【作者】 徐建国；

【导师】 张友良；

【作者基本信息】 南京理工大学 ， 机械制造及其自动化， 2007， 博士

【摘要】 随着知识经济和信息技术的发展，网络化制造得到广泛研究和应用并逐渐取代传统制造模式成为新一代的先进制造模式。在网络化制造模式下，由于产品开发活动分布于不同企业的不同部门，企业只有得到数字化仿真工具，特别是数字化加工过程仿真工具的支持，才能真正实现产品的快速设计和开发。虚拟加工是实际加工过程在不消耗能源和资源的计算机虚拟环境中的本质映射。它一方面使设计人员可以根据仿真结果评价设计零件的可加工性，另一方面也使得工艺人员能够在实际加工前检验数控工艺和数控程序的正确性，从而有力地支持网络化制造的异地产品协同开发。因此，研究网络化制造系统中虚拟加工关键技术具有重要的理论意义和工程应用价值。本文首先从虚拟加工的特点入手，在对虚拟加工系统进行需求分析的基础上，提出一种由界面层、功能层和数据层三个层次组成的虚拟加工系统体系结构，讨论了系统实现所需的关键技术，为论文的研究确定了方向。虚拟加工环境模型是网络化制造系统数字模型的重要组成部分，是实现虚拟加工的基础。根据虚拟加工环境模型的功能需求分析，提出了由部件层、设备层和环境层组成的虚拟加工环境层次模型。部件模型由部件几何模型和部件物理属性仿真模型组成。部件几何模型又进一步分为显示几何模型和工程语义模型，它不依赖于具体商用CAD软件。设备模型由设备配置模型和设备行为控制模型组成，环境模型由环境配置模型和环境行为控制模型组成。此层次模型具有扩展性好、信息完备、支持重构等优点，为虚拟加工系统的实现提供了支持。网络化制造系统中数控设备的分布性和多样性要求数控程序解析器具有通用性。通过对数控程序格式的分析，提出一个通用数控程序解析器的框架结构及其处理流程。基于调用堆栈对子程序进行检错和解析处理，高效地实现了数控程序段位置的跳转、子程序调用次数的控制以及调用现场的恢复。提出了用于对解析器进行功能扩展的数控系统定制方法，使用户可以方便快捷地建立新数控系统的规则。基于正则表达式对数控程序进行语法分析，实现简单，效率高。设计了支持通用数控程序解析的规则数据库表结构。加工过程可视化仿真是虚拟加工的核心功能之一。提出了加工表面的细分方法和通用刀具廓形扫掠体表面方程的求解方法，在此基础上，提出了基于三角网格模型的优化仿真算法。为了提高虚拟加工可视化仿真的实时性，提出一个改进的区域划分算法，对三角面片区域判定、虚拟场景部件遍历及重绘区域判定三个方面的问题进行了深入探讨，并就区域粒度对算法性能的影响作了实验分析。碰撞检测是全面验证数控工艺和数控程序所必需的另一关键技术。提出了一个面向虚拟加工的混合碰撞检测算法。算法由两部分组成，其一为物体空间的包围盒检测算法，其二为图像空间的碰撞检测算法。采用扫掠和裁剪算法进行物体空间的粗判断，用以快速排除未发生碰撞的物体对。继而采用图像空间算法精确检测物体对之间的相交状况。首先判断图形硬件是否支持可见性查询；如果支持，选用基于可见性查询的算法进行碰撞检测；否则，选用基于深度-模板测试的算法进行检测；以此兼顾算法的适应性和效率。对算法的性能作了实验分析，实验结果表明此算法显著提高了碰撞检测的效率。基于网络化异地协同设计制造系统e-CWS，应用本文的研究成果，采用面向对象和组件化程序设计方法开发了一个虚拟加工原型系统VMS，并进行了虚拟加工可视化仿真的实例验证。更多还原

【Abstract】 With the development of knowledge economy and information technology, networkedmanufacturing is widely researched and applied. It is now becoming a new paradigm formanufacturing industry. Because product development activities are distributed innetworked manufacturing system (NMS), digital simulation tools, especially digitalmachining process simulation tools are required for rapid product development. Virtualmachining (VM) is the map of real machining in computer environment. On one hand, itassists designers to evaluate the machinability of a part based on simulation. On the otherhand, it can help process planner validate numerical control (NC) process and codes beforereal machining. Hence, the research of virtual machining key technologies in NMS is ofgreat importance in both theory and application.On the basis of the analysis of the characteristics and function requirements of virtualmachining system (VMS), a VMS architecture, which is composed of interface layer,function layer and data layer, is proposed. The key technologies for VMS are discussed andthus the research direction of the dissertation is determined.Virtual machining environment (VME) model is an important part of digital models inNMS, and it is also the basis of VMS. A hierarchical VME model is presented, which iscomposed of component layer, equipment layer and workshop layer. Component modelincludes a geometry model and a physics attribute simulation model. Component geometrymodel is made up of a display geometry model and an engineering semantic model, and itis independent of commercial CAD software. Equipment model consists of an equipmentconfiguration model and an equipment behavior control model. Environment modelincludes an environment configuration model and an environment behavior control model.The hierarchical VME model has the virtue of good expandability, full information andsupporting reconfiguration.Because the equipment in NMS is distributed and diverse, the NC code parser shouldbe all-purpose. Based on the analysis of NC code format, a general NC code processframework and a flow chart are proposed. The sub-program is processed on the basis ofcalling stack. This method can deal with the transfer of NC code location, the control ofNC sub-program calling number and the resume of calling conditions efficiently. The NCsystem customization method is designed to make the user set up the rules of a new NCsystem quickly and conveniently. The syntax is analyzed based on regular expression. Furthermore, the scheme of rule database is designed for general NC code processing.Visual machining process simulation is the core function of VM. Firstly, a workpiecesurface subdivision method and a method for solving swept volume surface of general toolare proposed. And then an optimized machining simulation algorithm based on triangularmesh model is put forward. For promoting the visual simulation speed of VM, an improvedregion partitioning algorithm is presented. The display surface is first divided into smallregions. Then the triangular facets are regrouped according to their covering regions.During machining simulation, since only the facets of modified regions need to be redrawn,each frame can be rendered in a short time. Three important aspects of the algorithm:triangular facet’s region judgment, virtual scene components traverse and redraw regionjudgment are discussed in detail. The tests are done to demonstrate how the regiongranularity can affect the performance of the algorithm.Collision detection is a key technology for fully validating NC process and code. Ahybrid collision detection algorithm for VM is presented. The algorithm is made up of twoparts. One is an object space detection algorithm, the other is an image space detectionalgorithm. The object space algorithm prunes the non interference object pairs rapidly. Andthe image space algorithm judges the interference state between objects precisely. Firstly,the algorithm judges whether the graphics display hardware supports the visibility query. Ifthe function is supported, the algorithm based on visibility query is used. Otherwise, thealgorithm based on depth-stencil test is used. The performance of the algorithm is testedand the results show that the algorithm can enhance the efficiency of collision detectiongreatly.In the end, a virtual machining prototype system, which is a module of the networkedcollaborative design and manufacturing system e-CWS, is developed by COM techniques.Some application instances are introduced to validate the technologies of the dissertation.更多还原