On the Implementation of Supervised Control of Discrete Event Systems

Supervisory control theory is well developed, but its use in industrial applications can be limited by a set of problems arising when supervisors have to be implemented on common control machines. As a matter of fact, the asynchronous and undetermined nature of supervisors makes their implementation on synchronous devices like programmable logic controllers (PLCs) and PCs a complicated task. In this paper, an overview on the existing techniques about this topic is given first. Then, the supervised control approach is used to implement supervisors and the supervised control architecture consisting of a controller and a supervisor is completed by a dispatcher to obtain a closed-loop, determined behavior. The main problems occurring in implementing supervised control on synchronous devices are presented and discussed. Finally, a method is proposed to translate automata, Petri net or colored Petri net supervisors in structured text language, one of the IEC 61131-3 standard languages, by preserving their structure and the closed-loop behavior as expected from the theory.