Design of sequence controllers using Petri net models

Current research in flexible automation indicates that ladder logic diagrams (LLDs) are inefficient to develop control software and difficult to debug and maintain. To overcome the disadvantages of LLDs, Petri nets (PNs) were developed and demonstrated as an effective tool for logic controller design by several researchers and industrial practitioners. One critical task in this development is to design Petri net models given the sequence control specifications. Development of such a PN model is the first step to develop Petri net based sequence controllers. There exists systematic design procedures for designing ladder logic diagrams. However, for the large scale application of PNs in industry, there is a need for systematic design procedures for developing PN models. This paper presents a simple conversion procedure to formulate PN models from a given logic control specification