Passive self-tuning energy harvester for extracting energy from rotational motion

This paper presents experiments and models of a passive self-tuning energy harvester for rotational vibration applications. Tensile stress due to centrifugal force in a radially oriented piezoelectric cantilever beam passively tunes the resonant frequency so that the harvester remains at or near its resonant frequency. Because centrifugal force is proportional to the square of driving frequency, the resonant frequency of an optimized harvester can track and match the driving frequency over a wide frequency range. An analytical model is presented to explain the harvester’s operation, advantages, and design parameter selection. A prototype demonstrated significantly improved performance compared with an untuned harvester.