Enhanced Frequency Up-Conversion of Vibration Energy Harvesters via Modified Magnetic Forces

In this work, a technique to improve the magnetic frequency up-conversion (FuC) of piezoelectric energy harvesters at low velocities of interaction (0.4 m/s - 0.6 m/s) is proposed. The magnets used in the FuC are shielded with additional magnetic material and opposite polarization with the aim of making the force-distance curve between the magnetic blocks sharper. The concept is investigated both analytically and experimentally. A mesoscale energy harvester is then simulated at low-frequency (5 Hz). The results show that the proposed technique improves the impulsiveness of the magnetic interaction and a power gain of about 36x is obtained with an amplitude of velocity equal to 0.6 m/s.