A Novel Passive-Self-Tuning Energy Harvester

To capture the maximum induced vibrational energy, it is crucial to have near-resonance vibrations in an energy harvester. This can be accomplished by passive self-tuning resonators which can adapt themselves to the excitation frequency. However, the existing self-tuning beam resonators can only, due to the gravity field, operate when they are placed horizontally, which makes it impossible to be used in mobile electronic devices. In this paper, we introduce a novel concept of beam resonators that is neutral to any orientation with respect to the gravity field and, thus, can be employed in mobile electronic devices. In this study, the influence of preload on the modal behavior is also analytically and numerically investigated. Finally, with the aid of a nonlinear finite element simulation, we propose using preload in order to further optimize the performance of self-tuning beam resonators.