Heuristics for dynamic job shop scheduling with real-time updated queueing time estimates

The queueing times of the jobs in a dynamic job shop normally account for the major portion of their lead times. Hence, the criticality of a job cannot be accurately determined without some knowledge regarding the expected total queueing time for its remaining operations. A new approach is developed in this study to provide real-time estimates of the queueing times for the remaining operations of the jobs in the dynamic job shop and to incorporate this estimated queueing time information into existing scheduling heuristics to improve their performance. The results of a computational experiment indicate that, by applying the new procedure to estimate and to take the jobs' queueing times into consideration, the scheduling heuristics developed in this study have achieved statistically significant improvement over their counterparts on due-date related performance measures in almost all shop conditions studied.