A MEMS Tunable Capacitor With Dual Deformation Modes and High Tunability and Linearity

2021 ◽  
Author(s):  
Mahdi Shahi ◽  
Mohammad Shavezipur
Keyword(s):  
Parallel Plate ◽  
Actuation Voltage ◽  
Rf Circuits ◽  
Structural Instability ◽  
Design Parameters ◽  
Tunable Capacitor ◽  
Tunable Capacitors ◽  
High Tunability ◽  
Highly Nonlinear ◽  
Rigid Body Displacement

Abstract MEMS tunable capacitors have applications in tunable filters and RF circuits where high tunability and Q-factor are desired. Conventional parallel-plate tunable capacitors have a highly nonlinear capacitance-voltage (C-V) response and limited tunability of up to 50% due to fundamental limitation and structural instability. In this work, we present a novel design idea for a parallel-plate tunable capacitor that increases the tuning ratio and provides a smoother (more linear) response. The design uses two modes of deformation, rigid-body displacement of a curved moving electrode before pull-in and deforming the plate after pull-in, and exploits nonlinear structural stiffness to improve the linearity (and the tunability) of the tunable parallel-plate capacitor. The capacitor structure is designed such that when actuation voltage is applied, first the beams holding the moving electrode deform, and capacitance increase similar to conventional design up to pull-in. After the pull-in, the top electrode (which has a curved geometry) is deformed and further increases the capacitance, as the voltage increases. The design may provide an overall simulated tunability of more than 380%, and also has a more linear C-V response. The design is modeled and simulated using ANSYS coupled-field multiphysics solver and the effect of different design parameters are investigated. The simulation results show much high tunability and better linearity than conventional parallel-plate capacitors.

A Novel Highly Tunable Butterfly-Type MEMS Capacitor

2007 ◽  
Author(s):  
Mohammad Shavezipur ◽  
Amir Khajepour ◽  
Seyed Mohammad Hashemi
Keyword(s):  
Electrostatic Force ◽  
Actuation Voltage ◽  
Tunable Capacitor ◽  
Tunable Capacitors ◽  
High Tunability ◽  
Structural Rigidity ◽  
Highly Sensitive ◽  
Capacitance Voltage ◽  
Nodal Displacements ◽  
Q Factors

MEMS parallel-plate tunable capacitors are widely used in different devices such as tunable filters and resonators because of their simple structures, high Q-factors and small sizes. However, these capacitors have low tuning range with nonlinear and highly sensitive capacitance-voltage (C-V) responses. In this paper the development of novel tunable capacitor designs exhibiting highly linear C-V responses, is presented. The designs use segmentation technique to produce lumped flexibility in capacitor’s structure. A numerical model is developed to simulate the behavior of the capacitor. When a actuation voltage is applied, the structural rigidity of the plate produces resistive force which balances the electrostatic force, causes nodal displacements and changes the capacitance. It is shown that by optimizing the shape of segments (from rectangular to trapezoidal) and adding flexible steps located under the segments, a low sensitive linear C-V response could be achieved, while maintaining high tunability. The results of numerical simulation for the capacitors designed for PolyMUMPs process demonstrate that by optimization of the segments shape and structural stiffness a combination of high tunability over 100% and highly linear C-V response is achievable.

Sensitivity Analysis in Yield Optimization of MEMS Tunable Capacitors

2006 ◽  
Author(s):  
Mohammad Shavezipur ◽  
Kumaraswamy Ponnambalam ◽  
Amir Khajepour ◽  
Seyed Mohammad Hashemi
Keyword(s):  
Sensitivity Analysis ◽  
Design Parameters ◽  
Arbitrary Distribution ◽  
Voltage Response ◽  
Effective Parameters ◽  
Yield Optimization ◽  
Tunable Capacitor ◽  
Tunable Capacitors ◽  
Design Variables ◽  
Final Yield

The fabrication of MEMS tunable capacitors faces many uncertainties in which the fabricated dimensions differ from nominal values. This deviation in a tunable capacitor may cause significant variation in the capacitance-voltage response. In this paper, the effect of uncertainty in parallel-plate tunable capacitors is studied to maximize the yield under given criteria. A new method for yield optimization of tunable MEMS capacitors is developed. The method can take into account any arbitrary distribution and is not restricted to normality assumptions. The optimal designs verified by Monte-Carlo simulation exhibits considerable improvement in the yield. A sensitivity analysis is then performed to refine the design variables and maximize the yield based on the most effective parameters. When the fabrication process is already established and cannot be changed, the method can be employed to estimate the final yield for the process. The advantage of this method is demonstrated by numerical examples where the yield using initial design parameters is compared to the yield of the device with optimum parameters.

Particle Dampers for Workpiece Chatter Mitigation

2005 ◽  
Author(s):  
Neil D. Sims ◽  
Ashan Amarasinghe ◽  
Keith Ridgway
Keyword(s):  
Wide Frequency Range ◽  
Machining Process ◽  
Design Parameters ◽  
Depth Of Cut ◽  
Vibration Absorbers ◽  
Tuned Vibration Absorbers ◽  
Highly Nonlinear ◽  
Machining System ◽  
Order Of Magnitude ◽  
Particle Dampers

It is well known that the chatter stability of a machining process can be improved by increasing the structural damping of the system. To date this approach has been effectively used on various components of the machining system, for example boring bars, milling tools, and the machine structure itself. Various damping treatments have been proposed, including tuned vibration absorbers, active methods, and impact dampers. However, to date there has been little or no work to investigate the issue of particle dampers for this application. This special class of damper comprises a container of thousands of small granular particles which dissipate energy by friction and impact when the container vibrates. The resulting behaviour is highly nonlinear but can provide very high levels of damping across a wide frequency range. In the present study, particle dampers were applied to a workpiece to mitigate chatter during milling, and the limiting critical depth of cut was increased by an order of magnitude. This article gives an overview of the particle damper’s behaviour and key design parameters. Cutting trials employing the device are then described.

Novel Linearly Tunable MEMS Capacitors With Flexible Moving Electrodes

2008 ◽  
Author(s):  
Mohammad Shavezipur ◽  
Seyed Mohammad Hashemi ◽  
Amir Khajepour
Keyword(s):  
Parallel Plate ◽  
Design Methodology ◽  
Fem Simulation ◽  
Voltage Response ◽  
Parallel Plate Capacitor ◽  
Linear Region ◽  
High Tunability ◽  
Flexible Plates ◽  
Tuning Ratio ◽  
Capacitance Voltage

In conventional MEMS parallel-plate capacitor designs, the moving electrode is commonly modeled as a rigid plate with flexible boundary conditions provided by a set of supporting beams. Such a capacitor generates limited tuning ratio up to 1.5 and its capacitance-voltage response is nonlinear. This paper presents novel designs where the moving electrodes are fixed-edge flexible plates. The plate displacement is selectively limited by a set of rigid steps, located between two electrodes, to generate a smooth and linear response and high tunability. Three different step heights are considered in the design and the linearity of the C-V curve is maximized by modifying the geometry of the plate, and changing the location and order of steps. Since the analytical solution for coupled electrostatic-structural physics in this case does not exist, ANSYS® FEM simulation is performed to obtain the C-V curves and optimize the design. Two designs with different electrode shapes, rectangular and circular, are developed. For rectangular-plate capacitors, tunabilities ranging from 120% to 140% and high linearity are achieved. Circular-plate designs, on the other hand, generate lower tunabilities and an extremely linear region in C-V curves. Design methodology introduced in this research is not limited to proposed geometries and can be extended to different topologies to obtain a combination of high tunability and linearity.

Probabilistic Performance of Helical Compound Planetary System in Wind Turbine

2015 ◽  
Vol 10 (4) ◽  
Author(s):  
Fisseha M. Alemayehu ◽  
Stephen Ekwaro-Osire
Keyword(s):  
Wind Turbine ◽  
Multibody Systems ◽  
Planetary System ◽  
Design Parameters ◽  
Wind Turbine Gearbox ◽  
New Approach ◽  
Highly Nonlinear ◽  
Multibody Dynamic ◽  
Input Variables ◽  
Maintenance Process

The dynamics of contact, stress and failure analysis of multibody systems is highly nonlinear. Nowadays, several commercial and other analysis software dedicated for this purpose are available. However, these codes do not consider the uncertainty involved in loading, design, and assembly parameters. One of these systems with a combined high nonlinearity and uncertainty of parameters is the gearbox of wind turbines (WTs). Wind turbine gearboxes (WTG) are subjected to variable torsional and nontorsional loads. In addition, the manufacturing and assembly process of these devices results in uncertainty of the design parameters of the system. These gearboxes are reported to fail in their early life of operation, within three to seven years as opposed to the expected twenty years of operation. Their downtime and maintenance process is the most costly of any failure of subassembly of WTs. The objective of this work is to perform a probabilistic multibody dynamic analysis (PMBDA) of a helical compound planetary stage of a selected wind turbine gearbox that considers ten random variables: two loading (the rotor speed, generator side torque), and eight design parameters. The reliability or probabilities of failure of each gear and probabilistic sensitivities of the input variables toward two performance functions have been measured and conclusions have been drawn. The results revealed that PMBDA has demonstrated a new approach of gear system design beyond a traditional deterministic approach. The method demonstrated the components' reliability or probability of failure and sensitivity results that will be used as a tool for designers to make sound decisions.

Characterization and Modeling of Thermal Buckling in Eccentrically Loaded Microfabricated Nickel Beams for Adaptive Cooling

2005 ◽  
Author(s):  
Matthew McCarthy ◽  
Nicholas Tiliakos ◽  
Vijay Modi ◽  
Luc Freche´tte
Keyword(s):  
Closed Form ◽  
Analytical Model ◽  
Thermal Loading ◽  
Thermal Buckling ◽  
Design Parameters ◽  
Experimental Measurements ◽  
Test Results ◽  
Actuation Mechanism ◽  
Highly Nonlinear ◽  
Form Model

The design, fabrication and testing of micromachined nickel beams buckling under thermal loading will be presented in this paper. The focus will be on characterizing key design parameters important to the implementation of electroplated nickel beams as the actuation mechanism in a thermally adaptive microvalve. An analytical model of the thermal buckling phenomena has been developed and validated with test results from electroplated nickel beams with slight eccentricities. Highly nonlinear deflection versus temperature curves were predicted by the closed form model and match well with experimental measurements. Buckling deflections of more than 50μm were achieved at actuation temperatures under 100°C. The nickel beam fabrication process will be presented, as well as various fabrication related issues impacting the actuation capabilities of the beams.

A New Approach for Explicit Construction of Moldability Based Feasibility Boundary for Polymer Heat Exchangers

2011 ◽  
Author(s):  
Timothy Hall ◽  
Madan Mohan Dabbeeru ◽  
Satyandra K. Gupta
Keyword(s):  
Heat Exchangers ◽  
Intelligent Design ◽  
Nonlinear Process ◽  
Explicit Construction ◽  
Computational Experiments ◽  
Design Parameters ◽  
New Approach ◽  
Highly Nonlinear ◽  
Computationally Intensive ◽  
Polymer Heat Exchangers

Incorporating manufacturing feasibility is a very important consideration during the design optimization process and this paper is interested in investigating the molding feasibility of polymer heat exchangers. This application requires the explicit construction of the boundary, represented as a surface based on the parameter space, which separates the feasible and infeasible design space. The feasibility boundary for injection molding in terms of the design parameters is quite complex due to the highly nonlinear process physics, which, consequently, makes molding simulation computationally-intensive and time-consuming. Moreover, in heat exchanger applications, the optimal design often lies on the feasibility boundary. This paper presents a new approach for the explicit construction of a moldability-based feasibility boundary for polymer heat exchangers. The proposed approach takes inspiration from intelligent design of experiments and incorporates ideas from the field of active learning to minimize the number of computational experiments needed to construct the feasibility boundary. Our results show that the proposed approach leads to significant reduction in the number of computational experiments needed to build an accurate model of the feasibility boundary.

Study on Efficiency Factor of Bearing Capacity of Multi-Element Composite Foundation of Concrete Column and Lime Column

2011 ◽  
Vol 255-260 ◽  
pp. 178-182
Author(s):  
Xian Zhi Wang
Keyword(s):  
Bearing Capacity ◽  
Nonlinear Behavior ◽  
Composite Foundation ◽  
Theoretical Research ◽  
Design Parameters ◽  
Concrete Column ◽  
Highly Nonlinear ◽  
Elasto Plasticity ◽  
Efficiency Factors ◽  
Lime Column

Based on the model tests and the results of theoretical research, considered elasto-plasticity of the soil and highly nonlinear behavior of contact with columns and soil, more reasonable numerical model on multi-element composite foundation of concrete column and lime column was built. By changing the design parameters (the diameter of concrete column, the diameter of lime column, the length of lime column, cushion thickness), efficiency factors of bearing capacity of multi-element composite foundation on concrete column and lime column were to play a more systematic study. Some conclusions were drawn in favor of engineering design and theoretical study of multi-element composite foundation of concrete column and lime column.

scholarly journals Bio-inspired origami metamaterials with metastable phases through mechanical phase transitions

2021 ◽  
pp. 1-13
Author(s):  
Ke Liu ◽  
Tomohiro Tachi ◽  
Glaucio H. Paulino
Keyword(s):  
Structural Instability ◽  
Two Dimensions ◽  
Important Application ◽  
Metastable Phases ◽  
Design Parameters ◽  
Local Geometry ◽  
Unit Cells ◽  
Geometric Origin ◽  
Wave Guides ◽  
Multi Phase

Abstract Structural instability, once a catastrophic phenomenon to be avoided in engineering applications, is being harnessed to improve functionality of structures and materials, and has catalyzed a substantial research in the field. One important application is to create functional metamaterials that deform their internal structure to adjust performance, resembling phase transformations in natural materials. In this paper, we propose a novel origami pattern, named the Shrimp pattern, with application to multi-phase architected metamaterials whose phase transition is achieve mechanically by snap-through. The Shrimp pattern consists of units that can be easily tessellated in two dimensions, either periodically with homogeneous local geometry, or non-periodically with heterogeneous local geometries. We can use a few design parameters to program the unit cell to become either monostable or bistable, and tune the energy barrier between the bistable states. By tessellating these unit cells into an architected metamaterial, we can create complex yet navigable energy landscape, leading to multiple metastable phases of the material. As each phase has different geometry, the metamaterial can switch between different mechanical properties and shapes. The geometric origin of the multi-stable behavior implies that our designs are scale-independent, making them candidates for a variety of innovative applications, including reprogrammable materials, reconfigurable acoustic wave guides, and microelectronic mechanical systems and energy storage systems.

scholarly journals Novel RF MEMS tunable capacitors

2021 ◽  
Author(s):  
Zewdu Hailu
Keyword(s):  
Residual Stress ◽  
Rf Mems ◽  
Stress Gradient ◽  
Repulsive Force ◽  
Quality Factors ◽  
Comb Drive ◽  
Moving Plate ◽  
Tunable Capacitor ◽  
Tunable Capacitors ◽  
Residual Stress Gradient

Current tunable devices such as filters, impedance matching networks and oscillators have problems that degrade their performance at high microwave frequencies. Tuning ratios and quality factors are the major problems associated with semiconductor based tuning components. This thesis presents the design, fabrication and testing of two novel RF MEMS tunable capacitors. The first tunable capacitor is designed using electrostatic repulsive-force actuators which produce an upward movement of the moving plate of a tunable capacitor. The repulsive-force actuator is free of pull-in effect and capable of reaching large displacement. Gap increasing tunable capacitors with areas of 162μm×220μm and 300μm×302μm are developed using electrostatic repulsive-force actuators. The capacitances are calculated using simulations and maximum tuning ratios of 438.5% and 230% are obtained for a parallel and inclined plate designs, respectively, with capacitance-voltage linearity of 96.28% and 95.14%, respectively, in the presence of RF voltage. The second tunable capacitor is developed using residual stress gradient based vertical comb-drive actuator. Conventional vertical comb-drive actuators need two vertical comb fingers, i.e., one for the fixed and one for the moving comb. MetalMUMPs process provides a 20μm thick nickel layer which is subject to residual stress gradient along its thickness. Using the residual stress gradient two curve-up beams are devised to bend out of plane and upward. A moving plate is connected between the middles of the curve-up beams through supporting springs and is raised above the substrate. The moving fingers are connected to opposite sides of the moving plate. The fixed comb-drive fingers are anchored to the substrate. When a voltage is applied, the moving fingers move down towards the fixed fingers. As a result, the capacitance between the moving fingers and the fixed fingers change. Prototypes are fabricated to verify the working principles of this novel actuator using the MetalMUMPs process. Tunable capacitors based on this actuator are experimentally analyzed. Quality factors of 106.9-162.7 at 0.8GHz and 42.4-51.9 at 1.24GHz are obtained over actuation voltage of 0-100V. An optimal design of the tunable capacitors achieved a tuning ratio of 194.4% at 162.5V with linearity of 97.84%

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