Design of Piezoelectric Energy Harvesting System by Magnetic Force-Controlled Resonance Frequency

We designed a piezoelectric energy harvesting system that can be controlled the resonance frequency to the frequency of external energy. A permanent magnet (10 mm × 10 mm × 5 mm) was affixed to the free end of cantilever, and a permanent magnet was affixed to each of the four faces of a rotor at 90° angles. The effect of the dimension of the permanent magnets (20 mm × 20 mm × 10 mm, 30 mm × 20 mm × 10 mm, and 40 mm × 20 mm × 10 mm) and the effect of the pole array (NNNN, SSSS, NSNS, and NNSS) were experimentally tested. The optimum conditions were selected by testing varied distances between the magnets at varied rpm. The experiments demonstrated that the maximum output voltage was generated for the largest magnet and the minimum distance. The most effective way to control the resonance frequency was to modify the pole arrays of magnets affixed to the rotor. Furthermore, the optimum conditions were determined at each distance by changing the pole array and rpm. Simulation software supports the experimental results