A comprehensive approach to facility layout design and cell formation

Group technology (GT) and a facility layout problem share a common factor to optimize, which is the “Intercell Flow or Material Handling Flow”. Most group technology-based approaches use binary part-machine incidence matrix for cell formation. Impacts of flow volume analysis between machine pairs have not been analyzed in the design of cellular manufacturing systems. It is important to analyze the placement of machine cells for reduced material handling costs at the grouping stage itself. This paper develops a method to integrate GT philosophy with a facility layout problem using “From–Between” relationship chart as a tool. A new optimization technique with a “from–to chart” as the primary input, is used to determine the cell formation. A modified grouping efficiency measure is used to determine the efficiency of grouping. A genetic algorithm-based approach is used for machine cell placement within a layout matrix. Cells formed using the proposed approach show reduced intercell flows, high grouping efficiencies and reduced material handling costs when cells are placed in a layout grid compared to existing cell formation approaches.     

Enhancement of performance of Genetic Algorithm for job shop scheduling problems through inversion operator

It is observed that the optimization technique Genetic Algorithm is gaining more importance over the past several years. With high computing power we are able to apply soft computing techniques to solve complex problems in less time. An approach through Genetic Algorithm to solve job shop scheduling problems using inversion operator has been tried, with make-span objective. Computational experiments of this attempt have shown better solutions coupled with appreciable reduction in computer processing time. A set of 20 selected benchmark problems were tried with the proposed heuristic for validation and the results are encouraging. The inversion operator is found to perform better.     

A new history-independent modeling approach for feature-based design

The majority of current feature-based modeling systems employ model history to store feature creation operations and re-execute them sequentially after each modification, which is called history-based modeling. Due to the static feature creation order, history-based modeling causes some problems during the reevaluation of the model, such as the evaluated model does not correspond to its specification, the operation can only refer to the boundary entities created by the previous operations, high computation cost, etc. In this research work, a new history-independent modeling approach is proposed. For the “remove feature” operation, only boundary faces originating from the feature being removed, and the intersecting features are modified for updating the resulting BRep model. For the “modify feature” operation, the feature being modified is first removed from the product model and then re-added with the new specifications, thus its creation step in the model history is changed. As a result, some of the problems caused by the static feature creation order are solved. During the reevaluation, the computation time is dependent solely on the execution of the feature and its intersecting features being edited. The computational complexity of the boundary evaluation using the proposed method for three representative models has been analyzed based on Open CASCADE. A case model was studied in a proof-of-concept prototype system to demonstrate the proposed modeling approach.     

An iterative approach to system setup problems in flexible manufacturing systems

System setup problems in flexible manufacturing systems deal with short-term planning problems such as part type selection, machine grouping, operation assignment, tooling, fixture and pallet allocation, and routing. In this article, we consider three of the subproblems: part type selection, machine grouping, and loading. We suggest a heuristic approach to solve the subproblems consistently with the objective of maximizing the expected production rate. The proposed procedure includes routines to generate all possible machine grouping alternatives for a given set of machines, to obtain optimal target workloads for each grouping alternative, and to allocate operations and tools to machine groups. These routines are executed iteratively until a good solution to the system setup problem is obtained. Computational experience is reported.     

Heuristic solution approaches for combined-job sequencing and machine loading problem in flexible manufacturing systems

Job sequencing and machine loading are two vital and interrelated production planning problems in flexible manufacturing systems (FMSs). In this research, attempts have been made to address the combined job sequencing and machine loading problem using minimization of system unbalance and maximization of throughput as objective functions, while satisfying the constraints related to available machining time and tool slots. This research describes two heuristics to deal with the problems. Heuristic I uses predetermined fixed job sequencing rules as inputs for operation allocation decision on machines, whereas heuristic II uses genetic algorithm based approach for simultaneously addressing job sequences and operation machine allocation issues. Performance of these heuristics has been tested on problems representing three different FMS scenarios. Heuristic II (Genetic algorithm based) has been found more efficient and outperformed heuristic I in terms of solution quality.     

Product Grouping and Resource Allocation in Multiline Manufacturing Systems

This paper studies the product grouping problem and the resource allocation problem in the design of manufacturing systems where multiple production lines are used to manufacture a range of products. Each production line in the product grouping problem is dedicated to manufacturing a group of products. A mathematical model is developed to determine the number of product groups and the composition of each product group in the manufacturing system. For the resource allocation problem, a mathematical model is developed to determine the optimal resource allocation scheme for each production line and the optimal inventory level for each product. A genetic-based algorithm is proposed to solve the product grouping problem and the resource allocation problem simultaneously, and its results are compared to those of the conventional heuristic approaches. The proposed genetic approach is a simple but effective means of solving these problems.     

Cost estimation system of dies manufacturing based on the complex machining features

Part manufacturing estimation cost is a critical and important task for industrial firms. Price evaluation helps the enterprise occupy a successful competitiveness in the market. In fact there are three main approaches for the manufacturing cost evaluation the analytic approach, the analogic approach and the parametric approach. This paper presents a cost estimation system of manufacturing dies based on a semi-analytic approach. The developed system uses a semi-analytic approach based on the principle of the analogic approach and analytic approach. This principle has recourse to the analogic approach to search for analogies between the shapes to be machined before grouping them into complex machining features [1]. For each feature parameter the system generates a process to be used as a sample and consequently a model of machining time. In a second stage and by using the analytic approach, the cutting time is determined either by removal rates of metal units for rough operation (cm³/min) or from the finishing operation surface (cm²/min) or by both production ways [1]. The after cutting return time is calculated through the equations developed for each machining type [2].     

Complex nonlinear behaviors of drilling shaft system in boring and trepanning association deep hole drilling

This paper introduces a novel meta-heuristic algorithm called a “performance-enhancement algorithm”, to solve the part-machine grouping problem. The process of applying the algorithm begins with allocating the parts and machines randomly into different clusters and assigning each of them a uniform initial membership index to each cluster. Each of the parts and machines are then placed in different clusters in turn, and the fitness function is recorded in order to adjust the membership index. Finally, each part and machine is reallocated to the cluster with the highest membership index to get the algorithm ready for next generation. To evaluate the solution quality of this type of grouping scheme, four indexes (total bond energy, exceptional elements, machine utilization, and grouping efficacy) are used as the performance measure of the proposed algorithm. The algorithm has been applied to solve several well-cited problems, and the computational results show that the novel algorithm is effective in finding the best solution and revolution ability.     

控制网络环境下高速铁路重型施工装备的运动综合与协调控制

在中国国家自然科学基金项目《网络环境下多通道电液比例控制系统的运动综合与协调控制》、中国国家高技术发展计划(863计划)项目《DCY850吨运梁车》和中国铁道部项目《高速铁路客运专线施工机械》共同资助下,讨论面向高速铁路和跨海大桥施工的重型构件搬运及施工装备(TCM HC)所涉及的分布式电液比例控制系统的运动综合、协调控制与功率传输问题,报告基于网络控制架构的解决方案所涉及的网络规划、控制策略和多任务分配与调度研究成果。提出面向工程应用的网络控制系统设计框架,强调在综合分析的基础上,进行网络规划和控制策略的分离设计。网络规划中,通过估计网络负载和引入频谱能量分析法粗拟出各控制回路的采样周期范围,基于非抢占RM算法设计带宽分配策略,确定各任务周期和优先级配置,满足网络的可调度性。针对有界长时延和随机短时延等两种情况,研究NCS节点级的滑模控制策略。采用确定性设计方法对有界长时延网络控制系统提出基于增广状态模型的滑模控制策略。对于输出反馈系统设计出带有状态估计器,且满足分离定理的滑模控制律。针对随机小时延网络控制系统提出TEE工作方式下的在线时延观测和估计方法,设计出基于在线回路时延估计的离散滑模控制器,可有效避免常规随机控制中大量存在的在线均值和方差运算。以DCY850运梁车的操纵与控制为对象,探讨大型分布式智能机械的运动综合与协调控制问题,提出网络控制与电液比例控制相结合的整体解决方案。针对多轴     

Diagnostic Monitoring of Rolling-Element Bearings by High-Frequency Resonance Technique

In the present work, investigations by high-frequency resonance technique for diagnosis of defect frequencies of rolling-element bearings are reported. Raw vibration signature of the bearings at different speeds of operation has been demodulated. Envelope detected spectrum is analyzed to evaluate various defect frequencies and their energy levels. Experimentally evaluated frequencies are compared with theoretically determined defect frequencies. These frequency values and their energy levels are used to monitor intrinsic condition of bearings as well as to establish severity of existing/developed defects in the bearings. Relative comparison of bearings of the same type are made at various operating speeds under identical conditions of operation on the basis of identified defect frequencies and severity of defects.

The paper gives a realistic approach to monitor intrinsic condition of a bearing. Investigations given in the paper may have a potential for performance evaluation and may act as a reliable tool to establish safe limit for bearing operation. Investigations may serve as a quality control instrument for the earliest detection of even the smallest nature of defect existing in a bearing and may be used for “on-line” bearing condition monitoring as well as routine “quality control” instrument on the test bed for the diagnostic monitoring of rolling-element bearings.     

Output-only stochastic identification of a time-varying structure via functional series TARMA models

The problem of output-only stochastic identification of a Time-Varying (TV) laboratory structure is considered for the first time via a Functional Series Time-Dependent AutoRegressive Moving Average (FS-TARMA) approach. The approach is based on the modelling of a single non-stationary vibration response via a non-stationary parametric FS-TARMA model. The steps and facets of the identification procedure are presented, and the obtained model is used for structural characteristics recovery and vibration signal analysis. For purposes of comparison, multiple “frozen-configuration” stationary experiments are also carried out and a sequence of “frozen” stationary models are identified. The results of the study demonstrate the applicability, effectiveness, and high accuracy of the non-stationary FS-TARMA approach in capturing and analyzing the TV structural dynamics.     

Announcement of coming events

For some years, the concept of “resolution” has been a source of some confusion and much discussion in the imaging of structures using “high resolution” electron microscopy. More recently, somewhat analogous confusion has arisen over the meaning of the spatial resolution of elemental concentration determinations in modern “analytical” electron microscopes by energy-dispersive X-ray spectrometry. The confusion has arisen, just as in the imaging case, as a consequence of using the machines at the limits of their capabilities, where “common sense” definitions lose much of their utility. In the case of imaging, the concept has received considerable attention, and some quite general statements are now widely accepted as defining the “point to point”, “line” and “information limit” resolutions and their interrelationships. For the case of compositional analysis, however, little discussion has taken place toward a common view of the important concepts and their interrelation. We here attempt a discussion of the concept of spatial resolution of elemental concentration variations, hoping to at least clarify some of the important factors - in particular, considering the specimen-dependent contribution through beam spreading in the sample and the form of the actual concentration variation, versus the primarily machine-dependent factors of initial probe size and sensitivity limits.     

面向敏捷制造的企业资源计划的设计与开发

针对敏捷制造的新的功能要求,设计开发了一个实验性的面向敏捷制造的企业资源计划软件系统。该系统除具有一般企业资源计划软件的功能外,还能够支持敏捷制造的“机遇驱动”的运作方式、供应链计划、动态联盟的组成与监控、风险利润分配和联盟解体清算等多种功能。为使敏捷企业能够快速灵活响应市场不断变化的需求,并在全球范围内实现制造资源的优化配置,该系统包含伙伴挑选、供应链计划、分销网络设计、风险防范投资等若干优化模型。     

A hybrid approach of ordinal optimization and iterated local search for manufacturing cell formation

One of the fundamental problems in cellular manufacturing is grouping products with similar features into families and associated machines into cells. The objective is to maximize grouping efficacy, which indicates the within-cell machine utilization and the inter-cell movement. In this paper, a novel hybrid approach combining ordinal optimization (OO) and iterated local search (ILS) is presented to solve it in a short time. The hybrid algorithm takes ordinal optimization as the main framework, while ILS is embedded in the framework as a sub-procedure. In each iteration of the algorithm, according to OO strategy, r best solutions are accepted as the initial solutions for the embedded ILS in turn. From each initial solution, H solutions are generated and totally rH “good enough” solutions are obtained. For the ILS algorithm, a very-large scale neighborhood, cyclic transfer neighborhood is adopted, the characteristic of which is several products moving simultaneously in a cyclical manner. A reinforcement kick strategy is also proposed for the ILS algorithm, in which the products and machines are regrouped according to the current grouping relationships between products and machines. Computational experience on a set of group technology problems available in the literature shows the efficiency of the new hybrid algorithm. The results obtained by the hybrid algorithm are comparable to those obtained by other known algorithm in the literature for the problem.     

并行设计的进程模型

并行设计过程建模是对并行设计过程进行规划、监控和管理的基础。本文在引入设计进程这一概念的基础上 ,建立了设计过程的进程模型 ,并给出了相应的形式化表达方法。该模型较好地反映了并行设计过程的渐进性、多视图特征、动态性和可重用性等特征 ,并具有一定的可操作性 ,特别是它基于不同资源的多视图模型使资源冲突的检测变得简单易行。文中以减速器的并行设计为例给出了一系列示例。     

Thermal-error modeling for complex physical systems: the-state-of-arts review

Flexibility and responsiveness to customer demands are very important for success. Generally additional time is needed for setup caused by poor design of equipment. At this point the terms continuous process improvement and SMED (single minute exchange of dies) as an approach of lean manufacturing come into play. A lean manufacturing system is part of corporate culture, like tools and approaches. In this research work, the process capability analysis technique is implemented by using MINITAB14 software to investigate the relation between SMED methodology and equipment design. The index C_pk has been used in this application study to provide a quantitative measurement of the equipment design by applying the SMED methodology in automobile manufacturing. The results of this research study indicated that SMED in other words “quick changeover” is still a suitable method not only for manufacturing improvement but also for equipment/die design development.     

Evaluating the measurement capability of a wheel profile measurement system by using GR&R

Reliable data with less variation play a key role for acceptance of the usefulness of the measurement output of a wheel profile measurement system (WPMS) in a railway network. However, in practice, most studies are carried out without checking the reliability of data from such a system, which may lead to inappropriate maintenance strategies. To ensure the measurement capability of WPMS and to support robust maintenance in railway systems, this study has evaluated measurement data for the flange height, flange thickness, flange slope, and tread hollowing of rolling stock wheels by using gauge repeatability and reproducibility (GR&R). In this study, acceptance and rejection criteria for the precision-to-tolerance ratio (PTR), signal-to-noise ratio (SNR), and discrimination ratio (DR) have been employed to evaluate the measurement capabilities. For the purpose of illustration, we have implemented a new proposed approach. This approach involves both an analysis using graphs with four regions with a confidence interval (CI) of 95% and an analysis using a graph with three regions with only the predicted values; the latter type of graph represents an innovation made in this study. This graph has the advantages that it can visualize three different levels of data quality in same figure, namely “unacceptable”, “acceptable” and “good”, and also include a number of measures without becoming unclear, which are features that have been missing in previous presentations. The results show that the measurements of the flange slope are on an acceptable level, while those for the flange height, flange thickness and tread hollowing have to be rejected as unacceptable. The action proposed for increasing the quality of data on the flange height, flange thickness and tread hollowing is to enhance the calibration of the WPMS. In conclusion, GR&R is a useful tool to evaluate the measurement capability of WPMS and to provide helpful support for maintenance decision making. This investigation also shows that there is good reason to be careful when selecting measures and when interpreting the results, since, for a certain wheel profile parameter, when one measure is used, the results may be acceptable, but when another measure is used, the results may be unacceptable.     

基于“S”形加工样件的复合数控机床几何误差逆向追踪

基于对"S"形加工样件的复合机床误差影响溯源的研究,提出一种辨识影响加工缺陷最大的误差参数的方法。该方法将"S"形样件加工缺陷与复合数控机床成形运动综合考虑,采用三次B样条曲面对"S"形样件加工缺陷进行数学表征,并逆向推导出了"S"形样件加工缺陷处对应的刀具中心的实际位置,求解出了实际加工曲面到机床刀具的映射关系。同时利用多体系统误差分析理论建立了复合机床加工缺陷生成模型,并从机床角度求解出了缺陷处误差的表达方程。接着在"S"形样件缺陷产生的位置处,根据误差参数的敏感度及其实测值计算各项误差参数对加工缺陷的贡献并进行排序,确定对加工缺陷影响较大的5项误差参数。试验结果表明:该5项误差参数和全部误差参数同时作用下各点的误差进行差值比较,发现差值最大不超过±1.5μm,因此ε_(yC_1)、δ_z(B)、ε(C_1)、ε_x(C_1)、ε_(x_1C_1)是对加工缺陷影响较大的5项误差参数。     

铁路场站轨道吊动态配置及其与集卡协同调度

为提高铁路场站集装箱装卸效率和减少轨道吊长距离移动,提出"轨道吊—集卡"协同装卸方案,综合考虑集装箱位置、轨道吊重载与空载操作3个因素,构建轨道吊动态配置及其与集卡协同调度的双层优化模型.上层目标为作业均衡率最大化,解决轨道吊任务动态分配问题;下层目标为最小化作业完工时间,协同调度轨道吊与集卡.针对问题自身特点,结合遗...     

Estimation of bubble size distributions and shapes in two-phase bubble column using image analysis and optical probes

A precise estimation of bubble size distributions and shapes is required to characterize the bubble column fluid dynamics at the “bubble-scale”, and to evaluate the heat and mass transfer rate in bubble column reactors. Image analysis methods can be used to measure the bubble size distributions and shapes; unfortunately, these experimental techniques are limited to resolve bubble clusters and large void fractions, and can not be applied under relevant operating conditions (e.g., high temperature and pressure). On the other hand, needle probes (i.e, optical and conductive probes) can be used to measure bubble sizes in dense bubbly flows and under relevant operating conditions; however, needle probes measure chord length distributions, which should be converted into bubble size distributions by using statistical algorithms. These algorithms rely on correlations—generally obtained for single droplets/bubbles—that predicts the bubble shapes, by relating the bubble equivalent diameter to the bubble aspect ratio. In this paper, we contribute to the existing discussion through an experimental study regarding the bubble sizes and aspect ratio in a large air-water bubble column. The experimental investigation has consisted in gas holdup, image analysis and optical probe measurements. First, the gas holdup measurements have been used to identify the flow regime transition between the homogeneous flow regime and the transition flow regime. Secondly, the homogeneous flow regime has been described at the “bubble-scale”: chord length distributions and bubble size distributions have been obtained by using an optical probe and image analysis, respectively. Based on the experimental data from the image analysis, a correlation between the bubble equivalent diameter and the bubble aspect ratio has been proposed and has been compared with existing correlations. Finally, the chord length distributions have been converted into bubble size distributions using a statistical method, supported by the aspect ratio obtained through image analysis. The proposed approach has been able to estimate correctly the bubble size distributions at the center of the column then near the wall. We have also demonstrated that the correlations used to predicts the bubble shapes are the main point of improvement in the method.