| Hybrid active/passive control systems present unique, energy-efficient solutions to noise and vibration problems. Active systems frequently offer the only feasible control of low-frequency, high intensity vibrations, while passive materials offer superior attenuation at higher frequencies. These two approaches can be optimally coordinated for efficient broad-band control. Hybrid design methodologies are developed, modeled, and tested experimentally for acoustic control in a full-scale rocket fairing and for vibration control of an aircraft panel.; First, spatially weighted transducer arrays with H2 feedback control globally attenuate targeted low frequency acoustic modes in the fairing. Further coordination with passive acoustic foam demonstrates significant broadband acoustic control. Feasibility studies indicate that logistical considerations for actual launch application may not be prohibitive, but some optimization is necessary.; For more energy-efficient design, loudspeakers are tuned as optimal acoustic absorbers. Irregular geometry, changing payloads, and the compliant nature of the fairing hinder use of a passively tuned loudspeaker. Enclosure dynamics are digitally identified and used to actively tune the dynamics of the loudspeaker for passive dissipation of high intensity, low-frequency modes. Experimental results indicate that tuned loudspeakers can dissipate 12 dB per absorber at targeted modes.; Hybrid design then combines active and passive elements to reduce the vibrational energy in a typical aircraft panel. An energy balancing metric forms the basis of an optimization routine designed to minimize both the broad-band vibration of the structure and the weight, volume, and energy use of the control system. The metric also coordinates inherent benefits within the hybrid controller, improving the performance of active and passive materials. Implementing this design, active piezoceramic patches partner with a passive constrained layer damping treatment to present a coordinated control system no longer confined to a particular frequency range. Global average reductions exceed 8 dB in the 1000 Hz bandwidth. Optimally placed damping demonstrates 75% of the attenuation found in a typical full-coverage application while using only 9% of the material. Finally, the hybrid design method is expanded for multi-dimensional hybrid vibration control of flat and curved panel structures and for colocated hybrid control. |
