A multiple degree-of-freedom velocity amplified vibrational energy harvester: experimental analysis and modelling

A macroscopic two degree-of-freedom (2Dof) nonlinear energy harvester, which employs velocity amplification to enhance the power scavenged from ambient vibrations, is presented. Velocity amplification is achieved through sequential collisions between free-moving masses, and the final velocity is proportional to the mass ratio and the number of masses. Electromagnetic induction is chosen as the transduction mechanism because it can be readily implemented in a device which uses velocity amplification. The prototype was tested experimentally under both sinusoidal excitation and exponentially correlated Gaussian noise, with different geometries and a model, which takes into account both transfer of forces through springs, inelastic impacts and free motion of the masses, was developed. The aim of this investigation is to achieve a more complete understanding of the dynamics of velocity amplified systems in order to develop a MEMS scale multi-degree-of-freedom device.