Fault Detection In Discrete Event Systems Research Articles

Fault detection of Discrete-Event Systems based on an identified timed model

In this paper, a method for fault detection of Discrete-Event Systems (DES) based on a timed model called Timed Automaton with Outputs and Conditional Transitions (TAOCT), obtained by identification, is presented. The TAOCT is an extension of a recent untimed model proposed in the literature, called Deterministic Automaton with Outputs and Conditional Transitions (DAOCT). Differently from the DAOCT, where only the logical behavior of the DES is considered, the TAOCT takes into account information about the time that the events are observed, and, for this reason, it can be used for the detection of faults that cannot be detected by using untimed models, such as faults that lead the fault detector to deadlocks. The TAOCT represents the fault-free system behavior, and a fault is detected when the observed behavior is different from the one predicted by the model, considering both logical and timing information. A practical example is used to illustrate the results of the paper.

A Framework for Control-Reconfiguration Following Fault-Detection in Discrete Event Systems

We introduce a framework for control-reconfiguration in discrete event systems that performs fault-detection and then reconfigures the control to ensure that certain desired specifications are met. The controlled system has separate specifications prior to a fault versus after a fault (to allow for any changes in the specification owing to the occurrence of a fault). Prior to the occurrence of a fault, a certain controller is applied so as to ensure a given pre-fault specification. The same controller is continued to be used even after a fault and until its detection. Once a fault is detected, the control is reconfigured. All along the post-fault duration (prior to as well as after reconfiguration), the controlled system is required to satisfy a give post-fault specification. We mathematically formulate the above control problem and provide a condition for reconfigurability. We also establish the condition for the limiting case where control-reconfiguration is not required. Also, we introduce the notion of degree of disambiguability of faulty traces which when increased, increases the ability to meet the control requirements of pre- and post- fault specifications.