Fabric air permeability measurement method, device, equipment and storage medium

Abstract

The application belongs to the technical field of fabric performance detection, and discloses a fabric air permeability measurement method, device, equipment and storage medium, the method comprises the following steps: acquiring a no-flow field disturbance background image above a textile fabric and a flow field disturbance image after simulating human body temperature, taking the background gray image corresponding to the no-flow field disturbance background image as a reference image, calculating the flow field displacement graph corresponding to the flow field disturbance image through an optical flow algorithm, calculating the flow field displacement amplitude matrix and the flow field displacement direction matrix, inputting the flow field displacement amplitude matrix and the flow field displacement direction matrix into a relative air permeability intensity quantitative index calculation formula, a relative air permeability coverage quantitative index calculation formula and a dominant air flow direction quantitative index calculation formula respectively, calculating the relative air permeability intensity, the relative air permeability coverage and the dominant air flow direction, so as to determine the air permeability of the textile fabric; through the above method, the air permeability measurement efficiency of the fabric is improved.

Description

Methods, apparatus, equipment and storage media for measuring the air permeability of fabrics Technical Field

[0001] This application relates to the technical field of fabric performance testing, and more specifically, to a method, apparatus, equipment, and storage medium for measuring the air permeability of fabrics. Background Technology

[0002] In the research, development, production and application of textile fabrics, breathability is one of the core indicators for measuring the comfort of wearing fabrics, especially for summer clothing, sportswear, outdoor equipment, etc., as it is directly related to the heat dissipation efficiency, stuffiness and sweat evaporation experience when the human body is wearing it.

[0003] To accurately assess fabric breathability, various testing methods exist in the industry, with the most widely used techniques including pressure difference method, gravimetric method, and heat flow meter method. While these existing methods can quantitatively test fabric breathability, they still have significant technical shortcomings in practical applications, especially in simulating real-world heat dissipation scenarios where the human body is wearing the fabric as a heat source. Specifically, the pressure difference method and contact breathability meters rely on forced airflow (such as fan pressurization), which differs greatly from the environment where body temperature drives natural airflow when wearing fabric, resulting in a low correlation between the measured forced airflow and the actual natural heat dissipation effect. The gravimetric method focuses on moisture transfer rather than direct air permeability and only simulates a static humid environment, failing to reflect the combined heat dissipation process of the human body's own heat and natural airflow. Although the heat flow meter method constructs a temperature difference, the heat source is fixed and there is no natural convection, making it impossible to simulate airflow disturbances during human activity. This leads to a disconnect between the test data and the actual wearing experience (such as the stuffiness during exercise), hindering the development of highly comfortable fabrics.

[0004] In summary, existing mainstream testing methods can only output static values ​​(such as air permeability, moisture transfer rate, and heat flux density), failing to visually represent the airflow state on the fabric surface and in its pores. For example, the pressure difference method can only indicate the overall air permeability of the fabric, but cannot determine whether the airflow is uniform or whether there are localized air leaks or impermeable areas; similarly, the heat flux meter method and the gravimetric method can only provide overall performance data, unable to observe the actual path of heat-driven airflow or moisture flow. This problem of focusing solely on numerical test results while lacking overall fabric visualization makes it difficult for researchers to pinpoint the specific impact of fabric structural design (such as seams, holes, and textures) on air permeability. They can only rely on measured single-dimensional test values ​​for one-sided judgments, thus increasing the trial-and-error costs of fabric optimization and failing to meet the precise, practical, and visual testing requirements for fabric comfort research and development.

[0005] To address the aforementioned issues, existing technologies urgently need improvement. Summary of the Invention

[0006] The purpose of this application is to provide a method, device, equipment, and storage medium for measuring the air permeability of fabrics. Through an optical flow algorithm, combined with preset formulas for calculating flow field displacement amplitude, flow field displacement direction, relative air permeability intensity, relative air permeability coverage, and dominant airflow direction, the relative air permeability intensity, relative air permeability coverage, and dominant airflow direction are calculated to determine the air permeability of textile fabrics. This addresses the problem that existing fabric air permeability testing methods can only output static values ​​and cannot present the airflow state on the fabric surface and in the pores, making it difficult for researchers to pinpoint the specific impact of fabric structure design on air permeability. This method enables a comprehensive and multi-dimensional evaluation of fabric air permeability, allowing researchers to gain a deeper understanding of the specific impact of fabric structure design on air permeability, and improving the efficiency and accuracy of fabric air permeability measurement.

[0007] In a first aspect, this application provides a method for measuring the air permeability of a fabric, including:

[0008] By using a pre-set background schlieren imaging system, a background image without flow field disturbance and a flow field disturbance image after simulating human body temperature are obtained above the textile fabric.

[0009] Using the background grayscale image corresponding to the background image without flow field disturbance as a reference image, the flow field displacement map of the flow field disturbance grayscale image corresponding to the flow field disturbance image is calculated by optical flow algorithm;

[0010] Based on the preset formulas for calculating the amplitude and direction of the flow field displacement, the flow field displacement amplitude matrix and the flow field displacement direction matrix of the flow field displacement diagram are calculated.

[0011] The flow field displacement amplitude matrix and the flow field displacement direction matrix are respectively input into the preset relative permeability intensity quantification index calculation formula, the preset relative permeability coverage rate quantification index calculation formula and the preset dominant airflow direction quantification index calculation formula to calculate the relative permeability intensity, relative permeability coverage rate and dominant airflow direction of the flow field displacement map.

[0012] The air permeability of the textile fabric is determined based on the relative air permeability intensity, the relative air permeability coverage, and the dominant airflow direction.

[0013] The fabric breathability measurement method provided in this application enables the measurement of the breathability of textile fabrics. Through an optical flow algorithm, combined with preset formulas for calculating flow field displacement amplitude, flow field displacement direction, relative breathability intensity, relative breathability coverage, and dominant airflow direction, the relative breathability intensity, relative breathability coverage, and dominant airflow direction are calculated to determine the breathability of the textile fabric. This method addresses the problem that existing fabric breathability testing methods can only output static values ​​and cannot present the airflow state on the fabric surface and in the pores, making it difficult for researchers to pinpoint the specific impact of fabric structure design on breathability. It enables a comprehensive and multi-dimensional evaluation of fabric breathability, allowing researchers to gain a deeper understanding of the specific impact of fabric structure design on breathability, thus improving the efficiency and accuracy of fabric breathability measurement.

[0014] Optionally, the background schlieren imaging system includes an airflow isolation hood, and a background plate, a light source, an imaging camera, a bionic heat source, and a textile fabric disposed inside the airflow isolation hood; the light source is attached to the background plate and placed on the back of the background plate; the background plate faces the imaging camera, and the background plate and the imaging camera are on the same horizontal line; the bionic heat source is disposed on the back of the textile fabric, and the textile fabric is placed face up on the inner bottom surface of the airflow isolation hood between the background plate and the imaging camera, so that the imaging camera can capture the airflow disturbance above the textile fabric.

[0015] The fabric breathability measurement method provided in this application can measure the breathability of textile fabrics. It effectively avoids external airflow interference through an airflow isolation hood, and at the same time, the biomimetic heat source simulates human body heating, enabling the schlieren imaging system to accurately capture the weak airflow disturbances caused by fabric breathability, providing high-quality raw data for subsequent image processing and performance evaluation.

[0016] Optionally, using the background grayscale image corresponding to the background image without flow field disturbance as a reference image, an optical flow algorithm is used to calculate the real-time flow field displacement map corresponding to the flow field disturbance grayscale image, including:

[0017] The background image without flow field disturbance and the image with flow field disturbance are processed into grayscale to obtain the background grayscale image corresponding to the background image without flow field disturbance and the flow field disturbance grayscale image corresponding to the image with flow field disturbance.

[0018] Using the optical flow algorithm, with the background grayscale image as a reference image, the two-dimensional vector field tensor of the flow field disturbance grayscale image is calculated to obtain the flow field displacement map corresponding to the flow field disturbance grayscale image.

[0019] Optionally, the flow field displacement amplitude matrix and flow field displacement direction matrix of the flow field displacement diagram are calculated according to preset flow field displacement amplitude calculation formulas and preset flow field displacement direction calculation formulas, including:

[0020] The two-dimensional vector field tensor in the flow field displacement diagram is input into the preset flow field displacement amplitude calculation formula to calculate the flow field displacement amplitude matrix of the flow field displacement diagram.

[0021] The two-dimensional vector field tensor in the flow field displacement diagram is input into a preset flow field displacement direction calculation formula to calculate the flow field displacement direction matrix of the flow field displacement diagram.

[0022] Optionally, after calculating the flow field displacement amplitude matrix and flow field displacement direction matrix of the flow field displacement diagram according to the preset flow field displacement amplitude calculation formula and the preset flow field displacement direction calculation formula, the method further includes:

[0023] Using the flow field displacement amplitude matrix as the hue and the flow field displacement direction matrix as the brightness, combined with a fixed saturation, and following a preset mapping rule, a visualized flow field displacement map corresponding to the flow field displacement map is calculated to visualize the airflow state of the flow field displacement map.

[0024] Optionally, the flow field displacement amplitude matrix and the flow field displacement direction matrix are respectively input into preset formulas for calculating relative permeability intensity, relative permeability coverage, and dominant airflow direction, to calculate the relative permeability intensity, relative permeability coverage, and dominant airflow direction of the flow field displacement map, including:

[0025] A statistically robust filtering method based on the absolute deviation of the median is used to filter out outliers in the flow field displacement amplitude matrix and the flow field displacement direction matrix, resulting in filtered flow field displacement amplitude matrix and filtered flow field displacement direction matrix.

[0026] The filtered flow field displacement amplitude matrix is ​​input into the preset relative air permeability intensity quantification index calculation formula to calculate the relative air permeability intensity of the flow field displacement map.

[0027] The filtered flow field displacement amplitude matrix is ​​input into the preset relative air permeability coverage index calculation formula to calculate the relative air permeability coverage of the flow field displacement map.

[0028] The filtered flow field displacement direction matrix is ​​input into the preset formula for calculating the dominant airflow direction quantification index to calculate the dominant airflow direction of the flow field displacement map.

[0029] The fabric air permeability measurement method provided in this application can measure the air permeability of textile fabrics. By using a statistically robust filtering method based on the median absolute deviation, outliers in the flow field displacement data are effectively removed, ensuring the accuracy and reliability of subsequent quantitative index calculations, thereby improving the precision of fabric air permeability evaluation.

[0030] Optionally, a statistically robust filtering method based on the absolute deviation of the median is used to filter out outliers in the flow field displacement amplitude matrix and the flow field displacement direction matrix, resulting in filtered flow field displacement amplitude matrix and filtered flow field displacement direction matrix, including:

[0031] The median of the flow field displacement amplitude of all flow field displacement amplitudes in the flow field displacement amplitude matrix is ​​calculated to obtain the set of deviation vectors between all the flow field displacement amplitudes and the median of the flow field displacement amplitude.

[0032] Extract the median of the deviation vectors from the set of deviation vectors to determine the robust threshold;

[0033] Based on the robust threshold and the median of the flow field displacement amplitude, outlier filtering is performed on the flow field displacement amplitude matrix and the flow field displacement direction matrix to obtain the filtered flow field displacement amplitude matrix and the filtered flow field displacement direction moment.

[0034] Secondly, this application provides a fabric breathability measurement device, comprising:

[0035] The acquisition module is used to acquire a background image without flow field disturbance above the textile fabric and a flow field disturbance image after simulating human body temperature through a pre-set background schlieren imaging system.

[0036] The first calculation module is used to calculate the flow field displacement map of the flow field disturbance grayscale image corresponding to the flow field disturbance image using an optical flow algorithm, with the background grayscale image corresponding to the background image without flow field disturbance as a reference image.

[0037] The second calculation module is used to calculate the flow field displacement amplitude matrix and the flow field displacement direction matrix of the flow field displacement diagram according to the preset flow field displacement amplitude calculation formula and the preset flow field displacement direction calculation formula.

[0038] The third calculation module is used to input the flow field displacement amplitude matrix and the flow field displacement direction matrix into the preset relative permeability intensity quantification index calculation formula, the preset relative permeability coverage rate quantification index calculation formula and the preset dominant airflow direction quantification index calculation formula, respectively, to calculate the relative permeability intensity, relative permeability coverage rate and dominant airflow direction of the flow field displacement map.

[0039] The determining module is used to determine the air permeability of the textile fabric based on the relative air permeability intensity, the relative air permeability coverage, and the dominant airflow direction.

[0040] This fabric breathability measurement device uses an optical flow algorithm, combined with preset formulas for calculating flow field displacement amplitude, flow field displacement direction, relative breathability intensity, relative breathability coverage, and dominant airflow direction, to calculate relative breathability intensity, relative breathability coverage, and dominant airflow direction. This allows for the determination of the breathability performance of textile fabrics. It addresses the problem that existing fabric breathability testing methods only output static values ​​and cannot represent the airflow state on the fabric surface and in the pores, making it difficult for researchers to pinpoint the specific impact of fabric structure design on breathability. This device provides a comprehensive and multi-dimensional assessment of fabric breathability, enabling researchers to gain a deeper understanding of the specific influence of fabric structure design on breathability, thus improving the efficiency and accuracy of fabric breathability measurement.

[0041] Thirdly, this application provides an electronic device including a processor and a memory, the memory storing a computer program executable by the processor, wherein when the processor executes the computer program, it performs the steps in the fabric breathability measurement method described above.

[0042] Fourthly, this application provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, performs the steps of the fabric breathability measurement method described above.

[0043] Beneficial Effects: The fabric breathability measurement method, device, equipment, and storage medium provided in this application, through optical flow algorithm, combined with preset formulas for calculating flow field displacement amplitude, flow field displacement direction, relative breathability intensity quantification index, relative breathability coverage quantification index, and dominant airflow direction, calculates relative breathability intensity, relative breathability coverage, and dominant airflow direction to determine the breathability performance of textile fabrics. This solves the problem that existing fabric breathability testing methods can only output static values ​​and cannot present the airflow state on the fabric surface and in the pores, making it difficult for researchers to locate the specific impact of fabric structure design on breathability. It can comprehensively and multidimensionally evaluate the breathability performance of fabrics, enabling researchers to more deeply understand the specific impact of fabric structure design on breathability, and improving the efficiency and accuracy of fabric breathability measurement. Attached Figure Description

[0044] Figure 1 is a flowchart of the fabric breathability measurement method provided in the embodiments of this application.

[0045] Figure 2 is a schematic diagram of the fabric breathability measurement device provided in the embodiment of this application.

[0046] Figure 3 is a schematic diagram of the structure of the electronic device provided in the embodiment of this application.

[0047] Figure 4 is a schematic diagram of the background schlieren imaging system.

[0048] Figure 5 is a grayscale image of the background.

[0049] Figure 6 is a grayscale image of the flow field disturbance.

[0050] Figure 7 shows the flow field displacement diagram corresponding to the grayscale image of the flow field disturbance.

[0051] Figure 8 shows the flow field displacement diagram in the horizontal axis direction after slicing the flow field displacement diagram in the horizontal axis direction.

[0052] Figure 9 shows the flow field displacement diagram along the vertical axis after slicing the flow field displacement diagram along the vertical axis.

[0053] Labeling Explanation: 1. Acquisition Module; 2. First Calculation Module; 3. Second Calculation Module; 4. Third Calculation Module; 5. Determination Module; 11. Airflow Isolation Hood; 12. Background Plate; 13. Light Source; 14. Imaging Camera; 15. Textile Fabric; 301. Processor; 302. Memory; 303. Communication Bus. Detailed Implementation

[0054] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0055] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this application, terms such as "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0056] Please refer to Figure 1, which illustrates a method for measuring the air permeability of a fabric in some embodiments of this application. This method is used to measure the air permeability of textile fabrics and includes the following steps:

[0057] Step S101: Using a pre-set background schlieren imaging system, acquire a background image without flow field disturbance above the textile fabric and a flow field disturbance image after simulating human body temperature.

[0058] Step S102: Using the background grayscale image corresponding to the background image without flow field disturbance as a reference image, the flow field displacement map of the flow field disturbance grayscale image corresponding to the flow field disturbance image is calculated by optical flow algorithm.

[0059] Step S103: Calculate the flow field displacement amplitude matrix and flow field displacement direction matrix of the flow field displacement diagram according to the preset flow field displacement amplitude calculation formula and the preset flow field displacement direction calculation formula.

[0060] Step S104: Input the flow field displacement amplitude matrix and flow field displacement direction matrix into the preset relative permeability intensity quantification index calculation formula, the preset relative permeability coverage rate quantification index calculation formula and the preset dominant airflow direction quantification index calculation formula respectively, and calculate the relative permeability intensity, relative permeability coverage rate and dominant airflow direction of the flow field displacement map.

[0061] Step S105: Based on relative air permeability intensity, relative air permeability coverage and dominant airflow direction, determine the air permeability performance of the textile fabric.

[0062] This method for measuring fabric breathability uses an optical flow algorithm, combined with preset formulas for calculating flow field displacement amplitude, flow field displacement direction, relative breathability intensity, relative breathability coverage, and dominant airflow direction, to calculate relative breathability intensity, relative breathability coverage, and dominant airflow direction. This allows for the determination of the fabric's breathability performance. It addresses the problem of existing fabric breathability testing methods that only output static values ​​and fail to represent the airflow patterns on the fabric surface and in the pores, making it difficult for researchers to pinpoint the specific impact of fabric structure design on breathability. This new method provides a comprehensive and multi-dimensional assessment of fabric breathability, enabling researchers to gain a deeper understanding of the specific influence of fabric structure design on breathability and improving the efficiency and accuracy of fabric breathability measurement.

[0063] Specifically, in step S101, a background image without flow field disturbance and a flow field disturbance image after simulating human body temperature are acquired by a pre-set background schlieren imaging system. The background image without flow field disturbance refers to the gas flow diagram above the textile fabric captured by the background schlieren imaging system when the textile fabric is at room temperature or the same as the ambient temperature and there is no external airflow interference. The flow field disturbance image refers to the gas flow diagram above the textile fabric when the textile fabric is at human body temperature, captured by the background schlieren imaging system, by placing a heating device (such as a biomimetic heat source) on the back of the textile fabric to simulate human body temperature and generating natural convection airflow above the textile fabric.

[0064] The background schlieren imaging system is an optical imaging system. Its core principle is to utilize the phenomenon that light is deflected when passing through a flow field with different refractive index gradients, converting density changes in the flow field into grayscale or brightness changes in the image, thereby achieving visualization of transparent flow fields. Therefore, this background schlieren imaging system can be used to capture airflow disturbances caused by temperature differences above textile fabrics. As shown in Figure 4, the background schlieren imaging system specifically includes an airflow isolation hood 11, and a background plate 12, a light source 13, an imaging camera 14, a biomimetic heat source, and a textile fabric 15 disposed inside the airflow isolation hood. The airflow isolation hood 11 provides a closed and stable environment for the schlieren imaging process, effectively isolating external airflow disturbances and ensuring that, during image acquisition, flow field changes are caused only by the interaction between the biomimetic heat source and the textile fabric. The light source 13 is attached to the background plate 12 and placed on the back of the background plate 12, thereby providing uniform backlight illumination to the background plate 12, making the refractive index changes of the flow field more uniform. The imaging camera 14 is positioned directly opposite the background plate 12, and the two are on the same horizontal line, ensuring that the imaging camera 14 can capture the schlieren changes on the background plate 12 from the best angle, thereby obtaining a high-quality background image and flow field disturbance image. The biomimetic heat source is set on the back of the textile fabric 15, and its function is to simulate human body temperature to generate hot airflow, which causes the airflow to pass through the textile fabric 15 and form the flow field disturbance to be measured. The textile fabric 15 is placed face up on the inner bottom surface of the airflow isolation cover 11 between the background plate 12 and the imaging camera 14, so that the imaging camera 14 can capture the airflow disturbance above the textile fabric 15.

[0065] Specifically, in step S102, using the background grayscale image corresponding to the background image without flow field disturbance as a reference image, the flow field displacement map of the flow field disturbance grayscale image corresponding to the flow field disturbance image is calculated using an optical flow algorithm, including:

[0066] Grayscale processing was performed on the background image without flow field disturbance and the image with flow field disturbance respectively to obtain the background grayscale image corresponding to the background image without flow field disturbance and the flow field disturbance grayscale image corresponding to the image with flow field disturbance.

[0067] Using the optical flow algorithm, with the background grayscale image as a reference image, the two-dimensional vector field tensor of the flow field disturbance grayscale image is calculated to obtain the flow field displacement map corresponding to the flow field disturbance grayscale image.

[0068] In step S102, using existing grayscale processing algorithms, such as the weighted average method, the color information of the three color channels in the background image without flow field disturbance and the image with flow field disturbance are combined into a single brightness value to generate a grayscale image, resulting in the background grayscale image corresponding to the background image without flow field disturbance (as shown in Figure 5) and the flow field disturbance grayscale image corresponding to the image with flow field disturbance (as shown in Figure 6).

[0069] Optical flow algorithms are an existing technique for estimating the motion of objects in image sequences. Using optical flow algorithms (such as the Lucas-Kanade algorithm, Dense Inverse Search algorithm, Farneback algorithm, Horn-Schunck algorithm, Dual TV-L1 algorithm, or DeepFlow algorithm), the displacement vector of each pixel in the perturbed image relative to the corresponding pixel in the background image without perturbed flow is calculated (i.e., the two-dimensional vector field tensor of the perturbed grayscale image relative to the background image without perturbed flow). This yields the flow field displacement map corresponding to the perturbed grayscale image (as shown in Figures 7, 8, and 9). Figure 7 shows the flow field displacement map corresponding to the perturbed grayscale image, from which the displacement vector of the pixels under flow perturbed flow can be observed. Figure 8 shows the flow field displacement map after slicing along the horizontal axis. The flow field displacement map in the horizontal direction (i.e., the flow field displacement map containing only the displacement vector in the horizontal direction) shows the displacement vector of the pixel in the horizontal direction under flow field disturbance. Figure 9 shows the flow field displacement map in the vertical direction after slicing the flow field displacement map in the vertical direction (i.e., the flow field displacement map containing only the displacement vector in the vertical direction), which shows the displacement vector of the pixel in the vertical direction under flow field disturbance. This is to accurately capture the minute displacements of airflow disturbances caused by the breathability of textile fabrics on the image, providing basic data for subsequent quantification of breathability performance. The optical flow algorithm is an existing technology and will not be described in detail here.

[0070] Specifically, in step S103, the flow field displacement amplitude matrix and flow field displacement direction matrix of the flow field displacement diagram are calculated according to the preset flow field displacement amplitude calculation formula and the preset flow field displacement direction calculation formula, including:

[0071] The two-dimensional vector field tensor in the flow field displacement diagram is input into the preset flow field displacement amplitude calculation formula to calculate the flow field displacement amplitude matrix of the flow field displacement diagram.

[0072] The two-dimensional vector field tensor in the flow field displacement diagram is input into the preset flow field displacement direction calculation formula to calculate the flow field displacement direction matrix of the flow field displacement diagram.

[0073] In step S103, after the flow field displacement map is calculated using the optical flow algorithm, this flow field displacement map is typically represented in the form of a two-dimensional vector field tensor. By inputting the two-dimensional vector field tensor into a preset flow field displacement amplitude calculation formula, the length of each displacement vector is extracted to form a flow field displacement amplitude matrix. Similarly, by inputting the two-dimensional vector field tensor into a preset flow field displacement direction calculation formula, the direction information of each displacement vector is extracted to form a flow field displacement direction matrix.

[0074] The specific formula for calculating the amplitude of the pre-set flow field displacement is as follows:

[0075] ;

[0076] in, Location point The amplitude of the flow field displacement; Location point Two-dimensional vector field tensor in the horizontal axis direction; Location point The two-dimensional vector field tensor along the vertical axis; H is the height of the flow field displacement map; W is the width of the flow field displacement map; i is the location point. The x-coordinate, j is the position point. The ordinate.

[0077] The preset formula for calculating the flow field displacement direction is as follows:

[0078] ;

[0079] ;

[0080] in, Location point Intermediate values ​​for calculating the direction of displacement in the flow field; Let be the arctangent function of two variables, which is defined as: , This is an undefined variable (meaning it is a variable but has not been assigned a value). Location point The direction value of the flow field displacement (i.e., the location point) The corresponding two-dimensional vector field tensor and the deflection angle formed by the positive direction of the horizontal axis). The range is .

[0081] Specifically, after calculating the flow field displacement amplitude matrix and flow field displacement direction matrix of the flow field displacement diagram according to the preset flow field displacement amplitude calculation formula and the preset flow field displacement direction calculation formula, the process also includes:

[0082] Using the flow field displacement amplitude matrix as the hue and the flow field displacement direction matrix as the brightness, combined with a fixed saturation, and following a preset mapping rule, a visualized flow field displacement map corresponding to the flow field displacement map is calculated to visualize the airflow state of the flow field displacement map.

[0083] After calculating the flow field displacement amplitude matrix and the flow field displacement direction matrix of the flow field displacement diagram, normalization processing (such as Min-Max normalization) is first applied to these matrices to obtain the normalized flow field displacement amplitude matrix and the normalized flow field displacement direction matrix. The normalization process is existing technology and will not be described in detail here.

[0084] The normalized flow field displacement amplitude matrix is ​​mapped to the hue of the visualized flow field displacement map, assigning different colors to different airflow intensities. Simultaneously, the normalized flow field displacement direction matrix is ​​mapped to the value of the visualized flow field displacement map, using color variations to represent changes in airflow direction. Furthermore, saturation is set to a fixed value to ensure that hue and value clearly and without interference express the amplitude and direction information of the airflow. Following preset mapping rules, a visualized flow field displacement map (i.e., a colorized flow field displacement map) is generated, achieving intuitive visualization of the airflow state. It can present the airflow state above the textile fabric using easily recognizable color and brightness variations. For example, by observing the color distribution of the visualized flow field displacement map, areas with high and low airflow intensity can be quickly identified; by observing color variations, the main flow direction can be determined.

[0085] The preset mapping rules are as follows:

[0086] (1) Create a three-dimensional HSV color space matrix of the same size as the background image without flow field disturbance. , dimension ,Will The elements are initially assigned a value of 0, that is... The hue channel in Saturation channel and brightness channel The value is assigned to 0.

[0087] (2) Three-dimensional matrix tone channels Color information is represented by the following formula:

[0088] ;

[0089] in, Location point The hue channel value; This is a rounding function; The position points after normalization. The amplitude of the flow field displacement; For the hue channel threshold, take =180, which can be adjusted according to actual needs.

[0090] (3) Three-dimensional matrix saturation channel Color purity is represented by the following formula:

[0091] ;

[0092] in, Location point saturation channel value; Saturation channel threshold, saturation channel threshold For a fixed value, take =255, which is the saturation channel threshold. Set to maximum saturation. Maximum saturation ensures vibrant colors and avoids blurry colors caused by insufficient saturation, thus enhancing the recognizability of flow field displacement direction information.

[0093] (4) Three-dimensional matrix Brightness channel The brightness of a color is represented by the following formula:

[0094] ;

[0095] in, Location point The brightness channel value; The position points after normalization. The displacement direction value of the flow field.

[0096] Through the aforementioned mapping rules, different flow field displacement directions correspond to different hues. During continuous changes, the hue transitions smoothly without visual abrupt changes. Furthermore, the larger the flow field displacement amplitude, the brighter the image, intuitively reflecting intensity differences. This mapping method establishes a correspondence between flow field displacement direction and amplitude data and HSV color space channel characteristics. Through dual-dimensional encoding of hue and brightness, both direction and amplitude can be presented simultaneously, avoiding information fragmentation.

[0097] Specifically, in step S104, the flow field displacement amplitude matrix and flow field displacement direction matrix are respectively input into preset relative permeability intensity quantification index calculation formulas, preset relative permeability coverage rate quantification index calculation formulas, and preset dominant airflow direction quantification index calculation formulas to calculate the relative permeability intensity, relative permeability coverage rate, and dominant airflow direction of the flow field displacement map, including:

[0098] A statistically robust filtering method based on the absolute deviation of the median is used to filter out outliers in the flow field displacement amplitude matrix and the flow field displacement direction matrix, resulting in the filtered flow field displacement amplitude matrix and the filtered flow field displacement direction matrix.

[0099] The filtered flow field displacement amplitude matrix is ​​input into the preset relative permeability intensity quantification index calculation formula to calculate the relative permeability intensity of the flow field displacement map.

[0100] The filtered flow field displacement amplitude matrix is ​​input into the preset relative air permeability coverage index calculation formula to calculate the relative air permeability coverage of the flow field displacement map.

[0101] The filtered flow field displacement direction matrix is ​​input into the preset formula for calculating the dominant airflow direction quantification index to calculate the dominant airflow direction of the flow field displacement map.

[0102] Specifically, in step S104, a statistically robust filtering method based on the absolute deviation of the median is used to filter out outliers in the flow field displacement amplitude matrix and the flow field displacement direction matrix, resulting in the filtered flow field displacement amplitude matrix and the filtered flow field displacement direction matrix, including:

[0103] Calculate the median of all flow field displacement amplitudes in the flow field displacement amplitude matrix, and use it to calculate the set of deviation vectors between all flow field displacement amplitudes and the median of the flow field displacement amplitudes;

[0104] Extract the median of the deviation vectors from the set of deviation vectors to determine the robust threshold;

[0105] Based on a robust threshold and the median of the flow field displacement amplitude, outlier filtering is performed on the flow field displacement amplitude matrix and the flow field displacement direction matrix to obtain the filtered flow field displacement amplitude matrix and the filtered flow field displacement direction moment.

[0106] In step S104, after sorting all the flow field displacement amplitudes in the flow field displacement amplitude matrix, the value located in the middle position is extracted to obtain the median of the flow field displacement amplitude. The absolute value of the difference between each flow field displacement amplitude and the aforementioned median flow field displacement amplitude (i.e., the deviation vector) is calculated to construct a set of deviation vectors. Through the set of deviation vectors, the degree to which each data point deviates from the central trend can be quantified.

[0107] The median is calculated again from the above set of deviation vectors. The median of the deviation vectors is used to determine the robustness threshold. The robustness threshold is calculated as follows:

[0108] ;

[0109] in, A robust threshold; Set a coefficient for the robustness threshold, typically set to 3, but can be adjusted as needed. This is the median of the deviation vector.

[0110] For any flow field displacement amplitude, if it is greater than the difference between the median flow field displacement amplitude and the robust threshold, and less than the sum of the median flow field displacement amplitude and the robust threshold, it is determined to be a normal value; otherwise, if any flow field displacement amplitude is less than or equal to the difference between the median flow field displacement amplitude and the robust threshold, or if any flow field displacement amplitude is greater than or equal to the sum of the median flow field displacement amplitude and the robust threshold, it is determined to be an outlier. When a flow field displacement amplitude is identified as a normal value, there is no need to adjust its corresponding flow field displacement amplitude and direction values. When a flow field displacement amplitude is identified as an outlier, its corresponding flow field displacement amplitude and direction values ​​will be filtered out, thus obtaining the filtered flow field displacement amplitude matrix and the filtered flow field displacement direction matrix.

[0111] The calculation process for outlier filtering is as follows:

[0112] ;

[0113] in, The filtered flow field displacement amplitude. The value represents the direction of displacement in the filtered flow field. This represents the median of the flow field displacement amplitude.

[0114] In step S104, the filtered flow field displacement amplitude matrix is ​​input into the preset relative permeability intensity quantification index calculation formula to calculate the relative permeability intensity of the flow field displacement map. The filtered flow field displacement amplitude matrix is ​​input into the preset relative permeability coverage quantification index calculation formula to calculate the relative permeability coverage of the flow field displacement map. The filtered flow field displacement direction matrix is ​​input into the preset dominant airflow direction quantification index calculation formula to calculate the dominant airflow direction of the flow field displacement map.

[0115] The specific formula for calculating the preset relative air permeability index is as follows:

[0116] ;

[0117] in, Relative air permeability strength Characterizing the contrast between air permeability and breathability, this quantifies the relative intensity of airflow in a fabric. The stronger the airflow, the greater the relative air permeability. The higher the value, the better the breathability and heat dissipation performance of the fabric.

[0118] The pre-defined formula for calculating the relative breathability coverage rate is as follows:

[0119] ;

[0120] in, This refers to the relative breathability coverage. For the filtered flow field displacement amplitude matrix to satisfy the condition that the absolute value is greater than the air permeability coverage intensity threshold. The number of elements, the air permeability coverage intensity threshold It can be set according to actual needs. Relative breathability coverage. This reflects the relative size of the breathable area of ​​the fabric; the more breathable pores and the wider the distribution of disturbed airflow, the higher the relative breathable coverage. The higher the value, the better the breathability and heat dissipation performance of the fabric.

[0121] The specific formula for calculating the pre-defined dominant airflow direction quantification index is as follows:

[0122] ;

[0123] in, The dominant airflow direction; To be The width of each interval after dividing the text into multiple equal intervals, i.e. K is the total number of intervals. K can be set according to actual needs, and is generally set to 72. This represents the maximum number of elements in each interval (i.e., the number of filtered flow field displacement direction values) when the filtered flow field displacement direction matrix falls into multiple intervals. ), The `argmax` function is used to find the set of arguments that maximizes the objective function. This is the histogram corresponding to the displacement direction matrix of the filtered flow field. , It is a quantity function. For the k-th interval, This is the displacement direction matrix of the filtered flow field. The element located in the k-th interval of the filtered flow field displacement direction matrix (i.e., the filtered flow field displacement direction value); the dominant airflow direction. It reflects the direction of airflow movement that occurs most frequently in the breathable area of ​​the fabric, which helps researchers analyze the influence of fabric weaving patterns, seams, pores, etc. on the deviation of breathable airflow.

[0124] Specifically, in step S105, based on the relative air permeability... Relative breathability coverage and the direction of the dominant airflow By combining preset evaluation criteria, the air permeability performance of textile fabrics is comprehensively judged. For example, different thresholds can be set experimentally to distinguish air permeability levels such as "high air permeability," "medium air permeability," and "low air permeability," based on relative air permeability intensity. Relative breathability coverage and the direction of the dominant airflow The air permeability score of the textile fabric is calculated by comprehensive methods (such as weighted average method), and the air permeability of the textile fabric is determined by the threshold range in which the air permeability score is located.

[0125] As can be seen from the above, the method for measuring the breathability of this fabric acquires a background image without flow field disturbance and a flow field disturbance image simulated by human body temperature above the textile fabric through a pre-set background schlieren imaging system. Using the background grayscale image corresponding to the background image without flow field disturbance as a reference image, the flow field displacement map of the flow field disturbance grayscale image corresponding to the flow field disturbance image is calculated through an optical flow algorithm. According to the preset flow field displacement amplitude calculation formula and the preset flow field displacement direction calculation formula, the flow field displacement amplitude matrix and the flow field displacement direction matrix of the flow field displacement map are calculated. The flow field displacement amplitude matrix and the flow field displacement direction matrix are input into the preset relative breathability intensity quantification index calculation formula, the preset relative breathability coverage index calculation formula, and the preset dominant airflow direction quantification index calculation formula, respectively, to calculate the relative breathability intensity, relative breathability coverage, and dominant airflow direction of the flow field displacement map. Based on the relative breathability intensity, The relative air permeability coverage and dominant airflow direction are used to determine the air permeability performance of textile fabrics. Then, using an optical flow algorithm, combined with preset formulas for calculating flow field displacement amplitude, flow field displacement direction, relative air permeability intensity, relative air permeability coverage, and dominant airflow direction, the relative air permeability intensity, relative air permeability coverage, and dominant airflow direction are calculated to determine the air permeability performance of the textile fabric. This solves the problem that existing fabric air permeability testing methods can only output static values ​​and cannot present the airflow state on the fabric surface and in the pores, making it difficult for researchers to pinpoint the specific impact of fabric structure design on air permeability. This method enables a comprehensive and multi-dimensional evaluation of fabric air permeability performance, allowing researchers to gain a deeper understanding of the specific impact of fabric structure design on air permeability, and improving the efficiency and accuracy of fabric air permeability measurement.

[0126] Referring to Figure 2, this application provides a fabric air permeability measuring device for measuring the air permeability of textile fabrics, including:

[0127] The acquisition module 1 is used to acquire a background image without flow field disturbance above the textile fabric and a flow field disturbance image after simulating human body temperature through a pre-set background schlieren imaging system.

[0128] The first calculation module 2 is used to calculate the flow field displacement map of the flow field disturbance grayscale image corresponding to the flow field disturbance image through optical flow algorithm, using the background grayscale image corresponding to the background image without flow field disturbance as a reference image.

[0129] The second calculation module 3 is used to calculate the flow field displacement amplitude matrix and the flow field displacement direction matrix of the flow field displacement diagram according to the preset flow field displacement amplitude calculation formula and the preset flow field displacement direction calculation formula.

[0130] The third calculation module 4 is used to input the flow field displacement amplitude matrix and the flow field displacement direction matrix into the preset relative permeability intensity quantification index calculation formula, the preset relative permeability coverage rate quantification index calculation formula and the preset dominant airflow direction quantification index calculation formula, respectively, and calculate the relative permeability intensity, relative permeability coverage rate and dominant airflow direction of the flow field displacement map.

[0131] Module 5 is used to determine the air permeability of the obtained textile fabric based on the relative air permeability intensity, relative air permeability coverage, and dominant airflow direction.

[0132] This fabric breathability measurement device uses an optical flow algorithm, combined with preset formulas for calculating flow field displacement amplitude, flow field displacement direction, relative breathability intensity, relative breathability coverage, and dominant airflow direction, to calculate relative breathability intensity, relative breathability coverage, and dominant airflow direction. This allows for the determination of the breathability performance of textile fabrics. It addresses the problem that existing fabric breathability testing methods only output static values ​​and cannot represent the airflow state on the fabric surface and in the pores, making it difficult for researchers to pinpoint the specific impact of fabric structure design on breathability. This device provides a comprehensive and multi-dimensional assessment of fabric breathability, enabling researchers to gain a deeper understanding of the specific influence of fabric structure design on breathability, thus improving the efficiency and accuracy of fabric breathability measurement.

[0133] Specifically, when module 1 is executed, it acquires a background image without flow field disturbance and a flow field disturbance image after simulating human body temperature through a pre-set background schlieren imaging system. The background image without flow field disturbance refers to the gas flow diagram above the textile fabric captured by the background schlieren imaging system when the textile fabric is at room temperature or the same as the ambient temperature and there is no external airflow interference. The flow field disturbance image refers to the gas flow diagram above the textile fabric when the textile fabric is at human body temperature, captured by the background schlieren imaging system, after a heating device (such as a biomimetic heat source) is placed on the back of the textile fabric to simulate human body temperature, so that natural convection airflow is generated above the textile fabric.

[0134] The background schlieren imaging system is an optical imaging system. Its core principle is to utilize the phenomenon that light is deflected when passing through a flow field with different refractive index gradients, converting density changes in the flow field into grayscale or brightness changes in the image, thereby achieving visualization of transparent flow fields. Therefore, this background schlieren imaging system can be used to capture airflow disturbances caused by temperature differences above textile fabrics. As shown in Figure 4, the background schlieren imaging system specifically includes an airflow isolation hood 11, and a background plate 12, a light source 13, an imaging camera 14, a biomimetic heat source, and a textile fabric 15 disposed inside the airflow isolation hood. The airflow isolation hood 11 provides a closed and stable environment for the schlieren imaging process, effectively isolating external airflow disturbances and ensuring that, during image acquisition, flow field changes are caused only by the interaction between the biomimetic heat source and the textile fabric. The light source 13 is attached to the background plate 12 and placed on the back of the background plate 12, thereby providing uniform backlight illumination to the background plate 12, making the refractive index changes of the flow field more uniform. The imaging camera 14 is positioned directly opposite the background plate 12, and the two are on the same horizontal line, ensuring that the imaging camera 14 can capture the schlieren changes on the background plate 12 from the best angle, thereby obtaining a high-quality background image and flow field disturbance image. The biomimetic heat source is set on the back of the textile fabric 15, and its function is to simulate human body temperature to generate hot airflow, which causes the airflow to pass through the textile fabric 15 and form the flow field disturbance to be measured. The textile fabric 15 is placed face up on the inner bottom surface of the airflow isolation cover 11 between the background plate 12 and the imaging camera 14, so that the imaging camera 14 can capture the airflow disturbance above the textile fabric 15.

[0135] Specifically, when the first calculation module 2 calculates the flow field displacement map of the flow field disturbance grayscale image corresponding to the flow field disturbance image using the optical flow algorithm, with the background grayscale image corresponding to the background image without flow field disturbance as the reference image, it performs the following:

[0136] Grayscale processing was performed on the background image without flow field disturbance and the image with flow field disturbance respectively to obtain the background grayscale image corresponding to the background image without flow field disturbance and the flow field disturbance grayscale image corresponding to the image with flow field disturbance.

[0137] Using the optical flow algorithm, with the background grayscale image as a reference image, the two-dimensional vector field tensor of the flow field disturbance grayscale image is calculated to obtain the flow field displacement map corresponding to the flow field disturbance grayscale image.

[0138] When the first calculation module 2 is executed, it uses existing grayscale processing algorithms, such as the weighted average method, to merge the color information of the three color channels in the background image without flow field disturbance and the image with flow field disturbance into a single brightness value to generate grayscale images, thus obtaining the background grayscale image corresponding to the background image without flow field disturbance (as shown in Figure 5) and the flow field disturbance grayscale image corresponding to the image with flow field disturbance (as shown in Figure 6).

[0139] Optical flow algorithms are an existing technique for estimating the motion of objects in image sequences. Using optical flow algorithms (such as the Lucas-Kanade algorithm, Dense Inverse Search algorithm, Farneback algorithm, Horn-Schunck algorithm, Dual TV-L1 algorithm, or DeepFlow algorithm), the displacement vector of each pixel in the perturbed image relative to the corresponding pixel in the background image without perturbed flow is calculated (i.e., the two-dimensional vector field tensor of the perturbed grayscale image relative to the background image without perturbed flow). This yields the flow field displacement map corresponding to the perturbed grayscale image (as shown in Figures 7, 8, and 9). Figure 7 shows the flow field displacement map corresponding to the perturbed grayscale image, from which the displacement vector of the pixels under flow perturbed flow can be observed. Figure 8 shows the flow field displacement map after slicing along the horizontal axis. The flow field displacement map in the horizontal direction (i.e., the flow field displacement map containing only the displacement vector in the horizontal direction) shows the displacement vector of the pixel in the horizontal direction under flow field disturbance. Figure 9 shows the flow field displacement map in the vertical direction after slicing the flow field displacement map in the vertical direction (i.e., the flow field displacement map containing only the displacement vector in the vertical direction), which shows the displacement vector of the pixel in the vertical direction under flow field disturbance. This is to accurately capture the minute displacements of airflow disturbances caused by the breathability of textile fabrics on the image, providing basic data for subsequent quantification of breathability performance. The optical flow algorithm is an existing technology and will not be described in detail here.

[0140] Specifically, when the second calculation module 3 calculates the flow field displacement amplitude matrix and the flow field displacement direction matrix of the flow field displacement diagram according to the preset flow field displacement amplitude calculation formula and the preset flow field displacement direction calculation formula, it executes:

[0141] The two-dimensional vector field tensor in the flow field displacement diagram is input into the preset flow field displacement amplitude calculation formula to calculate the flow field displacement amplitude matrix of the flow field displacement diagram.

[0142] The two-dimensional vector field tensor in the flow field displacement diagram is input into the preset flow field displacement direction calculation formula to calculate the flow field displacement direction matrix of the flow field displacement diagram.

[0143] When the second calculation module 3 executes, after calculating the flow field displacement map using the optical flow algorithm, this flow field displacement map is typically represented in the form of a two-dimensional vector field tensor. By inputting the two-dimensional vector field tensor into a preset flow field displacement amplitude calculation formula, the length of each displacement vector is extracted to form a flow field displacement amplitude matrix. Similarly, by inputting the two-dimensional vector field tensor into a preset flow field displacement direction calculation formula, the direction information of each displacement vector is extracted to form a flow field displacement direction matrix.

[0144] The specific formula for calculating the amplitude of the pre-set flow field displacement is as follows:

[0145] ;

[0146] in, Location point The amplitude of the flow field displacement; Location point Two-dimensional vector field tensor in the horizontal axis direction; Location point The two-dimensional vector field tensor along the vertical axis; H is the height of the flow field displacement map; W is the width of the flow field displacement map; i is the location point. The x-coordinate, j is the position point. The ordinate.

[0147] The preset formula for calculating the flow field displacement direction is as follows:

[0148] ;

[0149] ;

[0150] in, Location point Intermediate values ​​for calculating the direction of displacement in the flow field; Let be the arctangent function of two variables, which is defined as: , This is an undefined variable (meaning it is a variable but has not been assigned a value). Location point The direction value of the flow field displacement (i.e., the location point) The corresponding two-dimensional vector field tensor and the deflection angle formed by the positive direction of the horizontal axis). The range is .

[0151] Specifically, after calculating the flow field displacement amplitude matrix and flow field displacement direction matrix of the flow field displacement diagram according to the preset flow field displacement amplitude calculation formula and the preset flow field displacement direction calculation formula, the process also includes:

[0152] Using the flow field displacement amplitude matrix as the hue and the flow field displacement direction matrix as the brightness, combined with a fixed saturation, and following a preset mapping rule, a visualized flow field displacement map corresponding to the flow field displacement map is calculated to visualize the airflow state of the flow field displacement map.

[0153] After calculating the flow field displacement amplitude matrix and the flow field displacement direction matrix of the flow field displacement diagram, normalization processing (such as Min-Max normalization) is first applied to these matrices to obtain the normalized flow field displacement amplitude matrix and the normalized flow field displacement direction matrix. The normalization process is existing technology and will not be described in detail here.

[0154] The normalized flow field displacement amplitude matrix is ​​mapped to the hue of the visualized flow field displacement map, assigning different colors to different airflow intensities. Simultaneously, the normalized flow field displacement direction matrix is ​​mapped to the value of the visualized flow field displacement map, using color variations to represent changes in airflow direction. Furthermore, saturation is set to a fixed value to ensure that hue and value clearly and without interference express the amplitude and direction information of the airflow. Following preset mapping rules, a visualized flow field displacement map (i.e., a colorized flow field displacement map) is generated, achieving intuitive visualization of the airflow state. It can present the airflow state above the textile fabric using easily recognizable color and brightness variations. For example, by observing the color distribution of the visualized flow field displacement map, areas with high and low airflow intensity can be quickly identified; by observing color variations, the main flow direction can be determined.

[0155] The preset mapping rules are as follows:

[0156] (1) Create a three-dimensional HSV color space matrix of the same size as the background image without flow field disturbance. , dimension ,Will The elements are initially assigned a value of 0, that is... The hue channel in Saturation channel and brightness channel The value is assigned to 0.

[0157] (2) Three-dimensional matrix tone channels Color information is represented by the following formula:

[0158] ;

[0159] in, Location point The hue channel value; This is a rounding function; The position points after normalization. The amplitude of the flow field displacement; For the hue channel threshold, take =180, which can be adjusted according to actual needs.

[0160] (3) Three-dimensional matrix saturation channel Color purity is represented by the following formula:

[0161] ;

[0162] in, Location point saturation channel value; Saturation channel threshold, saturation channel threshold For a fixed value, take =255, which is the saturation channel threshold. Set to maximum saturation. Maximum saturation ensures vibrant colors and avoids blurry colors caused by insufficient saturation, thus enhancing the recognizability of flow field displacement direction information.

[0163] (4) Three-dimensional matrix Brightness channel The brightness of a color is represented by the following formula:

[0164] ;

[0165] in, Location point The brightness channel value; The position points after normalization. The displacement direction value of the flow field.

[0166] Through the aforementioned mapping rules, different flow field displacement directions correspond to different hues. During continuous changes, the hue transitions smoothly without visual abrupt changes. Furthermore, the larger the flow field displacement amplitude, the brighter the image, intuitively reflecting intensity differences. This mapping method establishes a correspondence between flow field displacement direction and amplitude data and HSV color space channel characteristics. Through dual-dimensional encoding of hue and brightness, both direction and amplitude can be presented simultaneously, avoiding information fragmentation.

[0167] Specifically, when the third calculation module 4 inputs the flow field displacement amplitude matrix and flow field displacement direction matrix into the preset relative permeability intensity quantification index calculation formula, the preset relative permeability coverage rate quantification index calculation formula, and the preset dominant airflow direction quantification index calculation formula, respectively, and calculates the relative permeability intensity, relative permeability coverage rate, and dominant airflow direction of the flow field displacement map, it executes:

[0168] A statistically robust filtering method based on the absolute deviation of the median is used to filter out outliers in the flow field displacement amplitude matrix and the flow field displacement direction matrix, resulting in the filtered flow field displacement amplitude matrix and the filtered flow field displacement direction matrix.

[0169] The filtered flow field displacement amplitude matrix is ​​input into the preset relative permeability intensity quantification index calculation formula to calculate the relative permeability intensity of the flow field displacement map.

[0170] The filtered flow field displacement amplitude matrix is ​​input into the preset relative air permeability coverage index calculation formula to calculate the relative air permeability coverage of the flow field displacement map.

[0171] The filtered flow field displacement direction matrix is ​​input into the preset formula for calculating the dominant airflow direction quantification index to calculate the dominant airflow direction of the flow field displacement map.

[0172] Specifically, when the third calculation module 4 uses a statistically robust filtering method based on the absolute deviation of the median to filter outliers in the flow field displacement amplitude matrix and the flow field displacement direction matrix, and obtains the filtered flow field displacement amplitude matrix and the filtered flow field displacement direction matrix, the following is executed:

[0173] Calculate the median of all flow field displacement amplitudes in the flow field displacement amplitude matrix, and use it to calculate the set of deviation vectors between all flow field displacement amplitudes and the median of the flow field displacement amplitudes;

[0174] Extract the median of the deviation vectors from the set of deviation vectors to determine the robust threshold;

[0175] Based on a robust threshold and the median of the flow field displacement amplitude, outlier filtering is performed on the flow field displacement amplitude matrix and the flow field displacement direction matrix to obtain the filtered flow field displacement amplitude matrix and the filtered flow field displacement direction moment.

[0176] When the third calculation module 4 is executed, it sorts all the flow field displacement amplitudes in the flow field displacement amplitude matrix, extracts the value located in the middle position to obtain the median of the flow field displacement amplitude, and calculates the absolute value of the difference between each flow field displacement amplitude and the aforementioned median flow field displacement amplitude (i.e., the deviation vector) to construct a set of deviation vectors. Through the set of deviation vectors, the degree to which each data point deviates from the central trend can be quantified.

[0177] The median is calculated again from the above set of deviation vectors. The median of the deviation vectors is used to determine the robustness threshold. The robustness threshold is calculated as follows:

[0178] ;

[0179] in, A robust threshold; Set a coefficient for the robustness threshold, typically set to 3, but can be adjusted as needed. This is the median of the deviation vector.

[0180] For any flow field displacement amplitude, if it is greater than the difference between the median flow field displacement amplitude and the robust threshold, and less than the sum of the median flow field displacement amplitude and the robust threshold, it is determined to be a normal value; otherwise, if any flow field displacement amplitude is less than or equal to the difference between the median flow field displacement amplitude and the robust threshold, or if any flow field displacement amplitude is greater than or equal to the sum of the median flow field displacement amplitude and the robust threshold, it is determined to be an outlier. When a flow field displacement amplitude is identified as a normal value, there is no need to adjust its corresponding flow field displacement amplitude and direction values. When a flow field displacement amplitude is identified as an outlier, its corresponding flow field displacement amplitude and direction values ​​will be filtered out, thus obtaining the filtered flow field displacement amplitude matrix and the filtered flow field displacement direction matrix.

[0181] The calculation process for outlier filtering is as follows:

[0182] ;

[0183] in, The filtered flow field displacement amplitude. The value represents the direction of displacement in the filtered flow field. This represents the median of the flow field displacement amplitude.

[0184] When the third calculation module 4 is executed, it inputs the filtered flow field displacement amplitude matrix into the preset relative permeability intensity quantification index calculation formula to calculate the relative permeability intensity of the flow field displacement map, inputs the filtered flow field displacement amplitude matrix into the preset relative permeability coverage quantification index calculation formula to calculate the relative permeability coverage of the flow field displacement map, and inputs the filtered flow field displacement direction matrix into the preset dominant airflow direction quantification index calculation formula to calculate the dominant airflow direction of the flow field displacement map.

[0185] The specific formula for calculating the preset relative air permeability index is as follows:

[0186] ;

[0187] in, Relative air permeability strength Characterizing the contrast between air permeability and breathability, this quantifies the relative intensity of airflow in a fabric. The stronger the airflow, the greater the relative air permeability. The higher the value, the better the breathability and heat dissipation performance of the fabric.

[0188] The pre-defined formula for calculating the relative breathability coverage rate is as follows:

[0189] ;

[0190] in, This refers to the relative breathability coverage. For the filtered flow field displacement amplitude matrix to satisfy the condition that the absolute value is greater than the air permeability coverage intensity threshold. The number of elements, the air permeability coverage intensity threshold It can be set according to actual needs. Relative breathability coverage. This reflects the relative size of the breathable area of ​​the fabric; the more breathable pores and the wider the distribution of disturbed airflow, the higher the relative breathable coverage. The higher the value, the better the breathability and heat dissipation performance of the fabric.

[0191] The specific formula for calculating the pre-defined dominant airflow direction quantification index is as follows:

[0192] ;

[0193] in, The dominant airflow direction; To be The width of each interval after dividing the text into multiple equal intervals, i.e. K is the total number of intervals. K can be set according to actual needs, and is generally set to 72. This represents the maximum number of elements in each interval (i.e., the number of filtered flow field displacement direction values) when the filtered flow field displacement direction matrix falls into multiple intervals. ), The `argmax` function is used to find the set of arguments that maximizes the objective function. This is the histogram corresponding to the displacement direction matrix of the filtered flow field. , It is a quantity function. For the k-th interval, This is the displacement direction matrix of the filtered flow field. The element located in the k-th interval of the filtered flow field displacement direction matrix (i.e., the filtered flow field displacement direction value); the dominant airflow direction. It reflects the direction of airflow movement that occurs most frequently in the breathable area of ​​the fabric, which helps researchers analyze the influence of fabric weaving patterns, seams, pores, etc. on the deviation of breathable airflow.

[0194] Specifically, when module 5 is executed, it determines the relative air permeability intensity. Relative breathability coverage and the direction of the dominant airflow By combining preset evaluation criteria, the air permeability performance of textile fabrics is comprehensively judged. For example, different thresholds can be set experimentally to distinguish air permeability levels such as "high air permeability," "medium air permeability," and "low air permeability," based on relative air permeability intensity. Relative breathability coverage and the direction of the dominant airflow The air permeability score of the textile fabric is calculated by comprehensive methods (such as weighted average method), and the air permeability of the textile fabric is determined by the threshold range in which the air permeability score is located.

[0195] As can be seen from the above, this fabric breathability measurement device acquires a background image without flow field disturbance and a flow field disturbance image simulated by human body temperature above the textile fabric through a pre-set background schlieren imaging system. Using the background grayscale image corresponding to the background image without flow field disturbance as a reference image, the flow field displacement map of the flow field disturbance grayscale image corresponding to the flow field disturbance image is calculated through an optical flow algorithm. According to the preset flow field displacement amplitude calculation formula and the preset flow field displacement direction calculation formula, the flow field displacement amplitude matrix and the flow field displacement direction matrix of the flow field displacement map are calculated. The flow field displacement amplitude matrix and the flow field displacement direction matrix are input into the preset relative breathability intensity quantification index calculation formula, the preset relative breathability coverage index calculation formula, and the preset dominant airflow direction quantification index calculation formula, respectively, to calculate the relative breathability intensity, relative breathability coverage, and dominant airflow direction of the flow field displacement map. Based on the relative breathability intensity, The relative air permeability coverage and dominant airflow direction are used to determine the air permeability performance of textile fabrics. Then, using an optical flow algorithm, combined with preset formulas for calculating flow field displacement amplitude, flow field displacement direction, relative air permeability intensity, relative air permeability coverage, and dominant airflow direction, the relative air permeability intensity, relative air permeability coverage, and dominant airflow direction are calculated to determine the air permeability performance of the textile fabric. This solves the problem that existing fabric air permeability testing methods can only output static values ​​and cannot present the airflow state on the fabric surface and in the pores, making it difficult for researchers to pinpoint the specific impact of fabric structure design on air permeability. This method enables a comprehensive and multi-dimensional evaluation of fabric air permeability performance, allowing researchers to gain a deeper understanding of the specific impact of fabric structure design on air permeability, and improving the efficiency and accuracy of fabric air permeability measurement.

[0196] Please refer to Figure 3, which is a schematic diagram of the structure of an electronic device provided in an embodiment of this application. This application provides an electronic device including: a processor 301 and a memory 302. The processor 301 and the memory 302 are interconnected and communicate with each other via a communication bus 303 and / or other forms of connection mechanisms (not shown). The memory 302 stores a computer program executable by the processor 301. When the electronic device is running, the processor 301 executes the computer program to perform the fabric breathability measurement method in any optional implementation of the above embodiments, to achieve the following functions: acquiring a background image without flow field disturbance and a flow field disturbance image after simulating human body temperature through a pre-set background schlieren imaging system, using a background image without flow field disturbance. Using the corresponding background grayscale image as a reference image, the flow field displacement map of the corresponding flow field disturbance grayscale image is calculated through optical flow algorithm. According to the preset flow field displacement amplitude calculation formula and the preset flow field displacement direction calculation formula, the flow field displacement amplitude matrix and flow field displacement direction matrix of the flow field displacement map are calculated. The flow field displacement amplitude matrix and flow field displacement direction matrix are input into the preset relative air permeability intensity quantification index calculation formula, the preset relative air permeability coverage rate quantification index calculation formula, and the preset dominant airflow direction quantification index calculation formula, respectively, to calculate the relative air permeability intensity, relative air permeability coverage rate, and dominant airflow direction of the flow field displacement map. Based on the relative air permeability intensity, relative air permeability coverage rate, and dominant airflow direction, the air permeability performance of the textile fabric is determined.

[0197] This application provides a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, it performs the fabric breathability measurement method in any optional implementation of the above embodiments to achieve the following functions: acquiring a background image without flow field disturbance and a flow field disturbance image simulated by human body temperature above the textile fabric using a pre-set background schlieren imaging system; using the background grayscale image corresponding to the background image without flow field disturbance as a reference image; calculating the flow field displacement map of the flow field disturbance grayscale image corresponding to the flow field disturbance image using an optical flow algorithm; and based on a preset flow field... The displacement amplitude calculation formula and the preset flow field displacement direction calculation formula are used to calculate the flow field displacement amplitude matrix and flow field displacement direction matrix of the flow field displacement map. The flow field displacement amplitude matrix and flow field displacement direction matrix are then input into the preset relative air permeability intensity quantification index calculation formula, the preset relative air permeability coverage rate quantification index calculation formula, and the preset dominant airflow direction quantification index calculation formula, respectively. The relative air permeability intensity, relative air permeability coverage rate, and dominant airflow direction of the flow field displacement map are then calculated. Based on the relative air permeability intensity, relative air permeability coverage rate, and dominant airflow direction, the air permeability performance of the textile fabric is determined. The storage medium can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as Static Random Access Memory (SRAM), Electrically Erasable Programmable Read-Only Memory (EEPROM), Erasable Programmable Read Only Memory (EPROM), Programmable Red-Only Memory (PROM), Read-Only Memory (ROM), magnetic storage, flash memory, magnetic disk, or optical disk.

[0198] In the embodiments provided in this application, it should be understood that the disclosed apparatus and methods can be implemented in other ways. The apparatus embodiments described above are merely illustrative. For example, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. Furthermore, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Additionally, the displayed or discussed mutual couplings, direct couplings, or communication connections may be through some communication interfaces; indirect couplings or communication connections between devices or units may be electrical, mechanical, or other forms.

[0199] Furthermore, the units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment, depending on actual needs.

[0200] Furthermore, the functional modules in the various embodiments of this application can be integrated together to form an independent part, or each module can exist independently, or two or more modules can be integrated to form an independent part.

[0201] In this document, relational terms such as first and second are used only to distinguish one entity or operation from another entity or operation, without necessarily requiring or implying any such actual relationship or order between these entities or operations.

[0202] The above description is merely an embodiment of this application and is not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for measuring the air permeability of fabrics, used to measure the air permeability of textile fabrics, characterized in that, The steps include: acquiring a background image without flow field disturbance and a flow field disturbance image after simulating human body temperature above the textile fabric through a pre-set background schlieren imaging system; using the background grayscale image corresponding to the background image without flow field disturbance as a reference image, calculating the flow field displacement map of the flow field disturbance grayscale image corresponding to the flow field disturbance image through an optical flow algorithm. Based on the preset formulas for calculating the amplitude and direction of the flow field displacement, the flow field displacement amplitude matrix and the flow field displacement direction matrix of the flow field displacement diagram are calculated. The flow field displacement amplitude matrix and the flow field displacement direction matrix are respectively input into the preset relative permeability intensity quantification index calculation formula, the preset relative permeability coverage rate quantification index calculation formula and the preset dominant airflow direction quantification index calculation formula to calculate the relative permeability intensity, relative permeability coverage rate and dominant airflow direction of the flow field displacement map. The air permeability of the textile fabric is determined based on the relative air permeability intensity, the relative air permeability coverage, and the dominant airflow direction.

2. The method for measuring the air permeability of fabrics according to claim 1, characterized in that, The background schlieren imaging system includes an airflow isolation hood, and a background plate, a light source, an imaging camera, a bionic heat source, and a textile fabric disposed inside the airflow isolation hood; the light source is attached to the background plate and placed on the back of the background plate; The background panel faces the imaging camera, and the background panel and the imaging camera are on the same horizontal line; the biomimetic heat source is set on the back of the textile fabric, and the textile fabric is placed face up on the inner bottom surface of the airflow isolation cover between the background panel and the imaging camera, so that the imaging camera can capture the airflow disturbance above the textile fabric.

3. The method for measuring the air permeability of fabrics according to claim 1, characterized in that, Using the background grayscale image corresponding to the background image without flow field disturbance as a reference image, an optical flow algorithm is used to calculate the real-time flow field displacement map corresponding to the flow field disturbance grayscale image. This includes: performing grayscale processing on the background image without flow field disturbance and the flow field disturbance image respectively to obtain the background grayscale image corresponding to the background image without flow field disturbance and the flow field disturbance grayscale image corresponding to the flow field disturbance image; using the background grayscale image as a reference image, an optical flow algorithm is used to calculate the two-dimensional vector field tensor of the flow field disturbance grayscale image to obtain the flow field displacement map corresponding to the flow field disturbance grayscale image.

4. The method for measuring the air permeability of fabrics according to claim 3, characterized in that, The flow field displacement amplitude matrix and flow field displacement direction matrix of the flow field displacement diagram are calculated according to the preset flow field displacement amplitude calculation formula and the preset flow field displacement direction calculation formula, including: inputting the two-dimensional vector field tensor in the flow field displacement diagram into the preset flow field displacement amplitude calculation formula to calculate the flow field displacement amplitude matrix of the flow field displacement diagram; and inputting the two-dimensional vector field tensor in the flow field displacement diagram into the preset flow field displacement direction calculation formula to calculate the flow field displacement direction matrix of the flow field displacement diagram.

5. The method for measuring the air permeability of fabrics according to claim 1, characterized in that, After calculating the flow field displacement amplitude matrix and flow field displacement direction matrix of the flow field displacement map according to the preset flow field displacement amplitude calculation formula and the preset flow field displacement direction calculation formula, the method further includes: using the flow field displacement amplitude matrix as the hue and the flow field displacement direction matrix as the brightness, combined with a fixed saturation, and according to the preset mapping rules, to calculate the corresponding visualized flow field displacement map, so as to visualize the airflow state of the flow field displacement map.

6. The method for measuring the air permeability of fabrics according to claim 1, characterized in that, The flow field displacement amplitude matrix and the flow field displacement direction matrix are respectively input into preset formulas for calculating relative air permeability intensity, relative air permeability coverage, and dominant airflow direction, to calculate the relative air permeability intensity, relative air permeability coverage, and dominant airflow direction of the flow field displacement map. This includes: using a statistically robust filtering method based on the absolute deviation of the median to filter outliers in the flow field displacement amplitude matrix and the flow field displacement direction matrix, obtaining filtered flow field displacement amplitude matrix and filtered flow field displacement direction matrix; inputting the filtered flow field displacement amplitude matrix into the preset formula for calculating relative air permeability intensity to calculate the relative air permeability intensity of the flow field displacement map; inputting the filtered flow field displacement amplitude matrix into the preset formula for calculating relative air permeability coverage to calculate the relative air permeability coverage of the flow field displacement map; and inputting the filtered flow field displacement direction matrix into the preset formula for calculating dominant airflow direction to calculate the dominant airflow direction of the flow field displacement map.

7. The method for measuring the air permeability of fabrics according to claim 6, characterized in that, A statistically robust filtering method based on the absolute deviation of the median is used to filter outliers in the flow field displacement amplitude matrix and the flow field displacement direction matrix, resulting in filtered flow field displacement amplitude and flow field displacement direction matrices. This includes: calculating the median of all flow field displacement amplitudes in the flow field displacement amplitude matrix to obtain a set of deviation vectors between all flow field displacement amplitudes and the median; extracting the median of the deviation vectors from the set of deviation vectors to determine a robust threshold; and performing outlier filtering on the flow field displacement amplitude matrix and the flow field displacement direction matrix based on the robust threshold and the median, resulting in filtered flow field displacement amplitude and flow field displacement direction matrices.

8. A fabric breathability measurement device, used to measure the breathability of textile fabrics, characterized in that, include: The acquisition module is used to acquire a background image without flow field disturbance above the textile fabric and a flow field disturbance image after simulating human body temperature through a pre-set background schlieren imaging system. The first calculation module is used to calculate the flow field displacement map of the flow field disturbance grayscale image corresponding to the flow field disturbance image using an optical flow algorithm, with the background grayscale image corresponding to the background image without flow field disturbance as a reference image. The second calculation module is used to calculate the flow field displacement amplitude matrix and the flow field displacement direction matrix of the flow field displacement diagram according to the preset flow field displacement amplitude calculation formula and the preset flow field displacement direction calculation formula. The third calculation module is used to input the flow field displacement amplitude matrix and the flow field displacement direction matrix into the preset relative permeability intensity quantification index calculation formula, the preset relative permeability coverage rate quantification index calculation formula and the preset dominant airflow direction quantification index calculation formula, respectively, to calculate the relative permeability intensity, relative permeability coverage rate and dominant airflow direction of the flow field displacement map. The determining module is used to determine the air permeability of the textile fabric based on the relative air permeability intensity, the relative air permeability coverage, and the dominant airflow direction.

9. An electronic device, characterized in that, It includes a processor and a memory, the memory storing a computer program executable by the processor, which, when executing the computer program, performs the steps in the fabric breathability measurement method as described in any one of claims 1-7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it performs the steps in the fabric breathability measurement method as described in any one of claims 1-7.

Images