Abstract

Human beings are becoming more and more dependent on electronic devices, such as smart phones, smart watches, GPS, etc. This paper presents the design, modeling and testing of a novel suspended energy harvesting backpack using half-wave mechanical rectification. The proposed half-wave rectification mechanism can convert bidirectional linear vibration into unidirectional rotation with nonlinear inertia. Compared with full-wave mechanical rectification, the proposed half-wave rectification is designed only to convert the motion in one of the vibration directions while remaining idle in the other direction. Numerical simulation shows the proposed half-wave rectification based suspended energy harvesting backpack can obtain about two times of the average output power as the previous full-wave rectification design while also maintaining larger output power in the wideband frequency range. Bench test results indicate that the proposed half-wave rectification-based energy harvesting backpack can harvest 6.7 W (peak)/2.1 W (average) under 2 Hz and 6 mm excitation with a 31.8 kg payload, which is a significant improvement compared with 1.9 W(peak)/0.9 W (average) for the counterpart of full-wave rectification system. In addition, bench test results also validate the energy harvesting in wideband frequency range. Treadmill tests demonstrate an average power range of 1.2–11.0 W under walking speeds of 3.2–6.4 km/h with a 13.6 kg payload.

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