Position accuracy detection and control method for inkjet forming on curved surface with multi-degree-of-freedom array

Abstract

The present invention provides a method for detecting and controlling the position accuracy of inkjet forming of curved surfaces with multiple degrees of freedom arrays. The method forms a target pattern on a printing substrate adhered with a flexible material through a curved surface multi-degree-of-freedom inkjet forming system, and then spreads the flexible material for the detection system to pick up the target image and perform image processing and key point annotation, and then calculates whether the key point position accuracy meets the threshold requirements and reconstructs the input image based on the detected image to output or perform re-forming detection. This method can effectively solve the problem of large deviations between the printed input pattern and the actual formed pattern caused by the coupling of multiple factors such as the feed speed fluctuation of the multi-axis motion device, motion vibration, printing inclination angle change, and ink path system pressure change in the current curved surface multi-degree-of-freedom array inkjet forming device; it greatly improves the printing efficiency and provides very effective technical support for achieving efficient and high-precision electronic printing of curved surfaces with multiple degrees of freedom of a certain width.

Description

Technical Field

[0001] The present invention belongs to the field of curved electronic component printing, and in particular relates to a method for detecting and controlling the position accuracy of ink droplets formed on a substrate surface during the inkjet forming process of a multi-degree-of-freedom array of a curved electronic device. Background Art

[0002] With the explosive growth of industries like electronic communications and aerospace, computer-aided design and manufacturing of electronic components such as chips, advanced circuits, and conformal antennas has become a current research hotspot. Compared to the more mature layered two-dimensional planar additive manufacturing, achieving model-driven manufacturing on spatial curved surfaces requires researchers to systematically establish three modules: model processing, motion control, and equipment design and manufacturing. Currently, simple curved multi-axis direct writing equipment offers solutions for the manufacture of curved electronic components. However, due to the need to improve its production efficiency and precision, it is difficult to meet the requirements of large-scale industrial production, resulting in high mass production costs. Due to the limitations of actuators and control methods, traditional two-dimensional printing is difficult to print high-precision curved conformal electronic components that meet the requirements.

[0003] In the curved surface multi-degree-of-freedom array inkjet printing system targeted by this article, an array printhead is mounted at the end of a multi-axis motion mechanism to achieve electronic printing on curved surfaces of a certain width. In theory, this system can achieve efficient and high-precision electronic printing on spatial surfaces with a certain curvature limit. However, the current implementation of multi-degree-of-freedom array inkjet forming of curved electronic components has the following shortcomings:

[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 path pressure, the actual forming position has a large deviation from the target position, the position accuracy is low, and it is difficult to ensure the consistency of the input pattern and the output pattern;

[0005] (2) During the operation of the curved multi-degree-of-freedom array inkjet forming device, when a robotic arm is used to clamp a camera to shoot shallow circuit patterns 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) During the operation of the curved surface multi-degree-of-freedom array inkjet forming device, when a three-dimensional scanner is used to scan and reconstruct the shallow circuit pattern of the curved surface, it is difficult to capture the small height changes of the curved surface and the cost is high.

[0007] How to cooperate with the surface multi-degree-of-freedom array inkjet forming device based on image input to achieve closed-loop control of the position accuracy of surface multi-degree-of-freedom inkjet forming of a certain width under the influence of multiple factors such as actual cost, detection effect and application scenario is an important issue that urgently needs to be solved to achieve efficient and high-precision electronic printing on curved surfaces. It has far-reaching significance for the realization of integrated forming of curved electronic components. Summary of the Invention

[0008] In order to solve the above problems, the present invention discloses a method for detecting and controlling the position accuracy of curved surface multi-degree-of-freedom array inkjet forming, so as to solve the problem that during the operation of the existing curved surface multi-degree-of-freedom array inkjet forming device, due to the coupling influence of multiple factors such as the change of curved surface inclination angle, feed speed oscillation, change of distance between the nozzle and the substrate, and the deviation of the pattern injection frequency of the end array nozzle and the feed speed, the actual printed pattern has a large deviation from the input pattern, and the position accuracy of the curved surface multi-degree-of-freedom array inkjet forming is greatly affected. Conventional cameras have great difficulty in detecting curved surfaces, the cost of three-dimensional reconstruction is high, and repeated experiments are required, making it difficult to achieve accurate positioning of the curved surface pattern. This 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 solutions adopted in this plan are as follows:

[0010] A method for detecting and controlling the position accuracy of inkjet forming on a curved surface with multiple degrees of freedom arrays, comprising the following steps:

[0011] S1, the flexible material is adhered 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, spreading the flexible material formed in S1 on the image acquisition plane of the position accuracy detection system, and the visual detection system picks up the formed image, and then performs digital image processing on the image and marks the key point positions;

[0013] S3, performing pattern matching and key point position accuracy calculation on the image and key point positions obtained by S2 and the target image input to the printing system in S1;

[0014] S4, the position accuracy control system then 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;

[0015] S5, setting thresholds for average position accuracy, peak accuracy, and accuracy distribution variance, repeating steps S1 to S4 until the requirements are met, outputting the final print input image, and performing curved surface electronic printing on the printing substrate.

[0016] As a further design of this solution, the method of adhering a flexible material to a printing substrate and inputting a target image into a curved surface multi-degree-of-freedom array inkjet printing system is as follows: a target electronic printing image is selected, and it is imported into the curved surface multi-degree-of-freedom array inkjet printing system to trigger the array print head, and then the curved surface multi-degree-of-freedom array inkjet printing system forms a target pattern on the printing substrate adhered with the flexible material and solidifies it.

[0017] As a further design of this solution, the method for the visual inspection system to pick up the formed image is as follows: the flexible material formed in S1 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 been corrected for visual distortion.

[0018] As a further design of this solution, the method for processing the digital image within the detection receptive field and marking the key point positions is as follows: the position accuracy detection system picks up the target area and performs channel fusion, contrast enhancement, filtering, binarization and spot detection on the obtained RGB digital image, and finally marks the key point center coordinates and key point numbers.

[0019] As a further design of this solution, pixel matching and key point position accuracy calculation of the input image and the detected image include the following steps:

[0020] Step 1: Perform pixel and distance ratio annotation on the input image in S1 and the pixel-processed image in S2, and calculate the ratio between each pixel and the geodesic distance in the input image and the detected image to achieve 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 top left key point of the image, which is also the first-numbered key point in the initial input image and the detected image, as the pattern origin in the two images;

[0022] Step 3: Update the pixel distances of the key points in the two images relative to the pattern origin in the order of the key points, convert them into geodesic distances according to the proportional relationship between the detected pixels and the geodesic distances, and calculate the geodesic distances of the corresponding key points in the two images.

[0023] As a further design of this solution, 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, which includes the following steps:

[0024] Step 1: Corresponding to the image origins in the two images, the coordinates of the key points in the detected image relative to the pattern origin in the image are converted to coordinates in the input image based on the detected image, the geodesic distance, and the pixel ratio in the input image;

[0025] Step 2: Mark the input image with the coordinates of the key points of the detection image converted in step 1, and obtain the effect of the curved surface multi-degree-of-freedom array inkjet forming system under the influence of complex factors, and the coordinates of the key points of the target key points on the key point coordinates of the pattern formed on the printing substrate;

[0026] Step 3: The key point in the input image is the midpoint between the key point in the correction image and the key point in the detection image. The input image is reconstructed to obtain a correction image, which is used as the input image for the next shaping.

[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. Outputting the final printed pattern and performing curved surface electronic printing on the printing substrate includes the following steps:

[0028] Step 1: Set the mean threshold, variance threshold, peak threshold, iteration threshold and threshold variation coefficient of the Euclidean distance of 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 are less than the threshold, the input image at this time is output as the input image for subsequent curved electronic printing; if all thresholds are not met, repeat steps 2 to 3 until the threshold is met or the iteration number threshold is reached. If the threshold is met, the input image is output. If the iteration number threshold is reached, the threshold is increased according to the threshold change coefficient until the threshold is met and the optimal printed input image is output.

[0032] As a further design of this solution, the method for finally performing curved surface electronic direct printing is as follows: after obtaining the optimal input image, the image is used as the input image for subsequent curved surface electronic printing. At this time, the flexible substrate material is no longer added to the printing substrate, and the electronic pattern is directly printed on the substrate.

[0033] Beneficial effects of the present invention:

[0034] (1) The method for detecting and controlling the position accuracy of inkjet forming on a curved surface with multiple degrees of freedom arrays designed by the present invention is designed for an image-based curved surface with multiple degrees of freedom arrays. It effectively realizes closed-loop control of the position accuracy of inkjet forming on a curved surface with multiple degrees of freedom arrays with a certain width under the evaluation of multiple factors such as actual cost, detection effect, and application scenarios.

[0035] (2) The method for detecting and controlling the position accuracy of inkjet forming on a curved surface with multiple degrees of freedom arrays designed by the present invention integrates various difficulty factors involved 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 images, effectively solving the problem of difficulty in multi-factor coupling relationships.

[0036] (3) The method for detecting and controlling the position accuracy of inkjet forming on a curved surface with multiple degrees of freedom designed in the present invention addresses the problems of low image clarity and low contrast between the substrate and the pattern during electronic printing on curved surfaces, and designs a digital image processing method and a key point marking method for the image obtained within the receptive field. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a schematic diagram of inputting a target pattern and executing printing according to an embodiment of the present invention.

[0038] Figure 2 This is a schematic diagram of visual detection according to an embodiment of the present invention.

[0039] Figure 3 This is a schematic diagram of the digital image processing and key point annotation of the initial output image described in an embodiment of the present invention, wherein the left image is the initial image captured by the camera after the surface pattern formed by the initial printing parameters is spread out, and the right image is the image after being processed by the position accuracy detection system.

[0040] Figure 4 Schematic diagram of the error distribution of key points corresponding to the initial output image according to an embodiment of the present invention.

[0041] Figure 5 Schematic diagram of the input image reconstruction algorithm according to an embodiment of the present invention.

[0042] Figure 6 This is a flow chart of the algorithm for position accuracy detection and control system according to an embodiment of the present invention.

[0043] Figure 7 This is a schematic diagram of the optimal input pattern according to an embodiment of the present invention.

[0044] Figure 8 This is a schematic diagram of the digital image processing and key point annotation of the optimal output image according to an embodiment of the present invention, wherein the left image is the initial image captured by the camera after the surface pattern formed by the corrected printing parameters is spread out, and the right image is the image after being processed by the position accuracy detection system.

[0045] Figure 9 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 Flow chart of the method of the present invention. DETAILED DESCRIPTION

[0047] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are only intended to illustrate the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0048] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0049] like Figure 10 As shown, the embodiment of the present invention discloses a method for detecting and controlling the position accuracy of inkjet forming on a curved surface with multiple degrees of freedom, comprising the following steps:

[0050] (1) The flexible material is adhered 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 formed image is picked up by the visual detection system, and then the image is digitally processed and the key point positions are marked;

[0052] (3) performing pattern matching and key point position accuracy calculation on the image and key point positions obtained by S2 and the target image input to the printing system in S1;

[0053] (4) The position accuracy control system then 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) setting thresholds for average position accuracy, peak accuracy, and accuracy distribution variance, repeating steps S1 to S4 until the requirements are met, outputting the final print input image, and performing curved surface electronic printing on the printing substrate;

[0055] As a preferred embodiment of the present invention, refer to Figure 1 In step (1), a flexible material is adhered to a printing substrate, and then a target electronic printing pattern is selected and input into a curved surface multi-degree-of-freedom array inkjet printing system, which performs a forming task and solidifies the target electronic pattern on the flexible material;

[0056] As a preferred embodiment of the present invention, refer to Figure 2In 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 been corrected for visual distortion.

[0057] As a preferred embodiment of the present invention, refer to Figure 3 In step (2), the digital image within the detection receptive field is processed using an opencv-based interface. First, the position accuracy detection system picks up the target area and performs channel fusion on the obtained RGB digital image to select the G channel image with better imaging effect, and uses a contrast threshold of 150 and an adaptive local histogram with an image block size of 15×15 for contrast enhancement processing. Then, a Gaussian filter with a Gaussian kernel size of 9×9 and a standard deviation of 0 and a median filter with a median filter kernel size of 15×15 are used to remove Gaussian noise and salt and pepper noise. Then, a binarization process based on the large law and a pixel threshold of 100 to 255 and a spot detection algorithm based on feature matching with a minimum spot distance threshold of 75 are used. Finally, the center coordinates of the key points and the key point numbers are marked.

[0058] As a preferred embodiment of the present invention, refer to Figure 4 In step (3), the process of calculating pixel matching and key point position accuracy of the input image and the detected image includes: marking the input image in S1 and the pixel-processed image in S2 with pixel and distance ratios, calculating the proportional 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; 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 key point at the upper left of the image, which is also the first-numbered key point in the initial input image and the detected image, as the pattern origin in the two images; updating the pixel distances of the key points in the two images relative to the pattern origin according to the key point sequence, converting them into geodesic distances according to the proportional relationship between the detected pixels and 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, refer to Figure 5In step (4), the input image, the detected image and the key point coordinate information are comprehensively integrated to reconstruct the input image and obtain the corrected input image. The process includes: corresponding to the image origin in the two images, the coordinates of the key point in the detected image relative to the pattern origin in the image are converted into coordinates in the input image according to the detected image, the geodesic distance and the pixel ratio in the input image; the converted key point coordinates of the detected image are marked in the input image to obtain the target key point coordinates. After the curved surface multi-degree-of-freedom array inkjet forming system under the influence of complex factors, the key point coordinates of the pattern formed on the printing substrate are obtained; the key point in the input image is the midpoint of the key point in the corrected image and the key point in the detected image, thereby reconstructing the input image to obtain a corrected image, which is used as the input image for the next forming. The horizontal and vertical pixels of the key point A in the input image are x and y respectively, corresponding to the key point A in the detected image. ′ The horizontal and vertical pixels of the point are x ′ and y ′ Finally, the key point A in the corrected image ″ Point horizontal and vertical pixels x ″ and y ″ It can be solved by the following formula.

[0060]

[0061] Where x, y are the target pattern pixel positions; x′, y′ are the detected pattern pixel positions; and x″, y″ are the target pixel positions obtained after the input pattern is corrected by this paper.

[0062] As a preferred embodiment of the present invention, refer to Figure 6 In step (5), an error threshold is set, and steps S1 to S4 are repeated until the requirements are met, and the final printed pattern is outputted on the printing substrate. The process of performing curved electronic printing includes: setting the mean threshold, variance threshold, peak threshold, iteration number threshold and threshold variation coefficient of the Euclidean distance of the 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; comparing the calculated mean, variance and maximum value with the set threshold; if all are less than the threshold, outputting the input image at this time as the input image for subsequent curved electronic printing; if all thresholds are not met, continuing the iteration until the threshold is met or the iteration number threshold is reached, and if the threshold is met, outputting the input image as shown in FIG. Figure 7 As shown, the output image detection is as follows Figure 8 As shown; if the iteration number threshold is reached, the threshold is increased according to the threshold change coefficient until the threshold is met and the optimal print input image is output, as shown Figure 4The average, variance and maximum values ​​of the key point position accuracy detected from the initial input image are 11.162mm, 51.265mm respectively. 2 and 23.518mm; and after 5 rounds of iterations the output is as follows Figure 9 As shown, the average, variance and maximum values ​​of the key point position accuracy detected at this time are 0.629mm, 0.153mm respectively. 2 and 1.688mm.

[0063] As 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, no flexible substrate material is added to the printing substrate, and the electronic pattern is directly printed on the substrate.

[0064] The technical means disclosed in the solution of the present invention are not limited to the technical means disclosed in the above-mentioned embodiment, but also include technical solutions composed of any combination of the above technical features.

Claims

1. A method for detecting and controlling the position accuracy of inkjet forming on a curved surface with multiple degrees of freedom array, characterized in that: The following steps are involved: S1: The flexible material is adhered to the printing substrate, and then the target image is input into the curved surface multi-degree-of-freedom array inkjet printing system; S2: Spread the flexible material formed in S1 on the image acquisition plane of the position accuracy detection system, pick up the formed image by the visual detection system, and then perform digital image processing on the image and mark the key point positions; S3: performing pattern matching and key point position accuracy calculation on the image and key point positions obtained by S2 and the target image input to the printing system in S1; S4: The position accuracy control system performs a reconstruction calculation on 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 position accuracy, accuracy distribution variance, and peak accuracy, repeat steps S1 to S4 until the requirements are met, output the final printed input image, and perform curved electronic printing on the printing substrate; In S3, pixel matching and key point position accuracy calculation are performed on the image processed in S2 and the target image input to the printing system in S1, including the following steps: S3-1, performing pixel and distance ratio annotation on the input image in S1 and the image after pixel processing in S2, calculating the ratio between each pixel and the geodesic distance in the input image and the detected image to achieve pixel correspondence between the input image and the detected image; S3-2, 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 top left key point of the image, which is also the first-numbered key point in the initial input image and the detected image, as the pattern origin in the two images; S3-3, update the pixel distances of the key points in the two images relative to the pattern origin according to the order of the key points, convert them into geodesic distances according to the proportional relationship between the pixel and geodesic distance obtained in S3-1, and calculate the geodesic distances of the corresponding key points in the two images.

2. The method for detecting and controlling position accuracy of inkjet forming on a curved surface with multiple degrees of freedom array according to claim 1, characterized in that: In S1, a target electronic printing image is selected and introduced into a curved surface multi-degree-of-freedom array inkjet printing system to trigger an array print head, and then the curved surface multi-degree-of-freedom array inkjet printing system forms a target pattern on a printing substrate adhered with a flexible material and solidifies it.

3. The method for detecting and controlling position accuracy of inkjet forming on a curved surface with multiple degrees of freedom array according to claim 1, characterized in that: In S2, the flexible material formed in S1 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 been corrected for visual distortion.

4. The method for detecting and controlling position accuracy of inkjet forming on a curved surface with multiple degrees of freedom array according to claim 1, characterized in that: In S2, the position accuracy detection system picks up the target area and performs channel fusion, contrast enhancement, filtering, binarization and spot detection on the obtained RGB digital image, and finally marks the key point center coordinates and key point numbers.

5. The method for detecting and controlling position accuracy of inkjet forming on a curved surface with multiple degrees of freedom array according to claim 1, characterized in that: In S4, the input image, the detected image, and the key point coordinate information are comprehensively integrated to reconstruct the input image to obtain a corrected input image, including the following steps: S4-1, corresponding to the image origins in the two images, converting the coordinates of the key points in the detected images relative to the pattern origin in the images into coordinates in the input image based on the detected images obtained in S3-1, the geodesic distance, and the pixel ratio relationship in the input image; S4-2, marking the input image with the coordinates of the key points of the detection image converted in S4-1, which are the coordinates of the key points of the target key points in the pattern formed on the printing substrate after the curved surface multi-degree-of-freedom array inkjet forming system under the influence of complex factors; S4-3, the key point in the input image is the midpoint between the key point in the correction image and the key point in the detection image, and the input image is reconstructed and calculated to obtain a correction image, which is used as the input image for the next shaping.

6. The method for detecting and controlling position accuracy of inkjet forming on a curved surface with multiple degrees of freedom array according to claim 1, characterized in that: In S5, an error threshold is set, and steps S1 to S4 are repeated until the requirements are met. The final printed pattern is output and curved surface electronic printing is performed on the printing substrate, including the following steps: S5-1, setting the mean threshold, variance threshold, peak threshold, iteration number threshold and threshold variation coefficient of the key point geodesic distance; S5-2, repeat S1 to S4, calculate the geodesic distances of all corresponding key points in the two images obtained in S3-3, and calculate the statistical mean, variance, and maximum value; S5-3, comparing the calculated mean, variance and maximum value with the set threshold; S5-4, if all are less than the threshold, then the input image at this time is output as the input image for subsequent curved electronic printing; if all thresholds are not met, then S5-2 to S5-3 are repeated until the threshold is met or the iteration number threshold is reached. If the threshold is met, then the input image is output. If the iteration number threshold is reached, then the threshold is increased according to the threshold change coefficient until the threshold is met and the optimal printed input image is output.

7. The method for detecting and controlling position accuracy of inkjet forming on a curved surface with multiple degrees of freedom array according to claim 1, characterized in that: In S5, after the optimal input image is obtained, the image is used as the input image for subsequent curved surface electronic printing. At this time, no flexible substrate material is added to the printing substrate, and the electronic pattern is directly printed on the substrate.

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