Evaluating the complexity of Petri nets and ladder logic diagrams for sequence controllers design in flexible automation

This paper presents a methodology to evaluate the complexity of Petri nets (PNs) and ladder logic diagrams (LLDs) for sequence controllers design. Complexity of a design is characterized by the number of basic elements used to model the given control logic. More specifically, this paper presents analytical formulas to estimate the number of basic elements to model certain building blocks of logic modeling when PN and LLD are used. Also, by presenting a methodology to use these analytical formulas, this paper precludes the need for physically building the controllers by either PN or LLD for the comparison of their graphical complexity. The results are demonstrated by considering two examples of sequence controllers. Finally, the limitations of the present work are presented along with possible extensions for future research.<>