| Abstract: | Deadlock avoidance problems are investigated for automated manufacturing systems with flexible routings.
Based on the Petri net models of the systems, this paper proposes, for the first time, the concept of perfect maximal resourcetransition
circuits and their saturated states. The concept facilities the development of system liveness characterization and
deadlock avoidance Petri net supervisors. Deadlock is characterized as some perfect maximal resource-transition circuits
reach their saturated states. For a large class of manufacturing systems, which do not contain center resources, the optimal
deadlock avoidance Petri net supervisors are presented. For an general manufacturing system, a method is proposed for
reducing the system Petri net model so that the reduced model does not contain center resources and, hence, has optimal
deadlock avoidance Petri net supervisor. The controlled reduced Petri net model can then be used as the liveness supervisor
of the system. |
