Six degrees of freedom measurement with continuous scanning laser Doppler vibrometer

The dynamicresponseofastructurecanconsistofuptosixdegreesoffreedom(DOF).
Not allofthemmaybepresentatalltimesinastructure,butforadetailedfinite
elementmodelvalidationitisimportanttoprovideasmuchinformationaspossible.
CurrentcontacttransducerscanpickupacombinationofsomeofthementionedDOFs,
but arenotabletoprovideallsixDOFsfromasingletransducer.Severalcontact-less
transducers,suchasaScanningLaserDopplerVibrometer(SLDV),canbecombinedtoa
single measurementsystemthatallowsthedeterminationofuptothreetranslational
degreesoffreedomatapoint,buttheyarestillnotprovidingrotationalinformationas
the laserbeamisfixedtoapoint.ContinuouslyScanningLaserDopplerVibrometer
(CSLDV)methodscanpartlyovercomethisissuebytravellinginsmallcirclesaroundthe
measurementlocationandthusalsosensingtherotationaroundthethreeaxesata
point.AnintroductionofCSLDVmethodsformeasuringDOFsatapointisgiven,
focussingonamethodforcapturingupto5DOFsusingalens.However,thelenscan
make themeasurementofthein-planerotationverydifficultandimpractical.Thispaper
presentsanewtypeofscanningdevicewhichallowsmeasuringallsixdegreesof
freedomatameasurementlocationwithasinglesetupandasinglepointLDV,by
combiningvariablesmallcirclescans.Experimentalvalidationofthescanningheadis
presentedandthemeasurementofthelastDOF,thein-planerotation,isdemonstrated.