Modeling piezoelectric harvesters under amplitude and frequency modulated vibrations

The prediction of the extractable power from energy harvesting devices is of utmost interest for system designers. In this paper, this issue is addressed in the case of Piezoelectric Resonant Vibration Energy Harvesters (PRVEHs) driven by amplitude and frequency modulated vibrations. The widespread architecture of PRVEH systems made up of a passive rectifier cascaded by a DC/DC converter is here considered. An analytical expression of the harvested power as a function of the voltage at the output of the passive rectifier is derived for the cases of vibrations with amplitude modulation and frequency modulation. Further, an analytical-numerical formula is presented for PRVEHs fed by non-sinusoidal vibrations exhibiting envelope and frequency with slow variations. Numerical simulations confirm the theoretical results.