Scheduling Availability of Discrete Event Systems
Associate Professor Calin I. Ciufudean
“Stefan Cel Mare” Universtity of Suceava
Faculty of Electrical Engineering and Computer Science
Department of Automatics and Computers
9, University str., RO720225, Suceava
Abstract: Fault detection is a crucial
and challenging task in the automatic control of complex systems, e.g. in
flexible manufacturing systems (FMS’s) as a representative class of discrete
event systems (DES’s).
A discrete event system approach to the problem of failure diagnosis is
presented. The property of diagnosability is introduced in the context of
the failure diagnosis problem, e.g. in the context of the availability of
the DES. We bring a DES approach to the problem of failure diagnosis of
FMS’s because most of them are modelled by DES’s, and because continuous
variable dynamic systems can often be viewed as DES’s at a higher level of
abstraction, respectively when their trajectories are determined by
meaningful accumulations of dynamics e.g., are determined by events. The
states of the discrete event model reflect the normal and the failed status
of the system components, while the failure events form part of the event
We propose a systematic procedure for detection of failure events using
diagnoses implemented with stochastic coloured Petri nets (SCPN). The
diagnoser is a SCPN which models the FSM. This model performs detection and
isolation of failures (failure information and occurrences of failures can
be detected by inspecting the states of the SCPN model), and it also permits
the verification of the diagnosability properties of the system (e.g.,
permits the estimation of the availability of the system). In our assumption
the availability of a production cell j (j=1.2….,n, where n is the total
number of part cells in the FMS) is calculated with a Markov chain that
includes the failure rates, repair rates, and coverability of the respective
devices in the production cell j.
An analytical approach for the availability evaluation of cellular
manufacturing systems (as basic components of FMS’s) is presented, where a
FMS is considered operational as long as its production capacity
requirements are satisfied.
The approach is used to evaluate transient and steady-state performance of
alternative designs based on an industrial example.
Brief Biography of the Speaker:
• Honorary Member of the Romanian Society of Electrical & Control
Engineering - Member of the Romanian Technical Experts Corp.
• Technical Expert of the Romanian Ministry of Justice.
• President of the Romanian Society of Electrical & Control Engineering,
• Academic Positions: Assoc. Professor, Dept. of Automatics and Computers,
Faculty of Electrical Engineering and Computer Science, “Stefan cel Mare”
University of Suceava, Romania.
• Fields of Scientific Activities: Discrete Event Systems, Complex
Measurement Systems, Reliability and Diagnosis of Control Systems,
• He published 6 books and over 120 scientific papers in conference
proceedings and journals.