A reasoning method and system for the braiding process of special-shaped structural parts based on the eccentric theory

Abstract

The present invention relates to the technical field of three-dimensional braiding processes, and particularly relates to a method and system for reasoning about the braiding process of special-shaped structural parts based on the eccentric theory. The method includes the following steps: using the three-dimensional model to obtain a uniform surface mesh of the key cross-section of the mandrel; based on the eccentric braiding theory and the uniform surface mesh, obtaining a braiding angle vector field; according to the braiding angle vector field, optimizing the desired fabric structure on different regions of the mandrel; and through the desired fabric structure, reasoning and generating eccentric braiding process parameters. The process parameters inferred and generated by the present invention completely eliminate the fabric defects at the complex geometric features of the special-shaped structural parts, and the difference in the coverage rate between the inner and outer sides is reduced by more than 24%. It breaks through the braiding pose constraints of traditional braiding processes and provides a theoretical basis for the process planning software of a low-cost, fast, and automated braiding production line for large-sized special-shaped structural parts.

Description

Technical Field

[0001] The present invention relates to the technical field of three-dimensional braiding processes, and in particular, to a method and system for inferring a braiding process of a special-shaped structural member based on an eccentric theory. Background Art

[0002] At present, with the increasing demand for lightweight large-sized special-shaped structural members in the aerospace field, the demand for using composite materials instead of traditional metal materials for low-cost and rapid manufacturing of structural members such as large aircraft frames, floor beams, rocket nozzles, and throat liners is increasing. At the same time, processes such as manual laying, automatic laying, and automatic winding are difficult to form special-shaped structural members with high efficiency and high precision. Therefore, the three-dimensional braiding precise forming technology for special-shaped structural members has become a current research hotspot.

[0003] In the prior art, the analytical method is usually used to infer the braiding process parameters of special-shaped structural members with geometric features such as large curvature and variable cross-section. This method has the following deficiencies: First, it is difficult to establish the mapping relationship between the process parameters and the fabric structure through the given geometric constraint conditions, so as to infer the braiding process parameters in eccentric braiding; Second, when braiding using the inferred process parameters, there will be fabric defects such as fabric stacking and sparseness. The prior art adopts the kinematic method to infer the process parameters of special-shaped structural members under the eccentric braiding process, but this method takes the braiding angle as a single target and is difficult to solve the fabric defect problem in special-shaped structural members.

[0004] Therefore, in order to achieve the precise forming of special-shaped structural members, it is urgent to propose a high-quality braiding process parameter inference method that can eliminate fabric defects. Summary of the Invention

[0005] Aiming at the defects in the prior art, the present invention provides a method and system for inferring a braiding process of a special-shaped structural member based on an eccentric theory.

[0006] On the one hand, a method for reasoning about the braiding process of special-shaped structural parts based on the eccentric theory provided by the present invention includes the following steps: obtaining a three-dimensional model of the core mold of the special-shaped structural part; using the three-dimensional model to obtain a uniform surface mesh of the key cross-section of the core mold; based on the eccentric braiding theory and the uniform surface mesh, obtaining a braiding angle vector field; according to the braiding angle vector field, optimizing the desired fabric structure in different regions of the core mold; and through the desired fabric structure, reasoning and generating eccentric braiding process parameters. By using the three-dimensional model of the core mold of the special-shaped structural part and obtaining a uniform surface mesh of the key cross-section, the present invention ensures the accuracy of the basic data for the braiding process design, providing a reliable basis for subsequent process reasoning; based on the eccentric braiding theory and the uniform surface mesh, calculating the braiding angle vector field effectively combines the theoretical model with the actual braiding requirements, improving the scientificity and accuracy of the braiding process; through the braiding angle vector field, optimizing the desired fabric structure in different regions of the core mold and reasoning and generating eccentric braiding process parameters, realizing the precise reasoning of the braiding process of the special-shaped structural part, which is beneficial to eliminating the fabric defect problems existing in the braiding process.

[0007] Optionally, the step of using the three-dimensional model to obtain a uniform surface mesh of the key cross-section of the core mold includes: using the three-dimensional model to extract point cloud data; performing orthogonal projection on the point cloud data to obtain the center line of the special-shaped structural part; using the spatial relationship between the center line and the point cloud data to reconstruct the key cross-section of the core mold; and connecting the points of the key cross-section through a custom call sequence to generate a uniform surface mesh. By extracting the point cloud data of the three-dimensional model of the core mold, the present invention provides a rich data source for subsequent mesh generation, ensuring the comprehensiveness and accuracy of the data; performing orthogonal projection on the point cloud data to obtain the center line of the special-shaped structural part not only simplifies the data structure but also provides a benchmark for the reconstruction of the key cross-section, making subsequent operations more accurate and efficient; using the spatial relationship between the center line and the point cloud data to reconstruct the key cross-section of the core mold and connecting the points of the key cross-section through a custom call sequence to generate a uniform surface mesh not only ensures the uniformity and continuity of the mesh but also provides high-quality input data for subsequent braiding process reasoning, thereby improving the accuracy and reliability of the entire braiding process.

[0008] Optionally, obtaining the braiding angle vector field based on the eccentric braiding theory and the homogenized surface mesh includes: establishing a spatial relationship equation according to the position of the yarn on the guide ring and the landing position on the mandrel under the eccentric braiding process; performing a time differential operation on the spatial relationship equation to obtain an expression for the braiding speed of the spindle speed mapped on the surface of the mandrel; obtaining an expression for the yarn landing position according to the braiding speed expression; and obtaining the braiding angle vector field based on the yarn landing position expression and the homogenized surface mesh. According to the spatial relationship between the yarn on the guide ring and the landing point on the mandrel under the eccentric braiding process, the present invention establishes an accurate mathematical model, providing a solid theoretical basis for the calculation of the braiding speed; by performing a time differential operation on the spatial relationship equation, the mapping relationship of the spindle speed on the surface of the mandrel, that is, the braiding speed expression, is obtained, realizing the transformation from theory to practice and providing a basis for the calculation of the braiding angle; combining the yarn landing point expression and the homogenized surface mesh, the braiding angle vector field is successfully generated, improving the accuracy of the braiding process and promoting the wide application of the eccentric braiding technology in the manufacturing of special-shaped structural parts.

[0009] Optionally, the spatial relationship equation is as follows:

[0010] ,

[0011] The braiding speed satisfies the following expression:

[0012] ,

[0013] The expression for the yarn landing position is as follows:

[0014] ,

[0015] Where, is the angle of the yarn landing point in the cross-section coordinate system of the mandrel, is the angle of the intersection point of the yarn and the guide ring in the coordinate system of the guide ring, is the eccentricity value, is the radius of the mandrel, is the braiding speed of the yarn, is the radius of the guide ring, is the braiding speed of the spindle speed mapped on the surface of the mandrel, is the traction speed, is the braiding time, represents the yarn landing position when the braiding time is , is a constant. The spatial relationship equation established in the present invention accurately describes the correlation between the position of the yarn on the guiding ring and the landing position on the mandrel, providing a theoretical basis for the simulation and prediction of the braiding process; the derived braiding speed expression reveals the speed distribution law of the yarn moving along the surface of the mandrel, providing a basis for controlling the braiding density and fabric structure; the derived yarn landing position expression directly guides the precise positioning of the yarn on the mandrel, ensuring the accuracy and stability of the braiding process.

[0016] Optionally, obtaining the braiding angle vector field based on the yarn landing position expression and the uniform surface mesh includes: obtaining the desired braiding angle based on the yarn landing position expression and the uniform surface mesh; obtaining the braiding angle vector field according to the desired braiding angle. By combining the position of the yarn landing with the surface data of the uniform surface mesh, the present invention accurately calculates the desired braiding angle, ensuring the precise control of the braiding angle and providing a basis for the stability and consistency of the fabric structure; the determined desired braiding angle provides a direct basis for the construction of the braiding angle vector field, enabling the quantification and prediction of the angle changes during the braiding process, and improving the controllability and predictability of the braiding process; the obtained braiding angle vector field intuitively shows the braiding angle distribution of the yarn on the surface of the mandrel, enhancing the overall performance of the eccentric braiding process.

[0017] Optionally, the expression of the braiding angle vector field is as follows:

[0018] ,

[0019] where, represents the braiding angle direction vector on the th triangular patch, represents the clockwise yarn, represents the counterclockwise yarn, represents the projection vector of the center line on the th triangular patch, is the normal vector of the th triangular patch, is the desired braiding angle corresponding to the th triangular patch, is a generalized rotation matrix. The present invention provides an accurate description of the braiding angle of the yarn on the surface of the mandrel, enabling quantitative analysis of the arrangement and interweaving pattern of the yarn during the braiding process, providing a scientific basis for optimizing the fabric structure and improving the braiding efficiency; the visual expression of the braiding angle vector field intuitively shows the distribution state of the yarn on the surface of complex shaped structural parts, helping to better understand the braiding process, achieve precise control and adjustment, and thus improve the quality and performance of the product; through the analysis of the braiding angle vector field, the influence of different braiding parameters on the fabric structure and performance is predicted and evaluated, promoting the application and development of the eccentric braiding technology in the field of automated braiding.

[0020] Optionally, optimizing the desired fabric structure in different regions of the mandrel according to the braiding angle vector field includes: generating a braiding angle reference line for clockwise and counterclockwise yarns according to the braiding angle vector field; extracting reference points through the braiding angle reference line, where the reference points are the intersections of the braiding angle reference line and the key planes of the reconstructed mandrel; re-dividing the edges of the key section based on the positions of the reference points and the perimeter of the key section where they are located to obtain a division result; and optimizing the desired fabric structure in different regions of the mandrel according to the division result. The present invention realizes precise control of the braiding angles of the yarns by generating the braiding angle reference lines for clockwise and counterclockwise yarns, providing a reliable basis for constructing complex fabric structures; extracting the intersections of the braiding angle reference line and the key planes of the reconstructed mandrel as reference points not only simplifies the complexity of fabric structure design but also ensures the uniformity and rationality of the yarn distribution on the key section; re-dividing the edges based on the reference point positions and the perimeter of the key section optimizes the layout of the desired fabric structure in different regions of the mandrel, improving both the performance of the fabric and meeting the special requirements of the shaped structural parts for the fabric structure.

[0021] Optionally, inferring and generating the eccentric braiding process parameters through the desired fabric structure includes: obtaining the speeds, trajectories, and postures corresponding to all yarns through the desired fabric structure; performing a weighted average calculation on the speeds, trajectories, and postures to obtain the eccentric braiding process parameters. The present invention accurately obtains the speeds, trajectories, and postures of all yarns during the braiding process, providing detailed data support for setting process parameters and ensuring the stability and controllability of the braiding process; by performing a weighted average calculation on the speeds, trajectories, and postures, the motion characteristics of different yarns are effectively integrated, making the finally obtained eccentric braiding process parameters more reasonable and accurate, fully reflecting the overall requirements of the fabric structure.

[0022] Optionally, the eccentric braiding process parameters satisfy the following expression:

[0023] ,

[0024] where, is the traction speed corresponding to the yarn, is the weight value corresponding to the yarn, is the position of the center point of the guide ring, is the normal vector of the guide ring, is the traction speed under the eccentric weaving process, is the position of the weaving trajectory under the eccentric weaving process, is the attitude of the weaving trajectory under the eccentric weaving process, is the number of triangular patches on the clockwise yarn, represents the clockwise yarn, represents the counterclockwise yarn, , is the spatial coordinate. The present invention comprehensively considers multiple key factors such as the speed, trajectory, and attitude of the yarn, ensuring the accuracy and stability of the weaving process, and providing reliable technical support for the manufacturing of special-shaped structural parts; by calculating process parameters through the method of weighted averaging, it not only reflects the overall trend of yarn movement but also takes into account local differences, making the weaving result more in line with the design requirements and improving the quality and performance of the product; this expression simplifies the calculation process of eccentric weaving process parameters, improves the efficiency of process design, and provides strong support for the rapid iteration and optimization of the weaving process.

[0025] In a second aspect, a reasoning system for the weaving process of special-shaped structural parts based on the eccentric theory provided by the present invention includes an input device, a processor, an output device, and a memory. The input device, the processor, the output device, and the memory are interconnected. Among them, the memory is used to store computer programs, and the computer programs include program instructions. The processor is configured to call the program instructions, and the system uses the reasoning method for the weaving process of special-shaped structural parts based on the eccentric theory. Through precise calculation and reasoning, the system can automatically generate eccentric weaving process parameters that meet the design requirements, greatly improving the accuracy and efficiency of the weaving process; comprehensively considering multiple factors such as the speed, trajectory, and attitude of the yarn, it ensures the uniform distribution and reasonable interweaving of the yarn during the weaving process, thereby improving the quality and performance of special-shaped structural parts; it has high flexibility and scalability, can quickly adjust process parameters according to different design requirements, and provides strong technical support for the manufacturing of special-shaped structural parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is the flowchart of the reasoning method for the weaving process of special-shaped structural parts based on the eccentric theory according to the embodiment of the present invention;

[0027] Figure 2 is the schematic diagram of the main components of the weaving machine according to the embodiment of the present invention;

[0028] Figure 3 Schematic diagram for comparison between centric vertical weaving process and eccentric weaving process according to an embodiment of the present invention;

[0029] Figure 4 Schematic diagram for the optimization process of the desired fabric structure according to an embodiment of the present invention;

[0030] Figure 5 Schematic diagram for the reasoning process of eccentric weaving process parameters according to an embodiment of the present invention;

[0031] Figure 6 Schematic diagram for the weaving experiment according to an embodiment of the present invention;

[0032] Figure 7 Schematic diagram for comparison of weaving process parameters according to an embodiment of the present invention;

[0033] Figure 8 Schematic diagram for comparison of fabric structures of different weaving processes according to an embodiment of the present invention;

[0034] Figure 9 Schematic diagram for the structure of a weaving process inference system for special-shaped structural parts based on the eccentric theory according to an embodiment of the present invention. Detailed implementation manners

[0035] The specific embodiments of the present invention will be described in detail below. It should be noted that the embodiments described here are only for illustrative purposes and are not used to limit the present invention. In the following description, in order to provide a thorough understanding of the present invention, a large number of specific details are set forth. However, it will be apparent to those of ordinary skill in the art that the present invention does not have to employ these specific details. In other instances, well-known circuits, software, or methods have not been specifically described in order to avoid obscuring the present invention.

[0036] Throughout the specification, the reference to "an embodiment", "embodiments", "an example" or "examples" means that the specific features, structures, or characteristics described in connection with the embodiment or example are included in at least one embodiment of the present invention. Thus, the phrases "in an embodiment", "in embodiments", "an example" or "examples" appearing throughout the specification do not necessarily all refer to the same embodiment or example. In addition, the specific features, structures, or characteristics may be combined in any suitable combination and / or sub-combination in one or more embodiments or examples. In addition, those of ordinary skill in the art should understand that the diagrams provided herein are for illustrative purposes only and are not necessarily drawn to scale.

[0037] Please refer to Figure 1 , an embodiment of the present invention provides a weaving process inference method for special-shaped structural parts based on the eccentric theory, and the method includes the following steps:

[0038] S1. Obtain the 3D model of the core mold for the special-shaped structural part.

[0039] In one embodiment, the 3D model of the core mold for the special-shaped structural part was constructed using the professional 3D modeling software SolidWorks, and the 3D model accurately reflects the actual shape and size of the core mold.

[0040] S2. Utilize the 3D model to obtain the uniform surface mesh of the key cross-section of the core mold.

[0041] Among them, S2 further includes the following steps:

[0042] S21. Extract point cloud data using the 3D model of the core mold.

[0043] In one embodiment, the constructed 3D model is saved in the STL format. The STL format is a commonly used file format in the fields of 3D printing, numerical simulation, etc., and contains the geometric information of the model.

[0044] Furthermore, in SolidWorks, use the ScanTo3D plug-in to open the STL model in the form of a mesh file and save it as the OBJ format. The OBJ format is a common 3D model file format and is applicable to various 3D processing software.

[0045] Furthermore, install and configure the PCL (Point Cloud Library). The PCL is an open-source point cloud processing library that provides rich point cloud processing algorithms and tools.

[0046] Furthermore, use the point cloud library mesh sampling tool of PCL to convert the OBJ file into point cloud data and generate a point cloud file in the PCD format. The point cloud file contains the 3D coordinate information of each point in the point cloud.

[0047] S22. Perform orthogonal projection on the point cloud data to obtain the center line of the special-shaped structural part.

[0048] In one embodiment, first, preprocess the extracted point cloud data, including removing noise points and filling in missing parts to ensure the accuracy and integrity of the data.

[0049] Furthermore, according to the characteristics and requirements of the special-shaped structural part, select the main extension direction of the structural part as the orthogonal projection direction.

[0050] Furthermore, project the preprocessed point cloud data along the selected orthogonal direction. Each point in the projection will find its corresponding projection point on the projection plane, forming a projected point set.

[0051] Further, on the projected point set, a mathematical algorithm is used to extract the center line. The mathematical algorithm includes the least squares method and the Hough transform, which are used to identify and connect the key features in the projected points, thereby depicting the center line of the structural member.

[0052] Further, post-processing is performed on the extracted center line, including smoothing processing and removing redundant parts, to ensure its accuracy and aesthetics.

[0053] S23. Utilize the spatial relationship between the center line and the point cloud data to reconstruct the key cross-sections of the core mold.

[0054] In one embodiment, first, based on the extracted center line data, the position of the center line in three-dimensional space is determined.

[0055] Further, according to the design requirements of the core mold, specific cross-section positions are selected, and the cross-section positions and the center line are used as references to perform a slicing operation on the point cloud data. The slicing operation extracts a subset of the point cloud that intersects the selected cross-section.

[0056] Further, the sliced point cloud subset is processed to extract the contour of the cross-section, including steps of point cloud filtering, segmentation, and boundary recognition.

[0057] Further, the least squares method and the curve fitting method are used to fit the extracted contour to generate a smooth and accurate cross-section shape.

[0058] Further, according to the fitted cross-section shape, combined with the overall design and functional requirements of the core mold, the key cross-sections of the core mold are reconstructed.

[0059] S24. Connect the points on the key cross-sections through a custom call sequence to generate a uniform surface mesh.

[0060] In one embodiment, based on a 3D modeling software, according to the order and relationship of the point position data, a custom call sequence is defined, and the sequence will guide the software on how to connect these points in sequence.

[0061] Further, use the connection tool or command in the software to connect the points on the key cross-sections according to the custom call sequence, forming a network composed of line segments or curves.

[0062] Further, use the mesh generation tool or command in the software to initially generate a surface mesh according to the connected points and network.

[0063] Further, use the mesh optimization tool or plugin in the software to optimize the initially generated mesh to make the mesh more uniform and smooth, thereby obtaining a uniform surface mesh.

[0064] It should be noted that in most mandrels, due to design reasons, there are braiding redundant features such as through holes and bosses in the 3D model, resulting in uneven distribution of surface points on the mandrel, which affects the generation of braiding angles of each part of the mandrel 3D model and further reduces the optimization accuracy of the expected fabric structure. Therefore, the present invention uses a model reconstruction algorithm to perform secondary processing on the surface mesh of the mandrel.

[0065] S3. Based on the eccentric braiding theory and the homogenized surface mesh, obtain the braiding angle vector field.

[0066] Among them, S3 further includes the following steps:

[0067] S31. According to the eccentric theory, establish a spatial relationship equation.

[0068] The braiding process of the special-shaped structural part is shown in Figure 2. The braiding machine mainly includes two motion systems, namely the main drive system of the braiding machine and the braiding attitude adjustment system. The main drive system makes the clockwise spindles and counterclockwise spindles drive the yarns to perform high-speed interleaving motion. At the same time, the robot in the braiding attitude adjustment system holds the mandrel and continuously advances in different postures. After the yarns moving in the large-scale opposite direction are woven into a net-like structure in the air, through the constraint of the guide ring, finally, a fabric with different directions and highly intertwined is formed on the surface of the mandrel. Among them, the main drive system is composed of multiple servo motors and a closed-loop gear transmission chain, and the braiding attitude adjustment system is composed of one or more robots equipped with linear guides.

[0069] In the eccentric braiding theory, the centric vertical braiding process is first introduced, as shown in Figure 3 (a).

[0070] Specifically, in the centric vertical braiding process, the tangent point of the yarn landing point and the outer contour of the mandrel at any position can be described by a mathematical relationship, and the mathematical relationship is as follows:

[0071] ,

[0072] Among them, is the traction speed, is the braiding speed of the yarn, is the radius of the guide ring, is the radius of the mandrel, is the convergence radius, is the initial convergence length, is the braiding angle, is the braiding time. It can be seen from Figure 3 (a) that the yarns are evenly distributed around the mandrel and all the yarns have the same rotation speed. Therefore, the preform has the same circumferential structure on the mandrel, and from the above relationship, it can be seen that when When appropriately selected, the size of the knitting angle during the knitting process is only related to the knitting speed and the traction speed of the yarn. Under the condition of eccentric knitting, due to the existence of the eccentricity value, after the spindle speed is mapped onto the surface of the mandrel, the spindle speed is inconsistent with the circumferential deposition speed of the yarn and varies with the change of the landing position, as Figure 3 (b) shows.

[0073] In one embodiment, according to the position of the yarn on the guide ring and the landing position on the mandrel under the eccentric knitting process, a spatial relationship equation is established, and the form is as follows:

[0074] ,

[0075] where, is the angle of the yarn landing point in the coordinate system of the mandrel cross-section, is the angle of the intersection point of the yarn and the guide ring in the coordinate system of the guide ring, also called the knitting angle, is the eccentricity value, is the radius of the mandrel, is the radius of the guide ring.

[0076] It should be noted that in the eccentric knitting process, the size of the knitting angle affects the strength, elasticity, density and knitting efficiency of the knitted fabric. The desired knitting angle should be determined according to the specific type of knitted fabric, its use and the required performance. Therefore, when designing the knitting process, these factors should be fully considered to obtain the best knitting effect.

[0077] S32. Perform a time differential operation on the spatial relationship equation to obtain the expression of the knitting speed at which the spindle speed is mapped onto the surface of the mandrel.

[0078] Under the condition of eccentric knitting, due to the existence of the eccentricity value, after the spindle speed is mapped onto the surface of the mandrel, the spindle speed is inconsistent with the circumferential deposition speed of the yarn and varies with the change of the landing position.

[0079] In one embodiment, to obtain the knitting speed at which the spindle speed is mapped onto the surface of the mandrel under eccentric knitting, perform a differential operation with respect to time on in step S31, and the expression form is as follows:

[0080] ,

[0081] where, is the knitting speed at which the spindle speed is mapped onto the surface of the mandrel.

[0082] S33. Obtain the expression of the yarn landing position according to the knitting speed expression.

[0083] In one embodiment, based on the braiding speed expression obtained in step S32 and in combination with the specific braiding speed obtained in the braiding process, the angle of the yarn landing point in the core mold cross-section coordinate system is determined. .

[0084] Further, the angle is substituted into the spatial relationship equation in step S31 to obtain the braiding angle .

[0085] In another embodiment, based on the eccentricity theory, using the braiding speed expression, an expression for the yarn landing point position in the case of eccentricity is obtained, and the expression is as follows:

[0086] ,

[0087] wherein, is the traction speed, is the braiding time, represents the yarn landing point position when the braiding time is , is a constant.

[0088] S34. Based on the yarn landing point position expression and the uniform surface mesh, a braiding angle vector field is obtained.

[0089] Among them, S34 further includes the following steps:

[0090] S341. Based on the surface data of the yarn landing point position expression and the uniform surface mesh, an expected braiding angle is obtained.

[0091] In one embodiment, considering the strength, elasticity, density, and braiding efficiency of the braided fabric, the braiding performance of the eccentric braiding process is designed.

[0092] Specifically, first set an eccentricity value, and use the patch data on the surface of the uniform surface mesh, in combination with the expressions in steps S31, S32, and S33, to solve for the braiding angle, braiding speed, and yarn landing point position on the mesh surface. It should be noted that the patch data refers to the spatial data of each plane on the surface of the core mold three-dimensional model.

[0093] Further, according to the braiding angle, the braiding speed, and the yarn landing point position, the change state of the fabric structure on both sides of the eccentricity is measured, which involves fabric defects.

[0094] Further, the sparsity degree of the inner and outer sides of the fabric structure is judged.

[0095] Further, change the eccentricity value and continuously repeat the above steps until the surface landing point distribution of the fabric structure patches is uniform. At this time, this eccentricity value is the expected eccentricity value.

[0096] Further, substitute the expected eccentricity value into the expression of the braiding angle under the eccentricity condition in step S31, and solve for the braiding angle, which is the expected braiding angle.

[0097] S342. Obtain a braiding angle vector field according to the expected braiding angle.

[0098] In one embodiment, according to step S341, obtain the expected braiding angle data on each triangular patch of the reconstructed uniform surface mesh.

[0099] Further, generate a braiding angle vector field according to the expected braiding angle data, and the expression of the braiding angle vector field is as follows:

[0100] ,

[0101] where represents the braiding angle direction vector on the th triangular patch, represents the clockwise yarn, represents the counterclockwise yarn, represents the projection vector of the center line on the th triangular patch, is the normal vector of the th triangular patch, is the expected braiding angle corresponding to the th triangular patch, is a generalized rotation matrix, and the expression of the generalized rotation matrix is as follows:

[0102] ,

[0103] where is the normal vector of the triangular patch along the direction, is the normal vector of the triangular patch along the direction, is the normal vector of the triangular patch along the direction, represents the meaning of rotation, , , are spatial coordinates.

[0104] S4. Optimize the expected fabric structure in different regions of the mandrel according to the braiding angle vector field.

[0105] Among them, S4 further includes the following steps:

[0106] S41. Generate the braiding angle reference lines of the clockwise yarn and the counterclockwise yarn according to the braiding angle vector field.

[0107] In one embodiment, first, observe the distribution and variation law of the braiding angle vector field to determine the inclination direction and angle of the yarn.

[0108] Further, use mathematical tools (such as vector analysis) to quantitatively analyze the braiding angle vector field and extract the angle information of the yarn.

[0109] Further, according to the inclination direction of the yarn, the yarn is divided into clockwise yarn and counterclockwise yarn. For the clockwise yarn, its angle vector should point to the clockwise part in the braiding angle vector field; for the counterclockwise yarn, its angle vector should point to the counterclockwise part.

[0110] Further, for the clockwise yarn, select a representative yarn as the reference line, and the angle vector of this yarn should be able to reflect the overall inclination direction of the clockwise yarn. Similarly, for the counterclockwise yarn, also select a representative yarn as the reference line, and the angle vector of this yarn should be able to reflect the overall inclination direction of the counterclockwise yarn. This reference line is used to ensure that the yarn trajectory fluctuates near the desired braiding angle after optimization to avoid performance differences.

[0111] It should be noted that when selecting the reference line, factors such as the position, length, and inclination angle of the yarn can be considered to ensure that the reference line can accurately reflect the arrangement and braiding structure of the yarn.

[0112] S42. Extract reference points through the braiding angle reference line, and the reference points are the intersections of the braiding angle reference line and the key plane of the reconstructed core mold.

[0113] In one embodiment, first, ensure that the braiding angle reference lines of the clockwise yarn and the counterclockwise yarn have been generated according to the braiding angle vector field.

[0114] Further, determine the key plane of the reconstructed core mold, and the key plane is an important geometric feature plane or functional plane on the core mold. The positions and directions of these planes can be obtained through CAD models or actual measurements.

[0115] Further, use mathematical methods (such as vector operations) for calculation to obtain the intersections of the braiding angle reference line and the key plane of the reconstructed core mold.

[0116] S43. Based on the position of the reference point and the perimeter of the key cross-section where it is located, re-divide the edge line of the key cross-section and obtain the division result.

[0117] In one embodiment, first, obtain the accurate coordinates of the reference point and the perimeter information of the key cross-section where it is located. This information should be accurate and complete for subsequent analysis and division.

[0118] Further, according to the shape and size of the key section and the position of the reference point, determine a suitable division strategy, which should take into account the requirements of subsequent analysis, design, or manufacturing to ensure the practicality and accuracy of the division result.

[0119] Further, according to the perimeter of the key section and the division strategy, calculate the positions of the division points. Among them, mathematical methods such as equidistant division and angular division are used to determine the specific positions of the division points.

[0120] Further, connect the calculated division points in sequence to form a new side line, which should have continuity and smoothness for subsequent analysis and use.

[0121] S44. Optimize the desired fabric structure on different regions of the core mold according to the division result.

[0122] In one embodiment, based on the division result obtained from the reference point and the perimeter of the key section, combined with step S3, determine the required fabric structure type according to the function and performance requirements of different regions of the core mold.

[0123] Further, optimize the fabric structure to improve its adaptability and performance, such as Figure 4 shown.

[0124] It should be noted that the purpose of optimization is to eliminate the uneven distribution of the yarn spacing between the inner and outer sides of the curvature.

[0125] S5. Infer and generate the eccentric weaving process parameters through the desired fabric structure.

[0126] Among them, S5 further includes the following steps:

[0127] S51. Obtain the speeds, trajectories, and postures corresponding to all yarns through the desired fabric structure.

[0128] In one embodiment, according to the desired fabric structure, solve the positions mapped in the spindle motion space for the desired trajectories on all patches corresponding to the discrete points , as shown. Among them, Figure 5 shown. Among them, , are the landing positions of two different yarns, , are coordinate points.

[0129] Further, extend the yarn trajectory on the patch along its optimized desired fabric direction, and the intersection point with the guide ring is , and form the midpoint position of the guide ring, and the intersection point with the spindle motion plane is 。

[0130] Further, extract the time required for deposition on adjacent patches of the same trajectory, the position and attitude of the guide ring.

[0131] Further, solve the traction speed of each yarn.

[0132] It should be noted that the moving speed of the spindle in each yarn is a definite value.

[0133] S52. Calculate the weighted average of the speed, the trajectory, and the attitude to obtain the eccentric weaving process parameters.

[0134] In one embodiment, the weighted average of the speeds, trajectories, and attitudes corresponding to all yarns is taken to obtain the weaving process parameters under eccentric weaving. The expression of the weaving process parameters is as follows:

[0135] ,

[0136] Wherein, is the traction speed corresponding to the yarn, is the weight value corresponding to the yarn, is the position of the center point of the guide ring, is the normal vector of the guide ring, is the traction speed under the eccentric weaving process, is the position of the weaving trajectory under the eccentric weaving process, is the attitude of the weaving trajectory under the eccentric weaving process, is the number of triangular patches on the clockwise yarn, represents the clockwise yarn, represents the counterclockwise yarn, , is the spatial coordinate.

[0137] Further, according to the expression of the weaving process parameters, the eccentric weaving process parameters are obtained.

[0138] In a specific embodiment, an experiment is carried out using the weaving complete set of equipment of Yunlu Composite Materials, which includes a 176-spindle weaving machine and a weaving attitude adjustment system composed of a KUKA robot equipped with a linear guide rail to verify the effectiveness of the eccentric weaving process inference method of the present invention. The experiment adopts Figure 6 the large-curvature special-shaped structural part shown in the figure. The upper half is the woven forming section, and the lower half is an auxiliary extension section designed for convenient clamping. Weaving operation is not performed on the lower half. The experiment also uses the un-twisted carbon fiber yarn of Zhongfu Shenying 12K T700 for weaving. The parameters of the weaving equipment are shown in Table 1.

[0139]

[0140] In this embodiment, first, the process parameters of centric vertical braiding are deduced using the traditional analytical method, then the process parameters of eccentric braiding are deduced using the eccentric braiding theory, and then braiding experiments are carried out using the two braiding process parameters.

[0141] Specifically, as Figure 6 shown, for the dark measurement section area on the mandrel, a comparison is made between the braiding angle measurement result and the coverage measurement result. The traction trajectory and traction speed obtained by using two methods are shown in Figure 7. Among them, the traction trajectory is represented by the relative movement of the guide ring and the mandrel, and the movement of the mandrel passing through the guide ring is converted into the movement of the guide ring passing through the mandrel.

[0142] From Figure 7 it can be seen that under the traditional centric vertical process, the traction trajectory is almost the same as the mandrel center line, and due to the existence of the convergence length, the trajectory is slightly longer than the mandrel center line. However, there are significant differences between the traction trajectory under the eccentric braiding process and the center line. The curvature of the trajectory changes to optimize the local fabric in the preform, and the overall trajectory is shifted upward by 38 mm. At the same time, due to the existence of the convergence distance, the eccentric braiding trajectory optimizes the initial convergence distance, and the braiding speed is relatively fast in the first half of the braiding process, accelerating the process of the yarn from the initial state to the deposition state, and gradually stabilizing at 4 mm / s in the second half, which is the same as the speed obtained by the traditional analytical method.

[0143] Braiding is carried out using the process parameters deduced by the two methods, and the fabric structure is as Figure 8 shown. The process parameters of centric vertical braiding deduced by the traditional analytical method are used for braiding based on the mandrel center line. Since the special-shaped structural part of the present invention is a large-curvature elbow, the deposition amount of the circumferential yarn on the mandrel is the same, resulting in an abnormal fabric structure under different surface area conditions. On the inner side of the curvature, due to the small surface area, the fabric shows extrusion and stacking phenomena; on the outer side of the curvature, due to the large surface area, the yarn is not enough to cover the mandrel completely, resulting in fabric voids. From Figure 7 it can be seen that under the centric vertical process, the braiding angles on the inner and outer sides vary in the range of 55° to 65°, which is relatively close to the expected braiding angle of 60°. However, there are obvious differences in the coverage rate, and the difference is more than 35%. The coverage rates on the inner and outer sides of the fabric of eccentric braiding are significantly improved, without fabric stacking and sparseness phenomena. The average difference in the coverage rates on the inner and outer sides is 10.9%, which is more than 24% lower than that of the traditional method. However, due to the non-uniform circumferential deposition of the fabric under the deposition mechanism, the accuracy of the braiding angle on the inner and outer sides of the curvature is reduced to a certain extent, and the maximum difference from the expected braiding angle appears on the outer side of the curvature.

[0144] Please refer to Figure 9 , Figure 9Schematic diagram of the weaving process inference system for special-shaped structural parts based on the eccentric theory in the embodiments of the present invention. The system includes an input device, a processor, an output device, and a memory. The input device, the processor, the output device, and the memory are interconnected. Among them, the memory is used to store computer programs, and the computer programs include program instructions. The processor is configured to call the program instructions, and the system uses the weaving process inference method for special-shaped structural parts based on the eccentric theory.

[0145] In this embodiment, the input device is used to input the basic parameters in the weaving process, including the traction speed, the eccentricity value, and the spatial position data on the surface of the core mold. The basic parameters are used to infer and generate the weaving process parameters.

[0146] The processor incorporates various mathematical algorithms, including the weaving angle algorithm under eccentric conditions, the weaving speed algorithm, the yarn landing position algorithm, the weaving angle vector field algorithm, the generalized matrix algorithm, and the weaving process parameter algorithm.

[0147] The output device uses a display screen to display the calculation results processed by the processor.

[0148] The memory uses a high-speed solid-state drive to store the basic parameters input by the input device and the calculation results processed by the processor. The memory features fast read and write speeds, large capacity, and high reliability, and can meet the requirements for storing large amounts of data.

[0149] In summary, in view of the problem that fabric defects are likely to occur at complex geometric features in the weaving of special-shaped structural parts, the present invention proposes a method and system for inferring weaving process parameters based on the eccentric mechanism. The method analyzes the influence mechanism of the eccentric process on the fabric forming of special-shaped structural parts, reveals the weaving principle and method for solving fabric defects, arranges the surface meshes on the special-shaped structural parts uniformly based on the mesh reconstruction model, proposes an optimization method for the weaving angle direction vector, and inversely infers the weaving trajectory and speed under the eccentric weaving process. The weaving process inference method proposed by the present invention is a new inference means different from the traditional analytical method, applicable to the mandrel of special-shaped structural parts, and is beneficial to improving the weaving forming quality. Through experimental verification, the process parameters inferred by the present invention can completely eliminate the fabric defects at the complex geometric features of special-shaped structural parts, and the difference in coverage rate between the inner and outer sides is reduced by more than 24%. It breaks through the weaving pose constraints of the traditional weaving process and provides a theoretical basis for the process planning software of the low-cost, fast and automated weaving production line for large-size special-shaped structural parts. The system can automatically generate eccentric weaving process parameters that meet the design requirements through accurate calculation and inference, greatly improving the accuracy and efficiency of the weaving process; comprehensively considering multiple factors such as the speed, trajectory and posture of the yarn, ensuring the uniform distribution and reasonable interweaving of the yarn during the weaving process, thereby improving the quality and performance of special-shaped structural parts; having high flexibility and scalability, and being able to quickly adjust the process parameters according to different design requirements, providing strong technical support for the manufacturing of special-shaped structural parts.

[0150] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and the description of the present invention.

Claims

1. A reasoning method for the braiding process of special-shaped structural parts based on the eccentric theory, characterized in that, The method includes the following steps: Obtain a three-dimensional model of the core mold of the special-shaped structural member; Using the three-dimensional model, obtain the uniform surface mesh of the key cross-section of the core mold; the obtaining the uniform surface mesh of the key cross-section of the core mold by using the three-dimensional model includes: extracting point cloud data by using the three-dimensional model; performing orthogonal projection on the point cloud data to obtain the center line of the special-shaped structural member; reconstructing the key cross-section of the core mold by using the spatial relationship between the center line and the point cloud data; connecting the positions of the key cross-sections through a custom call sequence to generate a uniform surface mesh; Based on the eccentric braiding theory and the uniform surface mesh, obtain the braiding angle vector field; the obtaining the braiding angle vector field based on the eccentric braiding theory and the uniform surface mesh includes: establishing a spatial relationship equation according to the positions of the yarns on the guide ring and the landing positions on the core mold under the eccentric braiding process; performing a time differential operation on the spatial relationship equation to obtain a braiding speed expression; obtaining a yarn landing position expression according to the braiding speed expression; obtaining the braiding angle vector field based on the yarn landing position expression and the uniform surface mesh; the obtaining the braiding angle vector field based on the yarn landing position expression and the uniform surface mesh includes: designing the braiding performance based on the yarn landing position expression and the uniform surface mesh; obtaining the desired braiding angle according to the design result of the braiding performance; obtaining the braiding angle vector field according to the desired braiding angle; the expression of the braiding angle vector field is as follows: Among them, represents the knitting angle direction vector on the th triangular patch, represents the clockwise yarn, represents the counterclockwise yarn, represents the projection vector of the center line on the th triangular patch, is the normal vector of the th triangular patch, is the expected knitting angle corresponding to the th triangular patch, is the generalized rotation matrix; the spatial relationship equation is as follows: The braiding speed expression is as follows: The yarn landing position expression is as follows: Among them, is the angle of the yarn landing point in the core mold cross-section coordinate system, is the angle of the intersection point of the yarn and the guiding ring in the guiding ring coordinate system, is the eccentricity value, is the core mold radius, is the braiding speed of the yarn, is the guiding ring radius, is the braiding speed of the spindle speed mapped on the core mold surface, is the traction speed, is the braiding time, indicates that the braiding time is the yarn landing point position at this time, is a constant; According to the braiding angle vector field, optimize the desired fabric structure in different regions of the core mold; the optimizing the desired fabric structure in different regions of the core mold according to the braiding angle vector field includes: generating the braiding angle reference lines of the clockwise yarns and the counterclockwise yarns according to the braiding angle vector field; extracting the reference points through the braiding angle reference lines, and the reference points are the intersection points of the braiding angle reference lines and the reconstructed key plane of the core mold; re-divide the side lines of the key cross-section based on the positions of the reference points and the perimeters of the key cross-sections where they are located to obtain a division result; optimize the desired fabric structure in different regions of the core mold according to the division result; Generate the eccentric braiding process parameters by reasoning through the desired fabric structure; the generating the eccentric braiding process parameters by reasoning through the desired fabric structure includes: obtaining the speeds, trajectories, and postures corresponding to all the yarns through the desired fabric structure; performing a weighted average calculation on the speeds, the trajectories, and the postures to obtain the eccentric braiding process parameters; the eccentric braiding process parameters satisfy the following expression: Among them, is the drawing speed corresponding to the yarn, is the weight value corresponding to the yarn, is the position of the center point of the guide ring, is the normal vector of the guide ring, is the drawing speed under the eccentric braiding process, is the position of the braiding trajectory under the eccentric braiding process, is the attitude of the braiding trajectory under the eccentric braiding process, is the number of triangular patches on the clockwise yarn, represents the clockwise yarn, represents the counterclockwise yarn, , is the spatial coordinate.

2. A weaving process inference system for special-shaped structural parts based on the eccentricity theory, the system uses a weaving process inference method for special-shaped structural parts based on the eccentricity theory described in claim 1, characterized in that, The system includes an input device, a processor, an output device, and a memory. The input device, the processor, the output device, and the memory are interconnected. Among them, the memory is used to store a computer program, the computer program includes program instructions, and the processor is configured to call the program instructions.

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