共查询到20条相似文献,搜索用时 15 毫秒
1.
2.
3.
从计算机集成制造系统的概念出发,讨论了柔性制造车间在CIMS环境中的地位,介绍了FMS车间控制器的特点和主要功能,讨论了FMS车间内信息要求和计算机网络的结构,以及车间控制系统与其它系统的联系和功能上的协调和互补关系。 相似文献
4.
5.
高级Petri网及FMS的动态建模和仿真 总被引:3,自引:0,他引:3
给出了一种柔性制造系统模型,它能模仿和跟踪车间中散件调度计划的执行过程。模型由一类新的高级Petri网组成,它定义了着色令牌,时化变迁和谓词变迁,抽象了物理对象的主要属性和它们间的基本关联。通过数据库描述令牌属性,规则库描述变迁,构成了一种结构紧凑,信息丰富,可反映多个工作进程的高级Petri网模型。 相似文献
6.
流程制造业生产作业计划模式研究 总被引:1,自引:0,他引:1
生产作业计划的制定在企业中占有重要的地位,MRPⅡ已被广泛应用。本文试图通过一个案例介绍一种在流程制造业更为有效的生产计划模式-过程流计划(PFS)。 相似文献
7.
8.
9.
Macit Araz 《国际生产研究杂志》2013,51(2):563-583
The systematic representation of design concepts is an important requirement for computational support during the conceptual design stage within the process of product development. Behavioural simulation of design concepts is used as a systematic representation framework, and behavioural representation is based on modelling and simulating the behaviour of a design artefact at the conceptual level to perform an overall function, leading to behaviour-based conceptual design. The behaviour-based conceptual design approach is critical for mechatronic systems since they require synergistic integration starting from the initial conceptual design phase. The present study is focused on behavioural representation and simulation of design concepts via discrete event system specification formalism and Petri Nets so as to contribute to systematic conceptual design in mechatronic systems. The paper introduces a representation framework for the behaviour-based conceptual design of mechatronic systems and its implementation on five selected case studies, among laboratory-level educational robots. In addition to Petri Net modelling and computer simulations, the implementation also includes physical simulations of the intended operational behaviours for educational robots on a distributed physical structure called the ‘desktop design model’. In this paper, implementation on one of these case studies, namely the ‘frog robot’, is presented in detail. 相似文献
10.
Lian-Qiao Yang Chi Zhang Wen-Lei Li Guo-He Liu Majiaqi Wu Jin-Qiang Liu Jian-Hua Zhang 《先进制造进展(英文版)》2023,11(2):181-190
Low-temperature silicon nitride (SiNx) films deposited by plasma-enhanced chemical vapor deposition (PECVD) have huge application potential in the flexible display. However, the applicability of SiNx largely depends on the film’s general properties, including flexibility, deposition rate, residual stress, elastic modulus, fracture strain, dielectric constant, refraction index, etc. Process optimization towards specific application by conventional experiment design needs lots of work due to the interaction of muti quality and process parameters. Therefore, an efficient global optimization approach for the process technology was proposed based on the Taguchi orthogonal experiment method considering muti-factor muti-responses. First of all, the Taguchi orthogonal experiment design and analysis was used to rank the influences of main process parameters on the quality characteristics, including radio frequency (RF) power, pressure, silane flow rate, ammonia flow rate and nitrogen flow rate. Then, the global optimization approach was carried out utilizing the multi-response optimizer considering the combination target of film formation rate, residual stress, dielectric constant, elastic modulus, fracture strain, refractive index. Finally, the optimal solution of the SiNx film was finally obtained and verified. The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-022-00423-z 相似文献
11.
Business process modelling has been widely applied by many companies to support the projects such as BPR or enterprize integration. In general, business modelling technique plays the role of pre-designing and evaluating the business flow before the final implementation. However, due to certain improper situations, the developed model might not be appropriate for the final analysis and evaluation. Therefore, model feasibility should be confirmed before the formal evaluation. This research proposed a Petri-net-based approach to evaluate the feasibility of a model defined by BPMN (business process modelling notation). Two kinds of invalid situations, deadlock and infinite loops, will be defined and analysed. There are four phases in the proposed approach. In problem analysis phase, a modified business process development approach would be proposed first. Then, the invalid model would be defined and classification. In the design stage, the developed BPMN model will be transferred to Modified BPEL4WS, which is an XML based language. By applying XSLT and Java, the transferred BPEL4WS will be translated to a Petri-net model specified as CPNXML (Colored Petri-net XML). In the simulation phase, the CPNXML file can be imported into a graphical simulation package CPN Tools for further analysis. Finally, in the implementation phase, the three kinds of property analysis (deadlock, infinite loops and execution time) will be evaluated in terms of the ‘liveness’, ‘reachability’ and ‘consumed time’ of the converted Petri net model. 相似文献
12.
A sub-cycling integration algorithm (or named multi-time-steps integration algorithm), which has been successfully applied to FEM dynamical analysis, was firstly presented by Belytschko et al. (Comput Methods Appl Mech Eng 17/18:259–275, 1979). However, the problem of how to apply this type of algorithm to flexible multi-body dynamics (FMD) problems still lacks investigation up to now. Similar to the region-partitioning method used in FEM, this paper presents a central-difference-based sub-cycling integral method by decomposing the variables of an FMD equation into several groups and adopting different integral step sizes to each group of the variables. Based on the condensed form of an FMD equation, a group of common update formulae and a sub-step update formula, which constitute the sub-cycling together, are established in the paper. Furthermore, an implementation flowchart of the sub-cycling is presented. Stability of the sub-cycling will be analyzed and numerical examples will be performed to verify availability and precision of the sub-cycling in part II of the paper. 相似文献
13.
Numerical stability is an important issue for any integral procedure. Since sub-cycling algorithm has been presented by Belytschko
et al. (Comput Methods Appl Mech Eng 17/18: 259–275, 1979), various kinds of these integral procedures were developed in later
20 years and their stability were widely studied. However, on how to apply the sub-cycling to flexible multi-body dynamics
(FMD) is still a lack of investigation up to now. A particular sub-cycling algorithm for the FMD based on the central difference
method was introduced in detail in part I (Miao et al. in Comp Mech doi: 10.1007/s00466-007-0183-9) of this paper. Adopting
an integral approximation operator method, stability of the presented algorithm is transformed to a generalized eigenvalue
problem in the paper and is discussed by solving the problem later. Numerical examples are performed to verify the availability
and efficiency of the algorithm further. 相似文献
14.
In this work, ITO thin films were deposited onto poly(etherimide) (PEI) substrates at room temperature using r.f. magnetron sputtering and successively they were annealed in the 423-523 K (150-250 °C) temperature range. PEI/ITO substrates were structurally, optically and electrically characterized in order to verify the quality of the deposited ITO films and the PEI thermal stability during the ITO annealing process. A transmittance of about 80% was measured in the visible range. The best electrical properties achieved were: 3.04 × 10− 4 Ω cm, 12.07 × 1021cm2/V.s, 16.8 × 1021 cm− 3, for resistivity, carrier concentration and mobility, respectively. Small molecule Flexible Organic Light Emitting Diodes (FOLED) were then fabricated and characterized onto ITO functionalized PEI substrates. These preliminary results show clearly that PEI can be successfully used as substrate in flexible optoelectronic devices either operating in high temperature or when the process needs high temperatures. 相似文献
15.
Reducing work-in-process (WIP) inventory is continuing to be an important business need because of several factors including the need to reduce working capital. Numerous techniques have been suggested for WIP reduction, and CONWIP is a competitive algorithm for WIP reduction. Prior CONWIP algorithms have been primarily sequential algorithms and can be potentially incur significant computing time, especially when dealing with inventories for multiple products. The paper proposes a card-setting algorithm for multiple product types subject to routing and throughput requirements. The proposed algorithm searches the WIP space iteratively and the step-size is adaptively selected based on the known properties of multi-chain, multi-class, closed queuing networks. Furthermore, parallelization of this search algorithm across multiple processors is proposed where each processor searches a different segment of the WIP space while adaptively adjusting its step size for all product types to ensure fast convergence. The proposed parallel algorithm can take advantage of distributed computing architectures to speed-up the overall computation. An experimental implementation of the parallel algorithm using Message Passing Interface (MPI) over a high-speed network is described. Computational results demonstrate that the proposed parallel algorithm can be parallelized over eight to ten processors to obtain a speed-up of three to five. 相似文献
16.
Cu(In,Ga)Se2 (CIGS) solar cells on aluminum foils offer the advantage to be flexible, lightweight and, because of the low cost substrate, can be used for several applications, especially in buildings, where aluminum is already commonly used. There are reports of a-Si solar cells on Al foil, but to our knowledge development of CIGS solar cells on Al foils has not been reported. We have developed CIGS solar cells on coated Al-foil samples. When using Al as substrate, CIGS layers of suitable structural and opto-electronic properties should be grown at low (< 450 °C) deposition temperatures, because of the difference in the thermo-physical properties of layers and substrates. We have grown CIGS layers by evaporation of elemental Cu, In, Ga, and Se at different substrate temperatures and investigated the properties of these CIGS layers by different methods (SEM, SIMS, and EDX). The photovoltaic properties of small area solar cells were characterized with I-V and quantum efficiency measurements. An efficiency of 6.6% has been achieved. We have also observed that some Al from the foil dissolves during chemical bath deposition (CBD) of CdS. The presence of Al in the bath seems, in some cases, to be beneficial for the electrical properties of the CIGS solar cells. Thinner and more homogenous CdS layers are obtained. Elastic Recoil Detection Analysis (ERDA) and SIMS measurements have shown incorporation of Al in the CdS. 相似文献
17.
It has been reported that radio frequency identification (RFID) technology is applied to manufacturing shop floors for capturing and collecting real-time field data. Real-time information visibility and traceability allows decision makers to make better-informed shop floor decisions. It has been a great challenge to process a huge amount of RFID data into useful information for managerial uses. This paper presents an event-driven shop floor work-in-progress (WIP) management platform for creating a ubiquitous manufacturing (UM) environment. The platform aims to monitor and control dynamic production and material handling through RFID-enabled traceability and visibility of shop floor manufacturing processes. The platform provides facilities to process shop floor real-time RFID events and to aggregate actionable and meaningful operational information to support decision-making activities. An information processing mechanism based on a critical event model is proposed to organise real-time field data in various abstract levels for enterprise decisions. A case study at an air conditioner manufacturing company is used to demonstrate how the proposed platform can benefit its shop floor WIP management by showing how production and logistic operators and their supervisors accomplish their tasks. 相似文献
18.
Directed energy deposition (DED) is a branch of additive manufacturing (AM) processes in which a feedstock material in the form of powder or wire is delivered to a substrate on which an energy source such as laser beam, electron beam, or plasma/electric arc is simultaneously focused, thus forming a small melt pool and continuously depositing material, layer by layer. DED has several unique advantages compared to other AM processes, such as site-specific deposition and repair, alloy design, and three-dimensional printing of complex shapes. Herein, recent advances as well as the main aspects governing laser-material interactions during the DED process, melt pool thermal behavior, advanced in situ monitoring, and interaction mechanisms are critically reviewed. The most critical processing variables and their influence on the deposited material properties, along with defect formation mechanisms and characterization techniques, are also identified and discussed. An overview of high-end applications, current challenges associated with DED processing, and a critical outlook of the technology are presented. 相似文献
19.
协议分布式测试系统的性能模型 总被引:2,自引:0,他引:2
协议测试领域专家们已经达成共识:新一代的协议测试系统应该是分布式架构的。本文用广义随机Petri网(GSPN)对目前提出的几种协议分布式测试框架构造了性能模型,进行了性能比较和分析。为了解决状态空间爆炸的问题,提出了一种同步变迁实施速率等价法(STER),这种方法能够对具有同步变迁的随机Petri网模型分解求解。 相似文献
20.
《Quality Engineering》2012,24(4):567-577
Both the R and S charts are widely used in many manufacturing industries to monitor the process dispersion. The R chart is more popular among quality control practitioners especially when dealing with small sample sizes because of the simplicity of computing the range, R, from each sample. For larger sample sizes, the preferred choice is the S chart because it is slightly more effective than the R chart. The computation of the standard deviation, S, from each sample can now be made easily due to the availability of computers and scientific calculators. This article addresses the shortcomings of the conventional S chart and suggests a modified S chart to overcome these problems. 相似文献