An incremental approach to logic controller design with Petri nets

A conceptual and practical methodology is proposed for designing logic control systems with Petri nets. The main objectives are to reduce the design effort due to the complexity of control problems and to provide design criteria that perfectly fit the fundamental engineering approach to complexity, namely incremental design. The methodology is based on concepts coming from a number of theorems stated and proved. The designer is then provided with powerful basic net structures, implementing single control tasks, and with useful connections to coordinate and synchronize these tasks. This enables the designer to solve simple control problems and aggregate separate designs to form a more complex structure. Simple rules are provided that guarantee the preservation, after the merging of previous designs, of important net properties, like boundedness, cyclicness, and lifeness. To do so, it is sufficient to analyze an opportune graph based on the connections among tasks