The Role Of Sweep Rate In Energy Harvesting

Piezoelectric-based energy harvesting provides an attractive method of powering remote wireless devices. As such, significant research has been dedicated to studying the performance of such systems, though primarily while operating under steady state conditions. For some applications, however, these conditions are not realistic, and transient analysis must be performed. Of interest here is harvesting in conjunction with a vibration reduction technique, resonance frequency detuning. This technique provides a method of reducing mechanical response at structural resonances for systems with frequency sweep excitations. Inherent to these sweep excitations is an additional parameter rarely studied in energy harvesting research, the sweep rate. This paper addresses the role of the sweep rate in energy harvesting systems, with particular interest on how the power output and vibration response of the system respond to changes in sweep rate. Varying the sweep rate is shown to have an analogous effect to varying the modal damping ratio in steady-state systems, suggesting the frequency sweep may act as an additional source of damping. It is shown that the optimal power output bifurcates as the sweep rate drops below a particular value, similar to the concept of the bifurcation damping ratio