Improved nonlinear energy harvester with matched magnetic orientation
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© 2016 SPIE. This paper reports a numerical-experimental study of a nonlinear electromagnetic device consisting of a cantilever beam, tip magnets, tip coil and external side magnets to harvest ambient low-frequency vibration based on Faraday's law of induction. Two external side magnets are deployed symmetrically along a concave surface parallel to the trajectory of the cantilever tip with a controllable distance so that the magnetic orientation of the tip magnets are matched with that of the side magnets. The magnetic force and magnetic flux at the cantilever tip therefore depend on the relative distance between tip magnets on the trajectory and side magnets on the concave surface. The magnetic force (flux)-distance relationship is measured experimentally and curve fitted to characterize the magnetic force (flux) when side magnets are placed at varied positions along the concave surface. Numerical simulation is then performed to study the interrelationship of the position parameters (h, d, a) in order to predict the electromagnetic voltage output. The simulation results agree well with the measured data. Significant broadband response is obtained experimentally and the maximum RMS power output is 40.2 mW at 0.45 g excitation. The systematic analysis and numerical simulation is accomplished to investigate the harvesting performance while only few experimental data is needed, attributing to the matched magnetic orientation of the nonlinear energy harvester proposed here.
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