含有并行机器组的串行短生产线的性能分析

文中主要研究含有并行机器组的串行短生产线的生产性能,此生产线含有一个并行机器组及其上下游缓冲区.由概率守恒原理推导出短生产线的概率平衡方程,求得到短生产线的稳态概率,由此计算串行短生产线的性能指标:平均生产率和平均在制品数量.在Matlab平台下分析系统平均生产率与部分系统参数之间的关系.同时,建立短生产线的Petri网模型,采用事件调度法对短生产线进行仿真,将数值结果与仿真结果进行对比分析,说明文中以机器为中心的分析方法的有效性.     

多级CIMS生产线的可靠性分析

本文对带有缓冲区的可修的多级 CIMS 串行生产线的可靠性问题进行了研究.用马氏过程对中间工作站及中间缓冲区的状态进行了分析,得到了生产线的稳态可用度和稳态生产率的解析式,并用一个例子进行了说明.     

考虑缓冲区故障的CIMS生产线可靠性模型

本文对考虑缓冲区故障的多级CIMS生产线的可靠性问题进行了研究,分析了缓冲区故障对生产线运行的影响,求出了系统稳态可用度及稳态生产率,并用一数值例子进行了说明。     

MOHHA求解不可靠生产线多目标缓冲区分配问题

研究含有可失效机器的不可靠串行生产线上缓冲区容量分配问题,以最大化生产线生产率和最小化生产线缓冲区总量为多目标,提出一种多目标混合启发式算法（MOHHA）。采用了离散事件仿真方法,建立生产率与缓冲区容量分配的仿真模型作为算法的评价工具。算法第一步求得生产线最大生产率,并作为目标生产率进一步求解最小化缓冲区总量。通过三组测试算例,与以往研究结果作对比验证了算法的有效性和优越性。     

随机加工参数串行生产线的性能估计

研究加工参数服从一般分布,重复批量加工n种不同工件的随机串行生产线.给出 了一个稳态加工周期的存在性条件,得到稳态加工周期、生产率、机器利用率的上下估界.     

用遗传算法进行串行生产线缓冲器设计

1　引言制造系统生产线的分析、设计及优化问题 ,越来越受到工程专家们的关注 .在各类制造系统中 ,串行生产线制造系统是最简单的也是应用最为普遍的 ,所以近年来关于此类问题的分析方案已有数十种 .但是 ,由于串行生产线问题的状态维数很大 ,各种分析方法都十分复杂 ,计算量大 ,而且都没能对整条生产线状态建立一个清晰的适合优化的表达 .所以 ,现在仍没有一种有效的串行生产线优化算法 .2　生产线分析现有的一些有影响的分析方案 ,有 Buzacott[1 ] ,Hong[2 ] ,Gershinwin[3,4] ,疏松桂 [5]、谭民[6] 等人的算法 ,其中 Buzacott[1 ] 首先…     

有限小批量定制生产伯努利三机器装配系统实时性能分析

通常适用于大批量制造生产系统的稳态分析在过去几十年得到了广泛研究.然而,当生产量较小（例如,定制化有限小批量生产运行）时,暂态在生产过程中可能起到主要作用,稳态分析将变得不再适用.近年来,对有限小批量生产条件下的串行生产线的研究已经有了一些初步成果.与此同时,装配系统,其最终产品往往需要两个或者多个组件,也广泛用于实践生产中.本文中,在有限小批量生产运行的三机装配系统框架下,假设系统具有有限缓冲区容量,并且使用伯努利机器可靠性模型,研究了此类系统的性能评价问题.具体来说,首先推导出评价系统性能的数学模型和解析公式.然后,提出一种基于分解的方法来近似系统实时性能.最后,所提出的算法的准确性通过仿真数值实验进行了验证并通过一个数值实例进行了展示.     

非串行CIMS生产线可靠性建模、分析与综合

采用等效工作站方法,对非串行CIMS生产线可靠性进行了研究,得到了一条缓冲库可 用度的定理,并推导出在稳态情况下,非串行CIMS系统(如装配线和拆卸线)可以转变成串 行系统求解.同时分析出加工过程不丢失工件的充要条件和若干必要条件,绘出一幅PK-K 曲线,可以给出可行解的大致范围,有助于具体问题的求解.     

串行生产线的数学模型及其性能估算

本文利用Cohen等人提出的DEDS的极大代数上线性系统理论,建立了串行生产线的 状态方程.利用这线性模型,得到了系统的稳态运行的有关结果,并估算了参数扰动对系统性 能的影响.     

缓冲区有限的串行生产线的一种代数模型

本文基于有序事件模型研究了串行生产线在有缓冲区约束情况下的建模方法,给出了改进的代数模型,与原模型有相同的方程阶数和状态维数,因而计算量不增加.改进模型中所修改的参数具有明确的物理意义和简明的规律性,可以直接列写,文中附有建模实例予以验证.     

Computing transfer lines performance measures using dynamic programming

The dynamic behavior of a three-stage production transfer line with finite buffers and unreliable machines is modeled as a Markov chain. Performance measures are computed using value iteration dynamic programming with over-relaxation steps and finite element approximation. This approach permits considering larger buffers than is possible when solving directly for the steady-state probabilities.     

Steady-state performance analysis of serial transfer lines subjectto machine and buffer failure

In modern automated production lines, it is common to connect adjacent machines with buffers. Since these buffers are mechanical devices, they are prone to failure. Previous research concerning the steady-state analytical modeling of serial transfer lines assumed that buffers are completely reliable. The paper considers the unreliable buffer and presents a model of the serial transfer line incorporating this concept. A decomposition technique is developed for the general serial transfer line with unreliable buffers, and an algorithm for computing the solution of the model is presented     

Efficient combined immune-decomposition algorithm for optimal buffer allocation in production lines for throughput and profit maximization

Adequate allocation of buffers in transfer lines is crucial to the optimization of line throughput and work in process (WIP) inventory. Their optimal allocation is subject to specific constraints, associated costs, and revenue projections. In this paper, we implement a combined artificial immune system optimization algorithm in conjunction with a decomposition method to optimally allocate buffers in transfer lines. The aim of the buffer allocation problem (BAP) is to achieve optimal system performance under buffers space constraints. Maximizing line throughput does not necessarily achieve maximum profit. In this study the immune decomposition algorithm (IDA) is used to determine optimal buffer allocation for maximum line throughput and maximum line economic profit.Results of extensive series of tests carried out to compare, in production lines with different characteristics, the performances of the proposed method and those of other algorithms are presented.     

Event-based receding horizon control for two-stage multi-product production plants

In this paper a receding horizon control approach for multi-product production plants is presented. Specifically two-stage plants are considered. In the first stage, a set of parallel production lines generates intermediate products from raw materials. In the second stage, the intermediate products are assembled into final products. A set of buffers for the intermediate products connects the production lines and the assembly line thus allowing a continuous production flow.

The focus is on plants where the switch between product types is less frequent than in the assembly line. The latter is mostly dictated by the external demand, while the first one is the main scheduling variable. A systematic event-based control approach using receding horizon control (RHC) techniques is proposed; specifically the production line flow is controlled in order to satisfy the time-varying request from the assembly line while minimizing the intermediate products storage and processing time. Experimental results underline the benefits resulting from the application of the proposed approach to a car engine manufacturing process.     

Approximate analysis of transfer lines with unreliable machines andfinite buffers

The authors present an approximate method for the analysis of transfer lines with unreliable machines and finite buffers. In these systems blocking and starvation, which occur as a consequence of machine failures, are important phenomena. They first consider homogeneous lines, i.e., lines for which all machines have the same processing times. The behavior of the line is approximated by a continuous flow model. They then use a decomposition technique which enables one to decompose the analysis of the line into the analysis of a set of two-machine lines. This leads to a simple and fast algorithm which provides performance parameters such as production rate and average buffer levels. Experimental results show that this approximate technique is very accurate. They then consider the case of transfer lines with machines having different processing times. A simple transformation is introduced which replaces the line by a homogeneous line. This approximate transformation provides good results for a large class of systems     

Decomposition/aggregation-based dynamic programming optimization of partially homogeneous unreliable transfer lines

The general problem of buffers sizing for mean work in process/inventory minimization in a particular class of single part unreliable manufacturing flow lines, subjected to a constant rate of demand for finished parts, is analyzed. Two variants of the problem are considered: buffers sizing for average work in process minimization when there is a fixed requirement on parts availability in the buffer next to last; minimization of an aggregate measure of average work in process and demand backlog when the complete flow line is considered. A fluid model of part production is employed. The production control policies of interest are suboptimal, strictly decentralized, and are unambiguously parameterized by the size of buffer levels. Optimization of policy parameters is based on the analysis of the structural properties of an associated dynamic program. The latter is built around an approximate, flow line decomposition based, buffer levels dependent theoretical expression of the policy performance measure. The nature of the related flow line approximations is discussed and numerical results of the dynamic programming procedure are reported. Scalability of the computations is demonstrated. The numerical results suggest that when parameters are optimal, both a form of flow line balancing and a just in time internal production principle, are in place.     

Control volume based modelling in one space dimension of oscillating, compressible flow in reciprocating machines

We present an approach for modelling unsteady, primarily one-dimensional, compressible flow. The conservation laws for mass, energy, and momentum are applied to a staggered mesh of control volumes and loss mechanisms are included directly as extra terms. Heat transfer, flow friction, and multidimensional effects are calculated using empirical correlations. Transformations of the conservation equations into new variables, artificial dissipation for dissipating acoustic phenomena, and an asymmetric interpolation method for minimising numerical diffusion and non physical temperature oscillations are presented. The capabilities of the approach are illustrated with an example solution and an experimental validation of a Stirling engine model.     

A memetic algorithm for the flexible flow line scheduling problem with processor blocking

This paper introduces an efficient memetic algorithm (MA) combined with a novel local search engine, namely, nested variable neighbourhood search (NVNS), to solve the flexible flow line scheduling problem with processor blocking (FFLB) and without intermediate buffers. A flexible flow line consists of several processing stages in series, with or without intermediate buffers, with each stage having one or more identical parallel processors. The line produces a number of different products, and each product must be processed by at most one processor in each stage. To obtain an optimal solution for this type of complex, large-sized problem in reasonable computational time using traditional approaches and optimization tools is extremely difficult. Our proposed MA employs a new representation, operators, and local search method to solve the above-mentioned problem. The computational results obtained in experiments demonstrate the efficiency of the proposed MA, which is significantly superior to the classical genetic algorithm (CGA) under the same conditions when the population size is increased in the CGA.     

A tight flow control for job-shop fabrication lines with finite buffers

We propose a work-in-process (WIP) estimation flow control method which serves as a countermeasure against the throughput degradation problem caused by the redundant blocking time of conventional flow control. This method is based on a scheduling technique of which the most important features are: 1) breaking down the entire schedule into individual lot schedules; 2) lot scheduling to reduce redundant blocking time; and 3) WIP estimation for contiguous finite buffer scheduling. The method, first, schedules operational lots at each equipment unit in a fabrication line by using our scheduling procedure for contiguous finite buffers to satisfy the limit capacity of the buffers. Next, the method estimates the future WIP at each equipment group based on predetermined schedules for performing operations. Finally, the method improves the operation timings by continuously supplying WIP estimation to the scheduling procedure. In an actual liquid crystal display (LCD) fabrication line simulation, we have confirmed that the proposed WIP estimation method is a promising one from the standpoint of the line throughput which we obtained.     

Performance measurement and lumped parameter modeling of single server flow lines subject to blocking: An effective process time approach

The present paper extends the so-called effective process time (EPT) approach to single server flow lines with finite buffers and blocking. The power of the EPT-approach is that it quantifies variability in workstation process times without the need to identify each of the contributing disturbances, and that it directly provides an algorithm for the actual computation of EPTs. It is shown that EPT-realizations can be simply obtained from arrival and departure times of lots, by using sample path equations. The measured EPTs can be used for bottleneck analysis and for lumped parameter modeling. Simulation experiments show that for lumped parameter modeling of flow lines with finite buffers, in addition to the mean and variance, offset is also a relevant parameter of the process time distribution. A case from the automotive industry illustrates the approach.