基于多Agent柔性制造单元的生产调度研究

针对基于制造单元的作业车间的生产调度问题进行了研究,结合多代理的智能性、灵活性和遗传算法的智能优化能力,建立基于多智能体的柔性制造单元的作业车间的调度系统模型.然后,提出了集成多智能体和遗传算法的动态调度策略和调度协商机制;最后,应用此方法完成了常规调度和异常调度的仿真算例.结果表明所开发系统可以解决基于加工单元的制造...     

基于新型制造资源组织模型的生产调度系统研究

为了适应航天制造企业对生产调度系统的要求,提出了新型的制造资源组织模型—–基于虚拟制造单元的制造资源组织模型,探讨了此模式的理论思想以及基于此模型构建的生产调度系统.首先构建了基于虚拟制造单元的资源组织模型结构,并给出虚拟制造单元构建的详细过程;然后,建立了基于此制造资源组织模型的生产调度系统模型;最后,通过应用实例表明了该系统能够有效地简化生产调度过程,提高生产效率.     

半导体制造系统仿真调度中的优化方法

基于仿真的调度方法通常需要进行大量的仿真或者采用好的规则以优化调度结果. 本 文建立了以减小平均在制品为优化目标的半导体制造系统的调度模型, 对模型进行分解和简 化. 把结论作为一个调度规则直接应用于仿真调度方法. 由于充分利用了系统全局的状态信 息, 可以有效地减少仿真的次数, 提高了仿真调度的优化能力.     

差分进化算法求解带批处理机的机器人制造单元调度问题

机器人制造单元是智能制造系统的主要载体,研究机器人制造单元的生产调度问题对于提高智能制造系统的生产效率有着重要作用.对此,研究带批处理机的混合流水线机器人制造单元调度问题.首先,针对机器人制造单元与批处理机的生产特性,建立数学优化模型;其次,设计差分进化算法对其进行求解,提出染色体组编码的概念,求解该问题的染色体组由两个染色体构成,第1条染色体确定工件在每个工序选择的机器,第2条染色体确定加工顺序以及机器人的搬运顺序;然后,设计差分变异、交叉以及选择操作;最后,进行数值实验,结果证明,针对带批处理机的机器人制造单元调度问题,差分进化算法能缩短完工时间,得到更好的解.     

柔性制造单元一种多层计划调度方法

柔性制造单元的计划与调度问题已有许多的讨论,但大都针对具体的系统以及对任务做某些假设,本文提出一种多层计划和调度的方法并对每层的功能进行讨论,这种方法的结构可应用于各类单元.同时提出三种机器资源的分配方法.文中给出了仿真结果表明此方法是比较有效的.     

一种柔性路径下的跨单元调度方法

针对单元制造系统(Cellular manufacturing system, CMS)中需要多个单元协作完成的特殊工件, 提出柔性路径下跨作业(Job shop)单元的特殊工件调度方法---基于信息素的方法(Pheromone-based approach, PBA).基于多Agent对单元制造系统建立模型, 提出了冗余单元的概念,建立了多Agent之间的协商机制.同时通过建立Agent联盟, 减少通信量的同时增强系统的鲁棒性和调度优化的全局性.实验结果表明,与常见的组合调度规则相比, 本文提出的方法在5种性能指标上具有显著优势.     

汽车冲压车间生产调度仿真系统的设计

生产调度是冲压车间生产管理的基本内容,通过仿真方法可以优化生产调度,提高生产线的利用率.通过分析某汽车制造企业冲压生产线的工艺流程和调度要求,提出了有关合理假设,以最大化节约时间成本为指导思想,建立了汽车冲压车间生产调度仿真模型.在仿真算法设计原则基础上,详细说明了算法的执行流程.最后简单介绍了系统的功能,并给出一个生产调度实例.实例结果表明该系统能获得合理的调度方案,适用于企业冲压生产线的调度问题.     

知识化制造系统中动态调度的自适应策略研究

针对知识化制造系统中的动态调度问题,结合知识化制造单元的高智能特征,提出了B-Q学习算法．并基于该算法构建了一种自适应调度控制策略．针对知识化制造系统运行过程中系统状态空间较大的特点,通过提取系统状态特征,对系统状态进行合理聚类,有效地降低了系统状态空间的复杂性．根据系统当前所处的瞬时状态．选取不同的调度规则对缓冲区中工件进行有效调度．仿真结果验证了所提出调度控制策略的有效性．     

改进的蚂蚁算法车辆运行调度算法研究

研究车辆调度优化问题,考虑时间能合理安排运输线路.针对传统的蚁群算法收敛速度慢、易陷于局部最优、影响优化调度线路识别等缺陷,提出了一种改进的蚂蚁算法车辆调度优化方法模型.对城市车辆调度建立优化数学模型,将车辆运行调度归并为制造系统中的FLOWSHOP调度问题,构建一种动态开放的车辆调度系统优化模型,并采用改进的蚂蚁算法对数学模型进行仿真.仿真结果表明,提出的新的算法不仅能有效的求解车辆调度优化模型,可以快速得到近似最优解,而且计算机复杂度较低,收敛速度较快,是一种有效地车辆调度优化手段.     

自动化制造单元调度算法综述*

作为未来先进制造系统的重要发展方向,自动化制造单元（robotic cells）在半导体和印刷电路板制造、化学电镀、钢铁冶炼和机械制造等行业获得了日趋广泛的应用。为全面总结自动化制造单元调度算法的研究现状,对自动化制造单元进行分类,在此基础上综述了国内外自动化制造单元调度方法取得的进展及存在的问题,并指明了其进一步的研究方向。     

Stochastic models for performance analysis of multistate flexible manufacturing cells

Performance analysis of flexible manufacturing cells (FMCs) can help companies find the pros and cons of production processes. However, the emphasis has been on issues like cell formation, layout design and scheduling optimization. Little seems to have been done to assess the reliability of an FMC. In this paper, we develop the stochastic models for the performance analysis mainly on the reliability of two different FMCs configured from a set of teaching intelligent flexible manufacturing system (TIFMS). The closed form solutions of probabilities of system states are obtained. Then, utilization rate of equipment in the cell and productivities of the two FMCs as the performance indexes are calculated and optimized. Compared to simulation methods, the closed form solutions make calculations of the performance indexes faster and more accurate. When random variables in the stochastic models are assumed to follow non-exponential distributions, the effects of them on the performance indexes are discussed. The objective of this paper is to fill up the gap that the closed form solutions are difficult to obtain as the number of machine tool increases. Another objective is to optimize the performance indexes to help engineers better evaluate the performance of FMC. Numerical analysis cases are used to illustrate the proposed stochastic models.     

Simulation based optimization of a train maintenance facility

In this paper, a simulation based optimization method is developed for optimization of scheduling policies. This method uses the technique of coupling industrial simulation software with a multi-objective optimizer based on genetic algorithms. It is used to optimize the performances of a railway maintenance facility by choosing the best scheduling policy. Numerical results show that a significant improvement is achieved with respect to the simulation results of the existing system. The method adapted by our problem can be extended to deal with the selection of scheduling rules in using other types of simulation models.     

实时容错调度算法的自动模拟系统模型与设计

实时容错技术是实时系统中的关键技术之一,而实时容错调度算法则是实时容错研究领域中需要重点研究的问题.传统的实时容错调度算法的性能模拟是通过手工完成的,如果采用自动模拟方法,可以提高模拟实验的效率和准确性.首先给出一个实时容错调度算法的自动模拟系统模型,该模型定义了自动模拟系统中的关键参数.然后,提出了实时容错调度自动模拟算法.最后,研究了该自动模拟系统的软件结构.文章研究的自动模拟系统具重要的指导意义,可以参考该系统设计其他类型的调度算法的自动模拟系统.该系统的实现可大大节省用于研究实时容错调度算法的时间和费用.     

Smart shop floor scheduling using knowledge based simulation

In this paper, the need for knowledge-based simulation technique in shop floor scheduling are addressed. A prototype integrated system in Feed Mill manufacturing utilizing an integrated approach of Artificial Intelligence (AI) and simulation is discussed. The system is designed to support the production planner in scheduling and controlling the shop floor on real-time and on-line basis. System overview with the emphasis on knowledge-based simulation module is described.     

分时计算机随机服务系统的模拟

模拟技术可用于构造系统模型以预测系统在给定环境下的性能。本文基于排队系统的系统模拟之原理，提出了一个分时和前－后台优先级调度方式相结合的计算机随机服务系统的系统模型，产研制了模拟软件。     

Embedded simulation on a multiprocessor job scheduling system with inspection

This paper first develops architecture for a multiprocessor job scheduling system with an embedded simulation technique. The architecture provides a shell for applications that are characterized by two scheduling policies, a heuristic algorithm policy and a First-In-First-Out (FIFO) policy. These policies are implemented in the simulation model by using the embedded technique. The paper evaluates these two policies using the queue length, waiting time and flow time as the criteria to compare the performance of these two scheduling policies. Next we designed two simulation situations using two different real world applications. The purpose is to examine the performances of multiprocessor systems with and without inspection operations and two different scheduling policies. The two applications, berth allocation for the container terminal operations and production scheduling arrangement in an Original Equipment Manufacturer (OEM) power supply factory, are studied. The final results show that a proper scheduling policy will perform better than the traditional FIFO approach for a multiprocessor system. Our study also provides guidelines on balancing a system with the addition of a final inspection activity.     

Evaluation of system configuration of FMC for metal cutting

In the FMS of the next generation, the system configuration is to be of modular type, in which the basic module is that of an FMC. In addition, this FMC enables the FMS technology to be avialable for town and medium-size industries. To cope with such trends surrounding the FMC, it is now required to establish a design theory for special-purpose FMC and also a standardization method of FMC. Regarding the latter problem, thus, the similarity evaluation method of the FMC for metal cutting has been investigated to propose a classification method of FMC. The similarity evaluation proposed here puts its main stress on the system configuration, especially on the characteristics of the system component and work flow pattern, and to enable the evaluation procedure to be simplified, the FMC is represented with a directed graph. Through some trial applications, it can be verified that the proposed method is reliable and effective from the practical point of view.     

Deadlock-free scheduling and control of flexible manufacturing cells using automata theory

This paper presents a novel method for the scheduling and control of flexible manufacturing cells (FMCs). The approach employs automata, augmented by time labels proposed herein, for the modeling of machines, transportation devices, buffers, precedence constraints, and part routes. Ramadge-Wonham's supervisory-control theory is then used to synthesize a deadlock-free controller that is also capable of keeping track of time. For a given set of parts to be processed by the cell, A/sup */ search algorithm is subsequently employed using a proposed heuristic function. Three different production configurations are considered: Case 1) each part has a unique route; Case 2) parts may have multiple routes, but same devices in each route; and Case 3) parts may have multiple routes with different devices. The proposed approach yields optimal deadlock-free schedules for the first two cases. For Case 3, our simulations have yielded effective solutions but in practice, optimal deadlock-free schedules may not be obtainable without sacrificing computational time efficiency. One such nontime-efficient method is included in this paper. The proposed approach is illustrated through three typical manufacturing-cell simulation examples; the first adopted from a Petri-net-based scheduling paper, the second adopted from a mathematical-programming-based scheduling paper, and the third, a new example that deals with a more complex FMC scenario where parts have multiple routes for their production. These and other simulations clearly demonstrate the effectiveness of the proposed automata-based scheduling methodology.     

Linking ecological information and radiative transfer models to estimate fuel moisture content in the Mediterranean region of Spain: Solving the ill-posed inverse problem

Live fuel moisture content (FMC) is a key factor required to evaluate fire risk and its operative and accurate estimation is essential for allocating pre-fire resources as a part of fire prevention. This paper presents an operative and accurate procedure to estimate FMC though MODIS (moderate resolution imaging spectrometer) data and simulation models. The new aspects of the method are its consideration of several ecological criteria to parameterize the models and consistently avoid simulating unrealistic spectra which might produce indetermination (ill-posed) problems when inverting the model. The methodology was operatively applicable to 12 shrubland plots located in different provinces of the Mediterranean region of Spain and tested with field data collected in those areas. The results showed that the proposed method efficiently tracks changes of FMC with average errors around 15%. However the model under-estimates FMC values higher than 135.68% since those situations were not included in the simulation scheme and the inversion precision is also dependent on an accurate estimation of LAI. These limitations will be overcome in future work mainly by including spectral signatures of vegetation with FMC values higher than 135.68% in the simulations, and by exploring new methods for LAI retrieval. Further efforts will also be devoted to extend this approach to other ecosystems.     

基于支持向量机的计算资源反馈调度

在实时控制系统(RTCS)中,计算资源一般受限。由于诸多不确定性因素和工作负载的动态变化,系统总是运行在不可预期的开放环境中。为保证系统的稳定运行,提出了一种基于支持向量机(SVM)的计算资源反馈调度方法。它周期性地监测系统计算资源,通过SVM在线预测,得到各个控制回路的下一个采样周期,从而实现系统计算资源的动态分配。通过仿真实验验证了该反馈调度方法的性能,并与理想情况、传统开环调度方法进行了比较,显示了其优越性。