A distributed approach for fault detection and diagnosis based on Time Petri Nets

This paper proposes an algorithm for the model based design of a distributed protocol for fault detection and diagnosis for very large systems. The overall process is modeled as different Time Petri Net (TPN) models (each one modeling a local process) that interact with each other via guarded transitions that becomes enabled only when certain conditions (expressed as predicates over the marking of some places) are satisfied (the guard is true). In order to use this broad class of time DES models for fault detection and diagnosis we derive in this paper the timing analysis of the TPN models with guarded transitions. In this paper we also extend the modeling capability of the faults calling some transitions faulty when operations they represent take more or less time than a prescribed time interval corresponding to their normal execution. We consider here that different local agents receive local observation as well as messages from neighboring agents. Each agent estimates the state of the part of the overall process for which it has model and from which it observes events by reconciling observations with model based predictions. We design algorithms that use limited information exchange between agents and that can quickly decide “questions” about “whether and where a fault occurred?” and “whether or not some components of the local processes have operated correctly?”. The algorithms we derive allow each local agent to generate a preliminary diagnosis prior to any communication and we show that after communicating the agents we design recover the global diagnosis that a centralized agent would have derived. The algorithms are component oriented leading to efficiency in computation.     

联锁逻辑模型的安全性分析

故障树分析法(FTA)用于静态分析系统失效的可能事件和状态,是分析安全苛求系统的可靠性和安全性的一种有效方法。时间Petri网(TPN)描述具有时序关系的并发系统,用于系统行为的动态建模。但利用时间Petri网无法严格证明其模型是安全的。提出了一种用于时间Petri网模型的安全性分析方法,该方法有效地结合故障树分析法和时间Petri网的各自优点,实际应用于联锁逻辑模型的安全性分析,并对不安全的模型提出修正方案。     

扩展时段时序逻辑的推理机制

该文在扩展时段时序逻辑的基础上提出了一种推理机制，这种推理机制基于时间Petri网模型及基本不等式规则，可由一组已知的扩展时段时序关系推出一些未知的扩展时段时序关系，对不确定时间段内发生的事件及其相互关系具有较好的描述能力，这种推理机制的优势在于定性地对扩展时段之间的时序关系进行推理分析，利用时间Petri网模型，可以对复杂时序逻辑关系进行化简，比单纯利用不等式规则的推理更直观，也更简单，是一种行之有效的方法。     

扩展时段时序逻辑的模型、一致性和推理

给出了扩展时段时序逻辑的时间Petri网（TPN）模型构造方法，在构造模型的同时对时序关系进行一致性检验，在模型的基础上提出了一种时序关系推理算法，这种推理算法基于TPN模型的性质及基本不等式规则，可由一组已知的扩展时段时序关系推出一些未知的扩展时段时序关系，这种推广理算法的优势在于利用了TNP模型的分析技术，减小了推理的时间复杂度比单纯利用不等式规则的推理更直观，也更简单，是一种有效的方法，最后，对扩展时段时序逻辑的TPN模型进行了扩充，增强了其模型和分析的能力。     

Coding Mobile Synchronizing Petri Nets into Rewriting Logic

Mobile Synchronizing Petri Nets (MSPN's) are a model for mobility and coordination based on coloured Petri Nets, in which systems are composed of a collection of (possibly mobile) hardware devices and mobile agents, both modelled homogenously. In this paper we approach their verification, for which we have chosen to code MSPN's into rewriting logic. In order to obtain a representation of MSPN systems by means of a rewrite theory, we develop a class of them, that we call ν-Abstract Petri nets (ν-APN's), which are easily representable in that framework. Moreover, the obtained representation provides a local mechanism for fresh name generation. Then we prove that, even if ν-APN's are a particular class of MSPN systems, they are strong enough to capture the behaviour of any MSPN system. We have chosen Maude to implement ν-APN's, as well as the translation from MSPN's to ν-APN's, for which we make intensive use of its reflective features.     

Discovering simulation models

Process mining is a tool to extract non-trivial and useful information from process execution logs. These so-called event logs (also called audit trails, or transaction logs) are the starting point for various discovery and analysis techniques that help to gain insight into certain characteristics of the process. In this paper we use a combination of process mining techniques to discover multiple perspectives (namely, the control-flow, data, performance, and resource perspective) of the process from historic data, and we integrate them into a comprehensive simulation model. This simulation model is represented as a colored Petri net (CPN) and can be used to analyze the process, e.g., evaluate the performance of different alternative designs. The discovery of simulation models is explained using a running example. Moreover, the approach has been applied in two case studies; the workflows in two different municipalities in the Netherlands have been analyzed using a combination of process mining and simulation. Furthermore, the quality of the CPN models generated for the running example and the two case studies has been evaluated by comparing the original logs with the logs of the generated models.     

Extended Petri net-based modeling,analysis and simulation of an intelligent materials handling system

This paper describes, models, analyzes and simulates an intelligent materials handling system with diagnostic intelligence capabilities using Extended Petri Nets (EPNs). The important modeled system properties of safeness, liveness and reversibility, which guarantee that the system operates in a stable, deadlock free and cyclic manner are verified and illustrated through the simulation results, obtained through an EPN based software package. A real system, the USL CIM system, modified to function as an intelligent materials handling system with on-line adaptation capabilities is used as a case study.This work has been partially supported by the LEQSF Research Grant LEQSF (91–93) — RD-A-40. A short version of this paper has been presented at the 31st IEEE CDC, Tucson, Arizona, December 1992.     

Petri net modules in the transformation-based component framework

Component-based software engineering needs to be backed by thorough formal concepts and modeling techniques. This paper combines two concepts introduced independently by the two authors in previous papers. On one hand, the concept of Petri net modules introduced at IDPT 2002 in Padberg [J. Padberg, Petri net modules, Journal on Integrated Design and Process Technology 6 (4) (2002) 105–120], and on the other hand a generic component framework for system modeling introduced at FASE 2002 in Ehrig et al. [H. Ehrig, F. Orejas, B. Braatz, M. Klein, M. Piirainen, A generic component concept for system modeling, in: Proceedings of FASE ’02, Lecture Notes in Computer Science, vol. 2306, Springer, 2002]. First we develop a categorical formalization of the transformation based approach to components that is based on pushouts. This is the frame in which we show that Petri net modules can be considered as an instantiation of the generic component framework. This allows applying the transformation based semantics and compositionality result of the generic framework to Petri net modules. In addition to general Petri net modules we introduce Petri net modules preserving safety properties which can be considered as another instantiation of pushout based formalization of the generic framework.     

Decidability results in First–Order Hybrid Petri Nets

In this paper we tackle the decidabilityof marking reachability for a hybrid formalism based on Petrinets. The model we consider is the untimed version of First–OrderHybrid Petri Nets: it combines a discrete Petri net and a continuousPetri net, the latter being a fluid version of a usual discretePetri net. It is suggested that the decidability results shouldbe pursued exploiting a hierarchy of models as it has been donein the framework of Hybrid Automata. In this paper we definethe class of Single–Rate Hybrid Petri Nets: the continuousdynamics of these nets is such that the vector of the markingderivatives of the continuous places is constant but for a scalarfactor. This class of nets can be seen as the counterpart oftimed automata with skewed clocks. We prove that the reachabilityproblem for this class can be reduced to the reachability problemof an equivalent discrete net and thus it is decidable.     

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.     

Modeling and scheduling of ratio-driven FMS using unfolding time Petri nets

In this paper, we focus on the analysis of a cyclic schedule for the determination of the optimal cycle time and minimization of the Work in Process (WIP for short). Especially, this paper deals with product ratio-driven FMS cyclic scheduling problem with each other products and ratios using Timed Petri nets unfolding (TPN for short). TPN slicing and unfolding are applied to analyze this FMS model. We can divide original system into subsystem using TPN slices and change iterated cycle module into acyclic module without any loss of other behavior properties.     

Distributed simulation of modular time Petri nets: An approach and a case study exploiting temporal uncertainty

This paper proposes an approach to modular modelling and simulation of complex time-critical systems. The modelling language is represented by Merlin and Farber’s Time Petri Nets (TPNs) augmented with inhibitor arcs and modular constructs borrowed from the Petri Net Markup Language (PNML) interchange format. Analysis techniques depend on Temporal Uncertainty Time Warp (TUTW), a time warp algorithm capable of exploiting temporal uncertainty in general optimistic simulations over a networked context. A key feature of the approach is the fact that TPN models naturally exhibit a certain degree of temporal uncertainty which the TUTW control engine can exploit to achieve good speedup without a loss in the accuracy of the simulation results. The developed TUTW/TPN kernel is demonstrated by modelling and simulation of a real-time system example.A preliminary version of this paper was presented at 38th SCS Annual Simulation Symposium, April 4–6, 2005, San Diego (CA), IEEE Computer Society, pp. 233–240. Franco Cicirelli achieved a PhD in computer science from the University of Calabria (Unical), DEIS—department of electronics informatics and systems science. As a postdoc, he is making research on agent and service paradigms for the development of distributed systems, parallel simulation, Petri nets, distributed measurement systems. He holds a membership with ACM. Angelo Furfaro, PhD, is a computer science assistant professor at Unical, DEIS, teaching object-oriented programming. His research interests are centred on: multi-agent systems, modeling and analysis of time-dependent systems, Petri nets, parallel simulation, verification of real-time systems, distributed measurement systems. He is a member of ACM. Libero Nigro is a full professor of computer science at Unical, DEIS, where he teaches object-oriented programming, software engineering and real-time systems courses. He directs the Software Engineering Laboratory (www.lis.deis.unical.it). His current research interests include: software engineering of time-dependent and distributed systems, real-time systems, Petri nets, modeling and parallel simulation of complex systems, distributed measurement systems. Prof. Nigro is a member of ACM and IEEE.     

A Petri net model for integrated process and job shop production planning

In this paper a new Petri net class (Chameleon systems) for modeling and analyzing joined process planning and job shop production planning is proposed based on the multi-level Petri net model introduced by Valk (1995). Chameleon system is a High-level Petri net extended with time that consists of a High-level Petri net modeling the workshop which is called system net and ordinary Petri net modeling the jobs and setups which act as tokens of the system net and therefore are called token nets. Process plans of the jobs are partial orders of operation groups and alternatives. The uncertainty of operation duration is captured by a new time model. The advantages of this new modeling approach are the following: (i) a modular construction of the joined process and job shop planning is allowed, (ii) classical known Petri net analysis methods can be applied and (iii) the analysis can be done at different levels of abstraction.     

基于Petri网和Agent的复杂适应系统建模

针对复杂适应系统内部关系繁杂、难于描述及计算机仿真建模困难等问题,提出一种基于时间Petri网和多Agent相结合的建模方法.以Agent为基本建模元素,用Petri网描述Agent内部的行为规则,实现复杂适应系统的Petri网与多Agent相结合的有机建模,可避免Petri网建模引起的模型空间爆炸和Agent内部推理...     

调度问题的HPN模型研究

本文介绍了层次Ｐｅｔｒｉ网模型（ＨＰＮ）的概念。层次Ｐｅｔｒｉ网的特点在于它不仅可以在某一层次上模拟系统的局部行为，而且还可以通过一定的关联机制来表现系统的整体特性。本文还通过研究调度问题的ＨＰＮ模型，探讨了如何应用ＨＰＮ来分析调度问题，为进一步研究调试方法提供了基础。     

Model Checking of Time Petri Nets Using the State Class Timed Automaton

In this paper, we propose a method for building the state class graph of a bounded time Petri net (TPN) as a timed automaton (TA), which we call the state class timed automaton. We consider bounded TPN, whose underlying net is not necessarily bounded. We prove that our translation preserves the behavioral semantics of the TPN (the initial TPN and the obtained TA are proved timed-bisimilar). It allows us to check real-time properties on TPN by using the state class TA. This can be done efficiently thanks to a reduction of the number of clocks. We have implemented the method, and give some experimental results illustrating the efficiency of the translation algorithm in terms of number of clocks. Using the state class TA, we also give a framework for expressing and efficiently verifying TCTL properties on the initial TPN.     

Efficient Verification of Parallel Real–Time Systems

This paper presents an efficient model checking algorithm for one–safe time Petri nets and a timed temporal logic. The approach is based on the idea of (1) using only differences of timing variables to be able to construct a finite representation of the set of all reachable states and (2) further reducing the size of this representation by exploiting the concurrency in the net. This reduction of the state space is possible, because the considered linear–time temporal logic is stuttering invariant. The firings of transitions are only partially ordered by causality and a given formula; therefore the order of firings of independent transitions is irrelevant, and only one of several equivalent interleavings has to be generated for the evaluation of the given formula. In this paper the theory of timing verification with time Petri nets and temporal logic is presented, a concrete model checking algorithm is developed and proved to be correct, and some experimental results demonstrating the efficiency of the method are given.     

基于扩展随机高级判断Petri网的FMS调度和仿真

本文提出一种新的更适合FMS调度仿真的扩展随机高级E-net,简称ESHLEP-N(Extended stochastic High Level Evluation Petri Net)。以ESHLEP-N模型为基础,设计并建立了FMS调度仿真专家系统。借助于该系统提出并研究了新的旨在减少空闲(no-inputs)和阻塞的实时动态再调度规则。经过仿真,证明新规则的产率(throughput)比传统规则平均提高6.48％。本文的部分成果已经用于航空航天部159厂的高级DNC系统的设计之中。     

CAD系统的多任务模型

本文以实际系统为背景，利用Ｐｅｔｒｉ网建立分析ＣＡＤ系统的多任务模型。我们从最基本Ｃｌｉｅｎｔ／Ｓｅｒｖｅｒ的调用模型出发，按调用关系扩展了两类多任务模型；有环模型和无环模型，并利用面向对象的观点提出了建构实用系数模型的模块化构造方法，同时还给出了一个简单的差错处理模型。