Avoiding deadlocks in automated manufacturing systems with shared material handling system

The problem of avoiding deadlocks in automated manufacturing systems with the material handling system considered is addressed in this paper. The operation process of moving a part from one place to another place by the material handling system consists of three actions: picking the part up, moving to the destination place and putting the part down. We model these three actions together as an event by a transition in a Petri net model. This model is combined with the author´s colored resource-oriented Petri net (1995) [CROPN]. Based on the model, necessary and sufficient condition for deadlock avoidance and control law are presented when the material handling system is also considered. The control law guarantees the maximal use of the buffer spaces in the system while the deadlock is completely avoided. An illustrative example is taken to show the application of the proposed approach