The piezoelectric stack energy harvester(PSEH)is often used to transform ambient large amplitude vibrational energy,such as road vibrations and pressure fluctuations,because of its ability to withstand large external excitation force.However,due to the high natural frequency of the piezoelectric stack,it is difficult to generate resonance phenomenon,which leads to low energy efficiency for the energy harvester.In this paper,a piezoelectric stack energy harvester with force magnification frame(FMF)is proposed and studied for energy harvesting from low-frequency pressure ripples.First,a force magnification frame is designed to enhance the pressure transferring ability.The FMF is able to,not only amplify the exciting force acting on the piezoelectric stack but also decrease the natural frequency of the PSEH.Based on finite element method(FEM)analysis,the natural frequency of the PSEH with FMF is obtained.The natural frequency of the PSEH is successfully reduced,and the open-circuit voltage output of the PSEH under low-frequency resonance conditions is much higher than for off-resonance conditions.The results validate that the PSEH with FMF is efficient for lower frequency vibration environments.
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