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Articles 1021 - 1050 of 1342

Full-Text Articles in Mechanical Engineering

Improved State Estimation For Miniature Air Vehicles, Andrew Mark Eldredge Aug 2006

Improved State Estimation For Miniature Air Vehicles, Andrew Mark Eldredge

Theses and Dissertations

Research in Unmanned Air Vehicles (UAV's) continues to push the limitations of size and weight. As technical advances have made UAV's smaller and less expensive, they have become more flexible and extensive in their roles. To continue using smaller and less expensive components while retaining and even enhancing performance requires more sophisticated processing of sensor data in order for the UAV to accurately determine its state and thereby allow the use of feedback in controlling the aircraft automatically. This work presents a three-stage state-estimation scheme for the class of UAV's know as Miniature Air Vehicles (MAV's). The first stage estimates …

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Preliminary Modeling, Control, And Trajectory Design For Miniature Autonomous Tailsitters, Nathan B. Knoebel, Stephen R. Osborne, Deryl Snyder, Timothy W. Mclain, Randal W. Beard, Andrew Mark Eldredge Aug 2006

Preliminary Modeling, Control, And Trajectory Design For Miniature Autonomous Tailsitters, Nathan B. Knoebel, Stephen R. Osborne, Deryl Snyder, Timothy W. Mclain, Randal W. Beard, Andrew Mark Eldredge

Faculty Publications

A tailsitter UAV has unique advantages over typical fixed wing aircraft or hovercraft. This paper highlights topics of interest in our preliminary research in developing a tailsitter UAV. An aerodynamic model and quaternion-based attitude and position control scheme is presented for controlling a tailsitter through hover maneuvers, with simulation results. Desired trajectories are also developed through feedback linearization of the dynamic equations, intended for quaternion-based attitude control. Finally, a hardware platform is proposed.

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Modeling And Validation Of Tension-Element Based Mechanisms For Golf Ball-Club Impact, Aaron Robison Jul 2006

Modeling And Validation Of Tension-Element Based Mechanisms For Golf Ball-Club Impact, Aaron Robison

Theses and Dissertations

Previous work has systematically and numerically demonstrated feasibility and performance benefits of the tension-element concept in golf club heads; however, higher fidelity models needed to be created and validated for this concept. There is a need for more accurate models for this concept to further investigate its performance benefits. Performance is measured in terms of impact efficiency of the ball and head and is referred to as coefficient of restitution (COR). COR is affected by the dynamic effective face stiffness and mass properties of the club. This thesis creates and validates high-fidelity, non-linear, dynamic finite element models for the tension-element …

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Modeling The Mechanical Effects Of Liquid Mediated Adhesion Between The Human Vocal Folds, Gifford Zach Decker Jul 2006

Modeling The Mechanical Effects Of Liquid Mediated Adhesion Between The Human Vocal Folds, Gifford Zach Decker

Theses and Dissertations

The vocal folds are a complex self-oscillating biological system. In the current research, an equation was developed to model viscous adhesion forces that occur when the collision of the vocal folds results in the formation of a liquid bridge. The adhesion equation was validated using experimental data, and simplified to a one-dimensional approximation with an included correction factor that adjusted the predicted pressure in situations where the one-dimensional approximation was invalid. A non-oscillating vocal fold model with a modeled liquid bridge was used to study stress resulting from viscous adhesion. The vertical normal stress magnitude ranged from about 80 to …

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Contractor Variability In Construction Of Cement Treated Base Layers, Maile Anne Rogers Jul 2006

Contractor Variability In Construction Of Cement Treated Base Layers, Maile Anne Rogers

Theses and Dissertations

The primary purposes of this research were to identify construction factors most correlated to specific mechanical properties of cement-treated base (CTB) layers and to determine which construction factors exhibit comparatively high variability within individual construction sections of the two pavement reconstruction projects included in this study. In addition, differences between construction sections tested in this research were evaluated. The research focused on the construction of CTB layers in two pavement reconstruction projects in northern Utah, one along Interstate 84 (I-84) near Morgan and one along U.S. Highway 91 (US-91) near Richmond. The significant predictor variables associated with California bearing ratio …

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A Solution For Commodity Field Hauling With Self-Unloading Semi-Trailers, Lee Pagens Wilkerson Jul 2006

A Solution For Commodity Field Hauling With Self-Unloading Semi-Trailers, Lee Pagens Wilkerson

Theses and Dissertations

Commodity hauling of bulk goods is a growing enterprise that has expanded from hauling agricultural products to hauling many other bulk products. Commodity trailers are used to haul agricultural products from storage facilities to processing plants. These trailers are designed for highway use but are frequently required to work in field conditions as well. In many cases this environment overstresses these trailers and results in permanent irreparable damage. In addition to the structural problems of these trailers, the current systems for unloading the bulk produce from these trailers have serious inadequacies. While functional, the currently used chain and non-chain driven …

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Design Of A Linear Ultrasonic Piezoelectric Motor, Scott L. Sharp Jul 2006

Design Of A Linear Ultrasonic Piezoelectric Motor, Scott L. Sharp

Theses and Dissertations

A new geometrically unique ultrasonic motor (USM) was designed using finite element modeling (FEM). A USM operates by vibrating a drive tip in an elliptical motion while it is in periodic contact with a driven surface. Piezoelectric elements are used to create the elliptical motions and are driven near a resonant frequency to create the needed displacements for the motor to operate. An idea for a motor frame was conceived that consisted of an arch, a center ground, and two piezoelectric elements connected to the center ground. End caps were added between the frame and the piezoelectric elements to reduce …

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Development Of A Variational Part Model Using In-Process Dimensional Measurement Error, Shane A. Carlson Jun 2006

Development Of A Variational Part Model Using In-Process Dimensional Measurement Error, Shane A. Carlson

Theses and Dissertations

To improve the geometric accuracy of CNC machined parts, dynamic machining errors due to on-line disturbances (tool deflection, tool wear, heat deformation, etc.) should be accounted for in some manner. Unless these on-line disturbances are properly handled, it is obvious that a high degree of geometric accuracy is difficult to achieve. Many attempts have been made to compensate for these on-line disturbances such as the development of engineering models; however, the models are not adequate enough for reflecting the real phenomenon and are dependent on continuous process monitoring using a variety of sensors. Closed-loop process control is a scheme for …

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Compliant Mechanism Suspensions, Timothy Melvin Allred Jun 2006

Compliant Mechanism Suspensions, Timothy Melvin Allred

Theses and Dissertations

This thesis has explored the use of compliant mechanisms in vehicle suspension systems, specifically where a compliant mechanism acts as part of the wheel locating mechanism and as the energy storage element. A compliant mechanism has the potential of reducing part count, joints, and manufacturing and assembly costs of a suspension system. Fatigue failure has been found to be a limiting design constraint which competes with space and weight constraints. Controlling wheel motion in response to control forces has also been shown to be an important functional requirement for a compliant suspension system. Vehicle applications that are best suited for …

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Vector Field Path Following For Small Unmanned Aerial Vehicles, Derek R. Nelson, D. Blake Barber, Timothy W. Mclain, Randal W. Beard Jun 2006

Vector Field Path Following For Small Unmanned Aerial Vehicles, Derek R. Nelson, D. Blake Barber, Timothy W. Mclain, Randal W. Beard

Faculty Publications

This paper presents a new method for unmanned aerial vehicle path following using vector fields to represent desired ground track headings to direct the vehicle onto the desired path. The key feature of this approach is that ground track heading error and lateral following error approach zero asymptotically even in the presence of constant wind disturbances. Methods for following straight-line and circularorbit paths, as well as combinations of straight lines and arcs, are presented. Experimental results validate the effectiveness of this path following approach for small air vehicles flying in high-wind conditions.

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Vision-Based Target Localization From A Fixed-Wing Miniature Air Vehicle, Joshua D. Redding, Timothy W. Mclain, Randal W. Beard, Clark N. Taylor Jun 2006

Vision-Based Target Localization From A Fixed-Wing Miniature Air Vehicle, Joshua D. Redding, Timothy W. Mclain, Randal W. Beard, Clark N. Taylor

Faculty Publications

This paper presents a method for localizing a ground-based object when imaged from a small fixed-wing unmanned aerial vehicle (UAV). Using the pixel location of the target in an image, with measurements of UAV position and attitude, and camera pose angles, the target is localized in world coordinates. This paper presents a study of possible error sources and localization sensitivities to each source. The localization method has been implemented and experimental results are presented demonstrating the localization of a target to within 11 m of its known location.

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An Xyz Micromanipulator With Three Translational Degrees Of Freedom, Kimberly A. Jensen, Craig P. Lusk, Larry L. Howell May 2006

An Xyz Micromanipulator With Three Translational Degrees Of Freedom, Kimberly A. Jensen, Craig P. Lusk, Larry L. Howell

Faculty Publications

This paper introduces a three degree of freedom XYZ Micromanipulator (XYZM) that is fabricated in the x-y plane and positions components in the x, y, and z directions using three independent linear inputs. The mechanism positions components on a platform using three legs, each composed of a slider mechanism and a parallelogram mechanism.

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Forest Fire Monitoring Using Multiple Unmanned Air Vehicles, Timothy Mclain, Randal W. Beard, Ryan S. Holt, Joseph W. Egbert, Justin M. Bradley, Clark N. Taylor Apr 2006

Forest Fire Monitoring Using Multiple Unmanned Air Vehicles, Timothy Mclain, Randal W. Beard, Ryan S. Holt, Joseph W. Egbert, Justin M. Bradley, Clark N. Taylor

Faculty Publications

The ability to gather and process information on the condition of forest fires is essential to fighting the fires in a cost-effective, safe, and efficient manner. While high-altitude, long-endurance (HALE) unmanned air vehicles (UAVs) are currently used for fire surveillance; they are an expensive and scarce resource. As a proposed alternative, low-altitude, short-endurance (LASE) UAVs offer lower costs, quicker response times, and high- resolution information. In recent years, advances in solid-state sensor and autopilot technology have made LASE UAVs a feasible alternative. This paper overviews a current research project conducted by Brigham Young University and NASA Ames. In the project, …

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The Storage Of Parametric Data In Product Lifecycle Management Systems, Jonathan Gary Lund Mar 2006

The Storage Of Parametric Data In Product Lifecycle Management Systems, Jonathan Gary Lund

Theses and Dissertations

Product development companies are continually seeking methods to increase efficiency while maintaining quality. Distributed development is also more important than ever before as industries globalize. These forces have driven firms to adopt formal data management practices that allow groups and individuals to work from singular, centralized data source that are secure, reliable, and support collaboration. This thesis proposes a methodology to leverage globalized infrastructures for the efficient storage of product variations. The methodology is proved through a working prototype using the market leader in Product Lifecycle Management (PLM) systems, Teamcenter Engineering. First, paradigms are set forth for the storage of …

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Development Of A Strain Energy Storage Mechanism Using Tension Elements To Enhance Golf Club Performance, Marc A. Whitezell Mar 2006

Development Of A Strain Energy Storage Mechanism Using Tension Elements To Enhance Golf Club Performance, Marc A. Whitezell

Theses and Dissertations

The development of current golf club designs has followed an evolutionary process starting with the original wooden heads of a hundred years ago, to the thin-walled, hollow body titanium heads of today. Current designs utilize what has become known as the trampoline effect to increase the efficiency of the ball-club impact, which has a number of limiting factors that restrict clubhead performance. These limitations provided the motivation for this research to explore new mechanisms by which the efficiency of the ball club impact could be increased. In particular this research focuses on the development of compliant mechanisms to increase club …

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Human Interfaces For Cooperative Control Of Multiple Vehicle Systems, Jisang Sun Mar 2006

Human Interfaces For Cooperative Control Of Multiple Vehicle Systems, Jisang Sun

Theses and Dissertations

This thesis presents a human interface which helps users efficiently allocate multiple unmanned ground vehicles (UGVs) cooperating to accomplish timing-sensitive missions in an urban environment. The urban environment consists of obstacles and a hazardous region. The obstacles represent a "no-go zone" while the hazardous region represents a high-risk area. The main object of this problem is to minimize the team operational cost while satisfying timing constraints. Operational costs for individual vehicles are based on risk and power consumption, and are calculated using path length and vehicle velocity. In this thesis, three types of timing constraints are considered: simultaneous arrival, tight …

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Automated Manipulation For The Lotus Filament Winding Process, Jeffrey V. Anderson Mar 2006

Automated Manipulation For The Lotus Filament Winding Process, Jeffrey V. Anderson

Theses and Dissertations

The filament-winding process produces quality consistent composite parts for many industries. Filament winding allows for consistent quality parts by automating the winding process. A recent development of filament winding is the Lotus process. The Lotus process reverses conventional filament winding by leaving the mandrel stationary and winding composite fiber around the mandrel. The automated Lotus filament-winding machine is controlled by four-axis control manipulating the Lotus ring around a fixed mandrel. This allows Lotus filament winding to wind parts that do not have a linear axis. Lotus filament winding is in its early stages of development. As a second step in …

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Flight Testing Small, Electric Powered Unmanned Aerial Vehicles, Jon N. Ostler Mar 2006

Flight Testing Small, Electric Powered Unmanned Aerial Vehicles, Jon N. Ostler

Theses and Dissertations

Flight testing methods are developed to find the drag polar for small UAVs powered by electric motors with fixed-pitch propellers. Wind tunnel testing was used to characterize the propeller-motor efficiency. The drag polar was constructed using data from flight tests. The proposed methods were implemented for a small UAV. A drag polar was found for this aircraft with CDo equal to 0.021, K1 equal to 0.229, and K2 equal to -0.056. This drag polar was then used to find the following performance parameters; maximum velocity, minimum velocity, velocity for maximum range, velocity for maximum endurance, maximum rate of climb, maximum …

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Analysis Of Viscous Drag Reduction And Thermal Transport Effects For Microengineered Ultrahydrophobic Surfaces, Jason W. Davies Mar 2006

Analysis Of Viscous Drag Reduction And Thermal Transport Effects For Microengineered Ultrahydrophobic Surfaces, Jason W. Davies

Theses and Dissertations

One approach recently proposed for reducing the frictional resistance to liquid flow in microchannels is the patterning of micro-ribs and cavities on the channel walls. When treated with a hydrophobic coating, the liquid flowing in the microchannel wets only the top surfaces of the ribs, and does not penetrate into the cavities, provided the pressure is not too high. The net result is a reduction in the surface contact area between channel walls and the flowing liquid. For micro-ribs and cavities that are aligned normal to the channel axis (principal flow direction), these micropatterns form a repeating, periodic structure. This …

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Two Dimensional Friction Stir Welding Model With Experimental Validation, Charles Blake Owen Mar 2006

Two Dimensional Friction Stir Welding Model With Experimental Validation, Charles Blake Owen

Theses and Dissertations

The performance of a coupled viscoplastic model of FSW has been evaluated over a variety of tool RPMs and feed rates. Initial results suggested that further optimization of the material parameters and an additional ability to model the thermal recovery of the material would improve the overall performance of the model. Therefore, an experimental/numeric approach was taken to improve and quantitatively compare the performance of the model based upon the thermal profile of the workpiece. First, an experimental method for obtaining real-time temperature measurements during Friction Stir Processing (FSP) of 304L Stainless Steel was developed. The focus of the method …

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Automatic Geometric Data Migration Throughout Views Of A Model Fidelity Family, Hans L. Soderquist Mar 2006

Automatic Geometric Data Migration Throughout Views Of A Model Fidelity Family, Hans L. Soderquist

Theses and Dissertations

Changes in geometric model parameters are constant throughout the design process. Each group in an organization needs different model information at varying times during the design process. As a result many different models of the same part or assembly arise for the needs and use of each group in each design phase (from conceptual design to full product definition). When one group makes changes to a model, those changes need to be reflected in all of the models which describe the product in all groups and design phases in order for those changes to be verified against all design criteria …

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Learning Real-Time A* Path Planner For Unmanned Air Vehicle Target Sensing, Jason K. Howlett, Timothy W. Mclain, Michael A. Goodrich Mar 2006

Learning Real-Time A* Path Planner For Unmanned Air Vehicle Target Sensing, Jason K. Howlett, Timothy W. Mclain, Michael A. Goodrich

Faculty Publications

This paper presents a path planner for sensing closely-spaced targets from a fixed-wing unmanned air vehicle (UAV) having a specified sensor footprint. The planner is based on the learning real-time A* (LRTA*) search algorithm and produces dynamically feasible paths that accomplish the sensing objectives in the shortest possible distance. A tree of candidate paths that span the area of interest is created by assembling primitive turn and straight sections of a specified step size in a sequential fashion from the starting position of the UAV. An LRTA* search of the tree produces feasible paths any time during its execution and …

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Piezoresistive Feedback For Decreased Response Time Of Mems Thermal Actuators, Robert K. Messenger, Timothy W. Mclain, Larry L. Howell Mar 2006

Piezoresistive Feedback For Decreased Response Time Of Mems Thermal Actuators, Robert K. Messenger, Timothy W. Mclain, Larry L. Howell

Faculty Publications

Feedback control is commonly used in positioning systems to improve dynamic response, disturbance rejection, accuracy, and repeatability. Similar benefits can be expected for microelectromechanical systems (MEMS) that are used for positioning applications. Sensing at the micro level poses significant challenges. Most of these challenges are associated with the small size of the devices and the small motions and forces which are of interest. In many situations, applying the macro system paradigm, where the sensor is a component that is added to the system, leads to unacceptable results. At the macro level, sensors are typically small relative to the systems they …

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Variation Analysis Of Involute Spline Tooth Contact, Brian J. De Caires Feb 2006

Variation Analysis Of Involute Spline Tooth Contact, Brian J. De Caires

Theses and Dissertations

The purpose of this thesis is to provide an in-depth understanding of tooth engagement in splined couplings based on variations in clearances between mating teeth. It is standard practice to assume that 25-50% of the total spline teeth in a coupling are engaged due to variations from manufacture. Based on the assumed number of teeth engaged, the load capability of a splined coupling is determined. However, due to the variations in tooth geometry from manufacuture, the number of teeth actually engaged is dependent on the applied load and the tooth errors. The variations result in sequential tooth engagement with increasing …

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Settling-Time Improvements In Positioning Machines Subject To Nonlinear Friction Using Adaptive Impulse Control, Tim Hakala Jan 2006

Settling-Time Improvements In Positioning Machines Subject To Nonlinear Friction Using Adaptive Impulse Control, Tim Hakala

Theses and Dissertations

A new method of adaptive impulse control is developed to precisely and quickly control the position of machine components subject to friction. Friction dominates the forces affecting fine positioning dynamics. Friction can depend on payload, velocity, step size, path, initial position, temperature, and other variables. Control problems such as steady-state error and limit cycles often arise when applying conventional control techniques to the position control problem. Studies in the last few decades have shown that impulsive control can produce repeatable displacements as small as ten nanometers without limit cycles or steady-state error in machines subject to dry sliding friction. These …

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Remote Terrain Navigation For Unmanned Air Vehicles, Stephen R. Griffiths Jan 2006

Remote Terrain Navigation For Unmanned Air Vehicles, Stephen R. Griffiths

Theses and Dissertations

There are many applications for which small unmanned aerial vehicles (SUAVs) are well suited, including surveillance, reconnaissance, search and rescue, convoy support, and short-range low-altitude perimeter patrol missions. As technologies for microcontrollers and small sensors have improved, so have the capabilities of SUAVs. These improvements in SUAV performance increase the possibility for hazardous missions through mountainous and urban terrain in the successful completion of many of these missions. The focus of this research was on remote terrain navigation and the issues faced when dealing with limited onboard processing and limited payload and power capabilities. Additional challenges associated with canyon and …

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Lattice-Based Structures For Studying Percolation In Two-Dimensional Grain Networks, Brent L. Adams, John A. Basinger, David T. Fullwood Jan 2006

Lattice-Based Structures For Studying Percolation In Two-Dimensional Grain Networks, Brent L. Adams, John A. Basinger, David T. Fullwood

Faculty Publications

This work was supported primarily by the MRSEC program of the National Science Foundation under DMR-0079996. The applicability of standard lattice percolation models to a random 2-D grain structure is explored. A random network based on the triangle lattice is proposed as a more appropriate model, and results in a higher percolation threshold (0.711 compared with 0.653 for the standard hexagonal lattice). The triple junction constraint inherent in grain boundary structures is subsequently applied to the new network. This results in a lowering of the percolation threshold to 0.686; this is opposite to its effect on the standard hexagonal lattice. …

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Robust Design And Model Validation Of Nonlinear Compliant, Michael S. Baker, Larry Howell, Jonathan W. Walker Jan 2006

Robust Design And Model Validation Of Nonlinear Compliant, Michael S. Baker, Larry Howell, Jonathan W. Walker

Faculty Publications

Although the use of compliance or elastic flexibility in microelectromechanical systems (MEMS) helps eliminate friction, wear, and backlash, compliant MEMS are known to be sensitive to variations in material properties and feature geometry, resulting in large uncertainties in performance. This paper proposes an approach for design stage uncertainty analysis, model validation, and robust optimization of nonlinear MEMS to account for critical process uncertainties including residual stress, layer thicknesses, edge bias, and material stiffness. A fully compliant bistable micromechanism (FCBM) is used as an example, demonstrating that the approach can be used to handle complex devices involving nonlinear finite element models. …

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Extending Taylor Plasticity Theory For Microscopic Slip Transfer Conditions, Brent L. Adams, Ray M. Merrill, John A. Basinger, Bassem S. El-Dasher Jan 2006

Extending Taylor Plasticity Theory For Microscopic Slip Transfer Conditions, Brent L. Adams, Ray M. Merrill, John A. Basinger, Bassem S. El-Dasher

Faculty Publications

This work was supported primarily by the MRSEC Program of the National Science Foundation under DMR-0079996. Most studies in crystal plasticity are based upon Taylor's original 1938 work. Within Taylor's framework the dependence of yield strength on microstructure, beyond lattice orientation, is carried within the critical resolved shear stress for slip. Thus, as the grain size decreases, the critical resolved shear stress is required to increase. This increase in critical resolved shear stress is applied, uniformly across the entire interior of the slipping grains according to the basic assumption of the model (uniform plastic strain or strain rate). It is …

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Grain Boundary Property Determination Through Measurement Of Triple Junction Geometry And Crystallography, Brent L. Adams, D. Casasent, M. Demirel, Bassem S. El-Dasher, D. Kinderlehrer, C. Liu, I. Livshits, F. Manolache, D. Mason, A. Morawiec, W. W. Mullins, S. Ozdemir, Gregory S. Rohrer, Anthony D. Rollett, David M. Saylor, Shlomo Ta'asan, A. Talukder, Chialin T. Wu, C. C. Yang, W. Yang Jan 2006

Grain Boundary Property Determination Through Measurement Of Triple Junction Geometry And Crystallography, Brent L. Adams, D. Casasent, M. Demirel, Bassem S. El-Dasher, D. Kinderlehrer, C. Liu, I. Livshits, F. Manolache, D. Mason, A. Morawiec, W. W. Mullins, S. Ozdemir, Gregory S. Rohrer, Anthony D. Rollett, David M. Saylor, Shlomo Ta'asan, A. Talukder, Chialin T. Wu, C. C. Yang, W. Yang

Faculty Publications

This work was supported primarily by the MRSEC program of the National Science Foundation under Award Number DMR-0079996. Microstructure controls the properties of most useful materials. Thus an ability to control microstructure through the processing of materials is a key to optimization of materials performance. Most materials are polycrystalline and their grain structure is a very important aspect of their microstructure. Thanks to their complexity there is a great variety of grain boundary types even in relatively isotropic materials such as the cubic metals. Simply describing the crystallography requires five (macroscopic) parameters (e.g. disorientation and inclination). Evidently, acquiring a knowledge …

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