Abstract
In industrial situation such as FMS, there arises a need to optimize a schedule for a repetitive process in which one process assigns n jobs to m machines according to the prescribed ordering, e.g. a flow-shop or a job-shop problem, and the process is repeated many times.
In this paper, a Time Petri Net (TPN) is applied to a job-shop type repetitive process to obtain the time-suboptimal (non-delayed) schedule. The method is based on a reachable tree including time and the fact that the natural firing rule for TPN corresponds to a generation of a non-delayed schedule.
Then, based on the above result, the optimal restoring strategies are investigated which can be applied when the process undergoes an emergency stop and make a fresh start to restore to the above repetitive schedule after repairing.
Two cases are considered for restoring conditions. The results are illustrated by computer simulations.
