Experimental characterisation of dual-mass vibration energy harvesters employing velocity amplification

Vibration energy harvesting extracts energy from the environment and can mitigate reliance on battery technology in wireless sensor networks. This article presents the nonlinear responses of two multi-mass vibration energy harvesters that employ a velocity amplification effect. This amplification is achieved by momentum transfer from larger to smaller masses following impact between masses. Two systems are presented that show the evolution of multi-mass vibration energy harvester designs: (1) a simplified prototype that effectively demonstrates the basic principles of the approach and (2) an enhanced design that achieves higher power densities and a wider frequency response. Various configurations are investigated to better understand the nonlinear dynamics and how best to realise future velocity-amplified vibration energy harvesters. The frequency responses of the multi-mass harvesters show that these devices have the potential to reduce risks associated with deploying vibration energy harvester devices in wireless sensor network applications; the wide frequency response reduces the need to re-tune the harvesters following frequency variations of the source vibrations.