Hierarchical Design of Logic Controllers Using Signal Interpreted Petri Nets

Abstract

Logic Controllers are often used to control continuous or hybrid processes. In these cases, the connection to the plant is realized by implelnenting 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 problenl, Signal Interpreted Petri Nets, a Petri net model for the specification of PLC programs, are extended to include nonbinary signals. In this contribution hierarchical SIPN are presented. The analysis of the hierarchical net is based on the analysis of its subnets.