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Articles 31 - 56 of 56
Full-Text Articles in Aerospace Engineering
Improving Uav Handling Qualities Using Time Delay Compensation, Andrew J. Thurling
Improving Uav Handling Qualities Using Time Delay Compensation, Andrew J. Thurling
Theses and Dissertations
This research investigated control loop time delay and its effect on UAV handling qualities. Compensation techniques to improve handling qualities in the presence of varying amounts of time delay were developed and analyzed. One technique was selected and successfully flight-tested on a UAV. Flight-testing occurred at a constant flight condition with varying levels of additional time delay introduced into the control loop. Research pilots performed a pitch tracking task and gave Cooper-Harper ratings and comments. Tracking errors were used as a quantitative measure of Pilot/Display/UAV system performance. Predictive pitch compensation was found to significantly reduce pilot workload and improve Cooper-Harper …
Modeling Piezoceramic Twist Actuation In Single-Cell Anisotropic Torque Box Of Low-Observable Uav Wing, Peter Cseke Jr.
Modeling Piezoceramic Twist Actuation In Single-Cell Anisotropic Torque Box Of Low-Observable Uav Wing, Peter Cseke Jr.
Theses and Dissertations
The reduction of an aircraft's radar cross section can increase its survivability in hostile airspace by making it more difficult to locate and track by enemy radar. Replacing articulated flight control surfaces with adaptive controls will reduce surface discontinuities, and enhance low observability. Actuation of the aerodynamic surfaces is achieved by an electric field applied to PZT actuators embedded in the top and bottom skins, creating differential strain and shear in the host substrate. This creates torsion about the elastic axis, and a change in the wing lift coefficient. The torsion of the designed baseline UAV's wing torquebox was modeled …
A Nonlinear Pre-Filter To Prevent Departure And/Or Pilot-Induced Oscillations (Pio) Due To Actuator Rate Limiting, Michael J. Chapa
A Nonlinear Pre-Filter To Prevent Departure And/Or Pilot-Induced Oscillations (Pio) Due To Actuator Rate Limiting, Michael J. Chapa
Theses and Dissertations
Closed loop instability caused by excess phase lag induced by actuator rate limiting has been suspected in many aircraft departures from controlled flight and pilot-induced oscillations (PIO). As part of the joint Air Force Institute of Technology Test Pilot School (AFITITPS) program, a nonlinear rate limiter pre-filter (RLPF) was developed to minimize the phase lag induced by rate limiting. RLFF performance was evaluated inside the feedback path, but primary emphasis was on the pilot command path. Closed loop computer and motion-based flight simulation were conducted to prepare for the flight test. The HAVE FILTER flight test project was flown using …
Approximate Analytical Relationships For Linear Optimal Aeroelastic Flight Control Laws, Ayman Hamdy Kassem
Approximate Analytical Relationships For Linear Optimal Aeroelastic Flight Control Laws, Ayman Hamdy Kassem
Mechanical & Aerospace Engineering Theses & Dissertations
This dissertation introduces new methods to uncover functional relationships between design parameters of a contemporary control design technique and the resulting closed-loop properties. Three new methods are developed for generating such relationships through analytical expressions: the Direct Eigen-Based Technique, the Order of Magnitude Technique, and the Cost Function Imbedding Technique. Efforts concentrated on the linear-quadratic state-feedback control-design technique applied to an aeroelastic flight control task. For this specific application, simple and accurate analytical expressions for the closed-loop eigenvalues and zeros in terms of basic parameters such as stability and control derivatives, structural vibration damping and natural frequency, and cost function …
Modern Flight Control Design, Implementation, And Flight Test, Phillip T. Edwards
Modern Flight Control Design, Implementation, And Flight Test, Phillip T. Edwards
Theses and Dissertations
This thesis addresses the application issues raised implementing flight control designs derived from optimal control theory and the challenges in obtaining acceptable handling qualities when using these techniques. Using the USAF TPS FCS project as the controller architecture, four controllers were designed using classical methods, and H2, H3, and mixed H2/H optimal control theory. These designs were implemented in the Calspan VSS II Learjet, simulating unstable aircraft longitudinal dynamics and a limited handling qualities flight test evaluation was performed. The design phase found the optimal control techniques, as applied, difficult to design to handling qualities specifications. The H2, H3 and …
Optimal Formation Flight Control, Shawn B. Mccamish
Optimal Formation Flight Control, Shawn B. Mccamish
Theses and Dissertations
Automatic formation flight involves controlling multiple wing aircraft equipped with standard Mach-hold, altitude-hold, and heading-hold autopilots in order to maintain a desired position relative to a lead aircraft throughout formation maneuvers. Changes in the lead aircraft's states, including formation heading, velocity, altitude, and geometry changes, are treated as disturbance and are rejected by the formation flight control system. The work in this thesis is a continuation of five previous theses, dealing with the design of formation flight control systems. The goal of the optimal formation flight control design is to achieve robust formation maintenance in the face of formation maneuvers …
Design Of Flight Control Laws For Aircraft With Flexible Wings Using Quantitative Feedback Theory, Christina L. Osmon
Design Of Flight Control Laws For Aircraft With Flexible Wings Using Quantitative Feedback Theory, Christina L. Osmon
Theses and Dissertations
Aircraft composed of lightweight composite materials are extremely enticing since their structural weight is greatly reduced. However, the control of these aircraft is complicated by the resultant flexibility of the wings. Two avenues of approach are possible; stiffen the wings thus losing some of the weight reduction benefits, or design the lateral/directional flight control system cognizant of the wing's flexibility. In this thesis the second approach is taken. The design of three lateral/directional flight control systems for the sub-sonic flight envelope of the F-18 is presented. The Quantitative Feedback Theory (QFT) robust control design technique is used. These designs incorporate …
Flight Control Design Using Mixed H2/Μ Optimization, Douglas D. Decker
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 …
Applications Of ℓ1 And Mixed H2/ℓ1 Optimization, Mark S. Spillman
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.
A Gain Scheduling Optimization Method Using Genetic Algorithms, Robert C. Martin Iv
A Gain Scheduling Optimization Method Using Genetic Algorithms, Robert C. Martin Iv
Theses and Dissertations
Gain scheduling. the traditional method of providing adaptive control to a nonlinear system, has long been an ad hoc design process. Until recently; little theoretical guidance directed this practitioners' art. For this reason a systematic study of this design process and its potential for optimization has never been accomplished. Additionally, the nonlinearities and the large search space involved in gain scheduling also precluded such an optimization study. Traditionally, the gain scheduling process has been some variation of a linear interpolation between discrete design points. By using powerful non-traditional optimization tools such as genetic algorithms there are ways of improving this …
Direct Reduced Order Mixed H2/H∞ Control For The Short Take-Off And Landing-Maneuver Technology Demonstrator (Stol-Mtd), William C. Reigelsperger Jr.
Direct Reduced Order Mixed H2/H∞ Control For The Short Take-Off And Landing-Maneuver Technology Demonstrator (Stol-Mtd), William C. Reigelsperger Jr.
Theses and Dissertations
One of the conclusions from the STOL/MTD program was the need for a multivariable method of designing controllers of low order. This research investigated that problem by studying reduced order mixed H2/H∞ control theory applied to the STOL Landing configuration which employs both thrust vectoring and the use of a canard. Model matching techniques were used to obtain responses that met handling qualities criteria and reduced pilot workload by decoupling pitch rate and velocity commands. The time responses were found through nonlinear simulation and showed that the full order designs did match the ideal models very well …
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
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 …
Automation Of Formation Flight Control, Vincent P. Reyna
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 …
Exploring Qdes As A Tool For Determining Limits Of Achievable Performance In Aircraft Design, Mark F. Reidinger
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 …
Design Of A Flight Controller For An Unmanned Research Vehicle With Control Surface Failures Using Quantitative Feedback Theory, Mark S. Keating
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. …
Design Of A Subsonic Envelope Flight Control System For The Vista F-16 Using Quantitative Feedback Theory, Odell R. Reynolds
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.
Evaluation Of Moderate Angle Of Attack Roll Of A Dual Engine, Thrust Vectoring Aircraft Using Quantitative Feedback Theory, Kevin E. Boyum
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 …
Neural Networks For Dynamic Flight Control, Ronald E. Setzer
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 …
Development Of An Air-To-Air Refueling Automatic Flight Control System Using Quantitative Feedback Theory, Dennis W. Trosen
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 …
Helicopter Flight Control System Design Using The Linear Quadratic Regulator For Robust Eigenstructure Assignment, Dempsey D. Solomon
Helicopter Flight Control System Design Using The Linear Quadratic Regulator For Robust Eigenstructure Assignment, Dempsey D. Solomon
Theses and Dissertations
This thesis applied modern, multi-variable control design techniques, via a FORTRAN computer algorithm, to U.S. Army helicopter models in hovering flight conditions. Eigenstructure assignment and Linear Quadratic Regulator (LQR) theory are used to achieve enhanced closed loop performance and stability characteristics with full state feedback. The addition of cross coupling weights to the standard LQR performance index is specifically addressed. A desired eigenstructure is chosen with a goal of reduced pilot workload via performance qualities requirements. Cross coupling weighting is shown to provide greater flexibility in achieving a desired closed loop eigenstructure. While the addition of cross coupling weighting is …
Improvements To Lqgi/Ltr Methodology For Plants With Lightly Damped Or Low Frequency Poles, An-Chi Ju
Improvements To Lqgi/Ltr Methodology For Plants With Lightly Damped Or Low Frequency Poles, An-Chi Ju
Theses and Dissertations
LQG/LTR design has a tendency to invert the plant's dynamics, which is undesirable if there are plant poles near the imaginary axis. In this study, Static Output Feedback (SOF) is applied to reassign plant poles before LQG/LTR is applied. Alternatively, Robust Eigenstructure Assignment (REA) was used to design the target loop transfer function with an ideal eigenstructure to avoid the undesirable cancellations. Both methods were applied to several aircraft design problems. Results showed that the methods can be effectively used so that the LQG/LTR design has improved stability and performance; however, it was found that each method had strengths and …
Strategies For Optimal Control Design Of Normal Acceleration Command Following On The F-16, James C. Baird
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 …
Analysis Of The Effects Of Removing Nose Ballast From The F-15 Eagle, Richard L. Bennett
Analysis Of The Effects Of Removing Nose Ballast From The F-15 Eagle, Richard L. Bennett
Theses and Dissertations
This study investigated the results of removing lead ballast from the nose section of the F-15 Air Superiority fighter. The goal of the investigation was to determine if aircraft handling qualities remained acceptable with the ballast removed, and also to determine what improvements in aircraft nose pointing authority resulted. Actual F-15 weight reports were used to calculate the worst case aft center of gravity location shift due to the ballast removal. Several configurations with different center of gravity locations (based on various amounts of lead weights removed) were used for comparison to the baseline aircraft. Moments of inertia were calculated …
Development Of High Angle Of Attack Control Laws For An Unstable, Non- Minimum Phase Aircraft Using Variations Of The Quantitative Feedback Technique, Mark A. Mcclure
Development Of High Angle Of Attack Control Laws For An Unstable, Non- Minimum Phase Aircraft Using Variations Of The Quantitative Feedback Technique, Mark A. Mcclure
Theses and Dissertations
This thesis discusses the application of variations of the quantitative feedback technique to a control problem with unstable, non-minimum phase plants. The X-29A research aircraft is used as the basis for developing a set of representative linearized aircraft dynamics models, which are modified to allow for the use of differential canard control inputs for enhanced maneuverability at extreme angles of attack. A specialized design approach is presented to develop frequency dependent weighting matrices, and the shortcomings of traditional methods are discussed. Four independent longitudinal compensators are developed by first designing loop transmission functions. Discussion is provided that addresses the limitations …
Model Identification And Control System Design For The Lambda Unmanned Research Vehicle, Gerald A. Swift
Model Identification And Control System Design For The Lambda Unmanned Research Vehicle, Gerald A. Swift
Theses and Dissertations
Research for this thesis centered on the Lambda Unmanned Research Vehicle (URV), an asset of the Flight Dynamics Directorate, Wright Laboratory Patterson AFB. The following tasks were accomplished: (1) a linear, state-space, small perturbation model was developed for both the longitudinal and lateral directional dynamics of the vehicles, and (2) pitch rate roll rate, and yaw rate flight controllers were designed using classical and multivariable feedback methods. The parameters of the linear, state space, small perturbation model were estimated from actual flight test data. Digital Datcom was first used to estimate stability and control derivatives from the vehicle's geometry. Maximum …
An Approach For Including Reliability In Control System Designs, Ime Isaac Akpan
An Approach For Including Reliability In Control System Designs, Ime Isaac Akpan
Mechanical & Aerospace Engineering Theses & Dissertations
An approach is developed for non-catastrophic control component failure accommodation for large space structures. Reliability is considered for both the control configuration (i.e., selecting actuator locations over an admissible set) and the ultimate operation of the system. The approach presented is to construct a measure of performance that indicates the absolute goal of the system, and for a given structural design, to determine the lowest achievable cost conditional upon the failure states of the system (i.e., which actuators are operational). These costs are then weighted and summed to provide an overall system performance measure. This expected performance measure is then …