Setting acommonduedateinaconstrainedflowshop:Avariable neighbourhoodsearchapproach

In thispaperwestudyaduedatesettingprobleminaflowshoplayout.Theproblemconsistsof schedulingasetofjobsarrivingtothesystemtogetherwithjobsalreadypresent(denotedasoldjobs), in ordertosetacommonduedateforthenewjobs.Sincetheoldjobshaveacommonduedatethat must notbeviolated,ourproblemisareschedulingproblemwiththeobjectiveofminimisingthe makespanofthenewjobs(thusobtainingthetightestpossibleduedateforthenewjobs)anda constraintsincethemaximumtardinessoftheoldjobsmustbeequaltozero.Thisapproachleadstoan interestingschedulingprobleminwhichtwodifferentobjectivesareconsidered,eachoneforasubset of thejobsthatmustbescheduled.Tothebestofourknowledge,thistypeofproblemshavebeen scarcelyconsideredintheliterature,andonlyforveryspecificpurposes.Sinceourproblemisclearly NP-hard,anewheuristicbasedonvariableneighbourhoodsearch(VNS)hasbeendesigned. The computationalresultsshowthatourproposedheuristicoutperformstwoexistingheuristic methodsforsimilarproblemsintheliterature.