面向工艺规划的夹具CAD系统研制

夹具设计是制造工艺设计过程中的一项重要工作。如何进行CAPP与夹具CAD系统的集成是实施工艺设计信息化的关键问题之一。针对成组夹具设计的特点,提出一种CAPP与计算机辅助夹具设计(CAFD)子系统集成的方法,论述建立夹具设计资源库、算法库等有关模块的开发方法与实施技术。     

基于实时碰撞检测的船舶曲面分段人机交互场地布局技术

针对船舶曲面分段的建造具有外形复杂、固定工位、混合场地的生产特点,为满足曲面分段建造规划对空间布局的精细化、可视化、高效化控制需求,提出了基于实时碰撞检测的曲面分段人机交互式场地布局技术。以曲面分段空间布局参数化注入建模为基础,研究了面向动态过程的曲面分段实时碰撞检测算法,实现了人机交互的可视化场地布局,解决了调整位姿、更换场地、更换时间的时空冲突问题;建立了具有结构化、可控化场地布局能力的技术机制。结合实际的工程实例运行分析,验证了技术的合理性与有效性。     

An ant colony-based algorithm for finding the shortest bidirectional path for automated guided vehicles in a block layout

This paper considers the shortest path design problem (SPDP) on bidirectional path topology as one of the best known types of network configurations for automated guided vehicles. An integer linear programming model has been developed to solve the problem. The model intends to minimize the length of the path, which needs to cover all cells at least in one edge. Due to the NP-hardness of the problem, which has been proved previously, this model is only able to solve problems with a small number of cells. So we develop an ant colony system (ACS) algorithm to solve the problem. Comparisons of the designed algorithm with a cutting-plane algorithm show the efficiency of the proposed ACS algorithm for this SPDP.     

考虑避障路径规划的分段建造区域布局优化

为解决分段建造场地布局优化问题,从设施布局角度出发,以分段建造过程中物料运输总物流量最小为目标建立数学模型,综合考虑物料在运输过程中的避障路径求解问题,采用改进的遗传算法对分段建造区域布局进行优化,给出了物料布局方案及各物料规划后的运输路径。通过对某船厂某一分段建造区域布局进行优化,验证了所提方法的有效性和可行性。     

利用精英策略ST-ACO算法对UA-FLP的优化求解

针对制造业中常见的不等面积设施布局优化问题(UA-FLP),提出了一种精英策略蚁群优化算法(ACO)。该算法的主要特点是采用基于切片树(ST)的编码方法,将解分成三部分,即一只蚂蚁代表一个解,它有三部分的信息素;然后结合启发式信息,进行更新寻优,得到最小的物流费用;同时采用比较新颖的边界曲线(BC)回溯方法求出最小物流费用所对应的设施布局尺寸,并确定设施之间最优的输入、输出点(I、O)位置;最后,通过算例对比证明了该方法在解决中小规模实际问题中的有效性及相比于某些现存方法的优越性。     

Three-dimensional surface texture visualization of bone tissue through epifluorescence-based serial block face imaging

Serial block face imaging is a microscopy technique in which the top of a specimen is cut or ground away and a mosaic of images is collected of the newly revealed cross-section. Images collected from each slice are then digitally stacked to achieve 3D images. The development of fully automated image acquisition devices has made serial block face imaging more attractive by greatly reducing labour requirements. The technique is particularly attractive for studies of biological activity within cancellous bone as it has the capability of achieving direct, automated measures of biological and morphological traits and their associations with one another. When used with fluorescence microscopy, serial block face imaging has the potential to achieve 3D images of tissue as well as fluorescent markers of biological activity. Epifluorescence-based serial block face imaging presents a number of unique challenges for visualizing bone specimens due to noise generated by sub-surface signal and local variations in tissue autofluorescence. Here we present techniques for processing serial block face images of trabecular bone using a combination of non-uniform illumination correction, precise tiling of the mosaic in each cross-section, cross-section alignment for vertical stacking, removal of sub-surface signal and segmentation. The resulting techniques allow examination of bone surface texture that will enable 3D quantitative measures of biological processes in cancellous bone biopsies.     

Metaheuristics for fuzzy dynamic facility layout problem with unequal area constraints and closeness ratings

Dynamic facility layout problem deals with the problem of arranging and rearranging the layout plan of a system throughout several periods. In each period, the material handling costs are different from the past period due to the change in the market demand and product mix. In this paper, the uncertainty that exists in transportation values’ forecast is modeled by fuzzy theory. In this paper, departments have unequal areas. This means that in each period, departments can be placed only in certain places due to different spacing requirements. In addition, closeness rating matrix is considered in order to model the goodness of different layout plans with regard to qualitative factors according to decision maker. Accordingly, fuzzy dynamic facility layout problem with unequal areas and closeness rating matrix is considered that aims to minimize the uncertain material handling costs as well as the shifting costs, and maximize closeness rating with regard to space requirements of unequal area departments. A number of fuzzy algorithms are developed in order to deal with the problem. A number of ranking criteria from the literature are implemented in order to compare the performance of the developed algorithms.     

A guide to analysis and reconstruction of serial block face scanning electron microscopy data

Serial block face scanning electron microscopy (SBF‐SEM) is a relatively new technique that allows the acquisition of serially sectioned, imaged and digitally aligned ultrastructural data. There is a wealth of information that can be obtained from the resulting image stacks but this presents a new challenge for researchers – how to computationally analyse and make best use of the large datasets produced. One approach is to reconstruct structures and features of interest in 3D. However, the software programmes can appear overwhelming, time‐consuming and not intuitive for those new to image analysis. There are a limited number of published articles that provide sufficient detail on how to do this type of reconstruction. Therefore, the aim of this paper is to provide a detailed step‐by‐step protocol, accompanied by tutorial videos, for several types of analysis programmes that can be used on raw SBF‐SEM data, although there are more options available than can be covered here. To showcase the programmes, datasets of skeletal muscle from foetal and adult guinea pigs are initially used with procedures subsequently applied to guinea pig cardiac tissue and locust brain. The tissue is processed using the heavy metal protocol developed specifically for SBF‐SEM. Trimmed resin blocks are placed into a Zeiss Sigma SEM incorporating the Gatan 3View and the resulting image stacks are analysed in three different programmes, Fiji, Amira and MIB, using a range of tools available for segmentation. The results from the image analysis comparison show that the analysis tools are often more suited to a particular type of structure. For example, larger structures, such as nuclei and cells, can be segmented using interpolation, which speeds up analysis; single contrast structures, such as the nucleolus, can be segmented using the contrast‐based thresholding tools. Knowing the nature of the tissue and its specific structures (complexity, contrast, if there are distinct membranes, size) will help to determine the best method for reconstruction and thus maximize informative output from valuable tissue.     

基于多智能体由开放式CNC构筑网络制造系统

在分析先进制造系统特点的基础上，给出了一种基于MAS理论的车间网络控制系统模型。讨论了模型中不同智能体的功能与作用。由开放式数控系统和Intranet组成的DCN系统具有硬件成本低、软件开发费用少、性能好等优点。     

某微型轿车踏板布置运动分析

在CATIA中对某微车的踏板进行了布置和运动分析,得出了踏板的运动曲线。根据轿车及其变型车的标准进行了校核,符合国家标准,这为后期优化设计提供了理论数据。     

Optimal layout of a truss for alternative loads

The paper is concerned with the following problem: two alternative loads with the same point of application, A, are to be transmitted to a rigid foundation by a plane truss of minimum weight whose load factors for plastic collapse under one or the other load are not to exceed a given value. A necessary and sufficient condition for global optimality is established and used to determine the optimal layout of the truss.     

Automatic emotional expression of a face robot by using a reactive behavior decision model

This paper introduces a face robot named ‘Buddy’ which can perform facial expressions, such as eye-tracking and lip synchronization, via movements of its facial elements (i.e., eyeballs, eyebrows, eyelids, and lips). Buddy has 14 degrees of freedom. To produce the realistic motion of Buddy, we built a ‘Reactive Behavior Decision Model’ which decides not only how to control the rotation angles and speed of facial elements, but to exhibit as well particular emotions that could express the robot’s personality. Buddy’s personality is formed in the model by the accumulated external stimuli and internal status. The process to automatically achieve reactive behavior in the model is classified into three steps: (1) to analyze the external stimuli and identify variations in Buddy’s internal status; (2) to decide the type and degree of emotion based on the robot’s personality; and (3) to generate specific facial expressions and gestures by combining the appropriate primitive behaviors chosen from emotion databases. By using this model, we have proven that Buddy can display various facial expressions and behaviors, at times very reasonable but quite unexpected.     

Effect of conversion of functional layout to a cellular layout on the queue time performance: some new insights

Transition from a functional system to a cellular system involves partitioning the machine and part populations. Partitioning the machine population degrades the queue time performance. This paper investigates whether splitting the part population into part families can offset the effect of partitioning the machine population on queue time. Queue times are obtained for both cellular and functional systems through queueing theory for single stage production and by simulation for multistage production under identical factor settings of process time, setup time, batch size and part arrival. Unlike past research, this study identifies certain situations where a cellular system without getting benefits in factor settings outperforms a functional system.     

Different approaches for the loop layout problems: a review

In the manufacturing process, loop layout problems (LLPs) are preferred to configurations like single row layout, double row layout, cluster layout, and circular layout for their relative lower initial investment costs because they contain a minimal number of required material links to connect all workstations while providing a high degree of material handling flexibility. The performance of a system is based on the impact of the loop layout. Most of these LLPs are non-polynomial hard. Numerous research works related to loop layout have been published. The literature analysis given here is not restricted to specific considerations about loop layout design. This paper aims to deal with the current and future trends of research on LLPs based on previous research including formulations, solution methodologies. A trend toward bidirectional assumption, large-sized test problems, mixed integer programming, shortcuts instead of additional loop, loading and waiting time for shortcuts, integration of the supply chain management with the data envelopment analysis and also integrate exact, decomposition algorithm with metaheuristics, and developing loop layout using metaheuristics such as scatter search algorithm, improved tabu search, and artificial bees colony algorithm to loop layout is observed. Several research directions are pointed out and discussed.     

Implementing lean manufacturing with cellular layout: a case study

Lean manufacturing is an applied methodology of scientific, objective techniques that cause work tasks in a process to be performed with a minimum of non-value adding activities resulting in greatly reduced wait time, queue time, move time, administrative time, and other delays. In a cellular manufacturing system (CMS), machines are grouped into several cells, where each cell is dedicated to a particular part family and the objective is to maximize cell independence. CMS helps in reducing the material handling, work-in-process, setup time, and manufacturing lead time and improve productivity, operation control, etc. The facility layout used during lean implementation can be either be a line layout or in the form of cells. After grouping parts in to various part families, machine cells can be formed to produce those parts well inside the cells. As some of the lean manufacturing concepts are different from that of cellular manufacturing, e.g., establishment of Takt time, Takt-based resource balancing, etc., some new cell design methodology is required to be explored that is compatible with lean manufacturing. The rate at which work progresses through the factory is called flow rate or Takt. In the present work, a design methodology for cellular layout is proposed for implementing lean concepts and is exemplified in a manufacturing industry dealing with ammunition components for defense applications. Based on Takt time for various parts, the production flow among cells was optimized thus minimizing several non-value added activities/times such as bottlenecking time, waiting time, material handling time, etc. This case study can be useful in developing a more generic approach to design cellular layouts in lean environment.     

Multi-objective optimization in single-row layout design using a genetic algorithm

This paper presents the development of a genetic algorithm for determining a common linear machine sequence for multi-products with different operation sequences and facilities with a limited number of duplicate machine types available for a job. This work aims to minimize the total flow distance traveled by products, reduce the number of machines arranged in the final linear sequence, and decrease the total investment cost of the machines used in the final sequence. We assume that product flow runs only in the forward direction, either via in-sequence or bypass movement. We demonstrate the effectiveness of the proposed algorithm by solving a typical layout design problem taken from literature, and several randomly generated problems. Results indicate that the proposed algorithm serves as a practical decision support tool for resolving layout problems in manufacturing facilities.     

Structural changes in samples cryofixed by contact with a cold metal block

A common method of cryofixation is to bring a specimen rapidly in contact with a cold metal block. It is usually thought that during this process the surface of the specimen suffers little distortion since it freezes rapidly. Whether this is likely depends on the rate at which samples freeze compared with the speed at which the sample hits the cold block. There is some discrepancy between the published experimentally and theoretically determined freezing rates. As a contribution to this debate the distortion in cryofixed, freeze-substituted, striated muscle fibres has been investigated. In transverse sections, compression can be detected by deviations of the filament lattice from the hexagonal and used to estimate the time of freezing. Some specimens were frozen using a Gatan Cryosnapper, which freezes by catching the specimen between two nitrogen-cooled copper jaws. In addition, the speed with which the jaws close has also been determined. The results suggest that freezing of the well-preserved areas occurs in substantially less than 1 ms. This conclusion is supported by results obtained using metal-mirror apparatus in which the cushioned specimen was dropped onto a nitrogen- or helium-cooled copper block. All the specimens frozen against a cold block have a flat edge whereas muscle fibres are round. At the very edge there is evidence of structural damage as well as the more general lattice distortion.