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     

Research on the selectable disassembly strategy of mechanical parts based on the generalized CAD model

Disassembly has gained much attention due to the growing concerns of material resources, energy conservation, and environmental conscious. The process of disassembly attempts to breakup a product into several pieces, with the expectation that the pieces together have a net value greater than the discarded product. In analyzing these aspects, one needs to determine all feasible ways to disassemble a product. This is especially true for the complex products like automobile, aircraft, etc. Most researchers took the algorithm of complete-disassembly planning to design for disassembly, although the feasible disassembly sequence can be obtained, parts of a assembled entity should be removed totally. And the required S (refers to disassembly sequence) could be gained through the proper analysis and evaluation; however, there are so many difficulties in this process and it is hard to obtain the optimum solution, especially when there are many parts in assembled body (such as automotive product). Therefore, it is very necessary to research the selectable disassembly algorithm of mechanical parts. This paper puts forward an algorithm on the selectable disassembly strategy of mechanical parts based on disassembly wave concept. It is comparatively easy and efficient to search, and get the optimal selectable disassembly sequence of mechanical parts with less amount of computing. It is so significant for all the steps of maintaining, recycling and discarding. This project is sponsored by National Natural Science Fund Project (5975042) and Shanghai Natural Science Fund Project (02ZF14024).     

面向再制造的基于Pro/Toolkit的拆卸仿真

产品拆卸是再制造工程中重要的环节,拆卸的好坏直接影响产品再制造性。通过研究Pro/Toolkit二次开发的方法,得到拆卸仿真系统开发的流程:建立产品拆卸模型,提取模型拆卸信息,规划产品拆卸序列,进行产品再制造拆卸评估。研究了层次概率模糊认知图的数学模型规化拆卸序列的方法,得出了实现变速箱目标拆卸的最优拆卸序列。分析了拆卸仿真系统的再制造拆卸评估准则,给出了从零件的拆卸时间、拆卸费用、环境性影响、经济性、可拆卸度性、再制造性、回收价值性、零件耐用性、再制造工艺性、技术稳定性等方面进行产品再制造评估的改进算法。最后使用MFC对话框设计技术设计再制造拆卸仿真系统的对话框,得到面向再制造的拆卸仿真系统。     

Mechanical Product Disassembly Sequence and Path Planning Based on Knowledge and Geometric Reasoning

A feature-based assembly model is proposed for disassembly sequence planning, and establishing a correct and practical disassembly path for the part in the product, based on geometric reasoning and knowledge. The fundamental assembly modelling strategy for a product is based on the mating features of its parts. An algorithm is introduced which uses the information provided by the mating features of parts in the product to find the candidate parts for disassembly and to carry out disassembly path planning. A complete and accurate interference checking approach is used to ensure no global collision while disassembling a part. In some cases, it cannot be implemented by geometric reasoning alone, so a set of criteria and heuristic rules based on knowledge, constraints, relationships among parts, and quantitative disassemblability assessment are used. It can also be carried out interactively by the user when necessary. The proposed method is integrated with the CAD model of the product. The user can visually disassemble the product while planning, so it is easier to carry out the disassembly planning and generate an optimal sequence.     

Ant colony optimization for disassembly sequencing with multiple objectives

Product disassembly takes place in remanufacturing, recycling, and disposal. The disassembly line is the best choice for automated disassembly, so it is essential that it be designed and balanced to work efficiently. The multi-objective disassembly line balancing problem seeks to find a disassembly sequence which provides a feasible disassembly sequence, minimizes the number of workstations, minimizes idle time, balances the line (ensures similar idle times at each workstation), as well as addressing other disassembly-specific concerns. However, finding the optimal balance is computationally intensive due to exponential growth, with exhaustive search quickly becoming prohibitively large. In this paper, an ant colony optimization metaheuristic is presented for obtaining optimal or near-optimal solutions to the disassembly line balancing problem. Examples are considered to illustrate implementation of the methodology. Conclusions drawn include the consistent generation of near-optimal solutions, the ability to preserve precedence, the superior speed of the metaheuristic, and its practicality due to its ease of implementation.     

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     

产品拆卸配置优化研究

通过对产品拆卸内在规律的分析 ,建立产品拆卸 BOM“与 /或”树模型。以产品拆卸 BOM“与 /或”树模型为基础 ,提出产品拆卸经济性优化配置算法 ,通过合理的数据结构提高计算速度 ,并设计了该算法的实现模块     

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。     

用遗传算法实现产品回收中的拆卸序列规划

拆卸是产品回收利用中的一个重要环节,拆卸规划的目的是找到最优的顺序,以使拆卸代价最小或者代价效益比最低。这里使用遗传算法来规划拆卸序列,产生满足约束条件的效率最好的顺序。最后算法在一个实际装配体上得到了验证。     

Optimization of disassembly sequence planning for preventive maintenance

Disassembly sequence planning is considered an important research topic in the manufacturing automation field. In recent years, in close collaboration with manufacturers, many investigations have been conducted to design robust and profitable dismantling systems. Therefore, the designers of new products have to consider the disassembly constraints in the design phase of products. Moreover, considering the disassembly constraints is important not only in the context of life end of a product but also in its life cycle in order to reduce problems related to its exploitation and maintenance. Consequently, the optimization of the disassembly process of a product is a crucial task for improving the product design. This article presented an automated disassembly sequence planning approach based on ant colony algorithm. The developed method permits the generation of an optimal and feasible disassembly sequence planning of a product from its computer-aided design (CAD) model. Several criteria were introduced in this approach such as part volume, tool change, disassembly directions, and the maintainability of wearing part. A comparison between genetic and ant colony algorithms was conducted to reveal the effectiveness of the proposed approach. A case study is presented and an implemented tool was developed. The obtained results demonstrate the satisfactory side of the considered criterions to identify the feasible disassembly sequence plan.     

Petri网在产品拆卸序列规划中的应用研究

拆卸是废旧产品中零部件再制造及材料回收再利用的重要环节,拆卸过程规划的目的就是为了寻找最优的拆卸序列。这里以Petri网为工具,建立了包括零部件回收价值及拆卸成本在内的产品拆卸Petri网模型,对模型进行求解,得到了满足需求约束的最佳拆卸序列。     

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.     

面向产品回收设计的拆卸序列规划

基于绿色产品设计的思想，定义了产品的层次化结构模型，对产品的拆卸进行了建模分析，并主要讨论了拆卸序列组合爆炸、零部件邻接矩阵、拆卸算法等关键问题，实现了产品回收与再设计的拆卸序列规划。     

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.     

面向绿色制造的产品选择拆卸技术研究

针对机电产品的绿色制造,分析了产品生命周期中设计、服役使用和退役处理三个阶段的产品零部件选择拆卸问题;提出了基于蚁群算法的产品选择拆卸规划方法,给出了面向选择拆卸的产品图建模和选择拆卸序列的动态构建过程,并考虑拆卸方向改变次数和拆卸零件总数原则,以求解优化的选择拆卸序列;讨论了面向全生命周期的产品选择拆卸平台构成,并初步实现了平台的功能.最后,用实例说明了选择拆卸平台的工作过程.     

Product cooperative disassembly sequence planning based on branch-and-bound algorithm

This paper focuses on the cooperative disassembly sequence planning (CDSP) problem which is essential to disassembly a large and complex product in practice. A disassembly hybrid graph model (DHGM) is constructed to describe the mating contact and noncontact priority relationships among constituting product components. Thus, the disassemblability constraint expression can be deduced from it by reasoning. The CDSP is different from the disassembly sequence planning except for they are NP-complete. Therefore, a novel method is presented to generate cooperative disassembly hierarchical tree (CDHT) from the DHGM based on branch-and-bound algorithm in which two user-defined variables are introduced to control the size of the CDHT .The optimal solutions with a minimal disassembly time are derived according to the objection function. Finally, an example illustrates the proposed method.     

A converse method-based approach for assembly sequence planning with assembly tool

In order to improve the quality and efficiency of assembly sequence planning for complex mechanical product, a converse method-based approach for assembly sequence planning is proposed. Firstly, the disassembly interference matrix of product and the disassembly constraint degree of part are defined. Product disassembly sequence is obtained through geometry reasoning algorithm and the searching work of disassembly sequence is simplified by the contact constraint set. Secondly, the maneuverability of tool is inspected through the using matrix and interference matrix of assembly tool. The infeasible disassembly sequence is excluded and product assembly sequence is obtained by reversing the order of disassembly sequence. Thirdly, the evaluation mechanism for assembly sequence is established to get the optimal assembly sequence and the optimal assembly sequence is selected by calculating the value of evaluation function. Finally, a vibration generator is illustrated to verify the validity and feasibility of the proposed approach.     

面向经济回收的产品设计

面向回收的产品设计能够使废旧产品得到更好的回收和重用，优化拆卸序列的生成必须基于产品拆卸的经济性分析。本文应用废旧产品拆卸与回收过程中的回收价值、拆卸费用、处理费用等主要指标，分析了产品的零件材料回收价值与拆卸工艺，建立了零件材料合理回收的评估方法。     

Optimal Disassembly Sequence Using Genetic Algorithms Considering Economic and Environmental Aspects

In this paper, a genetic algorithm (GA)-based approach for an optimal disassembly sequence considering economic and environmental aspects is presented. All feasible disassembly sequences are generated by a disassembly tree or an AND/OR graph. Using the disassembly precedence and the disassembly value matrix, a disassembly sequence is optimised. The precedence of disassembly is determined through a disassembly tree or an AND/OR graph and the value of disassembly is induced by considering both economic and environmental aspects in the disassembly, recycling, and disposal phases. Economic and environmental factors can be compared by the same measure through converting environmental factors into economic cost. To solve the disassembly sequence problem, a heuristic algorithm based on GAs is developed. The proposed GA can search for and dynamically explore the disassembly node through the highest disassembly value, keeping their precedence in order to identify an optimal disassembly sequence. It can also help to explore the search space, and an optimal solution can be obtained by applying the optimisation criteria. A refrigerator is used as an example to illustrate the procedure.     

基于改进遗传算法的拆卸序列规划

拆卸序列规划是拆卸回收的关键部分,为了提高拆卸效率,找到产品最优拆卸方案,根据产品拆卸对象的优先关系和连接关系建立优先约束矩阵,同时依据拆卸组合优化的特点改进基本遗传算法的染色体编码方式和遗传算子,基于优先约束矩阵判别拆卸序列的可行性,改进算法流程,并利用MATLAB软件进行编码运行计算,得出产品的最优拆卸序列,最后通...