Vibration energy harvesting enhancement exploiting magnetically coupled bistable and linear harvesters

Many common environmental vibration sources exhibit low and broad frequency spectra. In order to exploit such excitations, energy harvesting architectures utilizing nonlinearity, especially bistability, have been extensively explored as a promising energy source for self-powered small-scale electric devices. For such devices, the energetic interwell oscillations between their stable equilibria can provide enhanced power harvesting capability over a wider bandwidth compared to the linear counterpart. Yet, one of the limitations of these nonlinear architectures is that the interwell oscillation regime may not be readily activated for low excitation level that is not sufficient to overcome the potential energy barrier, thus resulting in low amplitude intrawell response, which provides poor energy harvesting performance. This research investigates a multi-degree of freedom (MDOF) vibration energy harvesting system that leverages magnetically coupled bistable and linear harvesters. It presents novel in-depth insights into capitalizing on a passive mechanism that not only facilitates the energetic interwell response for relatively low excitation amplitudes and frequencies than that may be required for conventional bistable harvester by passively and adaptively lowering the potential energy barrier level, but also effectively exploits the redistributed dynamic energy and the rich MDOF dynamic characteristics introduced by the magnetically coupled linear harvester. It is found that in addition to the enhanced power harvesting performance of bistable harvester with adaptive potential, the power captured from the redistributed energy and the higher harmonic resonances introduced by the passive mechanism further increase the energy harvesting performance especially at the lower frequency range. Analytical, numerical, and experimental investigations reveal that strategically incorporating a linear harvester magnetically coupled to a conventional bistable harvester provides an effective and easy to implement means for enhancing broadband energy harvesting performance.