Nonlinear dynamics and triboelectric energy harvesting from a three-degree-of-freedom vibro-impact oscillator

A triboelectric energy harvester based on a three-degree-of-freedom vibro-impact oscillator is presented. Both the dynamic model of the oscillator and the theoretical model of the oscillator-based triboelectric energy harvester are established. The dynamic response and its effect on the electrical output are considered for various mass ratios and mass spacings. The study leads to the conclusions that the symmetric mass configurations of the oscillator are more beneficial to energy harvesting than the asymmetric cases. The extent of the initial spacing between the masses influences the dynamics of the system and the electrical output by triggering grazing bifurcation. High-order periodicity is found to accompany a reduction in the electrical power. An increase in mass ratio tends to increase the electrical output, and there may exist an optimal mass ratio at which the electrical output is maximized. Chatter and sticking motion can improve the output performance dramatically, while resonance, as usual, corresponds to large amplitude response, but these large amplitudes are not optimal for triboelectric energy harvesting, and thus the maximal output does not appear around resonance. This is different from other types of vibration-based energy harvesters, such as piezoelectric and magnetoelectric energy harvesters which are usually designed to operate at resonance. In addition, chatter is found to occur at low excitation frequencies, which can help harvest energy from low-frequency ambient vibration.