Harvesting At The Margins: A Study Of Harvesting Away From Optimal Conditions

Piezoelectric-based vibration energy harvesting is of interest in a wide range of applications, and a number of harvesting schemes have been proposed and studied – primarily when operating under optimal conditions. However, optimal conditions are not always available, so it is necessary to investigate energy harvesting in a more general sense. This approach will therefore relax several common assumptions. Of particular interest here is implementing a vibration reduction technique, resonance frequency detuning, that relies on operation near the short-circuit and open-circuit conditions. While energy harvesting research is largely concerned with maximizing power output and operation under optimal conditions, this effort focuses on harvesting “at the margins, -that is, near the shortcircuit and open-circuit conditions. Such behavior is not well understood, and this paper will work to improve this understanding. As a metric for studying this behavior, an effective stiffness for the structure is derived, and its inuence on power output is investigated. Results show that high stiffness control can be achieved by switching between the “margins, as a small shift in this effective stiffness is shown to have a significant impact on the harvested power