Mechanical Engineering Commons^™

Coordinated Uav Target Assignment Using Distributed Calculation Of Target-Task Tours, David H. Walker

Theses and Dissertations

This thesis addresses the improvement of cooperative task allocation to vehicles in multiple-vehicle, multiple-target scenarios through the use of more effective preplanned tours. Effective allocation of vehicles to targets requires knowledge of both the team objectives and the contributions that individual vehicles can make toward accomplishing team goals. This is primarily an issue of individual vehicle path planning --- determining the path the vehicles will follow to accomplish individual and team goals. Conventional methods plan optimal point-to-point path segments that often result in lengthy and suboptimal tours because the trajectory neither considers future tasks nor the overall path. However, cooperation …

A Comprehensive Model For Technology Push Product Development, Gregory Loren Bishop

Theses and Dissertations

Successful product development has been a fundamental part of many of today's companies and their continued prosperity depends on continuing to develop new products in the future. There are many models of product development. The two most common classes of development are market pull (MP) and technology push (TP). TP product development differs from MP in that the development begins with a specified technology rather than a specified customer. Because TP development is generally considered more difficult and challenging, most of the product development research has focused on MP development and many researchers and practitioners favor MP development over TP …

The Contextable: Building And Testing An Intelligent, Context-Aware Kitchen Table, Daniel Matthew Hoopes

Theses and Dissertations

The purpose of this thesis was to design and evaluate The ContexTable, a context-aware system built into a kitchen table. After establishing the current status of the field of context-aware systems and the hurdles and problems being faced, a functioning prototype system was designed and built. The prototype makes it possible to explore established, untested theory and novel solutions to problems faced in the field.

High-Torque Capacity Compliant Centrifugal Clutches, Ryan G. Weight

Theses and Dissertations

This thesis developed high-torque-capacity floating opposing arm clutches that are manufactured with standard economical manufacturing processes, while maintaining critical performance characteristics. Contact engagement speed and torque capacity models were created for the Hoffco-Comet, floating-opposing-arm (FOA), and floating 1 (F1) clutches. Sensitivity analyses were performed to identify key design parameters. A robust compliant FOA clutch was designed by minimizing the tolerance for both contact engagement speed and torque capacity. The robust design insures that the clutch will operate within the prescribed application constraints. Additional modeling showed that using a layered clutch would significantly tighten the contact engagement speed and torque performance …

Percolation Paths Of Three-Dimensions In Sensitized Stainless Steel, Alisa Jean Henrie

Theses and Dissertations

The study of three-dimensional percolation paths through materials is important in its contribution to understanding defect sensitive properties of materials. This work shows the importance of grain boundary character in modeling defect sensitive boundaries. Also presented are trends of percolation of sensitized grain boundaries in 304 stainless steel (304SS). Of particular interest is how open paths form in a three-dimensional model created through serial sectioning. Evidence is presented that triple or quadruple points that contain typically two boundaries with special character that intersect the percolation path break up the path. Some grains with no known special qualities (i.e., CSL) have …

Development Of Commercially Viable Compliant Mechanisms Using The Pseudo-Rigid-Body Model: Case Studies Of Parallel Mechanisms, Christopher A. Mattson, Larry L. Howell, Spencer P. Magleby

Faculty Publications

Analysis and synthesis of compliant mechanisms has recently been the subject of significant study in the research community. This focus has led to a number of design approaches for developing compliant mechanisms. This paper describes the value of using the Pseudo-Rigid-Body Model (PRBM) to design compliant mechanisms for commercial products. Application of the PRBM is illustrated through the development of two parallel mechanisms: a bicycle derailleur and parallel-motion bicycle brakes. The PRBM allows compliant mechanisms to be modeled and analyzed as rigid-body mechanisms and significantly reduces the complexity of analysis. Mechanisms with straightforward properties are used to demonstrate the use …

Effects Of Friction Stir Welding On Polymer Microstructure, Seth R. Strand

Theses and Dissertations

This work establishes the relationships between several key Friction Stir Welding process parameters and the resulting microstructural and flexural properties of the welded joint. A series of four single parameter experiments were run. The parameters investigated were pin diameter, feedrate, shoe temperature, and pressure time. Butt welds were made in 6 mm thick stress-relieved extruded polypropylene sheet. Three-point bend tests were used to determine the ultimate flexural strength and coincident strain. The maximum bend angle before failure was used to label the welds as "good or bad." An optical microscope capable of cross polarization was used to examine and photograph …

Microstructures By Design: Linear Problems In Elastic-Plastic Design, Brent L. Adams, B. Henrie, M. Lyon

Faculty Publications

Materials microstructure is considered to be a design variable in the methodology called microstructure sensitive design (MSD). Based upon existing homogenization relations, relating the first-order representation of microstructure (the local state distribution function) to elastic and yield properties, the paper describes the construction of properties closures. These establish the theoretically-possible combinations of properties achievable by the set of all possible microstructures, which is called the microstructure hull. Exemplary homogenization relations are shown to be, typically, hypersurfaces (often hyperplanes) in the Fourier space in which the microstructure hull resides. All points lying on (or to one side of) the hypersurface, that …

Microstructure Design Of A Two Phase Composite Using Two-Point Correlation Functions, Brent L. Adams, H. Garmestani, G. Saheli

Faculty Publications

This work has been funded under the AFOSR Grant no. F49620-03-1-0011 and Army Research Lab contract no. DAAD17-02-P-0398 and DAAD 19-01-1-0742. Two-point distribution functions are used here as to introduce "Microstructure Sensitive Design" in two-phase composites. Statistical distribution functions are commonly used for the representation of microstructures and also for homogenization of materials properties. The use of two-point statistics allows the composite designer to include the morphology and distribution in addition to the properties of the individual phases and components. Statistical continuum mechanics is used to make a direct link between the microstructure and properties (elastic and plastic) in terms …

Coordinated Uav Target Assignment Using Distributed Tour Calculation, David H. Walker, Timothy W. Mclain, Jason K. Kowlett

Faculty Publications

In this chapter a method for assigning unmanned aerial vehicle agents to targets through the use of preplanned vehicle tours is presented. Assignments are based on multi-target tours that consider the spread of the targets and the sensor capabilities of the vehicles. In this way, the individual agents and the team as a whole make better use of team resources and improve team cooperation. Planning and assignments are accomplished in reasonable computational time through the use of heuristics to reduce the problem size.

Establishing A Quantitative Foundation For Exactly Constrained Design, Alisha M. Hammond

Theses and Dissertations

Exactly constrained (EC) design is a robust design method which can be used for mechanical assemblies. It entails using the minimum number of constraints to eliminate all desired motion.

While found by some engineers in industry to have many benefits (including robust assembly, no binding or play, ease of assembly, and the ability to tolerate the wear of parts), EC designs remain somewhat unrecognized by academia. One reason for this minimal exposure may be the lack of a quantitative foundation for such designs. This thesis describes the history and current background for EC designs, and it also begins to develop …

Selecting Appropriate Product Concepts For Manufacture In Developing Countries, Danielle Johnson

Theses and Dissertations

There is a noticeable lack of production of indigenously engineered and manufactured products in Less Developed Countries (LDC's). Few products developed in these LDC's could be viable in competitive markets or even sold as components and supplies to other manufacturers of competitive goods. Assumintg that these less developed countries do not innovate and manufacture because they cannot, the next logical question to ask is why can they not?

This thesis looks at the problems of manufacture and design in LDC's from the standpoint of Product Development. It begins by looking at development theories, namely top down and bottom up and …

Dynamic Modeling Of Compliant Constant-Force Compression Mechanisms, Cameron Boyle, Larry L. Howell, Spencer P. Magleby, Mark S. Evans

Faculty Publications

A mathematical dynamic model is derived for compliant, constant-force compression-mechanisms, based on the pseudo-rigid-body model simplification of the device. The compliant constant-force compression mechanism (CFCM) is a slider mechanism incorporating large-deflection beams, which outputs near-constant-force across the range of its designed deflection. The equation of motion is successfully calibrated with empirical data from five separate mechanisms, comprising two basic configurations of CFCMs. The dynamic equation is derived from a generalized pseudo-rigid-body model. This allows every configuration to be represented by the same model, so a separate treatment is not required for each configuration. An unexpected dynamic trait of the constant-force …

Multiple Uav Cooperative Search Under Collision Avoidance And Limited Range Communication Constraints, Randal W. Beard, Timothy W. Mclain

Faculty Publications

This paper focuses on the problem of cooperatively searching, using a team of unmanned air vehicles (UAVs), an area of interest that contains regions of opportunity and regions of potential hazard. The objective of the UAV team is to visit as many opportunities as possible, while avoiding as many hazards as possible. To enable cooperation, the UAVs are constrained to stay within communication range of one another. Collision avoidance is also required. Algorithms for team-optimal and individually-optimal/team-suboptimal solutions are developed and their computational complexity compared. Simulation results demonstrating the feasibility of the cooperative search algorithms are presented.

The Distribution Of Internal Interfaces In Polycrystals, Brent L. Adams, Bassem S. El-Dasher, Gregory S. Rohrer, Anthony D. Rollett, David M. Saylor, Paul Wynblatt

Faculty Publications

This work was supported by the MRSEC program of the National Science Foundation under Award Number DMR-0079996. Recent advances both in experimental instrumentation and computing power have made it possible to interrogate the distribution of internal interfaces in polycrystals and the three dimensional structure of the grain boundary network with an unprecedented level of detail. The purpose of this paper is to review techniques that can be used to study the mesoscopic crystallographic structure of grain boundary networks and to summarize current findings. Recent studies have shown that grain surfaces within dense polycrystals favor the same low energy planes that …

Modeling The Transient Response Of A Thermosyphon, James Kirk Storey

Theses and Dissertations

Thermosyphon transient operation was numerically modeled. The numerical model presented in this work overcame the limitations of previous studies by including transient conduction in the vessel wall, shear stress between the rising vapor and the falling film in the thermosyphon, the influence of the mass in the liquid pool in the evaporator, and by using a more refined and accurate numerical grid. Unique to this model was the accounting for temporal changes in the effective length of the vapor space due to the expanding and contracting of non-condensable gases in the vapor space. The model assumed quasi-steady one-dimensional vapor flow, …

A Closed-Form Dynamic Model Of The Compliant Constant-Force Mechanism Using The Pseudo-Rigid-Body Model, Cameron Boyle

Theses and Dissertations

A mathematical dynamic model is derived for the compliant constant-force mechanism, based on the pseudo-rigid-body model simplification of the device. The compliant constant-force mechanism is a slider mechanism incorporating large-deflection beams, which outputs near-constant-force across the range of its designed deflection. The equation of motion is successfully validated with empirical data from five separate mechanisms, comprising two configurations of compliant constant-force mechanism. The dynamic model is cast in generalized form to represent all possible configurations of compliant constant-force mechanism. Deriving the dynamic equation from the pseudo-rigid-body model is useful because every configuration is represented by the same model, so a …

Predicting Drag Polars For Micro Air Vehicles, Mark Elden Luke

Theses and Dissertations

Drag polars for three Micro Air Vehicles (MAVs) were measured at Reynolds numbers of 70,000, 50,000, 30,000, and 10,000 and compared to predictions generated using the classical approach. The MAVs tested had different configurations and aspect ratios varying from 1.2 to 1.6 and ratios of wetted surface area to planform area from 2.6 to 3.9.

A force balance was used to measure the lift and drag on the MAVs at angles of attack ranging from -5 degrees (or -10 degrees) to 10 degrees. The force balance allowed the MAVs to rotate in the pitching axis. The MAV angle of attack …

Large Eddy Simulation Based Turbulent Flow-Induced Vibration Of Fully Developed Pipe Flow, Matthew Thurlow Pittard

Theses and Dissertations

Flow-induced vibration caused by fully developed pipe flow has been recognized, but not fully investigated under turbulent conditions. This thesis focuses on the development of a numerical Fluid-Structure Interaction (FSI) model that will help define the relationship between pipe wall vibration and the physical characteristics of turbulent flow. Commercial FSI software packages are based on Reynolds Averaged Navier-Stokes (RANS) fluid models, which do not compute the instantaneous fluctuations in turbulent flow. This thesis presents an FSI approach based on Large Eddy Simulation (LES) flow models, which do compute the instantaneous fluctuations in turbulent flow. The results based on the LES …

Predictive Joint Motion Limiting In Robotic Applications, Edward Red, Brian Fielding

Faculty Publications

Three joint space algorithms slow the Cartesian path motion when it appears that joint motion is approaching a joint, speed, or acceleration limit. All three algorithms use quadratic curve fitting to predict where the joint motion is heading, followed by a prediction as to how much time would elapse until a limit is reached.

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 …

A Texture Evolution Model In Cubic-Orthotropic Polycrystalline System, Brent L. Adams, H. Garmestani, D. S. Li

Faculty Publications

This work has been funded under the AFOSR Grant # F49620-03-1-0011 and Army Research Lab Contract # DAAD17-02-P-0398 and DAAD 19-01-1-0742. B.L. Adams acknowledges support of Army Research Office, Proposal No. 42566-MS. The authors express their sincere gratitude to Professor Surya Kalidindi, for helpful suggestions and correspondence for the derivation of the processing path functions. A new methodology based on a conservation principle in the orientation space is developed to simulate the texture evolution in a cubic-orthotropic polycrystalline system. A least squares error method was used to improve the accuracy of the simulation results obtained from the texture evolution function. …

A Five-Zone Model For Direct Injection Diesel Combustion, Rich Asay

Theses and Dissertations

Recent imaging studies have provided a new conceptual model of the internal structure of direct injection diesel fuel jets as well as empirical correlations predicting jet development and structure. This information was used to create a diesel cycle simulation model using C language including compression, fuel injection and combustion, and expansion processes. Empirical relationships were used to create a new mixing-limited zero-dimensional model of the diesel combustion process. During fuel injection five zones were created to model the reacting fuel jet: 1) liquid phase fuel 2) vapor phase fuel 3) rich premixed products 4) diffusion flame sheath 5) surrounding bulk …

A Descriptive Performance Model Of Small, Low Cost, Diskless Beowulf Clusters, Curtis R. Nielson

Theses and Dissertations

Commodity supercomputing clusters known as Beowulf clusters, have become a low cost alternative to traditional supercomputers. Beowulf clusters combine inexpensive computers and specialized software to achieve supercomputing power. The processing nodes in a diskless Beowulf cluster do not have a local hard disk unlike the nodes in most commodity clusters. Research has provided performance information for diskless clusters built with expensive, high performance equipment. Beowulf clusters use commodity off-the-shell hardware, and little information is available about their performance. This research includes the construction of several diskless Beowulf clusters. Using the NAS Parallel Benchmarks, the performance of these clusters was measured. …

Autonomous Vehicle Technologies For Small Fixed Wing Uavs, Derek B. Kingston, Randal Beard, Timothy Mclain, Michael Larsen, Wei Ren

Faculty Publications

Autonomous unmanned air vehicle flight control systems require robust path generation to account for terrain obstructions, weather, and moving threats such as radar, jammers, and unfriendly aircraft. In this paper, we outline a feasible, hierarchal approach for real-time motion planning of small autonomous fixed-wing UAVs. The approach divides the trajectory generation into four tasks: waypoint path planning, dynamic trajectory smoothing, trajectory tracking, and low-level autopilot compensation. The waypoint path planner determines the vehicle's route without regard for the dynamic constraints of the vehicle. This results in a significant reduction in the path search space, enabling the generation of complicated paths …

A Study Of Radiofrequency Cardiac Ablation Using Analytical And Numerical Techniques, Ryan Todd Roper

Theses and Dissertations

Studies on radiofrequency (RF) ablation are often aimed at accurately predicting tissue temperature distributions by numerical solution of the bioheat equation. This thesis describes the development of an analytical solution to serve as a benchmark for subsequent numerical solutions. The solution, which was obtained using integral transforms, has the form of a surface integral nested within another surface integral. An integration routine capable of evaluating such integrals was developed and a C program was written to implement this routine. The surface integration routine was validated using a surface integral with a known analytical solution. The routine was, then, used to …

Incorporating Functionally Graded Materials And Precipitation Hardening Into Microstructure Sensitive Design, Mark Edward Lyon

Theses and Dissertations

The methods of MSD are applied to the design of functionally graded materials. Analysis models are presented to allow the design of compliant derailleur for a case study and constraints are placed on the design. Several methods are presented for relating elements of the microstructure to the properties of the material, including Taylor yield theory, Hill elastic bounds, and precipitation hardening.

Applying n-point statistics to the MSD framework is also discussed. Some results are presented for the information content of the 2-point correlation statistics that follow from the methods used to integrate functionally graded materials into MSD.

For the compliant …

Design And Analysis Of End-Effector Systems For Scribing On Silicon, Bennion Rhead Cannon

Theses and Dissertations

This thesis investigates end-effector systems used in a chemomechanical scribing process. Chemomechanical scribing is a method of patterning silicon to selectively deposit a monolayer of material on the surface of the silicon. This thesis details the development of a unique end-effector for chemomechanical scribing using a compliant mechanism solution. The end-effector is developed to scribe lines that have uniform geometry and produce less chipping on the surface of the silicon. The resulting scribing mechanism is passively controlled, has high lateral stiffness, and low axial stiffness. The mechanism is analyzed using the pseudo-rigid-body model and linear-elastic beam method to determine the …

Learning Real-Time A* Path Planner For Sensing Closely-Spaced Targets From An Aircraft, Jason K. Howlett, Michael A. Goodrich, Timothy W. Mclain

Faculty Publications

This work develops an any-time path planner, based on the learning real-time A* (LRTA*) search, for generating flyable paths that allow an aircraft with a specified sensor footprint to sense a group of closely-spaced targets. The LRTA* algorithm searches a tree of flyable paths for the branch that accomplishes the desired objectives in the shortest distance. The tree of paths is created by assembling primitive turn and straight sections of a specified step size. The operating parameters for the LRTA* search directly influence the running time and path-length performance of the search. A modified LRTA* search is presented that terminates …

Analysis And Design Of Surface Micromachined Micromanipulators For Out-Of-Plane Micropositioning, Kimberly A. Jensen

Theses and Dissertations

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).