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Air Force Institute of Technology

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Articles 3841 - 3870 of 5699

Full-Text Articles in Engineering

Cargo Aircraft Bombing System (Cabs), Gurler Ari Mar 2003

Cargo Aircraft Bombing System (Cabs), Gurler Ari

Theses and Dissertations

From the early days of aviation, bombs typically have been carried by either fighter or bomber aircraft in the inventory. On the other hand, more and more long-range, precision-guided missiles are being produced with ranges that vary from tens to hundreds of miles. With such missiles, targets can be destroyed without placing personnel and equipment into close proximity to the targets. The mass delivery of standoff weapons could be especially advantageous during the early phases of an air campaign. This study considers the use of cargo aircraft for carrying and launching bombs and missiles. It discusses many aspects of a …

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The Air Force Operational Risk Management Program And Aviation Safety, Matthew G. Cho Mar 2003

The Air Force Operational Risk Management Program And Aviation Safety, Matthew G. Cho

Theses and Dissertations

Aviation mishaps are extremely costly in terms of dollar value, public opinion, and human life, The Air Force drastically reduced Class A mishap rates in its formative years. The rate plummeted from 44.22 mishaps per 100,000 flight hours in 1947 to 2.33 mishaps in 1983 and has held steady around 1.5 mishaps since. The Air Force implemented the Operational Risk Management (ORM) program in 1996 in an effort to protect their most valuable resources: aircraft and aviators. An AFIT thesis conducted in 1999 by Capt Park Ashley studied the Army similar Risk Management (RM) program. Ashley concluded that since his …

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Sensor-Craft Analytical Certification, Ronald W. Roberts Jr. Mar 2003

Sensor-Craft Analytical Certification, Ronald W. Roberts Jr.

Theses and Dissertations

This study developed a multi-disciplinary conceptual design of a joined-wing sensor-craft. Initial analysis was conducted using an aluminum model. Linear fully stressed design and flexible aerodynamic trim were used to converge to a minimum weight design that was aerodynamically stable. This optimized design was buckling safe. A similar optimization process using non-linear fully stressed design and flexible aerodynamic trim was conducted. The non- linear structurally deformation was over ten times greater than the linear structural deformation. Again, the model was structurally and aerodynamically optimized. The linear optimization was repeated using a composite structural model incorporating Conformal Load-bearing Antenna Structures. This …

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Groundwater Flow Through A Constructed Treatment Wetland, Jack A. Blalock Mar 2003

Groundwater Flow Through A Constructed Treatment Wetland, Jack A. Blalock

Theses and Dissertations

This study is an analysis of the flow of water through a constructed treatment wetland at Wright-Patterson AFB, OH. The purpose of the treatment wetland is to biodegrade perchioroethylene, which is present in the groundwater as a contaminant. Contaminated water enters the bottom of the wetland and flows upward, exiting the wetland from a weir at one end. The wetland is designed for water to move vertically through the soil layers composing the wetland. The main purpose of this study is to characterize the water flow through the different layers of soil in the wetland. In this study, hydraulic parameters …

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Modeling Catalytic Destruction Of Subsurface Contaminants In Recirculating Wells, Kerry J. Cadena Mar 2003

Modeling Catalytic Destruction Of Subsurface Contaminants In Recirculating Wells, Kerry J. Cadena

Theses and Dissertations

Groundwater and soil contamination is a significant problem throughout the nation, with approximately 300,000 to 400,000 sites affected (National Research Council, 1994). Examples of groundwater contaminants of special interest to DoD and AF installations include fuel hydrocarbons, chlorinated hydrocarbons, and nitroaromatic compounds. Traditional remediation technologies, which include pump-and-treat, permeable reactive barriers, and natural attenuation, have numerous drawbacks associated with them. These drawbacks have prompted researchers to look for innovative contamination clean-up methods. The technology investigated in this thesis, reticulating horizontal flow treatment wells (HFTWs) with in-well palladium (Pd) catalyst reactors, offers the potential for destruction of groundwater contaminants commonly found …

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A Proposed Military Construction Facility Investment Model, Andre R. Dempsey Mar 2003

A Proposed Military Construction Facility Investment Model, Andre R. Dempsey

Theses and Dissertations

The fiscal year (FY) 1999 and FY2000 National Defense Authorization Acts (NDAA) amended Title 10 USC, Section 17, and directed the secretary of defense to report annually on the capability of installations and facilities to provide support to forces in the conduct of their missions. This has come to be known as the Installations' Readiness Report (IRR). The Air Force's IRR links facility sustainment, restoration, and modernization (SRM) requirements, with the impact on the installation's ability to support the mission associated with the particular facility class. The Air Force's centralized military construction (MILCON) program model used to program major facility …

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The Effects Of Ionizing Radiation On Microelectromechanical Systems (Mems) Actuators: Electrostatic, Electrothermal, And Residual Stress, Jared R. Caffey Mar 2003

The Effects Of Ionizing Radiation On Microelectromechanical Systems (Mems) Actuators: Electrostatic, Electrothermal, And Residual Stress, Jared R. Caffey

Theses and Dissertations

The effects of ionizing radiation on the operation of polysilicon mmicroelectromechanical system (MEMS) electrostatic actuators, electrothermal actuators, and residual stress cantilevers were examined. Pre-irradiation, in-situ, and post-irradiation measurements were taken for the electrosatic and electrothermal actuators. The residual stress cantilevers were characterized before and after irradiation. All devices were irradiated to a total ionizing does of 1 megarad(Si) using both the Air Force Research Laboratory's low energy X-ray source and Co-60 gamma source.

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Analysis Of Broadband Higp-Impedance Ground Plane Antenna Designs, James W. Stewart Mar 2003

Analysis Of Broadband Higp-Impedance Ground Plane Antenna Designs, James W. Stewart

Theses and Dissertations

This research ties together computational and experimental analysis of two types of high-impedance ground plane (HIGP) antennas. One type of antenna consists of a proposed two-layer design. The structure consists of a bowtie antenna mounted over the surface of a HIGR The proposed structure was intended to achieve a resonant frequency of 3 GHz and a bandwidth of 48%; however, a design error results in a significant mismatch in operating bands between the antenna and HIGR Experiment results indicate the structure performs poorly across the entire measured band of 2-5 GHz. A new two-layer design is developed and presented. The …

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Quantum Mechanical Calculations Of Monoxides Of Silicon Carbide Molecules, John W. Roberts Jr. Mar 2003

Quantum Mechanical Calculations Of Monoxides Of Silicon Carbide Molecules, John W. Roberts Jr.

Theses and Dissertations

Modern semiconductor devices are principally made using the element silicon. In recent years, silicon carbide (SiC), with its wide band-gap, high thermal conductivity, and radiation resistance, has shown prospects as a semiconductor material for use in high temperature and radiation environments such as jet engines and satellites. A limiting factor in the performance of many SiC semiconductor components is the presence of lattice defects formed at oxide dielectric junctions during processing. Recent theoretical work has used small quantum mechanical systems embedded in larger molecular mechanics structures to attempt to better understand SiC surfaces and bulk materials and their oxidation. This …

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Multimission Aircraft Design Study, Payload, Ahmet Kahraman Mar 2003

Multimission Aircraft Design Study, Payload, Ahmet Kahraman

Theses and Dissertations

It is proposed that a Multi-Mission Aircraft (MMA) be prepared to combine some or all the functions of the aging AWACS, JSTARS, RIVET JOINT, COMPASS CALL, and AECCC fleet. Three different thesis studies have been developed by three Air Force Institute of Technology GSE students to show the feasibility of replacing the current aging fleet with one or more MMA platforms. This is the thesis in which the payload issuer have been examined. Within this thesis, two different alternative architectures, which are One Tail Number and Different Tail Numbers including nine different configurations, have been considered. Estimated payload characteristics of …

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Linear Programming And Genetic Algorithm Based Optimization For The Weighting Scheme Of A Value Focused Thinking Hierarchy, David M. Thawley Mar 2003

Linear Programming And Genetic Algorithm Based Optimization For The Weighting Scheme Of A Value Focused Thinking Hierarchy, David M. Thawley

Theses and Dissertations

Deriving weights for a Value Focused Thinking (VFT) hierarchy demands considerable time and input from Decision Makers (DM) and Subject Matter Experts (SME). Often, the DMs and SMEs are the leaders of companies and organizations, and this required time is unrealistic with their schedules. In these situations, as well as scenarios where there no available DMs/SMEs, conventional means of weighting a VFT hierarchy are impossible, and any VFT analysis is halted. When historical data exists on evaluation measures and performance of alternatives, linear programming and genetic algorithm based optimization may be used to derive historically optimal weights for a hierarchy. …

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An Analysis Of Multiple Layered Networks, Kevin T. Kennedy Mar 2003

An Analysis Of Multiple Layered Networks, Kevin T. Kennedy

Theses and Dissertations

Current infrastructure network models of single functionality do not typically account for the interdependent nature of infrastructure networks. Infrastructure networks are generally modeled individually, as an isolated network or with minimal recognition of interactions. This research develops a methodology to model the individual infrastructure network types while explicitly modeling their interconnected effects. The result is a formulation built with two sets of variables (the original set to model infrastructure characteristics and an additional set representing cuts of interdependent elements). This formulation is decomposed by variable type using Benders Partitioning and solved to optimality using a Benders Partitioning algorithm. Current infrastructure …

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An Analysis Of The Efficacy Of The Logistics Composite Model In Estimating Maintenance Manpower Productive Capacity, Kirk B. Pettingill Mar 2003

An Analysis Of The Efficacy Of The Logistics Composite Model In Estimating Maintenance Manpower Productive Capacity, Kirk B. Pettingill

Theses and Dissertations

The Logistics Composite Model (LCOM) is the tool of choice for many MAJCOM's (ACC, USAFE, AFMC) in determining maintenance manpower requirements. The LCOM is a simulation program capable of modeling the manpower, equipment, supplies, and facilities required to conduct aircraft maintenance activities, Manpower studies conducted with the LCOM result in manpower estimates that end up in Unit Manning Documents (UMD) as "LCOM earned," authorized positions. This research effort focuses on whether the LCOM can also be used to determine maintenance manpower's current capacity. Three different flying units at Cannon AFB, NM were modeled to determine if the LCOM, when programmed …

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Theoretical Comparison Of The Excited Electronic States Of The Linear Uranyl (Uo22+) And Tetrahedral Uranate (Uo42-) Ions Using Relativistic Computational Methods, Eric V. Beck Mar 2003

Theoretical Comparison Of The Excited Electronic States Of The Linear Uranyl (Uo22+) And Tetrahedral Uranate (Uo42-) Ions Using Relativistic Computational Methods, Eric V. Beck

Theses and Dissertations

This thesis examines the ground and excited electronic states of the uranyl (UO2+) and uranate (UO42-) ions using Hartree-Fock self-consistent field (HF SCF), multi-configuration self-consistent field (MCSCF) and multi-reference single and double excitation configuration interaction (MR- CISD) methods. The MR-CISD SD calculation included spin-orbit operators. Molecular geometries were obtained from self-consistent field (SCF ) second-order perturbation theory (MP2), and density functional theory (DFT) geometry optimizations using the NWChem 4.01 massively parallel ab initio software package. COLUMBUS version 5.8 was used to perform in-depth analysis on the HF SCF MCSCF and MR-CISD potential energy surfaces. Excited …

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Stress Analysis Of Silicon Carbide Microeletromechanical Systems Using Raman Spectroscopy, Stanley J. Ness Mar 2003

Stress Analysis Of Silicon Carbide Microeletromechanical Systems Using Raman Spectroscopy, Stanley J. Ness

Theses and Dissertations

During the fabrication of Micro-Electro-Mechanical Systems (MEMS), residual stress is often induced in the thin films that are deposited to create these systems. These stresses can cause the device to fail due to buckling, curling, or fracture. Government and industry are looking for ways to characterize the stress during the deposition of thin films in order to reduce or eliminate device failure. Micro-Raman spectroscopy has been successfully used to analyze poly-silicon MEMS devices made with the Multi-User MEMS Process (MUMPS trade name). Micro-Raman spectroscopy was selected because it is nondestructive, fast and has the potential for in situ stress monitoring. …

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Total Dose Effects Of Ionizing And Non-Ionizing Radiation On Piezoresistive Pressure Transducer Chips, Samuel J. Willmon Mar 2003

Total Dose Effects Of Ionizing And Non-Ionizing Radiation On Piezoresistive Pressure Transducer Chips, Samuel J. Willmon

Theses and Dissertations

The effects of ionizing and non ionizing radiation on the resistivity of silicon based, piezoresistive bulk micro-machined chips from pressure transducers were examined. Standard current-voltage (I-V) measurements were taken in-situ and post-irradiation during isothermal annealing at room temperature. One group of chips was irradiated to a maximum total gamma dose of lMrad(Si) in the 11,000 Ci (60) Co gamma cell at Ohio State University. The second group of chips was irradiated at the Ohio State University Research Reactor facility to a maximum total neutron dose of 4 Mrad(Si) using beam port Hi. The resistivity was shown to decrease during gamma …

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Evaluating The Performance Of Multiple Classifier Systems: A Matrix Algebra Representation Of Boolean Fusion Rules, Justin M. Hill Mar 2003

Evaluating The Performance Of Multiple Classifier Systems: A Matrix Algebra Representation Of Boolean Fusion Rules, Justin M. Hill

Theses and Dissertations

Given a finite collection of classifiers one might wish to combine, or fuse, the classifiers in hopes that the multiple classifier system (MCS) will perform better than the individuals. One method of fusing classifiers is to combine their final decision using Boolean rules (e.g., a logical OR, AND, or a majority vote of the classifiers in the system). An established method for evaluating a classifier is measuring some aspect of its Receiver Operating Characteristic (ROC) curve, which graphs the trade-off between the conditional probabilities of detection and false alarm. This work presents a unique method of estimating the performance of …

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Combining And Analyzing The Tanker And Aircrew Scheduling Heuristics, Cem Boke Mar 2003

Combining And Analyzing The Tanker And Aircrew Scheduling Heuristics, Cem Boke

Theses and Dissertations

Air refueling is an integral part of U.S. air power across a wide range of military operations. It is an essential capability in the conduct of air operations worldwide and is especially important when overseas basing is limited or not available. The planning, tasking, and scheduling of aerial refueling require solution of two major problems: assigning and scheduling of tankers to refueling points and efficiently assigning crews to each tanker. To address the scheduling of tankers, Wiley (2001) developed an efficient tabu search approach. Combs (2002) developed another tabu search approach to assign crews to tankers. This research combines the …

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Search Theory And U-Boats In The Bay Of Biscay, Ronald Gregory Carl Mar 2003

Search Theory And U-Boats In The Bay Of Biscay, Ronald Gregory Carl

Theses and Dissertations

Threats to our nation's resources and forces are becoming increasingly lethal and mobile. Therefore, our ability to locate and interdict these threats is more important than ever. Search theory is one tool that is vital to countering the increasing threat. This research presents a multi-agent simulation, built around the Allied search for U-boats in the Bay of Biscay during World War II, which extends several classic search theory algorithms. Comparison of techniques is based on the effectiveness of finding high- valued, mobile assets. A JAVA-based multi-agent simulation model is designed, built and tested, and used to demonstrate the existence of …

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Calculation Of The Actual Cost Of Engine Maintenance, Oguz Ezik Mar 2003

Calculation Of The Actual Cost Of Engine Maintenance, Oguz Ezik

Theses and Dissertations

The cost of military operations has been difficult to determine, yet considered of high importance. The cost of an operation is largely dependent upon the answers to subordinate questions involving the discrete costs of military activities, like supporting individual items, While different cost estimates have received attention from the media, the question arises as to how accurate these figures are, There have been numerous studies performed by the Operations Research analysts to minimize costs while allocating scarce resources, However, the values of these studies are dependent upon whether or not the cost figures used are sufficiently "true" or accurate, This …

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Optimum Component Design In N-Stange Series Systems To Maximize The Reliability Under Budget Constraint, Huseyin Gozebe Mar 2003

Optimum Component Design In N-Stange Series Systems To Maximize The Reliability Under Budget Constraint, Huseyin Gozebe

Theses and Dissertations

This research is intended to find a new heuristic for solving the reliability optimization of n-stage series system. The new heuristic will make the initial system design and use redundancy to improve system reliability level. The limited capacity of common optimization tools requires the new heuristic to be coded in VBA programming language. Moreover, the known reliability optimization heuristic, marginal analysis will be coded so that the difference between two heuristics can be seen and design engineers can use the best result in their applications.

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Analysis Of Scheduling Policies For A M/G/I Queue With Rework, Jennifer Hendrixson Mar 2003

Analysis Of Scheduling Policies For A M/G/I Queue With Rework, Jennifer Hendrixson

Theses and Dissertations

This thesis analyzes a multi-class M/G/1 priority queueing system in which distinct job types require one service cycle and, with non-zero probability, require a second service cycle. The main objective is to find a new heuristic scheduling policy that minimizes the long-run expected holding and preemption costs. Arrival rates, service rates, and the probability of undertaking second service are all class specific. A mean value analysis (MVA) approach was employed to derive the long- run mean time in queue for each job type under each policy, thereby providing the appropriate cost equations. Numerical experiments suggest that the preemptive resume scheduling …

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Planning Coverage Of Points Of Interest Via Multiple Imaging Surveillance Assets: A Multi-Model Approach, Sarah E. Jackson Mar 2003

Planning Coverage Of Points Of Interest Via Multiple Imaging Surveillance Assets: A Multi-Model Approach, Sarah E. Jackson

Theses and Dissertations

For the United States to maintain information superiority, it is necessary to have a means of allocating intelligence-gathering assets to collect information on particular points of interest. In today's geopolitical environment, however, the number of points of interest is growing rapidly, whereas the number of available assets is not. To aid in maintaining information superiority, this research explores the use of a Multi-Modal Goal Programming Resource Constrained Project Scheduling approach for allocating imaging surveillance assets (land, air, sea, and space) to a set of points of interest for a given time period. The multiple objectives of this formulation are to …

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A Value Focused Thinking Approach To Software Interface In A Complex Analytical Domain, Christopher M. Mcgee Mar 2003

A Value Focused Thinking Approach To Software Interface In A Complex Analytical Domain, Christopher M. Mcgee

Theses and Dissertations

The intelligence community is faced with an extensive amount of data. Software programs are being developed to examine this issue of data overload and to develop solutions. The responsibility of making the final software decision lies on the analyst, therefore, the interface is the key to linking the intelligence data to the processing and results, If the interface is difficult and complex, the software will be less likely to be used. A methodology must be created which can objectively evaluate the effectiveness of the interface, This methodology will also measure the improvements in the interface's effectiveness that result when various …

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Modeling Homeland Security: A Value Focused Thinking Approach, Kristopher A. Pruitt Mar 2003

Modeling Homeland Security: A Value Focused Thinking Approach, Kristopher A. Pruitt

Theses and Dissertations

The events of September 11, 2001 have propelled the topic of homeland security to the forefront of national concern. The threat of terrorism within the United States has reached an unprecedented level. The pervasive vulnerabilities of the nation's critical infrastructure coupled with the destructive capabilities and deadly intentions of modern terrorists pose extraordinary risks. The United States must mitigate these risks while at the same time balancing the associated costs and impact on civil liberties. Currently, the United States lacks effective methods and measure for assessing the security of the homeland from acts of terrorism. This study outlines a first …

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Analysis Of Cooperative Behavior For Autonomous Wide Area Search Munitions, Orhan Gozaydin Mar 2003

Analysis Of Cooperative Behavior For Autonomous Wide Area Search Munitions, Orhan Gozaydin

Theses and Dissertations

This research investigates the effectiveness of autonomous wide area search munitions using cooperative and non-cooperative behavior algorithms under various scenarios. The scenarios involve multiple autonomous munitions searching for an unknown number of targets with different priorities at unknown locations. For the cooperative cases, communications are allowed between the munitions to help locate, identify, and decide to pursue an attack on a target or to continue searching the rest of the battlefield. For non cooperative cases, munitions independently search, detect, identify and decide to attack an identified target or continue to search. Performance of the cooperative munitions depends on numerous parameters …

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Reduction Of Thermal Residual Strains In Adhesively Bonded Composite Repairs, Heather R. Crooks Mar 2003

Reduction Of Thermal Residual Strains In Adhesively Bonded Composite Repairs, Heather R. Crooks

Theses and Dissertations

Many military and commercial aircraft are being called upon to fly well beyond their original intended service lives. This has forced the United States Air Force (USAF) to increasingly rely on structural repairs to address fatigue induced damage and to extend aircraft useful life. The focus of this research is the use of a high-strength composite patch technique to repair a fatigue crack on an aluminum aircraft structure. This study investigates the thermal residual strains that occur as a direct result of the coefficient of thermal expansion (CTE) mismatch between the repair patch and the underlying cracked metallic structure to …

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The Effect Of A Hard Coating On The Damping And Fatigue Life Of Titanium, Frank T. Ivancic Mar 2003

The Effect Of A Hard Coating On The Damping And Fatigue Life Of Titanium, Frank T. Ivancic

Theses and Dissertations

This project compares the damping and fatigue life of bare titanium plates to those coated with magnesium aluminate spinel (mag spinel). Two different coating thicknesses were tested: .005" per side and .010" per side (total thicknesses of .010" and .020"). Dynamic ping tests were conducted on all specimens to determine their resonance frequencies. Laser vibrometry was used to determine the mode at each resonance frequency. Damping ratios were determined through the use of sine sweeps. A vibration mode was selected at which to fatigue the specimens, and the stress pattern was analyzed utilizing the Stress Pattern Analysis by Thermal Emissions …

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Computational Fluid Dynamics Investigation Of Vortex Breakdown For A Delta Wing At High Angle Of Attack, Jacob A. Freeman Mar 2003

Computational Fluid Dynamics Investigation Of Vortex Breakdown For A Delta Wing At High Angle Of Attack, Jacob A. Freeman

Theses and Dissertations

Using the commercially available FLUENT 3-D flow field solver, this research effort investigated vortex breakdown over a delta wing at high angle of attack (α) in preparation for investigation of active control of vortex breakdown using steady, along- core blowing. A flat delta-shaped half-wing with sharp leading edge and sweep angle of 60° was modeled at α=18° in a wind tunnel at Mach 0.04 and Reynolds number of 3.4 x 105. A hybrid (combination of structured and unstructured) numerical mesh was generated to accommodate blowing ports on the wing surface. Results for cases without and with along-core blowing …

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A Comparison Of Nonlinear Algorithms To Prevent Pilot-Induced Oscillations Caused By Actuator Rate Limiting, James G. Hanley Mar 2003

A Comparison Of Nonlinear Algorithms To Prevent Pilot-Induced Oscillations Caused By Actuator Rate Limiting, James G. Hanley

Theses and Dissertations

The objective of this study was to compare the ability of the Feedback-with-Bypass (FWB) and the Derivative-Switching (DS) flight control system filters to prevent PIO during actuator rate limiting, and the filters' effects on aircraft handling qualities. This comparison was conducted in three steps: computer simulation, ground simulation in the Large Amplitude Multimode Aerospace Research Simulator (LAMARS), and flight tests conducted in the Variable Stability In-flight Simulator Test Aircraft (VISTA). During computer simulation, the FWB filter better reduced the phase lag and prevented sustained or divergent oscillations during the closed-loop analysis. During both ground simulation and flight tests, the FWB …

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