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A game-theoretic approach to fault diagnosis and identification of hybrid systems
No full textPhysical systems can fail. For this reason the problem of identifying and reacting to faults has received a lot of attention in the control and computer science communities. In this paper we study the fault diagnosis problem for hybrid systems from a game-theoretical point of view. A hybrid system is a system mixing continuous and discrete behaviours that cannot be faithfully modelled neither by using a formalism with continuous dynamics only nor by a formalism including only discrete dynamics. We model hybrid systems as Hybrid Automata and add distinguished actions to describe faults. We define a Fault Identification Game on them, using two players: the environment and the identifier. The environment controls the evolution of the system and chooses whether and when a fault occurs. The identifier observes the external behaviour of the system and announces whether a fault has occurred or not. Existence of a winning strategy for the identifier implies that faults can be detected correctly, while computing such a winning strategy corresponds to implementing an identifier for the system. We will show how to determine the existence of a winning strategy, and how to compute it, for all decidable classes of hybrid automata that admit a finite bisimulation quotient
Fault Diagnosis of Hybrid Systems: an Onboard Camera Model
No full textIn this paper we apply a method for diagnosing faults on hybrid systems to a model of a camera mounted on a mobile robot. A hybrid system is a system mixing continuous and discrete behaviors that cannot be faithfully modeled neither by using a formalism with continuous dynamics only nor by a formalism including only discrete dynamics. We use the well known framework of hybrid automata for modeling hybrid systems, and try do detect faults exploiting a Fault Diagnosis Game on them, with two players: the environment and the diagnoser. The environment controls the evolution of the system and chooses whether and when a fault occurs. The diagnoser observes the external behavior of the system and announces whether a fault has occurred or not. The case study we introduce here is a simplified model of a camera mounted on a mobile rover that has to take pictures of some defined locations of the environment. We add the possibility of a stuck fault on the camera motor to apply the theory and show its effectiveness
Hierarchical Design of Distributed Fault Tolerant Control Systems
No full textThis work deals with the description of a design procedure for hierarchical Fault Tolerant Control (FTC) of large, distributed system. Following a functional perspective, a procedure for the modular design of the diagnostic and reconfiguration algorithms which run at different levels of the hierarchy is presented. The whole procedure is applied to an hydraulic benchmark system
A Game-Theoretic approach to Fault Diagnosis of Hybrid Systems
Get PDFPhysical systems can fail. For this reason the problem of identifying and reacting to faults has received a large attention in the control and computer science communities. In this paper we study the fault diagnosis problem for hybrid systems from a game-theoretical point of view. A hybrid system is a system mixing continuous and discrete behaviours that cannot be faithfully modeled neither by using a formalism with continuous dynamics only nor by a formalism including only discrete dynamics. We use the well known framework of hybrid automata for modeling hybrid systems, and we define a Fault Diagnosis Game on them, using two players: the environment and the diagnoser. The environment controls the evolution of the system and chooses whether and when a fault occurs. The diagnoser observes the external behaviour of the system and announces whether a fault has occurred or not. Existence of a winning strategy for the diagnoser implies that faults can be detected correctly, while computing such a winning strategy corresponds to implement a diagnoser for the system. We will show how to determine the existence of a winning strategy, and how to compute it, for some decidable classes of hybrid automata like o-minimal hybrid automata
A framework for Fault Diagnosis of Hybrid Systems based on Predicate Abstractions
No full textIn this paper we aim at checking fault reconfigurability in hybrid systems. A hybrid system is a system mixing continuous and discrete behaviours that cannot be faithfully modeled neither by using a formalism with continuous dynamics only nor by a formalism including only discrete dynamics. We extend the well known framework of hybrid automata for modeling hybrid systems, adding faults leading to recoverable and unrecoverable states. We use a discrete abstraction of hybrid automata to design a diagnoser that observes the external behaviour of the system and announces whether a fault has occurred or not. Moreover if the diagnoser is able to detect the fault before the system reaches an unrecoverable state, then the automaton is also reconfigurable. We prove the effectiveness of this procedure with a simple case study
Distributed fault tolerant control of the two-tanks system benchmark
No full textIn this work the application of a new Fault Tolerant Control strategy to the two-tanks system is presented. This system is viewed as a distributed system and it is divided, following a functional reasoning, into partial processes supervised at different levels. The results presented in the paper have been realized in the context of the European Project IFATIS (proposal number IST-2001-32122)
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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