A novel piezoelectric energy harvester with a multi-mode dynamic magnifier, which is capable of significantly increasing the bandwidth and the energy harvested from the ambient vibration, is proposed and investigated in this paper. The design comprises a multi-mode intermediate beam with a tip mass, called a 'dynamic magnifier', and an 'energy harvesting beam' with a tip mass. The piezoelectric film is adhered to the harvesting beam to harvest the vibration energy. By properly designing the parameters, such as the length, width and thickness of the two beams and the weight of the two tip masses, we can magnify the motion virtually in all the resonance frequencies of the energy harvesting beam, in a similar way as designing a new beam-type tuned mass damper (TMD) to damp the resonance frequencies of all the modes of the primary beam. Theoretical analysis, finite element simulation, and the experiment study are carried out. The results show that voltage produced by the harvesting beam is amplified for efficient energy harvesting over a broader frequency range, while the peaks of the first three modes of the primary beam can be effectively mitigated simultaneously. The experiment demonstrates 25.5 times more energy harvesting capacity than the conventional cantilever type harvester in the frequency range 3-300Hz, and 100-1000 times more energy around all the first three resonances of the harvesting beam.
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