Abstract:
Micro Electromechanical Systems (MEMS) actuators experience pull-in instability in their actuation range. MEMS actuating elements are thin parallel plate capacitor electrodes separated with air gap. The electrodes are fabricated from silicon as substrate layer and gold /aluminum layer as functional layer for reflecting laser beam in optical switching application. When the top electrode is attracted towards bottom electrode, as it crosses one third distance of the gap between the electrodes, it undergoes pull-in/snap-down with bottom electrode. This condition severely limits the device operating range. These devices are operated either analog or digital mode for positioning of the top electrode. The plate electrodes actuated in tilting mode or bending mode and they are typically torsional structures or fixed-fixed structures. This paper provides theoretical pull-in analysis for the static behavior of a optical switch model. It is derived from analytical modeling of the parallel plate type with fixed-fixed structural end conditions. The effect of dielectric layer thickness is taken into account for predicting the pull-in voltage. During the piston mode actuation cycle, when the threshold (pull-in) voltage is reached, the switch is in the bent or ON state due to electrostatic repulsion/attraction and for the no voltage condition it is in the parallel or OFF state. The pull-in hysteresis behavior of the multilayered micro-actuator bending beam model is analyzed for the variation in thickness of dielectric material. In this paper, the critical role of different dielectric layer materials in bringing down the static pull-in voltage is discussed.

Abstract:
In this paper, we study the behaviour of a microcantilever beam under electrostatic actuation using finite difference method. This problem has a lot of applications in MEMS based devices like accelerometers, switches and others. In this paper, we formulated the problem of a cantilever beam with proof mass at its end and carried out the finite difference solution. we studied the effects of length, width, and the gap size on the pull-in voltage using data that are available in the literature. Also, the stability limit is compared with the single degree of freedom commonly used in the earlier literature as an approximation to calculate the pull-in voltage.

Abstract:
The soft switched PWM ZVS full bridge DC to DC converter and push-pull type LLC series resonant converter are compared for use in low output voltage power supply applications. It is shown that push-pull type LLC series resonant converter takes on the desirable characteristics of the conventional push-pull converter and LLC series resonant converter. Push-pull type has less conduction loss than that of full bridge converter. Analyses and simulation shows that for low power applications required turn ratio of the transformer is less so efficiency is more and switching stress is less for push-pull LLC series resonant converter than PWM ZVS full bridge DC to DC converter. The 48V DC is efficiently reduced to 12V DC using both DC to DC converters using 20KHZ switching frequency and all parameters are compared.

Abstract:
The influence of the Casimir excitation on dynamic pull-in instability of a nanoelectromechanical beam under ramp-input voltage is studied. The ramp-input actuation has applications in frequency sweeping of RF-N/MEMS. The presented model is nonlinear due to the inherent nonlinearity of electrostatics and the Casimir excitations as well as the geometric nonlinearity of midplane stretching. A Galerkin based reduced order modeling is utilized. It is found that the calculated dynamic pull-in ramp input voltage leads to dynamic pull-in step input voltage by increasing the slope of voltage-time diagram. This fact is utilized to verify the results of present study. 1. Introduction Nano/microelectromechanical systems (N/MEMS) are mostly used as sensors and actuators. Because of their small size, low power consumption, and the reliability of batch fabrications, there are lots of potential applications in engineering. Clamped-clamped microbeams represent major structural components and play crucial roles in these systems. One of the most important phenomena associated with electrostatically actuated N/MEMS is pull-in instability which occurs when input voltage exceeds its critical value. In this manner, the movable part is suddenly collapsed toward the substrate. This phenomenon was observed experimentally by many researchers. Nathanson et al. [1] and Taylor [2] have investigated this phenomenon experimentally. This instability can occur in both static and dynamic circumstances. If the rate of applied voltage is negligible, the static pull-in instability may be observed; otherwise, one can observe DC dynamic pull-in. At the nanoscale, the intermolecular forces significantly influence dynamics of nanobeams. The Casimir effect is the most important force at the scale of N/MEMS. It represents attractive force between two flat parallel plates of solids that arises from quantum fluctuations in the ground state of the electromagnetic field [3]. The Casimir interaction becomes operative at separations less than several micrometers and above 20？nm [4]. The influence of Casimir force on the pull-in instability of nano- and microsystems has been investigated by many researchers. Lin and Zhao [5] studied the influence of the Casimir force on static pull-in behaviour of nanoelectromechanical systems using lumped model. Ramezani et al. [6] proposed a distributed parameter model to study the static pull-in instability of nanocantilevers subjected to intermolecular and electrostatic forces. They transferred nonlinear differential equation of the model into the integral form by

Abstract:
A pendulum powered by high voltage electricity is described. The pendulum consists of two conducting plates(thin foil) separated by copper rods and are insulated from each other. High voltage is applied to these plates through the connecting copper rods. Another stationary aluminum plate(thin foil) is placed in front of the pendulum such that it serves to attract the pendulum plates and makes electrical contact with them enabling charge transfer between the stationary plate and the pendulum plates. The pendulum is powered by the energy stored in the capacitance between the stationary aluminum plate and the pendulum plate. Attempt has been made to obtain the time period of oscillations as a function of applied voltage and other parameters. The derived formula for the time period has been verified experimentally. This apparatus can be used to demonstrate electrical phenomena in general and in particular electrical energy stored in conductors of small dimensions.

Abstract:
Electrostatic actuators are simple but important switching devices for MEMS applications. Due to the difficulties associated with the electrostatic nonlinearity, precise mathematical description is often hard to obtain for the dynamics of these actuators. Here we present two sharp theorems concerning the dynamics of an undamped electrostatic actuator with one-degree of freedom, subject to linear and nonlinear elastic forces, respectively. We prove that both situations are characterized by the onset of one-stagnation-point periodic response below a well-defined pull-in voltage and a finite-time touch-down or collapse of the actuator above this pull-in voltage. In the linear-force situation, the stagnation level, pull-in voltage, and pull-in coordinate of the movable electrode may all be determined explicitly, following the recent work of Leus and Elata based on numerics. Furthermore, in the nonlinear-force situation, the stagnation level, pull-in voltage, and pull-in coordinate may be described completely in terms of the electrostatic and mechanical parameters of the model so that they approach those in the linear-force situation monotonically in the zero nonlinear-force limit.

Abstract:
Pull-in voltage Evaluation is significant for the design of electrostatically actuated MEMS devices. In this work simple closed form models are derived for computation of pull-in voltage of cantilever beams. These models are obtained based on five different capacitance models suitable for wide range of dimensions. Using these models pull-in voltages are computed for a range of dimensions and the results are compared with the experimentally verified 3D finite element analysis results. The results show that, for every given range of dimension, choice of the model changes for the evaluation of the pull-in voltage with a maximum deviation of 2%. Therefore for a given range of dimension appropriate closed form model is to be chosen for accurate computation of pull-in voltage. Computation of pull-in voltage of microgripper further validates the closed form models. The results again show that for a given range of dimension only a particular model evaluates the pull-in voltage with less error.

Abstract:
The pull-in voltage of RF MEMS switches at different actuations is presented.When the actuation voltage is a pulse voltage,the movement of the switch beam is in a vibration state rather than quasi-static,so the pull-in voltage is different from the quasi-static condition and is called dynamic pull-in voltage.It is about 92% of the quasi-static pull-in voltage.Following the simple formula of the spring coefficient of a beam and the exact formula of the capacitor for the switch,the quasi-static and dynamic pull-in voltages of the clamped-clamped beam switch on CPW are analyzed,and the damping effect is also included.The damping reduces the difference between the two kinds of pull-in voltages.Finally,the influence of the RF input power on the pull-in voltage is analyzed.The input power decreases the pull-in voltage,reducing the pull-in voltage to zero at a certain power,and then making the switch self-actuate.

Abstract:
This paper describes an electrostatic excited microcantilever sensor operating in static mode that is more sensitive than traditional microcantilevers. The proposed sensor comprises a simple microcantilever with electrostatic excitation ability and an optical or piezoresistive detector. Initially the microcantilever is excited by electrostatic force to near pull-in voltage. The nonlinear behavior of the microcantilever in near pull-in voltage i.e., the inverse-square relation between displacement and electrostatic force provides a novel method for force amplification. In this situation, any external load applied to the sensor will be amplified by electrostatic force leading to more displacement. We prove that the proposed microcantilever sensor can be 2 to 100 orders more sensitive compared with traditional microcantilevers sensors of the same dimensions. The results for surface stress and the free-end point force load are discussed.

Abstract:
Electrostatic-driven microelectromechanical systems devices, in most cases, consist of couplings of such energy domains as electromechanics, optical electricity, thermoelectricity, and electromagnetism. Their nonlinear working state makes their analysis complex and complicated. This article introduces the physical model of pull-in voltage, dynamic characteristic analysis, air damping effect, reliability, numerical modeling method, and application of electrostatic-driven MEMS devices.