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VISUALFEEDBACKCONTROLOFAMICROLATHEHIROTAKAOJIMA1,KATSUHIROSAITO1,LIBOZHOU1,JUNSHIMIZU1,HIROSHIEDA11IBARAKIUNIVERSITYKEYWORDSMICROLATH,VISUALFEEDBACK,POSITIONCONTROLABSTRACTMICROMACHININGPROGRESSESRAPIDLYINRECENTYEARSINTHISRESEARCH,AMICROLATHEWHICHISINSTALLABLEANDOPERATIONALINSIDESEMVACUUMCHAMBERHASBEENDESIGNEDANDDEVELOPEDASAFIRSTSTEP,VISUALLYGUIDEDMICROLATHESYSTEMISDEVELOPEDWITHIMAGEOFCCDCAMERADEVICEINSTEADOFSEMIMAGEUNLIKETHECONVENTIONALFEEDBACKCONTROLWHICHPOSITIONSTHEXYTABLEONLY,THISSCHEMEOFFERSADIRECTCONTROLOFTHEPOSITION,PATHANDSPEEDOFTHETOOLTIPUSINGPROPOSEDMETHOD,CUTTINGEXPERIMENTWASACHIEVED,ANDITISCONFIRMEDTHATDEVELOPEDMICROLATHESYSTEMISEFFECTIVETODOCUTTING1INTRODUCTIONRECENTLY,THESYSTEMCAPABLEOFPRODUCINGTHEMICROPARTSAREREQUESTEDALONGWITHTHEMINIATURIZATION1MICROMACHININGPROGRESSESRAPIDLYINRECENTYEARSTHEEXPLORATORYRESEARCHHASAPPROACHEDTOALEVELOFACCESSINGASINGLEMOLECULEORATOMASADRIVINGFORCE,MEMSMICROELECTRONICMECHANICALSYSTEMHASBEENPLAYINGAMAJORROLEINMAKINGMICROCOMPONENTSANDDEVICESHOWEVER,MEMSISBASEDONTHEPHOTOLITHOGRAPHYTECHNOLOGYANDTHEREBYAPPLICABLEINTOLIMITEDMATERIALSSUCHASSILICONMONOCRYSTALLINEINORDERTOMEETTHEDEMANDSOFMINIATURIZATIONINELECTRONICANDOPTICALAPPLICATIONS,ALTERNATIVEMICROMACHININGTECHNOLOGYWHICHISABLETOACCESSAVARIETYOFMATERIALSINA3DIMENSIONALWAYISREQUIRED2MICROMESOMECHANICALMANUFACTURINGM4OFFERSACCESSIBILITYTODIFFERENTKINDSOFMATERIALACCORDINGTOEACHOBJECTIVE,ANDATTAINSHIGHREPEATABILITYANDACCURACYWITHTHELATESTULTRAPRECISIONMEANSTHEREARE,HOWEVER,MANYSCIENTIFICANDTECHNOLOGICALBARRIERSENCOUNTEREDINPRAGMATICIMPLEMENTATIONOFM4ONEOFTHEMISTHESURFACECHEMISTRYEFFECTSWHENMACHININGPARTSAREATMICROSCALE,ITISRECOGNIZEDTHATTHESURFACEAREATOVOLUMERATIOWILLBEINCREASEDINBOTHCHIPSANDTHERESULTINGPARTASCOMPAREDTOCONVENTIONALMACROMACHININGPROCESSANOTHERPROBLEMISTHEDIRECTMOTIONANDPOSITIONCONTROLSENSORSTHATARECAPABLEOFDIRECTLYMEASURINGTHERELATIVEDISPLACEMENTBETWEENTHETOOLANDWORKPIECEARENOTYETAVAILABLEINTHISRESEARCH,AMICROLATHEWHICHISINSTALLABLEANDOPERATIONALINSIDESEMVACUUMCHAMBERHASBEENDESIGNEDANDDEVELOPED3FIG1SHOWSTHECONCEPTSOFTHEDEVELOPEDMICROLATHEATSUCHOXYGENFREECONDITION,CUTTINGTESTSARECONDUCTEDTOUNDERSTANDSURFACECHEMISTRYEFFECTSONMICROMACHININGHOWEVER,SINCEDEVELOPEDMICROLATHEISSMALLINSIZE,RIGIDITYOFTHELATHEISLOWTHUSTHEPOSITIONOFTHETOOLOFTHELATHEISNOTABLETOBECONTROLLEDACCURATELYWITHACONVENTIONALMETHODWHICHCONTROLSXYTABLEONLYTHEREFORE,THEVISIONGUIDEDCONTROLMETHODISPROPOSEDTHEIMAGEFROMTHESEMSCANNINGELECTRONMICROSCOPEISDIGITIZEDBYCCDINTOPIXELSWITH8BITGRAYSCALESINCEEACHPIXELCONTAINS2DPOSITIONALINFORMATION,THEVISIONSYSTEMTHUSOFFERSANORTHOGONALCOORDINATEHEREAFTERREFERREDASTHEPIXELCOORDINATEFOROBJECTSINVIEWTOREFERTOTHEPIXELCOORDINATEISFREEFROMTHEMECHANICALINACCURACYANDOFFERSADIRECTMEASUREMENTOFSEMCCDMICROLATHEFIG1CONCEPTOFTHEDEVELOPEDMICROLATHEˆŠŠHOJIMA,KSAITO,LZHOU,JSHIMIZU,HEDATHERELATIVEPOSITIONOFTOOLANDWORKPIECETHERESOLUTIONINCREASESTOGETHERWITHTHEMAGNIFICATIONOFTHEMICROSCOPEANDTHENUMBEROFCCDPIXELSINTHISRESEARCH,AVISIONCONTROLSCHEMEHASBEENPROPOSEDANDIMPLEMENTEDFORFEEDBACKCONTROLOFTHETOOLMOVEMENTSUNLIKETHECONVENTIONALFEEDBACKCONTROLWHICHPOSITIONSTHEXYTABLEONLY,THISSCHEMEOFFERSADIRECTCONTROLOFTHEPOSITION,PATHANDSPEEDOFTHETOOLTIPASAFIRSTSTEP,VISUALLYGUIDEDMICROLATHESYSTEMISDEVELOPEDWITHIMAGEOFCCDCAMERADEVICEINSTEADOFSEMIMAGE2OVERVIEWOFSYSTEMACTUATINGMODULESENSINGMODULEPROCESSINGMODULEIMAGEINFORMATIONACTUATORSIGNALCAPTUREBOARDMICROLATHEXZSTAGEAMPCPUDIAMONDTOOLCCDWORKPIECED/ABOARDFIG2BLOCKDIAGRAMOFSYSTEMTABLE1SPECIFICATIONOFSYSTEMSIZEOFMICROLATHEWDH909042MMSPINDLEROTATIONALSPEED08000RPMDEPTHOFCUTTRAVERSEFEED1010MMCENTERHIGHADJUSTMENT30PMTOOLDIAMONDNOSEANGLE/NOSERADIUS40/2PMSCANNINGRATE20FRAME/STOTALPIXELS03MEGAPIXELSHOWNINFIG2ISTHEBLOCKDIAGRAMOFDEVELOPEDMICROLATHESYSTEM,WHICHCONSISTSOFTHREEMAINMODULES；THEACTUATINGMODULETHATDRIVESMICROLATHE,THESENSINGMODULETHATIMPORTSIMAGESANDTHEPROCESSINGMODULETHATIMPLEMENTSFEEDBACKCONTROLEACHMODULEISRESPONSIBLEFORDIFFERENTFUNCTIONTHEACTUATINGMODULEISTHECOREELEMENTWHERETHECUTTINGOPERATIONISCARRIEDOUTTHESENSINGMODULEIMPORTSIMAGESFROMCCDIMAGEDEVICE,ANDOBTAINSTHEPOSITIONOFTHETOOLANDTHEWORKPIECETHEOTHERTASKSINCLUDINGTHEIMAGEPROCESSINGANDFEEDBACKCONTROLAREEXECUTEDBYTHEPROCESSINGMODULEUPPERPICTUREOFFIG1SHOWSTHEOVERALLAPPEARANCEOFTHESYSTEMTABLE1SHOWSTHESPECIFICATIONSOFTHESYSTEMTHEACTUATINGMODULEFURTHERINCORPORATESADIAMONDTOOLWITHAXZLINEARSTAGE,ANDTHESENSINGMODULEINCLUDESAHIGHRESOLUTIONCCDIMAGEDEVICETHROUGHSENSINGMODULE,THEAPPEARANCEOFTHEWORKINGAREAISNOTONLYDISPLAYEDONTHEMONITORTOTHEGIVETHEOPERATORTHEVISUALINFORMATION,BUTALSOCONVERTEDINTODIGITALSIGNALFORSUBSEQUENTPROCESSINGASTHECONTROLDIAGRAMSHOWINFIG2,THEMOVEMENTSOFTHEDIAMONDTOOLAREGOVERNEDWITHTHEVISUALFEEDBACKCONTROLTHESENSINGMODULEFIRSTABSTRACTSTHEPOSITIONSOFTHETOOLANDWORKPIECEBYCOMPARINGTHEPREREGISTEREDTEMPLATESWITHTHECAPTUREDVISUALINFORMATIONCORRESPONDINGTOTHERELATIVEPOSITIONSOFTOOLANDWORKPIECE,THETOOLPATHANDSPEEDARECALCULATEDANDCONVERTEDINTOAPPROPRIATEPULSETRAINEGFHEFGHACBDABCDFIG4DRIVINGPRINCIPLEOFXZSTAGEXYZCENTERHIGHADJUSTMENTDCMOTORSPINDLEXZSTAGEMICROLATHEFIG3XZSTAGEANDMICROLATHE3ACTUATINGMODULETHEDEVELOPEDMICROLATHEISSHOWNRIGHTWARDINFIG3THISLATHECONSISTSOFTHEMAINSPINDLEWITHTHECOLLETCHUCKWITHTHEDCMOTOR,THECENTERHIGHADJUSTMENTUSINGAPIEZOELECTRICACTUATORANDXZSTAGEWHICHPERFORMSBOTHDEPTHOFCUTXAXISANDTRAVERSEFEEDZAXISTHEXZSTAGEISDRIVENBYTHEINERTIALSLIDING,ANDISCOMPOSEDOFAPIEZOELECTRICACTUATORANDTHELINEARGUIDEXZSTAGEISSHOWNLEFTWARDINFIG3ANACCURATETOOLPOSITIONINGISACHIEVEDBYDRIVINGTHEXZSTAGEPRECISELYIMPORTANTPOINTSOFDRIVINGTHEXZSTAGEARETHECONTROLOFTHEDRIVINGDIRECTION,DISTANCEANDVELOCITYFIGURE4SHOWSTHEINERTIALSLIDINGMECHANISMBYTHESAWTOOTHWAVETHEDIRECTIONOFTHEMOVEMENTISDECIDEDBYTHERISING/TRAILINGEDGEOFTHESAWTOOTHWAVEASSHOWNINFIG4FOREXAMPLE,ˆŠ‹VISUALFEEDBACKCONTROLOFAMICROLATHETHEMECHANISMINTHERIGHTDIRECTIONISEXPLAINEDASFOLLOWSTHEVOLTAGEGRADUALLYRISES,ANDAPIEZOELECTRICACTUATORSTRETCHESMOSTIN1THEACTUATORSHRINKSBASEDONTHECENTROIDIN2BYFALLINGRAPIDLYOFTHEVOLTAGEONLYTHESIDEWHERETHEFRICTIONALFORCEISSMALLMOVESASTHEACTUATORSTRETCHESGRADUALLYWITHTHEASCENTOFTHEVOLTAGEIN3THEACTUATORISSTRETCHESAGAININ4,ANDADVANCESTOWARDTHERIGHTDIRECTIONTHEACTUATORSIMILARLYADVANCESALSOTOWARDTHELEFTDIRECTIONIFAREVERSEPULSETRAINISGIVEN0010203040200400600FREQUENCYAHZSPEEDAMM/S80V40VFIG5VELOCITYCHANGEDEPENDINGONFREQUENCYANDVOLTAGENEXT,THEVELOCITYCONTROLOFTHISMECHANISMISDESCRIBEDASSHOWNINFIG5,THEVELOCITYISPROPORTIONALTOBOTHFREQUENCYOFTHEPULSETRAINANDDRIVINGVOLTAGEFINALLY,DRIVINGDISTANCECANBECONTROLLEDACCORDINGTOTHENUMBEROFPULSES,BECAUSETHEDRIVINGDISTANCEBYONEPLUSISABOUT500PMAT80VOR250PMAT40V500,420140,420500,60140,60XZ320,2404123FIG8EXPERIMENTALCONDITIONOFLINEARPATHCONTROLXPIXELZPIXELCOUNT210121011000200300400COUNTFIG7RECOGNITIONACCURACYOFTOOLTIPXZSTAGEDIAMONDTOOLCCDWORKPIECEX,ZZXFIG6VISUALSENSINGSYSTEM4SENSINGMODULETHEDIAMONDTOOLISMOUNTEDONXZSTAGE,WHICHUSESPIEZOELECTRICACTUATORTODRIVETOOLTHOSEMECHANICALINACCURACIES,MAINLYCAUSEDBYTHERMALEXPANSION,HYSTERESIS/DRIFTINACTUATORSANDMISALIGNMENTOFORTHOGONALAXIS,MAYDIRECTLYDELIVERANEGATIVEEFFECTTOTHESYSTEMPERFORMANCETOSOLVETHESEPROBLEMS,AVISIONCONTROLSCHEMEASSHOWNINFIG6ISDEVELOPEDTHELEFTPICTUREINFIG6SHOWSTHEMICROLATHEANDCCDIMAGEDEVICELOCATEDINYAXISFROMTHERIGHTPICTUREINFIG6,THEINCOMINGVISUALINFORMATIONFROMTHECCDISDIGITIZEDINTOPIXELSWITH8BITGRAYSCALEBYTHESENSINGMODULEASEACHPIXELBEARS2DPOSITIONALINFORMATION,THEVISIONSYSTEMTHUSOFFERSANORTHOGONALCOORDINATEREFERREDASTHEPIXELCOORDINATEFOROBJECTSINVIEWTOREFERTOTHEPIXELCOORDINATEISFREEFROMTHEMECHANICALINACCURACYANDITSRESOLUTIONINCREASESTOGETHERWITHTHEMAGNIFICATIONOFTHECCDATA480640PIXELFRAMEUSEDINTHECURRENTRESEARCH,FOREXAMPLE,THERESOLUTIONOFTHEPIXELCOORDINATEISABOUT6PMWHENTHEVIEWOFTHECCDISTWOFOLDMAGNIFIEDWHENTHECCDISALIGNEDALONGYAXIS,THEPOSITIONOFTHETOOLTIPANDWORKPIECEISPROJECTEDINTOA2DPIXELCOORDINATEXZWHICHISCOMMONLYSHAREDBYTHEXZSTAGEANDWORKPIECEDRIVENANDCONTROLLEDBYTHEPIXELCOORDINATE,THETOOLISABLETOBEPOSITIONEDANDMOVEDATTHEACCURACYOFPIXELRESOLUTIONWITHNOEFFECTBYTHEMECHANICALINACCURACYINADDITION,IFTHERIGIDITYBETWEENXZSTAGEANDTOOLISLOW,POSITIONINGOFTOOLTIPISNOTACHIEVEDBYDRIVINGXZSTAGEACCURATELYTHUS,MOREIMPORTANTLY,THISOPERATIONISANEFFECTIVEMETHODOFPOSITIONINGFORTHEMICROLATHEWITHALOWRIGIDITYFIGURE7SHOWSTHERECOGNITIONACCURACYTHATISMADEBYUSEOFSHAPEBASEDPATTERNMATCHING4TORECOGNIZETHEACTUALTOOLTIPREPEATEDLY500TIMESWECOMPREHENDFROMTHEGRAPHTHAT885RELIABILITYCANBEACHIEVEDWITHINTHELIMESOF1PIXEL6PM5PROCESSINGMODULEFORTHESYSTEMWHICHISCONSISTEDOFTHEACTUATINGANDSENSINGMODULEINPREVIOUSSECTION3AND4,THEVISUALˆŠŒHOJIMA,KSAITO,LZHOU,JSHIMIZU,HEDAFEEDBACKCONTROLMETHODISDESCRIBEDINTHISSECTIONTHETOOLTIPISDRIVENBYVISUALFEEDBACKCONTROLMETHODWITHPOSITIONSOFTHETOOLTIPANDTARGETSFROMCCDIMAGEDEVICEASAFIRSTSTEP,WEEXAMINEDLINEARPATHCONTROLANDCIRCULARPATHCONTROLOFTHETOOLTIPINTHESEPATHCONTROLS,DRIVINGFREQUENCYIS300HZ162PM/SATFIRST,LINERPATHCONTROLOFTOOLTIPISDESCRIBEDASSHOWNINFIG8,THETARGETPOSITIONISDEFINEDAS320,240WHICHISTHECENTEROFTHEIMAGEFROMCCD,ANDFOURKINDSOFPATHCONTROLAREEXAMINEDINTHECASEOFLINERPATHCONTROL,THEANGLEFORMEDBYTHETARGETPOSITIONANDTHEPRESENTPOSITIONOFTHETOOLTIPISFEDBACKTOACHIEVETHEPATHCONTROLFIGURE9ASHOWSTHERESULTANTPATHOFTHETOOLTIPWITHOUTFEEDBACKCONTROL,ANDBSHOWSTHATWITHFEEDBACKCONTROLINTHECASEOFTHEPATHWITHOUTFEEDBACK,FINALERRORSOFFOURPATHSAREBETWEEN5PIXELS30PMAND15PIXELS90PMONTHEOTHERHAND,THEPATHWITHFEEDBACKFOLLOWSALONGTHETARGETPATH,ANDFINALERRORISWITHIN2PIXELS12PMNEXT,THECIRCULARPATHCONTROLWHICHISMULTIAXIALINTERPOLATIONISDESCRIBEDTHECONDITIONOFTHECIRCULARPATHCONTROLISSHOWNINFIG10THECENTEROFTHETARGETCIRCULARPATHISDEFINEDAS320,240WHICHISTHECENTEROFTHEIMAGEFROMCCD,ANDTHERADIUSOFTHETARGETPATHIS100PIXELS600PM,MOREOVERTHETOOLTIPISDRIVENFROMSTARTINGPOINT220,240ALONGCOUNTERCLOCKWISEDIRECTIONREPEATED3TIMESINTHECASEOFCIRCULARPATHCONTROL,WECONSIDERTOFEEDBACKNOTONLYTHEANGLEFORMEDTHECENTEROFTHETARGETCIRCULARPATHANDTHEPRESENTTOOLPOSITION,BUTALSOTHEDEVIATIONOFTHERADIUSWHICHISTHEERRORBETWEENTHERADIUSOFTHETARGETCIRCULARPATHANDTHEDISTANCEFROMTHECENTEROFTHETARGETPATHTOTHEPRESENTTOOLPOSITIONINTHECASEOFTHEDRIVINGTHEPATH