Numerical modeling of dynamic response of miniature multi-impact electromagnetic device for low and wide range frequencies energy harvesting

Abstract

In this study, numerical modeling of nonlinear dynamic responses of miniature electromagnetic energy harvesters is reported for multiple impacts using limited amplitude and low-frequency excitations (0.5-3 g, 10-40 Hz). When an external vibration source frequency approaches oscillators' resonate frequencies (15 Hz and 30 Hz), these oscillators strongly impact onto a stiffer cantilever resulting in a much higher frequency vibration (1 kHz) in accordance with a large frequency up-conversion factor similar to 33.3-66.6. The Lorentz force and the nonlinear oscillators together resulted in complicated nonlinear dynamic responses of the cantilever, such as period doubling, superharmonic, or chaotic. Furthermore, the instantaneous generated power of miniature electromagnetic harvester was dramatically enhanced with 3 mu W, and the enhancement came from the more the number of oscillators, the lesser the air damping, and appropriate frequencies from external vibration sources. Moreover, the free tip of the cantilever in the system with both of the cube nonlinear oscillators and the linear oscillators were carefully analyzed by the phase portraits to demonstrate its dynamic responses behavior.