基于赋时Petri 网的化工批处理建模与控制优化

分析了化工批处理过程的特点,以过程设备为核心将整个过程操作划分为若干个子进程,用赋时Ｐｅｔｒｉ网来建立以子进程表示的批处理过程,并提出启发式动态 经自救对过程进行控制。仿真结果表明,基于赋时Ｐｅｔｒｉ网模型与启发式动态 经算法的Ｐｅｔｒｉ网控制器,不仅能准确描述批处理过程的同步、并发及资源工人享关系,而且Ｐｅｔｒｉ网的运行能给出过程生产的最优控制序列。     

化工间歇过程的时间Petri网模型和优化控制

针对化工间歇生产过程的特点及优化问题，本文提出用时间Ｐｅｔｒｉ网对过程建模，用动态规化方法对过程实行优化控制，并研究了该优化策略下的算法和控制设计问题。     

基于Petri网的IC制造调度优化

论文根据IC制造中存在的多制造路径、资源共享、可变晶片组及并发等特点,结合增强定时Petri网,提出了一种调度优化算法。该算法无论是对典型的Job-Shop问题,还是比此更复杂的问题,都能给出确实有效的优化结果,具有一定的通用性。该算法还具有较高的运行效率,文中的实验结果也充分显示了这点。     

Petri网系统活性的研究

随着Petri网在平行计算、通讯系统、计算机集成制造系统等领域的广泛应用,在以Petri网为实际系统建立模型之后,人们很关心模型系统各种性质与行为,其中,活性是最关心的性质之一。我们知道Petri网系统是动态系统的静态描述,从它可以很容易得到系统的状态转换图,一般称Petri网系统的可达图(系统无界时,得覆盖图)。实质上,可达图是动态系统的动态描述;系统有多少种不同状态(不考虑系统无界时),可达图就有多少个结点;结点间由有向弧连结,表明从一种状态转换为另一种状态发生了什么动作(一种或若干     

有界Petri网的可达图到网图的转换算法

本文给出了有界Petri网的可达标识图到网图的转换算法,对算法的正确性与复杂性分别进行了证明和估计,结果表明该算法是一个多项式算法,因而是有效的。     

多处理器调度算法实现及其Petri网建模与仿真

多处理器调度算法在嵌入式实时系统领域中起着关键的作用。根据多处理器的特点,提出一种实时多处理器动态分割并行调度算法SPara。该算法解决了此前多处理器算法,如Myopic、EDPF等仅依据截止期对任务调度产生的问题,实现了增加任务紧迫度限制的调度策略,以及针对执行时间长、截止期紧迫任务的有效调度方法。同时算法结合高级颜色时间Petri网理论进行建模并仿真。测试结果表明,SPara算法在处理器利用率以及调度成功率方面较Myopic等算法有较大提高。     

调度问题的压缩Petri网（RePN）模型研究

本文提出了一种新的Ｐｅｔｒｉ网模型－压缩Ｐｅｔｒｉ网（ＲｅＰＮ）模型，用于调度问题的建模和求解，与以前的模型相比，ＲｅＰＮ模型不仅具有较强的分析能力，而且大大减少了节点数，使可达集杨应减小，从而为搜索调度问题的最优解或近优解提供了方便。     

Petri网与优化算法结合求解FMS调度研究综述

Petri网是基于图形的强有力的建模工具,被用于柔性制造系统调度问题的研究,然而,搜索整个可达树寻找最优调度方案是一个指数倍复杂的问题,由此人们想到利用人工智能算法搜索可达树的一部分获得近优解。该方法被认为是求解调度问题的极具前途的解决方案。从上世纪90年代初期以来,人们对此作了一些卓有成效的研究,对这些研究进行归纳总结,为采用该方法求解调度优化问题的研究提供参考。     

基于Petri网的可达树与可达图的构造与算法实现

Petri网是一种系统设计和分析的工具，为了完成Petri网的各项分析，还需要借助如可达树、可达图等工具。讨论了Petri网可达树与可达图的构造方法，并给出了相应的算法。     

区域排水泵站的优化调度有色Petri网模型

针对城镇排水系统区域泵站调度及其可视化仿真问题,利用模糊控制思想,提出一种以流量进出平衡为基点的区域泵站调度优化策略,依据有色Petri网(CPN)理论,结合排水调度优化过程,建立区域泵站优化调度CPN模型.CPN Tools软件仿真结果表明,该模型动态运行过程符合排水调度控制规律及状态空间分析结果,能实现区域泵站调度...     

基于设备故障的间歇化工过程反应型调度

间歇化工过程生产中的不确定性因素很多,由于其不可预见性和多样性,不可能在产生原调度的同时给出不确定因素的最合适的处理方案,而是需要在不确定因素发生时结合过程的实际情形,来对原调度进行反应型调度.本文考察了设备故障的影响,根据设备故障的特点和所加工物料的性质,分故障产品重加工、故障工序继续加工和故障工序重加工三类加以分析和处理,建立了该问题的数学模型并用遗传算法来对该问题进行求解.文中给出设备故障反应型调度的算例,通过设备的维修时间、物料的处理方式以及故障发生时间对反应型调度的灵敏度分析揭示了基于设备故障的间歇化工过程反应型调度的实质.     

Real-time scheduling of batch systems using Petri nets and linear logic

This paper presents an approach to model, design and verify scenarios of real-time systems used in the scheduling and global coordination of batch systems. The initial requirements of a system specified with sequence diagrams are translated into a single p-time Petri net model representing the global behavior of the system. For the Petri net fragments involved in conflicts, symbolic production and consumption dates assigned to tokens are calculated based on the sequent calculus of linear logic. These dates are then used for off-line conflict resolution within a token player algorithm used for scenario verification of real-time specifications and which can be seen as a simulation tool for UML interaction diagrams.     

Multiobjective scheduling algorithm for flexible manufacturing systems with Petri nets

In this work, we focus on general multi-objective scheduling problems that can be modeled using a Petri net framework. Due to their generality, Petri nets are a useful abstraction that captures multiple characteristics of real-life processes.To provide a general solution procedure for the abstraction, we propose three alternative approaches using an indirect scheme to represent the solution: (1) a genetic algorithm that combines two objectives through a weighted fitness function, (2) a non dominated sorting genetic algorithm (NSGA-II) that explicitly addresses the multi-objective nature of the problem and (3) a multi-objective local search approach that simultaneously explores multiple candidate solutions. These algorithms are tested in an extensive computational experiment showing the applicability of this general framework to obtain quality solutions.     

基于Petri网的批处理调度研究

批处理过程存在于复杂的动态环境中,来自主客观的干扰及问题固有的易变性,会导致各种过程参数的变化,因此,需要研究对意外事件作出快速反应的动态调度方法,以捕捉生产环境的实时变化。该文针对批处理过程中最常出现的操作处理时间波动,提出了基于Petri网仿真技术的批处理过程动态调度方法。仿真结果表明,该方法能有效地改善调度性能,为批处理过程动态调度的研究提供了新思路。     

Dynamic scheduling in flexible assembly system based on timed Petri nets model

This paper investigates a scheduling model for optimal production sequencing in a flexible assembly system. The system features a set of machines working together in the same workspace, with each machine performing a subset of operations. Three constraints are considered: (1) the precedence relation among the operations specified by the assembly tree; (2) working space that limits concurrent operations; and (3) the variation of process time. The objective is to find both a feasible assignment of operations to machines and schedule tasks in order to minimize the completion time for a single product or a batch of products. The assembly process is modeled using timed Petri nets and task scheduling is solved with a dynamic programming algorithm. The method calculates the time required precisely. A detailed case study is discussed to show the effectiveness of the model and algorithm.     

A Reduced Reachability Tree for a Class of Unbounded Petri Nets

As a powerful analysis tool of Petri nets, reachability trees are fundamental for systematically investigating many characteristics such as boundedness, liveness and reversibility. This work proposes a method to generate a reachability tree, called ωRT for short, for a class of unbounded generalized nets called ω-independent nets based on new modified reachability trees (NMRTs). ωRT can effectively decrease the number of nodes by removing duplicate and ω-duplicate nodes in the tree, and verify properties such as reachability, liveness and deadlocks. Two examples are provided to show its superiority over NMRTs in terms of tree size.      

一种监控与调度集成的滚动式算法

给出一种通过滚动调度将动态调度与监控集成的方法，分析了在实际调度中改变调度策略的必要性和可行性，对滚动调度中的滚动窗口进行了描述。仿真实例表明该算法是有效的。