Piezoelectric Energy Harvesting Performance Of D₁₅ Mode PZT Bimorph Cantilever With Series/Parallel Connection

During the past decade, piezoelectric energy harvester from ambient vibration sourceshas been a hot research topic due to its potential for application in micro-wireless sensors andportable electronics. Cantilever energy device has attracted considerable attention due to itsadvantages such as they have simple structure, no fever, no electromagnetic interference,non-pollution and easy to manufacture and implementation mechanism of miniaturization. Ingeneral, piezoelectric materials for captive to piezoelectric cantilever device correspondingpiezoelectric coefficient is higher, the output voltage and power greater. Therefore,piezoelectric coefficient as one of the important indicators of piezoelectric energy harvestingattracted extensive research and attention by the researchers. The piezoelectric coefficients ofsome piezoelectric materials are usually large in the order of d15> d33>d31. In this study,focused on the cantilevered bimorph and based on the high shear piezoelectric coefficient, themain contents are given as follows:(1)Based on the piezoelectric ceramic material has the characteristics of piezoelectriccoefficient larger shear d15, we investigated the energy harvesting performances of the d15mode cantilever piezoelectric bimorph beam in series and parallel connection by using theTimoshenko beam theory. The output peak voltage-frequency and the output peakpower-frequency curves were simulated by using the proposed model and the finite elementsimulation at different load resistances. The variations of the output peak voltage and powerwith load resistance change for excitation are also discussed. Moreover, the effect of proofmass on the energy harvesting performance is analyzed at certain load resistance. The resultsare in good agreement with the finite element simulation results, indicating that the proposedmodel is valid for evaluating the energy harvesting performances of the cantileveredpiezoelectric bimorph. The proposed model can be used for the structure optimized designand performance improvement of shear mode piezoelectric energy harvesting.(2)A d15mode cantilever energy device with two piezoelectric elements in parallelconnection was fabricated based on the high shear piezoelectric coefficient of PZT-51ceramic, and the dependences of the output peak-to-peak voltage and the output power onfrequency were studied at various load resistances. The resonance transient output voltage andthe dependence curve of the peak-to-peak voltage on the vibration excitation voltage weremeasured at various load resistances. At the frequency of50Hz and the load resistance of100k, the output peak to peak voltage and the output power of cantilever energy device are4.56V and103.97μW. With increasing vibration excitation voltage, the output peak-to-peak voltage of cantilever energy device increases. The proposed structure would provide usefulguidelines for the design of d15mode piezoelectric energy harvesters.