Method for identifying features of arcs with irregular shapes in three-dimensional model

Abstract

The invention discloses a method for identifying features of an arc with an irregular shape in a three-dimensional model. The method comprises the following steps: S1, determining a three-dimensional entity feature model; s2, obtaining each outer surface of the three-dimensional entity feature model; s3, extracting an outer surface element domain; s4, dispersing the line elements according to given control parameters; s5, performing UV two-direction parameterization processing on the surface elements; s6, performing isoparametric curve solving on the UV directions of the surface elements to obtain two clusters of isoparametric curves; step S7, measuring each cluster of isoparametric curve in the UV direction; step S8, if any cluster of isoparametric curves of U or V are all arc lines, finally obtaining required arc features; otherwise, returning to the step S3. The method has the advantages that technologies such as topological decomposition, equal-chord-height discretization and parameterization processing of surface elements are comprehensively utilized, and automatic identification of irregular shape arc features is achieved.

Description

Technical Field

[0001] This invention relates to computer-aided design, and more particularly, to a method for recognizing arc features with irregular shapes in a three-dimensional model. Background Technology

[0002] Computer-aided design has become a primary design method in the industry. In strength design, circular arc features effectively reduce stress concentration, improve local stress distribution in parts, and minimize surface damage. In structural design, circular arc features ensure smooth transitions between different shapes, enhancing product aesthetics and assemblability. In machining, circular arc features on cutting tools can reduce surface roughness of workpieces and increase tool life. Therefore, circular arc features are widely used in practical product design.

[0003] Feature recognition technology is mainly applied in the fields of modifying existing models, simplifying models, and identifying manufacturing features. In actual 3D modeling, circular arc features, as auxiliary decorative features, are primarily attached to the parent feature. Therefore, circular arc features alter the topology of the original model (the position and size of points, lines, and surfaces), increasing the difficulty of subsequent model modifications. Finite element analysis preprocessing also requires the deletion or deactivation of circular arc features. The selection of machining processes and tools also needs to be designed and optimized based on circular arc features; therefore, circular arc recognition is an important component of feature recognition.

[0004] Typically, circular arc features can be directly measured and identified using CAD software. However, for complex parts, modeling often requires multiple trimmings and splicings based on existing circular arc features, resulting in irregular shapes that cannot be directly measured and identified using 3D modeling software. Therefore, recognizing circular arc features with irregular shapes is of great significance for rapid modification of product structures and improving the efficiency of finite element analysis preprocessing. Summary of the Invention

[0005] The purpose of this invention is to solve the problem that existing technologies can only identify circular arc features with regular shapes by directly measuring whether they have radius / diameter values, which cannot meet the actual design requirements. Therefore, this invention provides a novel method for identifying circular arc features with irregular shapes in three-dimensional models.

[0006] To achieve this objective, the technical solution of the present invention is as follows: a method for recognizing arc features with irregular shapes in a three-dimensional model, comprising: Step S1: Determine the 3D entity feature model; Step S2: Obtain each outer surface of the three-dimensional solid feature model; Step S3: Extract the elemental domains of the outer surface; Step S4: Discretize the line elements according to the given step size; Step S5: Parametrically process the UVs of the opposite element. Step S6: Solve for isoparametric curves in the UV direction of the curve element to obtain two sets of isoparametric curves; Step S7: Measure the isoparametric curves for each cluster in the UV direction; Step S8: If any cluster of isoparametric curves of U or V are all circular arcs, the desired circular arc feature is finally obtained; otherwise, proceed to step S3 to obtain the desired circular arc feature.

[0007] As a preferred method for identifying arc features with irregular shapes in a 3D model, in step S3, the element domain extraction method of the outer surface is to use the principle of topological decomposition to decompose the curved surface of the part into line elements and surface elements for subsequent measurement and discretization.

[0008] As a preferred method for identifying arc features with irregular shapes in a 3D model, in step S4, the outer surface line element discretization method adopts the equal chord height method, which fully considers the length and curvature variation trend of the line elements.

[0009] As a preferred method for recognizing circular arc features with irregular shapes in a 3D model, in step S5, the method for parameterizing the surface element in both UV directions is to first solve the surface equation, and then solve the scalar parameters of the discrete points of the line element projected onto the surface element.

[0010] As a preferred method for recognizing circular arc features with irregular shapes in a 3D model, in step S6, the isoparametric line solution method for the surface element is to fix one direction parameter of UV and solve for the parameter value of the other direction.

[0011] Compared with existing technologies, the beneficial effects of this invention are at least as follows: by comprehensively utilizing techniques such as topological decomposition, equal chord height discretization, and surface element parameterization, it achieves automatic recognition of irregular circular arc features. This solves the problem that the irregular shape of circular arcs makes direct measurement and judgment impossible, greatly improving the accuracy of circular arc feature recognition. Attached Figure Description

[0012] Figure 1 This is a flowchart of a circular arc feature recognition method according to an embodiment of the present invention.

[0013] Figure 2 This is a schematic diagram of an arc feature according to an embodiment of the present invention.

[0014] Figure 3 This is a schematic diagram of the topological decomposition of a circular arc feature surface according to an embodiment of the present invention.

[0015] Figure 4 This is an embodiment of the line element discretization method of the present invention.

[0016] Figure 5 This is a schematic diagram of a point cloud after line element discretization according to an embodiment of the present invention.

[0017] Figure 6 This is a schematic diagram of surface element parameterization according to an embodiment of the present invention.

[0018] Figure 7 This is a schematic diagram of a plane element UV direction isoparametric line cluster according to an embodiment of the present invention. Detailed Implementation

[0019] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. It should be noted that these descriptions are for the purpose of aiding understanding the invention and do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the invention described below can be combined with each other as long as they do not conflict with each other.

[0020] Object to be operated on: Circular arcs with irregular shapes.

[0021] Operational objective: To identify irregularly shaped circular arc features.

[0022] See Figure 1 The figure illustrates a method for recognizing irregularly shaped arc features in a 3D model. The recognition method includes: Step S1: Import a 3D part with arc features ( Figure 2 (As shown).

[0023] Step S2, Obtain the surface of the part: Use the extraction function of the 3D modeling software to obtain the surface of the part.

[0024] Step S3, see Figure 3 The topological decomposition method is used to extract line and surface elements from the outer surface of the part, and the UV direction of the surface elements is solved at the same time.

[0025] Step S4, see Figure 5 Using the method of equal chord height ( Figure 4 (As shown) Discretize the line elements into point cloud data.

[0026] Step S5, utilize the parameterized representation of the projection points of discrete points of line elements onto surface elements ( Figure 6 As shown, the face elements are parameterized.

[0027] Step S6, Figure 7As shown, based on the parameterized surface elements, the isoparametric curve family in the V direction is solved by fixing the U direction parameters; the isoparametric curve family in the U direction is solved by fixing the V direction parameters.

[0028] Step S7, Figure 7 As shown, based on the parameterized surface elements, the U-direction isoparametric curve cluster is solved by fixing the V-direction parameters.

[0029] Step S8: Based on the two sets of isoparametric curves of U and V, use the measurement function of CAD software to perform measurements respectively. If any set of isoparametric curves of U or V are all arcs, the required arc feature is finally obtained; otherwise, return to step S3 until the required arc feature is obtained.

[0030] By following the steps above, we can identify irregularly shaped arc features in a 3D model.

[0031] The above description merely illustrates embodiments of the present invention and is quite specific and detailed; however, it should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for recognizing circular arc features with irregular shapes in a three-dimensional model, characterized in that, Include the following steps and execute them in sequence: Step S1: Determine the 3D entity feature model; Step S2: Obtain each outer surface of the three-dimensional solid feature model; Step S3: Extract the elemental domains of the outer surface; Step S4: Discretize the line elements according to the given step size; Step S5: Parametrically process the UVs of the opposite element. Step S6: Solve for isoparametric curves in the UV direction of the curve element to obtain two sets of isoparametric curves; Step S7: Measure the isoparametric curves for each cluster in the UV direction; Step S8: If any cluster of isoparametric curves in U or V are all circular arcs, the desired circular arc feature is finally obtained; otherwise, return to step S3.

2. The method for recognizing irregularly shaped arc features in a three-dimensional model according to claim 1, characterized in that, In step S3, the element domain extraction method of the outer surface is to use the principle of topological decomposition to decompose the curved surface of the part into line elements and surface elements for subsequent measurement and discretization.

3. The method for recognizing irregularly shaped arc features in a three-dimensional model according to claim 1, characterized in that, In step S4, the outer surface line element discretization method adopts the equal chord height method.

4. The method for recognizing irregularly shaped arc features in a three-dimensional model according to claim 1, characterized in that, In step S5, the method for parameterizing the surface element in both UV directions is to first solve the surface equation, and then solve the scalar parameters of the discrete points of the line element projected onto the surface element.

5. The method for recognizing irregularly shaped arc features in a three-dimensional model according to claim 1, characterized in that, In step S6, the method for solving the isoparameter lines of the surface element is to fix one direction parameter of UV and solve the parameter value of the other direction.

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