Health and usage monitoring systems (HUMS) is an emerging market for industries to make their products “smart” while decreasing the inspection cost and risk of failure during operation. To power different electronic units of HUMS, including sensor nodes, data acquisition and storage systems, and transceivers, energy harvesting is a promising alternative to batteries. For applications where ambient conditions consist of low vibration frequencies and low excitation amplitudes, the challenge of generating reasonable amount of output power becomes imminent. In this work, an optimization method is developed to size the coil of an electromagnetic energy harvester. For a given magnetic structure, two steps of FEM analyses and analytical calculations are performed to determine the coil optimum position, the coil length, and the coil thickness. The dynamic tests on first prototypes showed good correlation between theoretical calculations and experimental results. Contrary to resonant systems with their characteristic peak power only at a specific resonant frequency; here, the energy harvester is operated out of resonance and the generated power increases with excitation frequency (30 μW to 2.2 mW from 3 Hz to 12 Hz with 1 mm vibration amplitude). Eventually the presented device has the potential to be employed as a wideband energy harvester which needs no resonant frequency tuning.
I. Shahosseini, R. L. Peterson, E. E. Aktakka, K. Najafi, “Electromagnetic generator optimization for non-resonant energy harvester,” IEEE Sensors, pp. 178-181, Valencia, Spain, Nov. 2014. [PDF]