Global ETD Search

1	Modeling and Parameter Study of Bistable Spherical Compliant Mechanisms Smith, Chester 01 January 2011 (has links) The bistable spherical compliant mechanism (BSCM) is a novel device capable of large, repeatable, out-of-plane motion, characteristics that are somewhat difficult to achieve with surface micromachined microelectromechanical systems. An improved pseudo-rigid-body model (PRBM) to predict the behavior of the BSCM is presented. The new model was used to analyze seven different versions of the device, each with a different compliant joint length. The new model, which adds torsion, is compared with a finite element analysis (FEA) beam model. The new model more closely approximates the results yielded by FEA than previous models used to analyze the BSCM. Future work is needed to quantify stress-stiffening interactions between bending and torsion. Both FEA and the current models show that increasing the length of the compliant segment decreases the amount of force required to actuate the device. 3D MEMS Microelectromechanical Ortho-Planar Virtual Work American Studies Arts and Humanities Engineering Mechanical Engineering
2	Moment-Dependent Pseudo-Rigid-Body Models for Beam Deflection and Stiffness Kinematics and Elasticity Espinosa, Diego Alejandro 24 March 2009 (has links) This thesis introduces a novel parametric beam model for describing the kinematics and elastic properties of ortho-planar compliant Micro-Electro-Mechanical Systems (MEMS) with straight beams subject to specific buckling loads. Ortho-planar MEMS have the ability to achieve motion out the plane on which they were fabricated, characteristic that can be used to integrate optical devices such as variable optical attenuators and micro-mirrors. In addition, ortho-planar MEMS with large output forces and long strokes could be used to develop new applications such as tactile displays, active Braille, and actuation of micro-mirrors. In order to analyze the kinematics and elasticity of a curved beam contained in a Micro Helico-Kinematic Platform (MHKP) device, this thesis offers an improved model of straight and curved flexures under compressive loads. This model uses an approach similar to the one applied to develop a regular Pseudo-Rigid -Body Model but it differs in the definition of a key parameter, the characteristic radius factor, γ, which is not a constant, but a function of the moment, γ*=γ(M) . This approach allows for the Pseudo-Rigid-Body Model (PRBM) to describe the motion taken by the deflected beam precisely over a large range of motion. In developing the model, this thesis describes kinematic and elastic parameters such as the angle coefficient, C9, the characteristic radius, γl, and the torque coefficient, Tθ. Furthermore, the torque coefficient is divided into two component functions, Tf, and, Tm, which can be used to find the working loads (force and moment) on the beam. The input displacement is the only needed state variable, object variables, which describe the beam, include the material modulus of elasticity, E, the moment of inertia, I, and its length, l. Flexible mechanisms curved beam parametric model ortho-planar motion virtual work American Studies Arts and Humanities
3	Ortho-Planar Mechanisms for Microelectromechanical Systems Lusk, Craig P. 07 July 2005 (has links) (PDF) A method for representing the design space of ortho-planar mechanisms has been developed. The method is based on the Theorem of Equality of Orientation Set Measures (TEOSM) which allows mechanisms to be represented by points in an abstract space. The method is first developed for single loop planar folded mechanisms with revolute joints, and later extended to mechanisms with prismatic joints and to spherical folded mechanisms. Functions which assign a value to each point in design space can be used to describe classes of mechanisms and evaluate their utility for MEMS design. Additionally, this work introduces the use of spherical mechanisms in MEMS design. Spherical mechanisms have characteristics that may be useful in MEMS, including the capability of spatial positioning of a link and the ability to convert rotation about an axis perpendicular to the substrate to rotation about an axis parallel to the substrate. Spherical kinematics has been used to develop three novel mechanisms, the Micro Helico-Kinematic Platform (MHKP), the Spherical Bistable Mechanism (SBM), and the Three-degree-of-freedom Platform (3DOFP). Mathematical models of these devices have been developed and MEMS prototypes have been designed and fabricated. MEMS Ortho-planar out-of-plane pop-up design space Mechanical Engineering
4	Analysis and Design of Surface Micromachined Micromanipulators for Out-of-Plane Micropositioning Jensen, Kimberly A. 23 July 2003 (has links) (PDF) This thesis introduces two ortho-planar MEMS devices that can be used to position microcomponents: the XZ Micropositioning Mechanism and the XYZ Micromanipulator. The displacement and force relationships are presented. The devices were fabricated using surface micromachining processes and the resulting mechanisms were tested. A compliant XYZ Micromanipulator was also designed to reduce backlash and binding. In addition, several other MEMS positioners were fabricated and tested: the Micropositioning Platform Mechanism (MPM), the Ortho-planar Twisting Micromechanism (OTM), and the Ortho-planar Spring Micromechanism (OSM). MEMS microelectromechanical systems micropositioning compliant mechanisms out-of-plane ortho-planar surface micromachining thermal actuation thermomechanical in-plane microactuator TIM Mechanical Engineering
5	Fundamental Components for Lamina Emergent Mechanisms Jacobsen, Joseph O. 22 February 2008 (has links) (PDF) This thesis introduces lamina emergent mechanisms (LEMs) and presents components that can be used as building blocks to create LEMs capable of more complex motion. As the name suggests, lamina emergent mechanisms are fabricated out of planar materials (the lamina) but their motion is out of that plane (emergent). Lamina emergent mechanisms can provide benefits that include reduced manufacturing costs and minimal volume when in the planar state. The compact initial state of LEMs is beneficial in reducing shipping costs, especially in volume critical applications. LEMs also exhibit the potential benefits of compliant mechanisms, namely increased precision, reduced weight, reduced wear, and part count reduction. The LEM components presented in this thesis include flexible segments, fundamental mechanisms, and a new complaint joint, the lamina emergent torsional (LET) Joint. The flexible segments are developed through changes in geometry, boundary/loading conditions, and material. The fundamental mechanisms presented have motion similar to planar change-point four-bar and six-bar mechanisms, and spherical change-point mechanisms. The LET Joint is presented as a compliant joint suited for applications where large angular rotation is desired, but high off-axis stiffness is not as critical. The joint is introduced and the equations necessary for determining the force-deflection characteristics and stress are presented. Since the LET Joint can be fabricated from a single planar layer, it is well suited for macro and micro applications. Illustrative examples of the LET Joint are provided with devices fabricated from materials as diverse as steel, polypropylene, and polycrystalline silicon. compliant mechanism lamina emergent mechanism torsional hinge lamina emergent torsional (LET) joint planar fabrication ortho-planar mechanism Mechanical Engineering
6	Developments Toward a Micro Bistable Aerial Platform: Analysis of the Quadrantal Bistable Mechanism Muñoz, Aaron A 30 October 2008 (has links) The Bistable Aerial Platform (BAP) has been developed in order to further enlarge the repertoire of devices available at the microscale. This novel device functions as a switch in that its platform can lock in two positions, up or down. Herein, it will be examined and explained, but a true understanding of its workings requires a better understanding of its compliant constituent parts. The Helico-Kinematic Platform (HKP), which serves as an actuator for the BAP, is currently under investigation by another researcher and will be merely touched upon here. The focus, therefore, will rest on the analysis of the Quadrantal Bistable Mechanism (QBM), the principle component of the BAP. A preliminary pseudo-rigid-body model, an aid for the understanding of compliant mechanisms, will also be examined for the QBM. The models developed for these two devices, the HKP and QBM, can later be combined to form a full model of the Bistable Aerial Platform. microelectromechanical systems (MEMS) compliant out-of-plane ortho-planar 3-D mechanism pop-up structure pseudo-rigid-body model American Studies Arts and Humanities
7	Achieving Complex Motion with Fundamental Components for Lamina Emergent Mechanisms Winder, Brian Geoffrey 01 March 2008 (has links) (PDF) Designing mechanical products in a competitive environment can present unique challenges, and designers constantly search for innovative ways to increase efficiency. One way to save space and reduce cost is to use ortho-planar compliant mechanisms which can be made from sheets of material, or lamina emergent mechanisms (LEMs). This thesis presents principles which can be used for designing LEMs. Pop-up paper mechanisms use topologies similar to LEMs, so it is advantageous to study their kinematics. This thesis outlines the use of planar and spherical kinematics to model commonly used pop-up paper mechanisms. A survey of common joint types is given, as well as an overview of common monolithic and layered mechanisms. In addition, it is shown that more complex mechanisms may be created by combining simple mechanisms in various ways. The principles presented are applied to the creation of new pop-up joints and mechanisms, which also may be used for lamina emergent mechanisms. Models of the paper mechanisms presented in Chapter 2 of the thesis are found in the appendix, and the reader is encouraged to print, cut out and assemble them. One challenge associated with spherical and spatial LEM design is creating joints with the desired motion characteristics, especially where complex spatial mechanism topologies are required. Hence, in addition to a study of paper mechanisms, some important considerations for designing joints for LEMs are presented. A technique commonly used in robotics, using serial chains of revolute and prismatic joints to approximate the motion of complex joints, is presented for use in LEMs. Important considerations such as linkage configuration and mechanism prototyping are also discussed. Another challenge in designing LEMs is creating multi-stable mechanisms with the ability to have coplanar links. A method is presented for offsetting the joint axes of a spatial compliant mechanism to introduce multi-stability. A new bistable spatial compliant linkage that uses that technique is introduced. In the interest of facilitating LEM design, the final chapter of this thesis presents a preliminary design method. While similar to traditional methods, this method includes considerations for translating the mechanism topology into a suitable configuration for use with planar layers of material. paper mechanism pop-up popup pop up mechanism linkage paper engineering paper crafts origami kinematics spatial mechanism planar mechanism bistable multi-stable spherical mechanism ortho-planar compliant PRBM pseudo-rigid-body model Lamina Emergent Mechanism LEM sheet goods planar layer complex joint elemental joint spatial joint degrees of freedom mechanism modeling mechanism design serial joint chain parallel series fundamental components complex motion revolute prismatic spherical cylindric universal half planar RSSR RCCC RSRC RTRT Altmann Bricard Bennett Goldberg 6R 4R joint axis angular offset paper joint V-fold circular arch figure-8 single slit double slit tube strap arch knee mechanism 45 degree fold solid shape floating layer tent Mechanical Engineering

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