Method and system for dynamically measuring rebound height of high-performance fiber fabric

Abstract

The invention provides a high-performance fiber fabric rebound height dynamic measurement method and system, and belongs to the technical field of textile material testing and digital image processing identification, the measurement system comprises an image acquisition device, a light source, a light source controller and an industrial personal computer, the light source is located on one side of a fabric, the light source is horizontally arranged and is perpendicular to the side face of the fabric for irradiation, and the light source controller is connected with the industrial personal computer; the image acquisition equipment vertically shoots the side surface of the fabric through a light through hole in the center of the light source for image acquisition; the measuring method comprises the steps of fabric sample preparation, compaction test, springback image acquisition, image preprocessing, fabric springback edge fitting and fabric springback data calibration, and finally fabric springback performance characterization and height quantitative evaluation. Therefore, the performance characterization and quantitative evaluation of the fabric rebound process are realized, the operation process is simplified, the test accuracy is improved, and the method is suitable for evaluating the rebound performance of various high-performance fiber fabrics.

Description

Technical Field

[0001] The invention belongs to the technical field of textile material testing and digital image processing and identification, and in particular relates to a method and system for dynamically measuring the rebound height of high-performance fiber fabrics based on machine vision. Background Art

[0002] High-performance fiber fabrics are widely used in aerospace, military equipment, protective clothing and other fields. Their fiber volume fraction is closely related to the mechanical and thermodynamic properties of composite materials. During the molding process, the pressurized densification process is often used to compress the fabric along the thickness direction to a specific fiber volume fraction, but the fabric deformation is viscoelastic deformation. After the pressure is released, the fabric will rebound, resulting in a decrease in the fiber volume fraction. Therefore, by accurately measuring the fabric rebound height, its fiber volume content can be accurately calculated to ensure that the fabric molding quality meets the process requirements.

[0003] In the prior art, the fabric rebound height measurement method mostly uses a steel ruler with a graduation value of 1 mm to measure the vertical distance between the working surface of the indicator plate and the working surface of the workbench, such as the national standards GB / T 22796-2021 and GB / T 24252-2019. A contact or non-contact displacement sensor can also be used to measure the distance from the sample plate to the bottom of the sample under different states.

[0004] With the development of science and technology, machine vision methods have been used for fabric defect detection, such as CN116309367A, a fiber fabric surface defect detection method based on machine vision, CN113643289A, a fabric surface defect detection method and system based on image processing, CN105654121B, a complex jacquard fabric defect detection method based on deep learning, etc. However, the current fabric rebound performance test method has problems such as complex operation, low efficiency, and poor measurement accuracy, which makes it difficult to meet the requirements of high-performance fiber fabric rebound height.

[0005] Therefore, there is an urgent need to invent a dynamic measurement method and system for the rebound height of high-performance fiber fabrics after compaction, so as to accurately calculate their fiber volume fraction and ensure the quality of fabric molding. Summary of the invention

[0006] The problem to be solved by the present invention is to provide a method and system for dynamically measuring the rebound height of high-performance fiber fabrics.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is: a dynamic measurement method for the rebound height of high-performance fiber fabrics, which is used to record the fabric rebound process and quantitatively evaluate the fabric rebound height, comprising the following steps: S1. Fabric sample preparation: Place the fabric that has been woven and formed but not compacted in a tooling and place it on a universal tensile testing machine; The fabric fibers are smooth and undamaged.

[0008] S2. Fabric compaction test: The fabric is compacted by constant speed method or constant pressure method. The pressure head moves from the origin to compact the fabric. After the fabric is compressed to a certain height, that is, the height of the compressed fabric basically does not change. Then, according to the process requirements, the load is released or the compression load is maintained unchanged for a period of time before the load is released. When the load is released, the pressure head moves to the original position at a constant speed; S3, fabric rebound image acquisition: perform image acquisition of the fabric rebound process after the load is released, and obtain the rebound shape of the fabric at each moment by acquiring each frame of image; S4. Image preprocessing: Obtain lossless original images from image acquisition equipment, and perform filtering and enhancement processing to highlight fiber features for easy calibration and measurement: Perform linear smoothing on the original grayscale value of the input image to obtain the average grayscale value; Figure 2 The binary image is processed using the morphological dilation method to obtain enhanced grayscale image pixels.

[0009] S5, fabric rebound edge fitting: according to the obtained average gray value, original gray value and gray value image pixel after filtering enhancement, the enhanced gray value is calculated, that is, the new image pixel is obtained, and the formula is as follows: Among them, res: is the new image pixel; round((orig - mean)×Factor) is the gray value image pixel after filtering and enhancement; orig is the original gray value; mean is the average gray value; Factor is the factor; round is the rounding symbol; a, b, and c are all fitting adjustment coefficients.

[0010] Since the pixel grayscale value at the edge of the fabric has a large gradient, the nonlinear least squares method is used to fit the new image pixels to obtain the pixel points at the edge of the fabric rebound. The pixel points at the edge are further fitted to obtain the fabric edge curve.

[0011] S6. Fabric rebound data calibration: Use a high-precision calibration plate to calibrate the camera, establish a mapping relationship between the side length of the checkerboard calibration plate and the number of pixels occupied by the corresponding image, and obtain single-pixel accuracy: A=L / NUM Where: A is the single pixel accuracy, mm / pixel; L is the side length of the chessboard calibration plate, mm; NUM is the number of pixels occupied by the corresponding image, pixle.

[0012] S7. Characterization and highly quantitative evaluation of fabric rebound performance: The dynamic change process of fabric rebound is observed online. Through single-pixel precision A, the image coordinate system and the actual physical coordinate system are associated to quantitatively evaluate the fabric rebound height, thus achieving a comprehensive characterization of fabric rebound.

[0013] The present invention also provides a high-performance fiber fabric rebound height dynamic measurement system, including an image acquisition device, a light source, a light source controller and an industrial computer. The light source is located on one side of the fabric, the light source is horizontally arranged, and irradiates perpendicularly to the side of the fabric. The light source is connected to the light source controller. The image acquisition device vertically shoots the side of the fabric through the light hole in the center of the light source to acquire the image. The image acquisition device is connected to the industrial computer via a data communication interface.

[0014] Among them, the image acquisition device is an industrial camera with a resolution of 5120 pixels × 5120 pixels and a required acquisition frame rate of 41fps; the industrial FA high-definition lens image resolution of the industrial camera is greater than or equal to 2500w pixels, and the acquired image has clear boundaries, which is convenient for accurately calculating the fabric rebound height.

[0015] Among them, the light source adopts a dome light source with high uniformity of diffuse reflection; the light source controller is required to output power that meets the requirements of the light source, and has an I / O receiving port, and is used in coordination with an industrial camera; the dome light source is connected to the light source controller to cooperate with the industrial camera for image acquisition, and the light source controller is triggered by the I / O signal of the industrial camera, thereby realizing the synchronous triggering of the industrial camera and the dome light source.

[0016] The industrial computer has a RAM capacity of 32 GB or more, a solid-state storage space of 512 GB or more, and a CPU version of i7-12th or more.

[0017] Among them, the communication speed of the data communication interface, data line, and acquisition card involved in the present invention meets the requirements of high-speed image transmission, requiring the use of a 10 Gigabit network card and related 10 Gigabit network communication cables.

[0018] Due to the adoption of the above technical solution, the present invention has the following beneficial effects: The present invention utilizes machine vision technology to solve the problem that the internal structure of the fabric cannot be evaluated in real time, realizes the in-situ characterization of the rebound of high-performance fiber fabrics, can monitor the dynamic change process of fabric rebound in real time online, can quickly and accurately measure the fabric rebound process, calculate the final rebound height of the fabric, comprehensively characterize the fabric rebound performance, improve the fabric rebound measurement efficiency, and enhance the measurement accuracy.

[0019] The measurement method based on machine vision enhances the reliability and stability of the test and reduces the dependence on manual measurement and human error. The invention is applicable to fabrics of different types, specifications and sizes and has wide applicability and application prospects.

[0020] It can be seen that the present invention realizes the performance characterization and quantitative evaluation of the fabric rebound process, simplifies the operation process, improves the accuracy of the test, and is suitable for the evaluation of the rebound performance of various high-performance fiber fabrics. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention will be described in detail below with reference to the accompanying drawings and in combination with examples, and the advantages and implementation methods of the present invention will become more obvious. The contents shown in the accompanying drawings are only used to explain the present invention and do not constitute any limitation to the present invention in any sense. In the accompanying drawings: Figure 1 This is a usage status diagram of the high-performance fiber fabric rebound height dynamic measurement system of the present invention.

[0022] Figure 2 This is the original diagram of the rebound process of the high-performance fiber fabric of the present invention.

[0023] Figure 3 This is a diagram of the rebound process of high-performance fiber fabric after image preprocessing filtering and enhancement of the present invention.

[0024] Figure 4 Schematic diagram of the high-precision calibration plate of the present invention.

[0025] Figure 5 This is a diagram for characterizing and quantitatively evaluating the resilience performance of high-performance fiber fabrics.

[0026] In the figure: 1. Image acquisition equipment; 2. Light source; 3. Light source controller; 4. Industrial computer. DETAILED DESCRIPTION

[0027] like Figures 1 to 5 As shown, the present invention provides a method for dynamically measuring the rebound height of a high-performance fiber fabric, comprising the following steps: S1. Fabric sample preparation: Place the fabric that has been woven and not compacted in a tool and place it on a SHIMADZU AGS-X universal tensile testing machine.

[0028] Among them, the fabric samples are specified according to the test requirements, and it is ensured that the fabric fibers are flat and the fabric is not damaged.

[0029] S2. Fabric compaction test: The fabric is compacted by the constant speed method (compressing the fabric sample to a certain displacement at a certain speed). The pressure head moves from the origin to compact the fabric until the height of the compressed fabric basically does not change. Then, the load is released according to the process requirements or the compressed load is maintained unchanged for a period of time before the load is released. When releasing, the pressure head moves to the original position at a constant speed.

[0030] Specifically, the pressure head of the universal tensile testing machine starts to move at a constant speed of 1 mm / min at the origin to pressurize and compact the fabric, compressing the fabric to the height required by the process; after the load is released, the pressure head moves to the original position at a constant speed of 10 mm / min.

[0031] S3. Fabric rebound image acquisition: The image acquisition device 1 (Hikvision robot MV-CH250-90TC-C-NF camera), light source 2 (dome light source), IPC industrial computer and other test systems are used to acquire images of the fabric rebound process after the load is released. By acquiring each frame of the image, the rebound shape of the fabric at each moment is obtained.

[0032] Among them, the image exposure time is 0.02ms and the acquisition frame rate is 41fps.

[0033] S4, image preprocessing: obtain the lossless original image from the image acquisition device 1, and perform filtering and enhancement processing to highlight the fiber features for easy calibration and measurement: Perform linear smoothing on the original grayscale value of the input image to obtain the average grayscale value; Figure 2 The binary image is processed by morphological dilation method to obtain the gray value image pixels after filtering and enhancement.

[0034] S5, fabric rebound edge fitting: according to the obtained average gray value, original gray value and gray value image pixel after filtering enhancement, the enhanced gray value is calculated, that is, the new image pixel is obtained, and the formula is as follows: Among them, res: is the new image pixel; round((orig - mean)×Factor) is the gray value image pixel after filtering and enhancement; orig is the original gray value; mean is the average gray value; Factor is the factor; round is the rounding symbol; a, b, and c are all fitting adjustment coefficients.

[0035] Since the pixel grayscale value at the edge of the fabric has a large gradient, the nonlinear least squares method is used to fit the new image pixels to obtain the pixel points at the edge of the fabric rebound. The pixel points at the edge are further fitted to obtain the fabric edge curve.

[0036] In this embodiment, Figure 2 and Figure 3 As shown, the original grayscale value captured is defined as α , the gray value image pixel after filtering and enhancement of binary image processing is defined as β。 The effective pixel points in the captured image are fitted with the nonlinear least square method to obtain the fiber edge. β and α Perform image operations to obtain new image pixels δ : δ = 0.81 β+ 1.23 α+ 0.11 S6. Fabric rebound data calibration: Use a high-precision checkerboard calibration plate to calibrate the camera, such as Figure 4 As shown, a mapping relationship between the side length of the chessboard calibration plate and the number of pixels occupied by the corresponding image is established to obtain the single-pixel accuracy (conversion coefficient) of the image coordinate system and the physical coordinate system: A=L / NUM Where: A is the single pixel accuracy, mm / pixel; L is the side length of the chessboard calibration plate, mm; NUM is the number of pixels occupied by the corresponding image, pixle.

[0037] S7. Characterization and highly quantitative evaluation of fabric rebound performance: The dynamic change process of fabric rebound is observed online. Through single-pixel precision A, the image coordinate system and the actual physical coordinate system are associated to quantitatively evaluate the fabric rebound height, thus achieving a comprehensive characterization of fabric rebound.

[0038] Specifically, Figure 5 As shown, the new image pixels δ Convert it into actual distance to get the actual height of fiber rebound.

[0039] h′= A× δ-h in, h is the compaction height of the fabric, recorded by the universal tensile testing machine, mm; h´ is the fabric rebound height, mm.

[0040] like Figure 1 As shown, the present invention also provides a high-performance fiber fabric rebound height dynamic measurement system, including an image acquisition device 1, a light source 2, a light source controller 3 and an industrial computer 4. The light source 2 is located on one side of the fabric, and the light source 2 is horizontally arranged to illuminate the side of the fabric vertically. The light source 2 is connected to the light source controller 3. The image acquisition device 1 vertically shoots the side of the fabric through the light hole in the center of the light source 2 to acquire the image. The image acquisition device 1 is connected to the industrial computer 4 through a data communication interface. When in use, adjust the focal length and the light source, and adjust the working parameters of the universal tensile testing machine.

[0041] Among them, the image acquisition device 1 is an industrial camera with a resolution of 5120 pixels × 5120 pixels and a required acquisition frame rate of 41fps; the industrial FA high-definition lens image resolution of the industrial camera is greater than or equal to 2500w pixels, and the acquired image has clear boundaries, which is convenient for accurately calculating the fabric rebound height.

[0042] Among them, the light source 2 adopts a dome light source with high uniformity of diffuse reflection; the light source controller 3 is required to output power that meets the requirements of the light source, and has an I / O receiving port, which is used in conjunction with the industrial camera. The light source controller 3 is triggered by the I / O signal of the industrial camera, thereby realizing the synchronous triggering of the industrial camera and the dome light source.

[0043] The industrial computer 4 has a RAM capacity of 32 GB or more, a solid-state storage space of 512 GB or more, and a CPU version of i7-12th or more.

[0044] Among them, the communication speed of the data communication interface, data line, and acquisition card involved in the present invention meets the requirements of high-speed image transmission, requiring the use of a 10 Gigabit network card and related 10 Gigabit network communication cables.

[0045] The present invention applies the dynamic testing method in the aforementioned embodiment to observe the dynamic change process of fabric rebound online and calculate the fabric rebound height, thereby achieving an intuitive evaluation of the fabric rebound performance, simplifying the operation process and improving the accuracy of the test.

[0046] The embodiments of the present invention are described in detail above, but the contents are only preferred embodiments of the present invention and cannot be considered to limit the scope of implementation of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the present invention.

Claims

1. A method for dynamically measuring the rebound height of high-performance fiber fabrics, characterized in that: The following steps are involved: S1. Fabric sample preparation: Place the woven fabric without pressurization in a tooling and place it on a universal tensile testing machine; S2. Fabric compaction test: The fabric is compressed by the constant speed method or constant pressure method until the height of the compressed fabric no longer changes, and then the load is released or the compression load is maintained until it remains unchanged and then the load is released; S3, fabric rebound image acquisition: perform image acquisition of the fabric rebound process after the load is released, and obtain the rebound shape of the fabric at each moment by acquiring each frame of image; S4, image preprocessing: obtain the lossless original image from the image acquisition device, perform filtering and enhancement processing, perform linear smoothing processing on the original grayscale value of the input original image, and obtain the average grayscale value; binarize the original image, use the morphological dilation method to process the binarized image, and obtain the grayscale value image pixels after filtering and enhancement; S5, fabric rebound edge fitting: according to the obtained average gray value, original gray value and filtered enhanced gray value image pixels, the enhanced gray value is calculated to obtain the new image pixel. The formula is as follows: Among them, res: is the new image pixel; round((orig - mean)×Factor) is the gray value image pixel after filtering enhancement; orig is the original gray value; mean is the average gray value; Factor is the factor; round is the rounding symbol; a, b, c are all fitting adjustment coefficients; The nonlinear least square method is used to fit the new image pixels to obtain the pixel points at the rebound edge of the fabric, and the pixel points at the edge are fitted to obtain the fabric edge curve; S6. Fabric rebound data calibration: Use a high-precision calibration plate to calibrate the camera, establish a mapping relationship between the side length of the checkerboard calibration plate and the number of pixels occupied by the corresponding image, and obtain single-pixel accuracy; S7. Characterization and highly quantitative evaluation of fabric rebound performance: Online observation of the dynamic change process of fabric rebound is carried out. Through single-pixel accuracy, the association between the image coordinate system and the actual physical coordinate system is established to quantitatively evaluate the fabric rebound height, thus achieving a comprehensive characterization of fabric rebound.

2. The method for dynamically measuring the rebound height of high-performance fiber fabrics according to claim 1, characterized in that: In step S2, when pressing down, the pressure head starts to move from the original position to compact the fabric; when the load is released, the pressure head moves to the original position at a constant speed.

3. The method for dynamically measuring the rebound height of high-performance fiber fabric according to claim 1, characterized in that: In step S6, the formula for single pixel accuracy is: A=L / NUM Where: A is the single pixel accuracy, mm / pixel; L is the side length of the chessboard calibration plate, mm; NUM is the number of pixels occupied by the corresponding image, pixle.

4. A high-performance fiber fabric rebound height dynamic measurement system, used to implement the high-performance fiber fabric rebound height dynamic measurement method according to any one of claims 1 to 3, characterized in that: It includes an image acquisition device, a light source, a light source controller and an industrial computer. The light source is located on one side of the fabric, is horizontally arranged, and irradiates perpendicularly to the side of the fabric. The light source is connected to the light source controller. The image acquisition device vertically shoots the side of the fabric through the light hole in the center of the light source to acquire the image. The image acquisition device is connected to the industrial computer through a data communication interface.

5. The high-performance fiber fabric rebound height dynamic measurement system according to claim 4 is characterized in that: The image acquisition device is an industrial camera, and the industrial FA high-definition lens image resolution of the industrial camera is greater than or equal to 2500w pixels.

6. The high-performance fiber fabric rebound height dynamic measurement system according to claim 5, characterized in that: The light source adopts a dome light source; the light source controller is used in coordination with an industrial camera; the dome light source is connected to the light source controller to cooperate with the industrial camera for image acquisition, and the light source controller is triggered by the I / O signal of the industrial camera to achieve synchronous triggering of the industrial camera and the dome light source.

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