Abrupt and Drift-Like Fault Diagnosis of Concurent Discrete Event Systems

Discrete Event Systems (DES) are dynamical systems that evolve according to the asynchronous occurrence of certain changes called events. This paper proposes a modular approach for abrupt and drift-like fault diagnosis of concurrent DES. In this class of DES, the system consists of several components or subsystems that operate concurrently. Each component is modeled as a sequence of predetermined actions as well as the responses to these actions. Each component model represents the desired (nominal) system behavior. An abrupt fault is viewed as a violation of the component desired behavior. While a drift-like fault is viewed as a drift in the normal characteristics of component response to actions. An indicator measuring the change in the response characteristics of the component is used to detect a drift. This detection can be then used to warn a human operator when the component behavior starts to deviate from its normal behavior. The proposed approach is illustrated using a manufacturing system.