SIMULATION MODELING OF A DYNAMIC JOB-SHOP RESCHEDULING WITH MACHINE AVAILABILITY CONSTRAINTS

In this paper we study dynamic job shop rescheduling where machine wor kstations are not always available due to breakdown or preventative ma intenance. A visual interactive simulation model using the AWESIM disc rete event modeling tools was constructed to show how the state depend ent rescheduling technology is used. Heuristics have been refined in o rder to include job shop state variable information. It was found that the job shop rescheduling problem can be simplified by understanding the state of the entire job shop and using this state knowledge to seq uence jobs in work station queues. We develop the PMBD heuristic that relies only on predicted downstream machine failure times and we compa re it with other conventional heuristics that are modified to use job shop state information. (C) 1998 Elsevier Science Ltd. All rights rese rved.