Time resolved eye diagrams to exploit hidden high energy branches in a nonlinear wideband vibration energy harvester

TL;DR

This paper introduces a novel eye diagram method to analyze and access hidden high-energy branches in a nonlinear wideband vibration energy harvester, significantly improving energy output and understanding of its complex dynamics.

Contribution

It presents a graphical eye diagram approach for characterizing energy branches in nonlinear vibrational harvesters, enabling access to high-energy states and optimizing energy conversion.

Findings

Achieved 1.3mW power output at 44Hz bandwidth

Developed a method to access hidden energy branches

Energy conversion ratio of 0.52 at 120Hz

Abstract

A wideband vibration energy harvester with multiple nonlinear forces is investigated. The nonlinearities are due to repulsive magnets and hardening springs, which gives rise to multistabilities between a number of energy branches. Not all branches are accessible by a simple up or down sweep of the driving frequency and in particular the highest energy branch is often hidden, requiring a suitable frequency schedule to be accessed. Detailed theoretical understanding of the energy branch structure along with robust experimental methods are essential for characterizing each of the energy branches to enhance the energy output from such vibration energy harvesting system. We introduce a graphical representation in the form of eye diagrams based on time-resolved measurements of acceleration and output voltage to study the dynamical features of the different branches. This generic approach allows us to optimize the design, which results in 1.3mW of power generated at 1g over 44Hz frequency bandwidth while maintaining a small footprint of $1.23 cm^3$. The energy conversion ratio of the energy harvester at 120Hz drive frequency is 0.52 for the high energy branch.