【作者】 李伟平；

【导师】 谷正气；

【作者基本信息】 湖南大学 ， 车辆工程， 2007， 博士

【摘要】 现代制造业尤其是汽车工业的全球化要求CAD技术朝着异构环境下的协同CAD方向发展。本文并在系统总结现有国内外最新理论成果的基础上，针对该领域中的若干关键技术进行了深入研究，内容主要包括以下几个方面：1．系统地阐述了基于异构的协同CAD系统的基本内涵、体系结构和相关的关键技术，提出利用集中式与复制式各自的优点，建立混合式协同CAD系统，并对异构系统之间基于特征的数据交换方法、数据表达和传输机制、以及消息的路由及处理机制等关键问题进行了研究。2．在分析基于特征的商业化CAD系统的基础上，提出基于隐式特征表达的增量式数据交换框架，依此建立了标准特征库，详细讨论了特征元素、特征结构、特征历史以及坐标系的表示方式。为满足车身设计的需要，在归纳前人研究成果基础上，提出了基于几何的曲面特征的表达方法。3．在特征参数化定义域直接引用B-Rep域中的拓扑实体是以往永久命名方法固有的缺陷。本文提出基于特征解决方案：为特征面建立统一的命名方法，并规定在建模过程中特征面的名字不变；建立拓扑实体与特征面之间的表达关系，在特征参数化定义过程中引用由特征面表达的拓扑面，解决基于特征的协同CAD中拓扑实体永久命名问题；给出提出参考面的概念，用于解决拓扑面、拓扑边分裂和多重交线等问题引起的引用模糊问题。在此基础上，详细讨论了拓扑面、拓扑边匹配的方法。4．在分析已有的复制式协同设计系统并发控制特点和不足的基础上，深入探讨了特征各种复杂的关系，给出了协同设计中并发冲突的定义；在研究CAD特征空间关系和依赖关系的基础上，提出以特征为并发控制的基本单元，设计了复制式结构下协同设计的并发控制模型。根据实际协同设计的需要，设计了与本地CAD系统低耦合的协同功能模块。5．在建立产品数据库方面，首先研究了EXPRESS模式到关系数据库模式的映射方法。重点研究了STEP定义的数据类型向关系数据库映射的规则，包括简单数据类型、命名数据类型、聚数据类型、构造数据类型映射方法，简单、复杂继承关系、引用关系的映射方法。然后，研究了STEP数据库访问接口SDAI的实现技术，针对导航式、存在-依赖式、混合式三种典型的STEP数据访问结构，以产品标识功能单元、物料清单功能单元、产品几何功能单元中的应用对象为例，提出相应的数据访问方法。最后，作为产品数据库的一个应用实例，提出以STEP AP214和AP224应用协议为信息交换和共享的“桥梁”，实现CAD／CAPP／CAM集成的思路，详细探讨了从AP214数据库提取特征信息的关键问题。在此基础上，利用VisualC++编程语言和STEP开发工具包ST-Developer进行了系统软件的开发。6．利用CAD软件的VRML接口实现了基于三角曲面模型的设计小组之间的协同观察。首先根据VRML文件给出初始三角曲面的构造方法；在解决多个曲面拼接过程中的顶点相容性问题后，给出了在保证曲面之间达到G~1连续的三角B-B曲面构造方法以及网格细分方法，保证能更加真实的反映原始CAD模型的形状。更多还原

【Abstract】 The globalization of modern manufacturing, especially in automobile industry calls for CAD technology focusing on collaborative CAD based on heterogeneous environment. Based on systemic summarizing production up to date, this dissertation deeply researches some key technology in the domain. Mainly content are:Basic meaning, architecture and correlative key technology of collaborative CAD system in Heterogeneous environment are discussed systemically. By utilizing the advantage of centralized and replicated system, composite collaborative CAD system is established. Furthermore, the key problem of CAD model exchange method between Heterogeneous CAD Systems based on feature, CAD model representation, transmission mechanism, and message route and treatment are researched in the dissertation.According to analysis of feature-based commercial CAD systems, framework of data exchange based on implicit and incremental feature is put forward and based on it, standard feature library is established. Furthermore, feature element, feature structure, feature history and feature coordinate are discussed in detail. To satisfied demand of car body design, geometry-based surface representation is put forward according to the method of previous investigator.Directly referring to topological entity of B-Rep domain in feature’s parametric definition domain is inherent limitation of previous persistent naming topological entity method. A feature-based solution for topological entity naming is proposed in this paper. Firstly, uniform naming method for feature face is established and its name is remaining invariable during the modeling procedure. Secondly, the expression between topological entity and feature face is established and topological entity expressed by feature face is referred during the course of feature’s parametric definition, and as a result, solve the problem of persistent naming topological entity for feature-based collaborative CAD. Thirdly, the concept of reference face is proposed and utilized to solve ambiguous referring problem, which arose from topological face splitting, topological edge splitting and multiply intersection edges. Based on above researches, topological face and topological edge matching method is discussed in detail. By analyzing the characteristic and deficiency of previous concurrency control of replicated collaborative CAD system and deeply researching complicated relations of features, the definition of concurrent conflict is presented in collaborative design system. The method of concurrency control taking feature as unit is proposed according to spatial and reliant relation between CAD features and concurrency control mode which is fit for replicated cooperative design system is designed. According to Practice requirement, low-coupling with local CAD system function module is also designed.Take account of product database system, the mappingEXPRESS-definitions into relational database system structures is researched firstly in this dissertation. The rules for mapping the data type defined in STEP standard to relational database system, including primitive type, naming type, aggregation type, structural type, and the relations between different types such as simple or complicated inheritance and reference. Secondly, aim at three representative access mode Navigational, Existence-dependent and mixed mode, take Part Identification, Bill of Materials and Part Geometry as example, corresponding data access method are presented. Lastly, as an application example of product database, a bridge for exchange information between AP214 and AP224 is designed to implement CAD/CAE/CAM integration. The procedure for extracting feature information form AP214 product database is discussed in detail. Based on the research mentioned above, system prototype is developed utilizing Visual C++ programming language and ST-Developer which is STEP development tool.Collaborative view triangular-surface model among different design teams is realized by using interface of CAD software. Firstly, original triangular surface is obtained form VRML file. Secondly, in order to capable of view original CAD model more approximately, method of constructing G~1 continuous triangular B-B surface and mesh subdivision after the vertex consistency problem is solved.更多还原