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Proceedings Paper

Hybrid structural/acoustic control of a subscale payload fairing
Author(s): Keith K. Denoyer; Steven Fulton Griffin; Dino Sciulli
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Paper Abstract

During launch, spacecraft experience severe acoustic and vibration loads. Acoustic loads are primarily transmitted through the shroud or payload fairing of the launch vehicle. In recent years, there has been a trend towards using lighter weight and extremely stiff structures such as sandwich construction and grid-stiffened composites in the manufacturing of payload fairings. While substantial weight savings can be achieved using these materials, the problem of acoustic transmission is exacerbated. For this reason, the Air Force Research Laboratory has been actively engaged in vibroacoustic research aimed at reducing the acoustic and vibration levels seen by payloads during launch. This paper presents experimental results for the simultaneous structural and acoustic cavity mode control of a sub-scale composite isogrid payload fairing structure. In this experiment, actuation is performed through the use of both an internal speaker as well as piezoceramic strain actuators located on the outer skin of the composite structure. Sensing is accomplished using a microphone as well as a piezoelectric strain sensor. The control approach presented in this paper is a decentralized frequency domain approach which makes use of a series of independent control loops. One loop uses the microphone and speaker, while additional loops use the piezoelectric sensors and actuators. The control algorithm consists of independent second-order Positive Position Feedback (PPF) controllers tuned to reduce the magnitude of each cavity mode. A PPF filter in conjunction with an extremely sharp bandpass filter is used on the structural mode of limit spillover. This approach leads to a substantial reduction in the acoustic transmission in the range of 0 - 800 Hz. Transmission coincident with the primary cavity modes of the system are reduced in magnitude by 26 and 9 dB respectively while the structural model that is responsible for the majority of transmission is reduced by approximately 7 dB.

Paper Details

Date Published: 27 July 1998
PDF: 7 pages
Proc. SPIE 3329, Smart Structures and Materials 1998: Smart Structures and Integrated Systems, (27 July 1998); doi: 10.1117/12.316896
Show Author Affiliations
Keith K. Denoyer, Air Force Research Lab. (United States)
Steven Fulton Griffin, Air Force Research Lab. (United States)
Dino Sciulli, Air Force Research Lab. (United States)

Published in SPIE Proceedings Vol. 3329:
Smart Structures and Materials 1998: Smart Structures and Integrated Systems
Mark E. Regelbrugge, Editor(s)

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