Electrically rectified piezoelectric energy harvesting induced by rotary magnetic plucking

A theoretical framework together with an experimental validation is developed for the investigation of a rotational piezoelectric energy harvester attached to the standard interface circuit for AC-DC conversion. The energy harvester consists of an electrically rectified piezoelectric cantilever beam mounted on a stationary base with a magnet attached to its free end. Energy is harvested by vibration of beam induced by non-contact rotary magnetic plucking. A theoretical model accounting for magnetic coupling and rotary plucking is developed and the phenomenon of frequency up-conversion is realized by the Fourier analysis of the impulsive-like driving force. The analytic estimate of DC harvested power is derived showing that the electric response can be imitated to the case of rectilinear harmonic force vibration whereas the multiplication of the driving frequency and the integer value closely matches the device's fundamental resonance. As a result, it exhibits broadband frequency response due to frequency up-conversion. In addition, the prediction on the crests and troughs of ripples in the DC power frequency response is remarkably found in excellent agreement with experiment. Finally, several design guidelines are proposed. These include power enhancement by lowering the ratio of perpendicular distance of magnetics to the radius of revolution, and the reduction of ripples by requiring larger mechanical damping.