Abstract
The mechanical amplification effect of parametric resonance has the potential to outperform direct resonance by over an order of magnitude in terms of power output. However, the excitation must first overcome the damping-dependent initiation threshold amplitude prior to accessing this more profitable region. In addition to activating the principal (1st order) parametric resonance at twice the natural frequency ω0, higher orders of parametric resonance may be accessed when the excitation frequency is in the vicinity of 2ω0/n for integer n. Together with the passive design approaches previously developed to reduce the initiation threshold to access the principal parametric resonance, vacuum packaging (< 10 torr) is employed to further reduce the threshold and unveil the higher orders. A vacuum packaged MEMS electrostatic harvester (0.278 mm3) exhibited 4 and 5 parametric resonance peaks at room pressure and vacuum respectively when scanned up to 10 g. At 5.1 ms−2, a peak power output of 20.8 nW and 166 nW is recorded for direct and principal parametric resonance respectively at atmospheric pressure; while a peak power output of 60.9 nW and 324 nW is observed for the respective resonant peaks in vacuum. Additionally, unlike direct resonance, the operational frequency bandwidth of parametric resonance broadens with lower damping.
Highlights
In addition to the conventional use of direct resonance for resonant-based vibration energy harvesting, parametric resonance has been previously demonstrated as a potential superior resonant mechanism in terms of peak power attainable at certain conditions [1]
The initiation threshold for various resonant peaks and their power response per excitation acceleration is given by table 1 and figure 6
The onset of the additional fifth parametric order for the vacuum packaged device was at significantly higher amplitude than that of the first four orders and the power response rapidly attained a high level upon accessing the parametric regime. This implies a lower true initiation threshold exists for the fifth order and the potential presence of further higher orders for both atmospheric pressure operation and vacuum packaged devices within the scanned acceleration range; these additional instability regions have been experimentally elusive due to the impractically narrow operational frequency bandwidth for the frequency sweeps to reveal
Summary
In addition to the conventional use of direct resonance for resonant-based vibration energy harvesting, parametric resonance has been previously demonstrated as a potential superior resonant mechanism in terms of peak power attainable at certain conditions [1]. The supposedly anchored end of the cantilever is coupled to the centre of an orthogonal clamped-clamped beam, which acts as the initial spring for the amplification of the base excitation that is fed into the parametric resonator (the cantilever). This threshold-aid design has been previously shown to decrease the initiation threshold of an otherwise sole cantilever structure by over an order of magnitude [1].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
