This letter presents a bi-directional electromagnetic energy harvester (EMEH) that consists of a spherical magnet encapsulated in an arc-shaped tube and two sets of coils wrapped around the tube. Two springs are affixed at the two ends of the tube to reduce the impact-induced energy dissipation and recycle the kinetic energy of the magnet. Experimental studies reveal that the arc-shaped EMEH is capable of capturing energy from ultra-low frequency vibrations that come from two orthogonal directions. Moreover, under the swing motion, the magnet is driven by its geopotential energy to move along the inner surface of the tube and then induce the coils to generate electrical power. Experimental measurements with the arc-shaped EMEH attached on human limbs show that the proposed design could perform simultaneous energy extraction from the vibration and swing motion even though they come from different directions, demonstrating the superior adaptability to the diverse excitations that are abundant in our living environment.
This paper proposes a nonlinear piezoelectric energy harvester (PEH) to scavenge energy from human limb motions. The
proposed PEH is composed of a ferromagnetic ball, a sleeve, and two piezoelectric cantilever beams each with a
magnetic tip mass. The ball is used to sense the swing motions of human limbs and excite the beams to vibrate. The two
beams, which are sensitive to the excitation along the radialis or tibial axis, generate electrical outputs. Theoretical and
experimental studies are carried out to examine the performance of the proposed PEH when it is fixed at the wrist, thigh
and ankle of a male who travels at constant velocities of 2 km/h, 4 km/h, 6 km/h, and 8 km/h on a treadmill. The results
indicate that the low-frequency swing motions of human limbs are converted to higher-frequency vibrations of
piezoelectric beams. During each gait cycle, different excitations produced by human limbs can be superposed and
multiple peaks in the voltage output can be generated by the proposed PEH. Moreover, the voltage outputs of the PEH
increase monotonously with the walking speed, and the maximum effective voltage is obtained when the PEH is
mounted at the ankle under the walking speed of 8 km/h.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.