A COMPARISON OF ARTIFICIAL NEURAL NETWORKS AND OTHER STATISTICAL METHODS FOR ROTATING MACHI

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1、ACOMPARISONOFARTIFICIALNEURALNETWORKSANDOTHERSTATISTICALMETHODSFORROTATINGMACHINECONDITIONCLASSIFICATIONA.C.McCormickandA.K.NandiAbstractStatisticalestimatesofvibrationsignalssuchasthemeanandvariancecanprovideindicationoffaultsinrotatingmachinery.Usingtheseestimatesjoi

2、ntlycangiveamorerobustclassicationthanusingeachindividually.Articialneuralnetworkarchitecturesandsomestatisticalalgorithmsarecomparedwithemphasisontrainingrequirementsandreal-timeimplementationaswellasoverallperformance.IntroductionAnalysisofvibrationscanindicatefaul

3、tconditionsinrotatingmachinery[1]suchasshaftunbalanceorrubbing.Onecommonapproachistoestimatetime-invariantfeaturesfromthevibrationtimeserieswhichchangewhenafaultoccursinthemachine.Thesefeaturescanthenbeinputintosomeformofclassicationsystemtodecidethemachine'scondition

4、.Articialneuralnetworkssuchasmulti-layerperceptrons(MLPs)provideasystemwhichcantheo-reticallyprovideBayesoptimalclassicationoftheconditionbaseduponmanyfeatures[2].Trainingnetworkscanhowevertakeasubstantiallengthoftimeandisnotguaranteedtondtheoptimalso-lution.Radialb

5、asisfunction(RBF)neuralnetworksprovideanalternativearchitecturewhichcanbetrainedinamuchshorterperiodoftime.Traditionalstatisticaldiscriminantanalysis[3]algorithmscanbeverysimpletoimplementanddonotrequireatimeconsumingtrainingalgorithm.Butinmanycases,theyrequirecertaina

6、ssumptionstobemadeabouttheinputdata.Iftheseassumptionsarenotvalid,theymaynotprovideasgoodasolutionasaneuralnetwork.ExperimentalSet-UpThevibrationsweremeasuredfromasmallexperimentalmachineset.Thisconsistedofanelectricmotorwhichdroveashaftwitha ywheel.Smallweightscouldbe

7、attachedtothe ywheelunbalancingtheshaftandrubbingcouldbeappliedusingascrewattachedtoaframe.Thevibrationsweremeasuredhorizontallyandverticallyusingaccelerometersattachedtoabearingblock.Thisset-upallowedthecreationoffourmachineconditions:NN-nofaultsapplied;NR-onlytherubf

8、aultisapplied;WN-onlytheunbalancefaultisapplied;WR-bothrubandunbalancefaultsareapplied.TheshaftDepartmentofElectronic