Implementation of Dual-Nonlinearity Mechanism for Bandwidth Extension of MEMS Multi-Modal Energy Harvester

Abstract

This paper presents a planar architecture implementing dual-nonlinearity mechanism for broadening bandwidth of a two-degree-of-freedom MEMS energy harvester. The proposed device consists of an electromagnetic-based inner resonator for power generation, and an outer resonator for accessory frequency tuning. In comparison with conventional 2DOF configuration, different high-order nonlinearity is subjected to the first two resonances by nonlinear springs incorporated into the inner and outer resonator, respectively, achieving double hardening responses with increased bandwidth at elevated excitation. Moreover, independent tuning of the resonant frequency and working bandwidth of both resonances could be achieved through concordant control of inner and outer nonlinear resonator, and with further adjust of mass and frequency ratio, the low-efficiency power generation range separating adjacent resonances could be effectively reduced. It's numerically shown that with proper nonlinearity at both oscillation stages, the approximate convergence of two nonlinear resonances with broadband and narrow low-efficiency range could be achieved following the mass ratio of μ <; 0.07 and linear frequency ratio of 0.7 <; α <; 1 between inner and outer stage. At acceleration of 1 g, test result further confirms that under dual-nonlinearity with nonlinearity ratio of 0.5, a continuous energy harvesting spectrum covering two nonlinear responses is realized with mass ratio of 0.02 and frequency ratio of 1, showing 3-dB bandwidth of 65 Hz. Power output of 127.7 μW and normalized power density of 1064 μWcm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> g <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> are achieved with the optimum load resistance of 37.5 Ω. This mechanism could be further applied to multi-DOF VEH for ultra-wide bandwidth of energy harvesting. [2020-0231]