基于赋色Petri网的检测线车辆调度建模与仿真

为了对汽车检测线运行效率进行评估以确保给定数量车辆检测时间最短,通过分析检测过程中的驱动事件和状态演变,采用赋色Petri网建立汽车检测线串行批处理调度模型,包括检测工位的赋色Petri网模型和车辆调度赋色Petri网模型两个层次。通过对检测线调度赋色Petri网模型的仿真获得车辆检测平均耗时、车辆等待队列长度等性能指标,根据仿真运行中的统计数据,在原有先来先服务调度策略基础上,提出复检车辆优先和全检车辆优先调度策略,采用复检车辆优先调度策略的车辆等待队列长度平均缩短了50%,且各工位设备的设备利用率均衡,这表明复检车辆优先调度策略对于改善现有检测线车辆调度性能具有工程应用价值。     

Deadlock prevention using Petri nets and their unfoldings

Unfoldings of Petri nets (PN) provide a method for the analysis of concurrent systems without restoring the state space of a system. This allows one to overcome the state explosion problem. Many properties of the initial PN (boundedness, safety, persistency and hazards) can be checked by constructing the unfolding. A deadlock prevention procedure first detects deadlocks using an unfolding. Then, the first method reduces the unfolding to a set of deadlock-free subunfoldings that cover all live behaviours. The second method uses a direct transformation at the level of the original PN. The methods are implemented as subroutines in the Berkeley program SIS. Although the deadlock detection problem is known to be NP-complete, experimental results show that for highly parallel specifications deadlock prevention by unfoldings is typically more efficient than deadlock prevention based on symbolic BDD (binary decision diagrams) traversal of the corresponding reachability graph.     

Load balanced scheduling and reliability modeling of grid transaction processing system using colored Petri nets

On-demand computing is a popular enterprise model in which the computing resources are made available to the users as needed. On-demand computing based transaction processing system which has grown rapidly in recent years is an information processing system with the stringent requirements of resources to meet the fluctuating demands. Concepts such as grid computing, utility computing, autonomic computing, and adaptive management seem very similar to the concept of on-demand computing. When demands of resources fluctuate, the system needs load balancing for the efficient utilization of the computational resources. Furthermore, scheduling is needed to assign the transactions to the appropriate resources. Thus, modeling of load balanced scheduling along with reliability analysis for this system is a challenging task.This paper presents the load balanced scheduling and reliability modeling in such an environment by using colored Petri nets (CPNs). CPNs which combine Petri nets with programming languages is a powerful modeling technique. The proposed CPN-based modeling pattern formally describes the process of transaction distribution and execution within the on-demand computing environment. Moreover, the CPN-based model uses the hierarchical modeling capability of CPNs, including different levels of abstraction (sub-modules). This helps easily handling and extending the model. Since, on-demand computing based transaction processing system executes a number of concurrent transactions. The CPN-based model is extended to express the concurrency, thus improving the reliability results. This paper takes the example of grid transaction processing (GTP) system with the problem of load balanced scheduling modeling and reliability evaluation.     

基于分层着色Petri网的增强现实装配系统建模

为弥补场景图在增强现实装配应用中的不足,提出一种将层次着色Petri网与图灵机模型结合的方法,建立了增强现实装配环境系统模型。该模型借鉴图灵机的思想,以虚拟手的手势代号及位姿矩阵作为输入,输出具体操作事件更新场景图,记录系统的当前内部状态并根据用户输入给出下一步的操作响应。相对于单一的碰撞检测方法,该方法能更好地满足增强现实装配系统的动态实时响应等性能要求。开发建立了该模型的原型系统,并通过网络状态生成图分析验证了模型实时响应的能力。     

Estimating product development cycle time using Petri nets

Product development has increased importance in business due to stiff competition and a fast changing business environment. Researchers recommend the project management approach but the existing planning tools are limited in application necessitating improved tools. In this paper the application of Petri nets to determine product development time is described and exemplified by a case study.     

有色-时间Petri网航班延误模型与波及分析

基于有色Petri网和时问Petri网理论,给出了单个机场起飞的多架飞机执行航班的有色Petri网模型,建立了多机场多航班有色-时间Petri网模型,提出了航班延误波及分析方法,用于判断当源机场发生航班延误时,从源机场起飞的各个飞机的下游机场是否出现航班延误,并分析和预测延误时间。仿真实验表明,松弛时间越大,越能够有效吸收延误波及;初始延误时间越长,波及下游机场个数越多。     

Modular synthesis of Petri nets for modeling flexible manufacturing systems

This paper proposes a modular Petri net synthesis method for modeling flexible manufacturing systems based on synchronization among control processes of the manufacturing resources (such as robots and machines). In the method, the target system is modeled in a bottom-up and uniform manner by first describing the system's control processes using strongly connected state machines (SCSMs) as the basic modules. Each SCSM may contain multiple tokens to represent resources from the same type such as spaces in a buffer. Next, the common transitions and common transition subnets of the modules are merged to represent their synchronization. The system model constructed is proven to be conservative and thus bounded. Moreover, a restricted class of merged nets is proven to be live and reversible. For general classes of merged nets, this paper shows theorems that easily calculateP-invariants of the final net without solving the linear system equations. TheseP-invariants can be used to help in verifying the model's qualitative properties such as liveness.     

PLC控制系统的Petri网模型研究

运用Petri网方法,给出了PLC控制系统的建模准则,在此基础上,对PLC控制系统进行了性能分析和仿真研究。     

基于Petri网的工作流模式研究

为了满足企业对过程模型描述能力的需求，提出了一个基于Petri网的新工作流模式完全解决方案。在深入研究工作流模式的基础上，应用高级Petri网技术来构造所有的工作流模式。抑制弧通过测零帮助实现多实例的同步，消耗库所负责移除多余的标记，带标记的库所实现对变迁触发序列的控制；设计加权弧和限制容量的库所来实现同步M条路径中被激活的N条的情况。本方案实现了将所有的工作流模式，从基本到复杂，都映射到相应的Petri网上。最后，通过一个集成制造过程模型的实例，说明基于Petri网的方案能够完全满足企业在模型描述能力上的各种复杂需求。     

基于Petri nets的再制造拆卸技术研究

拆卸技术是产品高效回收和再制造的重要前提,是再制造过程中的关键工序,它在很大程度上保证了新产品设计和废旧产品再制造资源的最大化利用。通过对产品拆卸Petri网模型的建立,拆卸序列规划,产品再制造拆卸评估方法的研究,利用Pro/E 4.0系统的客户化开发工具包Pro/Toolkit进行UI对话框设计出了产品再制造拆卸仿真界面,在VS2005中编写动作实现代C语言代码,生成动态链接库执行文件,在Pro/E中注册运行,得到再制造拆卸仿真系统。     

基于柔性制造系统的Petri网模型简化规则

为解决Petri网模型中的状态爆炸问题，提出了一种将简化规则应用到Petri网模型中的方法。该方法通过库所和变迁的合并与消除，来达到简化模型的目的。以柔性制造系统的加工站为例，建立加工站的Petri网模型，将简化规则应用到改进的加工站模型中。为了说明简化网保持了原网的外部功能，利用基于时序Petri网的时态逻辑规则进行了证明。结果显示，简化网在保持功能性的基础上，提高了验证和分析的效率。     

On a maximally permissive deadlock prevention policy for automated manufacturing systems by using resource-oriented Petri nets

It is theoretically and practically significant to synthesize a maximally permissive (optimal) controller to prevent deadlocks in an automated manufacturing system (AMS). With an AMS being modeled with Petri nets, by the existing methods, integer linear programming (ILP) problems are usually formulated and solved to obtain optimal policies by forbidding illegal markings at the same time no legal marking is excluded. Without an efficient technique for solving an ILP, such a method is usually computationally prohibitive. A resource-oriented Petri net (ROPN) is employed to model a class of AMS for resolving the deadlock control problem with maximal permissiveness in this paper. Efficient methods are developed to figure out the key structures in an ROPN model for deadlock prevention. Based on the structural properties of ROPN models, this work explores several types of illegal markings that can be prohibited optimally by structural analysis. For these markings, a deadlock prevention policy can be derived in an algebraic way without solving a notorious ILP problem. For the other markings, linear programming (LP), instead of ILP, approaches are developed to forbid them optimally. Thus, a maximally permissive controller can be developed while the computational cost is reduced greatly. The proposed methods are verified by typical examples in the literature.     

统一建模语言状态图的Petri网模型及其分析方法

针对现有关于统一建模语言状态图形式化语义研究过程中存在的缺点,给出一种统一建模语言状态图的形式化语法表示方法,结合统一网、着色网定义了描述统一建模语言状态图动态语义的Petri网模型状态图网,状态图网可以准确描述状态图中的层间转移、转移的冲突和并发等现象,并且可以描述状态图转移上的数据处理和状态图之间的通讯机制,给出了从统一建模语言状态图到状态图网的转换规则,讨论了基于状态图网验证统一建模语言状态图正确性和一致性的方法.     

An FMS scheduling and control decision support system based on generalised stochastic Petri nets

This paper presents an FMS scheduling and control DSS (decision support system) using generalised stochastic Petri nets (GSPNs) for model representation and analysis. The function of the DSS is to assist the FMS operator to search for suitable control strategies that will achieve efficient performance. It can also be called upon in the event of unforeseen changes in production requirements, component failures, or other related contingencies. The GSPN modelling approach is employed because GSPNs can characterise random processing times, machine breakdown and repair rates. The GSPN employed in the proposed DSS also incorporates dispatching control at conflicting immediate transitions and can be used to determine various performance measures pertaining to scheduling and control. An application example of the DSS for the processing of two part types in a three-machine FMS is also described.     

Modelling,simulation and scheduling of flexible assembly systems with coloured Petri nets

Scheduling in flexible assembly systems is a complicated phenomenon owing to the large variability in the operating parameters. In this paper, coloured Petri nets are shown to be useful in modelling, simulating and scheduling flexible assembly systems. Case studies from published literature are chosen to show its superiority over some of the heuristic and analytical tools. In addition, the tool is also shown to model and analyse systems with some realistic constraints.     

一种新的基于Petri网的分层工作流过程模型

过程模型的描述能力和分析能力难以满足企业的要求,为此,提出了一种新的基于Petri网的分层工作流过程模型。在深入研究各种工作流模型的基础上,通过对基本网进行一定的扩展,给出工作流过程的分层模型。该模型由工作流描述模型和工作流分析模型组成。工作流描述模型直接支持所有工作流模式,特别是多实例、取消、高级同步等高级Petri网无法直接描述的模式。工作流描述模型在Petri网的基础上增加了控制变量,并将变迁划分为变迁入口和变迁体两部分。控制变量与变迁之间构成读写关系。变迁入口函数通过判断控制变量,消解工作流描述模型中的冲突;变迁体函数通过可扩展逻辑描述语句,实现对控制变量的读写操作。工作流分析模型作为工作流描述模型的分析模型,剥离了工作流描述模型个案的语义信息,可以直接利用已有的Petri网分析技术来分析模型。最后,通过几个例子说明了如何使用本文提出的模型对各种复杂流程进行建模和分析。     

基于面向对象Petri网的多Agent系统交互协议建模

为了描述、分析和验证多Agent系统交互协议,提出了一种面向对象Petri网。与现有的形式化方法相比,面向对象Petri网能形象、直观地刻画多Agent系统复杂、并行的交互协议,可以描述其静态和动态语义,并可利用Petri网的数学分析方法对交互协议进行动态分析。面向对象Petri网还具有较好的模块性和柔性,能单独地分析参与交互的每一个Agent,而不会影响其他Agent和环境的状态。最后,利用面向对象Petri网描述了智能物理代理基金会请求协议和合同网协议,并对一个买卖Agent交互实例进行了建模和动态分析,验证了面向对象Petri网具有较好的建模能力。     

面向企业能源消耗过程的模糊Petri网模型研究

针对企业能源消耗系统模型的需求性,在分析企业能源消耗过程的特点和模糊Petri网基本原理的基础上,从实用、可行的角度探索基于模糊Petri网的企业能耗过程模型,详细阐述了面向企业能源消耗过程的模糊Petri网模型的定义和运行规则,并依据特定的建模原则,进行举例说明.模型的建立独立于特定的能源类型和用能设备,全面反映企业能耗过程及其影响因素,为进一步仿真分析企业能耗状况提供了依据.     

基于有色Petri网和分类服务的Web服务组合模型

为更好地集成众多以N层结构开发的遗产资源,提高服务建模的重用性和通用性,提出对面向服务的Web资源分类,并采用有色Petri网研究分类服务的组合建模.在该方法中,以服务目标、资源、状态、数据信息作为描述服务的基本要素,引入控制库所表达外因事件对服务组合的影响,建立了基于基本服务构建组合服务的算法和简化规则,讨论了服务组合Petri网的分析验证方法.最后,应用有色Petri网工具,建立和验证了基于分类服务的电网故障诊断有色Petri网模型.     

基于Petri网的Web服务描述及其可替换性分析

为解决服务组合中的Web服务可替换性问题,在工作流网、开放网等Petri网模型的基础上,提出一种适合面向服务系统的Petri网模型——WS_Net.该模型包含了Web服务的两部分内容:内部流程和外部接口.WS Net可以准确描述顺序、循环、并发、调用、选择五种常见的服务组合方式.在Petri网互模拟等价的基础上定义了WS_Net内网的关于接口变迁的互模拟等价关系,关于接口变迁互模拟等价的WS Net可以实现上下文无关的相互替换并保证替换前后组合服务的行为是一致的.在Petri网化简技术的基础上提出了WS_Net的化简规则,证明了这些化简规则能够保持WS_Net化简前后的接口互模拟等价特性.在实际应用中能够通过化简的方法降低Web服务可替换性分析的复杂度.