Frey, G.:
Hierarchical Design of Logic Controllers using Signal Interpreted Petri Nets.
Proceedings of the IFAC ADHS 2003, Saint-Malo (France), pp. 401-406, June 2003.

    Logic Controllers are often used to control continuous or hybrid processes. In these cases, the connection to the plant is realized by implementing pre- and post-processors for the conversion between analog and binary data. Hence, the controller remains purely discrete. However, the pre- and post-processors can not be included in the controller analysis. To overcome this problem, Signal Interpreted Petri Nets, a Petri net model for the specification of PLC programs, are extended to include non-binary signals. In this contribution hierarchical SIPN are presented. The analysis of the hierarchical net is based on the analysis of its subnets.