An EPM-based Variable Stiffness Oscillator for Vibration Energy Harvesting

AbstractThis study presents a novel variable stiffness oscillator for vibration energy harvesting with resonant frequency tunability. Methods of tuning frequency include changing dimensions, moving center of gravity of the proofmass, and adding positive or negative stiffness in electrostatic ways, piezoelectric ways, or magnetic ways. In this study, an EPM-based variable stiffness mechanism for a vibration energy harvester was proposed and applied to a cantilever oscillator to examine its basic performance. It was described that the holding force of the EPM significantly depended on the activation process, and it was important to realize the full activation to exploit the potential performance of the EPM. Then, it was shown that the resonance frequency of the cantilever oscillator can be changed from 26Hz to 42 Hz when the EPM placed in the middle of the beam was fully activated, while the partially activated EPM could not maintain the resonance because of its weak holding force.