Elastic and Electric Damping Effects on Piezoelectric Cantilever Energy Harvesting

Abstract

Piezoelectric cantilever is one of the simplest configurations for energy harvesting. Many reports have shown that the resonances frequency of the piezoelectric energy harvesting (PEH) can be essentially shifted by the proof masses to the lower working frequencies in practice, and its high electric capacity is required to decrease its output electric impedance to match the electric load resistant. However, there are few reports to investigate the mechanical vibration damping ratio of PEH affected by the proof masses and output electric loads. In this study, the mechanical damping ratio (ζm) of PEHBC with zero proof mass, and the electric damping ratio (ζe) related to the electric load, the mechanical vibration damping ratio with proof mass and the electric load are measured and discussed for the piezoelectric bimorph cantilever energy harvesting (PEHBC). The damping ratio was calculated by the time dependence of tip displacement or velocity amplitude of PEHBC using a laser vibrometer. A theoretical analysis was carried out to correlate the damping behaviors of the cantilever to the proof mass and the electric resistive load. A good agreement is observed by the two sets of data.