Optimization-of-Passive-Air-Damping-of-MOEMS-Vibration-Senso(4)

A. Kainz et al. / Procedia Engineering 87 ( 2014 ) 440 – 443

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Figure3:AmplitudeandphaseofthetransferfunctionA(f=ω/2π)(Eq.(1))ofoursensormeasuredat3·10 4mbar(left)andatmospheric

pressure(right).Thegreenandbluelines/circlescorrespondtomeasurements,theblackdashedlinetoa tofthedata.Theinsetsshowazoomaroundtheresonancepeak.

dampingcoe cienttobeslightlyhigherthantheoneobtainedbytheFVM,butlowerthantheoneobtainedbythemodel.Theresonancefrequencywasdesignedtobef0=780Hz.

ThesetupformeasuringtheteststructureisdepictedinFig.2b.Todeterminetheactualairdampingandtoisolateitfromothere ects,suchasthermoelasticdampingandanchorloss,weconductedourmeasurementsatpressuresofp=3·10 4mbarandp=1bar.ThecorrespondingtransferfunctionsaredepictedinFig.3.Fitsofthetransferfunctionsrevealedadampingofd≈0.01mg/sinvacuumandd=3.51mg/sinatmosphericpressure.Thus,themeasuredairdampingofd=3.50mg/sisinexcellentagreementwiththedesignedvalue.

Ithasbeenshownthatnotonlyviscousdragbutalsopressureforcescontributetothedamping.Whenappliedasavibrationsensor,wewanttoincreasethedissipationasfaraspossible.Futuredevicesthatwillnotbeoperatedinvacuumcanbedesignedwithabyfardecreasedxfr.Incombinationwithoptimizedparameters,weexpecttoreachacriticallydampedoscillatorbypassiveairdampingalone.References

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