Vibration energy harvesting by magnetostrictive material

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A new class of vibration energy harvester based on magnetostrictive material (MsM),Metglas 2605SC, is designed, developed and tested. It contains two submodules: an MsMharvesting device and an energy harvesting circuit. Compared to piezoelectric materials,the Metglas 2605SC offers advantages including higher energy conversion efficiency, longerlife cycles, lack of depolarization and higher flexibility to survive in strong ambientvibrations. To enhance the energy conversion efficiency and alleviate the need of a biasmagnetic field, Metglas ribbons are transversely annealed by a strong magnetic fieldalong their width direction. To analyze the MsM harvesting device a generalizedelectromechanical circuit model is derived from Hamilton’s principle in conjunction withthe normal mode superposition method based on Euler–Bernoulli beam theory. The MsMharvesting device is equivalent to an electromechanical gyrator in series with an inductor.In addition, the proposed model can be readily extended to a more practical case of acantilever beam element with a tip mass. The energy harvesting circuit, whichinterfaces with a wireless sensor and accumulates the harvested energy into anultracapacitor, is designed on a printed circuit board (PCB) with plane dimension25 mm × 35 mm. It mainly consists of a voltage quadrupler, a 3 F ultracapacitor and a smartregulator. The output DC voltage from the PCB can be adjusted within 2.0–5.5 V. Inexperiments, the maximum output power and power density on the resistor can reach200 µW and 900 µW cm−3, respectively, at a low frequency of 58 Hz. For a working prototype undera vibration with resonance frequency of 1.1 kHz and peak acceleration of8.06 m s−2 (0.82 g), the average power and power density during charging the ultracapacitor can achieve576 µW and 606 µW cm−3, respectively, which compete favorably with piezoelectric vibration energy harvesters.