Performance Measurement Methodologies and Metrics for Vibration Energy Scavengers

This paper deals with measurement methodologies for establishing indicators and metrics in order to assess the performance of vibration energy scavengers. The measurement method proposed here is based on the analysis of the flow of energy through several sections of the harvester, which sometime can include complex architectures and nonlinear phenomena. It is worth noting that the proposed solution is applicable not only to linear transducers in presence of periodic vibration source, as mainly proposed in the literature, but also to nonlinear harvester with its conditioning architectures/circuits and in presence of both stochastic and periodic sources. In this context, all the features have been studied from a generalized point of view which can be applied to study a wide range of Lead Zirconate Titanate-based architectures also exploring the effect of parameters variation, transducer architecture, and its consequence in terms of output performance as function of the kinetic input energy parameters. In particular, we outline a new metric addressing the limits of current solutions which the focus on a specific prototype composed of a single transduction element. This paper develops, from theory, a metric for analyzing the implementation of a performance measurement strategy and, in order to experimentally validate this methodology, considers four case studies, which represent the most popular architectures of scavengers proposed in the literature. The metric is first introduced, than the principle of the transducers under analysis is presented, analytical models have been developed, then, numerical analyses have been performed and the obtained behaviors have been validated from an experimental point of view, including characterization and performance evaluation; a comparison as respect the current figure of merits, applied in a specific device, has also been accomplished highlighting the suitability of the proposed methodology.