Research Papers

A Horizontal Diamagnetic Levitation Based Low Frequency Vibration Energy Harvester

[+] Author and Article Information
S. Palagummi

Department of Mechanical
and Aerospace Engineering,
North Carolina State University,
Raleigh, NC 27695 
e-mail: spalagu@ncsu.edu

J. Zou

Department of Mechanical
and Aerospace Engineering,
North Carolina State University,
Raleigh, NC 27695 
e-mail: jzou@ncsu.edu

F. G. Yuan

Department of Mechanical
and Aerospace Engineering,
North Carolina State University,
Raleigh, NC 27695
College of Mechanical and Vehicle Engineering,
Hunan University,
Changsha, Hunan 410082, China
e-mail: yuan@ncsu.edu

Contributed by the Technical Committee on Vibration and Sound of ASME for publication in the JOURNAL OF VIBRATION AND ACOUSTICS. Manuscript received January 7, 2015; final manuscript received May 17, 2015; published online July 9, 2015. Assoc. Editor: Patrick S. Keogh.

J. Vib. Acoust 137(6), 061004 (Dec 01, 2015) (10 pages) Paper No: VIB-15-1007; doi: 10.1115/1.4030665 History: Received January 07, 2015; Revised May 17, 2015; Online July 09, 2015

This paper investigates a horizontal diamagnetic levitation (HDL) system for vibration energy harvesting in contrast to the vertical diamagnetic levitation (VDL) system recently proposed by Wang et al. (2013, “A Magnetically Levitated Vibration Energy Harvester,” Smart Mater. Struct., 22(5), p. 055016). In this configuration, two large magnets, alias lifting magnets (LMs), are arranged co-axially at a distance such that in between them a magnet, alias floating magnet (FM), is passively levitated at a laterally offset equilibrium position. The levitation is stabilized in the horizontal direction by two diamagnetic plates (DPs) made of pyrolytic graphite placed on each side of the FM. This HDL configuration mitigates the limitation on the amplitude of the FM imposed in the VDL configuration and exploits the ability to tailor the geometry to meet specific applications due to its frequency tuning capability. A simple circular coil geometry is designed to replace a portion of the pyrolytic graphite plate without sacrificing the stability of the levitation for transduction. An experimental setup exhibits a weak softening frequency response and validates the theoretical findings; at an input root mean square (RMS) acceleration of 0.0434 m/s2 and at a resonant frequency of 1.2 Hz, the prototype generated a RMS power of 3.6 μW with an average system efficiency of 1.93%.

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Fig. 1

Schematic of a HDL system

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Fig. 2

A schematic of the HDL vibration energy harvester system: (a) front view and (b) side section view with the lifting magnets (LM1 and LM2), the diamagnetic plates (DP1 and DP2), the FM, and the copper coil. The lighter shaded FM shows its static equilibrium position whereas the darker shaded FM shows its perturbed dynamic position.

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Fig. 3

(a) Weight balance positions dz of the FM with the LM at the respective dx, (b) restoring force in the x-direction for the dx values taken from (a), (c) zoomed section of (b) at which static levitation is permissible, and (d) restoring force in the y-direction for the dx values taken from (c)

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Fig. 4

(a) Amplitude of FM in the z-direction (zmax) for different dx and (b) restoring force in the z-direction for varying dx

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Fig. 5

Restoring force in the x-direction at different z amplitudes

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Fig. 6

(a) Restoring force in the x-direction, (b) in the y-direction, and (c) in the z-direction

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Fig. 7

(a) Ring-down of the FM using a high-speed camera and (b) parametric sweep to determine coilout

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Fig. 8

An equivalent 1DOF model of the HDL based vibration energy harvester

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Fig. 9

Schematic of the coil geometry for (a) voltage induced calculation for the coil (V(z,z·) in Eq. (7)) and (b) Lorentz force calculation due to current in the coil (FL (i, z) in Eq. (8)

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Fig. 10

Experimental system for HDL based vibration energy harvester

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Fig. 11

Close-up of the HDL vibration energy harvester showing the FM, the LM, and the pyrolytic graphite with the copper coil

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Fig. 12

Experimental and theoretical predictions (a) relative amplitude of the FM, (b) RMS voltage across the load, (c) RMS power, and (d) average efficiency of the system. (RMS excitation acceleration varied from 0.028 m/s2 to 0.0678 m/s2 as the frequency was varied from 0.5 Hz to 3 Hz.)

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Fig. 13

FM and LM modeled as thin coils with equivalent magnetic moment




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