Utilizing Cut Trees as Design Skeletons for Facility Layout

Facility layout provides a fertile area for the application of optimization models. There is a major cost associated with constructing or reconfiguring a facility. In addition, the number of layout possibilites is so large that human designers frequently have difficulty in generating good layouts. A cut tree is proposed here as the design skeleton for a family of facility layouts. It has some very attractive properties when used as part of an interactive system to support the designer in the analysis, construction and improvement of facility layouts. The cut tree has proven to be both easy to use and very powerful in aiding designers to generate quality layouts.     

交互式进化设计中的思维固化及改进策略

目的 探讨交互式进化设计(IED)中设计师思维固化现象的发生和成因,并提出改进策略。方法 首先,解构IED中设计师思维固化现象,阐明人的视觉搜索机制和IED算法机制对交互式进化过程中设计师思维固化的影响,对应提出“信息刺激”“增大种群数量”及“增大变异概率”策略;其次,基于豪斯多夫距离算法,提出产品形态交互式进化设计中思维固化的量化方法,以中式花瓶轮廓为例,在MATLAB软件平台下开发了产品形态交互式进化设计系统;最后设计对比实验进行验证。结果 实验结果表明所提策略在缓解交互式进化过程中设计师的思维固化具有显著性。结论 提出的改进策略有助于提高交互式进化设计方案输出的创新性,为交互式进化设计中设计师认知特征提供新的研究视角。     

A hybrid approach for concurrent layout design of cells and their flow paths in a tree configuration

The layout design of multiple-cell automated manufacturing systems includes cell layout design and flow path layout design. Traditional layout methods often treat these two as separate problems and the sequence for solving them is usually cell layout first and flow path layout later. However, approaches of these kinds have one major drawback, that is, they may produce cell layouts that are awkward or difficult for designers to conduct flow path layouts, or cell layouts that do not turn out to be as good as expected after flow path layouts have been performed. Other drawbacks of traditional layout methods include irregular shapes of cells, inaccurate calculations of flow distances, etc. This paper addresses the layout problem of cells and their connecting flow paths in a tree configuration. The proposed layout procedure is designed to avoid the aforementioned drawbacks of traditional layout methods by emphasizing concurrent layout design of cells and flow paths. It combines a search algorithm and mathematical programming models. The search algorithm has a backtracking procedure that allows one to explore alternative layouts, while the mathematical programming models help one obtain accurate layouts of cells and flow paths. The proposed layout procedure also interacts with designers and allows designers to include their qualitative consideration into the layout design. As a result, one can obtain more accurate and good-quality layouts with the proposed layout procedure.     

Unequal-area facility layout by genetic search

This paper applies genetic optimization with an adaptive penalty function to the shape-constrained unequal-area facility layout problem. We implement a genetic search for unequal-area facility layout, and show how optimal solutions are affected by constraints on permitted department shapes, as specified by a maximum allowable aspect ratio for each department. We show how an adaptive penalty function can be used to find good feasible solutions to even the most highly constrained problems. We describe our genetic encoding, reproduction and mutation operators, and penalty evolution strategy. We provide results from several test problems that demonstrate the robustness of this approach across different problems and parameter settings.     

Maximum weight matching and genetic algorithm for fixed-shape facility layout problem

To achieve efficient facility design, the problem of finding an initial slicing tree of a complete graph may influence the layout solutions in many ways. We introduce a maximum weight-matching algorithm to generate the slicing tree, which is used as an initial solution. This initial solution produces modifications to generate alternative layouts for further selection. The system employs a genetic algorithm (GA) as the search engine with a relationship weight function to obtain good solutions. The model is proposed to solve a fixed-shape layout problem. The research has made contributions to two areas. First, it defines a quality function for the clustering technique to generate an initial slicing tree. Second, it designs a process for generating layout alternatives that can take predetermined location constraints and weights based on relationships among facilities into consideration. We compare our initial slicing tree GA with other approaches in the literature. In addition, computational results to demonstrate the performance characteristics of our algorithm are also evaluated.     

有价票据视觉复检自动化包装系统设计

目的针对现有有价票据包装工艺中自动化程度低、人力成本高、分包效率低、出错率高的现象,设计一套视觉复检自动化分包系统。方法采用自动分拣机构实现票据高速分机和整理,并通过视觉检测技术检测票据编码的正确性;利用双工位机械臂和包扎机构实现快速包扎和整理。结果所设计系统分拣速度达800张/min,工作节拍可达80捆/min,最大限度地提高了系统工作效率。结论该设计为各类票据高速、高效包装系统的实现提供了参考。     

A heuristic approach on the facility layout problem based on game theory

Facility layout problems are related to the location of all facilities in a plant. Numerous research works related to facility layout have been published. The applicability of these various existing models may be limited by the fact that they all ignore competitive reactions to one's actions. In addition to external competitors, some internal problems of system such as material handling system design affect layout designs. For considering these effects, some researchers have investigated multi-objective approaches that in most cases lead to the optimisation of a weighted sum of score functions. The poor practicability of such an approach is due to the difficulty of normalising these functions and quantifying the weights. To the extent that competitors do react to a firm's actions and also the facility layout problem considers several conflicting objectives by distinct decision makers in the firm, the existing models may be oversimplifications of reality. In this paper, we modelled such a facility layout problem with conflicting objectives under a duopoly Bertrand competition as a game and solved it with a proposed simulated annealing meta-heuristic. Results obtained from solving some numerical examples confirm the effectiveness of the proposed model for the layout design.     

Facility layout optimization using simulation and genetic algorithms

Traditionally, the objective of a facility layout problem has been to minimize the material handling cost of the manufacturing system. While it is important to reduce the amount of material handling, the traditional methods do not address the actual time at which the material is transported. In today's short cycle time production environments, the timing of material movement may have a bigger impact on the productivity of the system than its cost. In this paper, a facility layout optimization technique is presented that takes into consideration the dynamic characteristics and operational constraints of the system as a whole, and is able to solve the facility layout design problem based on a system's performance measures, such as the cycle time and productivity. Each layout solution is presented in the form of a string that is suitable for analysis by a genetic algorithm technique. These solutions are then translated into simulation models by a specially designed automated simulation model generator. Genetic algorithms are used to optimize the layout for manufacturing effectiveness while simulation serves as a system performance evaluation tool. Combined with a statistical comparison technique to reduce the simulation burden, the test results demonstrate that the proposed approach overcomes the limitations of traditional layout optimization methods and is capable of finding optimal or near optimal solutions.     

基于视觉认知特性的作战显控界面信息结构布局研究

目的 智能化作战趋势相应地会对在作战显控系统界面的信息量和信息呈现内容提出要求。针对未来态势环境下显控界面信息结构更为复杂,且融入更多信息的显控系统界面需要不断迭代的问题,从显控界面的信息结构分类展开实验研究,设计不同的信息结构布局类型,从而进行认知绩效的视觉搜索测评实验。方法 通过文献分析,从认知特性与界面信息架构布局、飞行员的认知行为等方面出发,对相关成果进行综述梳理。运用眼动追踪实验,设计针对不同任务的视觉搜索实验,从而对不同信息布局形式的认知绩效进行评估测量。结果 实验结果表明,在“作战”与“导航”任务场景中“纵向任务栏型”布局形式整体更优于“横向主图型”任务布局。在“作战”任务中,纵向三分类型布局形式的绩效水平更优;在“导航”任务中,纵向二分类型布局形式的绩效水平更优。结论 针对复杂显控作战界面的信息呈现,可以通过设定与作战任务相匹配的不同结构布局来优化信息模块的合理分配方式,对后续在作战显控界面的信息模块布局设计优化起到一定参考作用。     

Validating the random search model for a double-target search task

A random visual search model was fit to 2980 search times obtained from a double-target search task. The overall adequacy and prediction accuracy of the model for various search time parameters like mean and median search times, and response times for both individual and pooled data show that subjects' search strategy may reasonably be inferred from search time distributions. The results also suggest the general applicability of the random search model for describing the search behaviour of a large number of subjects performing the type of search task used here, and the practical feasibility of its application for determination of stopping policy in optimization of inspection system design. Notwithstanding the general conformity of the data with the model, some extremely long search times were found, and this was accounted for by the characteristics of visual lobes, nonoptimum interfixation distances and inappropriate overlapping of lobes previously reported. An interpretation of temporal changes of subjects' search strategies during target detection was made by considering the cross-over phenomenon exhibited by the two cumulative detection percentage curves.     

IVECO车身视觉检测系统现场溯源研究

汽车车身视觉检测系统是大型、专用的车身总成三维尺寸自动化检测设备,系统组成复杂,测量误差难以确定。本以南京ＩＶＥＣＯ车身视觉检测系统为背景,提出了一种现场溯源技术,解决了测量结果不确定度的溯源问题。     

Using queuing theory and simulated annealing to design the facility layout in an AGV-based modular manufacturing system

An automated guided vehicle-based flow production system is used for manufacturing prefabricated bathroom units. One unit can occupy a space of more than 10?m². Due to large time deviations in sequential processes, queues are formed and greater plant space is needed. Reducing work-in-progress helps to save plant space but renders manufacture less efficient. The research explores better workstation arrangements. An open queuing network (OQN) model was used to approximate the flow production system. Since the problem of workstation arrangement is a combinatorial optimisation problem, simulated annealing (SA) was applied to search for a good solution. The combination of an OQN model and SA provides a powerful tool to solve the facility layout problem for a stochastic flow production system. The experimental results show that the proposed approach has the potential to guide industrial layout design and practice.     

MULTI-HOPE: A tool for multiple floor layout problems

The objective of most facility layout problems is to minimize material handling cost, which is directly proportional to both the distance between the machines and the mix, as well as the volume of products handled. The mix and volume of products are dependent on the demand patterns, and the distance is dependent on the layout plan used for the facility. Because it is relatively difficult to change the demand patterns, and hence the mix and volume of products, the primary focus of most designers has been to deal with the distance attribute of the material handling costs. The limitations of available horizontal space create a need to explore vertical expansion of facilities. This brings up new aspects of vertical material handling and flow that need to be considered in the facility design problem. In this paper, we present a genetic algorithm-based heuristic for generating block layouts for multiple-floor layout problems. This approach produces better solutions than existing simulated annealing-based heuristics for all but one of five multiplefloor test problems available in the literature.     

Cellular machine layout based on the Segmented Flow Topology

This paper introduces a facility layout design procedure for converting an existing manufacturing system with a predefined aisle structure to a cellular manufacturing system based on the 'segmented flow topology' (SFT) developed by Sinriech and Tanchoco. The proposed procedure is aimed at finding the best machine grouping, along with the locations of pick-up and delivery stations and machine layout for each cell based on an existing facility. The objective is to minimize the total material handling cost. In contrast to previous work in this area, the proposed design procedure takes into account both distance and material flow in forming machine clusters. In addition, a revised cost model for material handling system, which accounts for different aspects of capital and operating cost, is presented.     

A genetic algorithm and queuing theory based methodology for facilities layout problem

Facilities layout, being a significant contributor to manufacturing performance, has been studied many times over the past few decades. Existing studies are mainly based on material handling cost and have neglected several critical variations inherent in a manufacturing system. The static nature of available models has reduced the quality of the estimates of performance and led to not achieving an optimal layout. Using a queuing network model, an established tool to quantify the variations of a system and operational performance factors including work-in-process (WIP) and utilisation, can significantly help decision makers in solving a facilities layout problem. The queuing model utilised in this paper is our extension to the existing models through incorporating concurrently several operational features: availability of raw material, alternate routing of parts, effectiveness of a maintenance facility, quality of products, availability of processing tools and material handling equipment. On the other hand, a queuing model is not an optimisation tool in itself. A genetic algorithm, an effective search process for exploring a large search space, has been selected and implemented to solve the layout problem modelled with queuing theory. This combination provides a unique opportunity to consider the stochastic variations while achieving a good layout. A layout problem with unequal area facilities is considered in this paper. A good layout solution is the one which minimises the following four parameters: WIP cost, material handling cost, deviation cost, and relocation cost. Observations from experimental analysis are also reported in this paper. Our proposed methodology demonstrates that it has a potential to integrate several related decision-making problems in a unified framework.     

Integrating occupational health and safety in facility layout planning,part I: methodology

An influential factor affecting the efficiency of a manufacturing facility is its layout. In a production facility, measure for efficiency can be based on the total cost of transporting the items between different departments and throughout the facility. However, other factors may influence efficiency of the manufacturing facility too. As such are: supporting the organisation's vision through improved material handling, material flow and control; effectively assigning people, equipment, space and energy; minimising capital investment; adaptability and ease of maintenance; as well as providing for employee safety and job satisfaction. By incorporating health and safety measures in the initial design of a facility layout, the organisation may avoid money and manpower loss resulting from industrial accidents. This paper proposes a facility layout planning methodology which integrates the occupational health and safety (OHS) features in the early design of a facility layout. The model considers transportation cost in the facility as well as safety concerns. By this means, the OHS issues are reflected prior to the construction of a facility.     

Assembly system facility design

This paper addresses the design of an assembly system facility consisting of multiple assembly lines of different shapes. In such a design problem there are two conflicting objectives: (i) to minimize the overall area of the facility; and (ii) to maximize the efficiency of the material handling transportation system. We first address the optimization problem of objective (ii) when replacing objective (i) with a constraint on the facility area. We propose a mixed-integer linear program to determine the layout of a facility with given dimensions and with given assembly line areas and shapes (that cannot be changed due to technological considerations). In the layout model, the physical placement of each line within the facility is a decision variable. The objective function of the layout model is to minimize the distances traveled by material flow. Our performance analysis provides an indication of the maximal problem size that can be solved in a reasonable amount of time and we examine the effect of the problem parameters on the solution run time. This layout model is then incorporated into an efficiency frontier approach for facility design to address both objectives. Examples are presented to illustrate the use of the proposed facility design model.     

A methodology for solving the unequal area facility layout problem using distance and shape-based measures

This paper presents a methodology for solving the unequal area facility layout problem commonly encountered in industry practice. A mixed-binary nonlinear-programming model is formulated to capture the operational issues encountered on the shop floor. In particular, in addition to the distance measure that is typically used to quantify the material handling costs, the impact of geometry or the shape of the departments is quantified in the formulation of the model. A higher-level heuristic solution algorithm, based on a concept known as ‘tabu search’, is proposed to efficiently solve industry-relevant problems. The methodology not only considers the impact of both distance and shape-based measures simultaneously in the proposed initial solution finding mechanism, but also in the evaluation of the objective function during the entire search procedure, in the hope that it will lead to identifying a better final solution. Taking into consideration fixed and variable tabu list sizes, along with long-term memory with maximum and minimum frequencies, has led to developing six different heuristics for the solution algorithm. A single factor experiment based on randomized block design has been used to compare the performances of the six different heuristics on three different problem structures—small, medium, and large—using the total cost as the criterion. Based on this experiment, the characterizations of search procedures have been recommended to facilitate identifying the best solution for each problem structure. The proposed method is also compared with those in the published literature by solving fairly well known unequal area facility layout problems. When an improvement is observed, the comparison has led to identifying a percentage improvement in total cost of approximately 2.8% to 11.8%, thus demonstrating the effectiveness of the model and the algorithm.     

Solution of facility layout problems with pickup/drop-off locations using random search techniques

Due to non-polynomial hardness, the facility layout problem (FLP) becomes more critical when pickup/drop-off (P/D) locations are considered in the design of an open field layout under a manufacturing environment. This paper proposes an indigenous model of the facility layout problem based on random search techniques and its solution methodology using a genetic algorithm (GA), simulated annealing (SA) and a hybrid algorithm (HA). The paper illustrates the performance of different random search operating parameters in solving the facility layout problem considering P/D locations along the periphery of rectangular machine blocks. The preliminary experiments were carried out on three facility layout test problems having six, eight and ten machines in order to fix the different operating parameters such as crossover operator, crossover rate, initial temperature, temperature reduction factor, number of generations, population size, etc. The results of extensive preliminary experimentation were utilized to solve facility layout problems having 12 and 18 machines and, finally, were compared with the existing procedures in the literature. The experimental tables and related analysis performed via the solution methods by applying GA, SA and HA revealed that random-search-based modeling of FLP considering P/D and its solution as suggested in this paper is worth pursuing.     

基于RFID技术的运动器械包装生产线检验系统设计

目的针对传统人工方法进行运动器械生产线检验存在的缺点,设计一种用于运动器械出厂包装生产线的检验系统。方法将RFID射频技术、可视化软件和数据管理技术进行结合,利用RFID高效读写功能对生产线上输送的出厂器械进行有效的产品检验、产品管理和人员管理,以提升生产工厂智能化水平。结果经实际运行验证,该系统可自动完成40台器械产品的检验管理。结论所设计的检验系统运行稳定可靠,可以有效提升检验效率。