Effects of mechanical coupling on oscillator frequency in a micromechanical accelerometer

Abstract

This thesis presents an analysis of the effect of mechanical coupling on the frequency behavior of the two oscillators in the SOA-3 micromechanical accelerometer. It also investigates the possible effect of the input acceleration on the degree of this mechanical coupling. A sensitivity study is also done to assess the dependence of the degree of mechanical coupling on the geometry of the beams that form the proof mass support system. By doing a modal analysis using both a Finite Element and a mass-spring model of the accelerometer, it is shown that mechanical coupling does exist between the two oscillators, and is a function of the input acceleration on the device. It is also shown that the effects of mechanical coupling on the frequencies of the oscillators are the greatest at the input acceleration where the oscillator's frequencies, if completely uncoupled, would approach the same value. Finally, several design changes are suggested that reduce the amount of mechanical coupling between the oscillators.