Abstract

Active control of sound and vibration fields has become an strong area of research over the past few decades. In regards to the active control of acoustic radiation from vibration fields, known as active structural acoustic control (ASAC), there have been many different methods employed to understand structural and acoustic relationships and to control vibrations to limit the acoustic radiation. With active sound field control, sensors, usually microphones, need to be dispersed in the sound field, or an array of microphones must be placed directly in the sound field which, in many cases, uses up too much space for practical applications. To remedy this, objective functions have been transferred to the structure, sensing vibrations rather than pressures. A small, integrated array of structural sensors can be placed on the structure, reducing the system's overall footprint. Acoustic energy density has become a well established objective function, which produces a more global effect using only a local measurement. Another benefit of acoustic energy density lies in the breadth of sensor placement. While acoustic energy density has proven successful in active noise control (ANC), the quantity deals with pressures, not surface vibrations. The problem with ASAC is that an objective function with the robustness of acoustic energy density does not yet exist. This thesis focuses on a structural error sensing technique that mimics the properties of acoustic energy density control in the sound field. The presented structural quantity has been termed Vcomp, as it is a composite of multiple terms associated with velocity. Both analytical and experimental results with the control of this quantity are given for a rectangular plate. The control of Vcomp is compared to other objective function including squared velocity, volume velocity and acoustic energy density. In the analytical cases, the benefits include: control at higher structural modes, control largely independent of sensor location, and need for only a single point measurement of squared Vcomp with a compact sensor. The control at higher frequencies can be explained by the control of multiple acoustic radiation modes. Experimental results offer some validity to the analytical benefits but alternate sensing techniques need to be investigates to more fully validate these benefits.

Degree

MS

College and Department

Ira A. Fulton College of Engineering and Technology; Mechanical Engineering

Rights

http://lib.byu.edu/about/copyright/

Date Submitted

2010-08-30

Document Type

Thesis

Handle

http://hdl.lib.byu.edu/1877/etd3961

Keywords

ASAC, ANC, structural control, velocity control, active control of structures, Fisher

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