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Articles 841 - 865 of 865

Full-Text Articles in Aerospace Engineering

A Handling Qualities Investigation Of Conventional, Rate Command- Attitude Hold, And Attitude Command-Attitude Hold Response-Types In The Probe And Drogue Air Refueling Task, Michael J. Taschner Mar 1994

A Handling Qualities Investigation Of Conventional, Rate Command- Attitude Hold, And Attitude Command-Attitude Hold Response-Types In The Probe And Drogue Air Refueling Task, Michael J. Taschner

Theses and Dissertations

This investigation examines the suitability of conventional, rate command/attitude hold (RCAH), and attitude command attitude hold (ACAH) response-types for the probe and drogue air refueling task. Data from a 1974 Calspan handling qualities investigation involving conventional response-types in the probe and drogue air refueling task were analyzed using the Bandwidth and STI Dropback criterions. Flight control laws were developed to achieve twelve superaugmented and two conventional configurations. The NT-33A analog variable stability system was used to simulate a relaxed static stability fighter and the NT-33A programmable digital flight control computer simulated the desired response-types. The handling qualities of the fourteen …

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Automation Of Formation Flight Control, Vincent P. Reyna Jan 1994

Automation Of Formation Flight Control, Vincent P. Reyna

Theses and Dissertations

The research contained in this thesis explores the concepts of Automated Formation Flight Control documented in three previous AFIT theses. The generic formation analyzed consists of a Leader and Wingman, with the Wingman referencing its maneuvers off of Leader maneuvers. Specifically, planar formation flight control concerning only heading and velocity changes is considered. Next, the vertical separation constraint is relaxed to allow wing maneuvers outside of the flight plane of the lead in order to minimize the energy expended by the wing in a maneuver. Analysis of the two forms of formation flight control investigated in this thesis reveals the …

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Exploring Qdes As A Tool For Determining Limits Of Achievable Performance In Aircraft Design, Mark F. Reidinger Dec 1993

Exploring Qdes As A Tool For Determining Limits Of Achievable Performance In Aircraft Design, Mark F. Reidinger

Theses and Dissertations

This thesis explores the usefulness of a computer aided control design software package called QDES in determining the limits of achievable aircraft performance as it relates to controller capability. Modern aircraft, particularly fighters, are being designed to be statically unstable to enhance their maneuverability and performance. It is possible that the aircraft, although physically capable of a certain level of performance due to its engine/ airframe combination, may be uncontrollable up to this level. This study sought to develop a methodology to use QDES to make a preliminary analysis of an aircraft design to determine if there exists a controller …

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Optimal Control Design Advantages Utilizing Two-Degree-Of-Freedom Controllers, Michael J. Stephens Dec 1993

Optimal Control Design Advantages Utilizing Two-Degree-Of-Freedom Controllers, Michael J. Stephens

Theses and Dissertations

The purpose of this study was to investigate and describe the differences between a one-degree-of-freedom (1-DOF) controller, in which a controller is placed in a single location in the control loop, and a two-degree- of-freedom (2-DOF) controller, in which two separate controllers are designed -- one in the feedback loop and the other as a prefilter in the forward loop. The approach involved summarizing the major rules governing loop shaping for performance and robustness in the 1-DOF case and then extending the concepts to the 2-DOF case. H2 optimization was utilized to perform several types of SISO examples and …

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Design Of A Flight Controller For An Unmanned Research Vehicle With Control Surface Failures Using Quantitative Feedback Theory, Mark S. Keating Dec 1993

Design Of A Flight Controller For An Unmanned Research Vehicle With Control Surface Failures Using Quantitative Feedback Theory, Mark S. Keating

Theses and Dissertations

This thesis describes the application of the multiple-input multiple- output (MIMO) Quantitative Feedback Theory (QFT) design technique to the design of a digital flight control system for the Lambda Unmanned Research Vehicle (URV). The QFT technique allows the synthesis of a control system which is robust in the presence of structured plant uncertainties. Uncertainties considered in this design are the aircraft's plant variation within the flight envelope and the effects of damage to aircraft control surfaces. Mathematical models of control surface failure effects on aircraft dynamics are derived and used to modify an existing small perturbation model of the Lambda. …

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Analysis And Characteristics Of Compressor Stall Precursor Signals In Forward And Aft Swept High Speed Compressor, Bernard J. Frank Dec 1993

Analysis And Characteristics Of Compressor Stall Precursor Signals In Forward And Aft Swept High Speed Compressor, Bernard J. Frank

Theses and Dissertations

The stall characteristic of four single-stage transonic compressor rotors were investigated as they were throttled to stall. Forward-swept, backward-swept, and straight leading edge rotors were examined. Three methods of analysis (1) windowed power spectrum densities of pressure and spatial Fourier coefficients, (2) phase tracking analysis, and (3) system identification were used to identify the first appearance of modal waves and their accompanying frequencies in order to identify a stall warning time. A direct correlation between the amount of stall warning time and the shape of the compressor characteristic was found. Specifically, if the compressor characteristic had a significant period of …

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Design Of A Subsonic Envelope Flight Control System For The Vista F-16 Using Quantitative Feedback Theory, Odell R. Reynolds Dec 1993

Design Of A Subsonic Envelope Flight Control System For The Vista F-16 Using Quantitative Feedback Theory, Odell R. Reynolds

Theses and Dissertations

A controlled plant's characteristics can vary widely throughout its operational envelope. This is a major problem in nominal plant-based control system design. Hence, gain scheduling is often used for full envelop design. In this paper, it is proposed to address the plant's variability using robust control design concepts. In particular, the frequency domain based Quantitative Feedback Theory Multiple-Input Multiple-Output robust control design method is employed for the synthesis of a full envelop flight control system for an F-16 derivative. Compensators for the aircraft's pitch and lateral directional channels are designed, and the designs are validated using linear simulations.

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Analysis And Simulation Of A Gps Receiver Design Using Combined Delay-Lock And Modified Tanlock Loops, George D. Harris Dec 1993

Analysis And Simulation Of A Gps Receiver Design Using Combined Delay-Lock And Modified Tanlock Loops, George D. Harris

Theses and Dissertations

The purpose of this thesis was to investigate the performance of two types of tracking loops used in Global Positioning System (GPS) receivers. The first loop, the Delay-Lock Loop (DLL), is responsible for maintaining synchronization with the received PN sequence. The second loop, the Modified Tanlock Loop (MTLL), is responsible for maintaining synchronization with the carrier signal. The performance of the two loops is investigated first separately then their performance is evaluated when operated together. This thesis is an investigation on the ability of these two loops to overcome corruption of the input signal due to noise. Expanding the dynamic …

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Evaluation Of Moderate Angle Of Attack Roll Of A Dual Engine, Thrust Vectoring Aircraft Using Quantitative Feedback Theory, Kevin E. Boyum Dec 1993

Evaluation Of Moderate Angle Of Attack Roll Of A Dual Engine, Thrust Vectoring Aircraft Using Quantitative Feedback Theory, Kevin E. Boyum

Theses and Dissertations

This thesis develops an innovative approach to the design of a flight control system for performing the large-amplitude velocity vector roll maneuver at high angles of attack AOAs. A six degree of freedom aircraft model is developed from the fundamental nine-state equations of motion using a modified linearization technique. The MIMO multiple-input multiple-output Quantitative Feedback Theory QFT robust control design technique is then used to jointly address the system nonlinearities present in this maneuver and the changes in the system parameters due to changes in flight condition, treating them as structured uncertainty in the design of a three-axis rate-commanded control …

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Neural Networks For Dynamic Flight Control, Ronald E. Setzer Dec 1993

Neural Networks For Dynamic Flight Control, Ronald E. Setzer

Theses and Dissertations

This thesis examines the application of artificial neural networks (NNs) to the problem of dynamic flight control. The specific application is the control of a flying model helicopter. The control interface is provided through a hardware and software test bed called the Fast Adaptive Maneuvering Experiment (FAME). The NN design approach uses two NNs: one trained as an emulator of the plant and the other trained to control the emulator. The emulator neural network is designed to reproduce the flight dynamics of the experimental plant. The controller is then designed to produce the appropriate control inputs to drive the emulator …

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Development Of An Air-To-Air Refueling Automatic Flight Control System Using Quantitative Feedback Theory, Dennis W. Trosen Jun 1993

Development Of An Air-To-Air Refueling Automatic Flight Control System Using Quantitative Feedback Theory, Dennis W. Trosen

Theses and Dissertations

Quantitative Feedback Theory and the improved method Quantitative Feedback Theory are enhanced to include the rejection of disturbance at the system output. The enhanced Quantitative Feedback Theory and improved method Quantitative Feedback Theory processes are applied to the design of an automatic flight control system to regulate position of the C-135B fuel receiving aircraft relative to the tanker during air-to-air refueling. A simple feedback control system is developed that will achieve stable position regulation. State-space aircraft models &re generated. An inner loop autopilot is designed to reduce the plant cutoff frequency and provide the system inputs for the Quantitative Feedback …

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Design And Implementation Of Fuzzy Logic Controllers. Thesis Final Report, 27 July 1992 - 1 January 1993, Osama A. Abihana, Oscar R. Gonzalez Jan 1993

Design And Implementation Of Fuzzy Logic Controllers. Thesis Final Report, 27 July 1992 - 1 January 1993, Osama A. Abihana, Oscar R. Gonzalez

Electrical & Computer Engineering Faculty Publications

The main objectives of our research are to present a self-contained overview of fuzzy sets and fuzzy logic, develop a methodology for control system design using fuzzy logic controllers, and to design and implement a fuzzy logic controller for a real system. We first present the fundamental concepts of fuzzy sets and fuzzy logic. Fuzzy sets and basic fuzzy operations are defined. In addition, for control systems, it is important to understand the concepts of linguistic values, term sets, fuzzy rule base, inference methods, and defuzzification methods. Second, we introduce a four-step fuzzy logic control system design procedure. The design …

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Strategies For Optimal Control Design Of Normal Acceleration Command Following On The F-16, James C. Baird Dec 1992

Strategies For Optimal Control Design Of Normal Acceleration Command Following On The F-16, James C. Baird

Theses and Dissertations

Weight shapes and locations are investigated for H2, H∞, and the general mixed H2/H infinity optimization methodologies. The design model is normal acceleration command following for the F-16 (SISO) at Mach 0.6 and Sea Level, which yields a nonminimum phase and unstable plant. H2 design types include LQG, LQG/Sensitivity, and LQG/Tracking. Robustness and tracking are the objectives of the central H infinity process. Both H∞ optimal and suboptimal controllers are examined, with the suboptimal controller shown as the practical choice for this plant. The mixed H2/H∞ setup allows the tradeoff between …

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Multiple Model Adaptive Estimation Applied To The Vista F-16 With Actuator And Sensor Failures, Timothy E. Menke Jun 1992

Multiple Model Adaptive Estimation Applied To The Vista F-16 With Actuator And Sensor Failures, Timothy E. Menke

Theses and Dissertations

A Multiple Model Adaptive Estimation (MMAE) algorithm is applied to the Variable Stability In-flight Simulator Test Aircraft (VISTA) F-16 at a low dynamic pressure flight condition (0.4 Mach at 20000 ft). A complete F-16 flight control system is modeled containing the longitudinal and lateral-directional axes. Single and dual actuator and sensor failures are simulated including: complete actuator failures, partial actuator failures, complete sensor failures, increased sensor noise, sensor biases, dual complete actuator failures, dual complete sensor failures, and combinations of actuator and sensor failures. Failure scenarios are examined in both maneuvering and straight and level flight conditions. The system performance …

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Comparative Analysis Of Guidance Algorithms For The Hyper Velocity Missile And Afti/F-16, Edward G. Rice Nov 1991

Comparative Analysis Of Guidance Algorithms For The Hyper Velocity Missile And Afti/F-16, Edward G. Rice

Theses and Dissertations

This project has provided me with endless intrigue. In considering the problem of guiding a hyper-velocity missile from a moving platform to a moving target, a common perception said it was just another Kalman Filtration design challenge. I began with lofty intentions of running a full up extended Kalman filter simulation but I became enthralled with the limited work available on the physical limitations of basic guidance algorithms. This became the emphasis of this project. The best filter scheme cannot overcome a guidance algorithms physical limitation. Only with an understanding of these limitations can one effectively integrate a guidance scheme …

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Application Of Mixed H2/H∞ Optimization, John J. Kusnierek Nov 1991

Application Of Mixed H2/H∞ Optimization, John J. Kusnierek

Theses and Dissertations

A non-conservative optimization technique is utilized to examine the problem of minimizing the 2 norm of one transfer function subject to an ∞-norm bound on another transfer function. For single exogenous input/ single exogenous output systems this non conservative mixed solution is shown to be up to 5% better in a specific example. For single exogenous input/two exogenous output systems the mixed solution is shown to be up to 27% better than a previous technique for a specific example. Finally, a two exogenous input/two exogenous output practical system is examined to demonstrate the utility of this mixed optimization technique.

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Development Of A Personal Computer Simulation Program Of The Ln-94 Inertial Navigation System, Thomas E. Flynn Jun 1991

Development Of A Personal Computer Simulation Program Of The Ln-94 Inertial Navigation System, Thomas E. Flynn

Theses and Dissertations

This thesis develops a simulation that emulates a Litton LN-94 INS. Real time simulation is achieved for a stationary navigation case and a straight-and-level flight trajectory are provided to exercise the simulation dynamics. The user interface is simple and requires little previous knowledge to operate. The communication link with the MILSTD 1553B bus provide a realistic environment in which to collect and analyze data. The simulation is processed on an 80386 IBM compatible personal computer. A 23-state INS error model is implemented and integration is performed by a fifth-order Kutta-Merson routine. The simulation is interfaced to a plotting routine and …

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An Erasable Optical Memory Based On Stimulated Electronic Transition Concept, James D. Satira Apr 1991

An Erasable Optical Memory Based On Stimulated Electronic Transition Concept, James D. Satira

Electrical & Computer Engineering Theses & Dissertations

Erasable optical memory systems with a high storage density and a large data transfer rate are required for many real time data acquisition systems such as those placed aboard NASA's space born platforms. A new concept for erasable optical memory involving stimulated electronic transitions (SET) will meet these requirements. The SET concept useful in erasable optical storage systems was demonstrated in MgS and SrS doped with Eu and Sm. The optical properties of these materials were studied. The reading and writing wavelengths for these samples were determined to be 950 and 514 nm respectively. The peaks of the emission spectra …

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A Navigation Reference System (Nrs) Using Global Positioning System (Gps) Aiding, Richard D. Stacey Mar 1991

A Navigation Reference System (Nrs) Using Global Positioning System (Gps) Aiding, Richard D. Stacey

Theses and Dissertations

To quantify the performance abilities of existing or proposed navigation systems, the U.S. Air Force has for the last several years compared the performance of the system under test to the performance of a baseline navigation system known as the Completely Integrated Reference Instrumentation System (CIRIS). CIRIS obtains a highly accurate navigation solution by combining the output from three major subsystems: inertial navigation system (INS) information, barometric altitude information, and range and range-rate data from ground transponders which have been precisely surveyed. Although the navigation solution produced by CIRIS is highly accurate, it will soon be inadequate as the standard …

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Model-Based Reasoning In The Detection Of Satellite Anomalies, Ralph W. Dries Dec 1990

Model-Based Reasoning In The Detection Of Satellite Anomalies, Ralph W. Dries

Theses and Dissertations

Automatic fault detection and recovery would be a mandatory requirement for a satellite where some degree of autonomy is required. This thesis reviews some AI techniques used for the detection of satellite anomalies, and concludes that the model-based reasoning paradigm is best suited for automated on-board fault detection because it can cope with situations not necessarily programmed into the knowledge base. Using the Scheme language and its SCOOPS object oriented extension, development of software is described that models the pitch control channel in the attitude and velocity control subsystem of a typical geo-stationary communications satellite. This model is used by …

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Integrated Control Of Thermally Distorted Large Space Antennas, Robert H. Tolson Oct 1990

Integrated Control Of Thermally Distorted Large Space Antennas, Robert H. Tolson

Mechanical & Aerospace Engineering Theses & Dissertations

Studies on controlling the thermal distortion of large space antennae have generally investigated a single orbital position and have optimized actuator locations based on minimizing the RMS surface deviation from the original parabolic shape. One study showed the benefits of directly using far zone electric field characteristics as the performance measure; but, this approach resulted in a nonlinear programming problem. The objective of the current study is to develop an approach to designing a control system that (1) recognizes the time dependence of the distortion and (2) controls variables that are directly related to far field performance in a quadratic …

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Effect Of Viscoplastic Flow Rules On The Initiation And Growth Of Shear Bands At High Strain Rates, R. C. Batra, Chang-Soo Kim Jan 1990

Effect Of Viscoplastic Flow Rules On The Initiation And Growth Of Shear Bands At High Strain Rates, R. C. Batra, Chang-Soo Kim

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Marchand and Duffy have reported detailed measurements of the temperature and strain as a shear band develops in a HY-100 steel. Assuming their torsional tests in thin-wall tubes can be adequately modeled by a viscoplastic block undergoing overall adiabatic simple shearing deformations, we investigate the effect of modeling the viscoplastic response of the material by a.power law, and flow rules proposed by Litonski, Bodner and Partom, and Johnson and Cook. Each of these flow rules is first calibrated by using the test data at a nominal strain-rate of 3300 s-1. Then predictions from the use of these flow rules at …

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Testing Of Solar Collectors By A Standard Method, Harry J. Sauer Jr., Bassem F. Armaly Jan 1978

Testing Of Solar Collectors By A Standard Method, Harry J. Sauer Jr., Bassem F. Armaly

UMR-MEC Conference on Energy / UMR-DNR Conference on Energy

A description of the recently adopted standard for testing solar collectors "ASHRAE STANDARD 93-77, METHOD OF TESTING SOLAR COLLECTORS BASED ON THERMAL PERFORMANCE" is presented. Results from the standard could be used to simulate the transient performance of an installed solar system.

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Ua66/1/2 Scrapbook, Wku Ogden College Of Science & Engineering Jan 1974

Ua66/1/2 Scrapbook, Wku Ogden College Of Science & Engineering

WKU Administration Documents

Scrapbook of clippings, press releases, photographs and other items related to the history of Ogden College of Science & Technology from 1961 to 1974.

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Decision-Directed Detector For Overlapping Pcm/Nrz Signals, Cheng Wang, Thomas L. Noack Jan 1973

Decision-Directed Detector For Overlapping Pcm/Nrz Signals, Cheng Wang, Thomas L. Noack

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A decision-directed (DD) technique for the detection of overlapping PCM/NRZ signals in the presence of white Gaussian noise is investigated. The performance of the DD detector is represented by probability of error PE versus input signal-to-noise ratio (SNR). To examine how much improvement in performance can be achieved with this technique, PE's with and without DD feedback are evaluated in parallel. Further, analytical results are compared with those found by Monte Carlo simulations. The results are shown in good agreement. © 1973, IEEE. All rights reserved.

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