Control of Impulsively Excited Vibration Energy Harvesters: Design and Viability Assessment

In energy harvesting technologies, the circuitry used to extract power can be viewed as imposing a feedback law on the harvester’s dynamics. Each circuit topology affords some degree of controllability, and consequently, a feasibility domain over which its feedback law can be optimized to maximize the harvested energy. The parasitic losses associated with a given circuit can be large enough that they are comparable to or exceed the available resource, thus precluding its viability. This article examines these issues for single-degree-of-freedom vibration energy harvesters subjected to a single-impulsive inertial loading. We introduce two different quadratic overbound techniques for parasitic loss modeling: one based on physical circuit parameters and the other based on a static efficiency model. We consider the choice between an active rectifier and active drive circuit to condition the power, and also the choice of whether to include power-factor correction circuitry. The four resultant design combinations represent different tradeoffs between the control functionality and the parasitic loss. For all cases, we illustrate a technique for determining the maximum energy that can be harvested from the impulse using the optimal control theory. We then use this analysis to determine, for each case, whether the parasitic power it must sustain to operate is justified by the performance it achieves. We also determine the critical threshold of parasitic loss, below which a given case is not a viable technology. Finally, we show that the relative favorability of each circuit depends strongly on the characteristics of the harvesting device, as well as the disturbance intensity.