The Relation between the Stabilization Problem for Discrete Event Systems Modeled with Timed Petri Nets via Lyapunov Methods and Max-Plus Algebra

A discrete event system is a dynamical system whose state evolves in time by the occurrence of events at possibly irregular time intervals. Timed Petri nets are a graphical and mathematical modeling tool applicable to discrete event systems in order to represent its states evolution where the timing at which the state changes is taken into consideration. One of the most important performance issues to be considered in a discrete event system is its stability. Lyapunov theory provides the required tools needed to aboard the stability and stabilization problems for discrete event systems modeled with timed Petri nets whose mathematical model is given in terms of difference equations. By proving stability one guarantees a bound on the discrete event systems state dynamics. When the system is unstable, a sufficient condition to stabilize the system is given. It is shown that it is possible to restrict the discrete event systems state space in such a way that boundedness is achieved. However, the restriction is not numerically precisely known. This inconvenience is overcome by considering a specific recurrence equation, in the max-plus algebra, which is assigned to the timed Petri net graphical model.

A modeling method of semiconductor fabrication flows with extended knowledge hybrid Petri nets

A modeling method of extended knowledge hybrid Petri nets(EKHPNs),incorporating object-ori-ented methods into hybrid Petri nets(HPNs),was presented and used for the representation and modelingof semiconductor wafer fabrication flows.To model the discrete and continuous parts of a complex semi-conductor wafer fabrication flow,the HPNs were introduced into the EKHPNs.Object-oriented methodswere combined into the EKHPNs for coping with the complexity of the fabrication flow.Knowledge anno-tations were introduced to solve input and output conflicts of the EKHPNs.Finally,to demonstrate the va-lidity of the EKHPN method,a real semiconductor wafer fabrication case was used to illustrate the model-ing procedure.The modeling results indicate that the proposed method can be used to model a complexsemiconductor wafer fabrication flow expediently.

飞机系统安全性指标的PetriNet分配方法

为解决动态故障树抽象而不利于交流的问题,利用Petri Net直观、易用且适用范围广的优点,提出基于Petri Net的飞机系统安全性指标分配方法。通过整理安全性指标及其相关的可靠性指标,选取失效率作为安全性指标,对比动态故障树及Petri Net建模方法,选取后者建立静态逻辑变迁和动态逻辑变迁的Petri Net指标分配模型。在此基础上,提出考虑严酷等级的系统安全性指标分配方法,经过算例分析,构建Petri Net层次系统故障模型进行指标分配。结果表明,分配值均在相应安全性指标内,该方法能够克服动态故障树法不直观、等分配法分配过于粗糙等缺陷,为飞机安全性设计与评估提供参考。

CCNeter:C程序代码Petri网自动建模工具

CCNeter是实现扩展的Petri网——CNet自动可视化建模的工具,对程序语句从数据、操作和控制3个方面进行描述,刻画了程序代码中数据、操作以及控制之间的关系。它通过解析C工程中文件、函数模块、变量之间的依赖关系,自动形成程序的CNet规范,并根据CNet规范自动进行图形绘制和布局。CCNeter是实现程序静态分析自动化的重要前提。

Modeling of photolithography process in semiconductor wafer fabrication systems using extended hybrid Petri nets

To describe a semiconductor wafer fabrication flow availably, a new modeling method of extended hybrid Petri nets (EHPNs) was proposed. To model the discrete part and continuous part of a complex photolithography process, hybrid Petri nets (HPNs) were introduced. To cope with the complexity of a photolithography process, object-oriented methods such as encapsulation and classifications were integrated with HPN models. EHPN definitions were presented on the basis of HPN models and object-oriented methods. Object-oriented hybrid Petri subnet models were developed for each typical physical object and an EHPN modeling procedure steps were structured. To demonstrate the feasibility and validity of the proposed modeling method, a real wafer photolithography case was used to illustrate the modeling procedure. The modeling results indicate that the EHPNs can deal with the dynamic modeling of a complex photolithography process effectively.

Dynamic properties of fuzzy Petri net model and related analysis

Fuzzy Petri net(FPN) has been extensively applied in industrial fields for knowledge-based systems or systems with uncertainty.Although the applications of FPN are known to be successful,the theoretical research of FPN is still at an initial stage.To pave a way for further study,this work explores related dynamic properties of FPN including reachability,boundedness,safeness,liveness and fairness.The whole methodology is divided into two phases.In the first phase,a comparison between elementary net system(EN_system) and FPN is established to prove that the FPN is an extensive formalism of Petri nets using a backwards-compatible extension method.Next,current research results of dynamic properties are utilized to analyze FPN model.The results illustrate that FPN model is bounded,safe,weak live and fair,and can support theoretical evidences for designing related decomposition algorithm.

模糊Petri网和“后向树”法在陶瓷能耗稳定性中的应用

在生产制造过程中,众多干扰因素会导致企业能耗损失严重,增加成本。提高能耗稳定性是复杂混合制造系统中能效优化的重要模块,在生产过程中快速、准确地找出能源不稳定性影响因素和路径对制造业节能减排具有重大意义。以高能耗中的典型陶瓷行业为例,在分析其生产流程的基础上,研究影响能耗不稳定性的主要影响因素,采用模糊Petri网和“后向树”推理法相结合的方法对能源稳定性进行建模及分析,对能源扰动进行了表示和推理,确定了其扰动的因素和传播路径。并进一步通过陶瓷企业中典型的高能耗烧成车间为例验证了所建模型的可行性和有效性。研究结果为进一步分析和优化能源系统提供参考。

A New Formalism for Modeling a Multi Agent Systems: Agent Petri Nets

In this paper, we present a new formalism for Modeling Multi Agent Systems (MAS). Our model based a PN is able to describe not only not the internal state of each agent modeled but also its behavior. Owing to these features, one can model naturally the dynamic behavior of complex systems and the communication between these entities. For this, we propose mathematical definitions attached to firing transitions. To validate our contribution, we will deal with real examples.

Mapping AADL to Petri Net Tool-Sets Using PNML Framework

Architecture Analysis and Design Language (AADL) has been utilized to specify and verify nonfunctional properties of Real-Time Embedded Systems (RTES) used in critical application systems. Examples of such critical application systems include medical devices, nuclear power plants, aerospace, financial, etc. Using AADL, an engineer is enable to analyze the quality of a system. For example, a developer can perform performance analysis such as end-to-end flow analysis to guarantee that system components have the required resources to meet the timing requirements relevant to their communications. The critical issue related to developing and deploying safety critical systems is how to validate the expected level of quality (e.g., safety, performance, security) and functionalities (capabilities) at design level. Currently, the core AADL is extensively applied to analyze and verify quality of RTES embed in the safety critical applications. The notation lacks the formal semantics needed to reason about the logical properties (e.g., deadlock, livelock, etc.) and capabilities of safety critical systems. The objective of this research is to augment AADL with exiting formal semantics and supporting tools in a manner that these properties can be automatically verified. Toward this goal, we exploit Petri Net Markup Language (PNML), which is a standard acting as the intermediate language between different classes of Petri Nets. Using PNML, we interface AADL with different classes of Petri nets, which support different types of tools and reasoning. The justification for using PNML is that the framework provides a context in which interoperability and exchangeability among different models of a system specified by different types of Petri nets is possible. The contributions of our work include a set of mappings and mapping rules between AADL and PNML. To show the feasibility of our approach, a fragment of RT-Embedded system, namely, Cruise Control System has been used.

Development of a plastic injection molding training system using Petri nets and virtual reality

In this study, Virtual Reality (VR)-based plastic injection molding training system (VPIMTS), which can be modeled as an integrated system with a task planning module, an intelligent instruction module, a simulation module, and virtual envi-ronment (VE) module, was developed. Presented in this paper are an architecture of VPIMTS, a practical knowledge modelling approach for modelling the training scenarios of the system by using Petri nets formalism and key techniques (FEM, injection molding procedure modelling) which have been developed independently. The utilization of the Petri net model realized the environment where the trainee can behave freely, and also made it possible to equip the system with the function of showing the next action of the trainee whenever he wants. The overall system is a powerful approach for highly improving the trainee’s comprehension and injection molding study-efficiency by building digital, intelligent, knowledgeable, and visual aids.

Arteriovenous Shunt Stenosis Evaluation Using a Fractional-Order Fuzzy Petri Net Based Screening System for Long-Term Hemodialysis Patients

This paper proposes the evaluation of arteriovenous shunt (AVS) stenosis using a fractional-order Fuzzy Petri net based screening system for long-term hemodialysis treatment of patients. The screening system uses the Burg method, the fractional-order chaos system, and the Fuzzy Petri net (FPN) for early detection of AVS dysfunction. The Burg method is an autoregressive (AR) model that is used to estimate the frequency spectra of a phonoangiographic signal and to identify the spectral peaks in the region from 25 Hz to 800 Hz. In AVS, the frequency spectrum varies between normal blood flow and turbulent flow. The power spectra demonstrate changes in frequency and amplitude as the degree of stenosis changes. A screening system combining fractional-order chaos system and FPN is used to track the differences in the frequency spectra between the normal and stenosis access. The dynamic errors are indexes that can be used to evaluate the degree of AVS stenosis using a FPN. For 42 long-term follow-up patients, testing results show that the proposed screening system is more efficient in the evaluation of AVS stenosis.

基于逻辑Petri网的循环选择驱动循环结构过程模型修复方法

模型修复是一种过程增强技术。现有模型修复方法较少考虑含间接依赖关系的过程模型,在表示结构间的间接依赖关系时存在不足,修复含循环选择驱动循环结构的模型时难以描述结构间的间接依赖关系。本研究基于逻辑Petri网,针对循环选择驱动循环结构,提出在修复循环选择驱动循环结构的同时可以表达结构间的间接依赖关系的方法。在从日志中获取循环序列和选择序列算法的基础上,通过定理确定模型与日志是否存在偏差并找到偏差位置;根据不同结构提出修复算法修复模型,并使用关联规则描述结构间的间接依赖关系;最后通过实验证明方法的可行性。

一种面向对象的Petri网

柔性制造系统属于离散事件动态系统，具有实时、并发、异步等特性，由于Ｐｅｔｒｉ网模型的图形表述和数学描述，使它既可以采用数学分析，又可以通过图形形象地表述出离散动态系统，故广泛应用于制造过程动态行为建模与分析。而面向对象建模与设计是一种围绕真实世界的概念来组织模型的全新的思考问题方式，面向对象的模型能帮助对问题的理解，有助于同领域专家通讯交流。本文在Ｐｅｔｒｉ网基础上，引入面向对象技术，提出了一种面向对象Ｐｅｔｒｉ网（ＯＰＮ）模型，并以企业中的一项生产活动——二次电源生产过程为实例，建立了描述这一活动系统的完整的ＯＰＮ模型，真实地反映了系统的动态特性。

基于着色随机时间Petri网的维修性建模方法

产品的维修性是决定其维修品质与寿命周期费用的关键因素,维修性建模是维修性设计的重要环节,对产品的维修性水平有重要影响。对维修性建模方法进行深入研究:利用着色随机时间Petri网的库所与颜色标记等基本要素描述维修对象、维修资源等维修实体及其状态,基于库所、颜色标记、随机时间变迁等基本要素给出维修实体状态与维修作业关系以及维修作业逻辑关系的描述方法,并以此为基础构建基于着色随机时间Petri网的维修过程模型。根据该模型提出基于蒙特卡罗法的维修时间仿真算法以及维修资源需求量计算方法。结合某型飞机前起落架系统给出维修过程建模与维修时间仿真、维修资源需求量计算实例,表明模型与方法的优越性。

一种基于Petri网的RFID事件检测的形式化方法

无线射频识别(RFID)采用唯一的电子标签识别物理对象,可高速收集大量目标数据.为向各类应用提供语义信息,RFID系统需从收集的数据中检测用户自定义的复合事件.通过提出一种基于Petri网的RFID事件检测方法,引入形式化的ED-net模型描述复合事件语义,并以此为基础实现一种事件检测方法.ED-net模型是对传统Petri网的一种扩展,提供了描述用户自定义类型、函数及表达式的能力,可精确描述RFID复合事件的属性及时域、非时域、参数化等约束条件.通过对RFID事件形式化描述,各种RFID事件可以统一在ED-net模型,并可自动化进行检测处理,避免了不同复合事件间公共子事件重复检测的问题.最后,经过实验测试和分析,验证了该形式化方法的有效性及其优势.

产品开发ProA一般Petri网模型研究

为了定量描述产品开发ProA的内部运行过程,更好地支持产品开发管理,构建了产品开发ProA的一般模型。深入剖析了产品开发ProA的内部运行机理;利用多色集合的着色原理对Petri网进行改进,形成了多色ProA Petri网方法。在此基础上,建立了产品开发ProA的一般Petri网模型。最后,给出了该模型在汽车油泵单向阀测试器开发中的应用情况。

时间Petri网模拟能力的研究

模型的模拟能力一直是系统建模方面的一个重要研究课题。本文先用一个直观的“零检验”例子说明时间Petri 网的模拟能力比传统 Petri 网要强,并首次证明了时间 Petri 网与计算科学的最高模型——图灵机有相等的模拟能力;最后给出了另外一种含时间因素的时延 Perri 网向时间 Petri 网的转换方法,这说明了时间 Petri 网虽然形式上较为简单,但其模拟能力却并不比其它合时间因素的 Petri 网逊色,同时为时延 Petri 网的研究提供了另外一种有效方法。

基于Petri网模型的收获机轴流式脱分选装置参数化设计

为实现设计的快速化和规范化,进行了基于喂入量变化的联合收获机轴流式脱分选装置的参数化设计研究。通过建立喂入量与相关设计参数的数学模型,获得可用于参数化设计的各个参数。在分析参数之间层次关系和依赖关系的基础上,利用Petri网模型、通过参数传递构建了简化设计的计算机模型并开发了设计平台。应用结果表明:当在程序界面中输入喂入量并选择相关数据后,能自动生成各种所需的结构参数(栅格式凹板包围面积、清选筛面积、脱粒滚筒齿数)以及工作参数(风量、功率);将某部件所得结构参数输入UG环境平台,可获得该部件的三维设计图样。经与现有成熟机型脱分选装置结构参数和工作参数比较可知,计算机模型生成的设计参数和工作参数规范,获得的三维图样符合设计要求。参数化设计平台不但可以进行脱分选装置的规范化设计、提高设计效率,还可以快速判别、修正现有机型脱分选装置的设计参数。

Petri网络理论在电网故障诊断中的应用

论述了基于Petri网络理论进行电网故障诊断的方法,描述了故障元件、保护、开关之间内在的动作关系,提出了运用简单的矩阵计算进行诊断的方法,与传统的专家系统相比,大大减少了诊断时间,提高了准确度,适用于各种网络拓扑.网络测试表明:该方法快速、准确,适于在线运行.

基于模糊有色Petri网的不确定性学习和推理方法

模糊Petri网模型可以用于模糊推理,但在Petri网中不得不用独立子网表示所有类型的过程,即使这些过程具有相同的行为,这导致整个Petri网变得很大。文中提出基于模糊有色Petri网的不确定性推理方法和基于遗传算法的学习过程。在减少网络规模,计算时间和克服解释网络困难的同时,它能保持等量的信息,提供结构化的表示,使知识库中的规则之间的关系易于表示。