A Petri-net-based collision and deadlock avoidance scheme for FMS

Automated manufacturing systems, including flexible manufacturing systems (FMSs), belong to the class of discrete event dynamic systems. In such a system, potentially conflicting events may occur due to concurrency. The problem of collision and deadlock avoidance can be investigated using Petri nets which are powerful techniques suitable for modeling concurrent processes. A Petri net based approach is employed in this paper to model, detect and avoid collisions and deadlocks in FMSs. Unlike the existing Petri net based techniques, the proposed approach uses the concept of critical states to avoid the system from entering a state leading toward a deadlock state. A multirobot assembly example is used to illustrate the proposed scheme