Conversion of Petri net controllers for manufacturing systems into ladder logic diagrams

As automated manufacturing systems become more complex, the need for an effective design tool to produce both high level discrete event control system (DECS) and low level implementation, becomes increasingly more important. Petri nets represent the most effective method for both the design and implementation of DECSs. The conversion of such Petri nets into real-time applications has recently been greatly simplified through the advent of the token-passing logic (TPL) methodology. The technique has been developed for normal Petri nets, P-timed Petri nets, T-timed Petri nets and coloured Petri nets. In this paper the Petri net concepts are extended to deal with Petri net controllers, by including actuators and sensors as formal structures within the Petri net controller. The conversion of such a Petri net controller into ladder logic diagrams is also demonstrated by considering the control of a component sorting manufacturing system.