CN104615078B - Method for recognizing characteristics of bending side of aircraft sheet metal based on topological adjacent performance - Google Patents

Abstract

The invention relates to a feature recognition method for aircraft sheet metal flanges based on topological adjacency, and belongs to the technical field of aircraft digital advanced manufacturing. The method includes the following steps: 1) identification of topological adjacency of two surfaces; 2) classification and identification of bending arcs; 3) identification of curved edges; wherein, identification of topological adjacency of two surfaces includes (1) definition of topological adjacency of two surfaces; (2) First-level classification recognition; (3) Second-level classification recognition; bending arc classification and identification, including (1) bending arc classification; (2) bending arc identification; this method assumes that two topological surfaces are composed of a The edge line shared by the two topological faces is the bend line, which is produced after the original face is bent. Using the expression form of the bend line, the topological connection of the two faces is defined, and then the automatic identification of the bent edge features is realized. The method can effectively solve the identification of the flange surface, and provides a basis for automatic calculation of the key parameters of the flange feature surface, thereby reducing the workload of user interaction and effectively improving work efficiency.

Description

Feature recognition method of aircraft sheet metal flange based on topological adjacency

technical field

The invention relates to a method for recognizing a feature of a bending edge of an aircraft sheet metal part. The method can quickly recognize the bending edge features of aircraft sheet metal parts, and belongs to the technical field of aircraft digital advanced manufacturing.

Background technique

The bending feature is the bending surface of the aircraft sheet metal part, which is generally the bonding part when connecting with other parts. Due to the complexity of the aircraft structure, the bending feature of the sheet metal part is generally non-planar.

At present, the design of sheet metal parts of various domestic aviation manufacturing enterprises has entered the digital age, but the processing and manufacturing of sheet metal parts is still in the state of the coexistence of CNC machining and traditional technology. It is still necessary to know the key parameters of the flange feature, especially the typical angle, height, bending radius, etc., which need to be marked in the 3D feature tree and 2D drawings, and the marking of these parameters is basically still in the way of manual interaction. , it is necessary to manually identify the flange features and perform a large number of interactive operations to calculate these parameters. The process is cumbersome and inefficient.

Contents of the invention

In order to solve the above problems, the present invention provides a method for recognizing the features of bending of aircraft sheet metal parts based on topological adjacency. The method assumes that two topological surfaces are produced by bending an original surface, and the two topological surfaces share the same The edge line is the bend line. Using the expression form of the bend line, the topological adjacency of the two sides is defined, and then the automatic recognition of the bend feature is realized. This method has important practical value for the annotation and template design of aircraft sheet metal parts .

The edge feature recognition method proposed by the present invention originates from the assumption that two topological surfaces of an aircraft sheet metal part are formed by bending an original surface and the analysis of sheet metal process knowledge.

The specific plan is as follows:

A method for feature recognition of aircraft sheet metal flanges based on topological adjacency, characterized in that it comprises the following steps: 1) recognition of topological adjacency on both sides; 2) classification and recognition of bending arcs; 3) recognition of flange faces;

The step 1) two-face topological adjacency identification, including (1) two-face topological adjacency definition; (2) first-level classification identification; (3) second-level classification identification;

(1) Definition of topological adjacency of two surfaces: assuming that two topological surfaces are produced by bending an original surface, according to the form of the two topological surfaces at the bend, the topological adjacency of two surfaces is defined: including first-level classification, Secondary classification;

Among them, the primary classification;

<1.1>Concave edge: the tangent plane at any point on the bending line is inside the solid body;

<1.2> Convex edge: the cut surface at any point on the bending line is outside the entity;

<1.3> Cutting edge: the tangent plane at any point on the bending line is tangent to the two topological planes;

Among them, the trimming type can be further classified into two levels according to the concave-convexity of the relative bending line of the two topological surfaces;

<2.1> Double flat trimming: the tangent plane at any point on the bending line is tangent to and coincides with the two topological planes;

<2.2> Flat and concave trimming: the tangent plane at any point on the bending line is tangent to two topological faces and coincides with a topological face, and the tangent plane is inside the entity of the non-coincident topological face;

<2.3> Plane-convex trimming: the tangent plane at any point on the bending line is tangent to two topological faces and coincides with one topological face, and the tangent face is outside the entity of the non-coincident topological face;

<2.4>Concave-convex trimming: the tangent plane at any point on the bending line is tangent to the two topological surfaces, and does not coincide with the topological surfaces. The tangent plane is inside the entity of one topological surface and outside the entity of the other topological surface;

<2.5> Double concave trimming: the tangent plane at any point on the bending line is tangent to the two topological surfaces, and does not coincide with the topological surfaces, and the tangent plane is inside the entity of the two topological surfaces;

<2.6> Double convex trimming: the tangent surface at any point on the bending line is tangent to the two topological surfaces, and does not coincide with the topological surfaces, and the tangent surface is outside the entity of the two topological surfaces;

The above (2) first-level classification recognition: using the form of bending lines to identify the topological adjacency of two sides, the specific method is:

① Obtain the common edge of two adjacent topological surfaces F ₁ and F ₂ , that is, the bending line, and take the midpoint P _f of the edge;

② Obtain the in vitro normal vectors V ₁ and V ₂ of the midpoint P _f in F ₁ and F ₂ through the built-in interface of the CAA component application architecture;

③Calculate the tangent vector V _t1 in the counterclockwise direction at the midpoint P _f when the bending line belongs to the surface F ₁ , (according to the counterclockwise direction along the bending line, take the adjacent point P _Δf1 (t ₀ +Δt) of P _f (t ₀ ) ), V _t1 = P _Δf1 (t ₀ +Δt)-P _f (t ₀ )), calculate the tangent vector V _t2 in the counterclockwise direction at the midpoint P _f when the bending line belongs to the surface F ₂ , (along the bending Take the adjacent point P _Δf2 (t ₀ +Δt) of P _f (t ₀ ) in the counterclockwise direction of the line, V _t2 =P _Δf2 (t ₀ +Δt)-P _f (t ₀ ));

④ Calculate the normal vectors V _n1 and V _n2 at the midpoint P _f when the bending line belongs to two topological surfaces respectively;

V _n1 =V ₁ ×V _t1 V _n2 =V ₂ ×V _t2

⑤ Calculate the counterclockwise angle θ between the two normal vectors V _n1 to V _n2 when V _t1 is used as a reference, the process is:

a. Obtain the cross product V _s of V _n1 to V _n2 , that is, the plane Ax+By+Cz+D=0 formed by V _n1 and V _n2 , if the angle between V _s and V _t1 is greater than 90 degrees, V _n1 and V _n2 interchange;

b. Move the coordinates of V _n1 along V _s for a certain distance to obtain a point P _n1 (x ₀ , y ₀ , z ₀ ) out of the plane;

c. The projection line equation of point P _n1 to the plane is Transformed into a parametric equation to get x=x ₀ -At, y=y ₀ -Bt, z=z ₀ -Ct, substituting into the plane equation to obtain Substituting t into the projection line parameter equation can obtain the two-dimensional vector V _n1 ' of V _n1 in the plane, and similarly obtain the two-dimensional vector V _n2 ' of V _n2 in the plane;

d. Extract the coordinates (a, b) of V _n1 ', and obtain the vertical vector V _n1 "(b, -a) of V _n1 ';

e. Calculate the angle θ ₁ between V _n1 ' and V _n2 ', if θ ₁ is equal to 180 degrees, then θ=θ ₁ ;

f. Otherwise, calculate the angle θ ₂ between V _n1 ″ and V _n2 ′, if θ ₂ is less than 90 degrees, then θ=θ ₁ +180, otherwise θ=θ ₁ ;

If θ is less than 180 degrees, the topological adjacency form of two faces is a concave edge;

If θ is greater than 180 degrees, the topological adjacency form of two faces is a convex edge;

If θ is equal to 180 degrees, the topological adjacency form of two surfaces is tangent;

Described (3) two-level classification identification: on the basis of the first-level classification identification, keep the in vitro normal vectors V ₁ and V ₂ as the benchmarks for further identification, obtain the concave vector at the midpoint of the topological surface, and compare them with the two Calculate the included angle between the normal vectors V ₁ and V ₂ outside the topological surface, and judge according to the included angle value. The specific method is as follows:

① If the topological adjacency form of two surfaces is tangent, record the normal vector V ₁ as V _f1 and V ₂ as V _f2 ;

② Calculate the normal plane F _f at the middle point P _f of the bending line;

③ Intersect the normal plane F _f with the surfaces F ₁ and F ₂ respectively, and obtain the intersecting lines L ₁ and L ₂ of the intersection results;

④ Obtain midpoints P ₁ and P ₂ of intersection lines L ₁ and L ₂ ;

⑤ Calculate the curvatures C ₁ and C ₂ at the midpoints P ₁ and P ₂ ;

⑥If C ₁ and C ₂ are less than the critical value Q, and Q takes _a value of 1.0e _{+ 5} , _{obtain the principal normal vector V mn1 and} V _mn2 ;

⑦ Calculate the angle θ ₁ between vector V _f1 and V _mn1 and the angle θ ₂ between V _f2 and V _mn2 respectively;

⑧According to the comparison of curvature and included angle, the results of secondary classification and identification are as follows:

If both C ₁ and C ₂ are greater than Q, then the topological adjacency form of two faces is double flat tangent edge;

If C ₁ is greater than Q, C ₂ is less than Q, and θ ₂ is less than 90 degrees, then the topological adjacency form of two faces is plano-concave trimming;

If C ₂ is greater than Q, C ₁ is less than Q, and θ ₁ is less than 90 degrees, then the topological adjacency form of two faces is plano-concave trimming;

If C ₁ is greater than Q, C ₂ is less than Q, and θ ₂ is greater than 90 degrees, then the topological adjacency form of two faces is plano-convex trimming;

If C ₂ is greater than Q, C ₁ is less than Q, and θ ₁ is greater than 90 degrees, then the topological adjacency form of two faces is plano-convex trimming;

If both C ₁ and C ₂ are less than Q, and θ ₁ is greater than 90 degrees, and θ ₂ is less than 90 degrees, then the topological adjacency form of the two surfaces is concave-convex trimming;

If both C ₁ and C ₂ are less than Q, and θ ₁ is less than 90 degrees, and θ ₂ is greater than 90 degrees, then the topological adjacency form of the two surfaces is concave-convex trimming;

If both C ₁ and C ₂ are less than Q, and both θ ₁ and θ ₂ are less than 90 degrees, then the topological adjacency form of two surfaces is biconcave trimming;

If both C ₁ and C ₂ are less than Q, and both θ ₁ and θ ₂ are greater than 90 degrees, then the topological adjacency form of two faces is biconvex tangent.

The step 2) classification and identification of bending arcs includes (1) classification of bending arcs; (2) identification of bending arcs;

The above (1) classification of bending arcs: bending arcs are the transition arcs between the web surface and the flange surface, and are the bridge between the web surface and the flange surface, which can be divided into Concave type and convex type;

(2) Recognition of the bending arc: intersect the to-be-discriminated topological surface F _dp with the web surface F _fb , if successful, obtain the common bending line of both sides, and take the middle point P _f of the bending line; calculate In vitro normal vectors V _dp and V _fb of the midpoint P _f in the surfaces F _dp and F _fb ; calculate the tangent vector V _tdp in the counterclockwise direction at the midpoint P _f when the bending line belongs to F _dp , and calculate the bending line Tangent vector V _tfb counterclockwise at the midpoint P _f when it belongs to F _fb ; calculate the normal vectors V _ndp and V _nfb at the midpoint P _f when the bending line belongs to two topological surfaces respectively; calculate the two normal vectors The counterclockwise angle θ between V _ndp and V _nfb when V _tdp is used as a reference. If θ is equal to 180 degrees, the topological surface to be judged is a bending arc; calculate the normal plane F _f at the middle point P _f of the bending line ; Intersect F _f and F _dp to obtain the intersection result intersection line L _dp ; Calculate the principal normal vector V _mndp at the midpoint P _dp of L _dp ; Calculate the angle θ between the vector V _dp and V _mndp , if θ is less than 90 degrees, the bending arc is concave; if θ is greater than 90 degrees, the bending arc is convex.

Step 3) Flange face recognition: intersect the to-be-discriminated topological surface F _dp with the convex bending arc F _zw , if successful, obtain the common bending line of both sides, and take the midpoint P of the bending line _f ; calculate the external normal vector V _dp and V _zw of the midpoint P _f in the surface F _dp and F _zw ; calculate the tangent vector V _tdp in the counterclockwise direction at the midpoint P _f when the bending line belongs to F _dp , and calculate When the bending line belongs to F _zw , the tangent vector V _tzw in the counterclockwise direction at the midpoint P _f is calculated; when the bending line belongs to two topological surfaces, the normal vectors V _ndp and V _nzw at the midpoint P _f are calculated; the two The counterclockwise angle θ between the normal vector V _ndp and V _nzw when V _tdp is used as a reference. If θ is equal to 180 degrees, the topological surface to be identified is a curved edge surface.

Beneficial effects of the present invention: According to the topological adjacency identification of two adjacent surfaces, the present invention further expands the form of topological adjacency in detail, effectively solves the identification of the flange surface, and is the key to automatically calculate the feature surface of the flange Parameters provide a basis, thereby reducing the workload of user interaction and effectively improving work efficiency.

Description of drawings

Figure 1 is a schematic diagram of the bending features of aircraft sheet metal parts.

Figure 2 is a schematic diagram of two-face topological adjacency calculation.

Figure 3 is the general flowchart of edge feature recognition.

Fig. 4 is a flow chart of two-face topological adjacency first-level classification identification.

Fig. 5 is a flow chart of the two-surface topological adjacency two-level classification identification.

Figure 6 is a two-face topological adjacency classification diagram.

Figures 7-1 to 7-9 are two-sided topological adjacency diagrams.

detailed description

A feature recognition method for aircraft sheet metal flanges based on topological adjacency, including the following steps: 1) two-sided topological adjacency recognition; 2) bending arc classification and recognition; 3) flange surface recognition; (as shown in Figure 1 Show)

The step 1) two-face topological adjacency identification, including (1) two-face topological adjacency definition; (2) first-level classification identification; (3) second-level classification identification;

(1) Definition of topological adjacency of two surfaces: assuming that two topological surfaces are produced by bending an original surface, according to the form of the two topological surfaces at the bend, the topological adjacency of two surfaces is defined: including first-level classification, Secondary classification; (as shown in Figure 6)

Among them, the primary classification;

<1.1>Concave edge: the cut surface at any point on the bending line is inside the solid; as shown in Figure 7-1;

<1.2> Convex edge: the cut surface at any point on the bending line is outside the entity; as shown in Figure 7-2;

<1.3> Trimming: the tangent plane at any point on the bending line is tangent to the two topological planes; as shown in Figure 7-3;

Among them, the trimming type can be further classified into two levels according to the concave-convexity of the relative bending line of the two topological surfaces;

<2.1> Double flat trimming: the tangent plane at any point on the bending line is tangent to and coincides with two topological planes; as shown in Figure 7-4;

<2.2> Flat-concave trimming: the tangent plane at any point on the bending line is tangent to two topological surfaces and coincides with one topological surface, and the tangent plane is inside the entity of the non-coincident topological surface; as shown in Figure 7-5;

<2.3> Flat-convex edge trimming: the tangent plane at any point on the bending line is tangent to two topological surfaces and coincides with a topological surface, and the tangent plane is outside the entity of the non-coincident topological surface; as shown in Figure 7-6;

<2.4>Concave-convex trimming: the tangent plane at any point on the bending line is tangent to the two topological surfaces, and does not coincide with the topological surfaces. The tangent plane is inside the entity of one topological surface and outside the entity of the other topological surface; as shown in Figure 7- as shown in 7;

<2.5> Double concave trimming: the tangent plane at any point on the bending line is tangent to the two topological surfaces, and does not coincide with the topological surfaces, and the tangent plane is inside the entity of the two topological surfaces; as shown in Figure 7-8;

<2.6> Double convex trimming: the tangent plane at any point on the bending line is tangent to the two topological surfaces, and does not coincide with the topological surfaces, and the tangent plane is outside the entity of the two topological surfaces; as shown in Figure 7-9;

The (2) first-level classification identification: use the form of bending lines to identify the topological adjacency of two sides, the specific method is: (as shown in Figure 2)

① Obtain the common edge of two adjacent topological surfaces F ₁ and F ₂ , that is, the bending line, and take the midpoint P _f of the edge;

② Obtain the in vitro normal vectors V ₁ and V ₂ of the midpoint P _f in F ₁ and F ₂ through the built-in interface of the CAA component application architecture;

③Calculate the tangent vector V _t1 in the counterclockwise direction at the midpoint P _f when the bending line belongs to the surface F ₁ , (according to the counterclockwise direction along the bending line, take the adjacent point P _Δf1 (t ₀ +Δt) of P _f (t ₀ ) ), V _t1 = P _Δf1 (t ₀ +Δt)-P _f (t ₀ )), calculate the tangent vector V _t2 in the counterclockwise direction at the midpoint P _f when the bending line belongs to the surface F ₂ , (along the bending Take the adjacent point P _Δf2 (t ₀ +Δt) of P _f (t ₀ ) in the counterclockwise direction of the line, V _t2 =P _Δf2 (t ₀ +Δt)-P _f (t ₀ ));

④ Calculate the normal vectors V _n1 and V _n2 at the midpoint P _f when the bending line belongs to two topological surfaces respectively;

V _n1 =V ₁ ×V _t1 V _n2 =V ₂ ×V _t2

⑤ Calculate the counterclockwise angle θ between the two normal vectors V _n1 to V _n2 when V _t1 is used as a reference, the process is:

a. Obtain the cross product V _s of V _n1 to V _n2 , that is, the plane Ax+By+Cz+D=0 formed by V _n1 and V _n2 , if the angle between V _s and V _t1 is greater than 90 degrees, V _n1 and V _n2 interchange;

b. Move the coordinates of V _n1 along V _s for a certain distance to obtain a point P _n1 (x ₀ , y ₀ , z ₀ ) out of the plane;

c. The projection line equation of point P _n1 to the plane is Transformed into a parametric equation to get x=x ₀ -At, y=y ₀ -Bt, z=z ₀ -Ct, substituting into the plane equation to obtain Substituting t into the projection line parameter equation can obtain the two-dimensional vector V _n1 ' of V _n1 in the plane, and similarly obtain the two-dimensional vector V _n2 ' of V _n2 in the plane;

d. Extract the coordinates (a, b) of V _n1 ', and obtain the vertical vector V _n1 "(b, -a) of V _n1 ';

e. Calculate the angle θ ₁ between V _n1 ' and V _n2 ', if θ ₁ is equal to 180 degrees, then θ=θ ₁ ;

f. Otherwise, calculate the angle θ ₂ between V _n1 ″ and V _n2 ′, if θ ₂ is less than 90 degrees, then θ=θ ₁ +180, otherwise θ=θ ₁ ;

If θ is less than 180 degrees, the topological adjacency form of two faces is a concave edge;

If θ is greater than 180 degrees, the topological adjacency form of two faces is a convex edge;

If θ is equal to 180 degrees, the topological adjacency form of two surfaces is tangent;

Described (3) two-level classification identification: on the basis of the first-level classification identification, keep the in vitro normal vectors V ₁ and V ₂ as the benchmarks for further identification, obtain the concave vector at the midpoint of the topological surface, and compare them with the two Calculate the included angle between the normal vectors V ₁ and V ₂ outside the topological surface, and judge according to the included angle value. The specific method is as follows:

① If the topological adjacency form of two surfaces is tangent, record the normal vector V ₁ as V _f1 and V ₂ as V _f2 ;

② Calculate the normal plane F _f at the middle point P _f of the bending line;

③ Intersect the normal plane F _f with the surfaces F ₁ and F ₂ respectively, and obtain the intersecting lines L ₁ and L ₂ of the intersection results;

④ Obtain midpoints P ₁ and P ₂ of intersection lines L ₁ and L ₂ ;

⑤ Calculate the curvatures C ₁ and C ₂ at the midpoints P ₁ and P ₂ ;

⑥If C ₁ and C ₂ are less than the critical value Q, and Q takes _a value of 1.0e _{+ 5} , _{obtain the principal normal vector V mn1 and} V _mn2 ;

⑦ Calculate the angle θ ₁ between vector V _f1 and V _mn1 and the angle θ ₂ between V _f2 and V _mn2 respectively;

⑧According to the comparison of curvature and included angle, the results of secondary classification and identification are as follows:

If both C ₁ and C ₂ are greater than Q, then the topological adjacency form of two faces is double flat tangent edge;

If C ₁ is greater than Q, C ₂ is less than Q, and θ ₂ is less than 90 degrees, then the topological adjacency form of two faces is plano-concave trimming;

If C ₂ is greater than Q, C ₁ is less than Q, and θ ₁ is less than 90 degrees, then the topological adjacency form of two faces is plano-concave trimming;

If C ₁ is greater than Q, C ₂ is less than Q, and θ ₂ is greater than 90 degrees, then the topological adjacency form of two faces is plano-convex trimming;

If C ₂ is greater than Q, C ₁ is less than Q, and θ ₁ is greater than 90 degrees, then the topological adjacency form of two faces is plano-convex trimming;

If both C ₁ and C ₂ are less than Q, and θ ₁ is greater than 90 degrees, and θ ₂ is less than 90 degrees, then the topological adjacency form of the two surfaces is concave-convex trimming;

If both C ₁ and C ₂ are less than Q, and θ ₁ is less than 90 degrees, and θ ₂ is greater than 90 degrees, then the topological adjacency form of the two surfaces is concave-convex trimming;

If both C ₁ and C ₂ are less than Q, and both θ ₁ and θ ₂ are less than 90 degrees, then the topological adjacency form of two surfaces is biconcave trimming;

If both C ₁ and C ₂ are less than Q, and both θ ₁ and θ ₂ are greater than 90 degrees, then the topological adjacency form of two faces is biconvex tangent.

The step 2) classification and identification of bending arcs includes (1) classification of bending arcs; (2) identification of bending arcs;

The above (1) classification of bending arcs: bending arcs are the transition arcs between the web surface and the flange surface, and are the bridge between the web surface and the flange surface, which can be divided into Concave type and convex type;

(2) Recognition of the bending arc: intersect the to-be-discriminated topological surface F _dp with the web surface F _fb , if successful, obtain the common bending line of both sides, and take the middle point P _f of the bending line; calculate In vitro normal vectors V _dp and V _fb of the midpoint P _f in the surfaces F _dp and F _fb ; calculate the tangent vector V _tdp in the counterclockwise direction at the midpoint P _f when the bending line belongs to F _dp , and calculate the bending line Tangent vector V _tfb counterclockwise at the midpoint P _f when it belongs to F _fb ; calculate the normal vectors V _ndp and V _nfb at the midpoint P _f when the bending line belongs to two topological surfaces respectively; calculate the two normal vectors The counterclockwise angle θ between V _ndp and V _nfb when V _tdp is used as a reference. If θ is equal to 180 degrees, the topological surface to be judged is a bending arc; calculate the normal plane F _f at the middle point P _f of the bending line ; Intersect F _f and F _dp to obtain the intersection result intersection line L _dp ; Calculate the principal normal vector V _mndp at the midpoint P _dp of L _dp ; Calculate the angle θ between the vector V _dp and V _mndp , if θ is less than 90 degrees, the bending arc is concave; if θ is greater than 90 degrees, the bending arc is convex.

Step 3) Flange face recognition: intersect the to-be-discriminated topological surface F _dp with the convex bending arc F _zw , if successful, obtain the common bending line of both sides, and take the midpoint P of the bending line _f ; calculate the external normal vector V _dp and V _zw of the midpoint P _f in the surface F _dp and F _zw ; calculate the tangent vector V _tdp in the counterclockwise direction at the midpoint P _f when the bending line belongs to F _dp , and calculate When the bending line belongs to F _zw , the tangent vector V _tzw in the counterclockwise direction at the midpoint P _f is calculated; when the bending line belongs to two topological surfaces, the normal vectors V _ndp and V _nzw at the midpoint P _f are calculated; the two The counterclockwise angle θ between the normal vector V _ndp and V _nzw when V _tdp is used as a reference. If θ is equal to 180 degrees, the topological surface to be identified is a curved edge surface.

Applications:

This example is carried out on the premise of the aforementioned technical solutions.

Fig. 3 shows the specific process of the aircraft sheet metal part flange feature recognition method proposed by the present invention, and its implementation steps are: 1) loading the web surface (S1); 2) extracting the adjacent edge and adjacent surface of the web surface (S2 ); 3) identifying the convex bending arc (S3); 4) extracting the adjacent edge and adjacent surface of the bending arc (S4); 5) identifying the bending surface (S5); wherein:

The step 1) loads the web surface (S1), that is, selects the topological surface as the web surface in the model space;

Step 2) Extract the adjacent edge and adjacent surface of the web surface (S2), that is, the topological surface that successfully intersects with the web surface in the model space is the adjacent surface of the web, and the edge shared by the adjacent surface and the web surface is the bend line;

Step 3) Identify the convex bending arc (S3), that is, judge that the topological adjacency mode between the web surface and its adjacent surface is tangent, and the adjacent surface type is convex. The specific method is as follows:

(1) To identify whether the topological adjacency of two surfaces is tangent (as shown in Figure 4): firstly, obtain the bending line common to the topological surface F ₁ to be judged and the web surface F ₂ , and take the midpoint of the bending line P _f ( S6); Calculate the external normal vectors V ₁ and V ₂ of the midpoint P _f in the surfaces F ₁ and F ₂ (S7); calculate the tangent in the counterclockwise direction at the midpoint P _f when the bending line belongs to the surface F ₁ Vector V _t1 , calculate the tangent vector V _t2 (S8) in the counterclockwise direction at the midpoint P _f when the bending line belongs to the surface F ₂ ; calculate the normal direction at the midpoint P _f when the bending line belongs to two topological surfaces respectively Vector V _n1 , V _n2 (S9); calculate the counterclockwise angle θ (S10) between the two normal vectors V _n1 to V _n2 when V _t1 is used as a reference, if θ is equal to 180 degrees, the topological surface to be judged is folded Bend the arc (S11), keep it for further identification;

(2) Identify whether the adjacent surface type is convex (as shown in Figure 5): record the normal vector V ₁ as V _f1 , and V ₂ as V _f2 (S12); calculate the normal plane F at the midpoint P _f of the bending line _f (S13); intersect the normal plane F _f with the surfaces F ₁ and F ₂ respectively, and obtain the intersecting results intersection lines L ₁ and L ₂ (S14); calculate the midpoints P ₁ and P ₂ of L ₁ and L ₂ ; Calculate the curvature C ₁ , C ₂ at the midpoint P ₁ , P ₂ (S15); if C ₁ , C ₂ are greater than the critical value Q, then the F ₁ , F ₂ surfaces are flat (S16), otherwise calculate the intersection Principal normal vectors V _mn1 and V _mn2 at midpoints P ₁ and P ₂ of lines L ₁ and L ₂ (S17); respectively calculate the included angles between vectors V _f1 and V _mn1 , V _f2 and V _mn2 , if the included angle is greater than 90 degree, then this topological surface is a convex bending arc (S19);

Step 4) Obtain the adjacent edge and adjacent surface of the bending arc (S4), that is, the topological surface that successfully intersects the bending arc in the model space, and is not the web surface, that is, the adjacent surface of the bending arc, and the adjacent surface and The edge shared by the bending arc is the bending line;

Step ₅ ) Flange surface identification (S5), that is, to determine whether the topological adjacency _of the bending arc and its adjacent surface is tangent. Bending line, take the middle point P _f of the bending line (S6); calculate the external normal vectors V ₁ and V ₂ of the midpoint P _f in the surfaces F ₁ and F ₂ (S7); calculate the bending line belonging to the surface F ₁ tangent vector V _t1 in the counterclockwise direction at the midpoint P _f when calculating the bending line belongs to the surface F ₂ tangent vector V _t2 in the counterclockwise direction at the midpoint P _f (S8); The normal vectors V _n1 and V _n2 (S9) at the midpoint P _f of the topological surface; calculate the counterclockwise angle θ (S10) of the two normal vectors V _n1 to V _n2 when V _t1 is used as a reference, if θ is equal to 180 degrees, then the topological surface to be judged is a curved surface (S11).

Claims (3)

1. A feature recognition method for aircraft sheet metal flanges based on topological adjacency, characterized in that it comprises the steps of: 1) two-sided topological adjacency recognition; 2) bending arc classification and recognition; 3) flange face recognition ; The step 1) two-face topological adjacency identification, including (1) two-face topological adjacency definition; (2) first-level classification identification; (3) second-level classification identification; (1) Definition of topological adjacency of two surfaces: assuming that two topological surfaces are produced by bending an original surface, according to the form of the two topological surfaces at the bend, the topological adjacency of two surfaces is defined: including first-level classification, Secondary classification; Among them, the primary classification; <1.1>Concave edge: the tangent plane at any point on the bending line is inside the solid body; <1.2> Convex edge: the cut surface at any point on the bending line is outside the entity; <1.3> Cutting edge: the tangent plane at any point on the bending line is tangent to the two topological planes; Among them, the trimming type can be further classified into two levels according to the concave-convexity of the relative bending line of the two topological surfaces; <2.1> Double flat trimming: the tangent plane at any point on the bending line is tangent to and coincides with the two topological planes; <2.2> Flat and concave trimming: the tangent plane at any point on the bending line is tangent to two topological faces and coincides with a topological face, and the tangent plane is inside the entity of the non-coincident topological face; <2.3> Plane-convex trimming: the tangent plane at any point on the bending line is tangent to two topological faces and coincides with one topological face, and the tangent face is outside the entity of the non-coincident topological face; <2.4>Concave-convex trimming: the tangent plane at any point on the bending line is tangent to the two topological surfaces, and does not coincide with the topological surfaces. The tangent plane is inside the entity of one topological surface and outside the entity of the other topological surface; <2.5> Double concave trimming: the tangent plane at any point on the bending line is tangent to the two topological surfaces, and does not coincide with the topological surfaces, and the tangent plane is inside the entity of the two topological surfaces; <2.6> Double convex trimming: the tangent surface at any point on the bending line is tangent to the two topological surfaces, and does not coincide with the topological surfaces, and the tangent surface is outside the entity of the two topological surfaces; The above (2) first-level classification recognition: using the form of bending lines to identify the topological adjacency of two sides, the specific method is: ① Obtain the common edge of two adjacent topological surfaces F ₁ and F ₂ , that is, the bending line, and take the midpoint P _f of the edge; ② Obtain the in vitro normal vectors V ₁ and V ₂ of the midpoint P _f in F ₁ and F ₂ through the built-in interface of the CAA component application architecture; ③Calculate the tangent vector V _t1 in the counterclockwise direction at the midpoint P _f when the bending line belongs to the surface F ₁ , and take the adjacent point P _Δf1 (t ₀ +Δt) of P _f (t ₀ ) in the counterclockwise direction along the bending line , V _t1 ＝P _Δf1 (t ₀ +Δt)-P _f (t ₀ ), calculate the tangent vector V _t2 in the counterclockwise direction at the midpoint P _f when the bending line belongs to the surface F ₂ , counterclockwise along the bending line The direction is taken as the adjacent point P _Δf2 (t ₀ +Δt) of P _f (t ₀ ), V _t2 =P _Δf2 (t ₀ +Δt)-P _f (t ₀ ); ④ Calculate the normal vectors V _n1 and V _n2 at the midpoint P _f when the bending line belongs to two topological surfaces respectively; V _n1 =V ₁ ×V _t1 V _n2 =V ₂ ×V _t2 ⑤ Calculate the counterclockwise angle θ between the two normal vectors V _n1 to V _n2 when V _t1 is used as a reference, the process is: a. Obtain the cross product V _s of V _n1 to V _n2 , that is, the plane Ax+By+Cz+D=0 formed by V _n1 and V _n2 , if the angle between V _s and V _t1 is greater than 90 degrees, V _n1 and V _n2 interchange; b. Move the coordinates of V _n1 along V _s for a certain distance to obtain a point P _n1 (x ₀ , y ₀ , z ₀ ) out of the plane; c. The projection line equation of point P _n1 to the plane is Transformed into a parametric equation to get x=x ₀ -At, y=y ₀ -Bt, z=z ₀ -Ct, substituting into the plane equation to obtain Substituting t into the projection line parameter equation can obtain the two-dimensional vector V _n1 ' of V _n1 in the plane, and similarly obtain the two-dimensional vector V _n2 ' of V _n2 in the plane; d. Extract the coordinates (a, b) of V _n1 ', and obtain the vertical vector V _n1 "(b, -a) of V _n1 '; e. Calculate the angle θ ₁ between V _n1 ' and V _n2 ', if θ ₁ is equal to 180 degrees, then θ=θ ₁ ; f. Otherwise, calculate the angle θ ₂ between V _n1 ″ and V _n2 ′, if θ ₂ is less than 90 degrees, then θ=θ ₁ +180, otherwise θ=θ ₁ ; If θ is less than 180 degrees, the topological adjacency form of two faces is a concave edge; If θ is greater than 180 degrees, the topological adjacency form of two faces is a convex edge; If θ is equal to 180 degrees, the topological adjacency form of two surfaces is tangent; Described (3) two-level classification identification: on the basis of the first-level classification identification, keep the in vitro normal vectors V ₁ and V ₂ as the benchmarks for further identification, obtain the concave vector at the midpoint of the topological surface, and compare them with the two Calculate the included angle between the normal vectors V ₁ and V ₂ outside the topological surface, and judge according to the included angle value. The specific method is as follows: ① If the topological adjacency form of two surfaces is tangent, record the normal vector V ₁ as V _f1 and V ₂ as V _f2 ; ② Calculate the normal plane F _f at the middle point P _f of the bending line; ③ Intersect the normal plane F _f with the surfaces F ₁ and F ₂ respectively, and obtain the intersecting lines L ₁ and L ₂ of the intersection results; ④ Obtain midpoints P ₁ and P ₂ of intersection lines L ₁ and L ₂ ; ⑤ Calculate the curvatures C ₁ and C ₂ at the midpoints P ₁ and P ₂ ; ⑥If C ₁ and C ₂ are less than the critical value Q, and Q takes _a value of 1.0e _{+ 5} , _{obtain the principal normal vector V mn1 and} V _mn2 ; ⑦ Calculate the angle θ ₁ between vector V _f1 and V _mn1 and the angle θ ₂ between V _f2 and V _mn2 respectively; $\begin{array}{cc}\mathrm{<span\; class="notranslate">\; c</span>}\mathrm{<span\; class="notranslate">\; o</span>}\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{<span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}\mathrm{<span\; class="notranslate">\; no</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; |</span>}{<span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; |</span><span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}\mathrm{<span\; class="notranslate">\; no</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; |</span>}& \mathrm{<span\; class="notranslate">\; c</span>}\mathrm{<span\; class="notranslate">\; o</span>}\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{<span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}\mathrm{<span\; class="notranslate">\; no</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; |</span>}{<span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; |</span><span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}\mathrm{<span\; class="notranslate">\; no</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; |</span>}\end{array}$ ⑧According to the comparison of curvature and included angle, the results of secondary classification and identification are as follows: If both C ₁ and C ₂ are greater than Q, then the topological adjacency form of two faces is double flat tangent edge; If C ₁ is greater than Q, C ₂ is less than Q, and θ ₂ is less than 90 degrees, then the topological adjacency form of two faces is plano-concave trimming; If C ₂ is greater than Q, C ₁ is less than Q, and θ ₁ is less than 90 degrees, then the topological adjacency form of two faces is plano-concave trimming; If C ₁ is greater than Q, C ₂ is less than Q, and θ ₂ is greater than 90 degrees, then the topological adjacency form of two faces is plano-convex trimming; If C ₂ is greater than Q, C ₁ is less than Q, and θ ₁ is greater than 90 degrees, then the topological adjacency form of two faces is plano-convex trimming; If both C ₁ and C ₂ are less than Q, and θ ₁ is greater than 90 degrees, and θ ₂ is less than 90 degrees, then the topological adjacency form of the two surfaces is concave-convex trimming; If both C ₁ and C ₂ are less than Q, and θ ₁ is less than 90 degrees, and θ ₂ is greater than 90 degrees, then the topological adjacency form of the two surfaces is concave-convex trimming; If both C ₁ and C ₂ are less than Q, and both θ ₁ and θ ₂ are less than 90 degrees, then the topological adjacency form of two surfaces is biconcave trimming; If both C ₁ and C ₂ are less than Q, and both θ ₁ and θ ₂ are greater than 90 degrees, then the topological adjacency form of two faces is biconvex tangent. 2. A method for feature recognition of aircraft sheet metal flanges based on topological adjacency according to claim 1, wherein said step 2) classification and identification of bending arcs includes (1) bending circles Arc classification; (2) Bending arc identification; The above (1) classification of bending arcs: bending arcs are the transition arcs between the web surface and the flange surface, and are the bridge between the web surface and the flange surface, which can be divided into Concave type and convex type; (2) Recognition of the bending arc: intersect the to-be-discriminated topological surface F _dp with the web surface F _fb , if successful, obtain the common bending line of both sides, and take the middle point P _f of the bending line; calculate In vitro normal vectors V _dp and V _fb of the midpoint P _f in the surfaces F _dp and F _fb ; calculate the tangent vector V _tdp in the counterclockwise direction at the midpoint P _f when the bending line belongs to F _dp , and calculate the bending line Tangent vector V _tfb counterclockwise at the midpoint P _f when it belongs to F _fb ; calculate the normal vectors V _ndp and V _nfb at the midpoint P _f when the bending line belongs to two topological surfaces respectively; calculate the two normal vectors The counterclockwise angle θ between V _ndp and V _nfb when V _tdp is used as a reference. If θ is equal to 180 degrees, the topological surface to be judged is a bending arc; calculate the normal plane F _f at the middle point P _f of the bending line ; Intersect F _f and F _dp to obtain the intersection result intersection line L _dp ; Calculate the principal normal vector V _mndp at the midpoint P _dp of L _dp ; Calculate the angle θ between the vector V _dp and V _mndp , if θ is less than 90 degrees, the bending arc is concave; if θ is greater than 90 degrees, the bending arc is convex. 3. a kind of aircraft sheet metal flanging feature recognition method based on topological adjacency according to claim 1, is characterized in that, described step 3) flanging surface identification: the topological surface F _dp to be discriminated and convex If it is successful, obtain the common bending line on both sides, and take the midpoint P _f of the bending line; calculate the _external normal vector V of the midpoint P _f on the surface F _dp and F _{zw dp} and V _zw ; calculate the tangent vector V _tdp in the counterclockwise direction at the midpoint P _f when the bending line belongs to F _dp , and calculate the tangent vector V _tzw in the counterclockwise direction at the midpoint P _f when the bending line belongs to F _zw ; Calculate the normal vectors V _ndp and V _nzw at the midpoint P _f when the bending line belongs to the two times respectively; Calculate the counterclockwise angle θ between the two normal vectors V _ndp to V _nzw when V _tdp is used as a reference, if θ is equal to 180 degrees, then the topological surface to be judged is a curved surface.