Engineering Commons^™

A Variable-Stiffness Compliant Mechanism For Stiffness-Controlled Haptic Interfaces, Jeffrey C. Hawks

Theses and Dissertations

In this research a variable-stiffness compliant mechanism was developed to generate variable force-displacement profiles at the mechanisms coupler point. The mechanism is based on a compliant Roberts straight-line mechanism, and the stiffness is varied by changing the effective length of the compliant links with an actuated slider. The variable-stiffness mechanism was used in a one-degree-of-freedom haptic interface to demonstrate the effectiveness of varying the stiffness of a compliant mechanism. Unlike traditional haptic interfaces, in which the force is controlled using motors and rigid links, the haptic interface developed in this work displays haptic stiffness via the variable-stiffness compliant mechanism. The …

Fully Compliant Mechanisms For Bearing Subtraction In Robotics And Space Applications, Ezekiel G. Merriam

Theses and Dissertations

Robotics and space applications represent areas where compliant mechanisms can continue to make a significant impact by reducing costs and weight while improving performance. Because of the nature of these applications, a common need is for bearing replacement mechanisms, or mechanisms that perform the function of a bearing without the complexity and failure modes associated with bearings. Static balancing is a design strategy that attempts to reduce the actuation effort of a mechanism, and has been applied to compliant mechanisms in some applications. Monolithic construction, especially by means of 3D printing technology, is a strategy whereby the mechanism links and …

Design Principles And Preliminary Actuation Approaches For Novel Multiple-Layer Lamina Emergent Mechanisms, Paul Shumway Gollnick

Theses and Dissertations

Multiple-layer Lamina Emergent Mechanisms (MLEMs) are mechanisms made from multiple sheets (lamina) of material with motion that emerges out of the fabrication plane. This study has shown that understanding how layers are used in existing products and in nature provides insight into how MLEMs can also use layers to achieve certain tasks. The multi-layered nature of MLEMs and the interactions between these layers are what enhance the capabilities of MLEMs and allow them to better meet design objectives. Layer separation is one objective for which MLEMs are well-suited. Layer separation can have a variety of applications and there are a …

Piezoresistive Models For Polysilicon With Bending Or Torsional Loads, Gerrit T. Larsen

Theses and Dissertations

This thesis presents new models for determining piezoresistive response in long, thin polysilicon beams with either axial and bending moment inducing loads or torsional loads. Microelectromechanical (MEMS) test devices and calibration methods for finding the piezoresistive coefficients are also presented for both loading conditions. For axial and bending moment inducing loads, if the piezoresistive coefficients are known, the Improved Piezoresistive Flexure Model (IPFM) is used to find the new resistance of a beam under stress. The IPFM first discretizes the beam into small volumes represented by resistors. The stress that each of these volumes experiences is calculated, and the stress …

Achieving Complex Motion With Fundamental Components For Lamina Emergent Mechanisms, Brian Geoffrey Winder

Theses and Dissertations

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, …

Principles, Functions, And Concepts For Compliant Mechanically Reactive Armor Elements, Cameron S. Andersen

Theses and Dissertations

There exists a great need for armor systems with greater mass efficiencies and ballistic limits. This thesis explores the development of a new field of armor capable of satisfying the increased demand for modern armor: Mechanically Reactive Armor or MRA. More specifically, the thesis focuses on Compliant MRA or CMRA. From the physics governing projectile-armor interactions, principles governing successful design of MRA are identified and presented. These principles or design approaches focus primarily on rejecting, minimizing, or absorbing the incoming projectile's kinetic energy. After identifying these principles, the specific mechanical functions required by the principles are isolated. These functions represent …

Piezoresistive Sensing Of Bistable Micro Mechansim State, Jeffrey K. Anderson

Theses and Dissertations

The objective of this work is to demonstrate the feasibility of on-chip sensing of bistable mechanism state using the piezoresistive properties of polysilicon, thus eliminating the need for electrical contacts. Changes in position are detected by observing changes in resistance across the mechanism. Sensing the state of bistable mechanisms is critical in their various applications. The research in this thesis advances the modeling techniques of MEMS devices which use piezoresistivity for position sensing. A fully compliant bistable micro mechanism was designed, fabricated, and tested to demonstrate the feasibility of this sensing technique. Testing results from two fabrication processes, Fairchild's SUMMiT …

Compliant Ortho-Planar Spring Behavior Under Complex Loads, Nathan Oliver Rasmussen

Theses and Dissertations

This thesis presents research on the feasibility of applying compliant-ortho-planar springs (COPS) to rotational applications. The primary motivation of this research is the application of COPS to a continuously variable transmission (CVT). The design space limitations, loading conditions, stresses, stress concentrations, and limitations of current design tools, such as pseudo-rigid-body models (PRBM) for COPS, are discussed. A new 3D PRBM is presented along with a discussion on the possible applications of such to a rotating COPS. Stress stiffening and lateral stability are two major phenomena occurring in a rotating COPS. Both phenomena are a direct result of the inertial loads …

Compliant Mechanisms To Perform Bearing And Spring Function In High Precision Applications, Jesse R. Cannon

Theses and Dissertations

An increasing number of mechanical systems are being designed on the micro and meso scales. Assembly and maintenance become increasingly difficult as the size of mechanisms decrease, and the minimum size of traditional elements such as bearings and springs is limited. The backlash of bearings also limits their usefulness in applications where high precision and repeatability are needed. At small scales and for high precision applications, alternative, non-traditional elements are needed.

The objective of this thesis is to develop reliable and scalable compliant components to replace bearings and helical springs. Components replacing springs must be able to produce specified torque/motion …

Compliant Centrifugal Clutches: Design, Analysis, And Testing, Nathan B. Crane

Theses and Dissertations

Existing classes of centrifugal clutch concepts were reviewed. The pseudo-rigid-body model (PRBM), rigid-body replacement synthesis, force-deflection analysis, compliance potential evaluation, and compliant concept evaluation were used to develop effective new centrifugal clutch concepts. These methods helped develop and model four novel compliant centrifugal clutch designs, model two existing designs, and identify a concept with excellent potential for low-cost centrifugal clutch applications. This concept, the floating opposing arm (FOA) clutch, doubles the torque capacity metric relative to existing compliant designs. Torque and engagement speed models for this clutch were developed and verified against four prototype clutches. Additional novel designs devel-oped through …

Development And Design Of Constant-Force Mechanisms, Brent Lewis Weight

Theses and Dissertations

This thesis adds to the knowledge base of constant-force mechanisms (CFMs). It begins by reviewing past work done in the area of CFMs and then develops new nondimensionalized parameters that are used to simplify the calculations required to design a CFM. Comparison techniques are then developed that utilize these non-dimensionalized parameters to compare mechanisms based on stiffnesses, percent constant-force, actual lengths, normal displacements, and feasible design orientations. These comparison techniques are then combined with optimization to define new mechanisms with improved performance and range of capabilities. This thesis also outlines a design process, methods to identify mechanisms that are suitable …