毕业设计外文翻译-用蚁群算法在刀库索引位置的优化配置.docx

毕业设计外文翻译-用蚁群算法在刀库索引位置的优化配置.docx

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Optimalallocationofindexpositionsontoolmagazinesusinganantcolonyalgorithm

AbstractGenerationofoptimalindexpositionsofcuttingtoolsisanimportanttasktoreducethenon-machiningtimeofCNCmachinesandforachievementofoptimalprocessplans.Thepresentworkproposesanapplicationofanantcolonyalgorithm,asaglobalsearchtechnique,foraquickidentificationofoptimalornearoptimalindexpositionsofcuttingtoolstobeusedonthetoolmagazinesofCNCmachinesforexecutingacertainsetofmanufacturingoperations.Minimisationoftotalindexingtimeistakenastheobjectivefunction.

KeywordsIndexingtime.Automatictoolchange.CNCmachine.Optimization.Antcolonyalgorithm

1Introduction

Intoday’smanufacturingenvironment,severalindustriesareadaptingflexiblemanufacturingsystems（FMS）tomeettheever-changingcompetitivemarketrequirements.CNCmachinesarewidelyusedinFMSduetotheirhighflexibilityinprocessingawiderangeofoperationsofvariouspartsandcompatibilitytobeoperatedunderacomputercontrolledsystem.TheoverallefficiencyofthesystemincreaseswhenCNCmachinesareutilizedtotheirmaximumextent.Sotoimprovetheutilization,thereisaneedtoallocatethepositionsofcuttingtoolsoptimallyonthetoolmagazines.

ThecuttingtoolsonCNCmachinescanbechangedorpositionedautomaticallywhenthecuttingtoolsarecalledwithinthepartprogram.TodothisturretsareusedinCNClathemachinesandautomatictoolchangers（ATC）inCNCmillingmachines.ThepresentmodelcanbeusedeitherfortheATCmagazinesorturretsonCNCmachines.

Theindexingtimeisdefinedasthetimeelapsedinwhichaturretmagazine/ATCmovesbetweenthetwoneighbouringtoolstationsorpockets.Bi-directionalindexingofthetoolmagazineisalwayspreferredoveruni-directionalindexingtoreducethenon-machiningtimeofthemachine.Inthisthemagazinerotatesinbothdirectionstoselectautomaticallythenearerpathbetweenthecurrentstationandtargetstation.Thepresentworkconsidersbi-directionalmovementofthemagazine.Inbidirectionalindexing,thedifferencebetweentheindexnumbersofcurrentstationandtargetstationiscalculatedinsuchawaythatitsvalueissmallerthanorequaltohalfofthemagazinecapacity.

Derelietal.[1]formulatedthepresentproblemasa“travelingsalesmanproblem”（TSP）,whichisNPcomplete.Theyappliedgeneticalgorithms（GA）tosolvetheproblem.Dorigoetal.[2,3]introducedtheantcolonyalgorithm（ACA）forsolvingtheNP-completeproblems.ACAcanfindthesuperiorsolutiontoothermethodssuchasgeneticalgorithms,simulatedannealingandevolutionaryprogrammingforlarge-sizedNP-completeproblemswithminimumcomputationaltime.So,ACAhasbeenextendedtosolvethepresentproblem.

2Methodology

Determinationoftheoptimalsequenceofmanufacturingoperationsisaprerequisiteforthepresentproblem.Thissequenceisusuallydeterminedbasedonminimumtotalset-upcost.Theauthors[4]suggestedanapplicationofACAtofindtheoptimalsequenceofoperations.Oncethesequenceofoperationsisdetermined,thefollowingapproachcanbeusedtogettheoptimalarrangementofthetoolsonthemagazine.

Step1Initiallyasetofcuttingtoolsrequiredtoexecutethefixed（optimal）sequenceofthemanufacturingoperationsisassigned.Eachoperationisassignedasinglecuttingtool.Eachtoolischaracterizedbyacertainnumber.Forexample,letthesequenceofmanufacturingoperations{M1-M4-M3-M2-M6-M8-M9-M5-M7-M10}beassignedtothesetofcuttingtools{T8-T1-T6-T4-T3-T7-T8-T2-T6-T5}.Thesetoftoolscanbedecodedas{8-1-6-4-3-7-8-2-6-5}.HerethemanufacturingoperationM1requirescuttingtool8,M4requires1andsoon.Intotalthereareeightdifferenttoolsandthuseightfactorialwaysoftoolsequencespossibleonthetoolmagazine.

Step2ACAisappliedastheoptimizationtooltofindthebesttoolsequencethatcorrespondstotheminimumtotalindexingtime.Foreverysequencethatisgeneratedbythealgorithmthesamesequenceofindexpositions（numbers）isassigned.Forexample,letthesequenceoftools{4-6-7-8-2-5-3-1}begeneratedandhenceassignedtotheindexingpositions{1-2-3-4-5-6-7-8}inthesequentialorder,i.e.tool4isassignedtothe1stposition,tool6tothe2ndpositionandsoon.

Step3Thedifferencesbetweentheindexnumbersofsubsequentcuttingtoolsarecalculatedandthentotaledtodeterminethetotalnumberofunitrotationsforeachsequenceofcuttingtools.Absolutedifferencesaretobetakenwhilecalculatingthenumberofunitrotationsrequiredfromcurrenttooltotargettool.Thisfollowingsectiondescribesanexampleindetail.

ThefirsttwooperationsM1andM4inthepre-assumedfixedsequenceofoperationsrequirethecuttingtools8and1,re