A bistable electromagnetic energy harvester for low-frequency, low-amplitude excitation
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(2020) 42:520
TECHNICAL PAPER
A bistable electromagnetic energy harvester for low‑frequency, low‑amplitude excitation Mohammed Ali Abdelnaby1 · Mustafa Arafa2 Received: 31 December 2019 / Accepted: 1 September 2020 © The Brazilian Society of Mechanical Sciences and Engineering 2020
Abstract In this work, we propose a bistable vibration energy harvester that can be used for non-resonant low-frequency, low-amplitude excitation. The design exploits magnetic bistability created between a pair of repelling magnets. Unlike base-excited beams, our design relies on placing one magnet on the tip of a cantilever beam having a fixed base, while transversely moving an opposite magnet thereby displacing the beam across its two stable positions with an amplified motion to harvest greater amounts of power by electromagnetic induction. A theoretical model is developed to simulate the dynamic behavior of the system at different excitation frequencies, amplitudes and magnetic gaps in order to assess the effect of the design parameters on the performance. It was found that the proposed design is beneficial and outperforms conventional linear oscillators for a broad range of frequencies, except at the linear resonance frequency. The results are supported experimentally over a range of load resistance. Keywords Bistable · Energy harvesting · Low-frequency · Low-amplitude List of symbols A Excitation amplitude (mm) AR Amplification ratio B Magnetic flux density (T) b Beam width (m) [c] Damping matrix (Ns/m) {F} Total force vector (N) f Excitation frequency (Hz) Fm Bistable force (N) Fem Electromagnetic damping force (N) h Beam thickness (m) I Electric current (A) [k] Stiffness matrix (N/m) l Beam length (m) lc Coil inductance (H) lw Coil wire length (m) [m] Mass matrix (kg) Rc Coil resistance (Ω) Technical Editor: Pedro Manuel Calas Lopes Pacheco. * Mohammed Ali Abdelnaby [email protected] 1
Department of Production Engineering and Printing Technology, Akhbar Elyom Academy, Cairo, Egypt
Mechanical Engineering Department, American University in Cairo, Cairo, Egypt
2
Rl Load resistance (Ω) y External excitation (m) [z] Nodal degrees of freedom β Proportional damping coefficient ω Excitation frequency (rad/s) δ Gap between magnets (m)
1 Introduction Vibration-based energy harvesting has been recognized as an enabling technology for self-powered devices owing to its perennial existence in natural sources and engineering equipment [1–4]. One promising application is powering wireless sensor nodes in structural health monitoring applications [5–8]. Different harvester designs have been presented in the literature to convert vibrational energy to useful electrical power through the use of electromagnetic and piezoelectric materials [1–4]. Many studies rely on cantilever configurations with a proof mass because of the ease of manufacturing and the ability to tailor the resonant frequency [9, 10]. However, deviations from operating at resonance lead to significant reduction in the output pow
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