KR101640913B1

KR101640913B1 - Feature-based simplification method of CAD models using unit feature simplification and its system

Info

Publication number: KR101640913B1
Application number: KR1020150060073A
Authority: KR
Inventors: 김병철; 윤여운
Original assignee: 동아대학교 산학협력단
Priority date: 2015-04-28
Filing date: 2015-04-28
Publication date: 2016-07-19

Abstract

The present invention provides a simplification system based on features of a CAD model, comprising: a feature segmentation unit of individually classifying a plurality of features in an inputted feature-based CAD model; a feature importance calculation unit of assigning importance for each feature classified by the feature segmentation unit; a feature ordering unit for rearranging the order of the features segmented based on the importance calculated by the feature importance calculation unit; and a feature inhibition unit of inhibiting the features according to priority in the features ordered by the feature ordering unit. In the feature segmentation unit, a protrusion feature, revolution feature, sweep feature, and loft feature are classified as a two-dimensional sketch-based feature, and a variable radius fillet, pattern feature, hole feature, and shell feature are classified as a sketch-non-based feature. In addition, in the feature inhibition unit, a loop in a sketch, a concave peak of the sketch, and fillet and round of the sketch are sequentially removed with respect to one classified sketch, thereby gradually simplifying the inputted CAD model. According to the present invention, one feature is segmented and can be reconfigured by several steps, whereby the present invention is capable of gradually simplifying a CAD model, which is more segmented by each type of the feature.

Description

[TECHNICAL FIELD] The present invention relates to a feature-based simplification method and system for a CAD model,

The present invention relates to a method for simplifying the shape of a CAD model and a system therefor.

Simplification of CAD (Computer Aided Design) model is an important technology for integration between CAE (Computer Aided Engineering). It is applied to various engineering such as engineering analysis, network-based design, and virtual prototyping Used in activities.

On the other hand, the method of simplifying the shape of the CAD model can be divided into progressive, continuous, and discrete simplifications. The gradual simplification can be further divided into a mesh-based simplification, a simplification based on the boundary expression model, Based simplification.

The feature-based simplification uses a feature-based model as an input, and the feature-based model expresses a final shape by continuously applying shapes having engineering meaning called a feature shape as a logo.

The following Patent Document 1 discloses a CAD apparatus for simplifying and displaying the shape of an object. In the solid shape analysis, a large analysis time is required due to a large number of meshes, or a memory capacity shortage phenomenon is solved It is possible to automatically reduce the minute concavity and convexity and the loose curved surface which are regarded as unnecessary in the analysis accuracy, thereby making it possible to reduce the number of meshes significantly.

However, in the above-described conventional techniques, the feature is used as a minimum simplification unit. Therefore, when the whole shape is composed of a small number of features, only the additive feature is formed, or when one feature itself is a complex shape It is difficult to obtain a simplified model of the required level.

JP 2007272403 A1

SUMMARY OF THE INVENTION It is an object of the present invention to provide a feature-based simplification method of a CAD model using simplification of a unit feature shape to further refine and simplify feature features to solve the problems of the related art.

Another object of the present invention is to provide a feature-based simplification method of a CAD model using a unit feature simplification that allows different simplification methods to be applied to each feature in consideration of features of feature types.

It is still another object of the present invention to provide a feature-based simplification system of a CAD model using unit feature simplification for the above-described method.

The features-based simplification system according to the present invention includes a feature refinement unit for separately distinguishing a plurality of feature shapes from an input feature-based CAD model, and a feature providing unit for assigning importance to features classified by the feature refinement unit A characteristic shape ordering unit for rearranging the order of the feature shapes subdivided on the basis of the importance calculated according to the characteristic shape importance calculating unit and a characteristic shape sorting unit for sorting the characteristic shapes sorted by the characteristic shape ordering unit And a feature suppression unit for suppressing the feature according to the order of the features, wherein the feature refinement unit includes a protrusion feature, a revolution feature, and a sweep feature ), Loft Feature, and Variable Radius Fillet with Sketch-Based Feature a fill feature, a fill feature, a hole feature, a hole feature, a hole feature, and a shell feature, and the feature suppression section separates one sketch separated from the sketch inner loop, Vertex removal, sketch fillet and round elimination are successively applied to gradually simplify the input CAD model.

Wherein the feature importance calculating unit calculates a change in volume before and after application of simplification in one of the divided sketches so that a priority is given when the volume change is small.

The feature-based-based simplification method according to the present invention is characterized in that each feature-based refinement step of separately dividing a plurality of feature shapes in an input feature-based CAD model, a feature importance calculation step of calculating a degree of importance for each of the separated features, A feature rearranging step of rearranging the order of the feature features classified according to the feature importance calculating step and a feature suppressing step of suppressing the subdivided feature having a low importance, A sketch-based feature can be classified into a protrusion feature, a revolving feature, a sweep feature, and a loft feature. The sketch- Variable radius fillet, Pattern Feature, Hole Feature and Shell Feature. The sketch inner loop removal process, the sketch recessed vertex removal process, the sketch fillet, and the round elimination process are sequentially performed to simplify the inputted CAD model gradually. do.

If both the sketch inner loop removal process, the sketch recessed vertex removal process, and the sketch fillet and round removal process can be performed in the subdivided feature shape, .

According to the present invention, one characteristic feature can be segmented and reconstructed in various stages. Therefore, it is possible to simplify a gradual CAD model that is further subdivided according to types of feature shapes.

In addition, since the progressive CAD model can be simplified as described above, it is advantageous in that a target CAD model applicable to the feature-based simplification method is diversified.

1 is a block diagram for explaining the configuration of a feature-based simplification system of a CAD model using unit feature shape simplification according to the present invention.
FIG. 2 is a flowchart illustrating a feature-based simplification method of a CAD model using unit feature shape simplification according to the present invention.
FIG. 3 and FIG. 4 are diagrams for explaining a process of reconstructing one feature in various stages in the simplification method according to the present invention. FIG.
FIG. 5 and FIG. 6 are diagrams showing simplified features according to the present invention; FIG.
7 is a view showing an embodiment of a feature-shape suppression process according to the related art.
FIG. 8 illustrates an embodiment of a feature suppression process according to the present invention. FIG.

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. It is to be understood, however, that the spirit of the invention is not limited to the embodiments shown and that those skilled in the art, upon reading and understanding the spirit of the invention, may easily suggest other embodiments within the scope of the same concept.

FIG. 1 is a block diagram for explaining a configuration of a feature-based simplification system of a CAD model using unit feature shape simplification according to the present invention. FIG. 2 is a block diagram of a CAD model using unit feature shape simplification A flowchart for explaining a feature-based simplification method is shown.

Referring to these drawings, in the simplified system according to the present invention, a feature-based CAD model is input and a simplified CAD model is output through a plurality of function units.

To this end, the simplification system includes a feature refinement unit 100, a feature importance calculation unit 200, a feature order arrangement unit 300, and a feature shape suppression unit 400.

In detail, the feature refinement unit 100 includes a feature subdivision step S100 for dividing a plurality of feature shapes constituting a provided CAD model into individual features, Is performed.

To this end, three sketch simplification operations are applied to one feature in the present invention.

3 and 4 are diagrams for explaining a process of reconstructing one feature in various stages in the simplification method according to the present invention.

Referring to these drawings, in the present invention, a sketch simplifying operation such as inner loop elimination, concave vertex elimination, fillet and round elimination is applied to one feature to obtain more detailed simplification results.

In the sketch inner loop elimination, the sketch loops used to define the feature are examined to remove the inner loop 510 existing therein, leaving only the outer loop 520 (see FIG. 4A).

In the sketch recessed vertex removal, it is determined whether the concave vertex is a corner by using an angle between two edges having a common vertex 530, and after the concave vertex is removed, the remaining two vertices are concatenated to simplify (see FIG. 4B)

Here, the determination of the concave vertex can be determined as a concave vertex when the angle between the two edges is less than 180 degrees.

In the sketch fillet and round removal, three consecutive edges on the sketch are illuminated and the middle edge is a fillet / round 540. If both edges are straight, the fillet / round 540 is removed, The edges are extended to simplify (see Figure 4c).

If both the sketch inner loop elimination, the sketch recession vertex removal, and the sketch fillet and round elimination are both feasible in the sketch to be simplified, the volumes before and after the simplification are compared and the volume change is performed sequentially from the simplest one.

On the other hand, the sketching based shape of the sagging can be simplified for each type by using three sketch operations defined as described above.

FIGS. 5 and 6 are views showing simplified shapes of characteristic shapes according to the present invention.

Referring to these figures, in the present invention, a feature is divided into a shape having a sketch and a shape having no sketch, and a feature having a sketch is divided into a protrusion feature, a revolve feature, A sweep feature, and a loft feature.

In the case of the protrusion feature, it can be defined as one sketch, protrusion direction, and height, and the inner space is eliminated to fill the void space and the simplification proceeds. To this end, in the case of a protrusion feature, all three sketch operations described above are applied and simplified.

In the case of the Revolution Feature, it is defined as one sketch, rotation axis and rotation angle, and the simplification is performed by filling the center empty space caused by the distance between the axis and the sketch. To simplify the revolving feature, we apply the above three operations and further simplify the filling of the empty space between the rotation axis and the sketch.

In the case of the sweep feature, a profile sketch and a path sketch are provided, thereby simplifying the two sketches.

In the sweep feature sketch, the profile sketch is defined by moving along the path sketch, the profile sketch is simplified by applying all three operations described above, and applying the fillet and round elimination to the path sketch.

In the case of the Loft Feature, a plurality of sketches are concatenated to define a shape, and the above three operations are applied to all included sketches to simplify them.

On the other hand, the shape without a sketch is divided into a variable radius fillet, a pattern feature, a hole feature, and a shell feature.

In the case of the variable radius fillet, simplification is achieved by converting a fixed radius of curvature into a constant radius and attaching it to the smallest radius.

In the case of the pattern feature (Parrern Feature), the reference feature is simplified and the number of instances is reduced to simplify the feature.

In the case of the hole feature, the hole type is simply typed and simplified. For example, in the case of a hole having a counterbore, a type conversion into a hole without a widely extended counterbore is simplified (see FIG. 6).

In the case of the shell feature, the feature is suppressed and simplified. If the volume of the object to be applied in the shell feature is too large, the characteristics of the original shape may be lost.

Therefore, in the case of the shell feature, the inhibition is not proceeded when the change is more than the reference point. Here, the reference point is determined as a rate of change of volume, and can be optionally designated by the user.

As described above, the characteristic features refined by the feature refining unit 100 are calculated for each characteristic feature subdivided by the feature importance calculating unit 200.

The significance here is determined by calculating the volume change before and after applying the simplification method. In the present invention, a higher priority is given to a volume change after application than when a simplification method is applied.

When the importance degree is calculated for each feature type as described above, the feature order reordering unit 300 rearranges the order of the feature type subdivided according to the importance level (S300).

In the step of rearranging the feature (S300), each feature of the input CAD model is sorted according to priority. After the alignment is completed, the feature suppression unit (400) Step S400 is performed.

7 is a view showing an embodiment of a feature suppression process according to the related art, and FIG. 8 is a view illustrating an embodiment of a feature suppression process according to the present invention.

Referring to these drawings, when simplification is performed through the conventional technique with the same CAD model, the hole machining feature suppression, the rotation feature suppression and the sweep feature suppression are sequentially performed as shown in Fig. 7, Most of the model is deleted and output.

That is, in the case of a CAD model constituted by additive features whose entire shape is not subdivided as in the prior art, since the individual features themselves do not have a detailed shape and the feature is used as a minimum simplifying unit, A part of the shape may be deleted when the feature is composed only of the additive feature or when the feature itself has a complicated shape.

On the other hand, according to the present invention, the same CAD model is divided into four sketch feature shapes of protrusion, sweep, rotation, and hole machining, and simplification proceeds.

That is, as shown in FIG. 8, in the present invention, inner loop elimination, concave vertex removal and round elimination are performed in the protruding feature sketch, concave vertex removal in the sweep feature profile sketch, and round elimination in the sweep feature path sketch .

Then, a concave vertex removal is made in the rotation feature sketch, and a suppression of the feature in the hole machining feature sketch is made so that the final simplified CAD model compared with Fig. 7 can be output.

That is, according to the present invention, since one feature can be simplified by subdividing it by feature type, more detailed gradual CAD model can be simplified and applicable CAD model can be expanded.

100 ........ feature-shape refinement unit 200 ... ... feature-
300 ........ The feature order arranging unit 400 ........ The feature-

Claims

A feature shape subdivision unit for separately dividing a plurality of feature shapes in an input feature-based CAD model;
A feature shape importance calculating unit for assigning importance of each feature classified by the feature shape refining unit;
A feature order rearranging unit for rearranging the order of feature subdivided based on the importance calculated according to the feature importance calculating unit;
And a feature suppression unit that suppresses the feature according to the priority order of the feature features aligned by the feature order reordering unit,
In the feature shape refinement unit, a protrusion feature, a revolve feature, a sweep feature, and a loft feature are classified into a two-dimensional sketch-based feature, Based feature can be divided into a variable radius fillet, a pattern feature, a hole feature, and a shell feature,
Wherein the feature suppression unit simplifies the input CAD model by sequentially applying one sketch separated by the sketch inner loop elimination, the sketch recessed vertex removal, the sketch fillet, and the round elimination sequentially. Feature - based simplification system of CAD model.

The apparatus according to claim 1, wherein, in the feature importance calculating unit,
Wherein a change in volume before and after application of simplification is calculated in one sketch that is divided, and priority is assigned when the change in volume is small. A feature-based simplification system of a CAD model using unit feature simplification

A feature subdivision step of separately dividing a plurality of feature types in an input feature-based CAD model;
A feature importance calculating step of calculating the importance of each divided feature;
A feature rearranging step of rearranging the order of the feature features classified according to the feature importance calculating step,
And a feature suppression step of suppressing the subdivided feature having low importance,
In the feature subdivision step, a protrusion feature, a revolving feature, a sweep feature, and a loft feature are classified into a two-dimensional sketch-based feature, Based feature can be divided into a variable radius fillet, a pattern feature, a hole feature, and a shell feature,
Wherein the sketch inner loop elimination process, the sketch recess vertex removal process, the sketch fillet, and the round elimination process are sequentially performed in the separated feature sketch, and the input CAD model is gradually simplified. Feature-based Simplification Method of CAD Model Using Shape Simplification

The method of claim 3,
If both the sketch inner loop removal process, the sketch recessed vertex removal process, and the sketch fillet and round removal process can be performed in the subdivided feature shape, A Feature-based Simplification Method of CAD Model Using Simplified Unit Features