Engineering Commons^™

Flight Control Design Using Mixed H2/Μ Optimization, Douglas D. Decker

Theses and Dissertations

This thesis examines the use of the mixed H2-Microns optimal control synthesis method in the design of a flight control system for the lateral-directional axes of the F-16 Variable Stability In-Flight Simulator Test Aircraft (VISTA). The method is designed to minimize the H2 norm (two-norm) for a given value of microns. This should provide adequate noise and disturbance rejection while maintaining robustness against several types of uncertainties in the system. This thesis finds that, for this problem, the two-norm is not an accurate representation of the outputs of interest. When the two-norm is broken up into its constituent parts an …

Viscoplastic Characterization And Fatigue Modeling Of Titanium Based Metal Matrix Composites, Mark A. Foringer

Theses and Dissertations

Viscoplastic characterization and fatigue modeling of titanium-based metal matrix composites was accomplished by combining a unified viscoplastic theory, a nonlinear micromechanics model, and a linear damage accumulation model. First. Ti 15-3 was characterized using the Bodner-Partom viscoplastic theory. A micromechanics model was then employed in a linear damage accumulation fatigue model to predict the fatigue behavior of titanium based composites. The viscoplastic behavior predictions of the micromechanics model were used to eliminate separately defined time dependent terms in the fatigue model. Also, a new linear damage accumulation model was developed from the fatigue behavior of the composite constituents. Finally, it …

Applications Of ℓ1 And Mixed H2/ℓ1 Optimization, Mark S. Spillman

Theses and Dissertations

This thesis explores the use of ℓ₁ and mixed H2/ℓ1 optimization methods to design flight control systems. ℓ₁ optimization is used to handle tracking issues in the design of digital compensators. Control deflection and rate limitations, overshoot and undershoot limitations and steady-state error requirements are discussed. Model-matching techniques which produce acceptable tracking results with lower order controllers are also examined. New numerical methods for continuous H2/L1 and discrete H2/ℓ1 optimization are presented. These methods are used to design an aircraft controller in continuous and discrete time and the results are compared.

The Design And Development Of A Low-Speed, Low-Force Wind Tunnel Data Acquisition System With An Application To Bicycle Front Fork Spacing, Alan W. Elledge

Theses and Dissertations

This thesis encompassed the design, development, and application of a low-speed, low-force data acquisition system for the AFIT 5-ft Wind Tunnel. The new data acquisition system was designed and developed to measure approximately 0.045 N (about 0.01 lb_f) at nearly 64.4 km/h (40 mph). Verification of the capability was obtained through testing of a cylindrical model. As part of a technology transition program with Wright Laboratory, this new system was used to investigate bicycle front fork blade spacing in order to determine the optimal spacing for minimum drag. As for the minimum drag of a bicycle with an …

A New Drag Measurement System For Wind Tunnel Testing Of The Racing Bicycle And Rider To Determine A Low Drag Configuration, Brian A. Parker

Theses and Dissertations

This study investigated the application of splitter plate effects to reduce the aerodynamic drag of the racing bicycle and rider system. A sensitive, low-force, beam-type, single-component balance was developed to provide drag measurements accurate to within 0.053 N (0.012 lb_f). The performance of the new system was verified by comparing the measured drag on a three-dimensioaal, right-circular cylinder model, 0.127 m (5.0 in) in diameter and 0.610 m (24 in) long, with the results from a commercial balance and a other similar data. The bicycle and rider model consisted of a full-scale mannequin comprising only the hips, legs …

An Investigation And Improvement Of Electrorheological (Er) Fluid Technology, Adil F. Dalal

Masters Theses

The purpose of this research was to investigate and overcome the limitations of Electrorheological (ER) fluids and to introduce this advanced technology at WMU. Electrorheological (ER) Fluids are a special class of fluids, which exhibit a reversible, infinitely variable phase transition from a liquid to a solid/semi-plastic state, in the presence of an electric field.

ER fluids can provide a unique solution to the problems of vibration isolation of systems. The applications are currently limited due to the high voltage requirements, electric power related heating and limited research into wear/abrasive characteristics of ER fluids.

A specially designed and constructed "electro-viscosimeter" …

Investigation Of Boundary Layer And Performance Effects Of Transpiration Cooling Through A Porous Plate In A Rocket Nozzle, David N. Keener

Theses and Dissertations

This study used a range of low blowing ratios with air through an area of porous material in a Mach 2.0 nozzle to quantity the change in boundary layer thickness as a function of blowing ratio. Also, exit and wall Mach number profiles at each blowing ratio were collected to characterize performance losses as a result of blowing. Performance in terms of specific impulse was also studied. As expected, the boundary layer thickness increased and nozzle performance in terms of exit Mach number decreased with increasing blowing ratio.

Fatigue Behavior Of A Cross-Ply Ceramic Matrix Composite At Elevated Temperature Under Tension-Tension Loading, Craig D. Steiner

Theses and Dissertations

This study investigated the fatigue behavior and damage mechanisms of a [0-90]_4s SiC-MAS ceramic matrix composite under tension-tension loading at two elevated temperatures and two frequencies. Stress and strain hystereses, maximum and minimum strain, and modulus of elasticity were evaluated to characterize the material behavior. Microscopy and fractography were used to evaluate damage progression and mechanisms. Fatigue life was independent of frequency at both temperatures.

Experimental Investigation Of The Effects Of Relative Physical Orientation Between Evaporator And Condenser For A Loop Heat Pipe, Brad R. Thompson

Theses and Dissertations

This research examined the effects on performance of varying angular orientation and height differences between evaporator and condenser for a loop heat pipe. Performance was defined as the difference in temperature between evaporator and condenser (DELTA T). The pipe was evaluated at varying input power (Qin) for: varying evaporator and condenser angles, different coolant temperatures, and varying relative height differences. All analysis included only steady state operation. The performance was influenced by condenser angles, with an optimal condenser angle for best performance being +45 degrees from horizontal. Additionally, the evaporator angles were found to influence performance only at low Qin …

Compressible Turbulence Measurements In A Supersonic Flow With Adverse Pressure Gradient, Jon W. Dotter

Theses and Dissertations

Mean flow and compressible turbulence measurements have been obtained upstream and within a shock boundary interaction and a compression ramp in Mach 3 flow. Compressible turbulence models have met with little success in the accurate prediction of high-speed flows involving complicated shock boundary interactions and adverse pressure gradients because of a crucial lack of experimental data. Data were collected using conventional Pitot and cone static probes, single overheat cross-wire anemometry, multiple overheat cross-wire anemometry, and flow visualization techniques. Direct measurements of the total Reynolds shear stress were obtained using a turbulence transformation. Results indicate that compressibility effects, as evidenced by …

Performance Characterization Of A Highly-Offset Diffuser With And Without Blowing Vortex Generator Jets, Michael B. Senseney

Theses and Dissertations

The effect of blowing vortex generator jets (VGJs) on the performance of a highly-offset (s-duct) diffuser was investigated experimentally. VGJs are pitched, skewed jets which generate streamwise vortices as well as injecting high-momentum fluid into the boundary layer. Diffuser performance with and without VGJs was measured for an inlet Mach number of 0.6 (Re/x = 1.27x10⁷ per cm). Pitot static and hot-film instrumentation was used to measure flow properties at the diffuser inlet and exit planes. Without blowing, the flow on the lower surface of the diffuser was massively separated. Blowing at 0.48% mass flow ratio through three lower-surface …

An Integrated Gps-Ins-Baro And Radar Altimeter System For Aircraft Precision Approach Landings, Robert A. Gray

Theses and Dissertations

Currently, the Department of Defense (DoD) and the commercial airline industry are utilizing the Instrument Landing System (ILS) during aircraft landings for precision approaches. The replacement system for the aging ILS was thought to he the Microwave Landing System (MLS). Instead, use of the Global Positioning System (GPS) is now thought to be a viable replacement for ILS precision approaches. The majority of current precision landing research has exploited 'stand-alone' GPS receiver techniques. This thesis instead explores the possibilities of using an extended Kalman filter (EKF) that integrates an Inertial Navigation System (INS), GPS, Barometric Altimeter, Pseudolite and Radar Altimeter …

Control Of A Large Space Structure Using Multiple Model Adaptive Estimation And Control Techniques, Gordon C. Griffin Jr.

Theses and Dissertations

A moving bank multiple model adaptive estimator-controller (MMAE-MMAC), based on linear system, quadratic cost, and Gaussian noise (LQG) assumptions, is used to quell unwanted vibrations in a large flexible space structure. The structure, known as the SPace Integrated Controls Experiment, or SPICE, exists at Phillips Laboratory, Kirtland AFB, NM. The structure consists of a large platform and a smaller platform connected by a tripod of flexible legs. The purpose of the control system is to maintain a very precise line-of- sight vector through the center of the spacecraft. Kalman filtering, used to estimate the position and velocity of the bending …

Optimization Of A Nutation Damper Attached To A Spin-Stabilized Satellite, Brady P. Hauboldt

Theses and Dissertations

This study uses linearized equations of motion for a rigid body with an attached spring-mass-damper to maximize the decay rate of a satellite's coning motion. An analysis of the numerical eigenvalues is presented which leads to an optimal relationship between relevant parameters: damper placement, spring constant, damping coefficient, system moments of inertia, and damper mass fraction. The coupled system's eigenvalues do not provide truly critical damping, thus the real eigenvalue parts are minimized in order to achieve damping which requires the minimum amount of time. A comparison between this optimal design method and a classical method concludes a noticeable improvement …

Generic Satellite Monitoring Expert System, Loretta A. Kelemen

Theses and Dissertations

Air Force Satellite Operations is undergoing major changes. Operators no longer receive detailed satellite training, instead they are taught basic fundamentals of satellite operations and expected to control multiple multimillion dollar satellites. The need is clear. An efficient and economical automated system is necessary to assist the satellite operator in his daily tasks of maintaining these DOD priority resources. Satellite intelligent controllers been under R&D since the early 1980s to this need. These systems, however, have focused on the control of one constellation of satellites. In a military striving for efficiency and lower costs, developing a unique intelligent controller for …

A Multi-Attribute-Utility-Theory Model That Minimizes Interview-Data Requirements: A Consolidation Of Space Launch Decisions, Raymond W. Staats

Theses and Dissertations

This research uses multi-attribute utility theory (MAUT) to define a mathematical representation of a decision maker's utility associated with a satellite system. While developing the survey instrument, we focused on making it simpler to administer, primarily by eliminating the use of lottery questions. These simplifications enabled us to shorten our interview with the decision maker to under two hours for a rather complex model.

Weighting Scheme For The Space Surveillance Network Automated Tasker, Beth L. Petrick

Theses and Dissertations

The purpose of this research is to find the best weighting scheme in the SPADOC 4C Sensor Tasking Prototype. This software, known as the Prototype Tasker, assigns a tasking to each sensor of the Space Surveillance Network. A tasking is a list of objects in which the sensor needs to gather positional data, called observations. One of the inputs to the Prototype Tasker is a user-definable weighting scheme. The goal is to find the weighting scheme that produces the most efficient taskings. This problem was solved using a Simulated Annealing algorithm. The values in the weighting scheme were the variables …

Analysis Of Hypersonic Boundary Layer Second Mode Instability Over A 7° Cone, Richard A. Dennery

Theses and Dissertations

This paper presents the results of the analysis of Mach 8.0 flow over a seven degree half-angle cone. The purpose of this analysis was to develop techniques to examine boundary layer transition at hypersonic velocities. The specific objectives were to look for second mode instability waves characteristic of the transition process and to quantify the percentage of turbulent flow. Two sets of data were used in this analysis. The first set of data was taken at several axial positions at a freestream Reynolds number 4.265 million per meter. This data was used to develop the analysis techniques. The second set …

Improved Numerical Solution Of Mixed H2/H∞ Optimization With Applications, Linda D. Smith

Theses and Dissertations

This study improved the numerical optimization technique used to compute mixed H₂/H_∞ controllers. The run time to generate the full curve of an H₂/H_∞ design was reduced by a factor of almost 200 for a specific example. This was accomplished by improving gradient calculations, upgrading the H_∞ norm calculation to capture multiple peaks in the singular value plot and using routines that minimized processing time. The optimization routine used was the MATLAB CONSTR' Sequential Quadratic Programming (SQP) routine. This SQP routine was compared to a FORTRAN SQP numerical optimizer, IMSL-DNCONG. The method was …

Flow Visualization Of A Turbulent Shear Flow Using An Optical Wavefront Sensor, Daniel W. Jewell

Theses and Dissertations

The research reported here investigated the use of a shearing interferometer (SI) wavefront sensor to determine the effects of shear-layer turbulence on an optical wavefront. A collimated helium-neon laser beam was propagated through a plane shear-layer produced by mixing helium and nitrogen at different velocities. Since the gases have different indices of refraction, the optical wavefront was distorted by different amounts by each gas. The SI measured the wavefront slope across the sampled area of the wavefront. The shear-layer was viewed from two orthogonal directions. This document contains shadow graphs, interference patterns imaged by each of the SI's six cameras, …

Computing Norad Mean Orbital Elements From A State Vector, Dwight E. Andersen

Theses and Dissertations

NORAD maintains and disseminates mean orbital elements on Earth-orbiting satellites in the form of Two-Line Element Sets (TLE). Five mathematical propagator models were developed for NORAD's use to predict the position and velocity using TLEs. This study investigated two approaches, Newton's method and direct iteration, to inverting this process by iterating to obtain NORAD-compatible mean orbital elements from a position and velocity state vector and the drag term. The Newton's iteration method was developed but not tested. The less computationally intensive direct iteration method was developed, coded in FORTRAN, and tested. The initial guess and subsequent corrections in the iterative …

A Decision Support Model For Establishing A Plastics Recycling Program, Deven M. Dalcher

Theses and Dissertations

This research focuses on the development of a decision support model for the establishment of a plastics recycling program. The decision support model focuses on identifying the end-product uses and material specifications first. Once the end-product specifications have been identified, the recycling program can be designed. The model will provide solid waste managers an effective decision-making tool to evaluate the economic feasibility of establishing a plastics recycling program.

A Systems Engineering Approach To Environmental Risk Management: A Case Study Of Depleted Uranium At Test Area C-64, Eglin Air Force Base, Florida, Charles M. Carter, Kristina M. Fortmann, Stephen W. Hill, Robert M. Latin, Edward J. Masterson, Joseph A. Roh, Sujay R. Setlur

Theses and Dissertations

Environmental restoration is an area of concern in an environmentally conscious world. Much effort is required to clean up the environment and promote environmentally sound methods for managing current land use. In light of the public consciousness with the latter topic, the United States Air Force must also take an active role in addressing these environmental issues with respect to current and future USAF base land use. This thesis uses the systems engineering technique to assess human health risks and to evaluate risk management options with respect to depleted uranium contamination in the sampled region of Test Area (TA) C-64 …

Effects Of Blowing Ratio On Heat Transfer To The Throat Region Of A Porous-Walled Nozzle, Joseph L. Lenertz

Theses and Dissertations

This experiment analyzed the effects of blowing ratio on heat transfer to the throat region of a porous-walled nozzle, using the AFIT low speed shock tube. Heat flux data were taken from both sides of a two-dimensional Mach 2.0 Re-m=5.2x10⁷ nozzle using thin film resistance thermometers. One side was transpiration-cooled by secondary air injection through a sintered wall, while the other side served as a control. Control results were validated using empirical relations, and cooled side results showed up to a 14% reduction in heat transfer coefficient at blowing ratios of only 0.51%. The linear nature of cooling effectiveness …

Telepresent Spacecraft Docking With Object-Based Bilateral Control (Obbc), Paul Woznick

Theses and Dissertations

The concept of object-based control is extended to the field of teleoperation, specifically to accomplish the task of spacecraft docking via a bilateral manual controller. An object-based controller with bilateral feedback controls the motion of the grasped object, not the trajectory of the manipulator. For this reason it can be designed with feedback that is intricately linked with the task kinematics. The benefits derived from anthropomorphicity and force feedback are possible without kinematically-geometrically similar master-slave systems, complex calibration and joint mapping schemes, or expensive, high degree-of-freedom force reflection. Object-based control is ideal for low-level telerobotic interfaces. A hand controller and …

Stall Precursor Study Of High Frequency Data For Three High Speed, Swept Compressor Rotors, James F. Anderton

Theses and Dissertations

The frequency spectra of three single stage, high speed compressor rotors were derived and analyzed from experimental data. The compressor rotors included straight, backward-swept, and forward-swept blade designs. Data was acquired from four pressure transducers located on the compressor casing and arranged axially between locations 40% of blade chord upstream of the rotor face to just over the leading edge of the blades. Each rotor was throttled to stall at two constant speeds between 90% and 100% of design speed. Data digitization at 20 kHz revealed multiples of the rotor frequency up to and beyond a dominant blade passing frequency. …

Investigation Of Tension-Compression Fatigue Behavior Of A Notched Cross-Ply Metal Matrix Composite At Elevated Temperature, Matthew W. Yocum

Theses and Dissertations

This research extends the existing knowledge of MMC fatigue damage mechanisms by studying the tension-compression fatigue behavior of a notched cross-ply laminate MMC at elevated temperature. A [0-90]_2S SCS-6-Ti-15-3 laminate with a center hole was subjected to tension-compression fatigue at 427 °C (800 °F). Stress and strain data was taken to evaluate macro-mechanic behavior of the material. Microscopy and fractography were performed to characterize the damage on a micro-mechanical level. Crack initiation and progression was monitored using acetate face replicas. Four cracks were found to develop around the periphery of the hole, two of which became dominant and proceeded …

The Design And Analysis Of Integrated Navigation Systems Using Real Ins And Gps Data, Curtis D. Evans

Theses and Dissertations

An extended Kalman filter (EKF) is used to combine the information obtained from a Global Positioning System (GPS) receiver and an Inertial Navigation System (INS) to provide a navigation solution. This research compares the results of an actual tightly-coupled GPS-INS integrated system with those obtained in computer simulation. Differences between the simulation and actual hardware results, such as navigation solutions and tuning values, are shown in the research. An analysis of various GPS models was studied to determine the best representation for a system truth model. Measurement updates and their effects upon position accuracies was considered and preliminary research was …

Analysis And Simulation Of Narrowband Gps Jamming Using Digital Excision Temporal Filtering, Gerald L. Falen

Theses and Dissertations

The purpose of this thesis is to investigate the performance of the Digital Excision Temporal Filter (DETF) to reject narrowband jammers used against the Global Positioning System (GPS). The DETF takes the Fast Fourier Transform (FFT) of the GPS signal and excises any FFT bins that are above a preselected threshold level. Then the excised signal is Inverse Fourier Transformed and fed to the GPS receiver. Several jammer types are simulated including Continuous Wave (CW), Pulse CW, Swept CW, Narrowband Spot Noise, and Wideband Barrage Noise jammers. Cases are also simulated using all but the Wideband Barrage Noise jammer at …

An Experimental Study Of Planar Heterogeneous Supersonic Confined Jets, Frederick J. Tanis Jr.

Theses and Dissertations

The effects of varying the exit pressure of a supersonic helium jet exhausting coaxially with two parallel supersonic air streams into a constant area duct were investigated. The method used to evaluate the mass entrainment rate was to measure helium molar concentration profiles and mass flux across the duct using a binary gas probe then calculate the mass entrainment into the helium jet. In order to conduct this study a novel binary gas probe was developed which allowed helium concentration and mass flux data to be obtained during continuous traverses across the supersonic flowfield. High exit pressure ratio (EPR) led …