CN101097569A

CN101097569A - Part feature information modelling approach

Info

Publication number: CN101097569A
Application number: CNA2006100180391A
Authority: CN
Inventors: 张琳娜; 赵凤霞
Original assignee: Zhengzhou University
Current assignee: Zhengzhou University
Priority date: 2006-06-29
Filing date: 2006-06-29
Publication date: 2008-01-02

Abstract

The invention relates to a kind of modeling method for part characteristics. The invention can classify the shape characteristics based on constant class, and the intrinsic properties of constant class are as the parameters of parametric equation to realize digital expression; the direction relationships between shape characteristics adopt direction properties to realize digital expression; the accuracy properties is as the additional properties of shape properties, and the accuracy properties and shape properties are integrated by geometry link; and the information model of part is stored in database, and the CAX system can realize the integration of CAX by sharing database.

Description

A kind of part feature information modelling approach

Affiliated technical field

The invention belongs to the manufacturing informatization field, the modeling that is used for CAX integrated system Product Feature Information is with shared.Be particularly related to a kind of characteristic information modeling and storage means.

Background technology

At present, the feature modelling technology is one of effective ways that solve the CAD/CAPP/CAM integrated technology.Planform feature and accuracy characteristic are two chief components of parts information model.The planform feature description of part have the geometric configuration and the function information thereof of certain engineering significance, accuracy characteristic has then been described the permission variation or the error of geometric configuration and size, is non-geological information.The representation model of precision information is divided into based on CSG, based on B-Rep and several based on CSG/B-Rep mixture model etc. by the relation of itself and planform.Wherein, can only be based on the part feature information model of B-Rep at size and position of related features, and be only limited to and handle plane, the face of cylinder, circular conical surface and sphere.Moulding system based on CSG is still at the experimental stage at present, it is very limited to describe tolerance, also be not confirmed for whether being convenient to TOLERANCE ANALYSIS, simultaneously because this method is to realize in the system based on CSG, complex figure is obtained by intersecting and merging, difference by simple graph, so when same original pixel is in diverse location, can only give an identical tolerance value, different if desired tolerance values must re-construct the CSG tree.Express precision informations such as tolerance based on the CSG/B-rep mixture model, the two advantage of integrated application CSG, B-rep.The tolerance module is connected to the top layer of mixed structure, and the user can generate tolerance and other technical information in the process that body is created, but this method is complicated, is also really realized at present.In recent years, product model exchanges data (STEP) standard is devoted to complete, unambiguity ground expression tolerance under the prerequisite that adapts with the ISO1101 standard, and adapts to the needs of product data model exchange.What but this model used when definition position and direction in tolerance is approach vector, for actual entities, and how additional not clearly explanation of coordinate system on part.

Summary of the invention

The objective of the invention is to propose a kind of part feature information modelling approach based on invariance class for realizing the information integration of CAX.

Technical thought of the present invention is that with the adeditive attribute of accuracy characteristic as the planform feature, how much chained lists integrate accuracy characteristic and planform feature by reference, set up the part feature information model.Based on invariance class the planform feature is sorted out and to be divided into seven types in complex, prism, solid of revolution, conveyor screw, right cylinder, plane and ball, every kind of invariance class is expressed as the parameter realization digitizing of its parametrization equation with essential characteristic, and the position relation between the shape facility adopts orientative feature realization digitizing to express; The information model of generation part is stored in the database, and the CAX system realizes the information integration of CAX by the sharing feature database.

The invention has the beneficial effects as follows, solved the integration mechanism of further feature in precision information and the part feature model, and adopt sharing feature database storing part feature information, guaranteed the Rational flow of part feature information and shared each other, for the information integration of CAX realizes providing new approaches.

Description of drawings

Fig. 1 is part feature information model interaction figure of the present invention.

Fig. 2 is the planform tagsort figure based on invariance class of the present invention.

Embodiment

In the part feature information model, referring to Fig. 1, primary attribute is mainly used in the main attribute of description scheme shape facility, comprises tag number, feature name, heat treatment requirements etc.Accuracy characteristics such as size and tolerance, form and position tolerance, surfaceness connect with doubly linked list.The attributes relevant such as invariance class, size and tolerance, form and position tolerance, surfaceness with the planform feature, respectively with the node of the corresponding geometric element of pointed, size, precision and benchmark, simultaneously in the data structure of geometric element, feature, precision and benchmark also with its pairing geometry node of quoting of pointed.Adopt this geometric ways of quoting, on the one hand, quoted geometric expression geometric element that precision acted on and feature on the other hand, quoted how much also with a kind of attribute of precision as geometric element, expressed the precision that acts on the different geometric elements.Input along with precision information, system dynamics ground is set up and chained list is quoted in maintenance how much, thereby set up getting in touch between feature, geometry and the precision, geometry and non-geometric attribute information integration are got up, form a complete product information model that can satisfy integrated needs.

Based on invariance class shape facility is sorted out division, referring to Fig. 2.The position key element is the orientation of planform feature and the key element of direction, and it can be a point (PT), straight line (SL), a plane (PL) or a helicoid; For example the position key element of cylinder is an axis, and the position key element of circular cone is summit and axis.Essential characteristic is the parameter of planform characteristic parameter equation, as the radius of circular arc, and the diameter of cylinder, the drift angle of circular cone, the angle of two straight lines etc.Relation between two planform features is expressed with orientative feature, is the direction between two key elements of definition and the feature in orientation.For example, the mutual alignment between circular cone and the plane by circular cone position key element (axis and summit) and the position key element (plane itself) on plane between point-interplanar and line provide to the distance between face.The related side on a cylinder and plane line-face angle between the position key element (plane itself) on position key element (axis) by cylinder and plane provides.Like this, based on invariance class the planform feature is sorted out division after, can realize that the digitizing of part feature information model is described.

Adopt the database stores characteristic information, geological information relevant in the characteristic information points to the geological information storehouse with the pointer mode.The characteristic information that the CAX systematic unity selects for use each subsystem of sharing feature database definition, operation and management to share.

Claims

1, a kind of part feature information modelling approach.Planform feature and accuracy characteristic are two chief components of parts information model.It is characterized in that, set up the integrated mechanism of further feature in precision information and the part feature model; Its feature also is, based on invariance class the planform feature is sorted out division, realizes that the digitizing of part feature information model is described; Its feature also is, adopts the sharing feature database to realize the information integration of CAX system.

2, method according to claim 1 is characterized in that, accuracy characteristic is as the adeditive attribute of planform feature, and how much chained lists integrate accuracy characteristic and planform feature by reference, set up the part feature information model.

3, method according to claim 1, it is characterized in that, based on the carrier of invariance class with parts information---the planform feature is sorted out and is divided into seven types in complex, prism, solid of revolution, conveyor screw, right cylinder, plane and ball, adopts essential characteristic and orientative feature to realize describing based on the digitizing of the part feature information model of invariance class.

4, method according to claim 1 is characterized in that, institute is produced the part feature information model be stored in the database, and the CAX system realizes the information integration of CAX by the sharing feature database.