NUMERICAL ANALYSES ON THE RESPONSES OF UNIMORPH AND BIMORPH PIEZOELECTRIC HARVESTERS IN TIME DOMAIN

Abstract

The paper presents the assessment of the electric output rendered by a unimorph and a bimorph piezoelectric harvester, with one and two active piezoceramic wafers, using numerical simulations. Expected sinusoidal voltages were obtained in a time-dependent study, with a time step corresponding to the eigenfrequency found after conducting an Eigenfrequency study. The terminal voltages obtained agree with the Euler-Bernoulli beam theory and with the distance of the piezoelectric layers from the neutral fiber. By adding an electric circuit node to the electric field problem to form a closed internal circuit, a single unified sinusoidal voltage response should be obtained, coinciding with the input vibration signal. The independent voltages of the layers of a piezoelectric structure with more than one layer (usually two or four) cannot be observed experimentally, as a harvester has only two terminals that pick the overall electric response from all the layers, giving a single alternating voltage output.