Self-Tuning Analog Shunts for Modular Piezoelectric Vibration Absorbers

This article proposes a modular semi-active vibration control unit formed by a piezoelectric patch with a model-free self-tuning analog shunt, which can be bonded in batches on flexible structures to control the resonant responses of low-order flexural modes. Unlike conventional self-tuning systems, this unit does not require additional sensors or digital control. On the contrary, it relies on an analog shunt, which implements an extremum-seeking algorithm that sets the shunt to maximize the time-averaged electrical power absorbed from the vibration of the target flexural mode. The analog shunt includes a separate opto-coupled tuning board, which ensures stable operation and avoids unwanted electrical interactions. In first place, this article describes the architecture of the self-tuning analog shunt and provides general guidelines on how the dithering signal of the extremum seeking algorithm affects its stability and convergence speed. Then, it presents practical tests where five units are bonded on a thin plate to control the resonant response of a single or multiple flexural modes. More specifically, two configurations are investigated: in the first, all units are set to control the resonant response of a specific target mode, which shows reductions of 20–30 dB, whereas in the second, the units are set to control separate target modes, which show reductions of 10–15 dB. These results confirm the potential of the proposed unit, which can be miniaturized and mass-produced to operate straightforwardly on a wide range of structures.