Numerical and experimental study of a compressive-mode energy harvester under random excitations

Piezoelectric energy harvester working in compressive mode has shown outstanding performance under harmonic excitation. However, it is still not clear if the compressive-mode energy harvester can sustain its superiority under random excitations. This paper presents a theoretical and experimental study on a nonlinear compressive-mode piezoelectric energy harvester under random excitations. First, a comprehensive distributed parameter electro-elastic model is developed using the extended Hamilton's principle and the Euler-Bernoulli beam theory. The embedded force amplification effect of the flexural motion is analytically predicted. Then, the model is numerically solved under random excitations. Strong nonlinear responses was observed in both mechanical and electrical responses. Furthermore, a prototype was fabricated and tested. The experimental data show a good agreement with the model estimations under different level excitations and resistances. The results under random excitation demonstrate that the compressive-mode energy harvester significantly outperforms the state-of-the-art systems in terms of output voltage and normalized power density. If the optimal resistance is chosen in the harvesting circuit, the root mean square power of the prototype will reach three times higher than that of the counterparts.