| Abstrakt: |
This paper addresses the problem of fault diagnosis and diagnosability enforcement of discrete event systems. Given a nondiagnosable discrete event system modeled with Petri nets, which may enter deadlocks and unobservable live-locks, a digital twin system (derived from the original Petri net model) can be established as a particular Petri net such that the closed-loop system established from the original system under the control of its digital twin counterpart is diagnosable. This procedure employs a deterministic finite automaton (derived from the digital twin system) to diagnose the closed-loop system and provides necessary and sufficient conditions for diagnosability enforcement. In this way, we do not need to compute and analyse the reachability graph or basis reachability graph of the original Petri net, which in practice reduces the computational overheads as exposed by experimental studies. Examples are presented to demonstrate the proposed method. Note to Practitioners—Fault diagnosis and diagnosability enforcement are critical for the development and operation of highly automated systems covering computer-integrated production processes, intelligent traffic, computer and communication networks, smart gird, etc. This work touches upon this problem from the perspective of discrete event systems that are modeled with Petri nets. The feasibility and applicability of the reported method stem from the usage of a digital twin system derived from a plant to be investigated such that the computational cost of a real-world system is acceptable. The graphical representation of Petri nets as well as the digital twin system make the method easy to use and manipulate. Moreover the sufficient and necessary conditions of diagnosability enforcement can be readily verified by the basics of graph theory, facilitating its adoption by practitioners. |
