Improved piezoelectric energy harvester with dual-impact strategy for small acceleration amplitude vibrations

Increasing the operable frequency range and improving the small acceleration amplitude harvesting performance of the piezoelectric energy harvesting devices is importance due to the wide frequency spectrum and large amplitude range of environmental vibrations. In this Letter, an improved piezoelectric energy harvester with frequency upconversion is proposed, which is comprised of a composite piezoelectric beam and a firing pin. In contrast to the conventional impact-based systems that mainly rely on beam vibrations to enhance harvesting performance, the proposed system employs a dual-impact strategy. In particular, an oblique impact-based harvesting phenomenon is observed, which has not been investigated in previous studies. A multilevel impact nonlinear coupled dynamic model is developed. The experimental results indicate that at an excitation acceleration amplitude of 0.15 g, the proposed system demonstrates a 482.9% increase in the output peak value and introduces dual-band frequency in comparison with the conventional structure. Additionally, the proposed coupled model is validated through adjustments to various load resistances. The highest output power is achieved at a load resistance of 210 kΩ, with the maximum average power reaching 3.96 mW and a power density of 1.59 mW/mm3g2 at an acceleration amplitude of 0.15 g, outperforming other piezoelectric energy harvesters.