The magnetic coupling of a piezoelectric cantilever for enhanced energy harvesting efficiency

It is shown that the energy harvesting capabilities of a piezoelectric cantilever can be enhanced through coupling to a static magnetic field. A permanent magnet is fixed to the end of a piezoelectric cantilever, causing it to experience a non-linear force as it moves with respect to a stationary magnet. The magnetically coupled cantilever responds to vibration over a much broader frequency range than a standard cantilever, and exhibits non-periodic or chaotic motion. While the off-resonance response is substantially increased compared to that of a standard cantilever, no reduction in the response at the resonant frequency is observed, as long as a symmetric magnetic force is applied. The magnetically coupled cantilever motion is analyzed using a simple driven harmonic oscillator model with a non-linear magnetic force term. The results show that magnetic coupling can be used to increase the amount of power scavenged from environments containing multi-mode, or random vibration sources.