A Novel Representation Scheme for Disassembly Sequence Planning

The representation of the disassembly sequence is a key issue in maintenance planning. It involves a highly constrained combinatory problem, which is coupled with varying start and end nodes. These start and end nodes are dependent upon the nature of a maintenance task. In this paper, different representation and modelling schemes for disassembly sequence planning are first reviewed. Then, a novel representation scheme for disassembly sequence, which is generic and can be used to represent both the geometrical and precedence constraints dynamically in product disassembly, is proposed. Based on such a representation scheme, the process for the determination of possible disassembly sequences can be simplified. By taking into consideration disassembly constraints, the optimal disassembly sequence in relation to the component to be maintained (target component) can be quickly derived. This is achieved by pruning the search space of disassembly sequences, grouping related components into subassemblies, and identifying free components to facilitate disassembly oper-ations. Subsequently, the optimal disassembly sequence in relation to the target component can be obtained using genetic algorithms. In this manner, the disassembly sequences for a complex product comprising a relatively large number of components can be derived within a short time. A case study is used to illustrate the effectiveness of the representation scheme. Comparisons are made using the same case study with the AND/OR graph representation and the Petri net approach for disassembly sequence planning. The results show that the proposed representation scheme is simpler and is more efficient than the rest. ID="A1" Correspondence and offprint requests to: Dr L. P. Khoo, School of Mechanical and Production Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798. E-mail: mlpkhoo@nyu.edu.sg     

基于拆卸Petri网和混沌粒子群的拆卸序列规划

为解决燃气涡轮发电机组虚拟拆装训练中拆卸序列规划问题,提出了基于拆卸Petri网和混沌粒子群优化算法的拆卸序列规划方法。在基本Petri网的基础上进行拓展,引入了时间元素,构建了拆卸Petri网模型;针对粒子群优化算法容易陷入局部极值的不足,将混沌寻优方法嵌入到粒子群优化算法中,结合早熟评判标准,提高粒子群算法全局寻优能力。运用上述方法,以最短时间为目标,对分配机匣的完全拆卸序列进行仿真实验,得到了符合实际操作规律,可行有效的拆卸序列。     

Disassembly Planning Based on Precedence Relations among Assemblies

An algorithm is presented that is based on a representation method for products, which lets us show, intuitively, the hierarchical relationships among components and/or assemblies of the product. This paper presents an algorithm for establishing a partial non-destructive disassembly sequence of a product. The disassembly sequence can be obtained for a component as well as for a sub-assembly (group of different components). The disassembly sequence is obtained autonomously and automatically and can be used in a flexible manufacturing system. ID="A1"Correspondance and offprint requests to: F. Torres, Department of Physics, Systems Engineering and Signal Theory, University of Alicante, Crta San Vicente s/n, PO Box 99, Alicante, Spain. E-mail: ftorres@disc.ua.es     

基于Pareto解集蚁群算法的拆卸序列规划

为提高产品拆卸序列规划的效率,分析拆卸序列规划问题中的多个优化目标平衡问题,提出一种基于Pareto解集的多目标蚁群优化算法求解此类拆卸规划问题,并给出拆卸序列的构建过程。通过利用拆卸矩阵推导拆卸可行条件,获得可以执行拆卸操作的零件及其可行的拆卸方向。通过利用零件的轴向包围盒(Axis aligned bounding boxes,AABB)计算零件的拆卸行程。考虑拆卸方向改变次数、拆卸总行程、拆卸零件数量为优化目标,通过利用蚁群算法搜索可行解并计算各个解之间的支配关系,得到Pareto解集,实现求解优化的拆卸序列,给出算法的具体步骤。最后以单杠发动机为拆卸实例,利用所提方法进行拆卸序列规划求解,通过分析试验结果,并对比典型的单目标蚁群规划算法,证明了该方法的高效性和可行性。     

基于广义轴理论的产品拆卸路径规划

如何将所有可行的拆卸路径进行紧凑、合理的表达是实现产品拆卸路径规划时首要解决的问题.为此,要对指定拆卸类型下的装配体进行有效的子装配体聚类.为在产品拆卸路径规划中实现子装配体聚类的优化,同时避免传统方法所造成的组合爆炸等问题,引用并扩展了表达零件问紧密程度的配合关系等概念,并结合对装配结构和装配过程的深入分析,提出符合工程语义的广义轴理论以及拆卸优先级修正系数等概念.在具体操作上,首先借助邻接矩阵的表达形式并结合同轴度系数函数和拆卸优先级别系数分配表等对应关系得到同轴隶属度矩阵及其修正矩阵.然后,结合模糊数学中模糊聚类分析的有关算法,得到具有传递性的模糊等价矩阵以及分属不同截距下的动态产品聚类关系图.最后,结合此关系图和拆卸优先级别系数分配表,实现子装配体的聚类优化.经验证,所提方法增强了拆卸路径划分同工程实际的一致性,同时减少了计算工作量.     

基于子装配识别的产品拆卸序列生成研究

对含有较多零件的复杂产品拆卸方法作了讨论,提出了一种基于子装配识别的拆卸序列生成算法。根据装配连接图和干涉图识别出子装配体,然后将子装配体看作一个零件,采用装配经验知识与几何推理相结合的方法生成子装配体序列,最后以一个装配实例说明了算法的有效性。     

基于贪婪算法的产品拆卸序列规划

分析了产品实际拆卸过程中的不确定性,将实际产品拆卸序列规划转化为一类贪婪算法求解问题。以最少工具更换次数为指标,构建了基于贪婪算法的产品拆卸序列规划调整的贪婪准则,进而给出了产品拆卸序列规划调整流程。最后,通过一个简化的计算机主机箱的拆卸说明该方法的可行性和有效性。     

基于不确定规划的产品拆卸序列规划

分析了产品拆卸序列规划中的不确定性,在基于混合图的产品拆卸模型的基础上,将产品拆卸序列规划转化为一类不确定规划问题。以机会约束规划模型为基础,使用模拟退火算法,给出了基于不确定规划的产品拆卸序列规划求解流程和算法。最后,通过一个简化的计算机主机箱实例说明了方法的有效性及优越性。     

Automatic Subassembly Detection from a Product Model for Disassembly Sequence Generation

The time taken for the generation of assembly or disassembly sequences is proportional to the number of components in the assembled product. For each additional component considered, the number of possible sequences to assemble (or disassemble the product) increases combinatorially. Research work had been carried out to reduce this complexity so that unfeasible assembly sequences could be discounted. A significant approach to further reduce the time for the generation of the assembly sequences is to group components together into subassemblies and then to treat these subassemblies as "individual components". This will reduce the number of components involved in the search or generation of assembly sequences, and hence reducing the sequence generation time. This paper presents a methodology for automatically extracting subassemblies from a product in order to simplify the disassembly or assembly sequence generation.     

产品装配顺序的层次化推理方法研究

提出一种装配优先关系分类模型,将装配顺序规划过程中的各种装配优先关系分为几种优先关系,确定性工艺优先关系和模糊性工艺优先关系3类。并在此基础上,提出层次化装配顺序推理方法,分别从装配顺序的几何可行性、工艺可行性和工艺优良性3个层次,对装配顺序进行递进推理,最终得到性能优良的装配顺序。开发的产品装配分析软件原型系统－－PAAS可以对复杂产品的装配顺序规划进行有效的分析和优化。     

基于普通算法进行几何推理的参数化设计方法

提出了一种基于普通算法进行推理的参数化设计方法。该方法引入了建立和管理参数化模型的新策略 ,通过扩展一般的图形数据结构统一表示几何约束 ,基于普通算法实现几何推理。在此基础上开发了面向对象的参数化设计系统 ,验证了此算法的有效性     

一种面向拆卸稳定性的产品拆卸序列规划方法

针对拆卸过程稳定性问题,以及复杂产品拆卸图模型构建困难和效率低等不足,提出一种面向拆卸稳定性的拆卸序列规划方法。充分分析面向绿色制造和循环经济的拆卸的特点和原则;通过分析产品的CAD模型,构建一种集零部件类型、零部件可行拆卸方向集、零部件拆卸空间制约矩阵、零部件接触矩阵、零部件自由度约束矩阵等于一体的产品拆卸信息分析模型;提出相关拆卸优先原则和稳定性原则;给出基于拆卸过程稳定性的产品拆卸序列规划算法;通过一个完全拆卸和目标零件拆卸实例验证该算法的可行性、实用性。     

基于知识的装配序列规划方法研究

为了解决装配序列规划的计算机辅助生成问题,对产品的装配CAD模型进行了分析,得到与装配规划相关的几个重要信息,并对其进行知识表示。通过建立产品的装配特征矩阵,确定了装配零、部件在各个方向的自由度。根据从CAD模型中得到的信息和零、部件的自由度信息,制定了产品拆卸序列规划的推理规则和求解算法;按照“可拆即可装”的原则,倒置拆卸序列得到产品的装配序列。以球阀产品为例,详细介绍了本文提出的装配序列规划方法的应用。     

基于模拟退火遗传算法的拆卸路径规划

针对现存拆卸路径规划图论方法中的组合爆炸问题和遗传算法的早熟现象,给出模拟退火和遗传算法相结合的拆卸路径规划方法.在拆卸路径规划模型中,以拆卸效率最优作为优化目标,给出了算法流程.该算法对拆卸路径的全面寻优提供了一种新的思路.通过实例验证该算法的可行性,最后提出了进一步的研究方向.     

基于遗传算法的拆卸序列规划研究

为得到满足实际需要的产品拆卸序列方案,减少人工输入所带来的不便,利用联接矩阵和干涉矩阵,构建了产品拆卸序列的数学模型;利用干涉矩阵和联接矩阵,产生满足几何约束条件且经过初步优化的拆卸序列;利用基于拆卸序列规划的遗传算法,优化了上述拆卸序列;通过实例验证了此种基于遗传算法的拆卸序列规划方法的可行性及实用性。     

机械产品非线性装配顺序规划研究

提出了用于机械产品非线性装配顺序规划的关系码矩阵模型,通过编码将所有的装配关系信息集成于一个简单矩阵中,用连接模式,即二进制数模板技术来识别装配时零件的几何约束。基于关系码矩阵模型给出了规划可行的装配顺序,检测装配过程中零件的稳定性及识别子装配的计算方法,使用遗传算法搜索并优化装配顺序,用复合表表示遗传算法中个体的装配顺序。最后,通过一个实例验证了该方法的有效性。     

基于分层结构的拆卸序列规划研究

产品能否方便拆卸直接影响到产品的可回收性。拆卸序列规划是面向拆卸的绿色设计关键技术。通过与无向图的比较，提出了一种新的层次结构理论模型，给出了生成层次结构模型的方法和拆卸序列规划的生成规则。这种模型更接近拆卸的实际情况，大大提高了计算效率，也为拆卸路径的干涉检查减少了工作量。     

基于遗传算法的产品装配序列规划研究

为解决产品实际装配过程装配序列规划的问题,建立了描述装配过程中零部件间装配关系的几何干涉关系矩阵。设计了以装配换向次数、装配工具更换次数、装配体稳定性和基础件位置为目标函数的遗传算法,并改进了该遗传算法相应的交叉算子、变异算子和适应度函数,以确保算法的有效性。在初始种群生成时,输入由DELMIA软件虚拟拆卸得到的几何可行装配序列,改善种群的组成成份。将该遗传算法应用于某链轮的装配序列规划中,验证了该算法的有效性。     

A Multi-Objective Methodology for Evaluating Product End-of-Life Options and Disassembly

In recent years, sustainable manufacturing has become important all over the world. Manufacturers have begun to realise the need for the responsible use and management of resources in the life cycle of a manufactured product, especially the planning for product retirement. The common end-of-life options are reuse, remanufacture, recycle, landfill, and incineration. This paper discusses a multi-objective methodology for determining appropriate end-of-life options for manufactured products, set against the often conflicting objectives of minimising environmental impact and minimising deficit (or sometimes maximising surplus). Guidelines for determining feasible end-of-life options (including the economic value of products and their components) are discussed. A numerical index of the environmental impact of a material or process – the eco-indicator – is adopted. Except for landfill and incineration, components of economic value destined for reuse, remanufacture, or recycling have first to be extracted from the product. It is therefore necessary to determine the optimal stage of disassembly, when all economically valuable components are retrieved. In order to determine the extent to which a product should be disassembled during its retirement, one may consider minimising environmental impact or associated costs or maximising the rate of return. Two end-of-life disassembly charts are introduced showing the impact on the environment and cumulative costs incurred as a product is disassembled. One of the charts can be used to assist in product design or redesign, whereas the other can be used to determine the optimal stage of end-of-life disassembly of the product. An end-of-life disassembly chart for a telecommunication pager revealed that if the pager is disassembled and its components reused, remanufactured, or recycled, the costs incurred will be very high. The pager is not designed for end-of-life retirement. It is best landfilled. The end-of-life options of a coffee maker were investigated using the methodology. It is concluded that the coffee maker is designed for end-of-life retirement. Complete product disassembly is always mandatory. If the coffee maker were completely disassembled and all components processed, the total disassembly time is 97 s, and a surplus of US$0.1918 is even realisable. The coffee maker was found to be designed for end-of-life retirement.     

基于遗传退火算法的复杂产品装配序列规划方法

分析了可行装配序列的推理约束条件,建立了考虑装配体稳定性的优化评价模型。采用带记忆的遗传模拟退火算法进行复杂产品的装配序列规划,并通过大量试验分析确定了算法近优运行参数。最后以8E150ZLC柴油机机油泵为例验证说明该方法是一个行之有效的具有工程实际意义的产品装配序列规划方法。