shape design optimization of unimorph piezoelectric cantilever energy harvester

the most promising method for micro scale energy scavenging is via vibration energy harvesting which converts mechanical energy to electrical energy by the effect of coupling between electric fields and mechanical variables. using piezoelectric cantilevers is the most common method for vibration energy harvesting. changing the shape of the cantilevers can lead to changing the generated output voltage and power. in this work vibration energy harvesting via piezoelectric resonant unimorph cantilevers is studied and new design for obtaining more efficient piezoelectric energy harvester is suggested. this study provides comprehensive analysis of the output voltage relationships and deducing a considerable precise rule of thumb for calculating resonance frequency in cantilever-type unimorph piezoelectric energy harvesters using rayleigh method. the analytical formula, is then analyzed using matlab and mathematica as well as finite element methods and verified by fem simulation in abaqus. the analytical data was found to be very close to simulation data. a key finding is that among all the unimorph trapezoidal v-shaped cantilever beams with uniform thickness, the triangular tapered cantilever, can lead to highest resonance frequency and by increasing the ratio of the trapezoidal bases, the resonance frequency decreases. also the possible analytical relations for a triangular cantilever beam are evaluated and the nearest exponentially tapered shape to triangular cantilever is proposed. these new findings provide guidelines on system parameters that can be manipulated for more efficient performance in different ambient source conditions.