Papers by Keyword: Pull-In

Abstract: Electrostatic micro-devices are simple but important for MEMS applications. Precise dynamic descriptions of these devices are often hard to obtain due to the electrostatic nonlinearity and the fluid-structure interactions in devices. Here we present a comprehensive electrostatic-mechanical-fluidic coupling transient analysis for the pull-in process of two ends fixed micro-plate device. The numerical results are compared with the published experiment works of other researchers available in the literature, and thus the model had been validated. After that the proper orthogonal decomposition approach is performed for the snapshot matrixes which are sampled from an ensemble of the fully finite element results. The resulted spatial distribution modes of pressure show a higher spatial frequency toward the middle of the micro-plate, which indicates that the pressures at the moving edges of the plate are not equal to ambient pressure. Due to the increasing demands for simulation accuracy, the electrostatic-mechanical interactions and the nonlinear features of viscous loss from the surrounding fluid have to be taken into account in details.

Abstract: This paper presents an analytical model based on the basis finite element analysis to solve the nonlinear behavior of double-cantilever structure. The structure beam is replaced with a series of beam elements by traditional finite element method. The deformation curve of the beam is calculated by gradually loading voltage in small increments, and pull-in behavior is identified when the convergence of the deflection iteration cannot be achieved after voltage increment. This method considers the effect of deformation on stiffness by establishing a new equivalent stiffness matrix for each voltage step on the basis of the results of previous steps. Through this approach, we prevent the approximate errors of the stiffness matrix from accumulating. The analytical results show good agreement with those obtained by using multiphysics coupling software.

Abstract: For the deformation problem of electrostatically actuated clamped-clamped micro-beams, pull-in behaviors of the micro-beams have been analyzed by using Rayleigh-Ritz method. Approximate analytical expressions for pull-in voltage and normalized pull-in displacement of the micro-beam have been obtained. When the pull-in occurs, the pull-in voltage and normalized pull-in displacement of the micro-beam at the mid-span position are 38.6V and 0.398, respectively. The results show that the approximate analytical solution possesses high accuracy.

Abstract: For the deformation problem of an electrostatically actuated cantilever micro-beam, size effect on pull-in behaviors of the micro-beams have been studied based on modified couple stress theory. The approximate analytical solutions to the pull-in voltage and pull-in displacement of the micro-beam are derived by using the Rayleigh-Ritz method. The results show that the normalized pull-in voltage of the cantilever micro-beam is size-dependent and the normalized pull-in displacement of the micro-beam is size independence.

Abstract: Three main obstacles in modeling electrostatic torsional micromirror are hard to calculate – damping coefficient, mechanical spring constant and electrostatic torsion accurately. Because that parameter variations and model uncertainty of the torsional micromirror resulting from fabrication imperfections are inevitable, it is another problem to seek a control scheme for achieving accurate positioning and trajectory tracking of an electrostatic torsional micromirror. In this paper, aimed at a real prototype of circular electrostatic torsional micromirrorr, both static and dynamic behaviors are modeled and studied. A novel nonlinear Proportional, Integral and Derivative (PID) control are proposed in succession. Simulation results show that the system model derived is more accurate to the micromirror and the nonlinear PID can eliminate the static deviation.

Abstract: Parallel-plate capacitor whose plates both fixed to elastic supports is presented and analyzed in this paper, and its cantilevers model is analyzed to study the parameter dependence of pull-in voltage. The whole process of voltage calculation is based on material mechanics theories and analytical methods, and the results are verified by simulation of MEMS software, which is mainly aiming at the effects of plate dimensions on pull-in voltage. It is concluded that the longer are the supporting beams, the smaller are the effects of plate’s parameters on voltage, besides, the effect extent of longitudinal length of plate is little larger than that of transverse length.

Abstract: A modified continuum model of electro-statically actuated micro-beam is presented based on the modified couple stress theory. The new model contains a material length scale parameter and can capture the size effect, unlike the classical Bernoulli-Euler beam theory. The governing equation of the micro-beam is derived based on the Hamilton’s principle, which accounts for the effects of the moderately large deflection, the residual stress and the fringing electrostatic field. The numerical analysis of mechanical characterization is performed by the Analog Equation Method (AEM). The effects of the couple stress on the static and dynamic responses, pull-in voltage and pull-in time are discussed.

Abstract: Four types of MEMS actuators are presented in this paper. The effect of structure on three major performance parameters of these actuators, such as resonance frequency, pull in voltage and stroke, are studied by FEA and compared with each other. The result shows that, on the condition of the same spring length and the same spring width , O-shape actuator have the largest stroke and pull in voltage, but that of L-shape actuator is the smallest.

Abstract: Deformable focusing micromirror is one of the important optical MEMS devices. The focusing length is determined by the profile of the micromirror surface. For uniform deformation, based on bulk microfabrication of isotropic etching and wafer bonding, a novel micro electrostatic deformable focusing mirror actuated by hemispherical electrode is designed and analyzed. Due to the coupling between elastic and electrostatic force, numerical method of finite element using ANASYS software is used to analyze the deformations and stresses of different structure sizes. The phenomenon that structures deform abruptly fast due to nonlinear increasing electrostatic force called pull-in is also discussed. Using the least square method, the profile of micro focusing mirror can be curve fitting as a parabola. And the focal length can be obtained. The results show deformation increases nonlinearly as applying voltages increasing. The stresses increase linearly when thickness also increase but nonlinearly when radius of mirror increases. The maximum stress happens in the region of bounded. The focal length decreases quasi-linearly as applying voltage increases. The mirror sizes and gaps have effect on pull-in voltages. Larger gap and smaller mirror radius will cause larger pull-in voltage.