DESIGN OF PETRI NET CONTROLLERS TO EXCLUDE FORBIDDEN STATES IN MANUFACTURING SYSTEMS

Abstract

Abstract A novel method for Petri net controller synthesis to exclude forbidden states has been proposed. The method is based on the concepts of place invariants and the structural conflicts of Petri net theory. Design methodologies to deal with place (marking) constraints, transition (firing vector) constraints, and combined place/transition constraints are given. The Petri net controller derived is maximally permissive. Furthermore, it can be applied to any processes which can be modelled by ordinary Petri nets, without the restriction of safety. This method is very attractive even for large Petri net models and will be applicable to practical manufacturing systems due to its simplicity.