Abstract
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.
Highlights
The architecture of a compliant mechanism is often obtained by the union of different instances of a same simpler structure rotated and translated in space
We considered a coupled analysis in order to exploit the computed pressure fields by the fluid-dynamical analysis as input data for the structural simulation
RESULTS we present results related to the elastodynamic analysis, we discuss the effect of the microchannels pressure on damping for the dynamic system
Summary
The architecture of a compliant mechanism is often obtained by the union of different instances of a same simpler structure rotated and translated in space. In recent years this class of mechanisms spread in industry because of its ease in manufacturing and assembling. Flexure mechanisms are one of the main outcome of this fast diffusion. Their architecture is often monolithic and composed of repeated modules arranged in series or parallel. Flexure mechanisms are not an assembly of different bodies coupled by means of joints, but they are fabricated as a monolithic structure not affected by backlash or friction [2]. Low hysteresis and zero maintenance, due to the absence of wear, make flexure mechanisms well-suited for: M.E.M.S., N.E.M.S., piezoelectric actuators, sensors, positioning and motion systems and many others applications requiring miniaturized systems
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