An impending deadlock-free scheduling method in the case of unified automated material handling systems in 300 mm wafer fabrications

摘要

Impending deadlock is difficult to detect on the track of the unified automated material handling systems in 300 mm wafer fabrications, and has been less examined. This paper proposes an impending deadlock detection model using a graphic formulation with new concepts of critical chains and shared nodes. A novel controlling method is presented to ensure critical chains have at least one empty node and sequence the OHTs' entry of the shared nodes. This method is easy to apply and features real-time operation and large-scale systems. The effectiveness and efficiency of the proposed method is confirmed by simulation experiments.