Experimental and theoretical investigations on piezoelectric-based energy harvesting from bridge vibrations under travelling vehicles

This paper aims to investigate the amount of energy which can be harvested by a cantilever beam type piezoelectric energy harvester from a bridge vibration. The sources of vibration are vehicles traversing the bridge. Two types of masses are considered as models for traversing vehicles: concentrated and distributed masses. The mass of the harvester is assumed negligible compared to that of the bridge. First, the problem of moving mass travelling with a constant speed over a beam is considered. The formulations for both concentrated and distributed masses are presented. The obtained results are then compared to the data available in the literature, in order to validate the model of a beam with a moving mass. Next, a mathematical model for the harvester is proposed, which is composed of an Euler-Bernoulli beam as a substrate, a tip mass, and a single piezoelectric patch whose electrodes are connected to a changeable resistance. To validate the model, the harvester is fabricated and tested on a shaker. The electroelastic frequency response functions of the system are measured by low-amplitude chirp excitation tests. The optimal resistive load at the resonance frequency, obtained from theory and experiments, are compared. Finally, the acceleration time histories for the beam at mid-span, where the harvester is located, are calculated for two mass types and used as base excitation signals to the harvester. These signals are replayed on an electromagnetic shaker to simulate the bridge vibrations on the fabricated harvester and the experimental results are compared with theoretical ones. Good agreement is observed.