A wideband low frequency 3D printed electromagnetic energy harvester based on orthoplanar springs

Electromagnetic energy harvesters are commonly known for their high performances in terms of power output conversion, and they are suitable for low frequency environmental vibrations. This work reports the study, design, development and experimental validation of a new extremely compact, low frequency, electromagnetic energy harvester based on two stacked ortho-planar springs, which exploits a promising magnets disposition. The device is composed by two stacked ortho-planar springs connected externally by a rigid frame. The two internal moving parts are connected to each other by a central pivot where an array of magnets is fixed on in a peculiar disposition: a half has a magnetic field directed upward, while the other half directed downward. A copper coil is wound into a housing fixed on the external frame. It comes a central massive cursor that axially moves, exploiting the springs compliance, relatively to the external frame. The prototype was almost completely realized by using Filament Fused Fabrication (FFF) additive manufacturing process in Onyx material, carbon fibre reinforced nylon. In the experimental assessment an oscillating excitation was applied on the external frame in multiple linear sweep frequency tests with different amplitude signals. The experimental validation shows a large bandwidth, from 10 to 30 Hz, and consistent output voltage and power signals.