Performance Dependence on Initial Free-End Levitation of a Magnetically Levitated Piezoelectric Vibration Energy Harvester With a Composite Cantilever Beam

Vibration energy harvesting by using piezoelectric materials provides a promising alternative solution for a wide range of self-powered systems. In this paper, performance dependence on initial freeend levitation position (IFLP) of a magnetically levitated piezoelectric vibration energy harvester (PVEH) with a composite cantilever beam is presented. A prototype consisting of a high-stiffness lead zirconate titanate beam with a proof mass and a flexible brass beam with a tip mass as well as an auxiliary structure adjusting repulsive magnetic force was fabricated to evaluate the IFLP effects. Experimental results showed that the performance of the magnetically levitated PVEH was varied with different IFLPs. With declining of the IFLP, the peak power output at the first resonance frequency decreased monotonically from 1541 to 343.2 μW, meanwhile, the power output initially decreased from 2735.6 to 904.5 μW and then constantly increased from 904.5 to 2220.9 μW at the second resonance frequency. The frequency variation at the first and second resonance points was 1.5 and 4 Hz, respectively. It was found that the IFLP had a stronger impact on the performance when it was above the horizontal orientation than below the horizontal orientation. Moreover, the IFLP brought a more significant influence on the second resonance frequency than the first one. In addition, the IFLP had a larger effect on the power output than the resonance frequency.