Exploiting the advantages of the centrifugal softening effect in rotational impact energy harvesting

This Letter presents a rotational impact energy harvester by utilizing the centrifugal softening effect of an inverted driving beam in improving the energy harvesting performance of two piezoelectric beams at low rotational frequencies. By our proposed structure, the static divergence of the inverted driving beam in the deflected mode can not only be avoided but also be utilized. Numerical and experimental results show that the centrifugal softening effect can amplify the relative motion between the driving and generating beams and increase the impact force, which in turn improves the output power significantly. The maximum output power of the harvester is increased by 212.5%, 258.7%, and 682.8% for the impact gaps of 1.07 mm, 1.43 mm, and 2.14 mm, respectively. Moreover, the inverted driving beam can be prevented from continuously deflecting by introducing large impact stiffness at the contact instant.