A dual electromagnetic array with intrinsic frequency up-conversion for broadband vibrational energy harvesting
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abstract
This letter proposes a dual electromagnetic array to transform low frequency rectilinear vibrations into electricity with frequency up-conversion. The free of mechanical contact harvester consists of a rectilinear oscillator (RLO) and an array of two identical rotary oscillators (RTO). The RTO includes a rotor and a stator. The rotor has eight cubic magnets distributed centrosymmetrically, and the stator has eight coils. Under rectilinear vibrational excitations, the RLO drives the rotor of the RTO to rotate through magnetic torque acting on the rotors. A slight fluctuation of the rectilinear motion can lead to a great change of torque, which converts the low frequency vibrations into high frequency rotational motions. By adopting the frequency up-conversion mechanism, a high instantaneous output voltage is produced and maintained from 3.0Hz to 9.5Hz. Experiments show that with the dual rotor array, the output power is improved and the RLO is able to oscillate at its resonance even if the input frequency is greater than its resonant frequency, which implies a potential solution to suppress and harvest vibration energy during an earthquake if properly arraying multiple rotors. Under the excitation of 0.5g and 4.0Hz, the harvester can provide a stable DC power of 3.1 mW after AC-DC conversion.
