Study on vibrational electric generator with impedance control

Abstract

This paper presents theoretical analysis and design method of a linear vibrational electric generator that converts kinetic energy of vibration into electricity. The generator is intended for applications such as supplying electricity to sensors or small information devices that must function without batteries for a long period of time. The generator is modeled as a one-degree-of-freedom vibration system. It is shown that the maximum output is attained when the generator is vibrating at its resonant frequency and at its mechanically movable maximum amplitude. The vibration amplitude is controlled by changing the electro-mechanical damping of the vibration system. The experimental system consists of three stationary generator coils and a moving permanent magnet unit suspended by leaf springs. A micro controller monitors the generator output and changes the connection of the generator coils to adjust the electro-mechanical damping to maximize the generator output. This system generated power of 100mW with 29% efficiency when external vibration of 6Hz with 5mm(p-p) amplitude was applied.