Design and analysis of a non-resonant rotational electromagnetic harvester with alternating magnet sequence

•The energy harvester is suitable for low-frequency kinetic movement.•Lagrange equation and numerical method are adopted.•The principle experiment and verification test are carried out. This paper proposed a portable non-resonant rotational electromagnetic vibration energy harvester using magnetic spring to scavenge kinetic energy from low-frequency human motion. Lagrange equations were established to study the dynamic characteristics of the harvester. MATLAB/Simulink was adopted to analyze the output performance at different excitation frequencies. A prototype has been fabricated for experiment, and the measured results are compared with the theoretical analysis. The energy harvester could respond to diverse vibration excitation. When external excitation frequency is 6 Hz, the output voltage and power density of the electromagnetic energy harvester are 2.2 V and 0.024 W·mm−3 respectively. Four LEDs are alight when external excitation frequency is 5 Hz. It is indicated that the electromagnetic energy harvester based on the magnet spring can efficiently harvest low frequency vibration energy at low frequencies. This work made a significant step toward energy harvesting from human motions. It has potential applications in self-powered portable electronics.