Abstract
Harvesting kinetic energy from environment is particularly suitable to replace the traditional electro-chemical type batteries as a power source of low-power electronics, such as pressure sensors and thermometers. Tire pressure monitoring system (TPMS) is a key device in preventing a flat tire, which is one of the most frequent causes of car accidents. In U.S.A., European Union and a number of Asian countries are currently considering the implementation of TPMS-related legislation. The existing TPMS are powered by a battery, but there are drawbacks to these batteries, such as their limited durability and pollution of the environment. For this reason, this thesis is aimed at developing a power generator for TPMS This study designed a weighted pendulum to harvest energy from a rotating wheel, which consisted of a pendulum and one or more weights. As an energy harvester applied in TPMS, a normal pendulum cannot oscillate with a large angle at any wheel speed. In this study, the well-weighted pendulum helped the pendulum to adjust its natural frequency to meet the wheel rotation frequency. Therefore, the well-weighted pendulum is able to oscillate at various wheel speeds with a large angle and angular velocity. The kinetic energy produced was converted into electrical energy by electromagnetic induction, and a numerical study revealed that the well-weighted pendulum generated power of hundreds micro-Watts. The numerical results obtained from the analytical model of the well-weighted pendulum were in good agreement with the experimental results in both the swing angle and the power generation. The models of power generation were derived by using Faraday's law of induction and Lorentz force law, which were followed by the numerical solutions performed to verify the correctness with experiments. Moreover, for enhancing the electromagnetic efficiency, a novel circular Halbach array disk has been presented to lighten 40 % of the coil layers in the power generation compared with the normal multipolar disk. To investigate the dynamic behavior and power generation of the weighted pendulum, a car wheel emulator was constructed. At an optimum external resistance, the power output of the well-weighted pendulum was approximately 300 to 550 micro-Watts at about 200 to 500 rpm. This performance demonstrated that this has the potential to replace the battery in TPMS.