A rule-based evaluation of ladder logic diagram and timed petri nets for programmable logic controllers

This paper describes an evaluation through a case study by measuring a rule-based approach for designing sequence controllers. The increasing complexity and functionality of modern discrete event manufacturing systems have challenged the traditional tools and design methods based on ladder logic diagrams (LLDs) for designing programmable logic controllers (PLC). Furthermore, while the complexity and functionality of manufacturing systems increases, designing flexible, reusable, and maintainable control software becomes more difficult. Petri nets as a high level specification language are an emerging technique in designing control software systems for complex manufacturing systems. It is used for modeling, analysis and simulation of industrial automated systems. The proposed rule based approach tends to a unified measurement. This is performed in three levels. System complexity increases in a step by step and incremental fashion level by level. We have shown that, when the levels are more complex, Petri nets are more tractable and more verifiable. Moreover, it can be concluded that Petri nets are more efficient than ladder logic diagrams in designing control software systems.