Method for detecting and controlling positional accuracy in curved-surface, multi-degree-of-freedom array inkjet forming
By using flexible materials and image processing methods of a vision inspection system in a curved surface multi-degree-of-freedom array inkjet forming device, the problem of positional accuracy deviation in the printing of curved electronic components has been solved, and efficient and high-precision curved electronic printing has been achieved.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- NANJING UNIV OF AERONAUTICS & ASTRONAUTICS
- Filing Date
- 2025-12-22
- Publication Date
- 2026-07-02
AI Technical Summary
Existing multi-degree-of-freedom array inkjet forming devices for curved surfaces suffer from significant deviations between the actual forming position and the target position due to the coupling effects of various factors during operation, making it difficult to achieve high-precision printing of curved electronic components. Furthermore, conventional testing methods are costly and ineffective.
A flexible material is bonded to the printing substrate. Images are picked up by a vision inspection system and digital image processing is performed to mark the positions of key points. Combined with pixel matching and key point accuracy calculation, a new input image is generated. A threshold is set and iterated until the accuracy requirements are met, thus achieving closed-loop control of position accuracy.
It effectively achieves closed-loop control of the positional accuracy of multi-degree-of-freedom inkjet forming on curved surfaces, reduces costs, improves printing accuracy and consistency, and adapts to the challenges of multi-factor coupling relationships.
Smart Images
Figure CN2025144292_02072026_PF_FP_ABST
Abstract
Description
Method for Position Accuracy Detection and Control of Multi-DOF Array Inkjet Printing on Curved Surfaces Technical Field
[0001] This invention belongs to the field of curved electronic component printing, specifically relating to a method for detecting and controlling the positional accuracy of ink droplets forming on the substrate surface during the multi-degree-of-freedom array inkjet forming process of curved electronic devices. Background Technology
[0002] With the explosive growth of industries such as electronics and communications, and aerospace, computer-aided design and manufacturing of electronic components such as chips, advanced circuits, and conformal antennas has become a research hotspot. Compared to the relatively mature 2D planar additive manufacturing, model-driven manufacturing on curved surfaces requires researchers to systematically establish three modules: model processing, motion control, and equipment design and manufacturing. Currently, simple curved surface multi-axis direct-write equipment offers solutions for manufacturing curved electronic components, but its production efficiency and accuracy need improvement, making it difficult to meet the requirements of large-scale industrial production, resulting in high mass production costs. Traditional 2D printing, due to limitations in its actuators and control methods, struggles to print high-precision conformal electronic components that meet the required specifications.
[0003] In the multi-degree-of-freedom array inkjet printing system for curved surfaces discussed in this paper, an array printhead mounted at the end of a multi-axis motion mechanism is used to achieve electronic printing tasks on curved surfaces of a certain width. Theoretically, this can achieve efficient and high-precision electronic printing on spatial curved surfaces with certain curvature limitations. However, currently, there are the following shortcomings in realizing multi-degree-of-freedom array inkjet forming of curved electronic components:
[0004] (1) During the operation of the curved surface multi-degree-of-freedom array inkjet forming device, due to changes in feed rate, motion posture, clamping error, coordinate calibration error, jetting distance and ink pressure, the actual forming position deviates significantly from the target position, resulting in low position accuracy and difficulty in ensuring consistency between the input and output patterns.
[0005] (2) When the curved multi-degree-of-freedom array inkjet forming device is in operation, the camera is clamped by a robotic arm to take pictures of the shallow circuit pattern on the curved surface. Factors such as angle changes, robot vibration and small printing spacing make it difficult for the camera to capture high-precision images.
[0006] (3) When the multi-degree-of-freedom array inkjet forming device is in operation, it is difficult to capture small height changes of the curved surface and the cost is high when using a three-dimensional scanner to scan and reconstruct the shallow circuit pattern of the curved surface.
[0007] How to coordinate with an image-input-based multi-degree-of-freedom array inkjet forming device to achieve closed-loop control of the positional accuracy of multi-degree-of-freedom inkjet forming on curved surfaces of a certain width, under the influence of factors such as actual cost, detection effect and application scenarios, is an important problem that urgently needs to be solved to achieve efficient and high-precision electronic printing of curved surfaces. It has profound significance for realizing the integrated forming of curved electronic components. Summary of the Invention
[0008] To address the aforementioned problems, this invention discloses a method for detecting and controlling the positional accuracy of multi-degree-of-freedom array inkjet printing on curved surfaces. This method solves the problem that during the operation of existing multi-degree-of-freedom array inkjet printing devices, the coupled influence of multiple factors, such as changes in the surface tilt angle, feed speed oscillations, changes in the distance between the printhead and the substrate, and deviations between the pattern ejection frequency and feed speed of the end array printhead, leads to significant deviations between the actual printed pattern and the input pattern. This significantly affects the positional accuracy of multi-degree-of-freedom array inkjet printing on curved surfaces. Conventional cameras face significant challenges in detecting curved surfaces, 3D reconstruction is costly, and repeated experiments are required, making it difficult to achieve accurate positioning of curved surface patterns. This invention provides an effective solution for achieving efficient and high-precision printing of curved electronic components with a certain width.
[0009] To achieve the above objectives, the technical solution adopted in this proposal is as follows:
[0010] A method for detecting and controlling the positional accuracy of curved surface multi-degree-of-freedom array inkjet forming includes the following steps:
[0011] S1, the flexible material is bonded to the printing substrate, and then the target image is input into the curved surface multi-degree-of-freedom array inkjet printing system;
[0012] S2, the flexible material formed in S1 is spread on the image acquisition plane of the position accuracy detection system, the visual inspection system picks up the formed image, and then performs digital image processing on the image and marks the key point positions.
[0013] S3, perform pattern matching and key point position accuracy calculation on the image obtained from S2 and the key point positions with the target image input into the printing system in S1;
[0014] S4, then the position accuracy control system reconstructs the input image based on the position accuracy obtained in S3, the input image and the detected image, and generates a new input image;
[0015] S5, set the thresholds for average position accuracy, peak accuracy, and accuracy distribution variance, repeat steps S1 to S4 until the requirements are met, output the final print input image, and perform curved surface electronic printing on the substrate.
[0016] As a further design of this solution, the method of bonding flexible material to the substrate and inputting the target image into the curved multi-degree-of-freedom array inkjet printing system is as follows: Select the target electronic printing image, import it into the curved multi-degree-of-freedom array inkjet printing system to trigger the array printing head, and then the curved multi-degree-of-freedom array inkjet printing system forms the target pattern on the substrate with the flexible material bonded and cures it.
[0017] As a further design of this solution, the method for the vision inspection system to pick up the formed image is as follows: the flexible material that has been formed in S1 is removed and laid out on the image acquisition plane of the position accuracy detection system and fixed by a special fixture. The position accuracy detection system is a special industrial camera that has undergone visual distortion correction.
[0018] As a further design of this scheme, the method for processing the digital image within the detection receptive field and marking the key point positions is as follows: the target area is picked up by the position accuracy detection system and the resulting RGB digital image is processed by channel fusion, contrast enhancement, filtering, binarization and speckle detection, and finally the center coordinates and key point numbers of the key points are marked.
[0019] As a further design of this scheme, pixel matching and key point location accuracy calculation of the input image and the detected image include the following steps:
[0020] Step 1: Label the pixel and distance ratios of the input image in S1 and the pixel-processed image in S2, and calculate the ratio of each pixel in the input image and the detected image to the geodesic distance, so as to realize the pixel correspondence between the input image and the detected image;
[0021] Step 2: Sort the key points of the initial input image and the detected image from left to right and from top to bottom, and then select the two key points in the upper left corner of the image, which are also the first two key points in the initial input image and the detected image, as the pattern origins in the two images;
[0022] Step 3: Update the pixel distances of the key points in the two images relative to the origin of the pattern according to the key point order, convert them into geodesic distances according to the ratio of the detected pixels to the geodesic distance, and calculate the geodesic distances of the corresponding key points in the two images.
[0023] As a further design of this scheme, the input image is reconstructed by integrating the input image, the detected image, and the key point coordinate information to obtain the corrected input image, including the following steps:
[0024] Step 1: Based on the origin of the two images, and according to the detected image, geodesic distance, and pixel ratio in the input image, convert the coordinates of the key points in the detected image relative to the origin of the pattern in that image into the coordinates in the input image.
[0025] Step 2: Mark the key point coordinates of the detected image obtained in Step 1 in the input image to obtain the key point coordinates of the target key point on the pattern formed on the substrate by the action of the multi-degree-of-freedom array inkjet forming system under the influence of complex factors.
[0026] Step 3: The key points in the input image are the midpoints of the key points in the corrected image and the key points in the detected image. The input image is then reconstructed to obtain the corrected image, which serves as the input image for the next shaping step.
[0027] As a further design of this solution, an error threshold is set, and steps S1 to S4 are repeated until the requirements are met. The output is the final printed pattern, and curved surface electronic printing is performed on the substrate, including the following steps:
[0028] Step 1: Set the thresholds for the mean, variance, peak value, number of iterations, and threshold variation coefficient of the Euclidean distance between key points;
[0029] Step 2: Repeat S1 to S4 to calculate the geodesic distances of all corresponding key points in the two images obtained above, and calculate the statistical mean, variance, and maximum value;
[0030] Step 3: Compare the calculated mean, variance, and maximum value with the set threshold.
[0031] Step 4: If all values are less than the threshold, output the current input image as the input image for subsequent surface electronic printing; if all thresholds are not met, repeat steps 2 to 3 until the threshold is met or the iteration reaches the iteration number threshold. If the threshold is met, output the input image; if the iteration number threshold is reached, increase the threshold by the threshold change coefficient until the threshold is met and output the optimal printing input image.
[0032] As a further design of this scheme, the final method for direct electronic printing on curved surfaces is as follows: After obtaining the optimal input image, the image is used as the input image for subsequent curved electronic printing. At this time, flexible substrate material is no longer added to the substrate, and electronic patterns are directly printed on the substrate.
[0033] The beneficial effects of this invention are:
[0034] (1) The method for position accuracy detection and control of curved multi-degree-of-freedom array inkjet forming designed in this invention is effective in achieving closed-loop control of position accuracy of curved multi-degree-of-freedom array inkjet forming with a certain width under the evaluation of multiple factors such as actual cost, detection effect and application scenario for image-input based curved multi-degree-of-freedom array inkjet forming device.
[0035] (2) The curved multi-degree-of-freedom array inkjet forming position accuracy detection and control method designed in this invention integrates various difficult factors in actual printing tasks, such as coordinate system calibration error, robot motion error, printing frequency and feed speed matching error and motion trajectory interpolation error, to achieve end-to-end control of forming position accuracy based on image, effectively solving the problem of difficult factors coupled with multiple factors.
[0036] (3) The curved multi-degree-of-freedom array inkjet forming position accuracy detection and control method designed in this invention addresses the problems of low image clarity and low contrast between substrate and pattern in the process of curved electronic printing. It designs digital image processing method and key point annotation method for the image obtained in the receptive field. Attached Figure Description
[0037] Figure 1 is a schematic diagram of inputting a target pattern and performing printing according to an embodiment of the present invention.
[0038] Figure 2 is a schematic diagram of the visual detection described in an embodiment of the present invention.
[0039] Figure 3 is a schematic diagram of digital image processing and key point annotation of the initial output image according to an embodiment of the present invention. The left image is the initial image captured by the camera after the curved pattern obtained by the initial printing parameters is spread out, and the right image is the image after the position accuracy detection system has processed the image.
[0040] Figure 4 is a schematic diagram of the error distribution of key points corresponding to the initial output image in an embodiment of the present invention.
[0041] Figure 5 is a schematic diagram of the input image reconstruction algorithm according to an embodiment of the present invention.
[0042] Figure 6 is a flowchart of the position accuracy detection and control system algorithm according to an embodiment of the present invention.
[0043] Figure 7 is a schematic diagram of the optimal input pattern according to an embodiment of the present invention.
[0044] Figure 8 is a schematic diagram of the optimal output image digital image processing and key point annotation according to an embodiment of the present invention. The left image is the initial image captured by the camera after the curved pattern obtained by the printing parameters after correction is spread out, and the right image is the image after the position accuracy detection system has processed the image.
[0045] Figure 9 is a schematic diagram of the error distribution of key points corresponding to the optimal output image according to an embodiment of the present invention.
[0046] Figure 10 is a flowchart of the method of the present invention. Detailed Implementation
[0047] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without inventive effort are within the protection scope of the present invention.
[0048] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.
[0049] As shown in Figure 10, this invention discloses a method for detecting and controlling the positional accuracy of curved surface multi-degree-of-freedom array inkjet forming, comprising the following steps:
[0050] (1) The flexible material is bonded to the printing substrate, and then the target image is input into the curved surface multi-degree-of-freedom array inkjet printing system;
[0051] (2) The flexible material formed by S1 is spread on the image acquisition plane of the position accuracy detection system, and the visual inspection system picks up the formed image, and then performs digital image processing on the image and marks the key point positions.
[0052] (3) Perform pattern matching and key point position accuracy calculation on the image obtained from S2 and the key point position with the target image input into the printing system in S1.
[0053] (4) Then, the position accuracy control system reconstructs the input image based on the position accuracy obtained in S3, the input image and the detected image to generate a new input image;
[0054] (5) Set the thresholds for average position accuracy, peak accuracy and accuracy distribution variance, repeat steps S1 to S4 until the requirements are met, and output the final print input image to perform curved surface electronic printing on the substrate.
[0055] As a preferred embodiment of the present invention, referring to FIG1, in step (1), the flexible material is adhered to the printing substrate, and then the target electronic printing pattern is selected and input into the curved multi-degree-of-freedom array inkjet printing system, which performs the forming task and solidifies the target electronic pattern on the flexible material.
[0056] As a preferred embodiment of the present invention, referring to FIG2, in step (2), the formed flexible material is removed and spread on the image acquisition plane of the position accuracy detection system and fixed by a special fixture. The position accuracy detection system is a special industrial camera that has undergone visual distortion correction.
[0057] As a preferred embodiment of the present invention, referring to FIG3, in step (2), the digital image within the detection receptive field is processed. Using an OpenCV-based interface, the target area is first picked up by the positional accuracy detection system and the obtained RGB digital image is fused to select the G channel image with better imaging effect. Then, contrast enhancement processing is performed using an adaptive local histogram with a contrast threshold of 150 and an image block size of 15×15. Afterwards, Gaussian filtering with a Gaussian kernel size of 9×9 and a standard deviation of 0 and median filtering with a median kernel size of 15×15 are used to remove Gaussian noise and salt-and-pepper noise. Finally, binarization processing based on the large law method with a pixel threshold of 100-255 and a spot detection algorithm based on feature matching with a minimum spot distance threshold of 75 are used to mark the center coordinates and key point numbers of the key points.
[0058] As a preferred embodiment of the present invention, referring to FIG4, in step (3), the process of calculating the pixel matching and key point position accuracy of the input image and the detected image includes: marking the pixel and distance ratios of the input image in S1 and the image after pixel processing in S2, calculating the ratio of each pixel in the input image and the detected image to the geodesic distance, so as to realize the pixel correspondence between the input image and the detected image; sorting the key points of the initial input image and the detected image from left to right and from top to bottom, and then selecting the two points with the first number in the key points of the image at the top left and the first number in the key points of the initial input image and the detected image as the pattern origins in the two images; updating the pixel distances of the key points in the two images relative to the pattern origins according to the key point order, converting them to geodesic distances according to the ratio of the detected pixels to the geodesic distances, and calculating the geodesic distances of the corresponding key points in the two images.
[0059] As a preferred embodiment of the present invention, referring to FIG5, in step (4), the process of reconstructing the input image by integrating the input image, the detected image, and the key point coordinate information to obtain the corrected input image includes: corresponding to the image origin in the two images, converting the coordinates of the key points in the detected image relative to the pattern origin in the image into coordinates in the input image according to the detected image, geodetic distance, and pixel ratio relationship in the input image; marking the converted key point coordinates of the detected image in the input image to obtain the key point coordinates of the target key points. After the curved multi-degree-of-freedom array inkjet forming system under the influence of complex factors, the key point coordinates of the pattern formed on the substrate are obtained; the key point in the input image is the midpoint between the key point in the corrected image and the key point in the detected image, thereby reconstructing the input image to obtain the corrected image, which is used as the input image for the next forming. The horizontal and vertical pixels of key point A in the input image are x and y, respectively, and the horizontal and vertical pixels of key point A′ in the detected image are x′ and y′, respectively. The horizontal and vertical pixels x″ and y″ of key point A″ in the final corrected image can be obtained by solving the following formula.
[0060] Where x,y are the pixel positions of the target pattern; x′,y′ are the pixel positions of the detected pattern; and x″,y″ are the target pixel positions of the input pattern after correction by this paper.
[0061] As a preferred embodiment of the present invention, referring to Figure 6, in step (5), setting an error threshold and repeating steps S1 to S4 until the requirements are met, the output is the final printed pattern. The process of performing curved surface electronic printing on the substrate includes: setting the mean threshold, variance threshold, peak threshold, iteration number threshold, and threshold change coefficient of the Euclidean distance of key points; repeating S1 to S4, calculating the geodesic distance of all corresponding key points in the two images obtained above, and calculating the statistical mean, variance, and maximum value of the corresponding key points in the two images; and comparing the calculated mean, variance, and maximum value with the set... Thresholds are compared; if all are less than the threshold, the current input image is output as the input image for subsequent curved surface electronic printing; if not all thresholds are met, iteration continues until the threshold is met or the iteration count threshold is reached. If the threshold is met, the input image is output as shown in Figure 7, and the output image detection is shown in Figure 8; if the iteration count threshold is reached, the threshold is increased by the threshold change coefficient until the threshold is met and the optimal printing input image is output, as shown in Figure 4. The mean, variance, and maximum value of the key point position accuracy obtained from the initial input image detection are 11.162 mm and 51.265 mm, respectively. 2 The accuracy was 23.518 mm; after 5 iterations, the output is shown in Figure 9. At this point, the mean, variance, and maximum accuracy of the key point positions detected were 0.629 mm, 0.153 mm, and 23.518 mm, respectively. 2 And 1.688mm.
[0062] In a preferred embodiment of the present invention, after obtaining the optimal input image, the image is used as the input image for subsequent curved surface electronic printing. At this time, flexible substrate material is no longer added to the substrate, and electronic patterns are directly printed on the substrate.
[0063] The technical means disclosed in this invention are not limited to those disclosed in the above embodiments, but also include technical solutions composed of any combination of the above technical features.
Claims
1. A method for detecting and controlling the positional accuracy of multi-degree-of-freedom array inkjet forming on curved surfaces, characterized in that, Includes the following steps: S1: The flexible material is bonded to the printing substrate, and then the target image is input into the curved surface multi-degree-of-freedom array inkjet printing system; S2: The flexible material formed in S1 is spread on the image acquisition plane of the position accuracy detection system. The visual inspection system picks up the formed image, and then performs digital image processing on the image and marks the key point positions. S3: Perform pattern matching and key point position accuracy calculation on the image obtained from S2 and the key point positions with the target image input into the printing system in S1. S4: The position accuracy control system reconstructs the input image based on the position accuracy obtained in S3, the input image, and the detected image to generate a new input image; S5: Set the thresholds for average positional accuracy, accuracy distribution variance, and peak accuracy. Repeat steps S1 to S4 until the requirements are met. The output is the final print input image, and curved surface electronic printing is performed on the printing substrate.
2. The method for detecting and controlling the positional accuracy of curved surface multi-degree-of-freedom array inkjet forming according to claim 1, characterized in that, In S1, the target electronic printing image is selected and imported into the curved multi-degree-of-freedom array inkjet printing system to trigger the array printing nozzle. The curved multi-degree-of-freedom array inkjet printing system then forms the target pattern on the substrate with the flexible material bonded to it and cures it.
3. The method for detecting and controlling the positional accuracy of curved surface multi-degree-of-freedom array inkjet forming according to claim 1, characterized in that, In S2, the flexible material formed in S1 is removed and laid out on the image acquisition plane of the position accuracy detection system, and fixed by a special fixture. The position accuracy detection system is a special industrial camera that has undergone visual distortion correction.
4. The method for detecting and controlling the positional accuracy of curved surface multi-degree-of-freedom array inkjet forming according to claim 1, characterized in that, In S2, the positional accuracy detection system picks up the target area and performs channel fusion, contrast enhancement, filtering, binarization, and speckle detection on the resulting RGB digital image, finally marking the center coordinates and key point numbers of the key points.
5. The method for detecting and controlling the positional accuracy of curved surface multi-degree-of-freedom array inkjet forming according to claim 1, characterized in that, In step S3, the image processed in S2 is compared with the target image input into the printing system in S1 for pixel matching and key point position accuracy calculation, including the following steps: S3-1, perform pixel and distance ratio annotation on the input image in S1 and the image after pixel processing in S2, calculate the ratio relationship between each pixel in the input image and the detected image and the geodesic distance, so as to realize the pixel correspondence between the input image and the detected image; S3-2, sort the key points of the initial input image and the detected image from left to right and from top to bottom, and then select the two key points in the upper left corner of the image, which are also the first two key points in the initial input image and the detected image, as the pattern origins in the two images; S3-3, update the pixel distance between the key points in the two images relative to the origin of the pattern according to the key point order, convert the pixel distance to geodesic distance according to the ratio of pixel distance to geodesic distance obtained in S3-1, and calculate the geodesic distance between the corresponding key points in the two images.
6. The method for detecting and controlling the positional accuracy of curved surface multi-degree-of-freedom array inkjet forming according to claim 5, characterized in that, In S4, the input image is reconstructed by integrating the input image, the detected image, and the key point coordinate information to obtain the corrected input image. This includes the following steps: S4-1 corresponds to the image origin in the two images. Based on the detected image, geodesic distance, and pixel ratio relationship in the input image obtained in S3-1, the coordinates of the key points in the detected image relative to the pattern origin in the image are converted to the coordinates in the input image. S4-2, mark the key point coordinates of the detection image obtained by conversion in S4-1 in the input image. These are the key point coordinates of the pattern formed on the substrate after the action of the multi-degree-of-freedom array inkjet forming system under the influence of complex factors. S4-3, the key points in the input image are the midpoints of the key points in the corrected image and the key points in the detected image. The corrected image is obtained by reconstructing the input image, and this image is used as the input image for the next shaping.
7. The method for detecting and controlling the positional accuracy of curved surface multi-degree-of-freedom array inkjet forming according to claim 5, characterized in that, In step S5, an error threshold is set, and steps S1 to S4 are repeated until the requirements are met. The output is the final printed pattern, and curved surface electronic printing is performed on the substrate, including the following steps: S5-1 sets the threshold values for the mean, variance, peak value, number of iterations, and threshold variation coefficient of the geodesic distance of key points; S5-2, repeat S1 to S4, calculate the geodesic distance of all corresponding key points in the two images obtained in S3-3, and calculate the statistical mean, variance and maximum value; S5-3, compare the calculated mean, variance and maximum value with the set threshold; S5-4: If all values are less than the threshold, output the current input image as the input image for subsequent surface electronic printing. If none of the thresholds are met, repeat S5-2 to S5-3 until the threshold is met or the iteration reaches the iteration number threshold. If the threshold is met, output the input image. If the iteration number threshold is reached, increase the threshold by the threshold change coefficient until the threshold is met and output the optimal printing input image.
8. The method for detecting and controlling the positional accuracy of curved surface multi-degree-of-freedom array inkjet forming according to claim 1, characterized in that, In S5, after obtaining the optimal input image, the image is used as the input image for subsequent curved surface electronic printing. At this time, flexible substrate material is no longer added to the substrate, and electronic patterns are directly printed on the substrate.