Selective disassembly planning for waste electrical and electronic equipment with case studies on liquid crystaldisplays

Waste Electrical and Electronic Equipments (WEEEs) are one of the most significant waste streams in modern societies. In the past decade, disassembly of WEEE to support remanufacturing and recycling has been growingly adopted by industries. With the increasing customisation and diversity of Electrical and Electronic Equipment (EEE) and more complex assembly processes, full disassembly of WEEE is rarely an ideal solution due to high disassembly cost. Selective disassembly, which prioritises operations for partial disassembly according to the legislative and economic considerations of specific stakeholders, is becoming an important but still a challenging research topic in recent years. In order to address the issue effectively, in this paper, a Particle Swarm Optimisation (PSO)-based selective disassembly planning method embedded with customisable decision making models and a novel generic constraint handling algorithm has been developed. With multi-criteria and adaptive decision making models, the developed method is flexible to handle WEEE to meet the various requirements of stakeholders. Based on the generic constraint handling and intelligent optimisation algorithms, the developed research is capable to process complex constraints and achieve optimised selective disassembly plans. Industrial cases on Liquid Crystal Display (LCD) televisions have been used to verify and demonstrate the effectiveness and robustness of the research in different application scenarios.     

A novel approach to product modularity and product disassembly with the consideration of 3R-abilities

In recent years, the production of electrical and electronic equipment (EEE) has been one of the fastest growing areas of manufacturing. The recent European Community waste EEE directives aim to promote the recycling, reuse and reduction (3R) of such waste. The 3Rs are becoming increasingly important, due to current strict environmental regulations. However, research to enhance 3R-abilities with better design presents some difficulties: there is no present analysis of the impact of each of the 3Rs and analytical methods are often too complicated, so there is a need for practical and simple guidelines. To resolve these issues, this paper presents a novel approach that considers the relationships between product components and identifies the ideal product disassembly pattern and modularity by constructing a component matrix, with regard to product disassembly. The product disassembly, which identifies modules and disassembly pattern, also initiates a strategy to enhance 3R-abilities. Two cases are presented to show the effectiveness of the proposed approach.     

The construction of a collaborative-design platform to support waste electrical and electronic equipment recycling

Recycling of waste electrical and electronic equipment (WEEE) is a very important subject not only from the viewpoint of waste treatment but also from the viewpoint of recovery of valuable materials. In the past, some obstacles make recycling challenging for today's manufactured products. First, it is difficult to gain all the information necessary to plan for the recycling evaluation, as most design information is owned and kept by suppliers. Another problem in recycling end-of-life (EOL) products is a lack of technologies to handle the very complex products that are being discarded today, because the knowledge of how to do so is owned by the recycler.This research demonstrates how to support WEEE recycling analysis by environmental information with the part of bill of material. A collaborative-design platform is further constructed and collected all the needed information using computer-aided design (CAD), enterprise resource planning (ERP), and product life-cycle management (PLM) systems. Through this platform, suppliers are required to provide component information to enable the manufacturer's design for disassembly and recycling analysis. The results demonstrate that designers can obtain disassembly and recycling information through the model, so that desirable changes can be made in the early stages of a design. An industrial case study from Taiwan is also provided to demonstrate the use of this model.     

回收不确定下WEEE逆向物流网络鲁棒优化设计

电子电器废弃物（WEEE）存在对环境和人体健康的危害,有效对其进行回收能避免此类危害和提高资源的利用率。WEEE逆向物流回收网络的设计为实现这一目标起到了关键的作用。考虑WEEE逆向物流网络运作的不确定性,引入风险偏好系数和约束背离惩罚系数,建立了WEEE逆向物流网络的鲁棒优化模型。该模型能允许决策者对系统运作的鲁棒水平进行调节,同时能允许决策者对风险偏好进行调节。仿真结果表明建立的模型能有效抑制逆向物流系统运作的不确定性,使系统具有更低的风险。     

WEEE treatment strategies’ evaluation using fuzzy LINMAP method

Electrical and electronic equipments (EEE) have already begun to be accumulated at the garbage dumps. This garbage accumulation brings big danger to the environment and human health. That’s why one should look for exploring the ways to dispose of these wastes and emphasize the waste treatment strategies. Waste treatment strategies also contribute either to local or global economies by creating a new sector and employment opportunities, and by reducing use of scarce resources. In this paper, a linear programming technique for multidimensional analysis of preference (LINMAP) method for solving multi-attribute group decision making (MAGDM) problems with preference information on alternatives in fuzzy environment is developed. The aim is to develop a fuzzy LINMAP model for evaluation and select of a waste treatment strategy for EEE. Thus, three treatment strategy alternatives and eight criteria are determined. The best strategy is selected and the key criterion is found accordingly. The best alternative is found to be treating waste electrical and electronic equipments (WEEE) by reuse and recycling methods.     

Disassembly information model incorporating dynamic capabilities for disassembly sequence generation

Industrial recycling and reusing is becoming more and more important due to the environmental and economic pressures. It involves disassembly activities to retrieve all the parts or selected parts. An information modeling for the disassembly and optimal disassembly sequence generation based on the information model becomes critical. Unlike the traditional graph based representation of product structure, this paper introduces an efficient and machine readable disassembly information model and then discusses a linear programming based optimization model for obtaining the optimal disassembly sequence from the proposed disassembly information model. A key feature of this approach is the incorporation and use of dynamic capabilities in its information model processing technique. Dynamic capabilities are added into the information model to handle state-dependent information such as parts' disassembly directions which may change after each disassembly operation. The overall information model is built in UML, and dynamic capabilities are represented as events in UML. The proposed method has been illustrated using an electrical–mechanical device.     

Intelligent decision making in disassembly process based on fuzzy reasoning Petri nets

Practical disassembly process planning is extremely important for efficient material recycling and components reuse. The research work for the process planning in literature focuses on the generation of optimal sequences based on the predictive information of products. The used products, unfortunately, exhibit high uncertainty since products may experience very different conditions during their use stage. The indeterminate characteristics associated to used products often makes the predetermined plan unrealistic. Their disassembly process has to be decided dynamically adaptive to the products' specific status. To be able to deal with uncertainty in a dynamic decision making process, this paper presents a fuzzy reasoning Petri net (FRPN) model to represent related decision making rules in disassembly process. Using the proposed fuzzy reasoning algorithm based on the FRPN model, the multicriterion disassembly rules can be considered in the parallel way to make the decision automatically and quickly. Instead of producing the disassembly sequences before disassembling a whole product, the proposed method makes intelligent decisions based on dynamically updated status of components in the product at each disassembly step. Therefore, it is adaptive to the changes that arise during the process. Finally, an example is used to illustrate the application of the proposed methodology.     

考虑零件功能性削减的多目标拆卸方案决策

为解决零件价值高低界限模糊、废旧产品拆卸深度不合理的问题,提出一种考虑零件功能性削减的产品多目标拆卸方案决策方法。分析零件具体损伤对拆卸工具、方向、约束状态的影响,建立损伤情况下的拆卸信息模型;结合各损伤形式对零件接触面功能性的削减作用,提出一种考量零件在产品中综合重要性的剩余价值排序方法,并由此建立一种动态的拆卸目标件选取模型;面向拆卸过程的经济性,建立包含“价值构成”和“成本构成”的目标函数,采用自适应遗传算法进行序列规划求解,并反向决策零件的回收去向;以受损的减速器为例,获得产品的最佳拆卸深度和各零件的回收去向,充分挖掘零件的利用价值,验证所提方法的经济性与科学性。     

Robustness analysis of non-ordinary Petri nets for flexible assembly/disassembly processes based on structural decomposition

Design of robust supervisory controllers for manufacturing systems with unreliable resources has received significant attention recently. Robustness analysis provides an alternative way to analyse a perturbed system to quickly respond to resource failures. Although we have analysed the robustness properties of several subclasses of ordinary Petri nets (PNs), analysis for non-ordinary PNs has not been done. Non-ordinary PNs have weighted arcs and have the advantage to compactly model operations requiring multiple parts or resources. In this article, we consider a class of flexible assembly/disassembly manufacturing systems and propose a non-ordinary flexible assembly/disassembly Petri net (NFADPN) model for this class of systems. As the class of flexible assembly/disassembly manufacturing systems can be regarded as the integration and interactions of a set of assembly/disassembly subprocesses, a bottom-up approach is adopted in this article to construct the NFADPN models. Due to the routing flexibility in NFADPN, there may exist different ways to accomplish the tasks. To characterise different ways to accomplish the tasks, we propose the concept of completely connected subprocesses. As long as there exists a set of completely connected subprocesses for certain type of products, the production of that type of products can still be maintained without requiring the whole NFADPN to be live. To take advantage of the alternative routes without enforcing liveness for the whole system, we generalise the concept of persistent production proposed to NFADPN. We propose a condition for persistent production based on the concept of completely connected subprocesses. We extend robustness analysis to NFADPN by exploiting its structure. We identify several patterns of resource failures and characterise the conditions to maintain operation in the presence of resource failures.     

Human–robot collaborative partial destruction disassembly sequence planning method for end-of-life product driven by multi-failures

Partial destructive disassembly (PDD) of large complex products often requires human–robot collaborative disassembly (HRCD). Therefore, a human–robot collaboration partial destructive disassembly sequence planning (HRCPDDSP) method of end-of-life products driven by multiple failures is proposed to obtain the optimal disassembly sequence to improve disassembly efficiency and degree of automation. Based on the product disassembly priority and part failure characteristics, an information model of the HRCPDDSP method is constructed. Furthermore, the model is expressed as a constraint matrix and recycling decision matrix. A multi-layer chromosome coding method, including HRCD, destructive constraint, and node layers, is proposed of the characteristics of the HRCPDDSP method. The approximate optimal sequence of human–robot collaboration PDD is achieved by improving evolutionary mechanisms such as selection, crossing, and mutation. Finally, the model and algorithm are applied to solve a case of HRCPDDSP, and the feasibility and effectiveness of the proposed method are further verified by comparison with other disassembly modes.     

Multi-objective partial disassembly optimization based on sequence feasibility

A sustainable manufacturing system integrates production systems, consumer usage behavior, and End-of-Life (EoL) product value recovery activities. Facilitating multi-objective disassembly planning can be a step toward analyzing the tradeoffs between the environmental impact and profitability of value recovery. In this paper, a Genetic Algorithm (GA) heuristic is developed to optimize partial disassembly sequences based on disassembly operation costs, recovery reprocessing costs, revenues, and environmental impacts. EoL products may not warrant disassembly past a unique disassembly level due to limited recovered component market demand, minimal material recovery value, or minimal functional recovery value. The effectiveness of the proposed GA is first verified and tested using a simple disassembly problem and then applied to the traditional coffee maker disassembly case study. Analyses are disaggregated into multiple disassembly network optimization problems, one for each product subassembly, resulting in a bottom-up approach to EoL product partial disassembly sequence optimization.     

离散鲸鱼算法求解拆解序列规划问题

工业产品的回收再制造有利于降低生产成本和保护环境,而制定优秀的产品拆解序列规划提高拆解效率、降低回收成本为其关键.针对回收设备在实际拆解中的因素,建立一种基于离散鲸鱼算法(DWOA)的拆解序列规划模型.该模型目标函数以位置改变为代价作为新的评价指标,利用分层组合的方法快速生成初始群体.离散鲸鱼算法具有优先保护约束交叉机制、启发式变异、优秀的全局和局部搜索能力.以回收上橡皮板和空气围带进行对比实验,结果表明在相同时间下,离散鲸鱼算法的算法稳定性、寻优能力、收敛速度都要优于其他算法.     

A hybrid metaheuristic algorithm for a profit-oriented and energy-efficient disassembly sequencing problem

Value recovery from end-of-life products plays a key role in sustainability and circular economy, which starts with disassembly of products into components for reuse, remanufacturing, or recycling. As the process is often complex, a disassembly sequencing problem (DSP) studies how to optimally disassemble products considering the physical constraints between subassemblies/disassembly tasks for maximum profit. With a growing attention on energy conservation, this paper addresses a profit-oriented and energy-efficient DSP (PEDSP), whereby not only the profit is maximized, but also energy consumption is accounted as an important decision criterion. In this work, a disassembly AND/OR graph (DAOG) is used to model a disassembly diagram for a product, in which the ‘AND’ and ‘OR’ relations illustrate precedence relationships between subassemblies. Based on the DAOG, we propose a hybrid multi-objective metaheuristic that integrates an artificial bee colony algorithm, a non-dominated sorting procedure, and a variable neighborhood search approach to solve the PEDSP for Pareto solutions. The proposed method is applied to real-world cases (i.e., a simple ballpoint pen and a relatively complex radio) and compared with other multi-objective algorithms. The results indicate that our method can quickly produce a Pareto front that outperforms the alternative approaches.     

Disassembly planning of mechanical systems for service and recovery: a genetic algorithms based approach

In a perspective of improving the behavior of a product in its whole life cycle, the efficient planning of the disassembly processes acquires strategic importance, as it can improve both the product’s use phase, by facilitating service operations (maintenance and repairs), and the end-oflife phase, by favoring the recycling ofmaterials and the reuse of components. The present paper proposes an approach to disassembly process planning that supports the search for the disassembly sequence best suited for both aspects, service of the product and recovery at the end of its useful life, developing two different algorithms. Notwithstanding their different purposes, the two algorithms share the typology of modeling on which they operate, and the logical structure according to which the genetic search procedure is developed. The choice of implementing genetic algorithms was prompted by the intrinsic complexity of the complete mathematical solution to the problem of generating the disassembly sequences, which suggests the use of a non-exhaustive approach. As is shown in the results of a set of simulations, both algorithms may be used not only for the purposes related to disassembly process planning but also as supporting tools during the product design phases. This is especially so for the second algorithm, that deals with the problem of a recovery-oriented disassembly through an all-encompassing approach, combining economical and environmental considerations, and extending the evaluations to the whole life cycle of the product. This formulation gives this algorithm and autonomous decisional capacity on both the disassembly level to be reached, and the definition of the optimum recovery plan (i.e., the best destination for the disassembled components, based on some significant properties of them).     

Analysis of the Petri net model of parallel manufacturing processes with shared resources

A method of analysis for a class of Petri nets (PNs) called parallel process net with resources (PPNRs) is presented in this paper. The proposed analysis method is based on reduced reachability graph (RRG) of PPNRs to verify the correspondence between required specification of manufacturing system and its PN representation. In order to reduce the reachability graph (RG), a new technique is proposed which incorporates the transition vectors (TVs) to determine all the enabled transitions at a given state of system and to recognize them as dependent or independent. An algorithm, based on the idea of simultaneous execution of concurrently enabled independent transitions, is developed to reduce the RG and its analysis is also performed. Moreover, relationship between the reduction of RG and parallel structure in the PN model is discovered. The proposed technique replaces the RG by a structure which directly depicts concurrent execution and does not show the irrelevant states by presenting the concurrent behavior of system in the reduced state space. The analysis of PPNRs based on RRG generated by proposed method is also presented and demonstrated by a practical example.     

Enhancing disassembly and recycling planning using life-cycle analysis

Both the general public and governmental agencies highly prioritize resource optimization (energy and material) and environmental issues such as ozone, acid rain and global warming in the life-cycle context. Disassembly and recycling are also increasingly important in most industrial countries due to the significant increase in the quantity of used products being discarded. Disassembly of used products has been recognized as necessary to make recycling economically viable in current state-of-the-art reprocessing technology. This emerging trend requires incorporating environmental considerations into design strategies. This study presents a graph-based heuristic method for disassembly analysis of end-of-life products, which incorporates the Eco-Design concept. Product components and their assembly relationships from the bill of material BOM are adopted to split the graph into sub-graphs denoting modular sub-assemblies. The life-cycle analysis LCA is then used to analyze disassembly trees, from which a disassembly sequence can be derived. Designers can use the analytical results to evaluate the dis-assemblability and recyclability of products when they are designed.     

To disassemble or not: a computational methodology for decision making

Environmentally conscious manufacturing is an important paradigm in today’s industrial practices and disassembly is a crucial factor in implementing this paradigm. Disassembly allows the reuse and recycling of parts and products that reach their “death” after their life cycle ends. There are many questions that must be answered before a disassembly decision can be reached. The most important question is economical. The cost of disassembly versus the cost of scrapping a product is always considered. This paper develops a computational methodology that allows decision-makers to calculate the disassembly cost of a product before it is built. The methodology makes it simple to perform “what if” scenarios fairly quickly. A Java based application has been developed to implement this methodology and it uses computational algorithms and a graphical user interface to enable designers to simulate product designs. The front end user interface is a Java based application while the back-end is the combination of a data parser and disassembly engine, which also makes use of Java and XML technologies. The disassembly engine performs calculations based on data represented in an XML data store and runs as the back-end component of the computational tools. The user interface has the ability to display a dynamically configurable disassembly tree. The disassembly knowledge is represented in XML format to allow robust and scalable parsing and processing of the various disassembly alternatives that correspond to the configurable disassembly tree. Examples are presented to demonstrate the implementation and capabilities of the computational design methodology presented in this paper. Received: March 2005 / Accepted: January 2006     

Selective disassembly for virtual prototyping as applied to de-manufacturing

Selective disassembly involves separating a selected set of components from an assembly. Applications for selective disassembly include de-manufacturing (maintenance and recycling), and assembling. This paper presents a new methodology for performing design for selective disassembly analysis on the CAD model of an assembly. The methodology involves the following three steps: (i) identifying the components to be selectively disassembled for de-manufacturing by a software program or designer, (ii) determining an optimal (e.g. minimal cost) disassembly sequence for the selected components that involves a computationally efficient two-level reduction procedure: (a) the determination of a set of sequences with an objective of minimal component removals via a wave propagation approach that topologically order components in an assembly for selective disassembly, and (b) the evaluation of resulting sequences based on an objective function (e.g. minimal cost) to identify an optimal sequence, and (iii) Performing disassembly design decisions based on the evaluated optimal sequence. Preliminary implementation results of the selective disassembly methodology in sequencing and disassembly cost evaluation, and application of the selective disassembly technique for de-manufacturing assessment are presented.     

Business case Roteb: recovery strategies for monitors

Due to the introduction of extended producer responsibility, European Original Equipment Manufacturers (OEMs) are forced to set up a reverse logistic system for their discarded products. As part of this set-up, OEMs or their service providers have to determine strategies for the recovery of these products. This involves determining an optimal degree of disassembly and assigning optimal recovery and disposal options. In this paper, optimisation models presented in some of our earlier work, are applied in a business case. The case concerns the recycling of PC-monitors and was part of a broader pilot project at Roteb (the municipal waste company of Rotterdam, The Netherlands). By using the models, it is shown that the recycling costs can be reduced by about 25%. Additional cost savings are also indicated, resulting in overall savings up to 40%. Also, modelling issues are discussed in relation to models that can be found in the literature and finally directions for further research are pointed out.     

基于预留缓存的并发访问及多任务并行支撑技术研究

在航天装备在役考核试验执行中,对于存在时空重叠的多个任务以及子任务,需要应用并行执行支撑技术。本文以典型航天装备在役考核综合评估任务为对象,从任务流层面和数据流层面,采用基于预留缓存的多线程并行并发技术,对多任务进行并行处理和执行。依托自主研发的航天装备在役考核综合评估系统,对本文方法进行了验证。系统运行结果表明,采用本文的多任务并行执行支撑技术可以高效快速地对大纲设计、数据采集等多个过程进行并发执行控制,对多源数据进行并行处理计算,有效提高了在役考核试验执行和综合评估的效率。