Design and development of a high-performance tensile-mode piezoelectric energy harvester based on a three-hinged force-amplification mechanism

When considering durability and reliability, flexible piezoelectric materials, such as PVDF and macro-fiber composite, are preferable to piezoceramics due to the brittleness of piezoceramics. However, flexible piezoelectric materials cannot sustain compressive loads so they need to be operated in either tensile or bending mode. The tensile mode has the advantage of uniform strain distribution over the bending mode. This study proposes a novel tensile-mode piezoelectric energy harvester based on a three-hinged force amplification mechanism. The proposed design consists of a rigid beam and an elastic PVDF film connected to each other via a revolute joint. The assembly is attached to a base via revolute joints with the PVDF film pre-stretched. The PVDF film bears a dynamic tensile load when the harvester is under harmonic excitations. A theoretical model of the proposed harvester is developed and experimentally validated. The simulation and experimental results show that the proposed design exhibits a strong hardening effect due to the nonlinear geometry of the three-hinged mechanism. The effect of preloads and mass distributions are explored to see their impact on the harvesting performance. It is shown that the peak voltage and bandwidth of the harvester decline as the preload increases. By properly tuning the mass distribution, the performance of the harvester can be enhanced. Compared with a bending-mode cantilevered harvester, the voltage output and harvesting bandwidth of the proposed harvester can be improved by 500% and 1250%, respectively.