Abstract
Traditional electromagnetic bistable energy harvesters (EM-FBEH) possess the fixed potential barrier characteristics, making inter-well motion difficult to achieve under weak excitation, which significantly reduces output power and narrows the effective bandwidth. To address this issue, an enhanced electromagnetic variable-barrier bistable energy harvester (EM-VBEH) is proposed in this study. First, the theoretical model of the EM-VBEH is established based on magnetic dipole theory and analytically derived. Then, the magnetic restoring force of the primary oscillator, the potential energy surface, and bifurcation characteristics of the system are numerically analyzed to investigate the influence of system parameters on the variable-barrier behavior. The dynamic evolution and complex nonlinear behaviors of the EM-VBEH under frequency sweep and amplitude sweep excitations are also examined. Compared to the EM-FBEH, the EM-VBEH is more readily excited into inter-well oscillation, resulting in larger vibration amplitudes and an approximately threefold increase in effective bandwidth. Furthermore, parameter optimization is performed for the EM-VBEH. Under an excitation level of 4.5 m/s2, the optimized EM-VBEH achieves an increase of approximately 1 Hz in effective bandwidth and an enhancement of about 100 mW in maximum output power. Finally, a prototype of the EM-VBEH is fabricated, and a series of experiments are conducted. The results demonstrate that both the output power and bandwidth of the EM-VBEH are improved by over 2.8 times compared to the EM-FBEH, with good agreement observed between experimental data and numerical simulations. The proposed EM-VBEH is thus verified as an efficient vibration energy harvesting device, capable of effectively and extensively collecting energy from low- and ultra-low-frequency ambient vibrations, providing a sustainable power source for low-power electronics.
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