拆卸序列规划中子装配体的识别与生成

子装配体识别是解决大规模拆卸序列规划"组合爆炸"问题的有效方法之一.为了准确有效地识别与生成子装配体,在装配体零部件间接触关系、联接关系和向位妨碍关系及其相应图模型、矩阵的基础上,提出了一种基于图模型和判断矩阵的拆卸序列规划子装配体的识别算法.该算法利用图模型对子装配体集合做加法,利用判断矩阵对子装配体集合做减法,首先依据子装配体识别准则对图模型检索生成潜在子装配体集合,然后依据矩阵判断公式从集合中排除不符合连续性原则、稳定性原则和可行性原则的子装配体,并筛选理想个数的符合重量标准、同质标准和价值标准的最终子装配体集合.以减速器实例验证方法的可行性和有效性.     

基于自动拆卸过程的装配序列生成方法研究

装配序列生成是装配工艺规划的基本任务,设计了一个基于自动拆卸过程的装配序列生成算法。首先,进行自动拆卸仿真,通过过程中的干涉检查生成可行的装配序列集。然后,定义了三类装配序列优先约束规则,对可行序列集进行过滤选择,得到可用于最终评价的少量装配序列。该算法在SolidWorks平台上得到了实现,给出了实例验证。     

基于模块化设计的混合图拆卸建模研究

拆卸建模是拆卸序列规划的基础,也是绿色设计的关键。在传统的拆卸序列规划过程中,随着产品零件数目的增加会造成“组合爆炸”问题。为解决该问题,提出了一种基于模块化设计思想的拆卸建模方法。首先,运用图论中有向图和无向图的概念分别表示零、部件之间的约束关系,并将有向图和无向图结合成混合图,建立产品混合图拆卸模型;其次,利用模块化设计中的模块划分原则生成子装配体,通过将模块化设计方法整合入混合图模型中,得到模块化设计的混合图拆卸模型,利用该模型可以有效地解决图论模型中边与顶点产生“组合爆炸”的问题;最后,以模块化设计的计算机主机箱的混合图拆卸建模为例来验证所提出的方法。     

开放式构架产品装配序列规划

和普通产品装配序列规划相比,开放式架构产品(open-architecture products,OAPs)以模块化结构为基础.装配序列规划(assembly sequence planning,ASP)包括两部分,即组成模块的零件装配顺序规划和模块之间的装配顺序规划.利用产品结构图、装配约束矩阵描述装配模型,建立物料清单(bill of material,BOM)表达模块化层次结构.考虑到OAPs中功能独立的模块其物理结构不一定独立,首先判断构成OAPs的各模块能否作为子装配整体进行独立的装配操作,并提出判断依据.对不能作为子装配整体单独装配的模块进行拆分,根据拆分结果调整BOM层次图.在此基础上分析各模块的装配约束关系矩阵,规划模块内部零件装配序列.最后结合OAPs的模块类型,利用层次优先方法规划模块之间装配序列.并以减速器为例对提出的方法进行了验证.     

基于工程语义约束的线束预装配自动规划方法

线束预装配是线束生产的重要环节,论文通过总结线束工艺设计中的工程语义约束信息,建立装配关联图模型,提出了一种线束预装配自动规划方法。该方法通过主件选择、最大子装配体提取、工程语义约束检测来实现对预装配序列自动规划,而无需与用户进行交互。最后的实例表明该方法是有效可行的,能较好的解决大线束图纸中装配序列规划问题。     

基于OBDD的拆卸序列表示模型的优化

拆卸序列的紧凑表示是拆卸序列的评价与优化的基础,AND-OR图是拆卸序列表示的一种典型方法,但是拆卸序列的AND-OR图表示模型存在冗余信息。通过对AND-OR图模型作等价变换,消除AND-OR图表示模型中的冗余信息。设计了拆卸序列的优化表示模型的生成算法,建立了优化的基于OBDD的拆卸序列表示模型,用来表示复杂装配体的拆卸序列。并论证了优化模型的拆卸序列表示可以节省存储空间,最后的实验表明,基于OBDD的拆卸序列优化表示模型的存储空间远小于AND-OR图的存储空间。     

武器评价中的权重问题研究

针对武器评价中属性指标权重的确定问题,提出了一种基于数学规划权重最优解的主、客观赋权法.主观权重由专家凭经验给出,客观权重由灰理论求解法给出.算例验证了其用于武器评价的有效性.通过数学规划模型求解属性指标权重的最优解,该解同时反映主观程度和客观程度,从而使武器评价结果较之传统方法更为合理,准确度更高.     

维修拆装工艺规划系统的研究

结合装备维修活动中的拆卸与装配问题,明确了研发面向维修的拆装工艺规划系统的必要性.提出了一个拆装工艺规划系统的构架,论述了系统的主要功能模块、工作流程以及所采用的关键技术.实现了装配建模、拆装序列规划、拆装序列评估与优化,以及拆装作业仿真等关键功能.实践表明该原型系统的设计切实可行,具有良好的应用前景.     

面向制造过程的装配公差模型研究

为了研究零件制造偏差对装配公差的影响,提出了一种面向制造过程的装配公差模型.基于小位移矢量方法建立零件表面公差模型,采用齐次坐标变换方法描述偏差累积,建立了工艺系统各组件的装配公差模型.在满足装配约束条件的前提下,考虑了装配零件的几何变动,利用统计法研究装配体的装配成功率.最后应用一实例对装配体进行了公差分析,验证了模型的合理性.该模型可以用于指导装配规划,避免不可装配性.     

基于模糊推理的不确定环境下拆卸工艺规划

回收产品因磨损等原因其结构和质量会发生改变,拆卸序列规划存在不确定性,拆卸前很难确定产品最优拆卸序列。首先建立一个模糊拆卸Petri网模型表示产品可行拆卸序列和拆卸过程存在的不确定信息,为降低产品质量和拆卸能力的不确定性对拆卸序列优化的影响,建立一个自适应的模糊推理系统,利用模糊推理和反馈学习的方法对产品各拆卸步骤的成本进行预测,然后通过计算不同拆卸序列下拆卸的收益来得到产品最优拆卸序列,最后通过算例证明了方法的有效性。     

An optimal algorithm for selective disassembly sequencing with sequence-dependent set-ups in parallel disassembly environment

This study considers selective disassembly sequencing in parallel disassembly environment in which two or more components can be removed by a single disassembly operation. The problem is to determine the sequence of disassembly operations to extract multiple target components while satisfying the precedence relations among disassembly operations. The objective is to minimise the sum of sequence-dependent set-up and operation costs. An integer programming model is developed after representing all possible disassembly sequences using an extended process graph, and then an optimal branch and bound algorithm is proposed that incorporates the methods to obtain the lower and upper bounds as well as a dominance property to reduce the search space. To show the performance of the algorithm, computational experiments are done on various random instances, and the results are reported. In particular, it is shown from the test results that the optimal algorithm requires much shorter computation times than a competitive commercial software package. Finally, a case is reported to illustrate the extended process graph and the solution algorithm.     

Using constraint-satisfaction to optimise disassembly sequences generated from AND/OR information

This paper applies a constraint-based method, shown to successfully find the optimal order of component removal using precedence information, to finding the optimal sequence via AND/OR data. Development of disassembly theory is vital for practically all product end-of-life strategies. In particular, Disassembly Process Plans (DPPs) allow the careful selection and removal of components for recycling and reuse. While AND/OR graphs explicitly embody all of the feasible DPPs of an assembly, generating the best plan is non-trivial due to the rapid increase in the number of solution paths. In contrast, defining the physical restrictions between the components using precedence relationships is implicit and hence compact. By converting AND/OR representations into precedence ones, not only is the size of the problem reduced, modified techniques developed previously are applicable. Dependent upon the structure of the subassemblies, two different approaches are used to achieve this: the introduction of dummy components, and by means of the set of operations upon the subassemblies. Thus an all-encompassing methodology is created that can deal with any DPP representation such that the optimal sequences may be found.     

Economical evaluation of disassembly operations for recycling,remanufacturing and reuse

This paper introduced a procedure which integrates economical factors into the scheduling of disassembly operations for Material Recovery Opportunities (MRO). MRO are defined as opportunities to reclaim post-consumer products for recycling, remanufacturing and reuse. Traditionally, recyclers have resorted to using heuristics for analysing the breakdown of products and the associated costs. In this paper, a quantitative method of disassembly analysis is developed. Its aim is to improve the efficiency of the disassembly planning process and to generate an optimal disassembly sequence which maximizes profit. Three economic indices are used to evaluate the trade-off between reclamation and disposal of individual components. A systematic procedure of generating an optimal disassembly sequence based on maximizing the profits of material recovery is presented. Three criteria are established to reduce the search space and facilitate recovery opportunities: (1) material compatibility, (2) clustering for disposal, and (3) concurrent disassembly operations. An example is provided on a product being disassembled for recycling at a local recycling plant in Canada.     

Partial disassembly sequencing considering acquired end-of-life product age distributions

Uncertainty management is a priority in remanufacturing operations due to uncertain end-of-life (EoL) product quality, quantity and return timing. Ignoring EoL product uncertainty can result in inefficient remanufacturing operations. In this work, an approach is developed that addresses the impact of EoL product quality uncertainty on partial disassembly sequences. Disassembly is performed on nearly all EoL products, yet it is vulnerable to uncertain EoL product quality, defined in this work as the remaining value of an EoL product compared to original equipment manufacturer standards. The developed approach converges to an optimal or near-optimal partial disassembly sequence provided that information regarding acquired EoL product age distributions is known and correlates to EoL product quality. A mathematical framework is introduced to evaluate disassembly sequences based on profit standard deviation and profit probability as well as the traditionally used expected profit. The approach is tested on an example case study to investigate the impact of uncertain quality on the optimal or near-optimal disassembly sequence, expected profit, profit standard deviation and profit probability.     

Value recovery from end-of-use products facilitated by automated dismantling planning

Circular economy is a promising business model that promotes sustainable development by closing material loops. Making progress toward a circular economy requires the recovery of valuable materials and components from end-of-use products and subsequent reuse of them in some form, thus maximizing the utility of components and materials. Currently, end-of-use products value recovery is carried out without a rational planning, causing the loss of the recoverable value embedded in material and components. To address this problem, dismantling planning and appropriate technologies should be employed to improve the economic performance of end-of-use products value recovery. In this paper, a two-stage dismantling planning method is proposed to find a profitable end-of-use strategy. In the first stage of this method, disassembly optimization model is constructed and can be executed to obtain the optimal disassembly plan allowing maximum preservation of component function value, in a preservative disassembly scenario. To speed up the modeling, a method for automatic generation of AND/OR graph—a structure of incorporating all possible disassembly operations and associated subassemblies, is presented. In the second stage of the method, in order to increase profitability, Pareto analysis is employed to identify bottlenecks to disassembly and automated/destructive technologies are considered to remove the bottlenecks. A hard disk drive serves as a case study to illustrate the suggested method.     

Robotic disassembly sequence planning using enhanced discrete bees algorithm in remanufacturing

Increasing attention is being paid to remanufacturing due to environmental protection and resource saving. Disassembly, as an essential step of remanufacturing, is always manually finished which is time-consuming while robotic disassembly can improve disassembly efficiency. Before the execution of disassembly, generating optimal disassembly sequence plays a vital role in improving disassembly efficiency. In this paper, to minimise the total disassembly time, an enhanced discrete Bees algorithm (EDBA) is proposed to solve robotic disassembly sequence planning (RDSP) problem. Firstly, the modified feasible solution generation (MFSG) method is used to build the disassembly model. After that, the evaluation criterions for RDSP are proposed to describe the total disassembly time of a disassembly sequence. Then, with the help of mutation operator, EDBA is proposed to determine the optimal disassembly sequence of RDSP. Finally, case studies based on two gear pumps are used to verify the effectiveness of the proposed method. The performance of EDBA is analysed under different parameters and compared with existing optimisation algorithms used in disassembly sequence planning (DSP). The result shows the proposed method is more suitable for robotic disassembly than the traditional method and EDBA generates better quality of solutions compared with the other optimisation algorithms.     

Selective disassembly sequencing with random operation times in parallel disassembly environment

Selective disassembly sequencing is the problem of determining the sequence of disassembly operations to extract one or more target components of a product. This study considers the problem with random operation times in the parallel disassembly environment in which one or more components can be removed at the same time by a single disassembly operation. After representing all possible disassembly sequences using the extended process graph, a stochastic integer programming model is developed for the objective of minimising the sum of disassembly and penalty costs, where the disassembly costs consist of sequence-dependent set-up and operation costs and the penalty cost is the expectation of the costs incurred when the total disassembly time exceeds a threshold value. A sample average approximation-based solution algorithm is proposed that incorporates an optimal algorithm to solve the sample average approximating problem under a given set of scenarios for disassembly operation times. The algorithm is illustrated with a hand-light case and a large-sized random instance, and the results are reported.     

Automatic derivation of transition matrix for end-of-life decision making

Recently strengthened environmental regulations have obligated manufacturing companies to treat end-of-life (EOL) products both environmentally consciously and economically. EOL treatment begins with disassembling a product into recyclable or disposable sub-assemblies. Therefore, the economic value of an EOL product is largely a function of the plan for its disassembly: the means by which it is to be disassembled into smaller sub-assemblies, and the choice of sub-assemblies to be disassembled first. In order to make these decisions, a disassembly structure describing every possible sub-assembly division and its disassembly path from the original product has to be presented in a typical form. A widely used form of such a structure is a transition matrix. A transition matrix shows all feasible sub-assemblies and their disassembly hierarchy. Whereas it can be easily transformed into mathematical disassembly planning problem, the tedious work required for its generation limits its practical use. In this paper, we propose an algorithm for automatic derivation of a transition matrix. The proposed algorithm provides an efficient way to derive a transition matrix based on a product's architectural information, which includes the product's physical connections and the relative geometric locations between individual parts. The algorithm was validated in deriving a transition matrix of a car door-trim. Our algorithm can significantly expand the applicability of transition-matrix-based disassembly planning research.     

Integrated approach for disassembly processes generation and recycling evaluation of an end-of-life product

An integrated approach for noble recycling is presented that puts forward the functional value of products and components. In a first step, the approach determines all feasible automatic disassembly sequences and in a second step all applicable recycling activities. This allows one to determine the most appropriate recycling process for an end-of-life product considering concurrent recycling techniques. The feasible automatic disassembly sequences are established by simulation in a virtual environment. The required generic disassembly product model, as well as the generic disassembly activity model, is presented by means of static and dynamic object-oriented diagrams. The recycling evaluation establishes an efficient solution responding to economic and ecological decision criteria. It is calculated applying a Goal-Programming approach transforming the multi-objective linear problem into a monocriteria linear program. The techno-economic decision model applied is Linear Activity Analysis. It allows one to integrate the generated disassembly processes based on single disassembly activities as well as other recycling techniques.