三维CAPP中零件特征提取及基于遗传算法的工艺排序研究.pdf

华中科技大学
硕士学位论文
三维CAPP中零件特征提取及基于遗传算法的工艺排序研究
姓名:徐正
申请学位级别:硕士
专业:机械电子工程
指导教师:张国军
20050430
摘要
工艺设计是联系产品设计与制造之间的桥梁,基于三维的 CAPP 是实现工艺设计
定量化与智能化的重要手段,对于提高产品研发水平具有重要意义。本文结合作者参
加的八六三项目,对三维环境下的 CAPP 系统研制开发中的两个关键技术:三维零件
特征提取和基于遗传算法的工艺排序进行了研究和探讨。
建立了三维环境下 CAPP(3D-CAPP)系统的框架体系结构,研究了 3D-CAPP
系统的运行流程,分析并比较了三维 CAD/CAPP 系统的几种集成方法,包括基于中
间文件、基于 PDM 以及直接集成方法等。
在研究 STEP 标准、STEP 文件结构和 EXPRESS 建模语言的基础上,给出了基于
STEP 和 EXPRESS 的工艺描述方法,通过 STEP 文件信息读取与分析,实现了零件特
征识别与提取。
以一个箱体类零件为例,描述了三维环境下基于遗传算法的工艺排序问题,建立
了基于遗传算法的工艺排序数学模型,研究了其基本过程,包括工序编码和解码、适
应度函数确定以及交叉和变异等。给出了运用上述方法进行工艺排序的实例。
开发了三维环境下 CAPP 系统的原型系统,介绍了系统的主要功能。
最后对全文进行了总结与展望。

关键词:三维 CAPP 特征提取遗传算法工艺排序







I
Abstract
Process planning is the bridge to link product design and manufacture. The CAPP
system in 3D environment (3D-CAPP) is an important means to realize the quantitative and
intelligent process planning. It has significant meaning to improve product research and
development. According to the project supported by the 863 Program, two important
technologies about 3D-CAPP, including part feature obtaining and process sequencing
based on ic algorithm, are studied.
First, the framework of 3D-CAPP system is built up and the working flow of
3D-CAPP system is discussed. Several methods of CAD/CAPP integration, including
neutral file based method, PDM based method, direct integration method, pared.
Secondly, the process describing method is given based on researches of the STEP
standard, STEP files structure and EXPRESS modeling language. Via reading and
analyzing the information in STEP files, the part feature identification and obtaining is
realized.
Then, taking a box part as an example, a process sequencing question using ic
algorithm (GA) is described. The mathematics model of positor using GA is
built up, and the basic working process, including coding and decoding the working
procedure, fitness function, crossover and mutation, is put forward. Then