Energy conversion by ‘T-shaped’ cantilever type electromagnetic vibration based micro power generator from low frequency vibration sources

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The design, development, and analyses of low-frequency vibration based T-shaped cantilever type electromagnetic micro power generators (EVMPGs) are presented in this paper. Four different configurations (Configurations A to D) of EVMPGs were designed and fabricated and subsequently characterized using detailed experimental and limited analytical techniques. Configuration A and B consisted of a single and a double cylindrical moving magnets (NdFeB), respectively, while Configuration C consisted of four rectangular moving magnets with respect to a fixed copper coil. In contrast, Configuration D used a moving coil between four rectangular magnets with a back-iron bar. The open circuit RMS voltage output was observed to be a maximum from Configuration D (98.2mV at 6.29Hz) with a base vibration acceleration of 0.8ms−2. Therefore, Configuration D was selected for further experimental investigations, which included changing the back-iron bar thickness, changing the base acceleration level, and changing the air gap separation between the magnets in order to optimize this configuration. The maximum load RMS voltage and power outputs of Configuration D were 105.4mV and 1.35mW at 6.29Hz for load resistance 8.2Ω and a base acceleration of 0.8ms−2 with a 4.2mm back-iron bar when the air gap between the magnets was 20mm. Finally, a small portable EVMPG prototype was developed based on the Configuration D and was tested at different human movement conditions (i.e., walking, quick walking, and running). The developed EVMPG prototype was capable of harvesting 35.2mV and 0.22mW at 7Hz with load resistance 5.6Ω for a base acceleration of 0.8ms−2.