Active feedback control of acoustic noise in 3 - D enclosures

Liu, Feng
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Mechanical Engineering
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Active Noise Control (ANC) strategies using feedback control methods are investigated for reducing acoustic noise in 3-D enclosures. It has been shown that robust control design techniques are effective in broadband control of noise especially in low frequency range. The work presented includes modeling, system identification, controller design, and experimental validation of different active control methodologies. The finite dimensional approximate models were obtained using both analytical as well as system identification-based methods. The analytical model was derived using basic 3-D wave equation and assumed modes method. The system identification-based model was derived using ERA-based system-id toolbox (SOCIT). The controller designs presented include LQG, passivity-based, and an H-infinity designs. The LQG design which used the state-weighting matrix derived directly from the energy function of the enclosure performed very effectively. The passivity-based controllers gave the most satisfactory closed-loop performance. These controllers are based on energy-extraction principle, and therefore, are the most desirable candidates for ANC systems. These controllers have excellent stability robustness properties as well. With high modal density and resonant peaks in the frequency response the design of H-infinity controllers becomes very difficult. For single and multi-tone cases, both LQG as well as passivity-based controllers gave significantly large noise reductions. For broadband white noise disturbance the noise reduction up to 6 dB was obtained without destabilization.

Mechanical engineering