Design, fabrication, and modeling of a four-bar electromagnetic vibration power generator

In this article, we report an electromagnetic vibration energy harvesting structure with efficiency approaching close to the theoretical limit. The structure was modeled to account for geometrical variation in magnetic field, velocity field, and the conductor orientation with respect to magnetic field patterns. A four-bar magnet geometry was selected, which allows for an easily manufactured device with high amount of electrical damping on the structure, and thus a close to optimal amount of power generated. Using standard modeling approaches in the literature for electromagnetic harvesters, it can be found that for this particular geometry, the prediction of the power output as a function of load resistance yields inaccurate results and overpredicts the optimal load resistance for the device. We present a comprehensive modeling approach for this geometry incorporating all the design variables, which contribute to a more accurate estimate of the power output as a function of load resistance. The model was validated against the fabricated prototype and consistent results were obtained.