FREQUENCY-UP CONVERSION MECHANISM FOR VIBRATIONAL ENERGY HARVESTING IN LOW-SPEED ROTARY STRUCTURES � A COMPARISON STUDY

Abstract

This theses developed mathematical models of three concepts of frequency up converters that convert low-speed mechanical rotation (simulating a wind turbine) into high-frequency vibration of a piezoelectric cantilever beam using a magnetic force. The first two concepts utilize the swing motion of a small disk to stimulate vibration on a piezoelectric beam by a magnetic repelling force. The third concept, on the other hand, utilizes a swinging pendulum instead of the disk. A system of governing equations was developed to describe the motion of the disk/pendulum, vibration of the beam, and voltage output of the harvesters. These equations were solved using the ODE45 function in MATLAB software. Design optimization was performed for each concept to improve their power generation performance. It was found that the pendulum harvester (the third concept) outperforms the disk harvesters � the power density is increased by 2 to 3 times. The simulation results of the pendulum harvester were verified experimentally.