An adaptive negative capacitance circuit for enhanced performance and robustness of piezoelectric shunt damping

Piezoelectric shunt damping is investigated as one possible solution for improving the vibroacoustic behavior of noise-prone lightweight structures. The negative capacitance shunt circuit appears to be the best choice due to its broadband damping effect. Usually, it is built from analog electronic components, such as operational amplifiers, resistors, and capacitors. In terms of damping efficiency and the vibroacoustic behavior of the circuit, the capacitance ratio between the negative capacitance and the inherent capacitance of the piezoelectric transducer is of major concern. For laboratory setups, this ratio may be adjusted manually, but for real applications, this is not suitable due to a lack of damping or the risk of instability of the circuit. Therefore, an improved approach is presented in this article, where a concept for an adaptive negative capacitance circuit is presented. An electronically tunable resistor is used to change the value of the negative capacitance to the best fit for the present conditions. Adjustment laws for the ideal value of this resistor are derived from the transfer function of the whole circuit. Finally, a prototype board is designed and experimentally tested at a beam structure. It can be shown that the adaptive circuit allows a tighter adjustment to the edge of stability resulting in higher damping or, in the case of too high vibration amplitudes, prevents the output voltage from saturating.