Passive magnetic coupling to enhance piezoelectric cantilever response in energy scavenging applications

This paper describes the use of non-linear magnetic coupling to tune the resonant frequency and bandwidth of a piezoelectric cantilever vibration scavenging system. A piezoelectric cantilever is fitted with a permanent magnet on its free-moving tip, while a second magnet is positioned to attract the magnetized tip. As the separation between the opposing magnets is reduced, the non-linear force introduced by the magnetic coupling down-shifts the resonant frequency of the cantilever beam, and broadens the observed frequency response. The results qualitatively agree with the predictions of a modified spring-mass vibration model.