Energy harvesting from ambient vibrations: Electromagnetic device and synchronous extraction circuit

This article presents the design and experimental test of a new electromagnetic generator optimized for vibration energy harvesting with a nonlinear energy extraction circuit (synchronized magnetic flux extraction circuit). Previous results showed that the synchronized magnetic flux extraction circuit allows the rectification and the amplification of the voltages produced by an electromagnetic transducer, as well as the optimization of the energy transfer independently of the load impedance. A new geometry of electromagnetic harvester is proposed and optimized to harvest the maximum energy with the synchronized magnetic flux extraction circuit. The studied structure, whose total volume is 10 cm³, is based on a closed ferromagnetic back iron in order to obtain a high reactance in comparison with its resistance. Experimental measurements show that with the synchronized magnetic flux extraction technique, a rectified power of 1.6 mW is harvested at 1 g, 100 Hz over a 10 Hz bandwidth.