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Adaptive Collocated Feedback for Noise Absorption in Acoustic Enclosures

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dc.contributor.authorCreasy, Miles Austinen
dc.contributor.committeechairLeo, Donald J.en
dc.contributor.committeememberJohnson, Martin E.en
dc.contributor.committeememberCarneal, James P.en
dc.contributor.committeememberInman, Daniel J.en
dc.contributor.departmentMechanical Engineeringen
dc.date.accessioned2014-03-14T21:47:44Zen
dc.date.adate2006-11-29en
dc.date.available2014-03-14T21:47:44Zen
dc.date.issued2006-10-06en
dc.date.rdate2006-11-29en
dc.date.sdate2006-10-19en
dc.description.abstractThis thesis focuses on adaptive feedback control for low frequency acoustic energy absorption in acoustic enclosures. The specific application chosen for this work is the reduction of high interior sound pressure levels (SPL) experienced during launch within launch vehicle payload fairings. Two acoustic enclosures are used in the research: the first being a symmetric cylindrical duct and the other being a full scale model of a payload fairing. The symmetric cylindrical duct is used to validate the ability of the adaptive controller to compensate for large changes in the interior acoustical properties. The payload fairing is used to validate that feedback control, for a large geometry, does absorb acoustic energy. The feedback controller studied in this work is positive position feedback (PPF) used in conjunction with high and low pass Butterworth filters. An algorithm is formed from control experiments for setting the filter parameters of the PPF and Butterworth filters from non-adaptive control simulations and tests of the duct and payload fairing. This non-adaptive control shows internal SPL reductions of 2.2 dB in the cylindrical duct for the frequency range from 100 to 500 Hz and internal SPL reductions of 4.2 dB in the full scale fairing model for the frequency range from 50 to 250 Hz. The experimentally formed control algorithm is then used as the basis for an adaptive controller that uses the collocated feedback signal to actively tune the control parameters. The cylindrical duct enclosure with a movable end cap is used to test the adaptation properties of the controller. The movable end cap allows the frequencies of the acoustic modes to vary by more than 20 percent. Experiments show that a 10 percent change in the frequencies of the acoustic modes cause the closed-loop system to go unstable with a non-adaptive controller. The closed-loop system with the adaptive controller maintains stability and reduces the SPL throughout the 20 percent change of the acoustic modes' frequencies with a 2.3 dB SPL reduction before change and a 1.7 dB SPL reduction after the 20 percent change.en
dc.description.degreeMaster of Scienceen
dc.identifier.otheretd-10192006-134038en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-10192006-134038/en
dc.identifier.urihttp://hdl.handle.net/10919/45209en
dc.publisherVirginia Techen
dc.relation.haspartCreasy_Thesis.pdfen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectFairingen
dc.subjectPayloaden
dc.subjectFeedback controlen
dc.subjectAcoustic Enclosureen
dc.subjectPPF controlen
dc.subjectAcousticsen
dc.titleAdaptive Collocated Feedback for Noise Absorption in Acoustic Enclosuresen
dc.typeThesisen
thesis.degree.disciplineMechanical Engineeringen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.levelmastersen
thesis.degree.nameMaster of Scienceen

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