A vector field analysis-based automatic reference line generation method for fiber placement

Abstract

The application discloses a kind of automatic fiber placement reference line generation methods based on vector field analysis, first, draw several auxiliary lines on the surface along the vertical direction of 0 degree fiber direction, draw several reference line starting points on the surface, draw a geodesic line at each starting point as the basis reference line, calculate the nearest point of the basis reference line and each auxiliary line as the starting position of the reference line node optimization;Again, the laying surface is meshed, the fiber direction at each grid node is calculated, the geodesic curvature and angle deviation are calculated using the vector field analysis method, and the path planning quality comprehensive evaluation function is calculated;Finally, the optimal position of the reference line node is solved using the optimization algorithm, the objective function of the optimization algorithm is set as the reference line comprehensive evaluation function, the optimization variable is set as the position of the reference line node, and the optimal reference line is obtained by fitting node;The application can improve the design efficiency of reference line, thereby improving the efficiency and effect of automatic fiber placement path planning generation.

Description

Technical Field

[0001] This invention relates to the field of automated fiber placement technology for composite materials, and more specifically to an automated fiber placement reference line generation method based on vector field analysis. Background Technology

[0002] Automatic fiber placement is an advanced automated manufacturing process for composite materials. This process uses a fiber placement head to lay a set of parallel fibers on the surface of a mold to form a layer. Multiple layers are stacked to form a complete composite material laminate. It can realize the overall manufacturing of large and complex curved surface composite material components. Path planning is the key technology of automatic fiber placement.

[0003] The industry widely adopts the fixed angle method for fiber placement path planning ([1] Jiang M, Wu B, Ma LA novel path planning algorithm in robotic fibre placement for complex closed surface structures; proceedings of the 2017 IEEE International Conference on Mechatronics and Automation (ICMA), F, 2017 [C]. IEEE; [2] An L, Zhou Y, Zhou L. Composite fiber placement path planning and fiber number determination [J]. ACTA AERONAUTICA ET ASTRONAUTICA SINICA-SERIES A AND B-, 2007, 28(3): 745; [3] Wang N, Liu Y, Xiao J. Fiber-placementpath design for composite structures inpipy-form [J]. Journal of Computer-Aided Design & Computer Graphics, 2008, 20(2): 228-33.), whose technical solution is to strictly follow the fiber direction of the design to generate the laying path. It has the disadvantage of poor adaptability to complex curved surfaces and is easy to plan a path with excessive curvature, resulting in laying defects.In addition, a multi-reference path planning method has emerged ([4] QuW, He R, Wang Q, et al. Algorithms for Constructing Initial and Offset Path of Automated FiberPlacement for Complex Double-Curved Surfaces[J]. Applied Composite Materials, 2021, 28(3): 855-75; [5] Xiao H, Han W, Tang W, et al. An Efficient and Adaptable Path Planning Algorithm for Automated FiberPlacement Based on Meshing and Multi Guidelines[J]. Materials (Basel), 2020, 13(18).). This method first requires the user to design reference lines, and then uses the fiber direction obtained by mapping the reference lines to perform fixed-angle path planning. Although it has good adaptability to complex curved surfaces, it has the disadvantage of relying on manual design of reference lines, and the planning quality is difficult to guarantee. Therefore, an efficient automatic fiber placement reference line generation method is needed. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, this invention provides an automatic wire laying reference line generation method based on vector field analysis, which realizes the automatic generation of reference lines, improves the efficiency of reference line design, and thus improves the efficiency and effectiveness of path planning generation.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] An automatic wire-laying reference line generation method based on vector field analysis includes the following steps:

[0007] A. Create the initial node for the reference line;

[0008] B. Calculate the comprehensive evaluation index of the reference line using vector field analysis method;

[0009] C. Use optimization algorithms to find the optimal positions of the reference line nodes and fit the nodes to obtain the optimal reference line.

[0010] Step A specifically involves:

[0011] Draw several auxiliary lines perpendicular to the 0-degree fiber direction on the open surface or solid of revolution. Then, using the point drawing tool, draw several reference line starting points at equal intervals on the surface. Draw a geodesic line at each starting point as the basic reference line. Finally, calculate the closest point between the basic reference line and each auxiliary line in turn as the starting position for the node optimization of that reference line.

[0012] Step B specifically involves:

[0013] First, the laid-out surface is discretized into a mesh. The fiber orientation at each mesh node is calculated using the multi-reference line mapping principle. Then, the geodesic curvature and angular deviation are calculated using the vector field analysis method.

[0014] Vector field analysis method for calculating geodesic curvature: First, calculate the rate of change of fiber direction from each node to the adjacent node, and use a linear interpolation algorithm to calculate the rate of change of angle of the fiber along a specific direction, which is the geodesic curvature of the fiber along that direction;

[0015] The vector field analysis method calculates the angle deviation as follows: First, the finite difference algorithm is used to calculate the surface normal vector at each grid node. Then, the Rosette mapping rule is used to calculate the fiber direction reference at each node, and the ideal fiber direction vector is obtained by rotating it around the node normal vector by the corresponding angle. Then, based on the multi-reference line mapping principle, the actual fiber direction vector at each node is calculated. The angle between the ideal fiber direction and the actual fiber direction vector is calculated, which is the multi-reference line angle deviation at that node.

[0016] Then, using geodesic curvature and angle deviation, calculate the comprehensive evaluation function for path planning quality:

[0017]

[0018] In the above formula, N is the number of sampling points, w defect With w angle These are the weights for layability and angular deviation, respectively; V defect (i) is the layability index of node i, V angle (i) represents the angular deviation of node i; V defect The formula for calculating (i) is as follows:

[0019]

[0020] Where K g (i) represents the fiber geodesic curvature at the i-th node, K m (i) represents the critical geodesic curvature of the filament bundle at the i-th node, and N represents the number of sampling points.

[0021] Step C specifically involves:

[0022] The objective function of the optimization algorithm is set as the reference line comprehensive evaluation function in step B, and the optimization variable is set as the reference line node position. The optimization solution is then performed. After the solution is completed, the generated nodes are connected sequentially into a smooth curve using a cubic spline fitting tool to obtain the optimized reference curve.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] (1) This invention uses the vector field analysis method to directly evaluate the theoretical geodesic curvature and angle deviation of the fiber, omitting the process of first planning the path and then analyzing the path curvature, thus improving the efficiency of reference line evaluation and improvement.

[0025] (2) This invention uses an optimization algorithm to automatically generate reference curves. Compared with the traditional method of manually drawing reference lines, it realizes the automatic generation of reference curves and improves the efficiency of reference curve generation.

[0026] (3) The present invention uses a comprehensive index of angle deviation and geodesic curvature to evaluate the performance of the reference curve. Compared with the traditional subjective judgment method, the path planning result has better comprehensive performance. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the auxiliary plane and auxiliary curve for drawing open surfaces according to an embodiment of the present invention.

[0028] Figure 2 This is a schematic diagram of the auxiliary plane and auxiliary curve for drawing the rotating body according to an embodiment of the present invention.

[0029] Figure 3 This is a comparison between the path planning performance of the embodiments of the present invention and the planning performance of traditional methods. Detailed Implementation

[0030] The present invention will be further described in detail below with reference to embodiments, but the implementation of the present invention is not limited thereto.

[0031] An example of an automatic wire placement reference line generation method based on vector field analysis, using CATIA V5 software, includes the following steps:

[0032] A. Create the initial node for the reference line;

[0033] The initial node of the reference line is the starting point for reference line optimization and should be set near the optimal solution to speed up the optimization process and improve the optimization effect; for example... Figure 1 and Figure 2As shown, firstly, use CATIA's generative shape design tool on the open surface or solid of revolution to draw 3-5 auxiliary planes at approximately equal intervals in the 0-degree direction of the ply. Then, use the intersection function to calculate the intersection line between the auxiliary planes and the ply surface as the auxiliary line. Next, use the point drawing command to draw 2-5 reference line starting points at equal intervals on the surface. At each starting point, use the geodesic drawing command to draw a geodesic line as the base reference line. Finally, calculate the nearest point between the base reference line and each auxiliary line in turn, as the starting position for the node optimization of that reference line.

[0034] B. Calculate the comprehensive evaluation index of the reference line using vector field analysis method;

[0035] The mesh discretization interface provided by CATIA V5 CAA is used to discretize the laid-up surface into a mesh. Based on the principle of multi-reference line mapping, the fiber orientation at each mesh node is calculated. Then, the geodesic curvature and angle deviation are calculated using the vector field analysis method.

[0036] The vector field analysis method is used to calculate geodesic curvature: First, the angle between the fiber direction vectors from each node to the adjacent node is calculated, and then divided by the length of the connecting edge to obtain the rate of change of the fiber direction. The linear interpolation algorithm is used to calculate the rate of change of the fiber angle along a specific direction, that is, to calculate the geodesic curvature of the fiber along that direction.

[0037] The vector field analysis method calculates the angle deviation as follows: First, the finite difference algorithm is used to calculate the surface normal vector at each grid node. Then, the Rosette mapping rule is used to calculate the fiber direction reference at each node, and the ideal fiber direction vector is obtained by rotating it around the node normal vector by the corresponding angle. Then, based on the multi-reference line mapping principle, the actual fiber direction vector at each node is calculated. The angle between the ideal fiber direction and the actual fiber direction vector is calculated, which is the multi-reference line angle deviation at that node.

[0038] After the vector field analysis is completed, the geodesic curvature and angular deviation are used to calculate the comprehensive evaluation function for path planning quality:

[0039]

[0040] In the above formula, N is the number of sampling points, w defect With w angle These are the weights for layability and angular deviation, respectively; V defect (i) is the layability index of node i, V angle (i) represents the angular deviation of node i; V defect The formula for calculating (i) is as follows:

[0041]

[0042] Where Kg (i) represents the fiber geodesic curvature at the i-th node, K m (i) represents the critical geodesic curvature of the filament bundle at the i-th node, and N represents the number of sampling points;

[0043] C. Use optimization algorithms to find the optimal positions of the reference line nodes and fit the nodes to obtain the optimal reference line;

[0044] The optimization algorithm is implemented based on CATIA V5 CAA secondary development technology. The objective function of the optimization algorithm is set as the reference line comprehensive evaluation function in step B, and the optimization variable is set as the reference line node position. The optimization solution is then performed. After the solution is completed, the cubic spline fitting command in generative shape design is used to connect the optimal nodes sequentially into a smooth curve to obtain the optimized reference curve.

[0045] The beneficial effects of this embodiment are:

[0046] The automatic generation of reference lines was achieved. Using these reference lines for path planning can eliminate areas with excessive geodesic curvature within a certain angular deviation range. To verify the advantages of the reference line generation algorithm, path planning was performed using a fixed-angle algorithm and the method presented in this paper. A comparative analysis of the geodesic curvature of the planning results was then conducted. The comparison results are as follows: Figure 3 As shown in the figure, the dark dots mark the points where the geodesic curvature exceeds the standard. It can be seen from the figure that the path generated by the traditional fixed angle algorithm has a large area of ​​curvature exceeding the standard, while the curvature of the path obtained by the method in this paper is all within the standard, which proves that the method of this invention can effectively eliminate the geodesic curvature exceeding the standard area.

[0047] The above description is merely one embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for automatically generating wire-laying reference lines based on vector field analysis, characterized in that, Includes the following steps: A. Create the initial node for the reference line; B. Calculate the comprehensive evaluation index of the reference line using vector field analysis; specifically: First, the laid-out surface is discretized into a mesh. The fiber orientation at each mesh node is calculated using the multi-reference line mapping principle. Then, the geodesic curvature and angular deviation are calculated using the vector field analysis method. Vector field analysis method for calculating geodesic curvature: First, calculate the rate of change of fiber direction from each node to the adjacent node, and use a linear interpolation algorithm to calculate the rate of change of angle of the fiber along a specific direction, which is the geodesic curvature of the fiber along that direction; The vector field analysis method calculates the angle deviation: First, the difference algorithm is used to calculate the surface normal vector at each grid node. Then, the Rosette mapping rule is used to calculate the fiber direction reference at each node, and the ideal fiber direction vector is obtained by rotating around the node normal vector by the corresponding angle. Then, based on the principle of multi-reference line mapping, the actual fiber direction vector at each node is calculated; the angle between the ideal fiber direction and the actual fiber direction vector is calculated, which is the multi-reference line angle deviation at that node; Then, using geodesic curvature and angle deviation, calculate the comprehensive evaluation function for path planning quality: In the above formula The number of sampling points. and These are the weights for layability and angle deviation, respectively. For nodes Deployability index, For nodes Angular deviation; The calculation formula is as follows: in Indicates the first Fiber geodesic curvature at each node Indicates the first Critical geodesic curvature of the filament bundle at each node Indicates the number of sampling points; C. Use optimization algorithms to find the optimal positions of the reference line nodes and fit the nodes to obtain the optimal reference line.

2. The method according to claim 1, characterized in that, Step A specifically involves: Draw several auxiliary lines perpendicular to the 0-degree fiber direction on the open surface or solid of revolution. Then, using the point drawing tool, draw several reference line starting points at equal intervals on the surface. Draw a geodesic line at each starting point as the basic reference line. Finally, calculate the closest point between the basic reference line and each auxiliary line in turn as the starting position for the node optimization of that reference line.

3. The method according to claim 1, characterized in that, Step C specifically involves: The objective function of the optimization algorithm is set as the reference line comprehensive evaluation function in step B, and the optimization variable is set as the reference line node position. The optimization solution is then performed. After the solution is completed, the generated nodes are connected sequentially into a smooth curve using a cubic spline fitting tool to obtain the optimized reference curve.

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