Online monitoring for diagnosis of violations of constraints in Petri net models

Abstract

Abstract Fault diagnosis in partially-observed discrete-event systems requires modelling faults as unobservable events within the system. Representing faults as events is not always realistic. For example, some classes of fault are in form of violations of constraints such as service-level agreement (SLA) and Quality of Service (QoS). To model such faults, we need to modify the plant model which is not always acceptable. Firstly, this may make the models large. Secondly, adding extra transitions is not always preferable from engineers’ prospective as every modification of the constraint will modify the model of the plant. This paper applies integer Fourier-Motzkin elimination (IFME) approach to address this issue. Since the constraints and their violations can be written as inequalities, we show that starting from a Petri net two sets of inequalities (diagnoser) are obtained. These sets are used to judge whether an observed sequence may satisfy (violate) these inequalities. The correctness of the proposed approach has also been proved.