【作者】 张志伟；

【导师】 王太勇；

【作者基本信息】 天津大学 ， 机械制造及其自动化， 2009， 博士

【摘要】 随着工业领域信息化进程的加快,数控技术得到了广泛的应用,新的数控系统数据接口规范STEP-NC是STEP在制造领域的延伸,它与STEP具有相同的几何信息描述的形式,解决了传统的数控编程数据接口ISO 6983局限性的问题。本文以交换文件为对象,对产品信息的特征提取与建模问题进行了研究。针对在建模中出现的信息量大和处理问题繁杂等难题,本文提出了由低端元素到高端元素的信息提取模式(L-H模式),并将该模式应用于STEP-NC文件的信息提取过程之中。使用此模式可减少最终数据模型中的信息冗余,节省信息存储空间,便于相关元素列表的生成,且有利于对产品信息的统一获取与管理,使产品模型易于维护。交换文件中存在着对产品边界的描述信息,为使这些信息得到充分利用,本文在对相关信息表述方式进行深入分析的基础上,提出了基于边界信息的特征提取方法,并将其用于STEP-NC文件显示操作之中。该方法充分利用产品模型中的边界相关信息,借助于对相关元素列表的遍历实现了对特征的提取。应用该方法可以节省产品模型中所有边线凹凸性进行判定的计算量,简化产品特征模型的构造过程。如何有效、快捷地完成不同产品模型之间的信息交换,是实现产品信息管理的重要一环。本文面向特征及其相关元素,提出了特征块的概念,并将特征块对象应用于不同产品模型之间的信息交换之中。以特征为基本单位对各个产品模型中与之相关的信息进行分类与整合,并存储于特征块数据结构中。将特征块作为连接工具构建了各产品模型间的互动信息流动平台,实现了基于特征参数的模型修改与更新。本文通过对交换文件的表示方法、元素定义的映射等关键技术的分析,论述了产品几何信息模型、产品信息模型、产品特征模型、产品可视化模型和产品公差模型的具体定义形式和实现的方法。创建了简洁适用的表征产品特征的模型体系及面向产品的数据管理系统。并以法兰等产品为例,验证了各模型及模型之间信息流动的可行性。更多还原

【Abstract】 With the rapid development of informatization in industrial domain, NC technology is used extensively. As a new standard interface in NC systems, STEP-NC is an extension of STEP in machining. It has the same format in description of geometry information and solves limitations of ISO 6983. Aiming at exchange file, this dissertation focuses on feature recognition and model establishment from part information.The down-top pattern (L-H pattern) for product information acquisition is proposed to deal with problems such as vast quantity and complexity of information in modeling, and is used in the extraction process of STEP-NC files. With this pattern, product data models have been established with reducing information redundancy and much storage space has been saved. Furthermore, relative elements lists have been conveniently realized and reasonable product information could be acquired and managed conformably from the use of this pattern, so that expedient model maintenance is supported.In order to fulfill the boundary information in exchange file, a feature extracting method, which based on bounding information of geometry elements, is proposed and is used in STEP-NC file for product visualization, through the analysis of expression of product model in exchange file. With the traversing of relative elements lists, product features are extracted by the extracting method, which takes advantage of bounding information in product model. With this method, calculation about the concavity and convexity of curves is not needed and the construct process of product feature model can be simplified.It is an important component in realizing management of part information to accomplish information flow among different part modules effectively and quickly. The definition of feature block is proposed on feature and its relative elements. And the object of feature block is used in information exchange among different product models. Take features as principal units, related information in product models is assorted, arranged and stored in data structure of feature block. With the feature block as link, a platform for information flow among product models is established and the feature-based amendment and refresh of product model can be achieved.Through the analysis of critical technologies such as presentation method in exchange file and mapping method of element definition, the definition and implication method of the product geometry information model, the product feature model, the product visualization model and the product tolerance model are discussed. A prototype system for product features and a product information management system are achieved. With a flange and other files as examples, the feasibility of every product models and the information flow among those models is validated.更多还原