General braiding simulation method and system for special-shaped structural parts based on model reconstruction algorithm

Abstract

The present invention relates to the technical field of knitting processes, and particularly relates to a general knitting simulation method and system for special-shaped structural parts based on a model reconstruction algorithm. The method comprises the following steps: obtaining three-dimensional model data of the core mold of the special-shaped structural part; extracting the center line of the core mold through the three-dimensional model data; obtaining the key cross-sections of the core mold according to the center line; reconstructing the surface mesh of the three-dimensional model of the core mold by using the key cross-sections; generating a yarn topological trajectory based on kinematic characteristics by using the surface mesh; and generating a fabric structure according to the yarn topological trajectory. By means of the model reconstruction algorithm and the kinematic method, the present invention effectively eliminates redundant features of the core mold of complex special-shaped structural parts, greatly improves the accuracy and efficiency of knitting simulation; the error from the knitting experiment measurement result does not exceed 5°, meeting the requirements of actual production, and can be used to verify the process design scheme in actual production, reducing the high costs brought by sample trial production.

Description

Technical Field

[0001] The present invention relates to the technical field of braiding processes, and particularly to a general braiding simulation method and system for special-shaped structural parts based on a model reconstruction algorithm. Background Art

[0002] The three-dimensional braiding process adjusts the braiding in real time according to the shape of the mandrel, and realizes the synchronous braiding of a large number of yarns into an integral net-shaped preform. It is an optimal method for forming special-shaped structural parts. However, complex features make it impossible to establish a high-precision fabric model, and it is difficult to realize the simulation verification of braiding process parameters and performance simulation. Therefore, the high-precision simulation of the braiding process of special-shaped structural parts has become a current research hotspot.

[0003] In the prior art, the finite element method, the geometric model analysis method, and the kinematic method are usually adopted to simulate the braiding process of special-shaped structural parts. Among them, the finite element method accurately simulates the behavior and response of the braiding process through multi-scale analysis of the braiding process of yarns; the geometric model analysis method establishes a definite non-linear equation set for the geometric function of the mandrel shape and the position of the yarns, so as to simulate and analyze the yarn landing position; the kinematic method provides detailed information on the braiding state in real time through kinematic analysis. However, the finite element method takes a long time to simulate, the geometric model analysis method has a low simulation accuracy for special-shaped structural parts, and the kinematic method has high requirements for the surface mesh of the mandrel. Therefore, there is an urgent need to propose a fast, highly applicable braiding process simulation method that is applicable to complex special-shaped structural parts.

[0004] Currently, there is not much research work on high-precision simulation methods for complex special-shaped structural parts, and there is no specific general braiding simulation method for special-shaped structural parts based on a model reconstruction algorithm. Summary of the Invention

[0005] Aiming at the deficiencies in the prior art, the present invention provides a general braiding simulation method and system for special-shaped structural parts based on a model reconstruction algorithm.

[0006] In a first aspect, a general weaving simulation method for special-shaped structural members based on a model reconstruction algorithm provided by the present invention includes the following steps: obtaining three-dimensional model data of the core mold of the special-shaped structural member; extracting the center line of the core mold through the three-dimensional model data; obtaining key cross-sections of the core mold according to the center line; reconstructing the surface mesh of the three-dimensional model of the core mold by using the key cross-sections; generating a yarn topological trajectory based on kinematic characteristics by using the surface mesh; and generating a fabric structure according to the yarn topological trajectory. By accurately obtaining the three-dimensional model data of the core mold of the special-shaped structural member, the present invention provides high-quality input for subsequent steps, ensuring the accuracy of the simulation results; by extracting the center line and key cross-sections and reconstructing the surface mesh of the three-dimensional model accordingly, the present invention realizes the accurate capture and expression of the complex shape of the special-shaped structural member, enhancing the flexibility and adaptability of the simulation; the process of generating the fabric structure not only ensures the rationality and continuity of the yarn movement, but also provides strong technical support for the weaving of special-shaped structural members.

[0007] Optionally, the extracting the center line of the core mold through the three-dimensional model data includes: constructing a center line space curve equation; and substituting the three-dimensional model data into the center line space curve equation to obtain the trajectory of the center line. The center line space curve equation constructed by the present invention realizes the accurate description of the center line of the core mold, making the extraction process of the center line more scientific and rigorous; by substituting the three-dimensional model data into the center line space curve equation, the trajectory of the center line is directly calculated, greatly improving the weaving simulation accuracy; the obtained center line trajectory has high accuracy, providing reliable data support for subsequent key cross-section acquisition and surface mesh reconstruction.

[0008] Optionally, the obtaining key cross-sections of the core mold according to the center line includes: obtaining the center line normal plane according to the trajectory of the center line; and reconstructing the key cross-sections of the core mold based on the intersection of the center line normal plane and the original mesh patches. By using the center line normal plane, the present invention accurately locates the cross-sectional shape of the core mold at different positions, ensuring the accuracy of key cross-section extraction; by using the intersection of the center line normal plane and the original mesh patches for cross-section reconstruction, not only the geometric features of the original mesh are retained, but also the complex shape of the core mold is meticulously depicted, improving the simulation accuracy; the obtained key cross-sections not only have good continuity, but also can truly reflect the structural features of the core mold at different cross-sections, providing an important reference basis for subsequent surface mesh reconstruction and yarn topological trajectory generation.

[0009] Optionally, the key cross-section of the core mold reconstructed based on the intersection of the centerline normal plane and the original mesh patch includes: extracting the outermost contour points based on the intersection of the centerline normal plane and the original mesh patch to form an ordered contour point set; reconstructing the key cross-section of the core mold according to the ordered contour point set. By extracting the outermost contour points, the present invention ensures that the outer contour shape of the key cross-section is consistent with the original mesh, improving the simulation fidelity; forming the extracted contour points into an ordered point set effectively avoids data chaos and reconstruction errors; reconstructing the cross-section according to the ordered contour point set generates a smooth and continuous key cross-section, which not only retains the geometric features of the core mold but also enhances the practicality and reliability of the simulation.

[0010] Optionally, using the key cross-section to reconstruct the surface mesh of the three-dimensional core mold model includes: using the key cross-section to obtain the number and positions of the reconstructed patch corner points; reconstructing the surface mesh of the three-dimensional core mold model according to the number and positions of the reconstructed patch corner points. By accurately obtaining the number and positions of the reconstructed patch corner points through the key cross-section, the present invention ensures the accuracy and integrity of the surface mesh reconstruction, enabling the reconstructed three-dimensional model to truly reflect the geometric shape of the core mold; using the accurate parameters of the reconstructed patch for mesh reconstruction effectively avoids mesh distortion and topological errors, improving the accuracy and fidelity of the three-dimensional model; the generated surface mesh of the three-dimensional model not only has good continuity but also has high smoothness and detail expressiveness, providing a reliable basis for subsequent applications and analyses.

[0011] Optionally, using the surface mesh to generate the topological trajectory of the yarn based on kinematic characteristics includes: using the surface mesh to judge the deposition state of the yarn based on kinematic characteristics to obtain a judgment result; generating the topological trajectory of the yarn based on the judgment result. By accurately judging the deposition state of the yarn, the present invention accurately analyzes the dynamic behavior of the yarn during the weaving process, providing a basis for generating a real yarn trajectory; based on the judgment result of the yarn deposition state, the continuity and rationality of the yarn trajectory during the weaving process are ensured; the generated topological trajectory of the yarn not only meets the requirements of the weaving process but also accurately reflects the distribution of the yarn on the three-dimensional model surface, providing a reliable basis for subsequent fabric structure generation.

[0012] Optionally, generating a fabric structure according to the yarn topological trajectory includes: obtaining the interweaving pattern of the yarn according to the yarn topological trajectory and using the interweaving relationship matrix; based on the interweaving pattern, performing secondary processing on each interweaving point on the surface of the core mold to form the spatial topology of the yarn; and generating a fabric structure using the elliptical cross-section and the spatial topology of the yarn. By accurately capturing the interweaving pattern of the yarn through the interweaving relationship matrix, the present invention ensures the accuracy and authenticity of the fabric structure, enabling the generated fabric structure to precisely reflect the mutual relationship and arrangement of the yarns; performing secondary processing on each interweaving point forms an accurate topological structure of the yarn in three-dimensional space, further enhancing the three-dimensional sense and detail expressiveness of the fabric structure; the combination of the elliptical cross-section and the yarn spatial topology not only simulates the actual shape of the yarn but also endows the fabric structure with more flexibility and diversity, making the generated fabric structure more in line with actual application requirements and providing a solid foundation for subsequent fabric simulation and analysis.

[0013] Optionally, the interweaving relationship matrix includes: an interweaving relationship matrix with a period of 2 interweaving points for the same interweaving situation on the same yarn in the spindle arrangement of the diamond weaving structure; an interweaving relationship matrix with a period of 4 interweaving points for the same interweaving situation on the same yarn in the spindle arrangement of the conventional weaving structure. By defining the interweaving relationship matrix with a period of 2 interweaving points in the diamond weaving structure, the present invention realizes the accurate capture and expression of the characteristics of the diamond weaving structure; by defining the interweaving relationship matrix with a period of 4 interweaving points in the conventional weaving structure, the stability and regularity of the fabric structure are ensured; through the two interweaving relationship matrices, not only the diversity of the fabric structure is enriched, but also flexible choices are provided for different weaving requirements.

[0014] Optionally, the secondary processing includes: at the interweaving point where the matrix content is 1, shifting the clockwise yarn along the normal vector of the surface of the core mold by twice the yarn thickness and the counterclockwise yarn by one time the yarn thickness; at the interweaving point where the matrix content is 0, shifting the counterclockwise yarn along the normal vector of the surface of the core mold by twice the yarn thickness and the clockwise yarn by one time the yarn thickness. By performing different-direction yarn shifting processing on the interweaving points with matrix contents of 1 and 0, the present invention realizes the accurate spatial positioning of the yarn at the interweaving points, avoiding overlap and conflict between the yarns and making the fabric structure clearer and more three-dimensional; the different settings of the clockwise and counterclockwise yarn shift amounts fully consider the kinematic characteristics and weaving rules of the yarn during the interweaving process, ensuring the stability and uniformity of the fabric structure; through the secondary processing method, not only the simulation accuracy of the fabric structure is improved, but also more accurate data support is provided for subsequent fabric processing and manufacturing, contributing to the improvement of the quality and performance of fabric products.

[0015] In a second aspect, the present invention provides a general braiding simulation system for special-shaped structural members based on a model reconstruction algorithm. 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, the processor is configured to call the program instructions, and the system uses the general braiding simulation method for special-shaped structural members based on the model reconstruction algorithm. The system provided by the present invention efficiently and accurately simulates the braiding process of special-shaped structural members, greatly improving the efficiency and accuracy of design and production, and reducing the trial-and-error cost; through the model reconstruction algorithm, the system flexibly responds to special-shaped structural members of various complex shapes, realizing the universality and scalability of braiding simulation, and meeting the needs of different industries and fields; the generated braiding simulation results have a high degree of realism and credibility, providing strong data support for subsequent process optimization, product design, and market analysis, and promoting the innovation and development of the braiding technology for special-shaped structural members.

[0016] Compared with the prior art, the beneficial effects of the present invention include: through the model reconstruction algorithm, redundant features of the core mold, such as through holes and bosses, are automatically identified and eliminated, greatly improving the braiding simulation accuracy; through the kinematic method, the calculation time of braiding simulation is reduced, thus greatly improving the braiding simulation efficiency; based on the reconstructed grid and yarn trajectory, the interwoven spatial structure of the fabric is generated, realizing high-fidelity modeling and performance analysis of the fabric; the error between the simulation result and the measurement result of the braiding experiment does not exceed 5°, meeting the requirements of actual production. Brief Description of the Drawings

[0017] Figure 1 It is a flowchart of the general braiding simulation method for special-shaped structural members based on the model reconstruction algorithm according to an embodiment of the present invention;

[0018] Figure 2 It is a schematic diagram of the core mold feature filtering process according to an embodiment of the present invention;

[0019] Figure 3 It is a schematic diagram of the patch combination method and its index number according to an embodiment of the present invention;

[0020] Figure 4 It is a schematic diagram of the reconstructed surface grid of the core mold according to an embodiment of the present invention;

[0021] Figure 5 It is a schematic diagram of the braiding process according to an embodiment of the present invention;

[0022] Figure 6 It is a schematic diagram of the braiding simulation after relative motion conversion according to an embodiment of the present invention;

[0023] Figure 7Schematic diagram of fabric structures under different spindle arrangements according to embodiments of the present invention;

[0024] Figure 8 Schematic diagram of the generation process of a single yarn entity unit according to embodiments of the present invention;

[0025] Figure 9 Schematic diagram of the geometric dimensions of the core mold according to embodiments of the present invention;

[0026] Figure 10 Schematic diagram of the fabric spatial structure according to embodiments of the present invention;

[0027] Figure 11 Schematic diagram of the comparison between the simulated woven fabric and the actual woven fabric according to embodiments of the present invention;

[0028] Figure 12 Schematic diagram of the comparison of the weaving angles between the simulated weaving and the actual weaving according to embodiments of the present invention;

[0029] Figure 13 Schematic diagram of the general weaving simulation system structure of special-shaped structural parts based on the model reconstruction algorithm according to embodiments of the present invention. Detailed implementation manners

[0030] 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 do not 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 be practiced with 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.

[0031] Throughout the specification, the reference to "an embodiment", "embodiment", "an example" or "example" 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 "example" 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 the diagrams are not necessarily drawn to scale.

[0032] Please refer to Figure 1 , embodiments of the present invention provide a general weaving simulation method for special-shaped structural parts based on the model reconstruction algorithm, and the method includes the following steps:

[0033] S1. Obtain the three-dimensional model data of the core mold of the special-shaped structural part.

[0034] In one embodiment, a three-dimensional scanner is used to scan the physical object of the core mold of the special-shaped structural member to obtain high-precision point cloud data.

[0035] Furthermore, preprocess the point cloud data to improve the data quality; the preprocessing includes denoising and registration.

[0036] Furthermore, in CAD software, according to the point cloud data, use modeling tools to create a three-dimensional model.

[0037] Furthermore, verify the three-dimensional model, check whether its dimensions, shape, and function meet the design requirements, and optimize the model according to the verification results to ensure the accuracy and reliability of the model.

[0038] Furthermore, export the optimized three-dimensional model data for subsequent analysis.

[0039] S2. Extract the center line of the core mold through the three-dimensional model data.

[0040] Among them, S2 further includes the following steps:

[0041] S21. Construct the center line space curve equation.

[0042] Optimizing the complex redundant features such as holes, flanges, concave corners, and hollows of the core mold grid is a necessary preprocessing process for finite element simulation, kinematic solution, and dynamic solution. Among them, the center line is the central reference for reconstructing the core mold grid, and its length interval corresponds to the length segmentation of the core mold.

[0043] In one embodiment, based on the core mold end face coordinate system , the projection contour boundary of the plane, solve and synthesize the center line and the traction trajectory, and the modeling reference and attitude of the used mandrel three-dimensional model are uniformly extended along the origin to the axis.

[0044] Specifically, project the contour boundary of the mandrel onto the , plane, as shown in Figure 2 (A); then, through the cubic curve interpolation algorithm and the curve fitting algorithm, fit and solve the curve of the contour boundary, and the mandrel contour and the boundary curve are as shown in Figure 2 (B). Figure 2 (B1) and Figure 2 (B2) represent the algorithm features of the contour section. Among them, represents the th point on the center line, represents the tangent vector of the th point on the center line, Represents the central axis normal plane, Represents the original mesh patch.

[0045] Furthermore, take a point on the upper and lower boundary curves and intersect them along their respective normal directions. When the length of the line connecting the two points is equal, it is the discrete point of the central axis.

[0046] Furthermore, take the value of the traction step size , and give , The plane curve equation is as follows:

[0047] ,

[0048] Furthermore, use the plane curve equation to synthesize the central axis space curve equation. Among them, during the synthesis process, use the two-dimensional line point-direction form to solve for the intersection point The two-dimensional line point-direction form is as follows:

[0049] ,

[0050] Among them, The coordinates of are , The coordinates of are , The coordinates of are , The coordinates of are . In this two-dimensional line point-direction form, when the lengths of line segment and line segment are equal and the included angle is obtuse, is on the central axis, and the corresponding point coordinates are recorded as the unordered discrete points of the central axis . The synthesized central axis space curve equation is in the following form:

[0051] ,

[0052] Among them, Represents the central axis space curve trajectory corresponding to the th traction step size, Is the traction step size, Is the maximum length of the central axis, Is The space curve equation of the plane, Is The space curve equation of the plane.

[0053] S22. Substitute the three-dimensional model data into the central axis space curve equation to obtain the trajectory of the central axis.

[0054] In one embodiment, the three-dimensional model data obtained in step S1 is substituted into the centerline space curve equation to obtain the complete trajectory of the centerline.

[0055] S3. Obtain the key cross-sections of the core mold according to the centerline.

[0056] Among them, S3 further includes the following steps:

[0057] S31. Obtain the centerline normal plane according to the trajectory of the centerline.

[0058] In one embodiment, for each point in the centerline trajectory, calculate its tangent vector, which is obtained by differentiating the parametric equation of the centerline trajectory or approximated by the vector difference between adjacent points.

[0059] Furthermore, for each point in the centerline trajectory, construct a plane that passes through this point and whose normal vector is perpendicular to the tangent vector, which is the normal plane of the centerline at this point.

[0060] S32. Obtain the key cross-sections of the core mold based on the intersection of the centerline normal plane and the original mesh patches.

[0061] In one embodiment, first, use the centerline normal plane and the original mesh patches The intersection of them is used as the dense cross-section point set. Among them, the dense cross-section point set of the centerline normal plane and the original mesh patches satisfies the following equation:

[0062] ,

[0063] Among them, , , are the point coordinates in the centerline normal plane; , , are the normal vector coordinates in the centerline normal plane, , is the ordinal number of the normal vector coordinates.

[0064] Furthermore, extract the outermost contour points to form an ordered contour point set, filter out redundant features such as holes, concave corners, and hollows, and form the key cross-sections of the reconstructed mesh. The key cross-sections are determined by two intersecting space lines and The space lines and satisfy the following equations:

[0065] ,

[0066] Among them, , , is the ordinal number of the corner coordinates of the triangular patch.

[0067] S4. Use the key section to reconstruct the surface mesh of the core mold three-dimensional model.

[0068] Among them, S4 further includes the following steps:

[0069] S41. Use the key section to obtain the number and position of the corner points of the reconstructed patch.

[0070] In one embodiment, first, the number of corner points is determined by using the key section ordered contour point set.

[0071] Furthermore, the points corresponding to the serial numbers of adjacent key sections are sequentially combined to form the corner point sequences and normals of multiple groups of patches, as Figure 3 shown. Among them, Figure 3 (A) is the corresponding diagram of the patch index number and the corner point sequence. A4.5 and A4.6 are the patch index numbers, and the edge black dots represent the corner points. Figure 3 (B) represents the patch situation corresponding to the patch index number A4.5. In Figure 3 , the patch index number of A1.7 is odd, and its corner point sequence is (P1.6, P1.5, P2.5), corresponding to Figure 3 (A) in; the patch index number of A1.8 is even, and its corner point sequence is (P1.6, P2.5, P2.6), corresponding to (B) in Figure 3; the patches are distributed clockwise along each segment according to the index numbers A0.0, A0.1, A0.2... A1.0, A1.1, A1.2... It is set that there are 48 patches in each grid segment (such as the patch set between S1 - S2), and there are 24 patch corner points on each key section.

[0072] Furthermore, according to the ordered contour point set with index relationship, obtain the coordinate positions of the corner points on the triangular patch, in the following form:

[0073]

[0074] Among them, represents the corner point coordinates on the triangular patch; is the corner point ordinal number, is the corner point coordinate.

[0075] S42. Reconstruct the surface mesh of the core mold three-dimensional model according to the number and position of the corner points of the reconstructed patch.

[0076] In one embodiment, determine the positions of all patches in space according to the number and position of the corner points of the reconstructed patch.

[0077] Further, all the patches are combined together to reconstruct the surface mesh of the core mold three-dimensional model, as Figure 4 shown. Its surface topological structure is tangentially distributed uniformly around the center line, and the arrangement order corresponds to the patch index number. Adjacent patches can be directly called through the patch index number, which is the key to the rapid iterative method of process design; the reconstructed mesh removes redundant features such as holes, edges, and hollows in the STL native mesh, overcomes the disordered and uneven patch distribution, but cannot directly call adjacent patches, resulting in a reduction in the iterative efficiency of the yarn trajectory prediction algorithm.

[0078] S5. Using the surface mesh, generate the yarn topological trajectory based on kinematic characteristics.

[0079] Among them, S5 further includes the following steps:

[0080] S51. Using the surface mesh, judge the deposition state of the yarn based on kinematic characteristics to obtain a judgment result.

[0081] Please refer to Figure 5 . During the knitting process using a radial knitting machine, two groups of spindles carrying bobbins are respectively placed at the corresponding notches on the dial, and the gear drives the dial, and the dial drives the spindles to move clockwise and counterclockwise along the serpentine track on the chassis of the knitting machine, and the yarns are continuously intertwined to form a mesh structure. At the same time, the robot in the core mold attitude adjustment system grips the core mold through the guide ring. Among them, the highly intertwined yarns cover the surface of the core mold on the forming plane after passing through the convergence distance.

[0082] During the knitting process, a large number of yarns are simultaneously formed on the surface of the core mold. To simplify the knitting simulation and improve the operation efficiency, the present invention ignores the interaction relationship between the yarns and the meandering movement of the spindles, describes the guide ring as a circular coil with a radius of , and describes the knitting equipment as a circular coil with a radius of . At the same time, to reduce the huge computational amount brought by updating the model data after each knitting attitude transformation, after reading the surface mesh data of the reconstructed core mold model, the present invention sets the core mold as a fixed reference system, and the spindles on the chassis make a helical movement according to the traction trajectory. Among them, the helix generated by the helical movement satisfies the following expression:

[0083] ,

[0084] Among them, is the spatial position information of the th spindle on the helix at time . The number of clockwise and counterclockwise spindles is both represented by ; is the position information of the center point of the knitting machine chassis at time ; is the normal vector of the knitting machine chassis plane at a moment; is in the core mold end face coordinate system the direction vector of the axis, with the direction pointing inside the core mold, is at a moment, the th spindle's angular position information on the chassis. Specifically as Figure 6 shown. Among them, represents the clockwise yarn, represents the counterclockwise yarn, , , represent the spatial coordinates.

[0085] In one embodiment, the deposition process of the yarn landing point on the surface of the core mold is described mathematically. The yarn starts from the yarn outlet and passes through the guiding ring. When passing through the guiding ring, the yarn direction is forced to bend to form a convergence area and finally lands on the surface of the core mold. Due to the uneven distribution of the yarn during the process of knitting a non-circular core mold, the circumferential movement speed of the yarn on the guiding ring is not equal to the knitting speed. Therefore, it is necessary to determine the intersection point of the yarn and the guiding ring according to the geometric relationship, and its expression is as follows:

[0086] ,

[0087] where, is at a moment, the intersection point of the yarn corresponding to the th spindle and the guiding ring, is at a moment, the projection point position information of the yarn landing point corresponding to the th spindle on the plane where the guiding ring is located, is at a moment, the projection point position information of the th spindle on the plane where the guiding ring is located, is the projection of the yarn landing point described in the guiding ring coordinate system on the plane of the guiding ring coordinate system, is the projection of the yarn landing point position and the spindle position described in the guiding ring coordinate system on the plane of the guiding ring coordinate system, is the angle formed between the contact point, the midpoint of the guiding ring and the landing point in the plane of the guiding ring coordinate system, and its expression is as follows:

[0088] ,

[0089] where, is the position of the knitting trajectory at a moment.

[0090] Further, the deposition state of each yarn is judged. According to the intersection point of the yarn and the guiding ring , the yarn landing point and the triangular mesh normal vector of the core mold surface where the landing point is located , the yarn state is judged and analyzed. When the yarn is located below the corresponding triangular mesh, it is defined that the yarn is deposited on the core mold surface to form a fabric. The conditional expression for forming the fabric is as follows:

[0091] ,

[0092] S52. Based on the judgment result, generate the topological trajectory of the yarn.

[0093] In one embodiment, based on the judgment result of the deposition state of each yarn, the topological trajectory of the yarn deposited on the core mold surface is generated.

[0094] S6. Generate the fabric structure according to the topological trajectory of the yarn.

[0095] Among them, S6 further includes the following steps:

[0096] S61. According to the topological trajectory of the yarn, use the interweaving relationship matrix to obtain the interweaving form of the yarn.

[0097] To achieve high-precision modeling and performance analysis of the subsequent composite materials, it is necessary to establish the interweaving structure of the fabric covering the outside of the core mold. The interweaving structures of knitting are mainly divided into two types, namely, the diamond knitting structure and the conventional knitting structure. The knitting structure is closely related to the arrangement mode of the spindles. The relationship between the two fabric structures and the spindle arrangement is shown in Fig. 7, Figure 7 (a) shows the relationship between the diamond knitting structure and the spindle arrangement, Figure 7 (b) shows the relationship between the conventional knitting structure and the spindle arrangement.

[0098] In the spindle arrangement of the diamond knitting structure, the interweaving of the clockwise spindles and the counterclockwise spindles is single and has strong periodicity. Since the period of the same interweaving situation on the same yarn is 2 interweaving points, according to the movement form of the dial, the interweaving points formed by the clockwise spindles and the counterclockwise spindles with different parity sequences are of one form of interweaving points, which is defined as the clockwise yarn on the top and the counterclockwise yarn on the bottom in the present invention. On the contrary, the interweaving points formed by the clockwise spindles and the counterclockwise spindles with the same parity sequence are of another form, which is defined as the clockwise on the bottom and the counterclockwise on the top in the present invention.

[0099] In one embodiment, for the convenience of calculation, the spatial position of the interweaving point is described in matrix form, and the interweaving relationship is defined as The interlacing relationship matrix. The interlacing state with the clockwise yarn on top and the counterclockwise yarn at the bottom is defined as 1 in the interlacing relationship matrix, and the interlacing state with the clockwise yarn at the bottom and the counterclockwise yarn on top is defined as 0. The interlacing relationship matrix in the spindle arrangement of the diamond weaving structure has the following expression:

[0100] ,

[0101] In the spindle arrangement of the conventional weaving structure, the interlacing pattern of the clockwise spindles and the counterclockwise spindles is more complex than that of the diamond weaving structure, and the period of the same interlacing situation on the same yarn is 4. Therefore, it is necessary to discuss the spindles of four serial numbers separately. The interlacing form under conventional weaving is two over two under. Therefore, according to the spindle arrangement order, the interlacing relationship matrix has the following expression:

[0102]

[0103] Furthermore, based on the above interlacing relationship matrix, the interlacing pattern of the yarn is initially generated.

[0104] S62. Based on the interlacing pattern, perform secondary processing on each interlacing point on the surface of the core mold to form the spatial topology of the yarn.

[0105] In one embodiment, based on the interlacing pattern, perform secondary processing on each interlacing point on the surface of the core mold to form the spatial topology of the yarn. The secondary processing includes:

[0106] At the interlacing point where the matrix content is 1, offset the clockwise yarn by twice the yarn thickness along the normal vector of the surface of the core mold where it is located, and offset the counterclockwise yarn by one time the yarn thickness;

[0107] At the interlacing point where the matrix content is 0, offset the counterclockwise yarn by twice the yarn thickness along the normal vector of the surface of the core mold where it is located, and offset the clockwise yarn by one time the yarn thickness.

[0108] S63. Use the elliptical cross-section and the spatial topology of the yarn to generate the fabric structure.

[0109] In one embodiment, use the elliptical cross-section and the spatial topology of the yarn to generate the solid unit of a single yarn, as Figure 8 shown. Figure 8 Shows the generation process of the fabric spatial structure.

[0110] For the braiding simulation method of the present invention, in one embodiment, simulation experiments were carried out using Matlab R2023b software, and the calculations were performed on a computer equipped with an Intel(R) Core(TM) i9-14900HX processor, an NVIDIA GeForce RTX4070 graphics card, 32GB of RAM, and a Windows11 operating system. During the actual braiding process, the yarn is tied tightly at the starting section of the mandrel using a binding tape. Therefore, the starting points of the yarn are evenly distributed on the end face of the mandrel, and the initial landing points of the yarn in the simulation model are the intersections of the connection line between the midpoints of the spindle and the mandrel end face and the contour line. Among them, the geometric dimensions of the mandrel are as Figure 9 shown. Through this experiment, the generated fabric spatial structure is as Figure 10 shown.

[0111] In the braiding experiment, a Yunlu Composite 176-spindle radial braiding machine and a KUKA six-degree-of-freedom industrial robot KR 240 R2700-prime installed on a linear guide were used. Each spindle in the radial braiding machine moves forward along the track of the braiding machine chassis, and the yarn is carried by the yarn bobbin installed on the spindle for braiding. At the same time, the motion system of the braiding machine consists of 4 servo motors, 2 vibration motors, and their controllers. The braiding equipment parameters are shown in Table 1.

[0112]

[0113] It can be seen from Figure 11 that through the reconstruction grid algorithm and braiding simulation method proposed by the present invention, the braiding process under any braiding process parameters has been accurately simulated, and there is a good consistency between the fabric structure and the actual braiding structure. The braiding angles of the simulated braiding and the actual braiding were compared, as Figure 12 shown. Due to the influence of the initial convergence distance, there is a certain delay in the change of the braiding angle in the initial stage. It can be seen from Figure 12 that the fabric distribution is relatively complex in the initial section of the mandrel, and the braiding angle shows a trend of first decreasing, then increasing, and finally becoming relatively stable. Since the cross-sectional shape of the mandrel changes from a circular cross-section to a quasi-rectangular cross-section, the error between the simulated braiding and the actual braiding of the braiding angle gradually increases. In the circular cross-section part, since the yarn is tangent to the mandrel in the time series, the influence of the interaction force between the yarns on the prediction result of the braiding angle is not considered. However, in the actual braiding process of the quasi-rectangular cross-section, due to the interaction between the yarns, there is a phenomenon of early deposition of the fabric, so there is a prediction error. According to the measurement results, the error can be guaranteed to be within 5°, so it meets the requirements of the actual working conditions.

[0114] Please refer to Figure 13 , Figure 13Schematic diagram of the general braiding simulation system for special-shaped structural parts based on the model reconstruction algorithm 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 general braiding simulation method for special-shaped structural parts based on the model reconstruction algorithm.

[0115] In this embodiment, the input device is mainly used to input braiding data information, and the braiding data information includes braiding process parameters, shape and size information of special-shaped structural parts, and types of braiding materials. Through the input device, not only can the required braiding process parameters and relevant information of special-shaped structural parts be conveniently input, but also instructions can be sent to the system, such as starting braiding simulation and adjusting process parameters.

[0116] The processor is the core part of the system, including various types of computing units, such as a central processing unit and a graphics processing unit, to support complex computing tasks; the processor is mainly used to execute the model reconstruction algorithm, process the input braiding data information, and generate corresponding braiding simulation results;

[0117] The output device uses a display screen to display the results processed by the processor to the user. The results include the image of braiding simulation and detailed data during the braiding process.

[0118] The memory uses a high-speed solid-state drive, which has the characteristics of fast read and write speed, large capacity, and high reliability, and can meet the needs of storing a large amount of data. It is used to store the braiding data information input by the input device and the results processed by the processor.

[0119] In summary, the present invention proposes a novel braiding process simulation method based on the model reconstruction algorithm for special-shaped structural parts of any shape. Among them, the model reconstruction algorithm can automatically identify and eliminate redundant features such as through holes and bosses of the core mold that affect the fabric prediction accuracy, ensuring the braiding simulation accuracy and efficiency. At the same time, based on the reconstructed grid and yarn trajectory, the intertwined spatial structure of the fabric is generated, facilitating high-fidelity modeling and performance analysis of the fabric. Based on the kinematic characteristics, the present invention greatly improves the calculation speed on the basis of ensuring accuracy, and the calculation time for special-shaped structural parts is much less than that of commercial finite element software. Through experimental verification with an aircraft inlet, the error between the braiding angle extracted from the circular cross-section part and the measured value is extremely small. In the variable cross-section part, due to the fact that the present invention does not consider the interaction relationship between yarns, the error value increases significantly, but it can still be guaranteed to be within 5°. Therefore, the present invention meets the actual production accuracy, can be used to verify the process design scheme in actual production, and reduce the high cost brought by sample trial production.

[0120] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than 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 on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to 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 general braiding simulation method for special-shaped structural parts based on a model reconstruction algorithm, characterized in that The method includes the following steps: Obtain the three-dimensional model data of the core mold of the special-shaped structural member; Construct the space curve equation of the core mold center line, specifically by projecting the contour boundary of the mandrel onto and planes, and then through the cubic curve interpolation algorithm and curve fitting algorithm, fitting and solving the curve of the contour boundary; take a point on the upper and lower boundary curves, intersect along their respective normal directions, and when the length of the line connecting the two points is equal, it is the discrete point of the center line; take the value according to the traction step and give , the plane curve equation, and the plane curve equation is as follows: ， Using the plane curve equation, synthesize the centerline space curve equation. During the synthesis process, use the two-dimensional line point-direction form to solve for the intersection points , and the two-dimensional line point-direction form is as follows: ， Among them, has coordinates , has coordinates , has coordinates , has coordinates , and respectively represent the tangent vectors of the first and second points on the center line. When the lengths of the line segments and the line segment are equal and the included angle is obtuse, is on the center line, and the corresponding point coordinates are recorded as the unordered discrete points of the center line; The form of the synthesized center line space curve equation is as follows: ， Among them, represents the centerline space curve trajectory corresponding to the i-th traction step length, is the traction step length, is the maximum length of the centerline, is the space curve equation of the is the space curve equation of the plane. Substitute the three-dimensional model data into the center line space curve equation to obtain the trajectory of the center line; Obtain the center line normal plane according to the trajectory of the center line; Based on the intersection of the central line normal plane and the original mesh patch, the outermost contour points are extracted to form an ordered contour point set. Specifically, the central line normal plane and the original mesh patch are used to take the intersection as the dense section point set. The dense section point set of the central line normal plane and the original mesh patch satisfies the following equation: ， Among them, , , are the point coordinates in the central axis normal plane; , , are the normal vector coordinates in the central axis normal plane, and i, j are the ordinal numbers of the normal vector coordinates; the outermost contour points are extracted to form an ordered contour point set; According to the ordered set of contour points, reconstruct the key cross-section of the core mold, and the key cross-section is determined by two intersecting space lines and The space lines and satisfy the following equations: ， Among them, , , is the ordinal number of the corner point coordinates of the triangular patch. Use the key cross-sections to obtain the number and positions of the reconstructed patch corner points, including first determining the number of corner points using the ordered contour point set of the key cross-sections, and then sequentially combining the points with corresponding serial numbers of adjacent key cross-sections to form the corner point sequences and normal vectors of multiple groups of patches. The patches are distributed clockwise in each segment according to the index numbers A0.0, A0.1, A0.2…A1.0, A1.1, A1.2... It is set that there are 48 patches in each grid segment, and 24 patch corner points in each key cross-section. According to the ordered contour point set with index relationship, obtain the coordinate positions of the corner points on the triangular patches, in the following form: ， ， Among them, represents the corner point coordinates on the triangular patch; is the corner point ordinal number, is the corner point coordinate; According to the number and positions of the reconstructed patch corner points, reconstruct the surface mesh of the core mold three-dimensional model, that is, combine all the patches together to reconstruct the surface mesh of the core mold three-dimensional model. The surface topology structure of the reconstructed core mold three-dimensional model is evenly distributed tangentially around the center line, and the arrangement order corresponds to the patch index number; Based on the kinematic characteristics, the deposition state of the yarn is judged using the surface mesh to obtain a judgment result. Among them, ignoring the interaction relationship between yarns and the serpentine movement of the spindle, the guide ring is described as a circular coil with a radius of , and the knitting device is described as a circular coil with a radius of . After reading the surface mesh data of the reconstructed mandrel model, the mandrel is set as a fixed reference system, and the spindles on the chassis perform a helical motion according to the traction trajectory. The helix generated by the helical motion satisfies the following expression: ， Among them, is the spatial position information of the i-th spindle on the spiral line at time j, is the position information of the center point of the knitting machine chassis at time j is the normal vector of the knitting machine chassis plane at time j, in the coordinate system of the core mold end face is the direction vector of the axis, and the angular position information of the i-th spindle on the chassis at time j; the intersection point of the yarn and the guide ring is determined according to the geometric relationship, and its expression is as follows: ， Among them, is the intersection point of the yarn corresponding to the i-th spindle at the j-th moment and the guiding ring, is the position information of the projection point of the yarn falling point corresponding to the i-th spindle at the j-th moment on the plane where the guiding ring is located, is the position information of the projection point of the i-th spindle on the plane where the guiding ring is located at the j-th moment, is to describe the projection of the yarn falling point in the guiding ring coordinate system in the plane of the guiding ring coordinate system, is to describe the projection of the position of the yarn falling point and the position of the spindle in the guiding ring coordinate system in the plane of the guiding ring coordinate system, is in the plane of the guiding ring coordinate system, and the included angle formed between the contact point, the midpoint of the guiding ring and the falling point is as follows: ， Among them, is the position of the weaving trajectory at time j; According to the intersection point of the yarn and the guiding ring , the yarn landing point and the triangular grid normal vector of the surface of the mandrel where the landing point is located , the state of the yarn is judged and analyzed. When the yarn is located under the corresponding triangular grid, it is defined that the yarn is deposited on the surface of the mandrel to form a fabric. The conditional expression for forming the fabric is as follows: ； Generate the yarn topological trajectory based on the judgment result; Generate the fabric structure according to the yarn topological trajectory.

2. The general braiding simulation method for special-shaped structural parts based on the model reconstruction algorithm according to claim 1, characterized in that, The generating the fabric structure according to the yarn topological trajectory includes: According to the yarn topological trajectory, use the interweaving relationship matrix to obtain the interweaving form of the yarn; Based on the interweaving form, perform secondary processing on each interweaving point on the surface of the core mold to form the spatial topology of the yarn; Generate the fabric structure using the elliptical cross-section and the spatial topology of the yarn.

3. A general braiding simulation method for special-shaped structural parts based on a model reconstruction algorithm according to claim 2, characterized in that The interweaving relationship matrix includes: The interweaving relationship matrix with a period of 2 interweaving points for the same interweaving situation on the same yarn in the spindle arrangement of the diamond weaving structure; The interweaving relationship matrix with a period of 4 interweaving points for the same interweaving situation on the same yarn in the spindle arrangement of the conventional weaving structure.

4. A general braiding simulation method for special-shaped structural parts based on a model reconstruction algorithm according to claim 2, characterized in that The secondary processing includes: At the interweaving point where the matrix content is 1, offset the clockwise yarn along the normal vector of the surface of the core mold by twice the yarn thickness, and offset the counterclockwise yarn by one time the yarn thickness; At the interweaving point where the matrix content is 0, offset the counterclockwise yarn along the normal vector of the surface of the core mold by twice the yarn thickness, and offset the clockwise yarn by one time the yarn thickness.

5. A general braiding simulation system for special-shaped structural parts based on a model reconstruction algorithm, the system using the general braiding simulation method for special-shaped structural parts based on the model reconstruction algorithm according to any one of claims 1 to 4, 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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