MS thesis abstract - Gutierrez, Carlos
| Author: | Gutierrez, Carlos |
| Degree: | Masters of Science |
| SERC #: | 6-00 |
| File type: | PDF, 215 kB |
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Unidirectional Active Acoustic Control for Launch Vehicle Fairings
Large amplitude vibro-acoustic loads during launch cause 40% of first day spacecraft failures. Structural-acoustic control offers the potential of reducing these loads without increasing payload mass by actively stiffening and destiffening the structure of the fairing to reduce acoustic transmission and reflection. In this thesis, two methods of structuralacoustic control for launch vehicle fairings are investigated. Both methods employ feedback control using only structural sensors and actuators to obtain global attenuation of the acoustic field within the fairing. This approach avoids the need for sensors and actuators near the payload, and is more effective at reducing the effect of disturbances than feedforward control.
The first method implements simultaneous transmission and reflection control on the structure. Individual Linear Quadratic Gaussian controllers are designed for transmission and reflection control and combined using superposition. Two separate sets of sensors are investigated: a microphone/accelerometer pair and a microphone/PVDF pair. Similar 10-1000 Hz broadband attenuation of 3.6 dB was predicted using both sensor pairs, but experimental results showed that the microphone/PVDF pair attenuated the broadband acoustics by 4.14 dB, whereas the microphone/accelerometer pair only attenuated the broadband acoustics by 2.62 dB.
The second method implements an acoustic power diode which allows acoustic energy to flow though the plate in only one direction, in this case, from the inside to the outside of the payload fairing. The diode only targeted the first structural mode due to sensor limitations. It was implemented on a symmetric acoustic chamber to show the effect of the diode depending on the end where the disturbance source was located. Although the diode effect was present, its performance was less than predicted. An attenuation of 10.56 dB at the first acoustic mode was obtained, with the possibility of even higher performance were the accelerometer to perform as predicted.