零件工艺知识建模及其相似性度量方法研究

Knowledge-based Modeling and Similarity Measurement for Process Planning of Parts

针对计算机辅助工艺规划系统中零件工艺设计知识重用的问题,提出一种适用于三维工艺知识重用的知识建模及相似性度量方法。通过分析零件工艺知识中三维几何特征的演变规律,提出加工元和加工元序列的概念。基于因素空间理论,分析工艺知识的信息本质,定义了工艺知识元并给出了知识元的因素集,以此构造出工艺知识空间表达模型。根据因素状态值的数据类型,将高维的知识元因素空间投影到三维度量空间,并给出三个维度各自的相似性度量函数。利用欧氏距离公式得出知识元的空间距离,归一化后得到知识元的相似性。

To solve the reuse of parts process knowledge in the Computer Aided Process Planning( CAPP) system,the knowledge based modeling and similarity measurement method for the reuse of Three-Dimensional( 3D) process knowledge is proposed. According to analyze the evolvement law of 3D geometric feature in parts process knowledge,we introduce the concept of machining cell and its sequence consequently. Based on the factor space theory,the information essence of process knowledge is analyzed,the concept of knowledge element is defined and its factor set is subsequently provided. According to the above-mentioned,we contruct the space expression model of process knowledge. According to the data type of the factor' s status value,we contruct the measurement space which is the projection of the high-dimensional factor space of knowledge element onto 3D space and present the similarity measurment function of each dimension. The space distance among knowledge elements using Euclidean distance is calculated and then the similarity of knowledge element is gotten. The effectiveness of the method has been confirmed in the prototype system for knowledge reuse.