Energy harvesting of random wide-band vibrations with applications to an electro-magnetic rotational energy harvester

Abstract

In general, vibration energy harvesting is the scavenging of ambient vibration by transduction of mechanical kinetic energy into electrical energy. Many mechanical or electro-mechanical systems produce mechanical vibrations. The kinetic energy associated with these mechanical vibrations represents a potential source of energy for sensors and other electronics. In fact, as the energy requirements for electronics and wireless communications systems has reduced, harvested energy from vibrations has been successfully used to power several wireless sensors. However, these sensors are implemented on systems with harmonic vibration sources. Most ambient vibrations are noisy, wide-band, and/or stochastic. As such, a resonant tuned-mass damper, with a narrow band-width, filters and discards much of the energy in the vibration spectrum, or worse, resonant harvesters will not resonate in stochastic environments. Several solutions are commonly proposed for harvesting energy from wide-band excitations; multiple resonators tuned to different frequencies (farm systems), non-linear systems, input excitation rectification, and frequency tuning are the most common. This thesis addresses some of the wide-band and/or stochastic challenges to vibration energy harvesting by investigating vibration energy harvesting as a power source for sensors and communications in a down-hole environment. This thesis shows that regardless of the transducer, a single resonant harvester tuned to the frequency with the maximum displacement times frequency cubed produces more power than a farm of resonant harvesters tuned to a range of frequencies. Additionally, this thesis shows that an electromagnetic harvester can be passively tuned to increase the power in a non-stationary system with a peak frequency that is a function of time. Finally, this thesis presents a new resonant, rotational architecture, which has the advantage of simultaneously maximizing the coupling inertia and displacement.