Constraint ratio in product assembly planning

Assembly planning considers the product, process, and production system. The existence of constraints makes the assembly planning process difficult and time consuming. The planning degree of freedom (PDOF) for designers will be increased if the number of constraints is decreased on either the product or the other sides. A higher PDOF means that companies can be more flexible in responding rapidly to the assembly of parts. In this paper, a constraint ratio (C_R) has been defined to measure the influence of the product constraints on assembly planning. Some rules have been established to simplify the evaluation procedures of the constraint ratio of the product. Examples are illustrated and explained.     

水平井牵引机器人虚拟装配规划研究

快捷的装配工艺是水平井牵引机器人使用与维护的有力保障.结合机器人的结构特点,研究装配顺序与装配路径规划方法,并针对自主研制的水平井牵引机器人,开发虚拟装配规划系统,验证规划算法的有效性.     

面向装配序列规划的装配成本评价研究

针对装配序列的特点提出了一个装配成本评价的模型,认为装配成本与产品装配过程中装配方向的变化次数,产品组成零件装配后的运动不确定度总和有关.提出了基于零件的装配方向矩阵确定装配方向变化次数的方法,并根据装配基础件确定零件装配后的运动不确定度.采用了基于优先关系矩阵的干涉推理方法检验装配序列的可行性,并计算装配序列中可能产生的装配干涉数目,最后用实例验证了所提模型的有效性.     

复杂结构产品虚拟布局与装配设计系统研究

为了在设计阶段发现并解决复杂结构产品的布局和装配问题,针对复杂结构产品的特点,分析了复杂结构产品虚拟布局与装配设计系统的需求。以算法设计为基础进行布局方案设计,以虚拟装配设计为检验手段对布局结果的可装配性进行检验和评价。建立了系统设计过程的功能模型,阐述了复杂布局问题的求解算法、面向虚拟装配的产品建模技术和虚拟装配仿真技术等主要关键技术。在这些原理方法研究的基础上,以飞行器仪器舱为应用背景,进行了原型系统的开发,给出了部分运行实例。运行结果验证了系统原理及其实现技术的可行性和实用性。     

阀门产品的装配规划系统研究与应用

为满足制造企业对装配建模、装配序列规划及装配工艺方案设计等技术的需求,设计和开发了具有工程应用价值的复杂产品装配规划与仿真系统AeroAssem。介绍了系统的总体结构并结合在阀门装配的经验,以典型产品为例分别阐述了各主要功能模块所采用的关键技术及其应用情况。通过与国外装配规划系统相比,分析了系统在矩阵提取、序列规划及工艺图等方面的优势。AeroAssem系统为复杂产品的数字化装配规划提供了较为全面的、具有实际工程应用价值的解决方案。     

面向生产现场的虚拟装配工艺规划技术

针对生产现场的需求和虚拟装配技术的发展,阐述了虚拟装配技术在装配工艺规划、装配精度预分析、管路与线缆装配及装配现场管理等方面的应用和发展.提出了半沉浸式虚拟装配工艺规划系统的整体思路及实现方法;虚拟环境下的线缆和管路的离散控制点建模及动态布局技术;虚拟环境下的带公差的产品建模方法和装配精度预分析技术.指出虚拟装配工艺规划技术能充分利用人的经验和感知,通过模拟真实装配过程,不仅可实现产品的装配顺序和路径规划,而且也是提高装配精度和装配可靠性问题的有效手段,为提高装配现场现代化管理水平提供了有效途径.     

基于装配特征本体表达的虚拟产品建模研究

在借鉴元对象工具思想的基础上,给出了装配特征的本体表达框架。采用四层元数据体系表达装配特征,并用网络本体语言描述装配特征本体信息。基于上述表达框架,提出了面向虚拟产品的全息语义模型。给出了模型数据的存储结构以及模型信息的重组算法。最后,通过应用实例验证了所提出的理论和方法。     

An effective integration approach toward assembly sequence planning and evaluation

An integration strategy for assembly sequence planning and sequence scheme evaluation is proposed. This strategy can be used to plan a reasonable assembly sequence, to optimize a sequence scheme, and to predict whether a collision will occur between the assembly tool and assembled components by considering factors like target components and assembly resources. A hybrid method is presented for assembly sequence modeling that combines human-computer interactive operations to manually build a hierarchical assembly sequence main model and a hybrid graph method to automatically generate sub-assembly sequence schemes of the main model. An optimization algorithm based on time-cost is introduced to handle a best candidate components selection. This relieves the problem of limited capability found when handling large size assembly models with traditional methods. The essential issues involved in system implementation are discussed as well; these include a representation method for the assembly consequence model, an optimization model of assembly sequence planning, and an object-oriented system architecture model employed with multi-agent technology for visually evaluating the assembling process. This system, KM computer-aided assembly process planning, KMCAAPP, has been developed on the basis of our previous work, KMCAD3; KMCAAPP uses the presented approach. KMCAAPP can be integrated with CAD model from KMCAD3D. A case study shows that the presented approach can use large CAD assembly models and delivers a feasible and effective way to integrate the assembly sequence planning process with scheme evaluation by visually evaluating the assembling process. This allows the identification of design errors in a timely manner and mitigates economic loss.     

Efficient method of assembly sequence planning based on GAAA and optimizing by assembly path feedback for complex product

In the process of complex product assembly, assembly resources (fixtures, tools, operations, and so on) must enter assembly environment with parts together to rapidly finish product assembly. Assembly planning must take assembly resources into account fully. But, designer cannot plan every assembly procedure because of the lack of assembly resources during assembly design. Then, it will cause assembly failures and redesign for assembly easily. This paper investigates an efficient method of assembly sequence planning based on genetic algorithm and ants algorithm (GAAA) and optimizing by assembly path feedback to assembly process planning including assembly resources for complex products. Firstly, a new GAAA is investigated to rapidly plan assembly sequence in order to solve the nondeterministic polynomial-bounded problem in high searching and solving efficiency. Secondly, on the basis of the assembly sequence, a B-Rep filling algorithm which can form a swept volume between the part and its kinetic orientation is developed to plan assembly path interactively. Thirdly, the performance of the assembly path according to the assembly sequence is analyzed and sent back to avoid the most of assembly collisions and interventions during product assembly design. Lastly, we develop a simulating system to simulate assembly sequence and path based on component application architecture for CATIA V5. The simulating result proved that the proposed method of assembly sequence planning based on GAAA and optimizing by assembly path feedback for complex products is efficient. Assembly optimal design including assembly resources can work well.     

产品装配协调顺序模糊综合评价方法研究

装配协调顺序受到多种因素的影响,为了在装配工艺规划中获得最佳的装配协调顺序,提出面向装配过程的装配协调顺序综合评价方法,从装配协调路线、装配成本、装配精度三个方面,分别给出相应的评价函数,并通过层次分析法获得各评价函数的权重因子,再采用模糊综合评价法,得出最佳的装配协调顺序.实践表明,该方法在某型飞机机翼装配中得到应用,验证了算法的有效性.     

基于装配操作难度指标的零件级可装配性评价方法

产品可装配性设计(DFA)对缩短产品开发周期、降低生产成本和提高产品质量有着很大的影响,特别是对可装配性评价已经成为DFA中的重要一环。从装配的实际操作角度,列出零件装配的八个基本动作,分析影响零件基本动作的因素,构建基于神经网络的产品可装配性评价模型,形成基于操作难度指标的动作级评价和零件级评价的二级可装配性评价方法,最后应用构建的评价方法对CB齿轮泵可装配性进行评价实验。通过评价实验,证实了该评价方法具有先进性、可行性和较强的实用性。     

基于联合分析和定量指数的柔性产品平台多目标规划方法

针对单一模块化或参数化平台设计中客户需求响应能力不足的问题,提出基于联合分析和定量指数的柔性产品平台多目标规划方法。分析了柔性平台调节特征和优化趋势,建立了柔性产品平台的设计过程模型;引入联合分析获得产品属性重要度和属性水平对客户满意度的效用值,采用质量功能配置获得产品属性和内部组件的关联矩阵;进而提出定量的平台通用性指数和多样化指数,构建柔性平台调节设计的两目标优化模型,并使用多目标进化算法进行求解。总体上实现了柔性平台调节方案的定量分析建模和多目标优化设计。通过液压支架平台调节方案规划实例,证明了所提出方法的有效性。     

面向装配规划的可重构装配模型

为提高复杂产品装配规划的效率,针对当前装配模型不能有效支持结构重构的问题,分析了重构对装配模型中信息变更的影响,提出了一种基于装配关系元的装配关系模型表达方法,实现了装配模型中关系信息和层次信息的柔性关联,进一步给出了可重构装配模型的信息组织方法和存储机制。在引入相关重构算法概念的基础上,给出了装配模型信息动态管理维护算法,以保证装配模型信息在重构前后的完整性与一致性。通过产品实例说明了上述研究成果的可行性和实用性。     

产品可装配性评价技术的研究现状和发展方向

阐述了产品可装配性评价技术产生的背景,分析了影响产品可装配性的因素,综述了近20年来国内外关于产品可装配性评价技术的发展现状,分析了现有评价技术中存在的不足。产品可装配性评价技术发展水平的相对滞后。已成为DFA一步发展和虚拟装配技术发展的瓶颈问题,因此评价技术的进一步研究,对于整个虚拟装配技术的发展有着特别重要的意义,最后提出了今后产品可装配性评价技术的研究方向。     

零件级的可装配性分析评价模型的建立与实现

在分析了单个零件对产品可装配性的影响因素的基础上,提出了对零件级可装配性分析评价指标体系,建立了零件级可装配性分析评价模型,系统在I－DEAS软件包上用Open I-DEAS和VC＋＋为工具开发实现。     

基于大装配的产品装配建模研究

从虚拟样机的角出发,结合流行ＣＡＤ软件的特点,提出在大装配的环境中快速有效地进行产品配建模的４种方法：引用集方法、部件过滤方法、小平面模型方法,以及特征简化方法。在实际产品开发中应用些这方法取得了较好的效果。     

A multi-plant assembly sequence planning model with integrated assembly sequence planning and plant assignment using GA

In a multi-plant collaborative manufacturing system, the manufacturing operations and assembly operations for producing a product can be distributed at different plants at various locations. The components are assembled with assembly operations performed in a multi-plant assembly sequence. In this research, a multi-plant assembly sequence planning model is presented by integrating (1) assembly sequence planning, and (2) plant assignment. In assembly sequence planning, the components and assembly operations are sequenced according to the assembly constraints and assembly cost objectives. In plant assignment, the components and assembly operations are assigned to the suitable plants to achieve multi-plant cost objectives. The feasible assembly sequences are generated using the developed graph-based models of assembly precedence graphs and matrices. A genetic algorithm (GA) method is presented to evaluate the multi-plant assembly sequences with an objective of minimizing the total of assembly operational costs and multi-plant costs. The main contribution lies in the new model for multi-plant assembly sequence planning and the new GA encoding scheme for simultaneous assembly sequence planning and plant assignment. Example products are tested and discussed. The test results show that the presented method is feasible and efficient for solving the multi-plant assembly sequence planning problem.     

Integrated knowledge-based assembly sequence planning

This paper presents a novel approach and system for the automatic generation, selection and evaluation, optimisation, and simulation of assembly plans. The information and knowledge about a product and its assembly (e.g. assembly constraints, solid model and CAD database, heuristic rules) are described using a hybrid approach and model with numeric and symbolic representation. A new methodology is presented to generate all feasible assembly sequences of the product by reasoning and decomposing the feasible subassemblies, and representing them by the assembly Petri net modelling. Qualitative strategic constraints are then used to evaluate the feasible assembly sequences. In order to obtain a good assembly sequence, some quantitative criteria such as assembly time and cost, workstation number, operator number, and part priority index are applied to select the optimal assembly sequence. Based on DFA analysis, MTM time analysis, and assemblability analysis, estimates are made of the assembly time and cost of the product when each of these sequences is used. A knowledge-based system KAPSS has been developed to achieve the integration of generation, selection evaluation, and visualisation of the assembly sequences.     

基于知识的智能装配规划系统

为了保证装配工艺的合理性和实用性,提出了基于知识的智能装配规划方法。该方法利用联接件装配工艺的特点和知识,进行装配序列规划,建立了基于联接件知识的装配实例库,生成装配序列的途径有典型实例的匹配、标准实例的匹配和运用有向联接件知识的装配序列规划。为了使产品的装配周期最短,并提高装配系统的柔性和可靠性,提出了基于多代理的装配任务规划方法,该方法综合考虑了装配操作时间和装配工具变换时间等因素。     

面向虚拟拆装的产品装配模型及其应用

本文针对机械产品的拆装次序及次序表达进行分析讨论,设计了一种面向虚拟拆装的产品装配模型.该模型是一棵具有拆装次序意义的装配树,不仅能够描述产品的层次信息,而且保证了产品拆装实验合理正确的设计和执行.具有简单、高效、可靠、适应面广等许多优点,可用于各种装备虚拟拆装,具有广阔应用前景.