Engineering Commons^™

Implementation Of Path Planning Methods To Detect And Avoid Gps Signal Degradation In Urban Environments, Ayush Raminedi

Doctoral Dissertations and Master's Theses

In the modern world, various missions are being carried out under the assistance of autonomous flight vehicles due to their ability to operate in a wide range of flight conditions. Regardless, these autonomous vehicles are prone to GPS signal loss in urban environments due to obstructions that cause scintillation, multi-path, and shadowing. These effects that decrease the GPS functionality can deteriorate the accuracy of GPS positioning causing losses in signal tracking leading to a decrease in navigation performance. These effects are modeled into the simulation environment and are used as part of the path planning algorithm to provide better navigation …

Mitigating Engine Unstart In Scramjets With Porous Bleeders, Ryan Lindley

Doctoral Dissertations and Master's Theses

The effectiveness of porous bleeders in mitigating unstart phenomena and enhancing isolator effectiveness in a hypersonic scramjet was investigated. Through computational fluid dynamics simulations, the impact of porous bleeder design parameters such as pressure jump coefficient and bleeder size on isolator effectiveness and unstart prevention was evaluated. Results indicated that porous bleeders delayed flow separation and reduced adverse pressure gradients, thereby enhancing isolator performance. Additionally, porous bleeders demonstrated promising capabilities in preventing full unstart events and mitigating oscillatory unstart phenomena.

Modeling, Control, And Hardware Development Of A Thrust-Vector Coaxial Uav, Andrew North

Doctoral Dissertations and Master's Theses

This thesis introduces a unique thrust vector coaxial unmanned aerial vehicle (UAV) configuration and presents a comprehensive investigation encompassing dynamics modeling, hardware design, and controller development. Using the Newton-Euler method, a dynamic model for the UAV is derived to gain in-depth insights into its fundamental flight characteristics. A simple thrust model is formulated and modified by comparing it with data obtained from vehicle testing. The feasibility of manufacturing such a vehicle is assessed through the development of a hardware prototype. Finally, a linear state feedback controller is designed and evaluated using the non-linear dynamics model. The results demonstrate successful validation …

Small Unmanned Aircraft Systems: Operator Workload And Situation Awareness Utilizing First Person View Techniques, Ross Lucas Stephenson Jr

Doctoral Dissertations and Master's Theses

The small, unmanned aircraft systems (sUAS) sector within the aviation industry is experiencing unprecedented growth. However, the regulatory guidance for the safe integration of sUAS into the National Airspace System (NAS) has not kept pace with this technological growth within the market. Current regulatory limitations of line-of-sight operations may have an impact on the establishment of an equivalent level of safety for sUAS operations as maintained by manned aircraft. The focal point of the discussion of line-of-sight operations has been the ability of the sUAS pilot to see and avoid all obstacles and other aircraft in a safe and timely …

Loss Of Control In-Flight (Loc-I): A Mixed Methods Study Of Voluntary Versus Mandatory Reports From The United States Of America, Roger Lee

Doctoral Dissertations and Master's Theses

Loss of control in flight (LOC-I) is one of modern aviation’s three most prominent fatal accidents. In the United States, air accidents are mandatorily reported to and investigated by the National Transportation Safety Board (NTSB). Established in 1976, the Air Safety Reporting System (ASRS) is a voluntary safety reporting (VSR) system administered by the National Aeronautics and Space Administration (NASA). Over 1.7 million ASRS reports have been processed to date. While the NTSB system handles LOC-I accidents, less severe incidents may have been reported voluntarily through the ASRS.

Safety reporting has been deemed the most valuable activity and the centerpiece …

A Simulation Of The Impacts Of Climate Change On Civil Aircraft Takeoff Performance, Thomas D. Pellegrin

Doctoral Dissertations and Master's Theses

Climate change affects the near-surface environmental conditions that prevail at airports worldwide. Among these, air density and headwind speed are major determinants of takeoff performance, and their sensitivity to global warming carries potential operational and economic implications for the commercial air transport industry. Previous archival and prospective research observed a weakening in headwind strength and predicted an increase in near-surface temperatures, respectively, resulting in an increase in takeoff distances and weight restrictions. The main purpose of the present study was to update and generalize the extant prospective research using a more representative sample of worldwide airports, a wider range of …

On-Board Artificial Intelligence For Failure Detection And Safe Trajectory Generation, Eduardo Morillo

Doctoral Dissertations and Master's Theses

The use of autonomous flight vehicles has recently increased due to their versatility and capability of carrying out different type of missions in a wide range of flight conditions. Adequate commanded trajectory generation and modification, as well as high-performance trajectory tracking control laws have been an essential focus of researchers given that integration into the National Air Space (NAS) is becoming a primary need. However, the operational safety of these systems can be easily affected if abnormal flight conditions are present, thereby compromising the nominal bounds of design of the system's flight envelop and trajectory following. This thesis focuses on …

Assessment Of Iso-Ahola’S Theory Of Tourism Motivation On Willingness To Fly As A Point-To-Point Suborbital Space Tourist, Brian T. Musselman

Doctoral Dissertations and Master's Theses

Suborbital space tourism involves flight in an air vehicle to an altitude exceeding 100 kilometers (62 miles). This altitude is referred to as the Karman Line and the edge of space. Point-to-point space travel is transportation in an air vehicle where the vehicle flies around the earth in space to decrease the time to travel from one point on the earth’s surface to another point on the earth’s surface. The commercial space flight industry has a vision for point-to-point space travel.

The study aimed to assess the influence of the four dimensions of Iso-Ahola’s (1982) theory of tourism motivation on …

Understanding Unsteady Corner Separation Within Wing-Body Junction Flows, Paul G. Winner

Doctoral Dissertations and Master's Theses

Wing-body junction flows, formed at the interface between a wing and fuselage surface, are a complex, coupled, three-dimensional, turbulent flow field. This thesis focused on the unsteady corner separation that develops at the trailing edge of this wing-body junction under certain conditions. A NACA 0015 wing mounted on a flat plate at an angle of attack of 13°was used as the model junction flow field. The wing had an aspect ratio of 8 with a linear washout twist of 15°. The Reynolds number based on the wing chord was Re_c = 4.5 × 10⁵. Time-dependent stereoscopic particle …

Effect Of Spray Rails On Takeoff Performance Of Amphibian Aircraft, Soham Bahulekar

Doctoral Dissertations and Master's Theses

Amphibian aircraft have seen a rise in popularity in the recreational and utility sectors due to their ability to take off and land on both land and water, thus serving a myriad of purposes such as aerobatics, surveillance, and firefighting. The design of such seaplanes requires to be both aerodynamically and hydrodynamically efficient, especially during the takeoff phase. In the past, naval architects have implemented ways to make boats, yachts, and large ships more efficient; one of them being the addition of chine strips and spray rails on the hull. This thesis study explores the possibility of implementing spray rails …

A Patient Risk Minimization Model For Post-Disaster Medical Delivery Using Unmanned Aircraft Systems, Mark J. Simpson

Doctoral Dissertations and Master's Theses

The purpose of this research was to develop a novel routing model for delivery of medical supplies using unmanned aircraft systems, improving existing vehicle routing models by using patient risk as the primary minimization variable.

The vehicle routing problem is a subset of operational research that utilizes mathematical models to identify the most efficient route between sets of points. Routing studies using unmanned aircraft systems frequently minimize time, distance, or cost as the primary objective and are powerful decision-making tools for routine delivery operations. However, the fields of emergency triage and disaster response are focused on identifying patient injury severity …

Quasi-Static Structural Analysis Of An Experimental Aircraft Wing, Scott Bender

Doctoral Dissertations and Master's Theses

In this report, a quasi-static load analysis is conducted on an experimental light sport aircraft wing via a whiffletree bending test. This report will discuss the loads present on the aircraft during straight level flight at a speed of 82 knots equivalent air speed. Flight load calculations are described along with the design of the whiffletree and mounting structures utilized for applying the distributed point loads. Initial finite element analysis is performed on the wing structure to determine critical strain locations and optimal sensor distribution. Subsequent mechanical experimentations are performed using a bending test to measure the strain at critical …

Behavioral Intention Factors For Prescription Deliveries By Small Unmanned Aircraft In Rural Communities, Sarah M. Talley

Doctoral Dissertations and Master's Theses

Nearly half of the U.S. population regularly use and depend on prescription medications; however, pharmacy availability and access to pharmacy services are often lacking, particularly in rural communities. In an effort to meet local healthcare needs, delivery by sUAS is proposed to ensure the nearly 60 million rural residents have access to their prescription medications.

As an emerging technology with little research into home delivery applications, the successful implementation of sUAS for prescription medication delivery requires public acceptance and positive behavioral intention toward its use. At the time of the current research, no prior studies have specifically focused on the …

Active Control Of Coherent Structures In An Axisymmetric Jet, Michael Marques Goncalves

Doctoral Dissertations and Master's Theses

The primary objective of this work is to develop high-fidelity simulation model for jet noise control predictions and quantify the sound reduction when an external source frequency mode excitation is imposed on the jet flow. Whereas passive approaches using mixing devices, such as chevrons, have been shown to reduce low-frequency noise in jet engines, such approaches incur a performance penalty since they result in a reduced thrust. To avoid a performance penalty in reducing jet noise, the current work investigates a open-loop active noise control (ANC) system that utilizes a unsteady microjet actuator on the nozzle lip in the downstream …

A Reduced-Order Model Bi-Modal Excitation Of A Supersonic Planar Jet, Benjamin Malczewski

Doctoral Dissertations and Master's Theses

This work analytically and numerically examines the effects of bi-modal excitation on a Mach 1.5 heated planar jet. Starting with the Navier-Stokes equations, triple decomposition is applied to the flow components. A reduced order model is derived, turning the Navier-Stokes partial differential equations into a set of coupled ordinary differential equations, relating the momentum thickness and amplitudes of a fundamental and subharmonic mode to the streamwise location along the jet. Computational fluid dynamics data from the minor plane of a Mach 1.5 heated rectangular jet is used to verify a hyperbolic tangent profile for the mean flow at various streamwise …

Modeling Of A Hybrid-Electric System And Design Of Control Laws For Hybrid-Electric Urban Air Mobility Power Plants, Sohail Bin Salam Lahaji

Doctoral Dissertations and Master's Theses

Advanced Air Mobility (AAM) is an emerging market and technology in the aerospace industry. These systems are being developed to overcome traffic congestion. The current designs make use of Distributed Electric Propulsion (DEP): either fully electric or hybrid electric. The hybrid engine system consists of two power sources: prime movers, such as turbine engines, and batteries. The hybrid systems offer higher range and endurance compared with the existing fully electric systems. Hybrid-electric power generation systems for AAM have different mission requirements when compared to systems used in automobiles. Therefore, there is a particular need to model hybrid-electric systems and the …

Design And Flight-Path Simulation Of A Dynamic-Soaring Uav, Gladston Joseph

Doctoral Dissertations and Master's Theses

We address the development of a dynamic-soaring capable unmanned aerial vehicle (UAV) optimized for long-duration flight with no on-board power consumption. The UAV’s aerodynamic properties are captured with the integration of variable fidelity aerodynamic analyses. In addition to this, a 6 degree-of-freedom flight simulation environment is designed to include the effects of atmospheric wind conditions. A simple flight control system aids in the development of the dynamic soaring maneuver. A modular design paradigm is adopted for the aircraft dynamics model, which makes it conducive to use the same environment to simulate other aircraft models. Multiple wind-shear models are synthesized to …

Computational Investigation Of Perforated Plate Film Cooling Utilizing Conjugate Heat Transfer, Jonathan Sippel

Doctoral Dissertations and Master's Theses

The accuracy of modern state-of-practice computational fluid dynamics approaches in predicting the cooling effectiveness of a perforated plate film-cooling arrangement is evaluated in ANSYS Fluent. A numerical investigation is performed using the Reynolds Averaged Navier Stokes equations and compared to NASA Glenn’s available Turbulent Heat Flux 4 experimental measurements collected as a part of the Transformational Tools and Technologies Project. A multiphysics approach to model heat conduction through the solid geometry is shown to offer significant improvements in wall temperature and film effectiveness prediction accuracy over the standard adiabatic wall approach. Additionally, localized gradient-based grid adaption is analyzed using the …

The Effects Of Remotely Piloted Aircraft Command And Control Latency During Within-Visual-Range Air-To-Air Combat, David Thirtyacre

Doctoral Dissertations and Master's Theses

The type of military missions conducted by remotely piloted aircraft continues to expand into all facets of operations including air-to-air combat. While future within-visual-range air-to-air combat will be piloted by artificial intelligence, remotely piloted aircraft will likely first see combat. The purpose of this study was to quantify the effect of latency on one-versus-one, within-visual-range air-to-air combat success during both high-speed and low-speed engagements. The research employed a repeated-measures experimental design to test the various hypothesis associated with command and control latency. Participants experienced in air-to-air combat were subjected to various latency inputs during one-versus-one simulated combat using a virtual-reality …

Constrained Motion Analysis Of Spacecraft Trajectory In Restricted Three Body Problem, Harshkumar Patel

Doctoral Dissertations and Master's Theses

Due to the popularity of libration points, many satellites are being maintained on their desired trajectory. Indian space research organization has planned to launch the Aditya-L1 spacecraft to study about the Sun by 2021. James Webb Space Telescope has also been designed to observe deep space at L2 in the Sun-Earth system by 2021. The combined gravity of the Earth and the Sun keep satellite’s orbit locked at libration points. Though satellites enjoys an uninterrupted view of Sun and Earth all the time, they are affected by the solar radiation pressure (SRP) continuously. Due to the instability of collinear libration …

Three-Dimensional, Vision-Based Proportional Navigation For Uav Collision Avoidance, Guanhong Gao

Doctoral Dissertations and Master's Theses

As the number of potential applications for Unmanned Aerial Vehicles (UAVs) keeps rising steadily, the chances that these devices will operate in close proximity to static or dynamic obstacles also increases. Therefore, collision avoidance is an important challenge to overcome for Unmanned Aerial Vehicle operations. Electro-optical devices have several advantages such as light weight, low cost, low algorithm requirements with respect to computational power and possibly night vision capabilities. Therefore, vision-based Unmanned Aerial Vehicle collision avoidance has received considerable attention. Although much progress has been made in collision avoidance systems (CAS), most approaches are focused on two-dimensional environments. In order …

Fuel Efficient Control Design And Constrained Motion Analysis For Spacecraft Coulomb Formation In Elliptic Chief Orbits, Muhammad Wasif Memon

Doctoral Dissertations and Master's Theses

The use of Coulomb force has been analyzed in recent years to provide propulsion in space for various applications. Coulomb formation can also be utilized to make close formation spacecraft missions fuel efficient. In this study, the Coulomb formation of two craft is studied in elliptic chief orbits for two formation geometries. The first formation requires both spacecraft to be aligned along the nadir (radial) direction and the second formation requires both spacecraft to maintain a constant separation distance relative to each other while each spacecraft rotates freely on the surface of a sphere with the ratio of the radii …

Adaptive Learning Terrain Estimation For Unmanned Aerial Vehicle Applications, Pedro L. Vergara Garcia

Doctoral Dissertations and Master's Theses

For the past decade, terrain mapping research has focused on ground robots using occupancy grids and tree-like data structures, like Octomap and Quadtrees. Since flight vehicles have different constraints, ground-based terrain mapping research may not be directly applicable to the aerospace industry. To address this issue, Adaptive Learning Terrain Estimation algorithms have been developed with an aim towards aerospace applications. This thesis develops and tests Adaptive Learning Terrain Estimation algorithms using a custom test benchmark on representative aerospace cases: autonomous UAV landing and UAV flight through 3D urban environments. The fundamental objective of this thesis is to investigate the use …

Risk Mitigation For Low Latitude Ground-Based Augmentation System (Gbas) Precision Approach Operations, Richard Walter Cole

Doctoral Dissertations and Master's Theses

The ground-based augmentation system (GBAS) is a safety-critical system consisting of the hardware and software that augments the Global Positioning System (GPS) to provide precision approach and landing capability and is one of the navigational cornerstones of the International Civil Aviation Organization's (ICAO) global transition to space-based technologies. In low latitude regions, where the space-based augmentation system (SBAS) cannot provide adequate precision approach service due to large system errors induced by ionospheric delays, GBAS is the best option to provide the primary navigation function for the modernized global air traffic system. The purpose of the study was to identify patterns …

Development Of Robust Control Laws For Disturbance Rejection In Rotorcraft Uavs, Johannes Verberne

Doctoral Dissertations and Master's Theses

Inherent stability inside the flight envelope must be guaranteed in order to safely introduce private and commercial UAV systems into the national airspace. The rejection of unknown external wind disturbances offers a challenging task due to the limited available information about the unpredictable and turbulent characteristics of the wind. This thesis focuses on the design, development and implementation of robust control algorithms for disturbance rejection in rotorcraft UAVs. The main focus is the rejection of external disturbances caused by wind influences. Four control algorithms are developed in an effort to mitigate wind effects: baseline nonlinear dynamic inversion (NLDI), a wind …

Uncover The Power Of Multipath : Detecting Nlos Drones Using Low-Cost Wifi Devices, Ashok Vardhan Raja

Doctoral Dissertations and Master's Theses

In recent years, consumer UAV technology has seen considerable advances. Consumer UAVs have become an ideal vector for privacy invasions due to their affordability, size, maneuverability, and their ability to stream live high-quality video. There is considerable proliferation of drones in both civil and military domains. Hence it is critical to detect invading unmanned aerial vehicles (UAVs) or drones in a timely manner for both security and safeguarding privacy. Currently available solutions like active radar, video or acoustic sensors are very expensive (especially for individuals) and have considerable constraints (e.g., requiring visual line of sight).

Recent research on drone detection …

Design And Implementation Of Intelligent Guidance Algorithms For Uav Mission Protection, Karina Rivera

Doctoral Dissertations and Master's Theses

In recent years, the interest of investigating intelligent systems for Unmanned Aerial Vehicles (UAVs) have increased in popularity due to their large range of capabilities such as on-line obstacle avoidance, autonomy, search and rescue, fast prototyping and integration in the National Air Space (NAS). Many research efforts currently focus on system robustness against uncertainties but do not consider the probability of readjusting tasks based on the remaining resources to successfully complete the mission. In this thesis, an intelligent algorithm approach is proposed along with decision-making capabilities to enhance UAVs post-failure performance. This intelligent algorithm integrates a set of path planning …

Development Of A Small Unmanned Aerial Vehicle Longitudinal Model For Future Flutter Testing, Said S. Hamada

Doctoral Dissertations and Master's Theses

This thesis presents the system identification of the longitudinal motion of a small unmanned aerial vehicle with flexible characteristics. The unmanned aerial vehicle of study is an off-the-shelf aircraft with limited knowledge about the dynamic model. The first task in obtaining a model for flutter testing is determining the rigid body model. Specifically, this thesis will focus in the development of the aircraft and obtaining the longitudinal rigid body model. This involves the assembly and configuration of the avionics and sensors, performing experiments to determine mass and inertia properties and using software tools for aerodynamic analysis to get preliminary values …

Homography-Based State Estimation For Autonomous Exploration In Unknown Environments, Andres S. Chavez Armijos

Doctoral Dissertations and Master's Theses

This thesis presents the development of vision-based state estimation algorithms to enable a quadcopter UAV to navigate and explore a previously unknown GPS denied environment. These state estimation algorithms are based on tracked Speeded-Up Robust Features (SURF) points and the homography relationship that relates the camera motion to the locations of tracked planar feature points in the image plane. An extended Kalman filter implementation is developed to perform sensor fusion using measurements from an onboard inertial measurement unit (accelerometers and rate gyros) with vision-based measurements derived from the homography relationship. Therefore, the measurement update in the filter requires the processing …

Robust Nonlinear Estimation And Control Applications Using Synthetic Jet Actuators, Natalie Ramos Pedroza

Doctoral Dissertations and Master's Theses

Limit cycle oscillations (LCO), also known as utter, cause significant challenges in flight control of small unmanned aerial vehicles (SUAVs), and could potentially lead to structural damage and catastrophic failures. LCO can be described as vibrational motions in the rocking, pitching and plunging displacements of an aircraft wing. To address this, the use of synthetic jet actuators (SJAs) in UAV flight control systems is becoming popular as a practical alternative and to mechanical deflection surfaces.

Synthetic jet actuators are promising tools for LCO suppression systems in small UAVs due to their small size, ease of operation, and low cost. Uncertainties …