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131CLOSEDLOOPSENSORSYSTEMFORAUTOMATEDMANUFACTURINGMACHINESAASHAIK1,GBRIGHT2ANDWLXU31COUNCILFORSCIENTIFICANDINDUSTRIALRESEARCH,MATERIALSCIENCEANDMANUFACTURING,SOUTHAFRICA,ASHAIKCSIRCOZA2UNIVERSITYOFKWAZULUNATAL,SCHOOLOFMECHANICALENGINEERING,SOUTHAFRICA,BRIGHTGUKZNACZA3MASSEYUNIVERSITY,INSTITUTEOFTECHNOLOGYANDENGINEERING,NEWZEALAND,WLXUMASEYACNZABSTRACTMANYAUTOMATEDMULTIAXISMACHINESOPERATEUNDEROPENLOOPCONTROLTHEEXACTPOSITIONINSPACEOFTHEENDEFFECTERORTOOLHEADISNOTSENSEDDIRECTLYTHESOFTWARECONTROLLINGTHEROBOTSORAUTOMATEDMANUFACTURINGMACHINESMAKEACALCULATEDESTIMATEOFWHERETHETOOLHEADSHOULDBETHISISOFTENACHIEVEDBYMONITORINGSENSORSONAXESTHATTRACKLINEARTRANSLATIONANDROTATIONSOFSHAFTSORGEARSFORLOWPRECISIONAPPLICATIONSTHISSYSTEMISAPPROPRIATEHOWEVER,POSITIONALERRORSOFTENOCCURTHISMETHODMAYNOTBESUITABLEFORHIGHPRECISIONROBOTSANDAUTOMATEDMACHINETOOLSTHEREEXISTSANEEDFORASENSORSYSTEMTHATISCAPABLEOFACQUIRINGTHEEXACTSPATIALCOORDINATESOFTHETOOLPOINTORENDEFFECTORDIRECTLYTHEAIMOFTHISRESEARCHPROJECTWASTODESIGNALOWCOSTSENSORSYSTEMTHATWOULDPRECISELYLOCATETHETOOLPOINTSSPATIALCOORDINATESDIRECTLYBYCLOSEDLOOPCONTROLTHISAIDEDINTHEREDUCTIONOFERRORSENCOUNTEREDINOPENLOOPCONTROLTHESYSTEMWASCAPABLEOFSEAMLESSINTEGRATIONWITHEXISTINGTECHNIQUESFORMOTIONCONTROLTHESENSORSYSTEMWASABLETOLOCATETHETOOLHEADIN2DSPACEWITHSIMPLEADDITIONSANDMODIFICATIONSITRENDEREDITSELFAPPLICABLETO3DSPACELOCATIONOFTHETOOLHEADITWASMODULAR,SUFFICIENTLYROBUSTANDERRORIMMUNESUCHTHATITWOULDWORKINALMOSTANYENVIRONMENTKEYWORDSAUTOMATION,MANUFACTURING,CLOSEDLOOPCONTROL1INTRODUCTIONTHENEEDFORASENSORSYSTEMTHATPROVIDESDIRECTFEEDBACKOFTHEENDEFFECTORSSPATIALCOORDINATESISESSENTIALFORPRECISEASSEMBLYANDMACHININGTHEOBJECTIVEOFTHISRESEARCHPROJECTWASTODESIGNAPARALLELROBOTTHATWOULDHAVEANINTEGRATEDSENSORSYSTEMTHESENSORSYSTEMSHOULDBELOWCOSTANDBECAPABLEOFLOCATINGTHETOOLPOINTSSPATIALCOORDINATESDIRECTLYORAIDINREDUCINGTHEERRORSENCOUNTEREDINTHEOPENLOOPCONTROLTHESYSTEMSHOULDBECAPABLEOFSEAMLESSINTEGRATIONWITHEXISTINGTECHNIQUESFORMOTIONCONTROLANDSHOULDBEABLETOLOCATETHETOOLHEADIN2DSPACEWITHSIMPLEMODIFICATIONSITSHOULDRENDERITSELFAPPLICABLETOLOCATIONIN3DSPACEITSHOULDBEMODULAR,SUFFICIENTLYROBUSTANDERRORIMMUNETOWORKINALMOSTANYENVIRONMENTTHEREARENUMEROUSTECHNOLOGIESAVAILABLEFORTHEPURPOSEOFLOCATINGOBJECTSINSPACETHESEARETHEGLOBALPOSITIONINGSYSTEMGPSWITH10MACCURACY,ADIFFERENTIALGPSSOLUTIONBY1REDUCESTHEERRORSTOLESSTHAN5CMPROXIMITYLOCATIONTHROUGHBLUETOOTH,WIFIANDCELLULARNETWORKSPOSITIONISDEDUCEDBYKNOWINGTHECELLWITHWHICHADEVICEISCOMMUNICATINGANDTRIANGULATIONSYSTEMSUSINGLASERS,ULTRASOUND,ETCINADDITIONTHEREAREIMAGINGMETHODSUSEDTODETERMINEPOSITION2DISCUSSESALOWCOSTSOLUTIONEMPLOYINGACAMERAANDLCDLIQUIDCRYSTALDISPLAYSCREENTOLOCATEANOBJECTSCOORDINATESIN2DWITHHIGHACCURACYVSLAMVISUALSIMULTANEOUSLOCATIONANDMAPPINGSYSTEMSUSEDINMOBILEROBOTICSUSECAMERASTOBUILDAMAPOFITSSURROUNDINGSFORNAVIGATIONPURPOSESTHEREAREALSOIMAGEPROCESSINGTECHNIQUESTHATCANDETERMINEMOVEMENTFROMCONSECUTIVEFRAMESPROVIDEDBYACAMERATHESEIMAGESALSOPROVIDEINFORMATIONREGARDINGTHESURROUNDINGSANDARECOMPLETELYPASSIVETHEACCURACYANDRESOLUTIONHOWEVERDEPENDONHOWFARFROMTHEOBJECTTHECAMERAISANDTHERESOLUTIONOFTHECAMERAITSELFALLTHESETECHNOLOGIESARESUITABLEFORLOCATINGLARGEOBJECTSINARELATIVELYLARGESPACE,FORINSTANCELOCATINGPEOPLEINBUILDINGS3ININDUSTRY,HOWEVER,ROBOTICARMSUSEDFORASSEMBLY,WELDINGORSPRAYPAINTINGMOVEINACONFINEDSPACEANDTHEPOSITIONOFTHEENDEFFECTORMUSTBEDETERMINEDWITHMILLIMETERTOSUBMILLIMETERRESOLUTIONFORMANUFACTURINGPURPOSESTHERESOLUTIONOFCOMPUTERNUMERICALLYCONTROLLEDCNCMACHINESRANGEFROMMICROMETERSTONANOMETERSFORSUCHPURPOSESLASERINTERFEROMETERTECHNOLOGIESARESOMETIMESUSEDTHESEPOSITIONSENSINGSYSTEMSHAVEEXCELLENTRESOLUTIONASWELLASACCURACYANDAREUSEDINMANUFACTURINGENVIRONMENTSFORICINTEGRATEDCIRCUITDESIGN,PROTOTYPINGANDMANUFACTURINGANOPTICALHETERODYNEINTERFEROMETERDESIGNEDATNASASJETPROPULSIONLABORATORYCANMEASURELINEARDISPLACEMENTSWITHANERROROF20PMPICOMETERS,1012MGRIDENCODERSOFFERANOTHERSOLUTIONGRIDSMADEBYOPTRAHAVEACOVERAGERANGEUPTO380MM380MMTHEIRACCURACYANDREPEATABILITYLIEINTHESAMERANGEASLASERINTERFEROMETERSIEMICROTONANOMETERRESOLUTIONBOTHGRIDENCODERSANDLASERINTERFEROMETERSAREEXPENSIVETECHNOLOGIES,USUALLYCOSTINGHUNDREDSOFTHOUSANDSTOMILLIONSOFDOLLARSFURTHERMORE,THEYCANNOTMEASUREABSOLUTEPOSITIONDIRECTLYTHEYBOTHUSEFRINGEPATTERNSDUETOLIGHTWAVEINTERFERENCETOMEASURERELATIVEDISPLACEMENTTHEINTEGRATIONOFTHESEDISPLACEMENTMEASUREMENTSCOUPLEDWITHTHEKNOWLEDGEOFTHEENDEFFECTORSINITIALPOSITIONYIELDSTHECURRENTPOSITION308AASHAIK,GBRIGHTANDWLXU2PROPOSEDSENSORFEEDBACKSYSTEMTHEPROBLEMOFLOCATINGTHEENDEFFECTOROFAROBOTINREALWORLDSPACEISFIRSTREDUCEDTOFINDINGITSPOSITIONINA2DPLANEWITHREGARDTOAPOINTREFERENCETHEGENERALPROBLEMOFLOCATIONIN3DSPACEISSOLVEDBYATTACHINGTWO2DPLANESATRIGHTANGLESWITHSUCHANARRANGEMENT2AXESCOINCIDEANDIFTHEREFERENCEPOINTOFEACHPLANECOINCIDES,THERESULTISA3AXISSENSORSYSTEMFORPOSITIONLOCATIONTHISPAPERATTEMPTSTODOCUMENTASOLUTIONOFFINDINGTHEENDEFFECTORINA2DPLANEAFTERCONSIDERATIONOFTHEAVAILABLEPHYSICALQUANTITIESULTRASOUND,INFRAREDLIGHT,RADIOWAVES,ETCUSEDWHENLOCATINGOBJECTS,ITWASDECIDEDTHATALASERWOULDBEMOSTSUITABLEFORTHEREASONSTHATFOLLOWALASERLIGHTSENSORCANBECONDITIONEDTOPROVIDEADIGITALOUTPUTCOMPARATIVELYANALOGUESENSORSREQUIREDIGITIZATIONFORUSEINDIGITALSYSTEMSANALOGUESIGNALSARECOMPROMISEDBYATMOSPHERICEFFECTS,TEMPERATURE,HUMIDITYANDUNSHIELDEDNOISEFROMSURROUNDINGMACHINERYTRIANGULATIONUTILIZINGRADIO,ULTRASOUNDORINFRAREDWAVESISNOTSUITABLEASMULTIPLEREFLECTIONSFROMSURROUNDINGSURFACESCAUSEINTERFERENCEANDPROVIDEUNRELIABLERESULTSTHEYALSOREQUIREMODULATIONANDDEMODULATIONTODISTINGUISHTHESIGNALSGENERATEDFROMANYTHATCANBECREATEDBYTHEENVIRONMENTTHEPROPOSEDSENSORCONCEPTUTILIZESADIRECTAPPROACH,WITHALASERATTACHEDTOTHEENDEFFECTORANDASENSORGRIDAGRIDOFLASERSENSORSEQUALLYSPACEDINROWSANDCOLUMNSMOUNTEDDIRECTLYABOVEITTHISISANATURALCHOICEASTHECOHERENTNATUREOFLASERLIGHTMAKESFINDINGTHEENDEFFECTORIN2DSPACEEASYIFTHELASERBEAMREMAINSPERPENDICULARTOTHESENSORPLANEATALLTIMESTHEENDEFFECTORSLOCATIONISTHESAMEASTHESENSORWHICHISSTIMULATEDINA2DPLANE,DEPTHHASNOMEANINGTHISPERPENDICULARCONSTRAINTCANBEENFORCEDBYTHEUSEOFTILTSENSORSTHATCANTELLTHEORIENTATIONOFANOBJECT,CORRECTIONSCANTHENBEMADETOKEEPTHEENDEFFECTORPERPENDICULARALSOTHEINHERENTNATUREOFTHEROBOTCANBESUFFICIENTTOFORCETHISCONDITIONTHEFLEXPICKERISONESUCHEXAMPLEASITSARMSFORCETHEENDEFFECTORTOREMAINPARALLELTOITSBASEATALLTIMESITMUSTBESTRESSEDTHATTHISSENSORSYSTEMREQUIRESONLYBIT1OR0INFORMATIONFOREACHSENSOREACHSENSORISEITHERSTIMULATEDORNOTSTIMULATEDTHISMAKESDATAPROCESSINGANDTRANSFERFARSIMPLERANDMAKESCONTROLEASIERTHERESOLUTIONISLIMITEDTOTHESPACINGBETWEENSENSORSIFTHESPOTLIGHTISSMALLERTHANTHESPACINGBETWEENSENSORS,THESEWILLREPRESENTADEADZONEWHEREBEAMTRACKINGWILLBELOSTCOMPLETELYTHELASERLIGHTDETECTORSAREPHOTOTRANSISTORSWITHADARLINGTONCONFIGURATIONCURRENTFABRICATIONTECHNIQUESCANACCOMMODATEMILLIONSOFTRANSISTORSONASLIVEROFSILICONTHESEFABRICATIONMETHODSCANBEUSEDTOCONSTRUCTADETECTORSCREENWITHANEXCEPTIONALANDPRACTICALRESOLUTIONRESOLUTIONAFFECTSDATAOUTPUT,AGREATERRESOLUTIONIMPLIESMOREDATAPERUNITAREAMORESENSORSAHYBRIDTYPESYSTEMWOULDINVOLVEASENSORGRIDWITHACOMPARATIVELYLOWERRESOLUTIONEACHSENSORPROVIDESACHECKPOINTKNOWINGTHEEXACTSPATIALDISTANCEBETWEENTHESEDETECTORSPROVIDESTHECONTROLLERAMEANSTOLIMITTHEERRORSINCURREDINSTEADOFACCUMULATINGERRORSFROMONEEXTREMITYTOTHENEXT,ERRORSONLYEXISTBETWEENSUCCESSIVEDETECTORSFIGURE11BLOCKDIAGRAMOFINTENDEDSENSORSYSTEM3MECHATRONICDESIGNTHEMECHATRONICDESIGNCONSISTSOF3PARTSTHEMECHANICAL,ELECTRONICANDSOFTWARECOMPONENTSASSTATEDIN4,THETERMMECHATRONICSISUSEDFORTHEINTEGRATIONOFMICROPROCESSORCONTROLSYSTEMS,ELECTRICALSYSTEMSANDMECHANICALSYSTEMSTHEMECHANICALSTRUCTUREWASDESIGNEDTOTESTTHEELECTRONICHARDWAREANDSOFTWARECONTROL,THEPURPOSEOFWHICHISTOVALIDATETHEPROPOSITIONTHEMECHANICALDESIGNWASALSOUNDERTAKENTOEXPLOREPARALLELMECHANISMSTHEDESIGNISDOCUMENTEDTODELIVERASIMPLEPROTOTYPETHESPECIFICATIONONRESOLUTIONWASRELAXEDASITWASSTATEDTHATFABRICATIONTECHNIQUESCANPRODUCEASCREENWITHAREALISTICRESOLUTIONMOREEMPHASISWASPLACEDONCREATINGACHEAPSYSTEMTHATCOULDREDUCEERRORSMECHANICALSTRUCTURETHEMECHANICALSTRUCTUREISBASEDONAFLEXPICKERPICKANDPLACEPARALLELKINEMATICSINDUSTRIALROBOTITISASCALEDADAPTATIONTHEDESIGNCONSISTSOF4ARTICULATEDARMS4SERVOMOTORSAPLATEENDEFFECTORWITHATTACHEDLASERBALLCUPJOINTSANDAMOUNTINGFRAMETHEENTIREMECHANICALSTRUCTUREIS600MMINLENGTH,400MMWIDEAND500MMHIGHFIGURES12AND13ILLUSTRATETHEPARTSANDTHEASSEMBLYFIGURE12SIGNIFICANTMECHANICALPARTSTHATPOSITIONTHELASERABALLFROMBEARING,BCUPFROMMODIFIEDBEARINGSOCKET,CSERVOMOTORWITHUPPERARMATTACHEDANDMOUNTINGBRACKET,DLOWERARMCOMPONENT,ELASERANDLASERMOUNTINGITMUSTBENOTEDTHATTHELOWERARMCOMPONENTSAREHELDTOGETHERVIA2SPRINGSNOTSHOWN,ONEJUSTBELOWTHEELBOWANDTHEOTHERJUSTABOVETHEWRISTFOREACHCLOSEDLOOPSENSORSYSTEMFORAUTOMATEDMANUFACTURINGMACHINES309FOREARMTHEBALLCUPJOINTSGIVEALARGEDEGREEOFFREEDOMTHESEWEREMADEFROMBALLINSOCKETBEARINGSTHEUPPERARMSSWINGFROMSIDETOSIDEWHEREASTHELOWERARMSCANMOVEUP,DOWN,LEFTANDRIGHTANDCANEVENROTATEABOUTTHEELBOWBYSEQUENCINGPAIRSOFITSBASICMOTIONINDUCEDBYROTATINGPAIRSOFSERVOSTHELASERCANMOVEABOUTASECTIONOFSPACE,WHICHISROUGHLYAHEMISPHEREBELOWTHESENSITIVITYAREATHESQUARECUTOUTONTHESERVOMOUNTINGFRAME,FIGURE13ATHEGUIDELINESFORPARALLELMECHANISMDESIGNWEREFOLLOWEDASPROVIDEDIN5FIGURE13ASSEMBLYOFALLCOMPONENTSRESULTINGINTHEFINALSTRUCTUREAALLSERVOSMOUNTEDWITHUPPERARMANDLOWERARMATTACHEDTOLASER,BLOWERARMATTACHMENTTOLASERENDEFFECTOR,CARTICULATEDARMELBOWJOINT,DCOMPLETEASSEMBLYELECTRONICHARDWARETHESYSTEMDESIGNEDISAHYBRIDTYPEASMENTIONEDINSECTION12THERESOLUTIONISLOWDUETOTHE5MMDIAMETEROFTHELEDTYPEPACKAGEOFTHELASERSENSORALSOTHEPCBTRACKSROUTINGSENSORSTOBUFFERSANDDATACONVERTERSOCCUPYSIGNIFICANTSPACE,WHICHCOULDNOTBEAVOIDEDTOIMPROVERESOLUTIONASMALLERPACKAGESHOULDBEUSED,PREFERABLYSURFACEMOUNT,HOWEVERTHESECOULDNOTBESOURCEDATTHETIMETHISSCREENWASMADEEACHSENSORGRIDCONSISTSOF64BP103PHOTOTRANSISTORSARRANGEDONAN8X8GRIDTHERESOLUTIONDISTANCEBETWEENTHECENTRESOF2SUCCESSIVESENSORSIS18MMONBOTHTHEROWSANDCOLUMNSTHISPHOTOTRANSISTORHASADAYLIGHTFILTERTOPREVENTWRONGFULSTIMULATIONBYAMBIENTLIGHTITISSENSITIVETOLIGHTWAVELENGTHSINTHERANGE600900NMA650NMKEYRINGLASERISBEINGUSEDASASENSORSTIMULANTTHISISACHEAPANDEFFECTIVESOLUTIONALTHOUGHTHEOUTPUTPOWEROFTHISLASERISLESSTHAN1MW,ITISSUFFICIENTTOTURNTHEPHOTOTRANSISTORONTHESENSEDSIGNALHASTOBEBUFFERED/AMPLIFIEDTOENSURETHATTHEVOLTAGELEVELOUTPUTFROMTHELPT133ISWITHINTHEPROPERDIGITALRANGE008VFORALOGIC0AND355VFORALOGIC1,ACCORDINGTO6FORPROPERELECTRONICDESIGNFORTHISPURPOSEEACHSENSORONACOLUMNISPASSEDTOATRANSISTORDRIVERWITHINAULN2803,WHICHCONSISTSOF8TRANSISTORDRIVERSEIGHTDRIVERCHIPSAREUSED,ONEFOREACHCOLUMNTHEOUTPUTSFROMEACHULN2803AREFEDTOAPARALLELTOSERIALDATACONVERTER,THE74LS166TOSERIALIZETHEDATAFORTRANSFERTOAPCTHE8OUTPUTSERIALLINESFROMTHEDATACONVERTERSAREFEDTOANATMELATMEGA8515MICROCONTROLLERTHEREAREEIGHTBYTESOFDATAANDEACHBITREPRESENTSONESENSORSCURRENTSTATETHECONTROLLERISUSEDTOTRANSFERTHE8BYTESOFDATATOTHEPCVIAITSUSARTTRANSCEIVERANDTHEPCSRS232SERIALPORTITALSOCONTROLSTHE74LS166DATACONVERTERSANDTHESERVOMOTORSTHEMICROCONTROLLERENABLESTHEDATACONVERTERSANDCLOCKSTHEDATAOUTOFEACHOFTHEMSOFTWARETHESOFTWAREHASTWOPARTSTOIT,IETHEMICROCONTROLLERCODEANDTHEUSERINTERFACEMICROCONTROLLERCODETHEREARE4PARTSTOTHEMICROCONTROLLERCODE,IERECEIVINGANDINTERPRETINGCOMMANDSFROMTHEPCSENSORDATAACQUISITIONDATATRANSFERANDSERVOROTATIONRECEIVINGANDINTERPRETINGCOMMANDSTHEREARECOMMANDSFORACTIVATION,SENSORDATAACQUISITION,DATATRANSFERANDSERVOROTATIONTHESETELLTHECONTROLLERWHENTORUNTHECORRESPONDINGROUTINESSENSORDATAACQUISITIONTHISROUTINEENABLES/DISABLESCLEARSANDCLOCKSTHEDATAOUTTHEPARALLELTOSERIALCONVERTERSSEE7FORACOMPLETEDESCRIPTIONOFHOWTHISISACHIEVEDDATATRANSFERONCETHESENSORDATAACQUISITIONROUTINECOMPLETES,THE8BYTESOFDATAAWAITTRANSFERTHESERIALPORTOFTHEPCWORKSWITHTHEASCIICHARACTERSETEACHDATABYTEREPRESENTINGANUMBERINTHERANGE0255MUSTBESENTOUTTHEMICROCONTROLLERSSERIALPORTVIA3ASCIICHARACTERSONECHARACTERFOREACHOFTHEHUNDREDS,TENSANDUNITSDIGITSREPRESENTINGNUMBERS09WHICHINASCIIIS0X300X39INHEXADECIMALNOTATIONINTOTALTHEREARE32CHARACTERBYTES4CHARACTERBYTESPERDATABYTE,INCLUDINGBYTECOMPLETIONCHARACTERTRANSFERREDFROMCONTROLLERTOPCUSINGABAUDRATEOF9600BITSPERSECONDANDINCLUDINGAPARITYCHECKBIT9BITSPERBYTETHISTAKES003STOCOMPLETESERVOROTATIONASTHEREARE4SERVOMOTORS,4PULSEWIDTHMODULATEDSIGNALSHAVETOBEGENERATEDINCOMINGCOMMANDSINDICATEAPARTICULARSERVOANDTHELENGTHOFITSPULSEWIDTHTHEPULSEWIDTHVALUEWILLBERECEIVEDIN3BYTESINTOTALTHEREARE16CHARACTERBYTESTRANSFERREDFROMPCTOCONTROLLER4BYTESPERSERVOTOPOSITIONTHELASERASREQUIREDTHETIMETAKENTODOTHISIS0015S9600BAUDTIMERSWITHINTHECONTROLLERWILLENSURETHATTHEPWMSIGNALSCOMPLYWITHTHEDESIREDRANGEOF12MSUSERINTERFACETHEUSERINTERFACEPROVIDESAVISUALDISPLAYOFTHEDATARECEIVED,64COLOREDCIRCLESREPRESENTTHE64PHOTOTRANSISTORSTHEDISPLAYROUTINESEARCHESTHROUGHEACHDATABYTECOLUMNSFORLOWBITSROWSANDCHANGESTHECOLOROFTHECORRESPONDINGCIRCLEBLUEWHENNOTSTIMULATED,REDWHENSTIMULATEDTHEINTERFACEALSOALLOWSTHEUSER2OPTIONSFORCONTROLEITHERVIAAMOUSEORASELECTIONGRIDWITHTHEMOUSETHEUSERCANMANUALLYCONTROLTHELASERANDMOVEITANYWHEREWITHINITSMECHANICALCONSTRAINTSWHENTHESELECTIONGRIDISACTIVETHELASERWILLPOSITIONITSELF,FIRSTFINDINGAREFERENCEPOINTANDTHENMOVEALONGROWSANDCOLUMNSITWILLPASSOVERALLSENSORSWHICHHAVEBEENSELECTEDBYTHEUSER310AASHAIK,GBRIGHTANDWLXUCONTROLDESIGNOVERVIEWTHESENSORGRIDPROVIDESDIRECTFEEDBACKOFTHEPOSITIONOFTHELASER/TOOLHEADATDISCRETEPOINTSINSPACETHEPURPOSEOFTHEGRIDISTORESETACCUMULATEDERRORSINTHEPOSITIONINGCONTROLSYSTEMTHECOORDINATESOFTHESENSORSARESTOREDINTHECONTROLLINGSOFTWAREWHENERRORSAREACCUMULATEDANDNEEDTOBERESETTHEENDEFFECTORISMOVEDTOSENSORTHATISCLOSESTTOTHEENDEFFECTORONCEITISPOSITIONEDANDTHESENSORISNOTSTIMULATEDITKNOWSTHATTHEREAREERRORSINITSPOSITIONINGANDITTHENSPIRALSOUTTOLOCATETHESENSORANDRESETTHEERROR4PERFORMANCE/OPERATIONTHENOVELTYOFTHISSENSORSYSTEMLIESWITHTHEFACTTHATITCANDETERMINETHEPOSITIONOFTHEENDEFFECTORDIRECTLY,PROVIDEDTHATTHECONSTRAINTSMENTIONEDARESTRICTLYADHEREDTOITDOESNOTDETERMINEPOSITIONFROMCALCULATIONASINLASERTRIANGULATIONSYSTEMSANDITDOESNOTINTEGRATEDISPLACEMENTSASINLASERINTERFEROMETERSTHENOVELTYOFTHEMECHANICALDESIGNISWITHRESPECTTOTHE4ARMSTHATATTACHTOTHEENDEFFECTORTHEARRANGEMENTANDCONFIGURATIONHASTHEADVANTAGEOFEASIERCONTROL,ASIMPLIFIEDKINEMATICSMODELANDADDEDSTIFFNESSSENSORGRIDTHESENSORGRIDOPERATESASINTENDEDAFTERHAVINGINTEGRATEDALLTHEFUNCTIONSDESCRIBEDONTHEMICROCONTROLLERTHEPROJECTISSTILLINTHETESTINGPHASEANDISCURRENTLYBEINGINTEGRATEDINTOTHESYSTEMMUCHWORKISSTILLNEEDEDTOENSURETHESCREENWORKSPROPERLYWITHALLDATACONVERSIONANDTRANSFERROUTINESTHESECONDVERSIONOFTHESCREENISCURRENTLYBEINGDESIGNEDTOIMPROVERESOLUTIONANDSYSTEMREPEATABILITYMECHANICALSTRUCTURETHEMOSTIMPORTANTASPECTOFTHEMECHANICALSTRUCTUREISTHEARTICULATEDARMSASIMULATIONMODELWASCREATEDTOSIMULATEANDANIMATEITSMOVEMENT,TOENSURETHATITCOMPLIESWITHTHEREQUIREMENTSOFTHEDESIGNTHERESULTSARESHOWNINFIGURE14AMOTIONGENERATORISATTACHEDTOEACHSERVOHEADANDISSETTOFOLLOWAHARMONICFUNCTIONTHEENDEFFECTORSMOTIONSPANNEDTHEENTIRERANGEOFTHESENSITIVITYAREAMOSTIMPORTANTLYTHELASERMOUNTINGREMAINEDPARALLELTOTHESENSORGRIDPCBSENSORPLANETHROUGHOUTITSMOTION,THISENSURESTHATTHELASERBEAMISALWAYSPERPENDICULARTOADETECTORTHESINGULARITIESFORTHISMECHANISMOCCURWHENTHEARMSARECOMPLETELYEXTENDEDORFOLDED,WHENTHEUPPERANDLOWERL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