Session 4: DES Diagnosis

 Session chair: Jose Cury

10:30 - 12:30 Thursday 5th September 2013
10:30 Conjunctive Decentralized Diagnosis of Discrete Event Systems
Authors: Takashi Yamamoto, Shigemasa Takai
Abstract: In this paper, we study conjunctive decentralized diagnosis of discrete event systems. A notion of conjunctive codiagnosability which guarantees that any failure is detected by a conjunctive decentralized diagnoser within a uniformly bounded number of steps has been defined in literature. However, the existing condition for the system not to be conjunctively codiagnosable is sufficient but not necessary. Motivated by this fact, we propose a new algorithm for verifying conjunctive codiagnosability based on a necessary and sufficient condition for the system not to be conjunctively codiagnosable. To construct a conjunctive decentralized diagnoser for a conjunctively codiagnosable system, we need to compute the delay bound. We show how to compute the delay bound.
11:00 Supervision Patterns: Formal Diagnosability Checking by Petri Net Unfolding
Authors: Houssam-Eddine Gougam, Audine Subias, Y. Pencolé
Abstract: This paper addresses the problem of checking diagnosability of supervision patterns in discrete-event systems. With a supervision pattern, it is possible to represent a complex behavior of the system, and especially a faulty behavior. As opposed to classical diagnosability analyzers that check by exploring the marking graph of the underlying net, the proposed method relies on Petri net unfoldings and thus avoids the combinatorial explosion induced by the use of marking graphs. The method is an adaptation of the twin-plant method to net unfolding: a pattern is diagnosable if the unfolding representing the twin-plant does not implicitly contain infinite sequences of events that are ambiguous. 
11:30 Active Diagnosis of Deterministic I/O Automata
Authors: Melanie Schmidt, Jan Lunze
Abstract: A method for the active fault diagnosis of systems modeled by sets of deterministic input/output automata is presented, where each automaton describes the behavior of the system subject to a different fault. It is shown that the system is diagnosable if and only if there are no equivalent states in different automata. An active diagnostic algorithm is presented, which generates adequate input sequences for the system and evaluates the outputs of the system in order to identify the present fault. The applicability of the developed method is demonstrated by means of an example. 
12:00 A Discrete Time Consensus Approach for Fault Detection and Recovery in Unreliable Networks
Authors: Maria Pia Fanti, Agostino Marcello Mangini, Walter Ukovich
Abstract: In this paper we address the problem of the fault detection and recovery in networks of agents with discrete time dynamics. In particular, we apply a fault detection and recovery approach, proposed for the standard linear consensus protocol, to a consensus algorithm that has been previously presented by the authors and is based on a triangular splitting of the iteration matrix of the standard consensus algorithm. Moreover, we show that for a particular topology of the communication graph the fault recovery strategy can be implemented by the agents in a fully decentralized and autonomous approach. An example describes how in the considered framework the fault recovery is implemented by each agent.