A Novel Piezoelectric and Electromagnetic Energy Harvester as a High-Pass Filter With a Low Cutoff Frequency

Battery-less wireless sensor networks (BL-WSNs) are an interesting and sustainable solution for Internet-of-Things (IoT) applications. The sensor nodes in the BL-WSNs are often powered by an energy harvester. Generally, these harvesters provide intermittent energy to the BL-WSNs. Hence, to cater to a variety of applications, the energy harvesters should work as a high-pass filter, that is, provide continuous energy to the BLWSNs. This article proposes a novel design to harvest vibration energy using a coupled Dovetail-shaped piezoelectric and electromagnetic energy harvester (Dovetail-PEM-EH). Unlike earlier PEM-EH designs with either one or two vertical cantilevers, Dovetail-PEM-EH uses three bimorphs and one copper (fixed tip end) cantilever with magnets on the tips. Placing more than two cantilevers with tip magnets requires optimizing distances among cantilevers and selecting tip magnets in such a way that energy harvesting is increased and the design is stable, that is, cantilevers do not collide with each other. A low-complexity binary search-based algorithm is presented to achieve the same. By doing so, the magnetic attractive forces increase the vibration sensitivity of the proposed design, and it works as a high-pass mechanical filter with a low cutoff frequency. The detailed simulation analysis performed in COMSOL shows that there is a minimum $2\times $ increase in the voltage and six out of the nine tested models show more than $3\times $ improvement in the harvested power when compared to the state-of-the-art. The hardware implementation of one of the models validates the simulation results with a slight variation.