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452PROCEEDINGSOFTHE26THCHINESECONTROLCONFERENCEJULY2631,2007,ZHANGJIAJIE,HUNAN,CHINAADESIGNOFVISIONBASEDLOCATIONCONTROLSYSTEMFORSTEELROLLINGMILLCHENWEI,FANGKANGLING,LIUXINHAICOLLEGEOFINFORMATIONSCIENCEANDENGINEERING,WUHANUNIVERSITYOFSCIENCEANDTECHNOLOGY,WUHAN430081,PRCHINAEMAILCHEN309WEI126COM,KLFANGMAILWUSTEDUCN,STEELLIUMAILWUSTEDUCNABSTRACTTHISPAPERDESCRIBESACLOSEDLOOPCONTROLSYSTEMBASEDONMACHINEVISIONINTHEPOSITIONCONTROLOFTHEHOTBILLETOFSTEELITISBASEDONANINDUSTRIALCAMERAASAVISUALSENSORTHATPROVIDESTHEPOSITIONINFORMATIONOFTHESTEELBILLETSINTHEHEATINGKILN,ANDISUSEDTODETECTTHEMOVINGBILLETSTOMEETTHEREQUIREMENTOFAROBUST,REALTIMEDETECTIONOFMOVINGBILLET,THISPAPERUSESTHESIMPLYBACKGROUNDSUBTRACTIONMODELTODETECTTHEMOVINGBILLETSTHEDIFFERENCEGRAYPROFILEPROJECTISAPPLIEDTODETECTTHEEDGEOFTHEBILLET,ANDTHEEFFECTISWELLINTHEPRACTICALAPPLICATION,THEVIDEOCONTROLSYSTEMHASOBTAINEDGOODCONTROLPERFORMANCEUNDERTHEINDUSTRIALENVIRONMENTKEYWORDSMACHINEVISION,OBJECTLOCATION,BACKGROUNDSUBTRACTION,FEEDBACKCONTROL1INTRODUCTIONINTHESTEELMILL,THEPREPROCESSINGOFSTEELBILLETSISHEATEDTO10001200INTHEHEATINGKILN,BEFORETHEYAREROLLEDFLATBLOCKSTHELAYOUTOFBILLETSINTHEKILNISTWOBILLETSINONEROWBECAUSETHELENGTHOFTHEKILNIS279M,ANDTHEWIDTHOFTHEKILNIS129MTHEOPERATORSCANNOTOBVERSETHEMOVINGOFBILLETSINTHEKILNDIRECTLYINORDERTOAVOIDTOCOLLIDINGAMONGTHEBILLETS,THEPOSITIONOFMOVINGBILLETSSHOULDBECONTROLLEDWHENTHEBILLETSARESENTINTOTHEHEATINGKILNFURTHERMORE,THECOMMONCONTACTPOSITIONSENSORSCANNOTAFFORDTHEHIGHTEMPERATUREINTHEKILN,ORISDESTROYEDBYTHECOLLIDINGOFTHEBILLETSEASILYTHEFEASIBLEMETHODISANONCONTACTDETECTIONMETHODACAMERAWHICHISSETONTHESIDEOFTHEKILNSHOWSINFIG1OBTAINSTHEINFORMATIONOFTHEBILLETSFIG1THECAMERAISSETONTHEKILNTHECAMERAHAS610170RESOLUTIONANDCANACQUIRE30FULLFRAMESPERSECONDPLANTOPERATORSUSETHEVIDEOCAMERAWHENTHEYMONITORANDCONTROLTHEPOSITIONOFBILLETBUTHUMANOPERATORSADJUSTTHEPOSITIONOFBILLETSBASEDONTHEOBSERVATIONBYINDUSTRIALTVISSUBJECTIVE,EXPERIENCEDEPENDENT,ANDLABORINTENSIVE5THEREARESOMEPROBLEMSINPRACTICALOPERATION,SUCHASTHELOWPRECISION2MINUTE,ANDSOON2THEPROBLEMANDCONTROLSYSTEMTHEREISAPROBLEMINTHEPOSITIONCONTROLOFTHEBILLETSTHATIS,THEREARETWOBILLETSINONEROWSOTHEREARETWODISTANCESWHICHMUSTBECONTROLLEDINTHEPOSITIONCONTROLOFTHEBILLETSONEISTHEDISTANCEBETWEENTHEBILLETAANDTHEBILLETBANOTHERISTHEDISTANCEBETWEENBILLETANDTHEWALLOFKILNSHOWSFIG2FIG2THEPOSITIONCONTROLOFBILLETSDISCREPANCIESBETWEENBILLETAANDBILLETB,ORBETWEENTHEBILLETSANDTHEKILN,WHICHISCONSECUTIVESTANDS,CANLEADTOTHECOLLIDINGOFTHEBILLETSWHENTHEYMOVEINTHEKILNIFONEOFTHEMEXCEEDSCERTAINLIMITSTHISLEADSTOACOLLISIONBETWEENTWOBILLETS,ORBETWEENTHEWALLOFKILNANDTHEBILLETSDURINGTHEBILLETSMOVINGSOMETIMESCATASTROPHICFAILUREOCCURSWITHTHECOLLISIONSITLEADSTOACOMPLETEINTERRUPTIONOFPRODUCTIONANDREQUIRESTHEPOSITIONOFBILLETSTOBEADJUSTEDBYHANDINORDERTOSIMPLIFYTHECONTROLPROBLEM,WECHOOSETHECENTEROFTHEKILNISTHEMIDDLEPOINTOFPOSITIONTHENWECANGETTHEEXPECTEDDEVIATIONIS123LS1WHERELISTHEWIDTHOFKILN,SISTHELENGTHOFBILLETS,ISTHEEXPECTEDDEVIATIONBETWEENTHEKILNANDTHEBILLET,ORBETWEENTHEBILLETANDTHEBILLETTHECAMERAINTHEKILNISREGARDEDASAVISUALSENSORINTHEVISIONBASEDCONTROLSYSTEM,THUSTHEBILLETOFPOSITIONCANBEFEEDBACKTOTHEPIDCONTROLLERSINCETHECAMERAHASAFINITEVIEW,THEREARETWOFEEDBACKSIGNALSONEISTHEVIDEOSIGNALANOTHERISTHESIGNALOFIMPULSECOUNTERFIG3SHOWSTHEFRAMEOFTHEVISIONBASEDLOCATIONCONTROLSYSTEM453FIG3THEFRAMEOFVISIONBASEDLOCATIONCONTROLSYSTEM3THEVIDEOPOSITIONALGORITHMTHEMOSTCOMMONMETHODTODETECTMOTIONINARUNNINGSEQUENCEOFIMAGESISBACKGROUNDSUBTRACTINGTHATISACHIEVEDBYTAKINGABSOLUTEDIFFERENCESBETWEENEACHINCOMINGFRAMEANDABACKGROUNDMODELOFTHESCENE2,3HOWEVER,THEMETHODISSENSITIVETOCHANGESOFDYNAMICSCENEDUETOLIGHTINGANDEXTRANEOUSEVENTSWHICHMAYREDUCEFALSEDETECTIONINORDERTOSOLVETHEPROBLEM,WEUSEADIFFERENCEGRAYPROFILEPROJECTALGORITHMTODETECTTHEPOSITIONOFBILLETS831IMAGEDENOISINGTHEREARESOMANYDISTURBANCESINTHEINDUSTRIALFIELDTHATTHEQUALITYOFTHEIMAGECAPTUREDISBADMOREOVER,THEREISNOTAFIXEDLIGHTINGINTHEKILNTHELIGHTWOULDBECHANGEWITHTHECHANGEOFTEMPERATURECONVENTIONALLY,THEFIRSTSTEPOFIMAGEPROCESSINGISTOELIMINATEORTODECREASETHEINFLUENCEOFNOISEBECAUSEOFTHEHARSHENVIRONMENTINTHEKILN,ITDOESNTELIMINATENOISETHOROUGHLYTHEREAREALOTOFNOISESTILLOCCASIONALLYAPPEARSINTHEIMAGECAPTUREDSHOWSFIG3INORDERTOPROCESSTHEIMAGEREALTIME,WEONLYTAKEASIMPLYDENOISINGBYHARDWAREMETHODTHEEXPERIMENTALRESULTSSHOWEDTHATMEETSTHEREQUESTOFIMAGEPROCESSINGINUSINGTHEBACKGROUNDPROJECTSUBTRACTIONALGORITHMFIG4THETYPICALIMAGECAPTUREDBYTHECAMERA32EXTRACTINGFEATUREANDEDGEDIFFERENCEISANEFFECTIVEMETHODINTHEDETECTINGOFAMOVINGOBJECTTHEREISAHIGHCORRELATIONINTHESERIESIMAGEIFTHECORRELATIONCANBEREDUCE,THEMOVINGTARGETISEASIERTOBESEGMENTEDFROMTHEBACKGROUNDTHEDIFFERENTIALALGORITHMCANREDUCETHECORRELATIONOFTHESERIESFRAMEOFVIDEOSLET,JIFBISABACKGROUNDIMAGE,AND,JIFKISTHECURRENTIMAGE“,3,2,1KTHENTHEDIFFERENTIMAGE,JIFCIS,JIFJIFJIFKBC2ASTATISTICMETHODHASBEENAPPLIEDTODETECTTHEEDGEOFBILLETITISKNOWNTHATTHECOLUMNGRAYVALUEOFTHEMOVINGREGIONWOULDBESIGNIFICANTLYDIFFERENTFROMTHECOLUMNGRAYVALUEOFTHEBACKGROUNDIMAGE,WHENTHEOBJECTMOVESINTHESCENEFIG5SHOWSTHECHANGEOFCOLUMNVERTICALPROJECTIONGRAYVALUEOFTHEIMAGEWHENTHEREISAMOVINGOBJECTWHICHAPPEARSINTHEIMAGE,ORDOESNTAPPEARINTHEIMAGETHENTHEGRAYVALUEWILLCHANGESTRONGLYATPOINT2TOR3TFIG5THECHANGEOFGRAYWHENTHEBILLETMOVESLETTHECOLUMNPROJECTIONGRAYVALUEOFTHEDIFFERENTIMAGEIS11,1,MICJCJIFMJIF3WHERE,JIFJCISTHEJTHCOLUMNVERTICALPROJECTIONGRAYVALUEBECAUSETHEFINALPOSITIONOFTHEBILLETAISTHEBACKEDGE,THELEFTHANDSIDEOFIMAGEISARELATIVEMOVINGREGIONTHEGRAYSCALECHANGESSLOWLYHOWEVER,THEFINALPOSITIONOFTHEBILLETBISTHELEADINGEDGE,THERIGHTHANDSIDEOFIMAGEISARELATIVEMOVINGREGIONFORTHEBILLETBTHETECHNIQUEOFSLIDINGWINDOWISUSEDTOEXTRACTTHEFEATUREOFEDGEFORIMPROVINGTHEREALTIMEANDTHEPRECISIONOFTHEBILLETSLOCATIONTHESLIDINGWINDOWISA170HWINDOW,WHEREH50ISANADJUSTINGCOEFFICIENTTHEREAREMANYDISTURBANCESINTHEINDUSTRIALCONDITIONITIMPROVESTHEROBUSTOFALGORITHMTOCOMPUTETHECHANGEOFEVERYCOLUMNVERTICALPROJECTIONGRAYVALUEANDTHECHANGEOFDIFFERENCEBETWEENTWOCOLUMNSINTHESLIDINGWINDOWLET1THISTHEPEAKGRAYTHRESHOLD,2THISTHECOLUMNDIFFERENTGRAYTHRESHOLD,THEN111,THEN1JCFIJTHFF42,JJCCFIJFITJTHTHEN221FF5WHERE1FISTHENUMBEROFCHANGINGCOLUMN,2FISTHENUMBEROFCOLUMNDIFFERENTCHANGING,TISTHENUMBEROFSLIDINGCOLUMNACCORDINGTOTHETHEORYOFNEARESTNEIGHBORDECISION1,THEDISCRIMINATEDFUNCTIONIS2212MFAFBTH6WHERETHISTHEFEATURECHANGETHRESHOLD,VABISTHEFEATUREVECTOROFEDGEWHENTHEEDGEOFBILLET454APPEARSINTHEIMAGE,WHICHGETSTHROUGHTRAININGOFFLINEWHENTHEDISCRIMINATEDFUNCTIONISMIN,THEEDGEOFBILLETAPPEARSINTHESLIDINGWINDOWTHENTHEMOVINGDISTANCEOFBILLETSISCHILFF7WHEREILISTHEMOVINGDISTANCEDURINGTHESAMPLETIMEINTERVALT,CFISTHEMAXCHANGINGCOLUMNOFCURRENTFRAME,HFISTHEMAXCHANGINGCOLUMNOFFORMERFRAME33BACKGROUNDMAINTENANCETHISPAPERUSESAPERIODICALUPDATINGTHEBACKGROUNDSTRATEGYTOSPEEDUPTHEIMAGEPROCESSINGTHEBACKGROUNDUPDATINGALGORITHMADOPTSTHEFIRSTORDERRECURSIVEFILTERMETHODISUSEDTOINTEGRATENEWINCOMINGINFORMATIONTOTHECURRENTBACKGROUNDIMAGE4THEBACKGROUNDUPDATESEVERYMFRAMEAS,1,1BKBFIJKFIJFIJK8WHERE,BFIJKISTHEBACKGROUNDIMAGE,ISASMALLPOSITIVENUMBER,KFIJISTHECURRENTIMAGE4THECONTROLALGORITHMBECAUSETHEWEIGHTOFABILLETIS1800,THEINERTIAOFTHEBILLETISAANOTHERPROBLEMINTHEPOSITIONCONTROLITMAKESTHEBILLETSTOSLIDEWHENTHESTEPPERMOTORHASSTOPPEDTHISPAPERADOPTSATWOSTAGECONTROLSTRATEGYTOSOLVETHESLIDINGPROBLEMOFTHEBILLETSFIRSTLY,THEBILLETSARERAPIDLYLOCATEDATSOMECERTAINPOSITIONINTHEKILNTHENTHEBILLETSAREPRECISELYLOCATEDTHEEXPECTEDPOSITIONBYAVISIONBASEDFEEDBACKCONTROLALGORITHMTHEFLOWOFLOCATIONCONTROLALGORITHMISILLUSTRATEDINFIG6HARDWAREDENOISINGDETECTINGEDGECAPTURETHEIMAGERENEWTHEBACKGROUNDNYDIFFERIMAGESLIDEWINDOWEXTRACTINGFEATUREPIDFASTLOCATIONALGORITHMEXPECTEDPOSITION1NYNYCAPTURETHEIMAGEHARDWAREDENOISINGDIFFERIMAGESLIDEWINDOWEXTRACTINGFEATUREPIDPRECISELYLOCATIONALGORITHMEXPECTEDPOSITIONTHEENDBILLETLOCATIONFIG6THEFLOWOFLOCATIONCONTROLALGORITHMFIG7,8SHOWSTHERESULTOFFASTLOCATIONANDTHEPRECISELOCATIONFIG7THERESULTOFFASTLOCATIONFIG8THERESULTOFPRECISELOCATION5APPLICATIONAANDCONCLUDETHEVISIONLOCATIONCONTROLSYSTEMWHICHDESCRIBESINTHISARTICLEHASBEENSUCCESSFULLYPUTINTOPRACTICALAPPLICATIONFORTWOYEARS,ANDOBTAINEDGOODCONTROLPERFORMANCEUNDERTHEINDUSTRIALENVIRONMENTSHOWSFIG8FIG9SHOWSTHEINTERFACEOFCONTROLSYSTEMFIG9THEINTERFACEOFCONTROLSYSTEMTAB1SHOWSTHECONTROLEFFECTOFTHEVIDEOFEEDBACKCONTROLSYSTEMTAB1THEERRORRATEOFPOSITION5CMERRORRATE/OLDCONTROLSYSTEM76VIDEOFEEDBACKCONTROLSYSTEM9697THEVISIONBASEDLOCATIONCONTROLSYSTEMCANDETECTTHEEDGEOFTHEMOVINGBILLETSINTHEFRAMEOFIMAGESTATISTICALPROJECTMETHODUSESTODETECTTHEEDGEOFTHEMOVINGBILLETSTHERESULTOFPRACTICALOPERATIONPROVESTHATTHEDIFFERENCEGRAYPROFILEPROJECTALGORITHMISFEASIBLEUNDERTHEINDUSTRIALENVIRONMENTBUTTHEVISIONBASEDLOCATIONCONTROLSYSTEMMAYBEMAKINGAMISTAKEBECAUSEOFVERYPOOROPERATEENVIRONMENT,BECAUSETHEDIFFERENCEBETWEENTHEOBJECTANDTHEBACKGROUNDISNOTSIGNIFICANT455THEREALTIMEANDROBUSTOFMOVINGOBJECTDETECTINGALGORITHMINCOMPLEXINDUSTRIALCONDITIONSHOULDNEEDTORESEARCHFURTHERREFERENCES