Dynamic and energetic characteristics of a bistable frequency up-conversion piezoelectric energy harvester coupled with a nonlinear spring oscillator

In ultralow-frequency and broadband environments, vibration energy harvesters exhibit lower energy harvesting efficiency. This article introduces a bistable vibration energy harvester that leverages a nonlinear spring oscillator to excite a Piezoelectric Energy Harvester (PEH), facilitating the efficient harvest of vibrational energy. We present the theoretical model, numerical analysis, and experimental validation for this system, featuring nonlinear springs and magnetic force to magnetically "pluck" the PEH, inducing superharmonic resonance. The results show that the PEH has complex dynamic phenomena such as intra-well superharmonic orbit, inter-well odd multiple superharmonic orbit, and chaos. The PEH demonstrates efficient energy harvesting capabilities near its natural resonance frequency of 12.66 Hz under low-amplitude (0.19-0.47 g) and ultralow-frequency (2.93-4.57 Hz) excitations. Remarkably, when the PEH's natural frequency aligns as triple of the excitation frequency, its vibrational energy significantly increases, highlighting its potential for optimal energy harvesting in environments characterized by low-amplitude and ultralow-frequency vibrations.