【作者】 张丹；

【导师】 左敦稳；

【作者基本信息】 南京航空航天大学 ， 机械制造及其自动化， 2010， 博士

【摘要】 航天产品结构复杂、零部件繁多,传统装配工艺设计需要建立大量物理模型以进行模装试验才能确定设计,并且纸质装配工艺文件难以清晰描述复杂装配工艺,使得产品装配周期长、成本高,无法满足企业敏捷制造的要求。虚拟装配技术为上述问题的解决提供了新的研究思路,本课题以企业应用为背景,展开面向航天产品敏捷总体装配的虚拟装配工艺设计及其应用基础研究,该项研究对于实现航天产品装配工艺的快速和低成本设计、提高企业的紧急动员生产能力,具有重要的现实意义和应用价值。论文完成的主要工作及取得的成果如下:1.设计了桌面式虚拟装配工艺设计系统的总体框架。首先分析了虚拟装配工艺设计系统的功能需求,在此基础上阐明了桌面式虚拟装配工艺设计系统的研究内容和特点,将系统结构分为交互层、功能层、支持层和数据层,建立了完整的系统层次体系结构,给出了系统的工作流程:数据预处理阶段、装配工艺设计阶段和工艺文件输出应用阶段。2.研究了面向航天产品的虚拟装配建模技术。分析了航天产品虚拟装配模型的需求,对装配场景模型进行了分类,将装配场景模型分为刚性零件模型、电缆零件模型和其他模型,并分别给出了实体表达及信息描述方法,提出了包括刚性零件和电缆零件的刚柔混合装配层次关联模型,并对模型的信息描述和数据结构表达进行了详述。分析了装配模型在虚拟环境中的建立内容和流程,提出了零件模型信息的转换与存储方法,最后给出了刚柔混合装配层次关联模型的建立流程。3.研究了虚拟装配的交互辅助技术。提出了虚拟环境下具有交互辅助功能的装配流程,提出了基于约束元素包围盒的装配意图捕捉算法及效率评估方法,根据约束元素的特征参数和配合类型,提出了基于位姿变换元素分解的约束精确定位求解算法,将位姿变换分解为点到线上、点到面上和直线平行3种位姿变换情况。并通过对零件自由度的求解和目标约束方向上的运动分量映射,提出了基于约束元素投影的装配运动导航方法,上述方法可有效减少约束的误识别和漏识别现象,并保证虚拟环境下零件的装配运动精度。研究了装配约束关系的动态解除方法和紧固件装配工具的操作及可达空间验证方法。研究了基于质点弹簧系统的电缆零件装配方法及仿真流程,分析了电缆束质点弹簧系统的动力学特性,使用Verlet积分法对质点弹簧动力学微分方程进行求解,并提出了弹簧动态变形约束算法和电缆束的网格变形更新算法来增强仿真的真实性。4.研究了面向虚拟装配工艺的顺序规划和路径规划方法。基于粒子群遗传算法,结合虚拟装配系统良好的交互性,提出一种人机协同的航天产品装配顺序优化方法。使用优先约束关联矩阵来描述零件间的优先约束关系和关联关系,并研究了粒子群遗传算法的基因组、染色体以及粒子的编码表达方法。综合考虑装配连续性、装配资源的变动和仪器设备的影响,提出了有工程意义的适应度函数的表达式,根据优先约束关联模型生成随机的可行初始装配序列,并利用粒子群算法重构遗传算法的交叉算子对装配顺序进行优化。用一个实例表明该方法较常规遗传算法有较好的收敛性和稳定性。研究了面向虚拟装配工艺的装配路径生成方法。提出了装配物料清单和装配动画的生成以及工艺文件数据的提取策略。5.开发并实现了桌面式虚拟装配工艺设计原型系统。原型系统由装配建模、虚拟装配仿真、装配顺序规划、装配工艺文档设计与示教四个模块组成,详述了各模块划分及模块间的数据流向,并介绍了原型系统的开发架构和开发环境。以航天产品某部件的装配模型为例,对其在原型系统中的虚拟装配工艺规划工作流程进行了详细说明,通过介绍各个模块的主要功能界面,验证了各个模块的功能,得到了初步应用。更多还原

【Abstract】 Traditional assembly process planning for aerospace products requires plenty of physical mock-up trials to verify designs because of their complicated structures and large number of components. Meanwhile papery process files are difficult to express complex assembly process clearly. As is stated above, the problem leads to long assembly cycle and high cost, so traditional assembly process planning can’t satisfy the agile manufacturing requirement of enterprise. Virtual assembly technology is a new approach to solve the problem. This research task has a background of enterprise application to research the virtual assembly process planning technology and its application for aerospace products, which has important practical significance and values for realizing the rapid assembly process planning and improving enterprise’s emergency mobilization productive capacity.The main work is illustrated in the following aspects:First, the desktop virtual assembly process planning system is designed. Virtual assembly systems are classified and functional requirements of virtual assembly process planning system are analyzed. Based on them the research contents and characters of the system are expressed. The system’s hierarchical architecture is established which is divided into four layers: interaction layer, function layer, core services layer and database layer. And the workflow includes data preprocessing phase, assembly process planning phase and process files output phase.Second, the virtual assembly modeling technology for aerospace products is studied. The demands of aerospace products assembly models are analyzed. The model representation and information description are researched according to the classification of models in the virtual assembly scene, which consists of rigid parts, cable harness parts and other parts. The dendritic liaison model of mixed assembly of rigid and flexible parts is introduced based on the hierarchical model and graph model. The content and workflow of assembly modeling in the virtual environment are proposed. And methods of model data transformation and storage are presented.Third, the interactive aid technology for virtual assembly manipulation is researched. The flow of virtual assembly manipulation with interaction aid is presented. A novel assembly intention capturing algorithm based on constraint element bounding box and its efficiency evaluation is proposed. And the precise positioning solving algorithm of constraint based on pose transform of elements decomposition is presented, in which pose transform is classified into three cases as follows: placing a point onto a line, placing a point onto a plane and paralleling a line to a line. Parts assembly motion navigation is realized by solving parts degree of freedom and mapping the motion component to the target constraint direction. The interactive aid technology can easily eliminate error and escaped constraint realization and can improve the validity and efficiency of assembly intention capturing. The assembly constraint dynamic remove method and fastener assembly tools’manipulation and its effective space estimation technique are also studied in virtual environment. The virtual assembly technology of cable harness parts is researched based on mass-spring system whose dynamic characteristics in cable harness model are analyzed. The dynamic differential equations are solved by Verlet integration method. Aiming to improve the reality of simulation, the spring dynamic deforming constraint algorithm and cable harness mesh deformation update algorithm are proposed.Four, assembly path and sequence planning for virtual assembly process are studied. With favorable interaction of virtual assembly system a man-machine cooperation method to solve the assembly sequence planning for aerospace products is presented based on particle swarm optimization and genetic algorithm (PSO-GA). The assembly precedence constraint relationship model is studied which is described by assembly precedence relations and liaisons matrix. The code representation of genomes, chromosomes and particles is also studied. Then the fitness function with engineering significance is presented by comprehensive consideration of assembly continuity, assembly resource and influence of instrument and equipment. The geometric feasible assembly sequences are initialized and optimized based on PSO-GA in which the GA’s crossover operator is reconstructed by PSO. An application case is discussed to demonstrate good convergence and stability of the proposed algorithm. Meanwhile, the assembly path generation and storage are presented. Assembly BOM and animation generations and process data extraction strategy are proposed for assembly process files.Finally, a prototype of desktop virtual assembly process planning system is developed and realized. The system is divided to four modules: Assembly modeling, virtual assembly simulation, assembly sequence planning and assembly process files design and guiding. The data flows among these modules are described, and the development frame and environment are introduced. A complete virtual assembly process planning workflow case of an aerospace products component is studied to verify each module’s function by introducing functional interfaces in the flow. And the system has been applied preliminarily for the aerospace products.更多还原