【作者】 陈蔚芳；

【导师】 姜澄宇； 王宁生；

【作者基本信息】 南京航空航天大学 ， 机械制造及其自动化， 2007， 博士

【摘要】 夹具是一种重要的工艺装备,直接影响产品的质量和研制周期。在当今航空制造业中,大多是单件小批和定制生产模式,在这种模式下,夹具设计与制造的工作量相当大,由于夹具准备不及时导致产品延迟交付和由于装夹不当导致工件变形的现象时有发生,造成巨大的经济损失,因此夹具的快速优化设计成为迫切需要解决的问题。本文在对夹具敏捷设计系统结构和流程分析的基础上,从并行设计、资源柔性管理、结构变异、夹具优化、快速装配等方面深入研究了夹具敏捷设计问题,取得了以下主要成果:建立了基于产品数据管理(product data management, PDM)的夹具并行设计集成框架。分析了基于特征的工件集成模型,重点研究了装夹特征模型、装夹特征提取流程、约束特征识别方法和特征映射方法。采用XML描述了工件集成模型信息,实现了异构环境的信息集成。详细讨论了夹具结构管理、配置管理、夹具设计过程管理功能,并实现了夹具敏捷设计与PDM的集成,使PDM强大的数据管理功能得到了延伸。为了实现夹具设计资源的柔性管理和有效共享,建立了基于夹具结构树和特征网的夹具模型,以及支持夹具设计全过程的设计资源模型。采用事物特性表对元组件、夹具等关键设计资源特性进行了描述,对元件、组件、夹具等关键设计资源的自动几何建模方法进行了研究,在元件建模基础上实现了组件和夹具级的尺寸驱动和自动几何建模。将实例推理方法应用于夹具设计全过程,在方案设计、优化设计、详细设计、装配设计等阶段实现了设计重用。重点分析了分层检索机制、推理机制、修改机制、实例存储策略。针对夹具实例修改难题,研究了夹具模板构建、基于模板的变异分类、变异知识获取与表达、变异流程等关键问题,实现了元组件规格和位置的变异。夹具优化设计是精密薄壁件夹具敏捷设计的关键,为此,建立了以最小工件变形和最均匀变形度为目标函数的夹具布局和夹紧力多目标同步优化模型,基于遗传算法和有限元法实现了夹具多目标同步优化设计过程。在建立有限元模型时,综合考虑了接触力、摩擦力、切削力、夹紧力、切屑的影响,使模型更为合理、更贴近实际。提出了基于优化布局,采用变夹紧力进一步控制工件变形的方法,分析了基于有限元法和遗传算法的动态夹紧力求解模型和求解方法。通过实例进行了验证,夹具布局和夹紧力多目标优化和变夹紧力优化可以减小工件变形。为了减少模型的复杂性,将装配模型分成了节点层和特征层,在节点层引入了有效路径;在特征层引入了有效特征面和有效作用距离,使装配模型更趋合理。研究了基于有效路径和装配特征面的装配策略,实现了夹具的快速装配。最后,完成了基于PDM和SolidWorks平台的夹具敏捷设计原型系统的开发,有效集成了SolidWorks、MATLAB、ANSYS等软件系统,集成了设计、分析、管理等功能模块。原型系统的部分模块已取得了良好的应用效果。更多还原

【Abstract】 A fixture is a device which directly affects product quality and lead-time. Many firms are running a single piece, small path or customized production in current aeronautical industry. In such a production mode, a mass of work should be done for fixture design and manufacture. It happens once in a while to delay production caused by not preparing fixture in time and also the workpiece deformation caused by a poor fixture setup. This leads to a huge economic loss. Therefore, the method of rapid fixture optimization design is urgently required. Based on the analysis of structure and process of an agile fixture design system, some researches have been done deeply in agile fixture design. They are concurrency of design, flexible resource management, variation of design, fixture optimization, rapid fixture assembly and so on. The main works in this paper are concluded as follows:A concurrent integration structure of an agile fixture design is created based on product data management (PDM). The feature-based workpiece integration model is developed. Fixturing feature model, feature information pick-up process, feature identifying and feature mapping method are analyzed. In order to meet the demand of information integration in different platforms, XML is used to describe the workpiece integration information. In order to extend the data management function of PDM, some integration functions, such as fixture structure management, configuration management and process management are analyzed and developed.Aiming at the flexible management and effective sharing of fixture design resources, a fixture model is created based on fixture structure tree and feature net and design recourse model, which supports the entire process of fixture design is established. SML (tabular layouts of article characteristics) are used to describe characteristics of the key design resources, such as fixture element, component and fixture. The automatic modeling method of part, component and fixture are studied in detail. Based on fixture element modeling, automatic driving and automatic geometry modeling for fixture component and fixture are accomplished.The issue of using case-based reasoning (CBR) in the entire process of fixture design is proposed. The strategy of reusing design is applied in the different stage of design, such as scheme design, optimization design, detail design, assembly design and other stage. Hierarchical index rule, reasoning rule, modification rule and instance storage strategy are analyzed. In order to solve the difficulty of instance modification, key points such as fixture template constructing, variation classification based on the template, expression of variation knowledge, and variation flow are studied. As a result, the variations of component specification and component position are realized.Fixture optimization design is the main point of agile fixture design for high-precision thin-walled workpiece. The optimizing model of fixture layout and clamping forces simultaneously is developed with objective of reducing machining deformation and increasing the distributing uniformity of deformation. The fixture multi-objective synchronization optimization design process is realized based on genetic algorithm and finite element method. When establishing finite element model, the influences of the contact force, friction force, cutting force, clamping force, and scraps, are all taken into account to make the model more reasonable and more close to reality. A method using dynamic clamping forces on the basis of optimized fixture layout, to reduce workpiece deformation, is presented. The solution model and method of dynamic clamping force based on finite element method and genetic algorithm are studied. An example is given to illustrate that the fixture layout and clamping force multi-objective optimization and alterable clamping force optimization can reduce workpiece deformation.In order to reduce the model complexity, the idea of dividing assembly model into node layer and feature layer is proposed. The effective path is introduced into node layer while effective feature face and effective effect-distance are introduced into feature layer, which make the assembly model more rational. This paper also researches on assembly strategy based on effective path and assembly feature face and implements fixture assembly rapidly.Finally, an agile fixture design prototype system is developed based on GS-PDM and SolidWorks platform. Software packages such as SolidWorks, MATLAB and ANSYS are effectively integrated. The system integrates all function modules including design module, analysis module, management module and so on. Some modules of this prototype system have applied well.更多还原