Development and experimental tuning of a model of a hybrid harvester for light vehicles

A hybrid piezoelectric harvester suited to light vehicles is presented. It is able to harvest energy both from base vibrations caused by the motion on uneven roads and from the airflow impinging on the vehicle. The proposed harvester is a cantilever equipped with a piezoelectric patch and a cylinder. The piezoelectric patch exploits bending vibrations. The cylindrical bluff body is used both to lower the natural frequency of the harvester and to generate vortex induced vibrations (VIV). The natural frequency of the harvester is set equal to the vortex shedding frequency at the typical cruising speed of the vehicle to exploit the lock-in phenomenon. A multiphysics model is presented, it includes the harvester dynamics, piezoelectric effects and a non-linear van der Pol wake oscillator, representing vortex shedding from the cylinder. The model is tuned by means of specific experimental tests. Piezoelectric constants are found by means of impulsive tests, whereas aerodynamic parameters are found by means of wind tunnel tests. The validated model is used to predict harvester behavior in different operational scenarios of the vehicle (constant and variable cruising speed). Numerical results show a synergic effect of road excitation and airflow excitation, and highlight the potentialities of the proposed harvester in the field of light vehicles.