Synthesis of feedback control logic for a class of controlled Petri nets

Real-world applications of the emerging theory of controlled discrete event systems (DES’s) will not be realized until the obstacle computational complexity is overcome. This paper presents a step in that direction by developing an efficient solution for a class of forbidden state problems. We consider DES’s which can be modeled as cyclic controlled marked graphs (CMG’s), a special class of controlled Petri nets (CPN’s). The distributed representation of the DES state in terms of the CMG marking permits an efficient specification of the forbidden states in terms of individual place markings. More importantly, we show that the graphical representation of the state transition logic in a CMG can be used to synthesize state feedback logic which is maximally permissive while guaranteeing the forbidden states will not occur. The practical application of the theoretical results is illustrated for an example of automated guided vehicle (AGV) coordination in a flexible manufacturing facility.