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 …

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 …

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 …

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 …

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 …

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 …

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 …

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 …

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 …

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 …

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 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 …

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 …

Uav As A Service: Providing On-Demand Access And On-The-Fly Retasking Of Multi-Tenant Uavs Using Cloud Services, Justin Yapp

Doctoral Dissertations and Master's Theses

As commercial roles for Unmanned Aerial Vehicles (UAVs) become more well-defined and demand for the services provided by them increases, UAVs rely more on new cloud computing services and co-operative coordination to provide mission planning, control, tracking and data processing. We present UAV as a Service (UAVaaS) framework, which brings features commonly found in traditional cloud services, such as Infrastructure, Platform, and Software as a Service, to the domain of UAVs. Our work aims to conceptualize and design UAVaaS for commercial applications. Specifically, a cloud-provided orchestration framework that allows multi-tenant UAVs to easily serve multiple heterogenous clients at once and …

2d Aeroacoustic Analysis Of Flow In The Flame Trench, Meghan Pokorski

Doctoral Dissertations and Master's Theses

We present here a methodology for using the commercial software ANSYSFLUENT to predict the acoustic field associated with Space-Launch System (SLS). We consider a two-dimensional model of flame deflector, and flame trench. The ANSYS code is then used to simulate the internal flow. Both the steady state case is considered along with other cases where the inflow has a harmonic component. A Ffowcs-Williams Hawking (FWH) surface is then constructed within the computational domain to use the computed flow fluctuations to obtain the acoustic field. The acoustic data was then compared to the experimental data.

When using the ANSYS code for …

Aerodynamic Trade Study Of Compound Helicopter Concepts, Julian Roche

Doctoral Dissertations and Master's Theses

The relative performance attributes of compound helicopter concepts have been examined, including their potential for meeting the requirements of several challenging mission profiles. For each concept, which included lift and/or propulsive compounding, a suite of aerodynamic performance models was developed using energy methods. In the case of a lift-compounded concept, an aerodynamic model representing the force interaction effects of the main rotor wake with the wing was also developed. Models of a conventional helicopter and of a tiltrotor were implemented as well, and the results used as a datum for comparison. In each case, the predictive capabilities of the model …

Aerodynamic And Structural Design Of A Winglet For Enhanced Performance Of A Business Jet, Nicolas El Haddad

Doctoral Dissertations and Master's Theses

The preliminary design of a winglet to improve the range and fuel burn of the Falcon 10 business jet is presented. Twelve candidate geometries were studied varying the cant angle and the span. The configuration offering the best compromise between induced drag reduction, profile drag increase and weight increase due to the winglet structure and necessary wing structural reinforcement was selected. More refined analysis was performed for that winglet with Reynolds averaged Navier-Stokes computational fluid dynamics and finite element analysis. Range and fuel burn were finally calculated for a typical mission using these refined results. The selected winglet, with a …

Aircraft De-Icing System Using Thermal Conductive Fibers, Min Soon Park

Doctoral Dissertations and Master's Theses

The accumulation of ice on the leading edges of aircraft wing poses complications for flight control as drag is increased with a tendency for higher relative turbulence over the wing. Pre-emptive and reactive ice removal techniques have been employed in the past by electromechanical, thermal, chemical and pneumatic methods. In this thesis, a carbon fiber fabric is utilized as a heating de-icer for composites aircraft wing surface structures. Two prototypes are constructed, tested to generate temperature profiles, and an appropriate heating voltage is selected for effective de-icing via distinct avenues of heating system configurations. The heat transfer efficiency of the …

Development Of An Exteroceptive Sensor Suite On Unmanned Surface Vessels For Real-Time Classification Of Navigational Markers, Christopher Lloyd Kennedy

Doctoral Dissertations and Master's Theses

This thesis presents the development of an exteroceptive sensor suite for real-time detection and classification of navigational markers on Unmanned Surface Vessels. Three sensors were used to complete this task: a 3D LIDAR and two visible light cameras. First, all LIDAR points were transformed from the sensor’s reference frame to the local frame using a Kalman filter to estimate instantaneous vehicle pose. Next, objects were chosen from the LIDAR data to be classified using either Multivariate Gaussian or Parzen Window Classifiers. Both produce 96% accuracy or better, however, multivariate Gaussian ran considerably faster than the Parzen and was simpler to …

Robust And Adaptive Nonlinear Control Of Limit Cycle Oscillations In Uavs 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 fight control of unmanned aerial vehicles (UAVs), and could potentially lead to structural damage and catastrophic failures. LCO can be described as vibrational motions in the pitching and plunging displacements of an aircraft wing. Even in low Reynolds number (low-Re) fight regimes, LCO can exceed the limiting boundary for safe UAV fight. Further, as practical considerations motivate the design of smaller, lighter weight UAVs, there is a growing need for UAV systems that do not require heavy mechanical actuators (e.g., ailerons). To address this, the use of synthetic …

Preliminary Design Of An Asteroid Hopping Mission, Michael D. Scheppa

Doctoral Dissertations and Master's Theses

In 2010, NASA announced that its new vision is to support private space launch operations. It is anticipated that this new direction will create the need for new and innovative ideas that push the current boundaries of space exploration and contain the promise of substantial gain, both in research and capital.

The purpose of the study is to plan and estimate the feasibility of a mission to visit a number of near Earth asteroids (NEAs). The mission would take place before the end of the 21st century, and would only use commercially available technology. Throughout the mission design process, while …

Development, Verification, And Future Applications Of A 3-Dof Entry And Descent Simulation Tool, Shaun Deacon

Master's Theses - Daytona Beach

With any space related mission, the unknown effects are often some of the most important design considerations. These effects must be accounted for in some fashion, and often lead to mission elements being centered around gathering information on the unknown.

It is the purpose of this research to develop and test a tool for simulation of entry, descent, and landing, (EDL) and to present a brief analysis of possible dispersion patterns related to autonomous radiosonde deployment on the surface of Mars.

The EDL simulation tool is written in Matlab. The aerodynamic information used by the tool is obtained with the …