Non-Contact Multiple Plucking Method for Frequency up Conversion Piezoelectric Energy Harvesters in Extremely Low Frequency Applications

Non-contact multiple plucking method is presented for frequency up conversion piezoelectric cantilever to increase output power in extremely low frequency range. Unlike the traditional method of decreasing device natural frequency to match external vibrations, the cantilever's high frequency self-oscillation is combined with the proposed multiple plucking method, i.e. to pluck cantilever multiple times in one cycle. Moreover, the plucking is non-contact via magnetic force, which further simplifies device structure and reduces energy loss. A prototype is assembled by using 2 pairs of magnets, and 4 times of plucking per cycle are achieved. Optimal device parameters such as magnet spacing, height, and gap are measured and discussed. Maximal peak output power of 1.2μW is obtained on 1.5MΩ resistance @ 0.1Hz. The proposed method is also utilized in a "wave & generate" setup, proving its potential in the non-contact power generation applications.