Rolling mass energy harvester for very low frequency of input vibrations

This paper presents a novel design of a nonlinear kinetic energy harvester for very low excitation frequencies below 10 Hz. The design is based on a proof mass, rolling in a circular cavity in a Tusi couple configuration. This allows for an unconstrained displacement of the proof mass while maintaining the option of keeping the energy transduction element engaged during the whole cycle and thus reducing the required number of transduction elements. Both the presented model and the fabricated prototype of the device employ electromagnetic induction to harvest energy from low frequency and low magnitude vibrations that are typically associated with human movements. The prototype demonstrated an average power of 5.1 mW from a 1.3 g periodic acceleration waveform at 2.78 Hz. The highest simulated normalized power density reaches up to 230 mu W/g(2)/cm(3), but this depends heavily on the excitation conditions. (C) 2018 Elsevier Ltd. All rights reserved.