Electrodynamic resonant energy harvester for low frequencies and amplitudes

Vibration is a suitable source for powering wireless sensors because of its energy level. A high energy output can be only reached by an appropriate harvester design taking the parameters of the available vibration into account. Very often ambient vibration sources have relative low frequencies and amplitudes. In this paper, a novel cylindrical electrodynamic resonant vibration converter is developed for low frequency and low amplitude. The design envisages a fixed coil to have a reliable connection to energy management electronic. For repulsion forces a magnetic spring is proposed to ovoid friction and aging effects of mechanical springs. This ensures a high reliability and compactness of the system. The design parameters have been optimized by finite element method modeling and by experiments. In order to validate the simulation results, an experimental setup for the converter is realized. An evaluation for the generated energy is also treated. The results show that the harvester is able to generate 470 mV for frequency excitation equal to 26 Hz and a low amplitude vibration equal to 1 mm. For the power output evaluation, the optimal load resistance is close to the coil resistance which is equal to 34 Ω and the converter is able to generate 0.72 mW.