Equivalent circuit modeling and analysis of mems accelerometer and microvibrating structures

Abstract

The present study focuses on equivalent circuit modeling of MEMS based structures such as microcantilever, microbridge and bimetallic strip. MEMS cantilever is an important component, since it forms a basic unit for all devices or systems. The Single Degree of Freedom model (SDOF) (mass, spring and damper) has been represented as a parallel resonator (capacitance, inductance and resistance) using force-current analogy. Capacitive micro machined accelerometers offer several beneand#1048767;ts when compared to other accelerometers along with good response and noise performance. It also has high sensitivity, low power dissipation and low drift. Timo Veijola s model of MEMS capacitive accelerometer with squeezed film damping effect at the temperature of 300K has been employed for the study. An improved linear model incorporating temperature, pressure and squeezed film effects is developed. The circuit model corresponds to a vibrating system, including dominant micro physical mechanisms. Analysis is carried out at temperature and pressure ranges of 100K to 400K and 30 to 3000Pa respectively. The parameters of the accelerometer such as resonance frequency, peak displacement and settling time are determined. The inclusion of squeezed film damping with the system model reduces oscillation and the vibration reaches the steady state in a short time. The mechanical system of the MEMS is implemented as an analogous electrical system and is analysed under different temperatures. Thermal effect leads to variation in length, spring constant, viscosity and damping coefficient of the MEMS cantilever. A temperature controlled nonlinear dynamical circuit has been developed and squeeze film damping effect is also employed newline