Design of Petri net controllers to exclude forbidden states in manufacturing systems

Abstract

Proposes a design method to avoid the forbidden states based on the concepts of place invariants and structural conflicts, inspired by the work of Yamalidou et al. (1994). Due to the utilization of structural conflicts, the synthesis procedure is greatly simplified when dealing with forbidden states involving firing vectors (transitions), and the resulting Petri net controller is simpler (size is smaller and the connections are simpler) than those obtained based on place invariants alone. Moreover, the method can be applied to any ordinary Petri net without the restriction of safety, which significantly extends the application domain. The method developed in this paper is generic, yet it is computationally efficient. For this reason, a Petri net controller can be synthesized for very large Petri net models, opening the way to design Petri net controllers for real industrial applications in manufacturing and batch processing where the processes can be efficiently modelled by Petri nets. (6 pages)