Enhancement of Energy Harvested from a Random Vibration Source by Magnetic Coupling of a Piezoelectric Cantilever

It is demonstrated experimentally that the energy harvested from a random noise source by a piezoelectric cantilever can be substantially enhanced by introducing a magnetic coupling force. The coupled cantilever responds to a 1/f vibration spectrum ('pink noise') with chaotic motion that on average has larger amplitude than the non-chaotic motion of an uncoupled cantilever. A 50% increase in output voltage was observed in the coupled cantilever compared to the uncoupled cantilever. Calculations show that the magnetic force transforms the quadratic spring potential of the cantilever into a double valley of two potential wells. Fluctuations between the two potential minima increase the amplitude of the cantilever motion over a range of vibration frequencies.