Optimal Virtual Mechanical Impedances Ap- Proach for the Vibroacoustic Active Con- Trol of a Panel

In order to reduce the acoustic power radiated by a structure, co-located actuator and sensor pairs are used to virtually implement local mechanical impedance. For each pair, at each frequency of interest, the virtual mechanical impedance is a complex value which imposes a linear relationship between the dual local variables of the actuator input and the sensor output. The optimal virtual mechanical impedances are defined at each frequency as the ones which minimize the sound power radiated by the structure. From a theoretical point of view, they can be computed from the primary sound field and the transfer functions between the control actuators, structural sensors and far-field acoustic sensors. The proposed experimental approach is a two-step process: (1) measurement and identification of transfer functions to compute the optimal virtual mechanical impedances; (2) implementation of the computed virtual mechanical impedances with a real-time MIMO harmonic controller. Measured and computed results are presented for a simply supported thin plate (aluminum). Special focus is put on the discussion about such control approach versus a classical active damping where the virtual mechanical impedance is defined as real positive.