A bi-stable horizontal diamagnetic levitation based low frequency vibration energy harvester

Abstract

A new form of bi-stable system based on the passive friction-free horizontal diamagnetic levitation mechanism is proposed in this article. The system is comprised of twelve magnets which create a bi-stable potential well for a centrally located floating magnet. The levitation is stabilized in the horizontal direction by the diamagnetic repulsion from pyrolytic graphite plates which are placed on either side of the floating magnet. Theoretical modeling is discussed involving the superposition of the magnetic fields and magnetic forces, which include semi-analytical equations, from the various magnets in the system to determine the characteristics of the bi-stable potential well. Stability equations for achieving static bi-stability and for maintaining stable levitation during intra-well and inter-well motion were discussed. An experimental prototype is presented whose frequency response characteristics were validated for varying input sinusoidal excitations. Once the dynamics of the bi-stable system were validated, copper coils are incorporated into the diamagnetic plates to enable the vibration energy harvesting capability of the levitation mechanism. The floating magnet underwent chaotic and interwell motions for a range of input sinusoidal excitation frequencies, 5.8 Hz – 8 Hz, at input accelerations of 1.99 m/s2 to 3.79 m/s2, and peak system efficiencies of close to 2.5% were achieved.