可重构制造系统监督控制器的自动重构

提出了基于改进的网重写系统(Improved net rewriting system, INRS)的可重构制造系统(Reconfigurable manufacturing systems, RMS) Petri网监督控制器的自动重构方法, 以快速适应由市场需求变化所引起的制造系统构形的频繁变化. INRS解决了网重写系统存在的问题, 可动态调整给定Petri网模型的结构而不改变其行为属性. 以集合和图的组合形式定义了RMS的构形, 并提出了基于INRS的一类模块化、可重构的Petri网控制器的设计方法. 针对这类Petri网控制器, 提出了基于INRS的自动重构方法. 方法可将RMS构形的变化转变为INRS的图重写规则, 并作用于当前Petri网控制器, 使其快速、自动地重构为所求的新控制器. 所提出的Petri网控制器的设计与重构方法, 均从理论上保证了结果的正确性, 免校验. 仿真研究验证了方法的有效性.     

可重构制造系统重构算法的实例研究

可重构制造系统（RcMS)的模型及其重构算法是可重构制造系统的形式化表示，是研究RcMS优化的理论基础，基于赋时可重构Petri网的可重构制造系统模型（TRPN－RcMS)及其重构算法是RcMS的形式化表示方法之一。文中以实例对RcMS重构算法进行说明和论证。首先假设一个RcMS的实例系统；然后，根据RcMS的当前系统组成及其生成计划生成RcMS当前系统的TRPN－RcMS模型；最后，根据RcMS重构后的系统组成及其生产计划的变化情况，利用RcMS的TRPN－RcMS模型的重构算法，生成重构后的系统的TRPN－RcMS模型。     

π演算的Petri网语义研究

为弥补π演算的固有缺陷．提出一种将π演算映射为Petri网语义的方法．该方法将π演算分为基本单元、顺序、并发、选择和递归等几种基本结构．分别映射为Petri网．然后复合构成复杂的系统．π演算的Petri网语义可形象地描述系统的物理结构和动态行为，可直接从模型网络结构上定性分析系统的性质．最后,利用该方法将移动汽车网络的π演算模型映射为Petri网，验证了方法的有效性．     

可重写Petri网:位置可重写及性质分析

针对Petri网对动态系统重构形式化描述和建模能力的不足,提出了可重写Petri网和位置可重写Petri网的基本概念.分析了位置可重写Petri网保持有界性、保守性、可重复性及活性等性质.给出了位置可重写Petri网保持活性的一个充要条件.证明了共享合成Petri网是位置可重写Petri网的一个实例,建立了退化的位置可重写Petri网模拟共享合成Petri网的算法.所得结果能够为动态重构系统的Petri网形式化建模提供理论方法,为大规模动态分布式系统的形式化验证提供有效途径.     

基于改进的网重写系统途径的可重构制造单元故障恢复

提出了一种用于可重构制造单元故障恢复的策略与方法, 允许故障发生时, 通过对用于正常操作控制的Petri网形式的监督控制器进行局部、临时性的修改, 实现故障的恢复. 首先, 提出改进的网重写系统, 可用于动态改变Petri网模型结构. 然后,提出了基于改进的网重写系统的故障恢复方法, 其中改进的网重写系统用于操作、引导Petri网监督控制器由错误状态进入正确状态. 故障恢复后监督控制器的结构与期望属性维持不变. 最后, 以实例演示了该故障恢复方法的应用, 证实了方法的有效性.     

自动制造系统设计和仿真中的死锁控制

通过对自动制造系统的Pctri网模型的分析．可以揭示出被模拟系统的死锁跟其初始标识和其结构有关。要想消除自动制造系统的死锁异常,可以通过修改Petri网的初始标识或Pctri网的结构来解决。该文结合具体示例,给出了具体的可操作算法并设计出了控制自动制造系统死锁的Petri网模型,从而为自动制造系统的异常处理提供了一条有效途径。     

基于模糊神经Petri网的故障诊断模型

Petri网是对具有产生式规则的故障诊断系统的有力建模工具，但其缺乏较强的学习能力．本文以Petri网的基本定义为基础，结合模糊逻辑和Petri网模型，定义了模糊Petri网模型，在此基础上引入人工神经网络技术，给出了人工神经网络的模糊Petri网表示方法，并针对工程机械故障诊断异步、离散等特点，提出并建立了故障诊断的模糊神经Petri网模型及其改进模型．基于模糊神经Petri网的故障诊断系统结合了Petri网和人工神经网络的优点，经过自学习后同时具有很强的推理能力和自适应能力．     

基于Petri网的PLC系统设计分析与远程监控

Petri网在离散事件的动态仿真中有着广泛的应用,而如何将Petri网应用到离散制造系统中具有重大的价值.以离散制造业中最常见的搬运机械手模型为基础,提出了它的Petri网模型设计方法,并且利用科学的转换方法将Petri网转化为梯形图,应用到在制造业中广泛使用的PLC系统中.利用这种设计方法,不仅能够轻松地将Petri网应用到实践当中,还能够对模型的死锁、生产周期和不变量进行定量的分析,给制造系统进行管理控制、故障诊断和现场监控带来方便.     

基于Petri网的IPv4到IPv6协议转换分析

应用Petri网原理分析IPv4-IPv6协议转换,并结合实际的系统和详细转换流程图,建立Petri网模型。通过此Petri网模型的有界性、可达性及活性等动态特性,证明此转换模型功能和安全上的可行性。     

基于平行Petri网的制造系统调度与控制一体化方法

为了消除制造系统调度层与控制层之间的隔阂, 实现对生产事件快速灵活响应, 本文提出了一种调度与控制一体化的方法. 首先, 定义了一种新型Petri网模型, 即平行Petri网, 从而集成地描述了传感器、执行器、任务和资源信息, 构建制造系统的信息物理系统模型; 其次, 提出了一种从平行Petri网到赋时Petri网的抽象简化方法, 大规模压缩优化调度所需搜索的状态空间; 再次, 定义了策略Petri网以描述最优调度策略. 最后, 给出了平行Petri网与策略Petri网同步执行算法, 使得平行Petri网与物理系统同步执行.     

Modeling of reconfigurable manufacturing systems based on colored timed object-oriented Petri nets

To cope with the rapid change in manufacturing market requirements, reconfigurable manufacturing systems (RMSs) with the feature of reconfigurability, have to be developed. A model that describes the reconfiguring process of a manufacturing system is developed by applying colored timed object-oriented Petri nets. Based on the main difference between configurations of RMSs and flexible manufacturing systems (FMSs), a modular hierarchical structure of RMS is developed. By the object-oriented method, all the object classes in the RMS model are identified. A macro-place is used to model the aggregation of many processes and a macro-transition is used to link all the related macro-places. Macro-places and macro-transitions are connected with arcs to form a Petri net named a macro-level Petri net so that the control logic of RMS is represented. The macro-level Petri net is refined by hierarchical steps, each step describing these macro-places by more detailed sub macro-places until all the macro-places cannot be divided. Then the characteristics of material flow and time constraints in RMS are modeled by applying colored tokens and associated time-delay attributes. This model integrates object-oriented methods, stepwise refinement ideas and Petri nets together. The RMS activities can be encapsulated and modularized by the proposed method, so that RMS can be easily constructed and investigated by the system developers.     

Optimal deadlock avoidance Petri net supervisors for automated manufacturing systems

Deadlock avoidance problems are investigated for automated manufacturing systems with flexible routings. Based on the Petri net models of the systems, this paper proposes, for the first time, the concept of perfect maximal resourcetransition circuits and their saturated states. The concept facilities the development of system liveness characterization and deadlock avoidance Petri net supervisors. Deadlock is characterized as some perfect maximal resource-transition circuits reach their saturated states. For a large class of manufacturing systems, which do not contain center resources, the optimal deadlock avoidance Petri net supervisors are presented. For an general manufacturing system, a method is proposed for reducing the system Petri net model so that the reduced model does not contain center resources and, hence, has optimal deadlock avoidance Petri net supervisor. The controlled reduced Petri net model can then be used as the liveness supervisor of the system.     

Optimal deadlock avoidance Petri net supervisors for automated manufacturing systems

Deadlock avoidance problems are investigated for automated manufacturing systems with flexible routings. Based on the Petri net models of the systems, this paper proposes, for the first time, the concept of perfect maximal resource-transition circuits and their saturated states. The concept facilitates the development of system liveness characterization and deadlock avoidance Petri net supervisors. Deadlock is characterized as some perfect maximal resource-transition circuits reaching their saturated states. For a large class of manufacturing systems, which do not contain center resources, the optimal deadlock avoidance Petri net supervisors are presented. For a general manufacturing system, a method is proposed for reducing the system Petri net model so that the reduced model does not contain center resources and, hence, has optimal deadlock avoidance Petri net supervisor. The controlled reduced Petri net model can then be used as the liveness supervisor of the system.     

On Resource Arc for Petri Net Modelling of Complex Resource Sharing System

PFS-R – Production Flow Schema with Resources – is a novel graphical representation for complex resource sharing discrete production systems proposed in this paper. The PFS-R is an augmented version of the PFS (Production Flow Schema, previously proposed by the authors) which includes correspondences of system resources at each production step. The PFS-R is able to model system structures as well as system behaviours in a more simplified and transparent manner than ordinary Petri net representations. That is, the PFS-R solves an important drawback when actually adopting Petri nets as a design technique for intelligent manufacturing systems. First, the paper introduces the basic elements of PFS-R, and the equivalent transformations of PFS-R model into hybrid nets and Petri nets, taking into account the net conservativeness. Next, examples of discrete production systems to illustrate the effectiveness of PFS-R are presented. In addition, it is shown, using an example, that the correspondence between resources and production steps in the process flow has a tree structure, which is an effective way to evaluate whether or not the objects designed have a well-defined structure.     

离散制造装配系统的活性控制

首次研究离散制造装配系统的活性控制问题.建立了系统的工件加工过程Petri网模型.通过对系统Petri网模型的结构分析,提出了导致系统死锁的两类元素结构及活性特征.对一类离散制造装配系统提出了避免死锁的Petri网控制器,这类控制器容易实现,对系统的限制小,而且使得受控系统仍具Petri网模型.对一般离散制造装配系统提出了保证系统活性的控制策略.     

离散制造装配系统的活性控制1)

首次研究离散制造装配系统的活性控制问题.建立了系统的工件加工过程Petri网模型.通过对系统Petri网模型的结构分析,提出了导致系统死锁的两类元素结构及活性特征.对一类离散制造装配系统提出了避免死锁的Petri网控制器,这类控制器容易实现,对系统的限制小,而且使得受控系统仍具Petri网模型.对一般离散制造装配系统提出了保证系统活性的控制策略.     

基于扩展模糊Petri网的知识推理方法研究

为使模糊Petri网能够描述可变模糊隶属判据下的模糊知识,利用基准变换能较好地表达模糊隶属判据可变情况的特点,基于定性映射和定性基准变换对模糊Petri网进行了扩展,给出了扩展后网模型的形式定义和基本运行机制。通过利用定性映射描述模糊产生式规则,给出了一种新的知识表示模式和推理方法,新方法有利于构建模糊Petri网基于认知的学习机制。结果显示,该网模型具有较强的知识表达能力,适用于处理认知模糊不确定性知识,其推理过程能体现某些认知特性,尤其适用于构建以定性判断为特点的智能系统。     

UML-OOPN集成建模方法及其在柔性制造系统的应用

针对柔性制造系统FMS(Flexible manufacturing system)建模特点,提出了UML-OOPN集成建模方法。该方法是用UML(the Unified Modeling Language)建立柔性制造系统FMS(Flexible manufacturing system)模型,然后将该模型映射为面向对象Petri网OOPN(Object-Oriented Petri Nets)网模型,通过Petri网模型的分析和仿真,其结果可用于修正和改进模型设计。     

Combining flow control techniques with Petri nets methodologies for real-time control of FMS

This paper focuses on the combination of the flow control techniques with Petri net methodologies. The flow control techniques are improved in order to handle multiple routing. A general and unified Petri net formalism is introduced. The integration of the flow control techniques with an interpreter based on this new Petri net formalism is discussed. Results for simulation of a very flexible manufacturing system are provided.