On the effect of driving amplitude, frequency and frequency-amplitude interaction on piezoelectric generated power for MFC unimorph

In this paper, an experimental study on effects of frequency, amplitude and frequency-amplitude interaction of base excitation on vibration piezoelectric energy harvesters is presented. To do so, a unimorph piezoelectric harvester made from macro fiber composite (MFC) piezoelectric layer is tested. A two-factor factorial design with two replications is considered, in which frequency and amplitude of driving vibration are the treatment factors. For changing treatment factors, an appropriate frequency range is considered to include the device fundamental frequency and three excitation levels are considered. In order to investigate the effects of treatment factors on the power output, a linear model is considered. Results show that increasing amplitude of excitation vibration causes a stiffness softening behavior of the piezoelectric oscillatory beam leading to reduction in the harvester natural frequency. In addition, from the frequency-amplitude interaction analysis, output power is much more sensitive to vibration amplitude for driving frequencies near the harvester natural frequency compared to frequencies far away from the harvester natural frequency.