基于NURBS曲面曲率分析的钣金件自由特征识别技术

Feature Recognition for Freeform Sheet Metal Parts Using Curvature Analysis of NURBS

提出并实现了一种面向钣金件自由曲面模型的形状特征识别技术.算法由曲面区域分割、领域独立凸凹特征的搜寻和面向钣金成形的形状特征识别3个步骤构成.输入几何模型数据是基于IGES格式的CAD模型,其中曲面是以NURBS形式表示的裁剪曲面.利用NURBS符号运算分析曲面的曲率特性,并将其分割成各种曲率域.通过基于规则的方法,将符合特定几何及拓扑关系且具有高层工程意义的连续曲率域集合识别为对应的形状特征.最后,通过2个实例验证了该方法的可行性和有效性.

This paper presented an approach to recognizing geometric features from freeform surface models of sheet metal parts.It consists of three steps： region segmentation of surfaces,domain independent protrusion/depression detection and recognition of geometric features for sheet metal forming domain.The（input） geometry data is based on an IGES CAD model and the surface can be represented by trimmed NURBS surfaces.Symbolic computation is used to analyze surface curvature and segment them into curvature（regions）（CRs）.Then sets of connected CRs with particular geometry and topology which have high-level engineering meanings are recognized as features by a rule-based approach.Two case studies are presented to verify the feasibility of the developed method.