Engineering Commons^™

Simple Adaptive Delta Operator Aircraft Flight Control For Accommodation Of Loss Of Control Effectiveness, Alfredo Cano, Kenneth Sobel

Publications and Research

A new proof for stability of delta operator simple adaptive control is presented in terms of a set of Linear Matrix Inequalities (LMIs). The paper shows how to design a feedforward gain to satisfy the LMIs over a polytope of loss of control effectiveness failures. The MATLAB Robust Control Toolbox is used to find the feedforward gain with the smallest norm that satisfies the LMIs. Examples are presented of the F/A-18 aircraft and the Innovative Control Effectors (ICE) tailless aircraft that show the design of a feedforward gain for a loss of control effectiveness in any one control effector. The …

Nonlinear Flight Control Design Using Backstepping Methodology, Thanh Trung Tran

Mechanical & Aerospace Engineering Theses & Dissertations

The subject of nonlinear flight control design using backstepping control methodology is investigated in the dissertation research presented here. Control design methods based on nonlinear models of the dynamic system provide higher utility and versatility because the design model more closely matches the physical system behavior. Obtaining requisite model fidelity is only half of the overall design process, however. Design of the nonlinear control loops can lessen the effects of nonlinearity, or even exploit nonlinearity, to achieve higher levels of closed-loop stability, performance, and robustness. The goal of the research is to improve control quality for a general class of …

Long-Term Quantitative Study Of Wind-Tunnel Balance Calibrations Across Multiple Calibration Systems, Ryan James Callahan

Mechanical & Aerospace Engineering Theses & Dissertations

Internal strain-gauge balances are multi-dimensional force transducers widely employed in wind tunnels to obtain accurate aerodynamic force and moment data on an aircraft model. Balances are calibrated periodically to assure measurement accuracy. The calibration provides a mathematical model relating the forces applied to the balance and the output signal from the balance. Currently, there are multiple types of internal strain-gauge balances used in wind-tunnel testing as well as multiple methods by which balances are calibrated. Because of the differences in the hardware and methodologies used to calibrate a wind-tunnel balance, it is hard to quantify the differences seen between the …

Experimental Analysis Of Turbulent Structures And The Effects Of Non-Equilibrium On An Axial Vortex, Michael P. Thompson

Mechanical & Aerospace Engineering Theses & Dissertations

Examples of the axial vortex include, dust devils, trailing line aircraft wake vortices, and tornadoes. Some of these vortices can prove hazardous to individuals and property. This necessitates that studies be conducted to understand their structure and to attempt to develop mathematical models of the flow physics involved. A wide variety of experimental techniques have been used in the past to study the vortex, with flow visualization and hotwire anemometry being chosen for this experiment. There have been many inadequate mathematical models proposed in the past. The experimental results obtained were compared to the work of Ash, Zardadkhan and Zuckerwar …

Experimental Investigation Of Turbulent Structures And Non-Equilibrium Effects In Axial Wake Vortices Via Particle Image Velocimetry, Jeffry William Ely

Mechanical & Aerospace Engineering Theses & Dissertations

Vortices are a common phenomenon in fluid flows that arise as kinetic energy dissipates into heat via viscous interaction. They arise naturally at large scales in the form of dust devils, tornadoes, and as a counter-rotating vortex pair in the wake of aircraft. It is important to understand the conditions leading to their formation, their duration, and their dissipation in order to forecast or prevent undesirable effects. Among these deleterious effects is a decrease in safety of aircraft operations in the wake of other aircraft, an extremely common situation at airports around the world. A large number of mathematical models …

A Hybrid Position Feedback Controller For Bistable Structures, Mehmet R. Simsek

Mechanical & Aerospace Engineering Theses & Dissertations

Bistability is the property of structures showing the ability to attain two statically stable states. Due to dynamic and static advantages such as no energy demand at stable positions and providing higher deflections compared to a monostable structure, bistability may be appealing in control surface design for aircraft structures and load alleviation for wind turbine blades. The dynamics of bistable structures is nonlinear because of the snap-through occurring during the cross-well oscillation between two stable states. A new control strategy called hybrid position feedback control is developed based on the conventional positive position control to exploit linear dynamics of bistable …

Modeling Shock Waves Using Exponential Interpolation Functions With The Least-Squares Finite Element Method, Bradford Scott Smith Jr.

Mechanical & Aerospace Engineering Theses & Dissertations

The hypothesis of this research is that exponential interpolation functions will approximate fluid properties at shock waves with less error than polynomial interpolation functions. Exponential interpolation functions are derived for the purpose of modeling sharp gradients. General equations for conservation of mass, momentum, and energy for an inviscid flow of a perfect gas are converted to finite element equations using the least-squares method. Boundary conditions and a mesh adaptation scheme are also presented. An oblique shock reflection problem is used as a benchmark to determine whether or not exponential interpolation provides any advantages over Lagrange polynomial interpolation. Using exponential interpolation …

Understanding Millennial, Generation X, And Baby Boomer Preferred Leadership Characteristics: Informing Today’S Leaders And Followers, Lee-Volker Cox

Dissertations

Purpose. This quantitative study’s purpose was to describe and determine the degree of difference and importance of leadership characteristics as perceived by Baby Boom, Generation X, and Millennial generational cohort followers in STEM-related U.S.-based or headquartered aerospace and computer organizations as measured by the Multigenerational Leadership Characteristics Questionnaire (MLCQ).

Methodology. This was a cross-sectional, nonexperimental, comparative and correlational quantitative, ex post facto study. A web-based MLCQ was developed after conducting an academic literature review. Participants used a 6-point Likert scale identifying the importance of 30 characteristics with 2 aggregation questions identifying the most and least important characteristics; 408 members of …

Improved Performance By The Tie-Gcm With The Inclusion Of Helium As A Major Species, Fredrick R. Schmidt

Theses and Dissertations

When considering the neutral constituents in the upper thermosphere and exosphere, helium needs to be accounted for as a major species. As detailed by Emmert [2015], most first-principle models do not consider helium a major species when solving for diffusion and collisions within the atmosphere. First-principle, physics-based models hold a distinct advantage of seasonal variations and spatial resolution over empirical models which leads to a more realistic depiction of the atmosphere. The National Center for Atmospheric Research’s (NCAR) self-consistent, physics-based Thermosphere-Ionosphere-Electrodynamic General Circulation Model (TIE-GCM) has been updated to take into account this neutral constituent in its calculations. The major …

Liquid Fuel Film Cooling: A Cfd Analysis With Hydrocarbon Fuel, Jacob D. Bills

Theses and Dissertations

Cooling of liquid rocket engine combustion chambers and nozzles is a critical component to liquid rocket engine design. A common method of cooling is liquid fuel film cooling. Liquid fuel is injected along the surface of the wall to act as a barrier against the core combustion gases. A numerical model is developed for simulating liquid fuel _lm cooling in a rocket engine using a hydrocarbon fuel. The model incorporates turbulent multiphase ow with species transport within the commercial ANSYS® Fluent CFD software. Conjugate heat transfer is simulated through walls containing embedded cooling channels. A novel User Defined Function is …

Investigation Into Reynolds Number Effects On A Biomimetic Flapping Wing, Daniel K. Hope

Theses and Dissertations

This research investigated how the nature of the wing changed as a function of Reynolds number by measuring the forces produced by wings with varying characteristic lengths, tested at varying air densities. Increasing the wing span increased the overall weight of the wing, which reduced the 1st natural frequency; and did not result in an increase in vertical force over the baseline 50 mm wing. However; if the decrease in natural frequency was counteracted by increasing the thickness of the joint material in the linkage mechanism, vertical force production did increase over the baseline wing planform. Negligible forces and moments …

Formation Flight Of Earth Satellites On Low-Eccentricity Kam Tori, Christopher T. Craft

Theses and Dissertations

The problem of Earth satellite constellation and formation flight is investigated in the context of Kolmogorov-Arnold-Moser (KAM) theory. KAM tori are constructed utilizing Wiesel’s Low-Eccentricity Earth Satellite Theory, allowing numerical representation of the perturbed tori describing Earth orbits acted upon by geopotential perturbations as sets of Fourier series. A maneuvering strategy using the local linearization of the KAM tangent space is developed and applied, demonstrating the ability to maneuver onto and within desired torus surfaces. Constellation and formation design and maintenance on KAM tori are discussed, along with stability and maneuver error concerns. It is shown that placement of satellites …

Multi-Cubesat Deployment Strategies: How Different Satellite Deployment Schemes Affect Satellite Separation And Detection For Various Types Of Constellations And Missions, Scott A. Biehl Jr.

Theses and Dissertations

As economics drive an increased demand for small satellites and, consequently, an increase in the number of satellites deployed per launch, different deployment schemes and their effects on satellite dynamics must be well understood. While there are advantages to deploying multiple satellites at once, users may have trouble with tracking, identifying, and communicating with their satellites. This investigation examines the deployment of eight 3U CubeSats, and the resulting relative motion within a constellation. Both the distance between any two satellites within a constellation and the volume of a polygon encompassing a constellation are used to analyze the satellite dynamics within …

Conceptual Design, Structural Analysis, And Design Space Exploration Of A Vacuum Lighter Than Air Vehicle, Brian C. Cranston

Theses and Dissertations

The research detailed in this study investigates an internal vacuum as well as its optimal structural design, utilizing currently available materials, as an alternative to traditional gases to create and sustain buoyancy in lighter than air vehicles. To date, the consideration of a vacuum lighter than air vehicle has been limited to three sources of literature, the earliest of which dates back to 1663. This study will initially summarize and review this literature. We will then combine finite element analysis, dimensional analysis, design of experiments, and response surface methodology studies to explore the feasibility, and the functional design of a …

Surface Roughness Of Electron Beam Melting Ti-6al-4v Effect On Ultrasonic Testing, Evan T. Hanks

Theses and Dissertations

Experimental research was conducted on the effects of surface roughness on ultrasonic non-destructive testing of Electron Beam Melted (EBM) additively manufactured Ti-6Al-4V. Additive Manufacturing (AM) is a developing technology with many potential benefits, but certain challenges posed by its use require further research before AM parts are viable for widespread use in the aviation industry. Possible applications of this new technology include, Aircraft Battle Damage Repair (ABDR), small batch manufacturing to fill supply gaps, and replacement for obsolete parts. The research presented here assesses the effectiveness of ultrasonic inspection in detecting manufactured flaws in EBM manufactured Ti-6Al-4V. EBM products are …

Key Detection Rate Modeling And Analysis For Satellite-Based Quantum Key Distribution, Jonathan C. Denton

Theses and Dissertations

A satellite QKD model was developed and validated, that allows a user to determine the optimum wavelength for use in a satellite-based QKD link considering the location of ground sites, selected orbit and hardware performance. This thesis explains how the model was developed, validated and presents results from a simulated year-long study of satellite-based quantum key distribution. It was found that diffractive losses and atmospheric losses define a fundamental trade space that drives both orbit and wavelength selection. The optimal orbit is one which generates the highest detection rates while providing equal pass elevation angles and durations to multiple ground …

Spectroscopic Measurement Of Gas Temperature In Small Internal Combustion Engines, Matthew J. Deutsch

Theses and Dissertations

The Small Engine Research Bench (SERB) was used previously to measure spatially and temporally averaged heat flux, as well as local, instantaneous heat flux at several external locations, for a series of small engines (1 - 10 kW). This investigation obtained time averaged crank angle resolved measurements of the in-cylinder gas temperature using Fourier transform infrared (FTIR) absorption thermometry. The results, coupled with heat flux measurements, will enable the validation or refinement of existing thermal energy loss models.

Enhanced Flow Migration In Full Annular Ultra Compact Combustor, Nicholas A. Gilbert

Theses and Dissertations

Since combustion efficiency in modern jet engines has stabilized, attention has turned to improving the combustor by improving the thrust-to-weight ratio. The Ultra Compact Combustor (UCC) is a means to reduce the weight of the combustor while ensuring exhaust meets increasingly stringent government emission standards. Combustion occurs within the UCC under a g-load in the circumferential direction, which maintains combustion efficiency while decreasing axial combustor length. Previous analysis optimized the combustion chamber flame characteristics with a common upstream air source. Previously, issues for the UCC were inspired by integration into a traditional axial turbojet. The focus of this investigation was …

Localized Plasma Measurement During Instability Modes In A Hall Thruster, David A. Cunningham

Theses and Dissertations

Hall thrusters are a key technology for current and future unmanned satellites, striking a balance between thrust and fuel economy suitable for many mission profiles of interest. Despite their extensive flight heritage and a large body of research, many phenomena occurring in the plasma discharge of Hall thrusters are not well understood. A combination of intrusive and non-intrusive measurement techniques were used to investigate the properties of the exhaust plume of two Hall thrusters and correlate optical characteristics of oscillating modes with the plasma potential and azimuthal current distribution during those modes. A strong trend was found associating the optical …

Space Object Self-Tracker On-Board Orbit Determination Analysis, Stacie M. Flamos

Theses and Dissertations

Due to the United States' growing dependence on space based assets and the in- creasing number of resident space objects (RSO), improvement of Space Situational Awareness (SSA) capabilities is more necessary than ever. As a way to aid in this need, the Air Force Institute of Technology (AFIT) is developing the Space Object Self-Tracker (SOS) as a proof-of-concept experimental satellite for RSO precision tracking and collision avoidance system in Low Earth Orbit (LEO). Specifically, SOS will use Global Positioning System (GPS) position estimates for on-board orbit de- termination. Currently, SOS will use the Simplified General Perturbations-4 (SGP4) algorithm as its …

Effects Of Additive Manufacturing Methods On The Dynamic Properties Of 15-5ph Stainless Steel, Allison A. Dempsey

Theses and Dissertations

Experimental research was conducted to determine the dynamic properties and characterize the microstructure of 15-5PH Stainless Steel manufactured through Direct Metal Laser Sintering (DMLS) additive manufacturing (AM) processes and heat treated using common heat treatment protocols. A thorough understanding of the material's properties is necessary before such parts are utilized in an operational capacity. Of the five builds, two deviated significantly from the specified composition of 15-5PH stainless steel. The remaining three builds, possessing the desired composition and crystalline structure, were tested in compression and tension at two strain rates. Tension tests using a reflected wave and a momentum trap …

Orbital Resonances In The Vinti Solution, Laura M. Duffy

Theses and Dissertations

The Vinti Solution offers a more accurate model than the two-body problem as an orbital propagator. Unfortunately, the Vinti solution contains small divisors near orbital resonances in the perturbative terms of the Hamiltonian, which lead to inaccurate orbital predictions. One approach to avoid the small divisors is to apply transformation theory. The methodology of this research is to identify the perturbative terms of the Vinti Solution, perform a coordinate transformation, and derive the new equations of motion for the Vinti system near orbital resonances. The analysis in this research focuses on the 2:1 resonance, which includes the Global Positioning System. …

Evaluation Of Unmanned Aircraft Flying Qualities Using Jsbsim, Joshua P. Kim

Theses and Dissertations

Flying qualities data can be used to predict the future performance of aircraft; however, no flying qualities requirements exist for Unmanned Aerial Vehicles (UAVs). The intent of flying qualities requirements is to guarantee the safety and operational effectiveness of the aircraft. Flying qualities requirements have been extensively researched and specified for fixed-wing and rotary-wing manned aircraft based on a substantial database of assessments. The critical issue today in flying qualities is how to extend them to pilotless aircraft. A simulation study using an open-source flight dynamics model (JSBSim) was conducted to perform various performance maneuvers and evaluate how well the …

Analysis Of A Modified Equivalent Circuit Model For Lithium-Ion Battery Modules In Cubesats, James J. Liu

Theses and Dissertations

Failure of the electrical power system (EPS) to meet mission requirements is a common problem in nano-size satellites commonly referred to as CubeSats. The motivation for this research stems from the desire to prevent EPS failure through a process of testing and space qualification of components. Utilizing models to predict the behavior of an EPS before it is designed, built, and tested for space can provide critical insight in areas of limitation in performance and survivability. Modeling an entire EPS system is challenging because it requires extensive knowledge of all components and their behavior. This research focuses specifically on the …

Performance Testing Of Various Nozzle Design For Water Electrolysis Thruster, Yuen Liu

Theses and Dissertations

The purpose of this research is to develop new nozzles for the HYDROS^TM thruster, a pulsed chemical thruster, to improve the current flight performance. This research consists of a base line test of the factory nozzle, as well as testing of three 15-degree conical nozzles with different expansion ratios. Experiments were conducted at plenum pressures 30, 40, and 45 psia to ensure the thruster is throttleable. Impulse bit data was collected through measuring the impulse response of each firing using a torsional balance thrust stand. Analysis of the thruster performance included calculations of impulse bit, specific impulse, thrust coefficient, …

Geolocation Of Rf Emitters Using A Low-Cost Uav-Based Approach, Michael A. Magers

Theses and Dissertations

The proliferation of unmanned aerial vehicles (UAVs) in both military and civilian settings has prompted great interest in finding new and innovative ways to utilize these tools. One such application is to locate ground-based radio emitters from a UAV platform. The goal of this research is to study the feasibility of a low-cost (on the order of $1000) UAV geolocation platform. To accomplish this goal, a series of both real-world flight testing and computer simulated scenarios were conducted. Simulations for different sensor uncertainties and approach path scenarios such as loiter and button hook patterns were investigated. Results showed that a …

Development Of A Modularized Software Architecture To Enhance Ssa With Cots Telescopes, Julian P. Mccafferty

Theses and Dissertations

As the catalog of Earth orbiting objects continues to grow exponentially, so too does the necessity for Space Situational Awareness (SSA). Previous work at AFIT has explored augmenting the Space Surveillance Network (SSN) by demonstrating detection and tracking of orbiting objects using Commercial-Off-The-Shelf (COTS) telescopes and Air Force generated Two-Line Element Sets (TLE). This research explores the process of developing and reengineering code into a modularized, hierarchical component architecture designed for the end user while enabling developers to continue to modify the software for future applications. Three graphical user interfaces (GUI) are compiled into standalone executable programs using MATLAB for …

Toward Automated Aerial Refueling: Relative Navigation With Structure From Motion, Kevin W. Colson

Theses and Dissertations

The USAF's use of UAS has expanded from reconnaissance to hunter/killer missions. As the UAS mission further expands into aerial combat, better performance and larger payloads will have a negative correlation with range and loiter times. Additionally, the Air Force Future Operating Concept calls for \formations of uninhabited refueling aircraft...[that] enable refueling operations partway inside threat areas." However, a lack of accurate relative positioning information prevents the ability to safely maintain close formation flight and contact between a tanker and a UAS. The inclusion of cutting edge vision systems on present refueling platforms may provide the information necessary to support …

Real-Time Implementation Of Vision-Aided Monocular Navigation For Small Fixed-Wing Unmanned Aerial Systems, Timothy I. Machin

Theses and Dissertations

The goal of this project was to develop and implement algorithms to demonstrate real-time positioning of a UAV using a monocular camera combined with previously collected orthorectified imagery. Unlike previous tests, this project did not utilize a full inertial navigation system (INS) for attitude, but instead had to rely on the attitude obtained by inexpensive commercial off-the-shelf (COTS) autopilots. The system consisted of primarily COTS components and open-source software, and was own over Camp Atterbury, IN for a sequence of flight tests in Fall 2015. The system obtained valid solutions over much of the flight path, identifying features in the …

Visual-Ins Using A Human Operator And Converted Measurements, Turner J. Montgomery

Theses and Dissertations

A method human operated INS aiding is explored in which the pilot identifies and tracks a ground feature of unknown position over a short measurement epoch using an E/O sensor. One then refers to Visual-INS. In contrast to current research trends, a human operator is entrusted with visually tracking the ground feature. In addition, a less conventional measurement linearization technique is applied to generate “converted” measurements. A linear regression algorithm is then applied to the converted measurements providing an estimate of the INS horizontal velocity error and accelerometer biases. At the completion of the measurement epoch, the INS is corrected …