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Articles 1 - 30 of 37
Full-Text Articles in Engineering
A Reduced Order Model Of The Celestial Icosahedron As The Substructure For A Lighter Than Air Vehicle, Torin C. Quick
A Reduced Order Model Of The Celestial Icosahedron As The Substructure For A Lighter Than Air Vehicle, Torin C. Quick
Theses and Dissertations
A finite element approach was used to investigate a novel reduced order model to determine the minimum structure dimensionality to support vacuum for a VLTAV. This modeling technique represented the individual segments of the substructure as curved beams with clamped radially-resisted boundary conditions. The full structure was then modeled as a bare structure and structure with skin to validate the results of the reduced order model. The beam geometry for the material Ultem 9085 was determined through this process leading to the 3-D printing of the structure. It was then experimentally tested under uniaxial compression complimented with a FEA model.
Cyber Risk Assessment And Scoring Model For Small Unmanned Aerial Vehicles, Dillon M. Pettit
Cyber Risk Assessment And Scoring Model For Small Unmanned Aerial Vehicles, Dillon M. Pettit
Theses and Dissertations
The commercial-off-the-shelf small Unmanned Aerial Vehicle (UAV) market is expanding rapidly in response to interest from hobbyists, commercial businesses, and military operators. The core commercial mission set directly relates to many current military requirements and strategies, with a priority on short range, low cost, real time aerial imaging, and limited modular payloads. These small vehicles present small radar cross sections, low heat signatures, and carry a variety of sensors and payloads. As with many new technologies, security seems secondary to the goal of reaching the market as soon as innovation is viable. Research indicates a growth in exploits and vulnerabilities …
Active Control Of A Morphing Wing Aircraft And Failure Analysis For System Reliability, Madison J. Montgomery
Active Control Of A Morphing Wing Aircraft And Failure Analysis For System Reliability, Madison J. Montgomery
Theses and Dissertations
A morphing wing aircraft has the ability to increase the efficiency of an aircraft by better optimizing lift and drag characteristics during a flight. A morphing wing UAV was designed and constructed by AFRL/RQVS and required a means of control and method of characterizing the performance of the aircraft through flight testing. This research presents the design and construction of a control system capable of adjusting the morphing wing shape based on pilot commands and current flight status. The control system was tested and improved following a flight test crash utilizing failure mode analysis.
Monocular Visual Odometry For Fixed-Wing Small Unmanned Aircraft Systems, Kyung M. Kim
Monocular Visual Odometry For Fixed-Wing Small Unmanned Aircraft Systems, Kyung M. Kim
Theses and Dissertations
The popularity of small unmanned aircraft systems (SUAS) has exploded in recent years and seen increasing use in both commercial and military sectors. A key interest area for the military is to develop autonomous capabilities for these systems, of which navigation is a fundamental problem. Current navigation solutions suffer from a heavy reliance on a Global Positioning System (GPS). This dependency presents a significant limitation for military applications since many operations are conducted in environments where GPS signals are degraded or actively denied. Therefore, alternative navigation solutions without GPS must be developed and visual methods are one of the most …
High Resolution Low-Bandwidth Real-Time Reconnaissance Using Structure From Motion With Planar Homography Estimation, Christian M.A. Arnold
High Resolution Low-Bandwidth Real-Time Reconnaissance Using Structure From Motion With Planar Homography Estimation, Christian M.A. Arnold
Theses and Dissertations
Aerial real-time surveillance exists in a paradigm balancing the constraints of delivering high quality data and transporting data quickly. Typically, to have more of one, sacrifices must be made to the other. This is true of the environment in which an Unmanned Aerial Vehicle (UAV) operates, where real-time communication may be done through a low-bandwidth satellite connection resulting in low-resolution data, and serves as the primary limiting factor in all intelligence operations. Through the use of efficient computer vision techniques, we propose a new Structure from Motion (SfM) method capable of compressing high-resolution data, and delivering that data in real-time. …
Comprehensive Study Of Study Of Optimal Synergetic Skip Entries With Dynamic Thrust Vectoring Control, Jeremiah M. Webb
Comprehensive Study Of Study Of Optimal Synergetic Skip Entries With Dynamic Thrust Vectoring Control, Jeremiah M. Webb
Theses and Dissertations
The atmospheric skip entry has been studied since London's presentation in 1962 describing a more fuel efficient means of altering the orbital inclination of satellites. Since London, research over the decades since has traversed many aspects of this field with varying degrees of success. The present research employs the use of modern optimal control software, complex dynamics with minor simplifications, and thrust vectoring to re-approach the aerocruise atmospheric skip entry. Using the aerodynamics of the X-34, the aerocruise problem is first compared to the un-powered aeroglide where it is shown that the aerocruise is capable of increasing the inclination change …
Passive Load Testing For Evaluation Of Electromechanical Actuators, Jeremiah R. Hoffman
Passive Load Testing For Evaluation Of Electromechanical Actuators, Jeremiah R. Hoffman
Theses and Dissertations
While aircraft control surfaces traditionally use hydraulic actuators, electromechanical actuators (EMAs) are interesting as they have potential to be lighter, lower maintenance, and more robust. However, EMAs require more research regarding force-fight characteristics, power requirements, performance specifications, and more. The Air Force Research Laboratory is conducting some of this research, and operates a test rig which provides a passive load to a pair of EMAs. This rig is designed for simple test profiles for investigating force-fight; if it could be used to represent actual flight profiles, the rig could accommodate a wider variety of tests. The focus of this project …
Stereo Vision: A Comparison Of Synthetic Imagery Vs. Real World Imagery For The Automated Aerial Refueling Problem, Nicholas J. Seydel
Stereo Vision: A Comparison Of Synthetic Imagery Vs. Real World Imagery For The Automated Aerial Refueling Problem, Nicholas J. Seydel
Theses and Dissertations
Missions using unmanned aerial vehicles have increased in the past decade. Currently, there is no way to refuel these aircraft. Accomplishing automated aerial refueling can be made possible using the stereo vision system on a tanker. Real world experiments for the automated aerial refueling problem are expensive and time consuming. Currently, simulations performed in a virtual world have shown promising results using computer vision. It is possible to use the virtual world as a substitute environment for the real world. This research compares the performance of stereo vision algorithms on synthetic and real world imagery.
Behavior Flexibility For Autonomous Unmanned Aerial Systems, Taylor B. Bodin
Behavior Flexibility For Autonomous Unmanned Aerial Systems, Taylor B. Bodin
Theses and Dissertations
Autonomous unmanned aerial systems (UAS) could supplement and eventually subsume a substantial portion of the mission set currently executed by remote pilots, making UAS more robust, responsive, and numerous than permitted by teleoperation alone. Unfortunately, the development of robust autonomous systems is difficult, costly, and time-consuming. Furthermore, the resulting systems often make little reuse of proven software components and offer limited adaptability for new tasks. This work presents a development platform for UAS which promotes behavioral flexibility. The platform incorporates the Unified Behavior Framework (a modular, extensible autonomy framework), the Robotic Operating System (a RSF), and PX4 (an open- source …
Effects Of Manufacturing Process Variables On Ultrasonic Testing In Electron Beam Melted Ti-6al-4v, Andrew D. Durkee
Effects Of Manufacturing Process Variables On Ultrasonic Testing In Electron Beam Melted Ti-6al-4v, Andrew D. Durkee
Theses and Dissertations
Further research on validating additive manufacturing production quality is required before the realization of direct print-to-fly application of critical components. This research examines the response of ultrasonic testing as a function of various manufacturing variables in electron beam melted samples of Ti-6Al-4V. Four dimensionally identical blocks with 6 spherical voids at varying depths were manufactured using different combinations of stock powder, edge treatments, and void melting. Scans were completed on two sides of each specimen with the transducer focused on the mid-plane. Additionally, one specimen was scanned 6 times, with the focal plane adjusted for each scan to match the …
Design, Buildup, And Testing Of A Radial Rotating Detonation Engine For A Compact Auxiliary Power Unit, Riley Huff
Design, Buildup, And Testing Of A Radial Rotating Detonation Engine For A Compact Auxiliary Power Unit, Riley Huff
Theses and Dissertations
Current power generators consume a large portion of the aircrafts usable volume and they are also extremely heavy for the amount of power that they can produce. Therefore, a need for compact, lightweight Auxiliary Power Units (APU) with high power density has arisen. A novel solution to this problem comes in the form of coupling a Rotating Detonation Engine (RDE) with a turbine generator. A new type of RDE referred to as the Radial Rotating Detonation Engine (RRDE) has been developed to fill this need. This project marks the first radial ow RDE successfully operated in the United States, and …
Analytical Determination Of A Helicopter Height Velocity Diagram, Michael J. Harris
Analytical Determination Of A Helicopter Height Velocity Diagram, Michael J. Harris
Theses and Dissertations
A helicopter height velocity (HV) diagram was analytically constructed using optimal control techniques. A three degree of freedom, point-mass, dynamic model was developed and validated with flight test data. An induced velocity calculation was incorporated which addressed the effects of vortex ring state. The problem was posed as an open final time, constrained initial state, constrained final state problem, with the objective function as a weighted sum of the initial altitude and quadratic controls. This formulation was solved using direct pseudo-spectral collocation and adaptive mesh refinement as implemented by the GPOPS-II® software suite. Proper adjustment of path constraints was crucial …
A Study Of The Hexakis Icosahedron Vacuum Lighter Than Air Vehicle And The Effects Of Air Evacuation On The Structural Integrity, Anthony A. Castello
A Study Of The Hexakis Icosahedron Vacuum Lighter Than Air Vehicle And The Effects Of Air Evacuation On The Structural Integrity, Anthony A. Castello
Theses and Dissertations
The research this paper focuses on is comparing the structural differences between the icosahedron and hexakis icosahedron frame and skin for use as a vacuum lighter than air vehicle (VLTAV), analyzing the stress concentrations in the hexakis icosahedron both with and without the skin, and finding the optimal location and size of the air evacuation method for creating the internal vacuum. Previous research to date has identified dynamic loading on the structure and optimization of the structure, but this will be the first research to analyze the manufacturing of the structure through the development of the air evacuation design. Findings …
Quasi-Static Nonlinear Analysis Of A Celestial Icosahedron Shaped Vacuum Lighter Than Air Vehicle, Kyle D. Moore
Quasi-Static Nonlinear Analysis Of A Celestial Icosahedron Shaped Vacuum Lighter Than Air Vehicle, Kyle D. Moore
Theses and Dissertations
Due to the many drawbacks associated with a traditional lighter than air vehicle (LTAV), there is a desire for a LTAV which generates lift from an internal vacuum. To date, two feasible designs (the icosahedron and the hexakis icosahedron) for this so called vacuum lighter than air vehicle (VLTAV) have been studied at the Air Force Institute of Technology (AFIT). This research looks to show the feasibility of a new design for a VLTAV, the celestial icosahedron. This research includes a boundary condition study which proves the symmetric nature of the celestial icosahedron's frame with laterally constrained and unconstrained vertices. …
Assessing The Reliability Of The B-1b Lancer Using Survival Analysis, Francisco J. Rodriguez
Assessing The Reliability Of The B-1b Lancer Using Survival Analysis, Francisco J. Rodriguez
Theses and Dissertations
During the 2017 posture statement to the US Senate Armed Services Committee, the Secretary of the Air Force and Chief of Staff of the Air Force stated the Air Force suffers from shrinking aircraft inventory, aging aircraft fleets, and flying beyond the expected service life. These trends are not an exception to the B-1B Lancer, which has been in service since 1986. Recently, the B-1B Lancer has maintained the lowest mission capable (MC) rates of 47.7 percent. The purpose of this research is to explore the failure rates of the B-1B Lancer using survival analysis that investigates the failure behavior …
Evaluating The Autonomous Flying Qualities Of A Simulated Variable Stability Aircraft, Ali M. Hamidani
Evaluating The Autonomous Flying Qualities Of A Simulated Variable Stability Aircraft, Ali M. Hamidani
Theses and Dissertations
Delivering communications from high altitudes, at airspeeds of just 30 knots, gathering data from active volcanoes and forming hurricanes, and collecting ISR over hostile territories, UAVs are at the ready to perform those missions that are too dull, dirty, or dangerous for manned aircraft. However, the proliferation of this new technology has its fair share of challenges. Over 460 DoD UAV mishaps have occurred since 2001, with almost half resulting in damages of $2M or more. One incident almost ended in fatalities, when a UAV, suffering from loss of control, collided with a C-130. That loss of control is what …
Dynamic Response Analysis Of An Icosahedron Shaped Lighter Than Air Vehicle, Lucas W. Just
Dynamic Response Analysis Of An Icosahedron Shaped Lighter Than Air Vehicle, Lucas W. Just
Theses and Dissertations
The creation of a lighter than air vehicle using an inner vacuum instead of a lifting gas is considered. Specifically, the icosahedron shape is investigated as a design that will enable the structure to achieve positive buoyancy while resisting collapse from the atmospheric pressure applied. This research analyzes the dynamic response characteristics of the design, and examines the accuracy of the finite element model used in previous research by conducting experimental testing. The techniques incorporated in the finite element model are confirmed based on the experimental results using a modal analysis. The experimental setup designed will allow future research on …
Performance Of A Small Internal Combustion Engine Using N-Heptane And Iso-Octane, Cary W. Wilson
Performance Of A Small Internal Combustion Engine Using N-Heptane And Iso-Octane, Cary W. Wilson
Theses and Dissertations
With the sustained interest in Unmanned Aircraft Systems (UAS) and Micro Air Vehicles (MAV), the military services have a real need for vehicles powered by an internal combustion (IC) engine that can run efficiently on heavy hydrocarbon fuels, especially JP-8 due to established logistics. This thesis concerns the results of running a two horsepower, 4-stroke, spark-ignition engine (FUJI BF34-EI) with both iso-Octane and n-Heptane. Results include the knocking characteristic of this engine with n-Heptane, a comparison of the brake specific fuel consumption (BSFC) of the two fuels in a factory delivered engine configuration with a 17x10 APC propeller loading, a …
Development Of A Flapping Wing Design Incorporating Shape Memory Alloy Actuation, Jeffrey A. Barrett
Development Of A Flapping Wing Design Incorporating Shape Memory Alloy Actuation, Jeffrey A. Barrett
Theses and Dissertations
This research sought to validate a proof of concept regarding shape memory alloy actuation of a flapping-wing blimp. Specimen wires were subjected to cyclic voltage at increasing frequencies to quantify expected strains. A laser vibrometer captured 2048 sample velocities during single contraction and elongation cycles, and the resulting samples were used to calculate displacements. Displacements were determined ten times for each specimen and frequency to compute averages. Subsequently, a circumventing frame was designed to encase a blimp envelope and provide support for a flapping motion actuation system. Contraction of shape memory wire translated force to the flapping mechanism via bellcranks, …
Monocular Vision Localization Using A Gimbaled Laser Range Sensor, Don J. Yates
Monocular Vision Localization Using A Gimbaled Laser Range Sensor, Don J. Yates
Theses and Dissertations
There have been great advances in recent years in the area of indoor navigation. Many of these new navigation systems rely on digital images to aid an inertial navigation estimates. The Air Force Institute of Technology (AFIT) has been conducting research in this area for a number of years. The image-aiding techniques are centered around tracking stationary features in order to improve inertial navigation estimates. Previous research has used stereo vision systems or terrain constraints with monocular systems to estimate feature locations. While these methods have shown good results, they do have drawbacks. First, as unmanned exploration vehicles become smaller …
A Structural Dynamic Analysis Of A Manduca Sexta Forewing, Travis W. Sims
A Structural Dynamic Analysis Of A Manduca Sexta Forewing, Travis W. Sims
Theses and Dissertations
Micro air vehicles (MAVs) are intended for future intelligence, surveillance, and reconnaissance use. To adequately fulfill a clandestine capacity, MAVs must operate in close proximity to their intended target without eliciting counter-observation. This objective, along with DARPA’s constraint of a sub-15 centimeter span, requires future MAVs to mimic insect appearance and flight characteristics. This thesis describes an experimental method for conducting a structural analysis of a Manduca Sexta (hawkmoth) forewing. Geometry is captured via computed tomography (CT), and frequency data is collected using laser vibrometry in air and vacuum. A finite element (FE) model is constructed using quadratic beams and …
Analysis Of Hybrid-Electric Propulsion System Designs For Small Unmanned Aircraft Systems, Ryan M. Hiserote
Analysis Of Hybrid-Electric Propulsion System Designs For Small Unmanned Aircraft Systems, Ryan M. Hiserote
Theses and Dissertations
Currently fielded electric-powered small unmanned aircraft systems (UAS) lack the endurance desired by warfighters, while their internal combustion engine (ICE) driven counterparts generate mission compromising acoustic and thermal signatures. Parallel hybrid-electric propulsion systems would meet the military’s needs by combining the advantages of hydrocarbon and electric power systems. Three distinct parallel hybrid-electric system designs, each with three unique battery discharging profiles, were analyzed and compared using a constrained static optimization formulation based upon traditional aircraft design equations. Each system combined an ICE sized for cruise speed with an electric motor sized for endurance speed. The nine hybrid variations were compared …
Dive Angle Sensitivity Analysis For Flight Test Safety And Efficiency, Matthew T. Schneider
Dive Angle Sensitivity Analysis For Flight Test Safety And Efficiency, Matthew T. Schneider
Theses and Dissertations
Flutter envelope expansion is one of the most critical types of developmental flight tests. The regions that present the most dangerous flight profiles are those test points in the negative PS realm of the flight envelope. These points develop into high-speed dives and require an accurate predictive model to prevent possible testing accidents. As a flight test is conducted, several conditions such as aircraft weight and ambient air temperature can change, causing a drastic shift in the excess power profiles resulting in significant alteration in the test conditions. Using a dive planning model, a number of parameters were analyzed to …
Conceptual Design Tool For Fuel-Cell Powered Micro Air Vehicles, Paul M. Hrad
Conceptual Design Tool For Fuel-Cell Powered Micro Air Vehicles, Paul M. Hrad
Theses and Dissertations
A conceptual design tool was built to explore power requirements of a hybrid-power system for Micro Air Vehicles (MAVs) comparable in size to the Cooper's Hawk. An inviscid aerodynamic code, Athena Vortex Lattice (AVL), and a motor-propeller analysis code, QPROP, provide overall lift, drag, and thrust data for power-required calculation as functions of many variables to include mass, platform geometry, altitude, velocity, and mission duration. Phoenix Technologies’ Model Center was used to integrate multi-disciplinary components that employ specific power and specific energy of two power sources to determine power system mass required for a designated mission. The tool simulated a …
Off-Design Analysis Of A High Bypass Turbofan Using A Pulsed Detonation Combustor, Caitlin R. Thorn
Off-Design Analysis Of A High Bypass Turbofan Using A Pulsed Detonation Combustor, Caitlin R. Thorn
Theses and Dissertations
Past research has indicated that implementation of a pulsed detonation combustor (PDC) into a high-bypass turbofan engine yields a more efficient engine at design conditions. It is proposed that performance gains can be made utilizing this hybrid engine off-design. A hybrid high-bypass turbofan engine with a PDC model was evaluated for a range of Mach numbers, altitudes, and fill fractions in the Numerical Propulsion System Simulation (NPSS). Results were compared to a conventional baseline high-bypass turbofan engine that shares the same architecture with the hybrid. The NPSS baseline engine was validated using the Aircraft Engine Design System (AEDsys) program and …
Experiments With Geometric Non-Linear Coupling For Analytical Validation, Jonathan D. Boston
Experiments With Geometric Non-Linear Coupling For Analytical Validation, Jonathan D. Boston
Theses and Dissertations
This study was focused on obtaining accurate experimental data for the validation of the geometrically exact beam theory from a series of experiments in which high quality surface shape and deflection data was collected. Many previous experiments have experienced issues with data collection or test articles which the researchers were unable to overcome. The test program was performed in two stages: qualification and joined-wing. The qualification stage validated the experimental procedures on simple 72 in long aluminum beams with 8 in x 0.5 in cross-sections. The joined-wing stage was the primary experiment focused on obtaining quality data for use in …
Laser Dot Projection Photogrammetry And Force Balance Measurement Techniques For Flapping Wing Micro Air Vehicles, David H. Curtis
Laser Dot Projection Photogrammetry And Force Balance Measurement Techniques For Flapping Wing Micro Air Vehicles, David H. Curtis
Theses and Dissertations
The purpose of this research was to develop testing methods capable of analyzing the performance of a miniature flapping-wing mechanism that can later be adapted to a flapping wing micro air vehicle (MAV). A previously designed and built flapping only mechanism was used for testing, while a previously designed flapping and pitch mechanism was fabricated utilizing an Objet Eden 500V 3-dimensional printer and its operation demonstrated. The flapping mechanism was mounted on a six component force balance. Force and moment data were collected for a variety of wing sets at different flapping frequencies. The testing was conducted using wings composed …
Evaluation Of An Opnet Model For Unmanned Aerial Vehicle Networks, Clifton M. Durham
Evaluation Of An Opnet Model For Unmanned Aerial Vehicle Networks, Clifton M. Durham
Theses and Dissertations
The concept of Unmanned Aerial Vehicles (UAVs) was first used as early as the American Civil War, when the North and the South unsuccessfully attempted to launch balloons with explosive devices. Since the American Civil War, the UAV concept has been used in all subsequent military operations. Over the last few years, there has been an explosion in the use of UAVs in military operations, as well as civilian and commercial applications. UAV Mobile Ad Hoc Networks (MANETs) are fast becoming essential to conducting Network-Centric Warfare (NCW). As of October 2006, coalition UAVs, exclusive of hand-launched systems, had flown almost …
Characterizing The Exhaust Plume Of The Three-Electrode Micro Pulsed Plasma Thrusters, Myeongkyo Seo
Characterizing The Exhaust Plume Of The Three-Electrode Micro Pulsed Plasma Thrusters, Myeongkyo Seo
Theses and Dissertations
Three-electrode micro-PPTs are a new version of two electrode micro-PPTs devices. Performance predictions and contamination expectations are essential characteristics needed by satellite designers. In order to focus on thruster specific impulse, thrust and efficiency, measuring the exhaust velocity or impulse bit and propellant consumption rate is essential. While this is not always possible to measure directly, focusing on the ejected mass from the PPT provides significant information allowing determination of these performance statistics. Specifically, focusing on exhaust angle distribution and velocity of the exhaust particles is the emphasis of this work. The results show that the three-electrode micro-PPT is more …
Probabilistic Estimation Of Rare Random Collisions In 3-Space, Timothy Holzmann
Probabilistic Estimation Of Rare Random Collisions In 3-Space, Timothy Holzmann
Theses and Dissertations
A study of risk assessment for artillery fire randomly colliding with fixed wing aircraft is presented. The research lends itself to a general study of collision models. Current models of object collisions fall under one of three categories: the historical model, the gas particle model, and the satellite model. These three vary in data requirements and mathematical representation of the impact event. The gas particle model is selected for its flexibility and robust estimation. However, current mathematical development in the literature does not include certain spatial and dynamic components necessary for a general encounter (collision) model. These are derived in …