This paper shows how to enhance the vibration attenuation obtained by means of piezoelectric resistive shunt coupled to the use of negative capacitances. This improvement is achieved by adding an inductance in the shunt circuit. This additional inductance is not used to the usual purpose of mono-modal control, but to improve the attenuation in a broader frequency range. The benefits offered by the use of the inductance are explained by describing the shunted electro-mechanical system as a feedback control loop. The achievable attenuation improvements are highlighted in the paper at first through numerical analyses and then by means of an experimental campaign which also allows to evidence the reliability of the model employed to describe the electro-mechanical system.

The use of shunt of piezoelectric transducers to damp mechanical vibrations is an interesting approach thanks to its low cost and the light weight of the actuators used. Among the different ways to build the shunt impedance, the use of negative capacitances is very attractive because it allows for high damping performances with low power required by the control system. Negative capacitances do not exist in the actual world but they can be designed and built using circuits based on operational amplifiers. The use of shunt circuits based on a negative capacitance coupled to a resistance allows to have a broadband control. This paper explains how to increase the bandwidth of the controller by adding to such a shunt circuit an inductance. The dynamics of the controlled system is solved analytically and the reason why the introduction of the inductance is able to give the mentioned improvement is made clear also using numerical simulations. Furthermore, this improvement also allows to increase the attenuation performance. The conditions necessary to assure the stability of the electro-mechanical system are found and explained.