Mahdieh Shojaei Baghini*
*Department of Mechanical, Maritime and Materials Engineering, Delft University of Technology, Delft, Netherlands
Abstract: This paper presents the design of a bulk Silicon MEMS single-axis 8-beam accelerometer utilizing meander beams in the Structural Mechanics and MEMS Module of COMSOL Multiphysics®. To obtain further insights into the design of the accelerometer, an electrical lumped element model of the structure is derived and represented in SPICE. Quantities such as eigenfrequencies and proofmass displacement have been extracted from COMSOL Multiphysics® as well as analytical studies. The effects of parasitic frequencies in the structure are observed by automatic tilting of the accelerometer at higher order eigenfrequencies due to finite off-axis stiffness coefficients. In order to mathematically quantify the response of the accelerometer arising due to parasitic frequencies, the transient damping response has been derived in COMSOL Multiphysics® as well as SPICE, and the differences are highlighted. Finally, the eigenfrequencies of the meanderbeam accelerometer have been compared with that of a simple-beam accelerometer and the validity of small deflection theory is tested for the lumped model approach. While the target damping factor of the accelerometer was 0.7, the obtained damping factor increased to 1.1 due to the aforementioned parasitic frequencies and reduction in the resonance frequency of the sensor. This effect was precisely captured during the COMSOL Multiphysics® simulation.
Fig: The designated sensor is damped using plates placed at a distance equal to h0; its a) electrical circuit equivalent of squeeze-film damped accelerometer; b) electrical circuit considering symmetric damping; c) simplified equivalent circuit for gap height derivation.
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