基于模糊统计的模糊Petri网token确定方法

在模糊Petri网应用研究中,普遍存在模糊token由专家直接给出或主观假定的问题。基于这种情况,提出了通过模糊统计法来获得库所的模糊token,为成功应用模糊Petri网理论创造了条件。给出了计算模糊token的通用形式化算法。实例论证了模糊统计法在求取模糊token时的可行性与有效性。

基于时间Petri网的制造过程模型研究

分析了时间Petri网的激发规则、托肯可用时间和抑制弧等特性,以及制造过程中随机故障的特征。提出不同的时间关联方式对应的多种建模方法,考虑不同的故障发现模式、不同的作业处理策略,建立相应的单机制造过程模型。在此基础上采用模块化和层次化方法可以构建复杂制造过程的时间着色Petri网模型,并可以转换成仿真模型,进一步分析随机机器故障对制造过程性能的影响。

一种模糊petri网仿真工具的设计实现

文章将面向对象思想应用于模糊Petri网仿真工具的设计和实现过程,探讨了模糊Petri网建模与仿真的可视化问题,提出了基于网格可视化技术解决方案及具体实现方法。通过对变速箱的自动建模和诊断仿真实例,证明该系统具有良好的实用性,为模糊Petri网理论的普遍应用提供了工具平台。

面向复杂制造过程质量的模糊Petri网预测及诊断方法研究

在复杂制造过程中，存在质量异常预测及诊断能力弱、智能化程度低、效率低等问题。如何针对制造过程质量问题特点采用合适的预测与诊断方法，满足日益提高的过程自动化水平的要求，是该领域研究人员面临重要的亟待解决的问题。 由于模糊Petri网是模糊集理论与Petri网理论有机结合的一种网络理论，其突出优势在于知识表示、推理和处理模糊信息的能力; 目前，尽管模糊Petri网已有成功的应用案例，但仍存在某些不足，需不断地改进与完善。因此，对模糊Petri网理论方法的研究，有利于提高其知识表示能力、模糊动态推理能力、推理结果可靠性与准确性等，对模糊Petri网理论的广泛应用具有推动作用。 本文以制造过程质量问题的预测与诊断为研究和应用背景，对模糊Petri网预测与诊断方法的研究为主线，以研发的系统为辅助分析工具，重点从方法的层面上对模糊Petri网理论进行了研究和探讨。旨在进一步完善模糊Petri网相关理论，并应用于制造过程质量问题的解决，提高过程的质量监控能力、事故预防能力、缩短故障原因查找周期、提高定位准确性及可靠性奠定方法基础。 针对制造过程质量预测与诊断问题特点，在广泛阅读相关文献并深入探索的基础上，对模糊Petri网理论方法进行了较深入的研究和探讨，重点解决了以下问题： 1）模糊Petri网自动建模方法：对模糊Petri网理论研究的基础和前提是建立模糊Petri网模型。为解决当前模糊Petri网建模效率低、工作量大、易出错等问题，本文提出了模糊Petri网的自动建模方法。该方法的提出，易于保证知识库与模型库更新的同步和一致，提高了建模效率，避免了建模的人为失误。 2) 模糊Petri网参数确定：模型建立后，为实现可靠有效地推理，需进行相关参数的确定。提出了确定模糊Petri网的初始库所token的方法。通过模糊统计的方法来获得模糊token，减少确定token时的主观臆断性和不一致性，为物理量与模糊token的实时转换提供了技术支持。由于构建符合客观实际的、连续的隶属函数是确定模糊token的前提条件，本文提出采用最小二乘拟合来构造模糊隶属函数方法。该方法简单，拟合能力强，人工干预少。由于变迁阈值影响推理的正确性及可靠性，这里对阈值设定进行了初步探讨。阈值设定越高，预测及诊断的漏报率越高；反之，误报率越高。给出了阈值设定的总代价计算式，阈值选择的目标是使总代价最小。 在建立了模糊Petri网模型、确定了相关参数后，便可对异常事件进行预测及诊断推理。 3）模糊Petri网预测方法：对预测模式进行了分类与定义，便于对不同模式下进行预测分析。提出了改进的FPN四种基本推理模型，通过禁止弧的引入，避免了激发过的变迁反复被激发，减少不必要的计算，实现了推理与模型结构的一致性。从而提高了推理效率和基于规则系统的响应能力。 4）模糊Petri网诊断方法：给出了一种模糊Petri网诊断推理方法。该方法充分利用模糊Petri网自身的结构与数学特性这一突出优势，实现了并行推理。以矢量计算方式获得中间库所能力，取代了常规的搜索方式，提高了推理效率。通过引入人机交互的处理策略，减少了模糊Petri网的复杂性及规模。指出在实践中，推理方法的效率、成本及实际的应用效果， 在重要性方面，要远大于方法自身的运算效率。 5）模糊着色Petri网推理方法：在建模复杂大型系统时，为解决模糊Petri网存在模型空间过大，模型数据结构松散等问题，提出了FCPN并行推理方法及FPR与FCPN模型转换算法。提出的FCPN与现有方法的主要区别在以下方面：首先，算法实现变迁的单次激发，避免推理激发变迁的重复计算。其次，某个使能变迁前集库所中token在该变迁激发后并不移除，符合实际推理情况。此外，通过输入/输出关联矩阵计算迭代，实现了并行推理。 最后，以一典型制造过程—埋弧自动焊接过程质量问题的预测和诊断为例，来说明模糊Petri网方法的实际应用。通过系统的实现，验证了相应方法是可行的。通过模糊Petri网的预测及诊断推理，便于实现质量异常的分析、预警、处理、过程控制及数字化管理，为生产策略的调整、纠正措施的采取提供了决策依据，加快了系统响应速度。 本文研究工作重点围绕模糊Petri网理论方法展开，虽以制造过程质量问题的预测与诊断为研究和应用背景，但并不局限于该领域，是属于具有一般性的共性方法。因此，所开展的方法研究工作具有良好的科研价值和广泛的应用前景。

Temporal structure and enablement representation for mutual wills: A Petri net approach

Those temporal formalisms that are sporadically found nowadays in the literature of AI & Law are based on temporal logic. We claim a revived role for another major class of temporal representation: Petri nets. This formalism, popular in computing from the 1970s, had its potential recognized on occasion in the literature of legal computing as well, but apparently the discipline has lost sight of it, and its practitioners on average need be tutored into this kind of representation. Asynchronous, concurrent processes—for which the approach is well‐suited—are found in the legal domain, in disparate contexts. We develop an example for Mutual Wills.

Elementary Petri net inside RFID distributed database (PNRD)

Usually, a Petri net is applied as an RFID model tool. This paper, otherwise, presents another approach to the Petri net concerning RFID systems. This approach, called elementary Petri net inside an RFID distributed database, or PNRD, is the first step to improve RFID and control systems integration, based on a formal data structure to identify and update the product state in real-time process execution, allowing automatic discovery of unexpected events during tag data capture. There are two main features in this approach: to use RFID tags as the object process expected database and last product state identification; and to apply Petri net analysis to automatically update the last product state registry during reader data capture. RFID reader data capture can be viewed, in Petri nets, as a direct analysis of locality for a specific transition that holds in a specific workflow. Following this direction, RFID readers storage Petri net control vector list related to each tag id is expected to be perceived. This paper presents PNRD cornerstones and a PNRD implementation example in software called DEMIS Distributed Environment in Manufacturing Information Systems.

Arquitetura multiprocessada e reconfigurável para a síntese de redes de Petri em hardware

Uma arquitetura reconfigurável e multiprocessada para a implementação física de Redes de Petri foi desenvolvida em VHDL e mapeada sobre um FPGA. Convencionalmente, as Redes de Petri são transformadas em uma linguagem de descrição de hardware no nível de transferências entre registradores e um processo de síntese de alto nível é utilizado para gerar as funções booleanas e tabelas de transição de estado para que se possa, finalmente, mapeá-las num FPGA (Morris et al., 2000) (Soto and Pereira, 2001). A arquitetura proposta possui blocos lógicos reconfiguráveis desenvolvidos exclusivamente para a implementação dos lugares e das transições da rede, não sendo necessária a descrição da rede em níveis de abstração intermediários e nem a utilização de um processo de síntese para realizar o mapeamento da rede na arquitetura. A arquitetura permite o mapeamento de modelos de Redes de Petri com diferenciação entre as marcas e associação de tempo no disparo das transições, sendo composta por um arranjo de processadores reconfiguráveis, cada um dos quais representando o comportamento de uma transição da Rede de Petri a ser mapeada e por um sistema de comunicação, implementado por um conjunto de roteadores que são capazes de enviar pacotes de dados de um processador reconfigurável a outro. A arquitetura proposta foi validada num FPGA de 10.570 elementos lógicos com uma topologia que permitiu a implementação de Redes de Petri de até 9 transições e 36 lugares, atingindo uma latência de 15,4ns e uma vazão de até 17,12GB/s com uma freqüência de operação de 64,58MHz.

A petri net based timing model for hardware/software co-design of digital systems

We have recently proposed an extension to Petri nets in order to be able to directly deal with all aspects of embedded digital systems. This extension is meant to be used as an internal model of our co-design environment. After analyzing relevant related work, and presenting a short introduction to our extension as a background material, we describe the details of the timing model we use in our approach, which is mainly based in Merlin's time model. We conclude the paper by discussing an example of its usage. © 2004 IEEE.

Automatic code generation for microcontrollers from place-transition Petri net models

This paper describes a program for the automatic generation of code for Intel's 8051 microcontroller. The code is generated from a place-transition Petri net specification. Our goal is to minimize programming time. The code generated by our program has been observed to exactly match the net model. It has also been observed that no change is needed to be made to the generated code for its compilation to the target architecture. © 2011 IFAC.

Finding best urban routes based on analyses of high level and IOPT Petri net models

This paper presents a tool that combines two kinds of Petri Net analyses to set the fastest routes to one vehicle in a bounded area of traffic urban. The first analysis consists of the discovery of possible routes in a state space generated from an IOPT Petri net model given the initial marking as the vehicle position. The second analysis receives the routes found in the first analysis and calculates the state equations at incidence matrix created from the High Level Petri net model to define the fastest route for each vehicle that arrive in the roads. It was considered the exchange of information between vehicle and infrastructure (V2I) to get the position and speed of all vehicles and support the analyses. With the results obtained we conclude that is possible optimizing the urban traffic flow if this tool is applied to all vehicles in a bounded urban traffic. © 2012 IEEE.

Ferramentas para a integração de redes de Petri e VHDL na síntese de sistemas digitais

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Comparação de técnicas de redes de Petri na descrição de um pipeline

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Desenvolvimento de uma arquitetura multiprocessada e reconfigurável para a síntese de redes de Petri em hardware

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Extração de casos de teste utilizando Redes de Petri hierárquicas e validação de resultados utilizando OWL.

Este trabalho propõe dois métodos para teste de sistemas de software: o primeiro extrai ideias de teste de um modelo desenvolvido em rede de Petri hierárquica e o segundo valida os resultados após a realização dos testes utilizando um modelo em OWL-S. Estes processos aumentam a qualidade do sistema desenvolvido ao reduzir o risco de uma cobertura insuficiente ou teste incompleto de uma funcionalidade. A primeira técnica apresentada consiste de cinco etapas: i) avaliação do sistema e identificação dos módulos e entidades separáveis, ii) levantamento dos estados e transições, iii) modelagem do sistema (bottom-up), iv) validação do modelo criado avaliando o fluxo de cada funcionalidade e v) extração dos casos de teste usando uma das três coberturas de teste apresentada. O segundo método deve ser aplicado após a realização dos testes e possui cinco passos: i) primeiro constrói-se um modelo em OWL (Web Ontology Language) do sistema contendo todas as informações significativas sobre as regras de negócio da aplicação, identificando as classes, propriedades e axiomas que o regem; ii) em seguida o status inicial antes da execução é representado no modelo através da inserção das instâncias (indivíduos) presentes; iii) após a execução dos casos de testes, a situação do modelo deve ser atualizada inserindo (sem apagar as instâncias já existentes) as instâncias que representam a nova situação da aplicação; iv) próximo passo consiste em utilizar um reasoner para fazer as inferências do modelo OWL verificando se o modelo mantém a consistência, ou seja, se não existem erros na aplicação; v) finalmente, as instâncias do status inicial são comparadas com as instâncias do status final, verificando se os elementos foram alterados, criados ou apagados corretamente. O processo proposto é indicado principalmente para testes funcionais de caixa-preta, mas pode ser facilmente adaptado para testes em caixa branca. Obtiveram-se casos de testes semelhantes aos que seriam obtidos em uma análise manual mantendo a mesma cobertura do sistema. A validação provou-se condizente com os resultados esperados, bem como o modelo ontológico mostrouse bem fácil e intuitivo para aplicar manutenções.

Petri Net Siphon Analysis and Network Centrality Measures for Identifying Combination Therapies in Signaling Pathways

Aberrant behavior of biological signaling pathways has been implicated in diseases such as cancers. Therapies have been developed to target proteins in these networks in the hope of curing the illness or bringing about remission. However, identifying targets for drug inhibition that exhibit good therapeutic index has proven to be challenging since signaling pathways have a large number of components and many interconnections such as feedback, crosstalk, and divergence. Unfortunately, some characteristics of these pathways such as redundancy, feedback, and drug resistance reduce the efficacy of single drug target therapy and necessitate the employment of more than one drug to target multiple nodes in the system. However, choosing multiple targets with high therapeutic index poses more challenges since the combinatorial search space could be huge. To cope with the complexity of these systems, computational tools such as ordinary differential equations have been used to successfully model some of these pathways. Regrettably, for building these models, experimentally-measured initial concentrations of the components and rates of reactions are needed which are difficult to obtain, and in very large networks, they may not be available at the moment. Fortunately, there exist other modeling tools, though not as powerful as ordinary differential equations, which do not need the rates and initial conditions to model signaling pathways. Petri net and graph theory are among these tools. In this thesis, we introduce a methodology based on Petri net siphon analysis and graph network centrality measures for identifying prospective targets for single and multiple drug therapies. In this methodology, first, potential targets are identified in the Petri net model of a signaling pathway using siphon analysis. Then, the graph-theoretic centrality measures are employed to prioritize the candidate targets. Also, an algorithm is developed to check whether the candidate targets are able to disable the intended outputs in the graph model of the system or not. We implement structural and dynamical models of ErbB1-Ras-MAPK pathways and use them to assess and evaluate this methodology. The identified drug-targets, single and multiple, correspond to clinically relevant drugs. Overall, the results suggest that this methodology, using siphons and centrality measures, shows promise in identifying and ranking drugs. Since this methodology only uses the structural information of the signaling pathways and does not need initial conditions and dynamical rates, it can be utilized in larger networks.