A reference path planning method for fiber curve placement based on quadrilateral grid

Abstract

The present invention belongs to the technical field of fiber curve placement path planning, and proposes a fiber curve placement reference path planning method based on quadrilateral grids: first, a three-dimensional model of a composite material core mold is established in finite element software; second, the quadrilateral unit grid is divided, and the microscopic fiber placement angle orientation of the core mold surface in the three-dimensional model of the composite material core mold is used as a reference; then, the key nodes are obtained by using a quadrilateral grid surface reference path key node search algorithm; finally, a continuous fiber curve placement reference path is obtained by a curve fitting method. The present invention has universal applicability to the fiber curve placement reference path planning of any open surface shell structure, and can provide a reference path that satisfies the fiber placement angle distribution for the global path planning of composite materials, and has important theoretical significance and practical value for realizing the engineering application of fiber curve placement of composite materials.

Description

Technical Field

[0001] The invention relates to the technical field of fiber curve placement path planning, and in particular to a fiber curve placement reference path planning method based on quadrilateral grids. Background Art

[0002] Fiber-reinforced composite materials have the advantages of light weight, high specific strength, high specific stiffness, and strong designability, and are widely used in the manufacture of wind turbine blades, aircraft and other equipment. With the development of science and technology, higher requirements have been placed on the mechanical properties of composite materials such as stiffness, strength, and buckling. Therefore, it is a hot research direction to arrange a reasonable and effective fiber curve placement path and give full play to the axial mechanical properties of the fiber.

[0003] However, most of the existing studies are based on the finite element method to discretize the curved structure into grids, take the unit micro-fiber laying angle as the design variable, and optimize the fiber laying angle by constructing a mathematical model to obtain the optimal distribution of the micro-fiber laying angle. Planning the fiber curve placement reference path is the first step to obtain the curve placement fiber reinforced composite material. The existing reference path planning method has a low degree of automation, is not convincing, and the path trajectory fails to fully utilize the axial mechanical properties of the fiber, and cannot be directly applied to engineering practice. There is an urgent need for a fiber curve placement reference path planning method with a high degree of automation to provide a fiber curve placement reference path carrying fiber laying angle information for global fiber full placement. Summary of the invention

[0004] The purpose of the present invention is to provide a fiber curve placement reference path planning method based on quadrilateral grids to solve the technical problems of low automation, weak persuasiveness, small scope of application and failure to fully utilize the optimal distribution scheme of fiber placement angles for path planning in the existing reference path planning methods.

[0005] The present invention solves the technical problem and adopts the following technical solution:

[0006] A fiber curve placement reference path planning method based on quadrilateral grids comprises the following steps:

[0007] Establish a three-dimensional model of the composite material core mold in finite element software;

[0008] The quadrilateral unit grid is divided, and the microscopic fiber laying angle orientation on the mandrel surface in the three-dimensional model of the composite mandrel is used as a reference;

[0009] The key nodes are obtained by using the key node search algorithm of the quadrilateral mesh surface reference path;

[0010] The continuous fiber curve placement reference path is obtained through the curve fitting method.

[0011] As a further optimization, the finite element software is ABAQUS, and the curve fitting method adopts the cubic NURBS curve fitting method.

[0012] As a further optimization, the microscopic fiber laying angle orientation is a discrete fiber laying angle of a curved quadrilateral grid unit, which is planned according to the mechanical properties of the structure.

[0013] As a further optimization, the key nodes are obtained by using a quadrilateral mesh surface reference path key node search algorithm, including the following steps:

[0014] S301, determining a core mold surface boundary node set BJ, a surface quadrilateral mesh unit information set DY, a unit node set JD, and a core mold surface microscopic fiber laying angle set DJ in a Cartesian coordinate system;

[0015] S302, set the reference path search starting point First, save it to the reference path key node set P, determine the basic coordinates and number coordinates of the starting point, and set the number m of unit edge interpolation points;

[0016] S303, determine the unit and node number dy of First: [u,D 1 ,D 2 ,D 3 ,D 4 ], and the basic coordinates of the nodes [(x D1 ,y D1 ,z D1 );(x D2 ,y D2 ,z D2 );(x D3 ,y D3 ,z D3 );(x D4 ,y D4 ,z D4 )], according to the unit grid processing method, the search point set PS is obtained;

[0017] S304, according to the fiber laying angle θ of the current unit, following the search principle, determine the basic coordinates and number coordinates of the search direction vector XL and the end point Next;

[0018] S305, determine whether Next meets the search termination condition. If Next meets the search termination condition, Next is taken as the key node of the reference path and saved to the set P to terminate the search. If it does not meet the condition, the next search domain is predicted according to the type of Next. When the number of search domain units of Next is 3, the search direction vector XL that meets the search principle in each unit is solved respectively, and only the direction with the smallest angle between the search direction vectors of adjacent units is selected to solve the predicted search point newNext in this direction. When the number of search domain units of Next is 1, the predicted search end point newNext is solved according to the search principle.

[0019] S306. Determine whether the predicted search end point of the next search domain has a solution. If there is no solution, Next is used as the key node of the reference path and saved to the set P, and the search is terminated. If there is a solution, Next is used as the key node of the reference path and saved to the key node set P, and the point Next is used as the new First, and S303 to S306 are repeated.

[0020] As a further optimization, in step S302, the basic coordinates are expressed in the form of coordinates in a Cartesian coordinate system, and the unit number coordinates have two forms:

[0021] The first type: the search point is located at the node numbered v, and the starting point and end point of the search direction vector are both located at the unit numbered u, expressed as [u-(v)];

[0022] The second type: the search point is located on the edge of the unit with nodes numbered v and w. The starting point and end point of the search direction vector are both located on the unit numbered u. The numbering order of the nodes on the edge of the unit follows the counterclockwise arrangement of the unit, expressed as [u-(v,w)].

[0023] As a further optimization, in step S303, the unit grid processing method is to perform linear interpolation processing on the unit edge line to obtain interpolation points;

[0024] When the unit number is u and the node is D 1 , D 2 , D 3 and D 4 When the unit is D 1 D 2 Interpolation point a on the edge i Coordinates The solution is as follows:

[0025]

[0026] in, Point D 1 coordinate, Point D 2 Coordinates, m is the number of interpolation points.

[0027] As a further optimization, in step S304, the search principle includes:

[0028] 1) Using unit edge interpolation points and unit nodes as search points, the search space of key nodes of the benchmark path is expanded;

[0029] 2) The maximum constraint of the search direction angle and fiber laying angle error is as follows:

[0030] |θ w -α w |≤e

[0031] Where e is the search tolerance, θ w is the fiber laying angle in the unit numbered w, α w is the search direction angle within the unit numbered w, and the fiber laying angle θ w and search direction angle α w The maximum deviation does not exceed the search tolerance e, α w The solution formula is:

[0032]

[0033] Where L is the reference vector in the unit w that is in the same direction as the x-axis of the local coordinate system, XL w is the search direction vector in unit w, which is a directed line segment from the starting point to the search point in unit w;

[0034] 3) Maximum constraint on the angle between adjacent search direction vectors. The constraint conditions are as follows:

[0035] |α j -α j+1 |≤etheta

[0036] Among them, α j is the search direction of the jth search unit, α j+1 is the j+1th search unit, and etheta is the constraint value of the search direction vector angle.

[0037] As a further optimization, in step S305, the search termination condition includes:

[0038] 1) When the search point is located on a cell that has been searched, the search is terminated;

[0039] 2) When the key node of the search path reaches the boundary of the core mold surface, the search is terminated;

[0040] 3) When the maximum constraint of the angle between adjacent search direction vectors is not met, the search is terminated.

[0041] As a further optimization, in step S305, the types of the search points are divided into four types, namely:

[0042] 1) The search point is located on the unit edge;

[0043] 2) The search point is located on the unit node;

[0044] 3) The search point is located on the searched unit;

[0045] 4) The search point is located on the core mold boundary line.

[0046] As a further optimization, in step S305, the number of the search domain units changes with the type of the search end point Next, specifically including:

[0047] 1) The end point Next is located on the unit edge, and this edge is the common edge of the search domain unit and the current unit. The number of the search domain units is 1;

[0048] 2) The end point Next is located on the unit node, and this node is the common node of the search domain unit and the current unit. When the node is on the core mold boundary, the number of the search domain units is 1. When the node is not on the core mold boundary, the number of the search domain units is 3;

[0049] 3) The end point Next is located on the searched unit, and the number of the search domain units is 0.

[0050] The beneficial effects of the present invention are as follows: Through the above-mentioned method for planning the reference path of fiber curve placement based on quadrilateral meshes, it is possible to give the unit mesh processing method, the search principle of the key nodes of the reference path, and the search termination condition based on the quadrilateral meshes. According to the distribution law of the mesoscopic fiber laying angle, taking the unit nodes and interpolation points as the search points, the key nodes of the reference path are obtained, and the continuous fiber curve placement reference path is obtained by using the cubic NURBS curve fitting method. It carries the fiber laying angle orientation information, can give full play to the axial mechanical properties of the fibers, and improve the mechanical properties of the fiber-reinforced composite material structure. Therefore, the present invention has universality and high efficiency for the planning of the reference path of fiber curve placement on any open surface core mold, and has important theoretical significance and application prospects. Description of the Drawings

[0051] Figure 1 is the flowchart of the reference path planning of fiber curve placement based on quadrilateral meshes in Embodiment 1 and Embodiment 2 of the present invention;

[0052] Figure 2 is the schematic diagram of the search principle of the key nodes of the reference path in Embodiment 1 and Embodiment 2 of the present invention;

[0053] Figure 3 is the schematic diagram of the types of search points in Embodiment 1 and Embodiment 2 of the present invention;

[0054] Figure 4 (a) is a middle plate core mold in Embodiment 1 of the present invention, Figure 4 (b) is a finite element model of the square plate core mold in the first embodiment of the present invention, Figure 4 (c) is a microscopic fiber laying angle distribution diagram of the square plate core mold of Example 1 of the present invention;

[0055] Figure 5 This is a diagram of a key node search process for a reference path of a middle plate core mold in Embodiment 1 of the present invention;

[0056] Figure 6 is the reference path of the middle plate core mold in the first embodiment of the present invention;

[0057] Figure 7 (a) is the concave-convex curved surface core mold in the second embodiment of the present invention, Figure 7 (b) is the finite element model in the second embodiment of the present invention, Figure 7 (c) is a microscopic fiber laying angle distribution diagram in Example 2 of the present invention;

[0058] Figure 8 This is a diagram of a key node search process for a concave-convex curved surface core mold reference path in the second embodiment of the present invention;

[0059] Fig. 9 It is the reference path of the concave-convex curved surface core mold in the second embodiment of the present invention. DETAILED DESCRIPTION

[0060] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0061] Embodiment 1

[0062] See also Figure 1 to Figure 3 The present embodiment provides a method for planning a fiber curve placement reference path based on a quadrilateral grid. In the present embodiment, first, a three-dimensional model of a composite material core mold is established in finite element software; secondly, the quadrilateral unit grid is divided, and the microscopic fiber placement angle orientation on the surface of the core mold in the three-dimensional model of the composite material core mold is used as a reference; then, a quadrilateral grid surface reference path key node search algorithm is used to obtain key nodes; finally, a continuous fiber curve placement reference path is obtained through a curve fitting method.

[0063] Specifically, a fiber curve placement reference path planning method based on a quadrilateral grid in this embodiment can be used for a flat square core mold when applied, and can be implemented by the following specific steps:

[0064] S301, establish a plane square plate core mold model and divide the grid into quadrilateral units to obtain data set information.

[0065] Here, modeling and meshing can be performed in ABAQUS software to determine the microscopic fiber laying angle set DJ on the mandrel surface, determine the mandrel surface boundary node set BJ in the Cartesian coordinate system, and extract the unit information set DY and the unit node set JD through the INP file.

[0066] S302, set the starting point First of the search reference path, save it to the reference path key node set P, determine the basic coordinates and number coordinates of the starting point, and set the number m of unit edge interpolation points.

[0067] In this step, First is the starting point of the current unit search direction vector, and the starting point will be continuously updated during the search process. In addition, in this embodiment, the starting point First of the reference path search is the No. 1 node of the No. 1 unit, and its basic coordinates are (0,0,0), the unit number coordinates are [1-(1)], and the number of unit edge interpolation points is set to m.

[0068] S303, determine the unit and node number dy of First: [u,D 1 ,D 2 ,D 3 ,D 4 ], and the basic coordinates of the nodes [(x D1 ,y D1 ,z D1 );(x D2 ,y D2 ,z D2 );(x D3 ,y D3 ,z D3 );(x D4 ,y D4 ,z D4 )], according to the unit grid processing method, the grid edges are interpolated, the search points are arranged in counterclockwise order, and the search point set PS is obtained.

[0069] Here, the unit and node numbers dy of the starting point First are [1,1,2,23,22]. The basic coordinates of nodes 1, 2, 23, and 22 can be determined through the unit node set JD. The interpolation point a of the unit edge line with endpoints as nodes 1 and 2 i For example, its basic coordinates (x ai ,yai ,z ai ) is solved as follows:

[0070]

[0071] Among them, (x 1 ,y 1 ,z 1 ) is the basic coordinate of node 1, (x 2 ,y 2 ,z 2 ) are the basic coordinates of node 2.

[0072] S304. According to the fiber laying angle θ of the current unit, strictly follow the search principle to determine the basic coordinates and number coordinates of the search direction vector XL and the end point Next, wherein the fiber laying angle θ is a value in the angle system.

[0073] Specifically, the search principles are as follows:

[0074] 1) Using unit edge interpolation points and unit nodes as search points, the search domain of key nodes of the benchmark path is expanded;

[0075] 2) The maximum constraint of the search direction angle and fiber laying angle error is as follows:

[0076] |θ w -α w |≤e

[0077] Wherein, e is the search tolerance error. In this embodiment, e=1, which means the fiber laying angle θ w and search direction angle α w The maximum deviation does not exceed 1°, θ w is the fiber laying angle in the unit numbered w, α w is the search direction angle within the unit numbered w, and its solution formula is:

[0078]

[0079] Where L is the reference vector in the unit w that is in the same direction as the x-axis of the local coordinate system, XL w is the search direction vector in unit w, which is a directed line segment from the starting point to the search point in unit w;

[0080] 3) Maximum constraint on the angle between adjacent search direction vectors. The constraint conditions are as follows:

[0081] |α j -α j+1 |≤etheta

[0082] Among them, α j is the search direction of the jth search unit, α j+1is the j+1th search unit, etheta is the constraint value of the search direction vector angle, and in this embodiment, the reference path etheta=30°.

[0083] S305, determine whether Next meets the search termination condition. If Next meets the search termination condition, Next is used as the key node of the reference path and saved to the set P to terminate the search; if not, the next search domain is predicted based on the type of Next. When the number of search domain units of Next is 3, the search direction vector XL that meets the search principle in each unit is solved respectively, and only the direction with the smallest angle between the search direction vectors of adjacent units is selected to solve the predicted search point newNext in this direction; when the number of search domain units of Next is 1, the predicted search end point newNext is solved based on the search principle.

[0084] See also Figure 2 to Figure 6 , the search termination conditions of this embodiment include:

[0085] 1) When the search point is located on a cell that has been searched, the search is terminated;

[0086] 2) When the key node of the search path reaches the boundary of the core mold surface, the search is terminated;

[0087] 3) When the maximum constraint of the angle between adjacent search direction vectors is not met, the search is terminated.

[0088] In practical applications, search points can be divided into four types, as follows:

[0089] 1) The search point is located on the edge of the unit;

[0090] 2) The search point is located on the unit node;

[0091] 3) The search point is located on a cell that has been searched;

[0092] 4) The search point is located on the core mold boundary line.

[0093] Specifically, the number of units in the search domain changes with the search endpoint Next type, including:

[0094] 1) The end point Next is located on the unit edge, which is the common edge between the search domain unit and the current unit, and the number of search domain units is 1;

[0095] 2) The end point Next is located at the unit node, which is the common node of the search domain unit and the current unit. When the node is at the core module boundary, the number of search domain units is 1, otherwise, the number of search domain units is 3;

[0096] 3) The end point Next is located on the cell that has been searched, and the number of cells in the search domain is 0;

[0097] S306. Determine whether the predicted search end point of the next search domain has a solution. If there is no solution, take Next as the key node of the reference path, save it to the set P, and terminate the search. Otherwise, take Next as the key node of the reference path, save it to the key node set P, and take the point Next as the new First, repeat S303 to S306.

[0098] S307 , using a cubic NURBS curve fitting method to obtain a continuous fiber curve placement reference path.

[0099] In this embodiment, the cubic NURBS curve can be expressed as a piecewise rational polynomial vector function in the form of:

[0100]

[0101] Among them, ω i (i=0,1,…,n) are weight factors, respectively related to the control point d i (i=0,1,…,n) are associated, and the first and last weight factors ω are specified 0 ,ω n >0, the restω i ≥0(i=1,2,…,n-1) to avoid the situation where the denominator of the fraction is zero. N i,3 (u) is a cubic B-spline basis function, defined on a non-periodic non-uniform canonical knot vector U, U = [u 0 ,u 1 ,…,u n+4 ], the repetition degree of the nodes at the beginning and end of the curve is 4, u 0 =u 1 =u 2 =u 3 =0,u n+1 =u n+2 =…=u n+4 =1, and the rest u∈[u 3 ,u n+1 ]=[0,1], the first and last points of the curve coincide with the first and last control vertices of its control polygon, and the first and last vertices are tangent to the first and last edges of the control polygon. The function of the cubic NURBS curve can be determined by the recursive formula of de Boor and Cox, as shown below:

[0102]

[0103] Specifically, fitting to generate NURBS curves is called curve inverse calculation, which mainly includes three steps:

[0104] (1) Calculate node vector

[0105] Make a cubic NURBS curve pass through the given point P i (i=0,1,...,n), in addition to ensuring that the first and last points of the curve coincide with the type value point, it is also necessary to ensure that P i Sequentially with the nodes u in the domain of the construction curve i+3 (i=0,1,...,n) one-to-one correspondence. This paper uses the canonical cumulative chord length method to parameterize the type value points, which can better deal with the problem of dense or sparse distribution of points in the parameter space, making the curve representation in the parameter space more uniform and accurate. The parameterization of the type value points of the cubic NURBS curve must satisfy the following formula:

[0106]

[0107] (2) Calculation boundary conditions

[0108] The boundary conditions for solving cubic NURBS curves are: tangent vector condition, open curve free endpoint condition and closed curve condition.

[0109] 1) The tangent vector condition requires that the tangent direction of the first and last points is fixed:

[0110]

[0111] Among them, d i is the control vertex, Δ i =u i+1 -u i (i=0,1,...,n) represents the node interval length.

[0112] 2) The free endpoint condition of the open curve requires that the curvature of the first and last points is 0, and the following formula must be satisfied:

[0113]

[0114] 3) The closed curve condition requires that the first and last points of the curve coincide and be second-order continuous, then:

[0115]

[0116] (3) Inverse calculation of control vertices

[0117] The first and last control vertices of a cubic NURBS curve are the shape value points at the first and last ends, that is, d 0 =P 0 ,d n+2 =P n , the matrix expression of control point inverse calculation is:

[0118]

[0119] e i =(Δ i+1 +Δi+2 ) i (i=0,1,…,n)

[0120] Among them, P 0 and P n is the first and last point of the curve, P 0 ′ and P n ′ is the tangent vector of the first and last points, element a i , b i 、c i 、e i No special meaning.

[0121] Figure 4 The square plate core mold, finite element model and microscopic fiber laying angle distribution diagram are shown, where the microscopic fiber laying angle direction is consistent. Figure 5 The figure shows the search process of the key nodes of the benchmark path. A total of 40 key nodes were obtained. Figure 6 The reference path obtained by the cubic NURBS curve fitting method is shown. Figure 4 The microscopic fiber laying angle distribution diagram in the reference path carries the fiber laying angle information and can be used as the reference path for global fiber curve placement.

[0122] In this embodiment, a fiber curve placement reference path planning method based on quadrilateral grid is proposed. The quadrilateral grid of the core mold is interpolated, and the fiber laying angle distribution of the unit grid is used as a reference. The search principle and search termination condition of the key nodes of the reference path are strictly followed to obtain the key nodes of the reference path. The reference path is not obtained by using the cubic NURBS curve fitting method. The square plate core mold with a fixed direction micro-fiber laying angle distribution is used as an example to prove the effectiveness of the reference path planning method.

[0123] Embodiment 2

[0124] See also Figure 1 to Figure 3 ,as well as Figure 7 to Figure 9 , a fiber curve placement reference path planning method based on a quadrilateral grid in this embodiment is used for a concave-convex curved surface mandrel, and specifically includes the following steps:

[0125] S301, establish a plane square plate core mold model and divide the grid into quadrilateral units.

[0126] Here, the modeling and meshing are also performed in ABAQUS software to determine the microscopic fiber laying angle set DJ on the mandrel surface, the mandrel surface boundary node set BJ in the Cartesian coordinate system, and the unit information set DY and the unit node set JD are extracted through the INP file.

[0127] S302, set the starting point First of the search reference path, save it to the reference path key node set P, determine the basic coordinates and number coordinates of the starting point, and set the number m of unit edge interpolation points.

[0128] Among them, First is the starting point of the current unit search direction vector, and the starting point will be continuously updated during the search process. In this embodiment, the starting point First of the reference path search is taken as the 14th node of the 14th unit, its basic coordinates are (20,30,44), the unit number coordinates are [14-(14)], and the number of unit edge interpolation points is set to m.

[0129] S303, determine the unit and node number dy of First: [u,D 1 ,D 2 ,D 3 ,D 4 ], and the basic coordinates of the nodes [(x D1 ,y D1 ,z D1 );(x D2 ,y D2 ,z D2 );(x D3 ,y D3 ,z D3 );(x D4 ,y D4 ,z D4 )], according to the unit grid processing method, the grid edges are interpolated, the search points are arranged in counterclockwise order, and the search point set PS is obtained.

[0130] Among them, the unit and node numbers dy of the starting point First are [14, 14, 42, 43, 15], and the basic coordinates of nodes 14, 42, 43, and 15 can be determined through the unit node set JD.

[0131] Specifically, the interpolation point a of the edge line of the node unit with endpoints 14 and 42 i For example, its basic coordinates The solution is as follows:

[0132]

[0133] Among them, (x 1 ,y 1 ,z 1 ) is the basic coordinate of node 14, (x 2 ,y 2 ,z 2 ) are the basic coordinates of node 42.

[0134] S304. According to the fiber laying angle θ of the current unit, strictly follow the search principle to determine the basic coordinates and number coordinates of the search direction vector XL and the end point Next.

[0135] Specifically, the fiber laying angle θ is a value in an angle system, and the search principle is the same as that in the first embodiment.

[0136] S305, determine whether Next meets the search termination condition. If Next meets the search termination condition, Next is used as the key node of the reference path and saved to the set P to terminate the search; if not, the next search domain is predicted based on the type of Next. When the number of search domain units of Next is 3, the search direction vector XL that meets the search principle in each unit is solved respectively, and only the direction with the smallest angle between the search direction vectors of adjacent units is selected to solve the predicted search point newNext in this direction; when the number of search domain units of Next is 1, the predicted search end point newNext is solved based on the search principle.

[0137] It should be noted that the search termination condition in this embodiment is the same as that in the first embodiment. The change in the number of search domain units with the search endpoint type is the same as that in the first embodiment.

[0138] S306. Determine whether the predicted search end point of the next search domain has a solution. If there is no solution, take Next as the key node of the reference path, save it to the set P, and terminate the search. Otherwise, take Next as the key node of the reference path, save it to the key node set P, and take the point Next as the new First, repeat S303 to S306.

[0139] S307 , using a cubic NURBS curve fitting method to obtain a continuous fiber curve placement reference path.

[0140] Specifically, the cubic NURBS curve fitting method in this embodiment is the same as that in the first embodiment.

[0141] Figure 7 The concave-convex surface core mold, finite element model and microscopic fiber laying angle distribution diagram are shown, where the microscopic fiber laying angle value range is 0°≤θ≤90°. Figure 8 The figure shows the search process of the key nodes of the benchmark path. A total of 46 key nodes were found. Fig. 9 The reference path obtained by the cubic NURBS curve fitting method is shown. Figure 7 The microscopic fiber laying angle distribution diagram in shows that the orientation of the reference path satisfies the laying angle distribution law. The path carries the fiber laying angle information and can be used as the reference path for global fiber curve placement.

[0142] This embodiment is based on the fiber curve placement benchmark path planning method of the quadrilateral grid, interpolates the quadrilateral grid of the core mold, takes the fiber laying angle distribution of the unit grid as a reference, strictly follows the search principles and search termination conditions of the key nodes of the benchmark path, and obtains the key nodes of the benchmark path. Instead of using the cubic NURBS curve fitting method to obtain the benchmark path, the concave and convex curved surface core mold with variable direction microscopic fiber laying angle distribution is used as an embodiment, which proves that the benchmark path planning method is effective and universal for path planning on the surface of the open curved core mold.

[0143] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for planning a reference path for fiber curve placement based on quadrilateral grids, characterized in that: The steps include: S1. Establish a three-dimensional model of the composite material core mold in finite element software; S2, dividing the quadrilateral unit grid, taking the microscopic fiber laying angle orientation on the surface of the mandrel in the three-dimensional model of the composite mandrel as a reference; S3, using a quadrilateral mesh surface reference path key node search algorithm to obtain key nodes; The method of obtaining key nodes by using a quadrilateral mesh surface reference path key node search algorithm comprises the following steps: S301, determine the core mold surface boundary node set in the Cartesian coordinate system BJ , surface quadrilateral mesh unit information collection DY , unit node set JD and the microscopic fiber laying angle collection on the mandrel surface DJ ; S302: Set the reference path search starting point First and save it to the reference path key node set P , determine the basic coordinates and number coordinates of the starting point, and set the number of interpolation points of the unit edge m ; S303, determine the unit and node number dy of First: [ u , D 1, D 2, D 3, D 4], and the basic coordinates of the nodes , according to the unit grid processing method, obtain the search point set PS ; S304, according to the fiber laying angle of the current unit , follow the search principle and determine the search direction vector XL And the basic coordinates and number coordinates of the end point Next; S305: Determine whether Next satisfies the search termination condition. If Next satisfies the search termination condition, save Next as the key node of the reference path to the collection. P , terminate the search. If it is not satisfied, the next search domain is predicted according to the type of Next. When the number of search domain units of Next is 3, solve the search direction vector that satisfies the search principle in each unit respectively. XL , only the direction with the smallest angle between the adjacent unit search direction vectors is selected to solve the predicted search point newNext in this direction; when the number of search domain units of Next is 1, the predicted search end point newNext is solved according to the search principle; S306: Determine whether the predicted search end point of the next search domain has a solution. If there is no solution, save Next as the key node of the reference path to the collection P , terminate the search, if there is a solution, save Next as the key node of the benchmark path to the key node set P and take the point Next as the new First, repeating S303 to S306; S4. Obtain a continuous fiber curve placement reference path through a curve fitting method.

2. A method for planning a reference path for fiber curve placement based on quadrilateral grid according to claim 1, characterized in that: The finite element software is ABAQUS, and the curve fitting method adopts the cubic NURBS curve fitting method.

3. The method for planning a reference path for fiber curve placement based on quadrilateral grid according to claim 1, characterized in that: The microscopic fiber laying angle orientation is a discrete fiber laying angle of a curved quadrilateral grid unit, and is planned according to the mechanical properties of the structure.

4. The method for planning a reference path for fiber curve placement based on quadrilateral grid according to claim 1, characterized in that: In step S302, the basic coordinates are expressed in the form of coordinates in a Cartesian coordinate system, and the unit number coordinates have two forms: Category 1: The search point is located at v The starting point and end point of the search direction vector are both located at the node numbered u The unit is expressed as [ u -( v )]; The second type: the search point is located at the node number v and w On the edge of the unit, the starting point and end point of the search direction vector are both located at u On a unit, the numbering order of the nodes on the unit edge line follows the counterclockwise arrangement of the unit, expressed as [ u -( v , w )].

5. The method for planning a reference path for fiber curve placement based on quadrilateral grid according to claim 1, characterized in that: In step S303, the unit grid processing method is to perform linear interpolation processing on the unit edge line to obtain interpolation points; When the unit number is u , the node is D 1 、D 2 、D 3 and D 4 units, D 1 D 2 interpolation points on the edge a i Coordinates The solution is as follows: ， in, For point D 1 coordinate, For point D 2 coordinates, m is the number of interpolation points.

6. The method for planning a reference path for fiber curve placement based on quadrilateral grid according to claim 1, characterized in that: In step S304, the search principle includes: 1) Using unit edge interpolation points and unit nodes as search points, the search space of key nodes of the benchmark path is expanded; 2) The maximum constraint of the search direction angle and fiber laying angle error is as follows: ， in, e To search for the tolerance, For the number w The fiber laying angle within the unit, For the number w Search direction angle within the unit, fiber laying angle and search direction The maximum deviation does not exceed the search tolerance e , The solution formula is: ， in, L For unit w Central and local coordinate systems x The reference vectors of the same axis, XL w For unit w The search direction vector within is the unit w A directed line segment from the starting point to the search point; 3) Maximum constraint on the angle between adjacent search direction vectors. The constraint conditions are as follows: ， in, For the j The search direction of the search unit, For the j +1 search unit, etheta is the constraint value of the search direction vector angle.

7. The method for planning a reference path for fiber curve placement based on quadrilateral grid according to claim 1, characterized in that: In step S305, the search termination condition includes: 1) When the search point is located on a cell that has been searched, the search is terminated; 2) When the key node of the search path reaches the boundary of the core mold surface, the search is terminated; 3) When the maximum constraint of the angle between adjacent search direction vectors is not met, the search is terminated.

8. The method for planning a reference path for fiber curve placement based on quadrilateral grid according to claim 1, characterized in that: In step S305, the search point types are divided into four types, namely: 1) The search point is located on the unit edge; 2) The search point is located on the unit node; 3) The search point is located on a cell that has been searched; 4) The search point is located on the core mold boundary line.

9. The method for planning a reference path for fiber curve placement based on quadrilateral grid according to claim 1, characterized in that: In step S305, the number of search domain units varies with the type of the search destination Next, specifically including: 1) The end point Next is located on the cell edge, which is the common edge between the search domain cell and the current cell. The number of search domain cells is 1; 2) The end point Next is located at the unit node, which is the common node of the search domain unit and the current unit. When the node is at the core model boundary, the number of search domain units is 1, and when the node is not at the core model boundary, the number of search domain units is 3; 3) The end point Next is located on a cell that has been searched, and the number of cells in the search domain is 0.

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