Bi-objective optimization research on integrated fixed time interval preventive maintenance and production for scheduling flexible job-shop problem

This paper investigates integrated flexible job shop problem (FJSP) with preventive maintenance (PM) activities under the multi-objective optimization approaches. Finding compromise solutions between the production objectives and maintenance ones is under consideration. In order to carry out the maintenance activities, reliability models are employed. This paper attempts to simultaneously optimize two objectives: the minimization of the makespan for the production part and the minimization of the system unavailability for the maintenance part. For doing it so, two decisions are taken at the same time: finding the appropriate assignment of n jobs on m machines in order to minimize the makespan and deciding when to execute the PM activities in order to minimize the system unavailability. Both the maintenance activity numbers and maintenance intervals are not fixed in advance. Four multi-objective optimization methods are compared to find the Pareto-optimal front in the flexible job-shop problem case. Promising the obtained results, a benchmark with a large number of test instances (more than 4800) and meticulous care is employed. (C) 2010 Elsevier Ltd. All rights reserved.