【作者】 宋小波；

【导师】 赵韩；

【作者基本信息】 合肥工业大学 ， 机械制造及其自动化， 2009， 博士

【摘要】 计算机网络技术、网格计算、并行工程技术以及CAD/CAM相关技术的发展,改变了产品开发模式,促进了网络化产品设计的需求与应用。论文系统地研究了复制式协同CAD基础平台的相关理论与实现技术,为实现产品的实时协同开发提供了一种解决方案。论文从课题的研究背景出发,对协同CAD基础平台的关键技术——协同数据交换、并发控制机制、协同数据安全以及迟加入机制的概念、特点以及国内外研究现状进行了归纳和总结,指出了存在的主要问题和不足,并预测了其发展趋势,为全文的研究奠定了基础。论文在研究协同实时造型特点的基础上,构建了复制式协同CAD基础平台的网络拓扑及其功能框架,并为支持网络协同设计,对CAD平台、网络数据通讯以及多媒体交流等构成的支撑环境进行了特殊处理与优化,为如何构造协同CAD系统提供了理论支持和依据。协同数据交换用于保证整个协同系统的工作效率和用户体验。论文在深入研究复制式协同CAD环境下数据交换特点的基础上,提出了基于隐式特征表达的协同数据交换方法。该方法不需要交换模型的几何拓扑信息,而只需交换参数化信息,几何拓扑模型则由系统调用本地几何建模引擎重构,并通过利用面向对象的隐式特征消息类封装、网络序列化传输技术、语义特征重构技术以及基于面向对象的动态八叉树几何匹配技术,实现了网络实时协同造型。实践证明,该方法能极大降低网络数据传输量,提高网络造型的实时性。并发控制机制用于约束各协同用户的操作和规范设计时序。论文在深入研究CAD特征之间的复杂关系(如依赖关系、空间关系等)对并发操作冲突影响的基础上,提出了复制式协同CAD环境下的分层分布式并发控制模型。该模型以特征为基本的并发控制单元,设定了并发操作冲突、并发逻辑冲突、并发依赖冲突以及并发意图冲突的四层递进式检测规则,并运用分布式互斥算法,构建了系统自动协调、冲突双方协商以及第三方仲裁的分层冲突协调机制,实现了对并发操作的有效控制,并用实例验证了该算法的可行性与有效性。访问控制机制用于保证协同设计数据的机密性和完整性。论文在深入研究CAD模型层次结构和自主角色委托的基础上,提出了复制式协同CAD环境下多粒度动态安全访问控制模型。该模型将访问权限进行多粒度划分和量化处理,简化了权限集的计算,借鉴了工作流中的权限依赖关系和状态迁移概念,实现了权限的动态激活及细粒度调整,并利用基于信任度的委托属性表达式,实现了受托者资格筛选,最后通过对委托限制进行分类和组合,引入了委托条件及受控使用概念,实现了委托权限的条件委托及约束使用。实践证明,该模型可以对协同数据访问进行有效地控制,符合设计任务间的分工性、依赖性和交互性的特点。迟加入机制用于保证迟加入进程与当前设计进程的同步性。论文在深入研究了加入机理的基础上,提出了复制式协同CAD环境下带容错机制的三多播组结构分布式“迟加入”算法,并详细探讨了算法实现的各个关键问题。实例分析表明该算法能有效降低初始化延迟、网络负荷和应用程序负担。为了实现产品的网络协同设计,作者开发了复制式协同CAD原型系统。该系统紧密结合网络协同的思想,把实时协同设计作为其实现目标,实现了CAD技术和网络技术的无缝集成。更多还原

【Abstract】 The development of computer network, grid computing, concurrent engineering and CAD/CAM technologies not only changes dramatically the model of production process, but also accelerates the demand and application of internet product design. This paper systematically presents theories and technologies related to the basic platform and propose a solution to the real-time designing of product.This dissertation starts with the background of the research about Collaborative CAD, and presents in details about the key technologies about the fundamental platform—concepts ,futures and the current situation around the world about data exchange、concurrency control、access control and late join mechanism. This is also the basis of the dissertation.Based on the research of real-time modeling, this dissertation also constructs the replicated Collaborative CAD network topology and its functional frame. In order to support Collaborative design, we did some special operations and optimizations about CAD platform, supporting environment of Data communication and multimedia communication. This research work provides theory support and evidence for how to build a Collaborative CAD System.Data exchanging is used to ensure the efficiency and user experience of the whole collaborative system. An implicit feature representation data exchange model is proposed based on a deep research about the virtues of data exchanging for replicated collaborative CAD system. In essence, instead of exchanging geometry and topology information, only parametric information of features is exchanged, and geometry and topology information are left to evaluate by CAD system internal environment. To accommodate Collaborative real-time modeling, object-oriented serializable class message encapsulation、semantic feature re-construction and geometric matching based on dynamic octree technology are used to make the internet transmit more efficient, and implicit model exchange based on features is implemented. This method is proved to be efficiency on improving the performance of Internet and enhancing the quality in real-time.Concurrency control is used to constrain users’operations and rule the time schedule of designing. A multi-level distributed concurrency control model is proposed for replicated collaborative CAD system based on understanding the effect of the complicated relationships among CAD features (e.g. dependent relationship, geometrical relationship) to the confliction of collaborative operations. Using feature as its basic control unit, this concurrency control mechanism settles four progressive confliction detect rules, including collaborative operations rules, collaborative logic rules, collaborative dependence rules and collaborative concept rules. It also constructs a self-compatible, conflict-meditation and third-lateral-judge multi-layer confliction mediation mechanism based on the distributed mutual exclusion algorithm, and the multi-level distributed concurrency control is implemented. This method is proved to be efficiency and feasibility on controlling collaborative operations.Access control is used to ensure the confidentiality and integrity of the collaborative design data. A multi-grained and dynamic security access control (MGDAC) model is proposed based on understanding about the characteristics of the CAD model hierarchy and role-based delegation for replicated collaborative CAD system. A multi-grained quantified privilege model is developed to simplify the process of permission assignment and calculation for enriching the expression ability and helping to realize fine-grained access control. The dependent relation of permission and the permission state migration are brought into MGDAC for dynamic authorization management based on the basic theory of workflow. The delegation attribute expression and delegation trustworthiness are brought into MGDAC for delegatee’s qualification filtrating. Three types of delegation constraints are further studied and analyzed, including temporal, globalization and obligation. Using these constraints, delegation condition and constrained usage is described. Based on the practice, MGDAC model is more efficient to control collaborative operations. It meets the characters of design tasks, i.e. separate working ability, dependency and interactivity.Late join mechanism is used to keep the latecomers consistent with current working process. A distributed late join algorithm with fault-tolerance based on three multicast group (T-MDLJ) is proposed for replicated collaborative CAD system. The latecomers joining mechanism has been analyzed and key issues of late join algorithms are discussed in detail. The simulation test shows that the T-MDLJ algorithm reduces the initialization delay, network and application load efficiently. To the problem of digital support for internet-based collaborative design, Prototype system of Replicated Collaborative CAD System is designed, and CAD is implemented in network.更多还原