Multiple PZT transducers implemented with multiple-mode piezoelectric shunting for passive vibration damping

In an earlier paper we reported a method for multiple-mode shunt-damping of structural vibration modes. It was successfully demonstrated in experiments on a two-wing cantilever beam to reduce three structural vibration modes simultaneously using a single piezoelectric PZT transducer. This multiple-mode shunting method is particularly useful for reduction of several vibration modes on structures that are limited in surface area and must be lightweight. To obtain a better overall damping performance for some structures, we have extended this shunting technique by employing multiple PZT transducers; each is implemented with a multiple-mode shunt circuit. This paper reports the reason why multiple transducers are needed and how we design the multiple-mode shunt circuits for them. This is described with experiments performed on two structures: one, a simple cantilever beam and the other, a cut-out panel from an F-15 fighter aircraft. Both of the structures are bonded with several PZT transducers implemented with multiple-mode shunt circuits. In the cantilever beam structure, we show the advantage of using a different transducer for controlling modes that are otherwise not controllable with the first transducer alone. For the F-15 panel, five PZT transducers were bonded on the inner surface of the panel. During the shunting experiment, the panel was excited with an acoustic load. We report how we determined the locations and the number of the transducers, and how we designed and implemented them with multiple-mode shunt circuits to control the two high-structural-vibration modes. Detailed experimental results are presented.