Sufficient conditions for diagnosability of DES modeled as Petri net are given in this paper. In proposed framework we refer to the concept of diagnosability given by Sampath et al. for finite state automata; as far as the fault events are concerned, they are modeled as unobservable transitions. The results here presented are based on the mathematical representation of PNs, and their complexity does not depend on the initial marking of the net. Hence the proposed approach does not suffer of the state space explosion problem, as the diagnoser approach does.

In this paper a new approach to fault diagnosis of discrete events systems modeled with Petri nets is presented. Fault events are associated to a subset of unobservable transitions of the net. Negative markings, called generalized marking, are used to estimate the explanations of the observed transitions. The generalized markings allow to cope with the problems related with the explosion of the state space estimation in a very efficient way in terms of memory usage. This feature makes the propos...

This paper studies online fault detection and isolation of modular dynamic systems modeled as sets of place-bordered Petri nets. The common places among the set of Petri nets modeling a system capture coupling of various system components. The transitions are labeled by events, some of which are unobservable (i.e., not directly recorded by the sensors attached to the system). The events whose occurrence must be diagnosed have unobservable transition labels. These events model faults or other sig...

The diagnosis of discrete event systems is strongly related to events estimation. This paper focuses on faulty behaviors modeled with ordinary Petri nets with some "fault" transitions. Partial but unbiased measurement of the places marking variation is used in order to estimate the firing sequences. The main contribution is to decide which sets of places must be observed for the exact estimation of some given firing sequences. Minimal diagnosers are defined that detect and isolate the firing of ...

In this note, we develop algebraic approaches for fault identification in discrete-event systems that are described by Petri nets. We consider faults in both Petri net transitions and places, and assume that system events are not directly observable but that the system state is periodically observable. The particular methodology we explore incorporates redundancy into a given Petri net in a way that enables fault detection and identification to be performed efficiently using algebraic decoding t...

In this paper we present an efficient approach for the fault detection of discrete event systems using Petri nets. We assume that some of the transitions of the net are unobservable, including all those transitions that model faulty behaviors. We prove that the set of all possible firing sequences corresponding to a given observation can be described as follows. First a set of basis markings corresponding to the observation are computed together with the minimal set of transitions firings that j...

The problem of achieving fault-tolerant supervision of discrete-event systems is considered from the viewpoint of safe and timely diagnosis of unobservable faults. To this end, the new property of safe diagnosability is introduced and studied. Standard definitions of diagnosability of discrete-event systems deal with the problem of detecting the occurrence of unobservable fault events using model-based inferencing from observed sequences of events. In safe diagnosability, it is required in addit...

A framework is introduced for fault diagnosis in timed discrete-event systems. In this approach, the required estimates for system condition are updated only when the output changes or when deadlines associated with output changes expire. Thus updates at every clock tick are not required. This in many cases results in reduction in online computing requirements and in the size of the diagnosis system, at the expense of more offline design calculations. The issue of failure diagnosability is also ...

The problems ofstate observation and diagnosis are solved for discrete–event systems, which are described by stochastic automata. As many systems are not observable in the sense that it is possible to reconstruct the state unambiguously, the observation problem is set up as the problem of determining the smallest possible set of states that are compatible with the measured input and output sequences. The diagnostic problem is shown to be, in principle, an observation problem. Conditions for the ...

We address the problem of failure diagnosis in discrete event systems with decentralized information. We propose a coordinated decentralized architecture consisting of local sites communicating with a coordinator that is responsible for diagnosing the failures occurring in the system. We extend the notion of diagnosability, originally introduced in Sampath et al. (1995) for centralized systems, to the proposed coordinated decentralized architecture. We specify three protocols that realize the pr...

Fault detection and isolation is a crucial and challenging task in the automatic control of large complex systems. We propose a discrete-event system (DES) approach to the problem of failure diagnosis. We introduce two related notions of diagnosability of DES's in the framework of formal languages and compare diagnosability with the related notions of observability and invertibility. We present a systematic procedure for detection and isolation of failure events using diagnosers and provide nece...

#1Ahmed Al-Ajeli(College of Information Technology)H-Index: 2

#2David Parker(University of Birmingham)H-Index: 72

Abstract null null We propose techniques for fault diagnosis in discrete-event systems modelled by labelled Petri nets, where fault events are modelled as unobservable transitions. The proposed approach combines an offline and an online algorithm. The offline algorithm constructs a diagnoser in the form of sets of inequalities that capture the legal, normal and faulty behaviour. To implement the offline algorithm, we adopt the Fourier–Motzkin method for elimination of variables from these sets o...

In this paper, we present a diagnoser-based approach to deal with fault diagnosis of bounded labeled Petri nets. The approach consists in building a semi-symbolic diagnoser to analyze diagnosability and perform online diagnosis. The contribution of this paper is twofold: (i) from the theoretical point of view, we provide new conditions for checking diagnosability based on a novel diagnoser variant that explicitly separates the normal reachable markings from the faulty ones, in each diagnoser nod...

Various aspects of privacy and safety in many application domains can be assessed based on proper analysis of successive measurements that are collected about a given system. This work is devoted to such issues in the context of timed stochastic discrete event systems (DES) that are modeled with partially observed timed stochastic Petri net models. The first contribution is to introduce a k-step trajectory-observer, which is a construction that captures all possible k-suffixes of the trajectorie...

#1Ahmed Al-Ajeli(College of Information Technology)H-Index: 2

#2David Parker(University of Birmingham)H-Index: 72

Abstract Fault diagnosis in partially-observed discrete-event systems requires modelling faults as unobservable events within the system. Representing faults as events is not always realistic. For example, some classes of fault are in form of violations of constraints such as service-level agreement (SLA) and Quality of Service (QoS). To model such faults, we need to modify the plant model which is not always acceptable. Firstly, this may make the models large. Secondly, adding extra transitions...

#1Ahmed Al-Ajeli(College of Information Technology)H-Index: 2

#2David Parker(University of Birmingham)H-Index: 72

This paper presents a new approach for the fault diagnosis problem in partially observable discrete-event systems modelled with Petri nets. Our approach is based on the use of the Integer Fourier-Motzkin Elimination (IFME) method. The fault diagnosis problem is solved by first creating an initial set of inequalities from the state equation of a Petri net. The occurrence or absence of faults can also be expressed by inequalities. After adding these inequalities to the initial set, we apply the IF...

This paper is devoted to the development of an approach to the diagnosability of a system described in the framework of partially observed Petri nets (POPNs) such that the developed fault diagnosis technique can be widely applicable to systems with mutable initial states and partial observations. Existing studies show that the diagnosability of a discrete event system (DES) can be improved by suitable sensor selections or redundancies. This paper proposes a redundancy-building method for a POPN ...

Aug 1, 2016 in CASE (Conference on Automation Science and Engineering)

#1Li Yin(MUST: Macau University of Science and Technology)H-Index: 3

#2Zhiwu Li(MUST: Macau University of Science and Technology)H-Index: 63

Last. Naiqi Wu(MUST: Macau University of Science and Technology)H-Index: 49

view all 3 authors...

In this paper, we focus on fault diagnosis in discrete event systems (DESs) which are modeled by partially observed Petri nets. We consider not only the case where faults occur either on transitions or places, but also a more general case where faults occur on both transitions and places at the same time. Some faults cannot be diagnosed directly due to the unobservability of some transitions and places in a partially observed Petri net. We propose an approach to diagnose the faults that cannot b...

This paper presents a new technique for failure diagnosis in partially observable discrete event systems modelled as Petri nets. In this new technique we adopt Integer Fourier-Motzkin Elimination (IFME) method. We start with a Petri net and produce the state equations. The state equations are a set of integer valued inequalities in variables that represent number of firing of transitions. Occurrences of failure can also be expressed by inequalities. Then we extend the set of inequalities obtaine...

Failure detection in partially observable model based Discrete Event Systems requires modelling failures as unobservable events within the system. Representing failures as events is not always realistic. For example, some classes of failure are in form of violations of constraints such as Service Level Agreement (SLA) and Quality of Service (QoS). These forms of failures do not represent events by themselves. They have to be modelled as additional events. Modifying the plant model is not always ...

Fault diagnosis of discrete-event systems has received a lot of attention in the literature since the early 90s. At the beginning, the problem has been approached using the framework of finite state automata and regular languages. Recently, the problem has been tackled within the Petri nets (PNs) framework. This paper overviews the main ideas behind the fault diagnosis approaches based on PNs.