Method for automatically extracting geometric information of tubular three-dimensional model

Abstract

The invention discloses a method for automatically extracting geometric information of a tubular three-dimensional model. Establishing a reference plane and a rotating center shaft by searching a key curved surface of the tubular three-dimensional model; key points are created through intersection points between all the reference planes and all the rotating center shafts, and sorting is managed according to rules; solving the bending radius through any one bending surface; and finally, geometric information of the tubular three-dimensional model is obtained through the steps, the pipe diameter is obtained, and the center line of the tubular three-dimensional model is created. According to the method, the topological geometric information of the tubular three-dimensional model is extracted, so that related work of automation of the tubular three-dimensional model can be developed.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of computer-aided design of tubular three-dimensional models, and in particular to the extraction of geometric information of CAD topology of tubular three-dimensional models. BACKGROUND

[0002] The production of pipe fittings is to bend the pipe through a pipe bender. The instructions of the pipe bender mainly include feeding, rotating, and bending. A straight pipe can complete the processing of a basic pipe fitting through a series of feeding, rotating, and bending of the bending machine. The parameters of feeding mainly refer to the length of the straight section, the parameters of rotating mainly refer to the angle of the space angle, and the parameters of bending mainly refer to the supplementary angle of the bend angle. The feeding, rotating, and bending parameters of the pipe fitting can be obtained to complete the pipe bending process, and the above parameters can be calculated through the center line of the pipe fitting. SUMMARY

[0003] The present application aims to obtain key geometric information of a tubular three-dimensional model, including a center line, a pipe diameter, and a bending radius, through the tubular three-dimensional model. The key data information is provided for direct calculation of process parameters, automatic reconstruction of tubular three-dimensional model parameterization, and optimization of tubular three-dimensional model.

[0004] The technical solution of the present application is to provide a method for automatically extracting geometric information of a tubular three-dimensional model, which includes traversing the tubular three-dimensional model to find key surfaces, creating a reference plane and a rotating center axis, creating key points, solving a bending radius, creating a center line of the tubular three-dimensional model, and obtaining a pipe diameter.

[0005] Specifically, the step of traversing the tubular three-dimensional model to find key surfaces includes the following steps: (1) finding a starting surface and a terminating surface, which is achieved by traversing all surfaces, marking two planes, marking one of the planes as a starting surface M1 and the other as a terminating surface Mn; (2) sequentially finding effective surfaces, which is achieved by starting from the starting surface M1, sequentially searching adjacent surfaces, selecting surfaces with large diameters as effective surfaces, and sequentially marking them as M2, M3,..., Mi-1, Mi,..., Mn-1, until the next surface is the terminating surface Mn.

[0006] Specifically, the step of creating a reference plane and a rotating center axis includes sequentially selecting key surfaces, creating a reference plane that coincides with the starting plane or the terminating plane when the key surface is the starting plane M1 or the terminating plane Mn, creating a rotating center axis of a cylindrical surface when the key surface is a cylindrical surface, and sequentially marking it as L1, L2,..., Li-1, Li,..., Ln-1, Ln; and not performing any operation when the key surface is a conical surface or a curved surface.

[0007] Specifically, the creating key points specifically includes the following steps: (1) selecting a starting surface M1 and a first rotation center axis L1, and creating an intersection point as a reference point and marking it as a first key point P1; (2) sequentially creating intersection points of adjacent two rotation center axes as key points and sequentially marking them as P2, P3, …, Pi-1, Pi, …, Pn-1; and (3) selecting a last rotation center axis Ln and a terminal surface Mn, and creating an intersection point as a reference point and marking it as a last key point Pn.

[0008] Specifically, the solving bending radius specifically includes the following steps: (1) obtaining any one bending surface in the key surface, traversing two circles on an edge of the bending surface, selecting a center of any one circle as a point O to create an auxiliary reference point; (2) calculating an included angle Beta formed by rotation center axes of two adjacent cylindrical surfaces of the bending surface; (3) when the included angle Beta is not 0° or 180°, then the bending radius = tan (0.5*Beta)*OB, wherein point B represents an intersection point of the two adjacent rotation center axes of the cylindrical surfaces, and OB represents a length of a line connecting the points O and B; and when 0°≤Beta≤1° or 179°≤Beta≤180°, then the bending radius is equal to half of a distance between the two adjacent rotation center axes.

[0009] Specifically, the creating a center line of the tubular three-dimensional model includes sequentially connecting the key points to draw line segments, drawing fillets, setting a fillet radius equal to the bending radius, and completing a rough sketch of the center line.

[0010] Specifically, the sequentially creating intersection points of adjacent two rotation center axes as reference points, when the included angle of the two rotation center axes is 0°≤Beta≤1° or 179°≤Beta≤180°, supplementally inserting a key point, specifically includes the following steps: (1) starting from the starting surface M1, sequentially marking the bending surfaces in all key surfaces as N1, N2, …, Ni-1, Ni, …, Nn-1, Nn; (2) starting from a group of rotation center axes Ln, Ln-1, and stopping at a group of rotation center axes L2, L1, measuring an included angle Beta of adjacent two rotation center axes, when 0°≤Beta≤1° or 179°≤Beta≤180°, determining that a surface Ni-1 clamped by the rotation center axes Li-1 and Li is a U-shaped bending surface; (3) traversing an edge of the U-shaped bending surface to find two circles on the edge, creating two circle centers Oi and Oi-1 as auxiliary reference points, wherein the point Oi is on the rotation center axis Li, and the point Oi-1 is on the rotation center axis Li-1; (4) taking the key point Pi and the key point Pi-1; offsetting the point Oi in a direction of , and the offset length is equal to the bending radius, and the offset point is Ki; offsetting the point Oi-1 in a direction of offsets the direction of the point Ki by a length equal to the bending radius, and the offset point is Ki-1; (5) inserts the point Ki-1 and the point Ki into the key point group, and the order of the key points after the insertion is: P1, P2, …, Pi-1, Ki-1, Ki, Pi, …, Pn-1, Pn; (6) finds and processes all U-shaped bends according to the above operations. Specifically, the bending surface is a curved surface other than a plane, a cylindrical surface and a conical surface.

[0011] Specifically, the method obtains any bending surface in the key curved surface, and if there is no bending surface in the key curved surface, directly returns without solving the bending radius.

[0012] After the above technical solution, the present application has the following advantages: the key topological geometric information such as the center line, the bending radius, the inner and outer diameters of the tubular three-dimensional model can be quickly obtained from the tubular three-dimensional model, which is beneficial to the development of automatic related work of the tubular three-dimensional model, such as automatic generation of 2D engineering drawings, automatic calculation of process parameters of the tubular three-dimensional model, three-dimensional standardized parameterized reconstruction, and the like, and is used for tubular three-dimensional model optimization design or tubular three-dimensional model automatic simulation. BRIEF DESCRIPTION OF DRAWINGS

[0013] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only one embodiment of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0014] Figure 1 is a geometric information automatic extraction method flowchart of a tubular three-dimensional model provided by the present application.

[0015] Figure 2 is a key curved surface schematic diagram of an embodiment of the present application.

[0016] Figure 3 is a reference plane schematic diagram of an embodiment of the present application.

[0017] Figure 4 is a rotating center axis schematic diagram of an embodiment of the present application.

[0018] Figure 5 is a key point schematic diagram of an embodiment of the present application.

[0019] Figure 6 is a bending radius solving method schematic diagram of an embodiment of the present application.

[0020] Figure 7 is a supplementary insertion key point schematic diagram of an embodiment of the present application. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0022] As shown in FIG. 1, a flow chart of a method for automatically extracting geometric information of a tubular three-dimensional model according to the present application comprises the following steps: Figure 1

[0023] As shown in FIG. 2, the key surface of the tubular three-dimensional model is found, comprising the following steps: Figure 2

[0024] (1) The starting surface and the ending surface are found, and the method is as follows: all the surfaces are traversed, and only two planes are marked, one of which is marked as the starting surface M1, and the other is marked as the ending surface M15;

[0025] (2) The effective surface is found in sequence, and the method is as follows: starting from the starting surface M1, the adjacent surfaces are searched in sequence, the surface with a large diameter is selected as the effective surface, and is marked as M2, M3,..., M14 in sequence, until the next surface is the ending surface M15.

[0026] As shown in FIG. 3, the key surface is selected in sequence, and when the key surface is the starting plane M1 or the ending plane M15, a reference plane coinciding with the starting plane or the ending plane is created; as shown in FIG. 4, when the key surface is a cylindrical surface, a rotation center axis of the cylindrical surface is created, and is marked as L1, L2,..., L6, L7 in sequence; when the key surface is a conical surface or a curved surface, no operation is performed. Figure 3 Figure 4 As shown in FIG. 5, the key point is created according to the following steps:

[0027] As shown in FIG. 6, the key point is created according to the following steps: Figure 5

[0028] (1) The starting surface M1 and the first rotation center axis L1 are selected, and the intersection point is created as a reference point and is marked as the first key point P1;

[0029] (2) The intersection points of the adjacent two rotation center axes are sequentially created as key points, and are sequentially marked as P2, P3,..., P6.

[0030] ​​​​(3) Select the last rotation center axis L7 and the terminal surface M15, and create the intersection point as the reference point as the last key point P7.

[0031] As shown in Figure 6 , the bending radius of the tubular three-dimensional model includes the following steps:

[0032] (1) Obtain the bend M3 in the key surface, traverse the two circles on the edge of the bend, select the center of any one circle as point O, and create an auxiliary reference point;

[0033] (2) Calculate the included angle Beta formed by the rotation center axes L1 and L2 of the two adjacent cylindrical surfaces of the bend;

[0034] (3) When 0°≤Beta≤1° or 179°≤Beta≤180°, then the bending radius = tan(0.5*Beta)*OB, where point B represents the intersection of the two adjacent rotation center axes of the bend, and OB represents the length of the line connecting point O and point B; When the included angle Beta is 0° or 180°, then the bending radius is equal to half the distance between the two adjacent rotation center axes of the bend. In this embodiment, the included angle Beta between the rotation center axes L1 and L2 obtained from the bend M3 is 49°, and OB is 43.89mm, which is substituted into the formula to calculate the bending radius of the tubular three-dimensional model as 20.0018mm, which is rounded to 20mm.

[0035] As shown in Figure 7 , the included angle between the rotation center axes L4 and L5 is 0°≤Beta≤1° or 179°≤Beta≤180°, which are parallel to each other, and supplementary key points are inserted, including the following steps:

[0036] (1) Start from the starting surface M1, and sequentially mark the bends in all key surfaces as N1, N2,..., N5, N6;

[0037] (2) Starting from one group of rotation center axes L7, L6, and stopping at one group of rotation center axes L2, L1, measure the included angle Beta of the adjacent two rotation center axes, when 0°≤Beta≤1° or 179°≤Beta≤180°, determine that the surface between the two rotation center axes is a U-shaped bend; According to the above determination method, the bend N4 between the rotation center axes L4 and L5 in this embodiment is a U-shaped bend.

[0038] (3) Traverse the edge of the U-shaped bend to find two circles on the edge, and create the centers O5 and O4 of the two circles as auxiliary reference points, where point O5 is on the rotation center axis L5 and point O4 is on the rotation center axis L4;

[0039] (4) Take the key point P5 and the key point P4; move the point O5 along the rotation center axis L5 to the point P5, and move the point O4 along the rotation center axis L4 to the point P4; offsets the point O4 in the direction of the bending radius, and the offset point is K4; offsets the point O4 in the direction of the bending radius, and the offset point is K4;

[0040] (5) inserts the point K4 and the point K5 into the key point group, and the order of the key points after the insertion is: P1, P2,..., P4, K4, K5, P5,..., P7;

[0041] (6) finds and processes all U-shaped bends according to the above operations.

[0042] connects the key points in sequence to draw a line segment, draws a round corner, sets the round corner radius equal to the bending radius, and completes the rough sketch of the center line. The above-described embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and should be included in the protection scope of the present application.

Claims

1. A method for automatically extracting geometric information of a tubular three-dimensional model, comprising traversing the tubular three-dimensional model to find key surfaces, creating a reference plane and a central axis of rotation, creating key points, solving the bend radius, creating a centerline of the tubular three-dimensional model, and obtaining the pipe diameter.

2. The method for traversing the tubular three-dimensional model to find key surfaces according to claim 1, specifically comprising the following steps: (1) finding a starting surface and a terminal surface, by traversing all surfaces, marking two planes, and marking any one of the two planes as the starting surface M1 and the other as the terminal surface Mn; (2) sequentially finding effective surfaces, by starting from the starting surface M1, sequentially searching adjacent surfaces, selecting surfaces with large diameters as effective surfaces, and sequentially marking them as M2, M3,..., Mi-1, Mi,..., Mn-1, until the next surface is the terminal surface Mn.

3. The method for creating a reference plane and a central axis of rotation according to claim 1, by sequentially selecting key surfaces, creating a reference plane coinciding with the starting plane or the terminal plane when the key surface is the starting plane M1 or the terminal plane Mn, creating a central axis of rotation of a cylindrical surface when the key surface is a cylindrical surface, and sequentially marking it as L1, L2,..., Li-1, Li,..., Ln-1, Ln; and not performing operations when the key surface is a conical surface or a curved surface.

4. The method for creating key points according to claim 1, specifically comprising the following steps: selecting the starting surface M1 and the first central axis of rotation L1, and creating a reference point at their intersection as the first key point P1; sequentially creating key points at the intersection of adjacent two central axes of rotation, and sequentially marking them as P2, P3,..., Pi-1, Pi,..., Pn-1; selecting the last central axis of rotation Ln and the terminal surface Mn, and creating a reference point at their intersection as the last key point Pn.

5. The method for solving the bend radius according to claim 1, specifically comprising the following steps: (1) obtaining any one curved surface in the key surface, traversing the two circles on the edge of the curved surface, selecting the center of any one circle as point O, and creating an auxiliary reference point; (2) calculating the included angle Beta formed by the central axes of rotation of the two adjacent cylindrical surfaces of the curved surface; (3) when the included angle Beta is not 0° or 180°, the bend radius = tan(0.5*Beta)*OB, where point B represents the intersection of the central axes of rotation of the two adjacent cylindrical surfaces of the curved surface, and OB represents the length of the line connecting point O and point B; when 0°≤Beta≤1° or 179°≤Beta≤180°, the bend radius is equal to half the distance between the two adjacent central axes of rotation of the curved surface.

6. The method for creating a centerline of the tubular three-dimensional model according to claim 1, by sequentially connecting key points to draw line segments, drawing round corners, setting the round corner radius equal to the bend radius, and completing the rough sketch of the centerline.

7. The method of claim 4, wherein when the included angle of the two adjacent rotation center axes is 0°≤Beta≤1° or 179°≤Beta≤180°, a key point is additionally inserted, and the method comprises the following steps: From the starting surface M1, all the curved surfaces in the key surfaces are sequentially marked as N1, N2,..., Ni-1, Ni,..., Nn-1, Nn; From the group of rotation center axes Ln, Ln-1, to the group of rotation center axes L2, L1, the included angle Beta of the two adjacent rotation center axes is measured, and when 0°≤Beta≤1° or 179°≤Beta≤180°, the curved surface Ni-1 between the rotation center axes Li-1 and Li is determined as a U-shaped curved surface; The edges of the U-shaped curved surface are traversed to find two circles on the edges, and the centers Oi, Oi-1 of the two circles are created as auxiliary reference points, wherein the point Oi is on the rotation center axis Li, and the point Oi-1 is on the rotation center axis Li-1; Take the key point Pi and the key point Pi-1; offset the point Oi in the direction of , and the offset length is equal to the bending radius, and the offset point is Ki; offset the point Oi-1 in the direction of , and the offset length is equal to the bending radius, and the offset point is Ki-1; insert the point Ki-1 and the point Ki into the key point group, and the order of the inserted key points is: P1, P2, …, Pi-1, Ki-1, Ki, Pi, …, Pn-1, Pn; All the U-shaped curved surfaces are found and processed according to the above operation.

8. Any one of the curved surfaces of claim 5, characterized in that: The curved surface is a curved surface other than a plane, a cylindrical surface and a conical surface.

9. The method of claim 5, wherein: If there is no curved surface in the key surface, the method directly returns without solving the bending radius.

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