科研之友
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摘要
For improving harvesting ability and adjusting resonant frequency, magnetic energy harvesters using functionally graded composite cantilever are analyzed theoretically. Simultaneously, output voltage of the harvester composed of homogeneous materials is measured experimentally to verify the developed model. In the theoretical model, functionally graded properties with a power-law distribution along the thickness are considered for piezoelectric and substructure layers. Two types of harvesters are designed based on the surface material properties of piezoelectric bimorph. The outputs (electric current, voltage, power etc.) under closed-circuit condition with impedance are derived. When the impedance value tends to infinity, the model successfully reduces to the one for magnetic sensors under open-circuit condition. The influence of the driven frequency, power n and impedance value on output power is studied in detail. Some comparisons are made between two harvesters to select the one with superiority. Then, the influence of substructure's thickness is analyzed. Finally, two available methods are put forward to broaden the responsive frequency range. The numerical results show that the introduction of functionally graded materials can enhance the magneto-mechano-electric coupling effect of harvesters. Different optimal impedances values can be obtained under different frequencies and n values, with whom the best harvesting ability is achieved. Moreover, the resonant frequency of the cantilever is effectively tuned by altering parameters. For the harvester composed of homogeneous materials, the theoretical results agree well with experimental data.
