Coupled fluid-dynamical and structural analysis of a mono-axial mems accelerometer

This study is aimed to numerically investigate the elastodynamics of a mono-axial MEMS accelerometer. The vibrating part of the device is dipped into a fluid micro-channel and made of a proof mass connected to the frame by two flexible legs. The adopted mathematical model lies on a linearized motion equations system, where the mass matrix is obtained by means of both lumped and distributed approach. The stiffness matrix is otherwise derived through FEA, in which the proof mass and the compliant legs are modeled as rigid and flexible bodies, respectively. The squeezed-film damping effect is evaluated by a fluid-dynamical FE model based on a modified Reynolds formulation. The ensuing analyses are carried-out for three pressure levels of the narrow gas film surrounding the device, by applying the logarithmic decrement method for evaluating the damping ratio. Numerical results, in terms of acceleration, frequency range and noise disturbance, are successfully compared to analytical and experimental ones previously published in literature. Our model characterizes the accelerometer dynamics in space, allowing, in addition, to assess translational motion errors along directions apart the working one