Joao Carlos Basilio

Federal University of Rio de Janeiro | UFRJ · Departamento de Engenharia Elétrica (DEE)

The problem of fault diagnosis of discrete event systems (DESs) concerns the capacity to detect the occurrence of fault events. In this work, we present a new fault diagnoser that uses labeled priority and λ-free diagnoser Petri nets to diagnose the fault occurrences of DESs modeled by Petri nets, which may be bounded or unbounded. By analyzing the...

Denial-of-Service (DoS) are attacks conducted by malicious agents that consists in disrupting, temporally or indefinitely, the services provided by a communication network. When a malicious agent gets access to some network node, it may also perform deception attacks by inserting valid packets with fake information into vulnerable channels. We addr...

In this paper, we deal with current-state opacity, and propose an Opacity-Enforcer that is able to change, in an appropriate way, the order of observation of event occurrences in the system, and also to delete event observations, so as to mislead the Intruder to never be sure if the current state of the system is a secret state. We then present two...

We address, in this article, the problem of codiagnosability of networked discrete event systems with timing structure (NDESWTS) subject to delays and loss of observations of events between the measurement sites (MS) and local diagnosers (LD). To this end, we first introduce a new timed model that represents the dynamic behavior of the plant based...

In this paper, we revisit the problem of robust diagnosability of Discrete-Event Systems (DES), and present a comparative analysis between the following notions of robust diagnosability existing in the literature: (i) diagnosability of DES subject to permanent sensor failures, assuming that sensors may fail only before the first occurrence of the e...

Real life experience has shown that intermittent faults are among the most challenging kinds of faults to detect and isolate, being present in the majority of production systems. Such a concern has made intermittent fault an active area of research in both discrete event and continuous-variable dynamic systems. In this paper, we present a review of...

Detection of abnormality (or faults) occurrences is of paramount importance in smart manufacturing systems of Industry 4.0 since faults do not usually take the system immediately to a halt, and so, it can jeopardize an entire production. With that in mind, we propose here an online diagnoser based on the Petri model of either a specific machine or...

O primeiro estágio do projeto de diagnosticadores de falhas para sistemas industriais consiste na obtenção de um modelo que descreva tanto o comportamento normal como o de falha. No contexto de diagnose de falhas de sistemas a eventos discretos (SED), o Mapeamento de Sensores (MS) é uma ferramenta utilizada para a obtenção de modelos por autômatos....

In this article, we study the supervisory control problem of networked discrete event systems with timing structure assuming bounded communication delays and intermittent loss of observations. The communication between the plant and the supervisor is through a network that can have several channels, and so communication delays may change the order...

Predictability is a discrete-event system property that aims to foresee some specific event occurrence, usually seen as failures. Two common assumptions in most existing works are the absence of cycles of states that are connected with unobservable events and language liveness, which could be restrictive in some system cases. In this paper, we revi...

This paper deals with the problem of copredictability verification of discrete event systems (DES) modeled by automata in less restrictive scenarios, i.e., avoiding the assumptions on language liveness and absence of cycles of states connected by unobservable events only. We present necessary and sufficient conditions for a regular language to be c...

We address in this paper the design of robust supervisors that are able to cope with intermittent loss of observations and also make the controlled system achieve the specification language under nominal operation. In order to do so, we introduce a definition of robust observability that leverages possible observations of the events that are subjec...

It has been argued for some time now, based on classroom, textbook and practical examples that the size of verifiers and diagnosers is comparable. This belief has been corroborated by a recent paper, where it is conjectured, based on a rigorous statistical analysis, that the size of the states of diagnosers is Θ(n0.77logk+0.63), on the average, whe...

In building failure diagnosis systems for discrete-event systems, two performance indexes must be specified: (i) the maximum time the diagnosis system takes to detect the failure occurrence, usually referred to as T-diagnosability; and (ii) if no time information is available, how many events must occur after the failure in order for the diagnosis...

Failure diagnosis is a crucial task in modern industrial systems, and several works in the literature address this problem by modeling the system as a Discrete-Event System (DES). Most of them assume perfect communication between sensors and diagnosers, i.e., no loss of observation of events, or event communication delays between the measurement si...

Diagnosability is an intrinsic property of the language generated by discrete event systems (DES) and the computational procedure to determine whether a language possesses or not this property is called diagnosability verification. For regular languages, diagnosability verification is carried out by building either diagnoser or verifier automata; t...

We address in this paper the problems of online diagnosis and verification of language diagnosability of discrete event systems (DES) modeled by acyclic labeled Petri nets, in which, different transitions can be labeled by the same event (observable, unobservable and failure). The proposed diagnoser makes its decision regarding the failure occurren...

This paper addresses the modular diagnosability verification of discrete event system (DES). We assume that the language generated by each automaton module can have deadlocks and that the common events among modules are observable. A new algorithm is developed based on the proposition of a necessary and sufficient condition for modular diagnosabili...

We address, in this paper, the problem of diagnosing intermittent sensor faults. In order to do so, we employ a model of intermittent loss of observations recently proposed in the literature, and use this model, together with an appropriately modified label automaton, to change the problem of detecting intermittent sensor faults into a problem of d...

In order to diagnose the occurrence of a fault event in a Discrete-Event System (DES), it is first necessary to verify if the language of the system is diagnosable with respect to an observable event set and a fault event set. In some cases, the language of the system is also diagnosable even when a subset of the set of observable events under cons...

In this paper, we present a new property of relative observability, and based on this property, we propose two algorithms: the first one, that has polynomial complexity, verifies if a regular language is relatively observable; the second algorithm computes the supremal relatively observable sublanguage of a given regular language. Although the latt...

In this paper, we present a new property of relative observability, and based on this property, we propose two algorithms to deal with relative observability of regular languages. The first algorithm, that has polynomial complexity, verifies if a regular language is relatively observable. The second algorithm, that computes the supremal relatively...

The essence of a public bicycle sharing system (PBSS) is very simple: to allow someone to pick up a bicycle at some point of a region and return it to another place. A redistribution vehicle is used to move bicycles from stations that are almost full to those almost empty; this is usually referred to as balancing operation. This poses an important...

Failure diagnosis is a crucial task in modern industrial systems, and several works in the literature address this problem by modeling the system as a Discrete-Event System. Most of them assumes perfect communication between sensors and diagnosers, i:e:, no loss of observation of events, or event communication delays between the measurement sites a...

Different notions of robust diagnosability of discrete-event systems (DESs) have been introduced in the literature. In all these works, the objective is the detection of unobservable fault events in DESs subject to uncertainties in the observation of the events and/or in the plant model. Recently, the so-called robust diagnosability of DESs against...

Although the theory of failure diagnosis of discrete-event systems has been proved effective, one question remains open: assuming that the generated language is diagnosable, how long does the diagnosis system take to detect the failure occurrence? In this paper, although we still consider the DES as a dynamic system whose evolution is determined by...

This paper shows that the first step in the design of multivariable controllers within the Characteristic Locus Method must be the design of a static normalizing pre-compensator that makes the pre-compensated plant as closely as possible to a normal matrix at the vicinity of the crossover frequency, if robustness is to be addressed in a later stage...

We propose in this paper a Petri net approach to online diagnosis of discrete event systems (DESs) modeled by finite state automata. The diagnosis method is based on the construction of a Petri net diagnoser (PND) which is constructed in polynomial time and requires less memory than other methods proposed in the literature. We also present methods...

In [1] the authors claim that there is an oversight in [2], in the sense that the proposed verifier is, in general, nondeterministic and the computational complexity analysis is incorrect. The authors in [1] also claim that the complexity of the verification algorithm presented in [3] is reduced when considering the more restrictive setting of proj...

Extended labeled Petri nets (ELPNs), i.e., labeled Petri nets with inhibitor arcs, are usually used to model the desired closed-loop behavior of a controlled discrete-event system, and, as such, their states are formed with both the controller and the plant states. However, the control logic is based on the controller states only and the interactio...

Local minima are still an important unsolved problem for artificial potential field approaches. In order to overcome this problem, we propose in this paper a new method inspired by the deterministic annealing approach that can be classified as LMA, since it prevents the robot from being trapped in a local minimum point, and allows the robot to cont...

This paper presents a new algorithm for mobile robots to escape from local minima points in an environment, which is inspired in the deterministic annealing algorithm. A comparative study between the proposed method and two known methods, simulated annealing to escape from local minima and the method of virtual obstacle, is carried out.

We address in this paper the problem of diagnosing intermittent sensor faults. In order to do so, we modify the model of intermittent loss of observations proposed in the literature to account for sensor malfunction only. Using this model together with a modified label automaton, it will be possible to change the problem of detecting intermittent s...

We consider the problem of diagnosing the occurrence of a certain unobservable event of interest, the fault event, in the operation of a partially-observed discrete-event system subject to permanent loss of observations modeled by a finite-state automaton. Specifically, it is assumed that certain sensors for events that would a priori be observable...

In the usual approaches to fault diagnosis of discrete event systems it is assumed that not only all sensors work properly but also all information reported by sensors always reaches the diagnoser. Any bad sensor operation or communication failure between sensors and the diagnoser can be regarded as loss of observations of events initially assumed...

We deal with the problem of finding sets of observable events (event bases) that ensure language diagnosability of discrete-event systems modeled by finite state automata. We propose a methodology to obtain such event bases by exploiting the structure of the diagnoser automaton, and in particular of its indeterminate cycles. We use partial diagnose...

All methods presented in textbooks for computing inverse $ {\cal Z}$-transforms of rational functions have some limitation: 1) the direct division method does not, in general, provide enough information to derive an analytical expression for the time-domain sequence $x(k)$ whose $ {\cal Z}$-transform is $X(z)$ ; 2) computation using the inversion i...

In this paper we present deslab, a scientific computing program written in python, for the development of algorithms for analysis and synthesis of discrete event systems (DES) modeled as automata. The main objective of deslab is to provide a unified tool that integrates automata, graph algorithms, and numerical calculations. deslab also allows the...

The continued progress and growth of industry has increased the need for communication and control integration. In this regard, it would be interesting to apply simple algorithms that combine model parameter identification and tuning of PID controllers. In this work we consider the digital implementation of a PID self-tuning system formed with an i...

The first step in the diagnosis of failure occurrences in discrete event systems is the verification of the system diagnosability. Several works have addressed this problem using either diagnosers or verifiers for both centralized and decentralized architectures. In this technical note, we propose a new algorithm to verify decentralized diagnosabil...

This study deals with the design of H_∞ controllers for speed control of rotor flux-oriented current-controlled induction motors. The mixed sensitivity problem (robust stability and performance) is initially revisited, and is shown, based on practical experiments, that when the rotor time constant is the uncertain parameter, it is necessa...

Reverse-frame-normalizing controllers overcome the sensitivity problems of commutative controllers and balance the tolerance of multivariable feedback systems to input and output multiplicative unstructured uncertainty. They are, however, based on the singular value decomposition of transfer function matrices and lead to implementation difficulties...

Sensitivity to parameter perturbation represents the main caution regarding the use of the characteristic locus method on the design of multivariable control systems. The method is not effective when the condition number of the plant eigenvector matrix is high or, equivalently, when the plant transfer matrix differs a great deal from normality. Wit...

Fault diagnosis of discrete event systems modeled as au-tomata This tutorial presents the background necessary to the study and research on fault diagnosis of discrete-event systems modeled as automata. Both centralized diagnosability and co-diagnosability with coordination are considered. Besides presenting necessary and sufficient conditions for...

This tutorial presents the background necessary to the study and research on fault diagnosis of discrete-event systems modeled as automata. Both centralized diagnosability and co-diagnosability with coordination are considered. Besides presenting necessary and sufficient conditions for the verification of diagnosability and co-diagnosability, the p...

Failure diagnosis is an important task in large complex systems and as such this problem has received in the last years considerable attention in the literature. The first step to diagnose failure occurrences in discrete event systems is the verification of the system diagnosability. Several works in the literature have addresses this problem using...

The modeling of physical systems using discrete event models assumes that a set of sensors always report the event occurrences correctly. However, bad sensor operation can result in loss of observability of the events associated with the malfunctioning sensors. If one or more sensors fail, it may be possible that either the diagnoser stands still o...

One approach to online fault diagnosis of discrete-event systems is through the use of the diagnosers. Diagnosers are deterministic automata whose states are sets formed with the states of the plant together with labels that indicate if the trace that has occurred so far possesses or not the fault event. The decision regarding fault occurrence is t...

The modeling of physical systems using discrete event models assumes that a set of sensors always report the event occurrences correctly. However, bad sensor operation can result in loss of observability of the events associated with the malfunctioning sensors. If one or more sensors fail, it may be possible that either the diagnoser stands still o...

We consider robust decentralized diagnosis of discrete event systems, where the goal is to detect the occurrence of unobservable fault events using a set of local diagnosers that are themselves subject to failures. We introduce a formal notion of robust decentralized diagnosability, called robust codiagnosability, and study its properties. Two diff...

Controlled systems designed by using the characteristic locus method can be very sensitive to small perturbations in the plant input and output at the frequencies where the plant transfer matrix is far from normal. In order to improve the closed-loop system robustness, previous work proposes the design of a dynamic normalizing pre-compensator follo...

Control Interpreted Petri Nets (CIPN) provide high level structured controllers for discrete event systems. However, discrete event control systems are usually implemented in PLCs using a graphical symbolic language called Ladder diagram, which is a low level programming language not suitable for the analysis and design of complex discrete event co...

This paper addresses the issues of modelling, simulation, design, and controller implementation in an Industrial Control course. The motivation for it comes from the fact that, differently from the plants used in first courses on control systems, which usually have fast step response, plants suitable for Industrial Control courses have slow step re...

This paper extends an existing sensor mapping procedure, defines compatibility of models and proposes an integrated methodology based on existing methodologies for the construction of diagnosers for discrete event systems modeled by Petri Nets. An industrial application is used as a case study to illustrate the theoretical results of the paper.

In a debate paper, Keel and Bhattacharyya have suggested, by means of simple examples taken from the open literature, that optimal and robust controllers can be fragile in the sense that a minute perturbation in the controller parameters can make the closed-loop system unstable. However, is it true that the optimal and robust controllers presented...

The Characteristic Locus Method constitutes a generalisation of the classical frequency response approach and as such provides a natural platform for design aimed at meeting specifications such as closed-loop stability and dynamic performance. However, to overcome problems of sensitivity to uncertainty, it is necessary to precondition the plant tra...

Normalization is a crucial requirement for the effectiveness of multivariable control system design within the Characteristic Locus Method. Previous work addresses this problem by solving an optimization problem formulated in order to increase normality; its formulation, however, do not consider the closed-loop system robustness with respect to per...

The characteristic locus method provides a systematic way to extend the classical control design techniques to multivariable systems. In addition, the manipulation of the eigenfunctions of the open-loop transfer matrix also allows optimal control problems, usually formulated using H ∞ optimization theory, to be addressed in the same manner as for s...

In a recent paper, Keel and Bhattacharyya suggest, by means of simple examples taken from the literature, that H¥ robust controllers can be fragile in the sense that a minute perturbation in the controller parameters can make the closed-loop system unstable. Subsequent works have related this problem to controller implementation and suggested that...

In this paper, algorithms for the computation of all matrices of the generalized polyno-mial Bezout identity are proposed. The algorithms are based on the computation of minimal polynomial basis for the right null spaces of certain polynomial matrices. For this reason, an algorithm for the computation of minimal polynomial bases is also proposed. S...

In a recent paper, Keel and Bhattacharyya suggest, by means of simple examples taken from the literature, that H∞, robust controllers can be fragile in the sense that a minute perturbation in the controller parameters can make the closed-loop system unstable. Subsequent works have related this problem to controller implementation and suggested that...

A difficulty usually encountered in the preparation of a state-space-oriented control laboratory is that most of the system identification techniques available in the literature are for input/output models. Although in recent years there has been a growing interest in state-space identification methods, the application of these techniques in underg...

In this paper the design of a control system for rotor flux oriented controlled induction motor drives using H_∞ optimal control theory is carried out. The variable to be controlled is the shaft velocity. Two H_∞ problems are formulated and solved: (i) a 1-block problem with the view to maximizing the system performance; (ii) a...

In this paper the design of a control system for rotor flux oriented controlled induction motor drives using H∞ optimal control theory is carried out. The variable to be controlled is the shaft velocity. Two H∞ problems are formulated and solved: (i) a 1-block problem with the view to maximizing the system performance; (ii) a 2-block problem with t...

In this paper, the problem of computing inverses of polynomial matrices has been revisited and algorithms of easy implementation are proposed to deal with either column or non-column reduced matrices. Other contributions of the paper are algorithms to perform column reduction and determinant of polynomial matrices.

Proportional-integral-derivative (PID) controllers are widely used in industrial control systems because of the reduced number of parameters to be tuned. The most popular design technique is the Ziegler-Nichols method, which relies solely on parameters obtained from the plant step response. However, besides being suitable only for systems with mono...

The characteristic locus method provides a systematic way to extend the classic control design techniques to multivariable systems. When other control objectives such as robustness are to be considered, the usual approach is to obtain a parametrization of allstabilizing controllers and in the sequel to deploy the available degrees of freedom in ord...

Previous algorithms to obtain reduced-order models by balanced truncation in a single step either require a very specific way to solve a pair of Lyapunov equations or are suitable only for scalar or symmetric MIMO systems. In this paper, model reduction is revisited and an algorithm to obtain a reduced order model in one step only is proposed. As i...