Abstract
In this thesis the feasibility of a micromechanical device for generating electrical energy from mechanical vibrations is explored. And this thesis is a study of microgenerator based upon the Lentz theory, which makes use of the magnet’s position changes to relative to the fixed flux collecting coils. Magnet position changes is provided by a thin polyimide membrane driver by external vibration. Simulation tools are used to analyze the spatial variations of magnetic field and to calculate the changes of the magnetic flux as a function of position and time, while the stress analysis can help the design of appropriate suspended membrane to make the best geometric design parameters for fabrication. Thick photoresist, electroplating, and bulk micromachining techniques were employed the fabrication the device. For a 1 x 1 cm2 membrane and 3.6 x 3.6 x 1 mm3 magnet, the maximum generate voltage is about 8.64 mV under external vibration at resonant frequency of 370 Hz. For a 2 x 2 cm2 membrane and 3.6 x 3.6 x 1 mm3 magnet, the maximum generate voltage is about 14.78 mV under external vibration at resonant frequency of 330 Hz. 1μw power generation is achievable for a 50Ω load. The main limitation on the power output of the generator is its size. Size limits the magnitude of the seismic magnet, and the maximum distance that the magnet can travel. The larger these can be made, the greater the electrical power that the generator will produce. The design rules for optimizing a generator to produce maximum power for a particular application are : The magnet should be as larger as possible within the available volume of the device. The extent that the magnet can move should be as large as possible in the space available. The spring should be designed so that the resonance frequency of the device matches the vibration frequency of the application. In future, potential applications for the generator may also include mobile phone and heart-pacers where human motions can be used as a source of mechanical energy.