Effect of single-side stroke limiter on cantilever-based piezoelectric energy harvesting from low frequency vibrations

Piezoelectric transducers which rely on oscillating cantilever-type beams to harvest mechanical energy locally available in environments have been of great interest as a substitute for batteries. Most of the research efforts focus mostly on designs which aim at resonance matching to achieve maximum energy output without taking the mechanical degradation of the piezoelectric layers into consideration. The purpose of this study is to propose an energy harvesting design which maximizes power output on the long run. Unimorph cantilevers, in which the neutral axis is located at the interface between the soft lead zirconium titanate (PZT) (PZT5A4) layer and the inert substrate (Pernifer 45), are used. An analytical model is developed to quantify the performance of the harvesters as a function of free length and tip mass. An experiment is set up to validate the theoretical model. To reduce the occurrence of cracks induced in the piezoelectric element due to the cyclic nature of the vibrational excitation, a housing acting as mechanical stroke limiter is adopted. The effect of the single-side stroke limiter on the power output and lifetime of the cantilevers is investigated. A 40 mm free length unimorph cantilever with 300 mg mass attached on the tip exhibiting an 18% increase in power output (0.1 mW) is proposed. An improved lifespan of the cantilevers is obtained by limiting the tensile deformation of the piezoelectric layer. This study opens the opportunity for more effective energy harvesting mainly through compressive operation for longer periods.