Theoretical, numerical, and experimental studies of a frequency up-conversion piezoelectric energy harvester

This paper presents the study of a two-degree-of-freedom (2DoF) stacked piezoelectric energy harvester (SPEH). The high performance of the 2DoF SPEH is achieved by the frequency up-conversion mechanism, which is realized by introducing a mechanical limiter. A theoretical model of the 2DoF SPEH is developed. A piecewise linear function describes the impact interaction that incurs the frequency up-conversion phenomenon. The approximated analytical solution is derived using the averaging method. Moreover, an equivalent circuit model (ECM) is established to capture the dynamic characteristics of the SPEH. Experiments are conducted to validate the theoretical and ECM models. The effects of system parameters on the SPEH's output performance are investigated. Due to the impact-induced amplitude truncation effect, the operation bandwidth of the SPEH is substantially enlarged. For instance, the bandwidth was expanded to 6.3 Hz with a sponge gasket. The 2DoF SPEH can produce an instantaneous power with a peak amplitude of 521.6 mW under an excitation of 10.8 Hz with k = 0.098 N/mm. Based on the parametric study results, design guidelines to improve the system for better energy harvesting performance are discussed and summarized.