Bifurcation Analysis and Nonlinear Dynamics of a Capacitive Energy Harvester in the Vicinity of the Primary and Secondary Resonances

Abstract

The impetus of the present study is to examine the effect of nonlinearity on the efficiency enhancement of a capacitive energy harvester. The model consists of a cantilever microbeam underneath which there is an electret layer with a surface voltage, which is responsible for the driving energy. The packaged device is exposed to unwanted harmonic mechanical excitation. The microbeam undergoes mechanical vibration and accordingly the energy is harvested throughout the output circuit. The dynamic formulation accounts for nonlinear curvature, inertia, and nonlinear electrostatic force. The efficiency of the device in the vicinity of the primary and super-harmonic resonances is examined and accordingly the output power is evaluated. Bifurcation analysis is carried out on the dynamics of the system by detecting the bifurcations in the frequency domain and diagnosing their types. One of the challenging issues in the design and analysis of energy harvesting devices is to broaden the bandwidth so that more frequencies are accommodated within the amplification region. In this study the effect of the nonlinearity on the bandwidth broadening, as well as efficiency improvement of the device, is studied.