Modeling and analysis of dual modules cantilever-based electrostatic energy harvester with stoppers

Abstract

Based on the cantilever beam, this paper proposes and designs a novel electret-based electrostatic energy harvester (e-EEH) with dual modules: module I is a capacitor of nonparallel plate electrodes; module II is a multi-electrode array capacitor. Two stoppers are presented in concern with reliability by limiting the motion of proof mass to prevent capacitor breakdown and pull-in. Meanwhile the stoppers serve as a functional element to realize broadband harvesting. Considering the bending of the cantilever beam, the expression of the module Ⅰ capacitance is analytically derived as a function of the deflection. Conformal transformation is applied to obtain the expression of the module Ⅱ capacitance, simultaneously considering the change of distance and overlap area between movable and fixed electrodes. According to Hamilton's principle and Kirchhoff's circuit law, the electromechanical coupling nonlinear dynamics equations of the proposed energy harvesters are established. The output performance of the energy harvester is obtained and analyzed by numerical calculation. The results show that the double-model electrostatic energy harvester can output high power in low- frequency broadband.