusting rod to the sliding sleeve, a vertical adjusting rod slidably connected to the adjusting rod vertically, and a third locking fastener for locking the vertical adjusting rod to the adjusting rod. A cylinder is mounted on the vertical adjusting rod.

[0012] The beneficial effects of this invention are as follows: This invention adopts a partitioned adaptive threshold detection method, which can automatically adapt to changes in lighting, workpiece reflection, and fluctuations in adhesive line color difference, eliminating the need for frequent manual parameter calibration and exhibiting strong environmental adaptability. Combined with segmented detection and a multi-frame fault-tolerant verification mechanism, it effectively filters on-site interference, significantly reducing the missed detection rate and false detection rate, and significantly improving detection stability. It achieves quantitative detection of adhesive width and PLC closed-loop automatic adhesive adjustment, solving the problem of poor adhesive coating consistency in traditional processes and improving product yield. The entire solution relies on a general-purpose industrial PLC, eliminating the need for a high-end vision controller, resulting in low modification costs, strong versatility, and ease of industrialization and promotion. Attached Figure Description

[0013] Figure 1 This is a three-dimensional structural diagram of the glue coating production line of the present invention, showing the hidden PLC controller and human-machine interface terminal.

[0014] Figure 2 This is a three-dimensional structural diagram of the defective product rejection mechanism of the present invention.

[0015] Explanation of reference numerals in the attached figures: 1. Conveyor line; 2. Incoming material sensor; 3. Glue gun; 4. Glue line detection sensor; 5. Defective product rejection mechanism; 6. Mounting bracket; 7. Cylinder; 8. Rejection head; 9. Fixed crossbar; 10. Sliding sleeve; 11. First locking fastener; 12. Adjusting longitudinal rod; 13. Second locking fastener; 14. Vertical adjusting rod; 15. Third locking fastener. Detailed Implementation To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to embodiments and accompanying drawings. The content mentioned in the embodiments is not intended to limit the present invention.

[0016] like Figure 1 and Figure 2 As shown, the present invention provides an adaptive glue coating defect detection and PLC closed-loop control method, which is based on the application of a glue coating production line. The glue coating production line includes a PLC controller, a human-machine interface terminal, a conveyor line 1 for conveying workpieces, and a material receiving sensor 2, a glue gun 3, a glue line detection sensor 4, and a defective product rejection mechanism 5 arranged sequentially along the conveying direction of the conveyor line 1. The specific method steps include: A. Conveyor line 1 transports the workpieces; B. After the incoming material sensor 2 detects the workpiece being conveyed by the conveyor line 1, it sends a signal back to the glue gun 3. C. Apply glue to the workpiece using glue gun 3 to form glue lines on the workpiece; D. The glue line detection sensor 4 continuously acquires grayscale images of the glue lines on the workpieces conveyed by the conveyor line 1. The PLC controller divides a single frame image into multiple independent detection zones along the workpiece movement direction, and performs segmented mean filtering and noise reduction preprocessing on each detection zone to eliminate discrete noise caused by jitter and light source flicker, thereby removing image noise interference and retaining clear glue line edge features. Preferably, the PLC controller evenly divides each frame image into 8 to 12 detection zones along the workpiece movement direction. E. The PLC controller collects the average grayscale value of the background of each detection zone in real time, and dynamically generates an independent adaptive grayscale detection threshold for each detection zone by combining it with the preset grayscale benchmark of the adhesive line. The recognition threshold is automatically adjusted up or down according to the brightness and reflectivity of the scene, so as to realize adaptive recognition in different areas and different working conditions, replacing the traditional global fixed threshold. When the ambient brightness decreases, the grayscale detection threshold is automatically lowered, and when the workpiece reflectivity is strong, the grayscale detection threshold is automatically raised to ensure the stability of the grayscale detection of the adhesive line. F. Based on the adaptive threshold segmentation of adhesive line pixels and background pixels, extract the upper and lower edge coordinates of the adhesive line, calculate the real-time adhesive width value and the continuous effective length of the adhesive line in each partition, and realize the quantitative detection of adhesive width. G. Based on the preset upper and lower limits of glue width and the threshold of continuous glue application length, perform preliminary judgment on glue width exceeding the standard and glue breakage / short glue defects respectively; perform two-level judgment on the data of each zone: exceeding the glue width range is judged as a size exceeding the standard defect (glue width too wide or too narrow exceeding the standard defect), and continuous glue-free areas exceeding the set length are judged as glue breakage / short glue defects; compare the detection data of each zone one by one, and mark the preliminary defect location and defect type; H. To avoid misjudgment caused by instantaneous interference on site, a fault tolerance check is performed by comparing multiple consecutive frames of images. Only when multiple frames of images simultaneously detect the same defect in the same location is the glue coating defect finally confirmed, filtering out single-frame misjudgment interference and greatly reducing the probability of false detection and false rejection. 1. The detection data is transmitted to the PLC controller. For qualified workpieces, the glue application servo speed and glue dispensing amount are finely adjusted in a closed loop. For defective workpieces, the defective product rejection mechanism 5 performs precise delay automatic rejection, realizing integrated closed-loop control of detection, glue adjustment, and sorting. Specifically, for qualified workpieces, the PLC controller dynamically adjusts the glue application servo speed and glue dispensing amount based on the deviation between the real-time glue width and the standard glue width, realizing closed-loop glue width correction. For defective workpieces, the delay is precisely calculated based on the speed of conveyor line 1. After the defective product arrives at the rejection station, the defective product rejection mechanism 5 is triggered to automatically reject it, and the defect data is stored to complete production traceability.

[0017] In this embodiment, the partitioned adaptive grayscale detection threshold in step E is automatically and dynamically adjusted according to the ambient light intensity and the reflectivity of the workpiece, replacing the fixed global threshold and adapting to the complex working conditions of the production line.

[0018] In this embodiment, a cross-verification mechanism of at least three consecutive images is used in step H to achieve interference-resistant and fault-tolerant detection, reducing the false detection and rejection rate of the production line. Specifically, three consecutively acquired images are cross-compared, and if only two or more images simultaneously determine the defect at the same location, the workpiece is confirmed to be defective, effectively filtering out occasional interference signals.

[0019] In this embodiment, in step I, the PLC controller, combined with the real-time speed of conveyor line 1, completes the delayed positioning of defective workpieces to achieve precise rejection. Simultaneously, it dynamically corrects the glue application servo parameters based on the glue width deviation, achieving closed-loop stable control of the glue width. Specifically, for qualified workpieces, the glue application servo parameters are automatically fine-tuned based on the glue width deviation, correcting the glue application accuracy in real time. For defective workpieces, speed measurement and delayed positioning precisely trigger the rejection station action, achieving automatic sorting of defective products. At the same time, the defect type, quantity, and glue width data are uploaded and saved, enabling traceability of production data.

[0020] This application eliminates the need for repeated manual calibration of testing parameters, boasts strong anti-interference capabilities, high testing accuracy, and a high degree of automation, and can be stably adapted to high-speed mass production lines.

[0021] In this embodiment, the adhesive line detection sensor 4 is a PJC-800 sensor.

[0022] In this embodiment, the defective product rejection mechanism 5 includes a mounting frame 6 disposed on one side of the conveyor line 1, a cylinder 7 mounted on the mounting frame 6, and a rejection head 8 mounted on the piston rod of the cylinder 7. In practical applications, for defective workpieces, the delay is accurately calculated based on the speed of the conveyor line 1. After the defective product arrives at the rejection station, the cylinder 7 is triggered to automatically reject it. The piston rod of the cylinder 7 drives the rejection head 8 to extend, causing the rejection head 8 to push the defective workpiece laterally, thereby removing the defective workpiece from the conveyor line 1, thus achieving the rejection of the defective workpiece. At the same time, defect data is stored to complete production traceability.

[0023] In this embodiment, the mounting bracket 6 includes a fixed crossbar 9, a sliding sleeve 10 slidably connected to the fixed crossbar 9, a first locking fastener 11 for locking the sliding sleeve 10 to the fixed crossbar 9, an adjusting rod 12 slidably connected to the sliding sleeve 10, a second locking fastener 13 for locking the adjusting rod 12 to the sliding sleeve 10, a vertical adjusting rod 14 slidably connected to the adjusting rod 12, and a third locking fastener 15 for locking the vertical adjusting rod 14 to the adjusting rod 12. The cylinder 7 is mounted on the vertical adjusting rod 14. Specifically, the first locking fastener 11, the second locking fastener 13, and the third locking fastener 15 can all be locking bolts. This structural design facilitates the adjustment of the height, lateral position, and longitudinal position of the cylinder 7 to ensure that non-standard workpieces can be rejected.

[0024] This invention employs a zoned adaptive threshold detection system, which can automatically adapt to changes in lighting, workpiece reflection, and fluctuations in adhesive line color difference, eliminating the need for frequent manual parameter calibration and demonstrating strong environmental adaptability. Combined with segmented detection and a multi-frame fault-tolerant verification mechanism, it effectively filters out on-site interference, significantly reducing the missed detection rate and false detection rate, and substantially improving detection stability. It achieves quantitative detection of adhesive width and PLC closed-loop automatic adhesive adjustment, solving the problem of poor adhesive application consistency in traditional processes and improving product yield. The entire solution relies on a general-purpose industrial PLC, eliminating the need for a high-end vision controller, resulting in low modification costs, strong versatility, and ease of industrialization.

[0025] The above embodiments are preferred implementations of the present invention. In addition, the present invention can be implemented in other ways. Any obvious substitutions without departing from the concept of the present technical solution are within the protection scope of the present invention.

Claims

1. An adaptive glue coating defect detection and PLC closed-loop control method, characterized in that: Based on the application of the glue coating production line, the glue coating production line includes a PLC controller, a human-machine interface terminal, a conveyor line (1) for conveying workpieces, and a material receiving sensor (2), a glue gun (3), a glue line detection sensor (4), and a defective product rejection mechanism (5) arranged sequentially along the conveying direction of the conveyor line (1). The specific method steps include: A. Conveyor line (1) transports the workpiece; B. After the incoming material sensor (2) identifies the workpiece being conveyed by the conveyor line (1), it sends a signal back to the glue gun (3). C. Apply glue to the workpiece using a glue gun (3) to form glue lines on the workpiece; D. The glue line detection sensor (4) continuously collects grayscale images of the glue line on the workpiece conveyed by the conveyor line (1), divides the single frame image into multiple independent detection zones along the workpiece movement direction, performs segmented mean filtering and noise reduction preprocessing on each detection zone, and removes image noise interference. E. The PLC controller collects the average grayscale value of the background of each detection zone in real time, and combines it with the preset glue line grayscale benchmark to dynamically generate an independent adaptive grayscale detection threshold for each detection zone. F. Based on the adaptive threshold, divide the glue line pixels and background pixels, extract the upper and lower edge coordinates of the glue line, and calculate the real-time glue width value and the continuous effective length of the glue line for each partition. G. Based on the preset upper and lower limits of glue width and the threshold of continuous glue application length, make preliminary judgments on glue width exceeding the standard and glue breakage / short glue defects respectively. H. Through continuous multi-frame image comparison and fault tolerance verification, the glue coating defect is finally confirmed only when the same defect is detected synchronously in multiple frames, thus filtering out single-frame misjudgment interference. I. The detection data is transmitted to the PLC controller. For qualified workpieces, the glue dispensing amount is finely adjusted in a closed loop. For defective workpieces, the defective product rejection mechanism (5) performs precise delayed automatic rejection, realizing integrated closed-loop control of detection, glue adjustment and sorting.

2. The adaptive glue coating defect detection and PLC closed-loop control method according to claim 1, characterized in that: In step E, the adaptive grayscale detection threshold for the partition is automatically and dynamically adjusted based on the ambient light intensity and the reflectivity of the workpiece.

3. The adaptive glue coating defect detection and PLC closed-loop control method according to claim 1, characterized in that: In step H, a cross-validation mechanism of at least three consecutive images is used to achieve interference-resistant and fault-tolerant detection.

4. The adaptive glue coating defect detection and PLC closed-loop control method according to claim 1, characterized in that: In step I, the PLC controller, in conjunction with the real-time conveyor line (1) speed, completes the delayed positioning of defective workpieces to achieve precise rejection. At the same time, it dynamically corrects the glue application servo parameters according to the glue width deviation to achieve closed-loop stable control of glue width.

5. The adaptive glue coating defect detection and PLC closed-loop control method according to claim 1, characterized in that: The adhesive line detection sensor (4) is a PJC-800 sensor.

6. The adaptive glue coating defect detection and PLC closed-loop control method according to claim 1, characterized in that: The defective product rejection mechanism (5) includes a mounting frame (6) set on one side of the conveyor line (1), a cylinder (7) mounted on the mounting frame (6), and a rejection head (8) mounted on the piston rod of the cylinder (7).

7. The adaptive glue coating defect detection and PLC closed-loop control method according to claim 6, characterized in that: The mounting bracket (6) includes a fixed crossbar (9), a sliding sleeve (10) slidably connected to the fixed crossbar (9), a first locking fastener (11) for locking the sliding sleeve (10) to the fixed crossbar (9), an adjusting rod (12) slidably connected to the sliding sleeve (10), a second locking fastener (13) for locking the adjusting rod (12) to the sliding sleeve (10), a vertical adjusting rod (14) slidably connected to the adjusting rod (12), and a third locking fastener (15) for locking the vertical adjusting rod (14) to the adjusting rod (12). A cylinder (7) is mounted on the vertical adjusting rod (14).

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