A comparative performance analysis of deadlock avoidance control algorithms for FMS

A deadlock condition for flexible manufacturing systems is characterized by a set of parts, which have been processed but cannot be discharged by a set of machines or buffers. To avoid such problems, it is necessary to adopt suitable control policies which limit the resource allocation in the system, thus affecting the overall system performance. In the present work, we address the problem of evaluating and comparing the performance of deadlock avoidance control policies applied to FMS. The problem is discussed for both untimed and timed models, and for models both with and without deadlock avoidance control policies. Different control algorithms, among the most common in the literature, have been considered. Imperfect deadlock avoidance control policies are also considered. In addition, some indices are proposed to assess the structural properties of FMS with respect to deadlock occurrence and their performance. Two different application examples are analyzed, with the help of a commercial simulation package. Finally, an adaptive algorithm which can learn from system evolution to avoid deadlocks is illustrated.