Efficient dispatching rules for dynamic job shop scheduling

This study attempts to provide efficient dispatching rules for dynamic job shop scheduling by combining different dispatching rules. A dispatching rule is used to select the next job to be processed from a set of jobs awaiting service. A job shop will be treated as dynamic, when conditions such as continuously arriving new jobs and deviations from current schedule need to be accommodated, and a job shop should be treated as an integrated part of a manufacturing system. The discussion includes a simulation technique which uses ARENA 4.0. software to simulate the dynamic model of a job shop under various rules and performance measures . Results of the simulation show that, for most of the performance measures, combined rules perform well. In this study, the combined rules MWKR_FIFO and TWKR_SPT do well under most conditions.     

Vehicle dispatching for highly loaded semiconductor production considering bottleneck machines first

Semiconductor wafer fabrication lines can be characterized by re-entrant product flow, long production lead-time, large variety of production processes, and large capital investment. These distinctive characteristics make the flow control in the fab very complicated. Throughput rate and lead-time are among the most important performance measures. The throughput rate is usually determined by a bottleneck resource, and the lead-time depends on the machine utilization level and the amount of variability in the system. Due to the high efficiency of material handling and reduced particles, automated material handling systems such as automatic guided vehicles (AGVs), overhead hoist transporters (OHTs), and overhead shuttles (OHSs) are being widely used in wafer fabrication lines (wafer fabs) instead of human operators. Although a material handling system itself is seldom a bottleneck of production in a fab, it is important for that to effectively support the bottleneck machines to maximize the throughput and reduce production lead-time. This paper presents a vehicle dispatching procedure based on the concept of theory of constraints, in which vehicle dispatching decisions are made to utilize the bottleneck machines at the maximum level. Simulation experiments have been performed to compare the proposed vehicle dispatching procedure with existing ones under different levels of machine utilization, vehicle utilization, and local buffer capacity.     

Evaluation of dispatching rules for cellular manufacturing

In this paper, the effects of various dispatching rules on the operation and performance of cellular manufacturing systems (CMS) are evaluated. When the study of a CMS considers the automated material handling, it is crucial to reduce the gridlock probability (i.e., the probability of an unsuccessful load transfer attempt occurring in the interface point between the intercell and intracell handling system). Preventing an unsuccessful load transfer is critical for the operation of the entire system as a blockage between the automated guided vehicle (AGV) and the overloaded cell results in a total system shutdown. The gridlock probability is influenced by the dispatching rule used to schedule the load transfers in the system. Therefore, in order to reduce this probability it is necessary to use a dispatching rule that will decrease the number of waiting loads in the transfer spurs. The main objective of the paper presented herein is to identify a dispatching rule that maintains the system operational at all times. A group of dispatching rules, including the first come first served (FCFS), shortest imminent operation (SI), longest imminent operation (LI), most remaining operations (MRO), shortest processing time (SPT), shortest remaining process time (SR), and a newly developed rule proposed by the authors, loads with the minimum number of processing first (MNP), are tested and evaluated with respect to whether the capacity of the transfer spurs of the cells is exceeded. This paper presents a simulation model of a cellular manufacturing system, which is used to further explore the effects of the dispatching rules on the system performance. The results show superior performance of the newly proposed MNP rule.     

A neural network for dispatching rule selection in a job shop

This paper investigates an intelligent system that selects dispatching rules to apply locally for each machine in a job shop. Randomly generated problems are scheduled using optimal permutations of three different dispatching rules on five machines. A neural network is then trained to associate between a statistical characterization of the job mix in each of these problems, with the best combination of dispatching rules to use. Once trained, the neural network is able to recommend for new problems a dispatching rule to use on each machine. Two networks are trained separately for minimizing makespan and the mean flowtime in the job shop. Test results show that the combinations of dispatching rules suggested by the trained networks produce better results, for both objectives, than the alternative of using a single rule common to all machines.     

Impact of operation flexibility and dispatching rules on the performance of a flexible manufacturing system

Operation flexibility is one of the eight common types of flexibility that exist in flexible manufacturing systems. Dispatching rules are commonly used in loading the machines. This paper studies the effects of different levels of operation flexibility and various dispatching rules on the performance of a flexible manufacturing system. The system performance considered is mean flow time. Simulation results indicate that the mean flow time cannot be always improved by increasing the level of operation flexibility. Altering the dispatching rules seems to have a more significant effect on the mean flow time performance than changing the level of operation flexibility.     

New dispatching rules for scheduling in a job shop — An experimental study

We present two new dispatching rules for scheduling in a job shop. These rules combine the process-time and work-content in the queue for the next operation on a job, by making use of additive and alternative approaches. An extensive and rigorous simulation study has been carried out to evaluate the performance of the proposed dispatching rules compared with those by the SPT rule, the WINQ rule, a random rule based on the SPT and WINQ rules, and the best existing rule. The important aspects of the results of the experimental investigation are also discussed in detail.     

半导体生产线动态调度方法研究

为了满足半导体生产线多目标优化要求,提出了多目标优化动态调度规则。它由正常状态调度规则、瓶颈设备较低在制品水平的调度规则、非瓶颈设备较高在制品水平的调度规则、多批加工设备调度规则以及紧急工件调度规则五种类型的调度规则组成。使用具有半导体生产线本质特征的简化模型,将多目标优化动态调度规则与先入先出法、最早交货期法、临界值法进行了比较,结果表明,多目标优化动态调度规则能够改善半导体生产线的整体性能,更好地优化模型的生产率、加工周期与在制品水平,最终提高准时交货率。     

模糊制造系统中的不同尺寸工件单机批调度优化

将工件尺寸不同的单机批调度问题扩展到模糊制造系统中,建立了基于模糊批加工时间和模糊批间隔时间的制造跨度模型,提出了一种集成粒子群优化和差异演化的混合算法,将制造跨度最小化.为提高算法的收敛速度,设计了基于工件优先值向量的统一编码方式,并采用线性的缩放因子以确保足够的差异化信息;为解决差异演化算法早熟收敛的问题,将粒子群优化的全局搜索技术嵌入了差异演化算法;最后,在解码时利用批调度的启发式算法,将混合算法的个体加以优化分批.仿真实验结果验证了该混合算法的求解性能优于目前文献中的其他算法.     

生产调度的启发式规则研究综述

启发式规则是求解生产调度问题比较简单有效的方法,与其他生产调度算法相结合,在过去50多年里得到了深入研究和广泛应用。首先综述了国内外对生产调度启发式规则的研究状况,阐述了启发式规则及其分类,介绍了启发式规则性能评价指标和鲁棒性,进一步分析了新提出的启发式规则。在总结启发式算法的基础上,给出了启发式规则应用于智能优化调度算法的一般性框架。最后展望了生产调度启发式规则的进一步研究方向。     

考虑生产能力约束的制造系统双重资源近似优化配置

针对操作工与设备相互间存在复杂的约束关联等问题,基于模具企业典型的模具加工工艺过程,综合考虑人与设备,建立了一种易于求解的线性整数规划数学模型,并运用Lingo得到该模型的最优解.为了验证数学模型的求解结果,根据该类制造系统典型的运作模式,建立了仿真模型,并进行了仿真实验.实验表明:由于模具的实际生产系统受订单到达时间、调度策略、缓存区大小等限制,虽然实际所需的设备及人员的数量比按照所提出的数学模型得到的新增设备及人员数量略多,但是考虑到求解的便利性,数学模型的近似程度可以接受.     

Operation and control of flow manufacturing based on constraints management for high-mix/low-volume production

The existing technology of flow manufacturing, which is mainly appropriate for high volume and repetitive production, is proven difficult to be applied in high-mix/low-volume environments. To adapt lean production into the latter, a new type of flow manufacturing is proposed based on flow path management technology. This paper first describes the general operation framework of the proposed new mode. The main idea is the dynamic formation of adaptable virtual production lines (called flow paths) corresponding to different product families. The application of different theories of constraints/drum-buffer-rope (TOC/DBR) control policies depends on the differences in scope of variety and scale of demand for these product families. The overall architecture of the proposed mechanism of constraint management-based operation and control is introduced. For the implementation, a mathematical programming method is suggested for the dynamic planning of flow paths, and a TOC/DBR ‘path-specific’ mechanism with group scheduling is used for the control over each flow path.We also study other critical issues including the identification and management of resource bottlenecks, and the setting of the buffer size in the deployment of the TOC/DBR mechanism.     

制造网格中资源的层次检索方法研究

分析了传统资源搜索方法应用在制造网格中的局限性，建立了制造网格中资源的信息模型和层次检索模型。在此基础上，提出了一种制造网格中资源的优化检索方法，通过与其他算法比较并结合实例验证了该检索方法的高效性与可行性。     

面向云制造作业车间的机器能力界定方法

针对面向云制造作业车间,研究不同扰动情形下机器保护能力的设置以及参与云服务能力的划分问题。揭示了系统有效产出随机器能力增长变化的规律。提出了能力松弛率和可用调度时间的概念,建立了面向云制造作业车间的机器能力界定模型。设定了不同的非瓶颈能力松弛率和扰动水平,通过对非瓶颈能力的分级利用,得到了非瓶颈松弛率对系统性能的影响曲线。基于聚类算法提出了非瓶颈能力界定方法,给出了不同扰动水平下每台非瓶颈机器的生产能力、保护能力和云服务能力,为企业自制与云服务能力划分与利用提供了决策依据。     

基于仿生原理的网络化制造资源模型定义和应用研究

应用神经元仿生学原理，构建多层结构的制造资源组织模型。通过细胞、逻辑神经和知识网络实现对制造资源信息、面向功能的制造资源组织逻辑和面向制造应用的制造资源应用知识的描述。为制造资源的应用、制造资源检索和用户需求求解以及异地制造资源信息集成提供支持。基于XML定义了制造资源标注语言MRML，研究了基于制造资源模型和制MRML的制造资源应用的相关技术，在上述研究的基础上，实现了制造资源信息的集成、信息挖掘、资源重构、数据重用等制造资源应用。     

基于约束理论的制造单元瓶颈分析及对策

任何系统中都存在制约其发展的约束因素，制造单元设计中的瓶颈问题则影响系统的负荷平衡及生产效率。本文依据约束理论，阐述了对制造单元中的资源瓶颈问题、如何判别MC中瓶颈环节和削减MC瓶颈的方法。瓶颈资源是变化的，贯穿于生产计划调度系统的整个过程，提出了基于TOC和MRPⅡ的集成计划与调度系统框架，其主要特点是考虑了基于约束的单元能力平衡。应用瓶颈管理优化制造单元，对提高制造企业的生产能力具有重要的指导意义。     

Modularized simulation for lot delivery time forecast in automatic material handling systems of 300 mm semiconductor manufacturing

The more accurate the forecast is to lot delivery time, the more effective it is in fab scheduling. In fab operations, scheduling is the major impact factor of tools capacity allocation, tools utilization control and bottleneck management. However, there is no effective method to estimate delivery time in 300 mm automatic material handling systems (AMHS) operation. Computer simulations are authentic, but they are either too complex to model fab operations as well as the whole AMHS, or too time-consuming to simulate with a full-scaled fab model. This paper proposes an analytic methodology to estimate the loop-to-loop delivery time for differentiated lots in a 300 mm AMHS environment. Combining simulation and statistics techniques, we develop a modularized simulation method (MSM) for delivery time forecast of priority lots. Numerical experiments based on data from a local 300 mm manufacturing fab are conducted. Simulation demonstrates that the MSM has credible results in estimating lot delivery times. The time differences between MSM and simulation for both priority lots and regular lots are 0.2 s and 0.1 s, respectively. Using the MSM method to forecast AMHS delivery time is a great contribution for streamlining shop floor operations, such as scheduling and dispatching, for eliminating time delays in the 300 mm automatic environment.     

在多相流变介质参数测量中数据交换的实现方法

本文主要介绍在间接式多相流变介质参数测量中，８０９８多机系统串行通讯的实现方法。在讨论系统结构的基础上，着重说明实现实时数据交换的接口和软件设计的特点。     

新型混合改进遗传算法求解零等待流水车间调度问题

具有零等待约束条件的流水车间调度问题是一类典型的NP难问题,针对该问题提出一种新型混合改进遗传算法进行优化求解.首先,采用改进NEH算法强化初始种群质量,提高种群的多样性.结合关联规则理论挖掘种群中的优势块,借助优势块进行人工染色体组合,以降低问题复杂度.交叉操作采用单段交叉、双段交叉和三段交叉3种交叉机制,改善算法全...     

A recursive algorithm for generating the equations of motion of spatial mechanical systems with application to the five-point suspension

In this paper, a recursive formulation for generating the equations of motion of spatial mechanical systems is presented. The rigid bodies are replaced by a dynamically equivalent constrained system of particles which avoids introducing any rotational coordinates. For the open-chain system, the equations of motion are generated recursively along the serial chains using the concepts of linear and angular momenta. Closed-chain systems are transformed to open-chain systems by cutting suitable kinematic joints and introducing cut-joint constraints. The formulation is used to carry out the dynamic analysis of multi-link five-point suspension. The results of the simulation demonstrate the generality and simplicity of the proposed dynamic formulation.