This paper describes the design and analysis of a novel energy harvesting device that uses magnetic restoring forces to levitate an oscillating center magnet. The mathematical model for the energy harvesting device is derived and then examined for the case of harmonic base excitation. Perhaps an interesting aspect is that the governing equation for relative displacement reduces to the form of Duffing's equation. The present investigations reveal that engaging the nonlinear response of system can result in relatively large oscillations over a wider range of frequencies - thus potentially improving the ability to harvest energy under certain circumstances. Expressions that consider the coupling between the mechanical and electrical domains are derived for the instantaneous, maximum, and average power. Unlike energy harvesting devices that operate within a linear regime, the excitation frequency where the maximum power is delivered to the electrical load can be at a frequency away from linear resonance. Thus an expression for the excitation frequency has been developed where maximum power occurs. The nonlinear response behavior of the harvester is shown to be strongly dependent on the damping level. Although expressions have been derived for the interplay between the parameters of the mechanical system and the electrically induced damping, it has not been explicitly explored the maximum power output for the experimental system. This was omitted because it has been recognized that an excessive level of input excitation would have been required to engage the nonlinear behavior - due to the relatively large mechanical damping. However, some practical improvements to the presented design, such as the implementation of methods to reduce the damping due to frictional contact between surfaces, could be implemented to reduce the mechanical damping. The coexisting periodic solutions provide an additional complication that is not observed in the linear counterpart. Specifically, both low- and a high-energy responses can coexists for the same parameter combinations. However, it is suggested that one could use the coupling between the electrical circuit and mechanical oscillations to trigger a jump to the more desirable attractor. The developed theoretical studies are compared with a series of experimental tests to confirm the response behavior of the experimental system. As was noted previously, the response behavior of the experimental system is shown to compare favorably with theoretical predictions.
Energy harvesting from the nonlinear oscillations of magnetic levitation
Energiegewinnung aus nichtlinearen Schwingungen der Magnetschwebetechnik
Journal of Sound and Vibration ; 319 , 1/2 ; 515-530
2009
16 Seiten, 9 Bilder, 1 Tabelle, 17 Quellen
Article (Journal)
English
Energy harvesting from the nonlinear oscillations of magnetic levitation
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