A combined nonlinearity mechanism for potential well shaping of MEMS bi-stable energy harvester

Abstract

This paper presents a combined nonlinearity mechanism for the enhanced capability in shaping double well potential energy of MEMS bi-stable energy harvester, which is critical for both wideband inter-well oscillation and high power output. In comparison with conventional magnetic-induced bi-stable energy harvester adopting linear mechanical support, mechanical nonlinearity is incorporated and cooperates with magnetic nonlinearity for effective potential well tuning. With specific control of this mechanical nonlinearity, system linear and nonlinear stiffness could be proportionally adjusted for the independent control of well-gap separating adjacent potential well. Moreover, higher restoring force governed by mechanical nonlinearity could be achieved for the counteraction of magnetic force within smaller deformation, bringing the effective narrowing of well-gap. Therefore, with the incorporation of mechanical nonlinearity, the well-gap could be independently adjusted within much wider range, while maintaining the corresponding barrier depth constant, which could contribute to the significant bandwidth extension of inter-well oscillation. The analysis result shows that at frequency-sweep excitation with acceleration of 1 g, the prototype with well-gap of 1.4 mm and barrier depth of 6 μJ achieves normalized power density of 36 mW cm−3 g−2 and wideband inter-well oscillation of 77 Hz, covering 85.6% of frequency range from 10 to 100 Hz. The test under random excitation confirms the role of the proposed mechanism in inducing effective potential well shaping for comprehensive performance enhancement of bi-stable energy harvester, and could be further applied to the recently proposed high-energy orbit sustaining strategy to achieve ultra-wide unique inter-well motion.