Open Access. Powered by Scholars. Published by Universities.®
- Institution
- Keyword
-
- Compliant mechanisms (4)
- Adjustable autonomy (2)
- Black liquor (2)
- CAD (2)
- CAx (2)
-
- COR (2)
- Coefficient of restitution (2)
- Control (2)
- Design (2)
- Force (2)
- GUI (2)
- Graphical user interface (2)
- Large eddy simulation (2)
- MEMS (2)
- Microelectromechanical systems (2)
- Motor (2)
- PDG (2)
- Torque (2)
- UAV (2)
- 3-D (1)
- 304L stainless steel (1)
- AIC (1)
- ANC (1)
- Acceleration (1)
- Active (1)
- Actuator (1)
- Actuators (1)
- Adaptation (1)
- Adaptive (1)
- Adhesion (1)
Articles 31 - 47 of 47
Full-Text Articles in Entire DC Network
Human Interfaces For Cooperative Control Of Multiple Vehicle Systems, Jisang Sun
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 …
Automated Manipulation For The Lotus Filament Winding Process, Jeffrey V. Anderson
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 …
Flight Testing Small, Electric Powered Unmanned Aerial Vehicles, Jon N. Ostler
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 …
Analysis Of Viscous Drag Reduction And Thermal Transport Effects For Microengineered Ultrahydrophobic Surfaces, Jason W. Davies
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 …
Two Dimensional Friction Stir Welding Model With Experimental Validation, Charles Blake Owen
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 …
Characterization Of Stress In Gan-On-Sapphire Microelectromechanical Systems (Mems) Structures Using Micro-Raman Spectroscopy, Francisco E. Parada
Characterization Of Stress In Gan-On-Sapphire Microelectromechanical Systems (Mems) Structures Using Micro-Raman Spectroscopy, Francisco E. Parada
Theses and Dissertations
Micro-Raman (µRaman) spectroscopy is an efficient, non-destructive technique widely used to determine the quality of semiconductor materials and microelectromechanical systems. This work characterizes the stress distribution in wurtzite gallium nitride grown on c-plane sapphire substrates by molecular beam epitaxy. This wide bandgap semiconductor material is being considered by the Air Force Research Laboratory for the fabrication of shock-hardened MEMS accelerometers. µRaman spectroscopy is particularly useful for stress characterization because of its ability to measure the spectral shifts in Raman peaks in a material, and correlate those shifts to stress and strain. The spectral peak shift as a function of stress, …
Automatic Geometric Data Migration Throughout Views Of A Model Fidelity Family, Hans L. Soderquist
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 …
Design, Build And Validation Of A Small-Scale Combustion Chamber Testing Facility, Eric R. Dittman
Design, Build And Validation Of A Small-Scale Combustion Chamber Testing Facility, Eric R. Dittman
Theses and Dissertations
This study investigated the design parameters necessary for the construction and use of a testing facility built to test the combustor section of engines. User inputs were acquired by interview and used in the decisions made in arrangement of pieces of machinery and how different systems were to interact. The design was then carried out as the various parts of the facility were built and installed. Software was designed which controlled the different parts of the combustion process and monitored the different products of combustion as well as the properties of the air and fuel used in the combustion. These …
Inertia Measurement And Dynamic Stability Analysis Of A Radio-Controlled Joined-Wing Aircraft, William A. Mcclelland
Inertia Measurement And Dynamic Stability Analysis Of A Radio-Controlled Joined-Wing Aircraft, William A. Mcclelland
Theses and Dissertations
Dynamic stability and stall during steady level turns were examined for VA-1, a joined-wing flight demonstrator aircraft. Configurations with a lower vertical tail and fairings over the main landing gear were compared with a recommendation on the combination had the best drag and dynamic stability characteristics. The dynamic stability analysis was broken into four key parts: a twist test experimentally measured mass moments of inertia, a panel method was used to find non-dimensional stability derivatives, lateral and longitudinal state space models estimated dynamic stability characteristics and handling quality levels were evaluated using a Cooper-Harper based rating system. VA-1 was found …
Power-Scavenging Mems Robots, Daniel J. Denninghoff
Power-Scavenging Mems Robots, Daniel J. Denninghoff
Theses and Dissertations
This thesis includes the design, modeling, and testing of novel, power-scavenging, biologically inspired MEMS microrobots. Over one hundred 500-μm and 990-μm microrobots with two, four, and eight wings were designed, fabricated, characterized. These microrobots constitute the smallest documented attempt at powered flight. Each microrobot wing is comprised of downward-deflecting, laser-powered thermal actuators made of gold and polysilicon; the microrobots were fabricated in PolyMUMPs® (Polysilicon Multi-User MEMS Processes). Characterization results of the microrobots illustrate how wing-tip deflection can be maximized by optimizing the gold-topolysilicon ratio as well as the dimensions of the actuator-wings. From these results, an optimum actuator-wing configuration was …
Microelectromechanical Systems (Mems) Interrupter For Safe And Arm Devices, Steven S. Mink
Microelectromechanical Systems (Mems) Interrupter For Safe And Arm Devices, Steven S. Mink
Theses and Dissertations
This thesis addresses the development of a new micro-scale interrupter mechanism for a safe and arm device used in modern weapon systems. The interrupter mechanism often consists of a physical barrier that prevents an initial source of energy, in an explosive train, from being transferred to subsequent charges. In general, when the physical barrier is removed, the weapon is considered armed, and the charge is allowed to propagate. Several issues facing current safe and arm devices systems are the shrinking industrial base for manufacturing these devices and the desire for modern safe and arm devices to be compatible with next …
Alleviation Of Buffet-Induced Vibration Using Piezoelectric Actuators, Shawn D. Morganstern
Alleviation Of Buffet-Induced Vibration Using Piezoelectric Actuators, Shawn D. Morganstern
Theses and Dissertations
Buffet-induced vibration has been problematic for aircraft structures for many years. The F-16 ventral fin, while prone to these effects, lends itself well to the evaluation of modern active structural and flow control technologies. The objective of this research was to determine the most critical natural modes of vibration for the F-16 ventral fin and design piezoelectric actuators capable of reducing buffet-induced ventral fin vibration. A finite element model (FEM) for the fin was developed, tuned and optimized to closely match published modal frequencies. Piezoelectric actuator patches were designed using the strain characteristics of the FEM and integrated into the …
Optimization Of A Low Heat Load Turbine Nozzle Guide Vane, Jamie J. Johnson
Optimization Of A Low Heat Load Turbine Nozzle Guide Vane, Jamie J. Johnson
Theses and Dissertations
Often turbomachinery airfoils are designed with aerodynamic performance foremost in mind rather than component durability. However, future aircraft systems require ever increasing levels of gas-turbine inlet temperature causing the durability and reliability of turbine components to be an ever more important design concern. As a result, the need to provide improved heat transfer prediction and optimization methods presents itself. Here, an effort to design an airfoil with minimized heat load is reported. First, a Reynolds-Averaged Navier-Stokes (RANS) flow solver was validated over different flow regimes as well as varying boundary conditions against extensive data available in literature published by the …
Variation Analysis Of Involute Spline Tooth Contact, Brian J. De Caires
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 …
Experimental Study On Two-Dimensional Propagating Edge Flames: Cold Flow Modeling And Flame Spread Rate Measurements, Marcos Villa-Gonzalez
Experimental Study On Two-Dimensional Propagating Edge Flames: Cold Flow Modeling And Flame Spread Rate Measurements, Marcos Villa-Gonzalez
Theses and Dissertations
This thesis presents the results of an experimental study on two-dimensional, planar propagating edge flames. The results were generated using a new apparatus in which a thin stream of gaseous fuel is injected into a low-speed laminar wind tunnel thereby forming a flammable layer along the centerline. The fuel injector consists of aluminum airfoil with a thin slot in its trailing edge, from which fuel is injected. After the initial stratified fuel/air layer is developed, a flame is ignited near the tunnel outlet, and the flame spreads against the incoming air, toward the fuel source. Experiments were conducted with methane …
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 …
Remote Terrain Navigation For Unmanned Air Vehicles, Stephen R. Griffiths
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 …