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Full-Text Articles in Engineering
An Investigation Into The Feasibility Of Using A Modern Gravity Gradient Instrument For Passive Aircraft Navigation And Terrain Avoidance, Marshall M. Rogers
An Investigation Into The Feasibility Of Using A Modern Gravity Gradient Instrument For Passive Aircraft Navigation And Terrain Avoidance, Marshall M. Rogers
Theses and Dissertations
Recently, Gravity Gradient Instruments (GGIs) - devices which measure the spatial derivatives of gravity, have improved remarkably due to development of accelerometer technologies. Specialized GGIs are currently flown on aircraft for geological purposes in the mining industries. As such, gravity gradient data is recorded in flight and detailed gradient maps are created after post mission processing. These maps, if stored in a database onboard an aircraft and combined with a GGI, form the basis for a covert navigation system using a map matching process. This system is completely passive and essentially unjammable. To determine feasibility of this method, a GGI …
Velocity Estimate Following Air Data System Failure, Scott A. Mclaren
Velocity Estimate Following Air Data System Failure, Scott A. Mclaren
Theses and Dissertations
Modern high performance aircraft can provide amazing performance due in part to their advanced flight control systems that require gain scheduling to provide optimum performance over a huge flight envelope. In modern fighter aircraft, this gain scheduling is a function of airspeed, and almost all of the research involving aircraft gain scheduling assumes aircraft airspeed to be a known quantity. The purpose of this research was to investigate a method of determining an aircraft’s airspeed in the event of total air data system failure. The process began by combining known aircraft information following an air data system failure to determine …
Autonomous Unmarked Aerial Rendezvous For Automated Aerial Refueling (Aar), Brian S. Burns
Autonomous Unmarked Aerial Rendezvous For Automated Aerial Refueling (Aar), Brian S. Burns
Theses and Dissertations
As unmanned aerial vehicles (UAVs) increase in capability, the ability to refuel them in the air is becoming more critical. Aerial refueling will extend the range, shorten the response times, and extend loiter time of UAVs. Executing aerial refueling autonomously will reduce the command and control, logistics, and training efforts associated with fielding UAV systems. Currently, the Air Force Research Lab is researching the various technologies required to conduct automated aerial refueling (AAR). One of the required technologies is the ability to autonomously rendezvous with the tanker. The goal of this research is to determine the control required to fly …
Development Of A Low-Latency, High Data Rate, Differential Gps Relative Positioning System For Uav Formation Flight Control, Stephen J. Comstock
Development Of A Low-Latency, High Data Rate, Differential Gps Relative Positioning System For Uav Formation Flight Control, Stephen J. Comstock
Theses and Dissertations
In order for Unmanned Aerial Vehicles (UAVs) to be able to fly missions currently performed by manned aircraft, they must be able to conduct in-flight refueling. Additionally, significant fuel savings can be realized if multiple UAV's are able to fly in precise formation and align wingtip vortices. In either case, the precise relative position between the aircraft must be known to an accuracy of only a few centimeters. Previous research at the Air Force Institute of Technology culminated in the development of a relative positioning system for manned aircraft. This thesis presents the development of the next-generation system designed for …
Formation Flight Control For Aerial Refueling, Steven M. Ross
Formation Flight Control For Aerial Refueling, Steven M. Ross
Theses and Dissertations
A controller is designed for an aircraft to autonomously fly formation during aerial refueling. Requirements for a refueling autopilot are stated. A six-degree-of-freedom model is developed for an F-16 lead aircraft and a Learjet LJ-25 wing aircraft. Bare airframe stability of both aircraft is investigated, and stability augmentation is performed. A Matlab Simulink® simulation is built to reproduce the sensor inputs that will be available to the wing aircraft in flight, including disturbances. Control frames are investigated to determine the optimum presentation of the error vector for control during the task of air refueling. Control laws are developed from the …
Nonlinear Regression Methods For Estimation, Eric B. Nelson
Nonlinear Regression Methods For Estimation, Eric B. Nelson
Theses and Dissertations
Regression techniques are developed for batch estimation and applied to three specific areas, namely, ballistic trajectory launch point estimation, adaptive flight control, and radio-frequency target triangulation. Specifically, linear regression with an intercept is considered in detail. An augmentation formulation is developed. Extensions of theory are applied to nonlinear regression as well. The intercept parameter estimate within the linear regression is used to identify the effects of trim change that are associated with the occurrence of a control surface failure. These estimates are used to adjust the inner loop control gains via a feed-forward command, hence providing an automatic reconfigurable retrim …
Characterization Of A Rotary Flat Tail As A Spoiler And Parametric Analysis Of Improving Directional Stability In A Portable Uav, Troy A. Leveron
Characterization Of A Rotary Flat Tail As A Spoiler And Parametric Analysis Of Improving Directional Stability In A Portable Uav, Troy A. Leveron
Theses and Dissertations
The United States Air Force Research Lab, Munitions Directorate, Flight Vehicles, Integration Branch (AFRL/MNAV), has developed a flexible wing micro air vehicle (MAV) to be used with special tactics groups. In keeping with the requirement that this MAV be compact, previous research developed a rotatable tail mechanism which resulted in tail movement similar to that of a bird's tail. In this study the design of this tail was modified to produce a more storable vehicle. The redesign also allowed the tail to deflect upward to large angles, enabling the tail to be used as a spoiler. The aerodynamic effects of …
Full Capability Formation Flight Control, Ryan K. Osteroos
Full Capability Formation Flight Control, Ryan K. Osteroos
Theses and Dissertations
The subject of automatic formation flight control is of current interest to the development of Unmanned Aerial Vehicles (UAV). Previous control approaches have been refined in this work to allow more robust maneuvering and to include a fourth control parameter. The equations of motion for each aircraft as a point mass, expressed in a wind-axis coordinate system, are coupled into differential equations that model the two aircraft system dynamics. Control laws are developed that include proportional and integral action. Gains are determined based on formation performance. Lead maneuvers are simulated and the controller is gauged on its ability to maintain …
Experimental Investigation Into The Aerodynamic Performance Of Both Rigid And Flexible Wing Structured Micro-Air-Vehicles, Anthony M. Deluca
Experimental Investigation Into The Aerodynamic Performance Of Both Rigid And Flexible Wing Structured Micro-Air-Vehicles, Anthony M. Deluca
Theses and Dissertations
The Air Force Research Lab, Munitions Directorate, Eglin Air Force Base, Florida has designed a man-portable carbon-fiber Micro-Air-Vehicle (MA V) used for on-the-spot surveillance by Special Operations Forces (SOF) for enemy reconnaissance as well as post-strike Battle Damage Assessment (BDA).The main goals of this experiment are: 1) characterize the flow quality of the new AFIT 3' x 3' wind tunnel and 2) determine the aerodynamic performance characteristics of the 24" span, 6" chord flexible and rigid wing MA V s. The turbulent intensity of the wind tunnel was approximately 2%. Both MA Vs had an average lift slope within 3.5% …
Outside Loop Control In Asymmetrical Trimmed Flight Conditions, Gary D. Miller
Outside Loop Control In Asymmetrical Trimmed Flight Conditions, Gary D. Miller
Theses and Dissertations
Traditionally flight control systems have used linearized equations of motion solved around a single trim point. This thesis proposes a nested-loop controller directly solved from the equations of motion. The control equations were developed as a solution to asymmetrically trimmed flight conditions. A two-loop design was proposed for the controller. The outer loop modeled the aircraft as a point mass and all forces were balanced to find the aircraft states. The equations input the control variables and output the aircraft states. The inner-loop utilizes the six-degree of freedom model of the aircraft to solve the moment equations. With the input …
A Comparison Of Nonlinear Algorithms To Prevent Pilot-Induced Oscillations Caused By Actuator Rate Limiting, James G. Hanley
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 …
Flight Control Failure Detection And Control Redistribution Using Multiple Model Adaptive Estimation With Filter Spawning, Michael L. Torres Jr.
Flight Control Failure Detection And Control Redistribution Using Multiple Model Adaptive Estimation With Filter Spawning, Michael L. Torres Jr.
Theses and Dissertations
In the current research, the MMAE with Filter Spawning and Control Redistribution (MMAE/FS/CR) are used together to identify failures and apply appropriate corrections. This effort explores the performance of the MMAE/FS/CR in different regions of the flight envelope using model and gain scheduling. The MMAE/FS/CR is able to detect complete and partial actuator/surface failures, as well as complete sensor failures. Once the actuator/surface failure is identified and the effectiveness is determined in the case of partial failures, proper control is applied in order to accomplish the desired pilot command. Improvements in the algorithm are required in order to enhance the …
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 …
Three Dimensional Formation Flight Control, James K. Hall
Three Dimensional Formation Flight Control, James K. Hall
Theses and Dissertations
Automating the control of an aircraft flying in formation necessitates the extension of the theory of formation flight control to allow for three dimensional maneuvers. The formation was modeled as a two-aircraft, leader and wingspan, formation. Both aircraft has its own three dimensional, rotating and translating, Cartesian axes system, with special attention being given to the motion of the leader in relation to the wingspan. The controller operated using the equations of motion expressed in the rotating reference frame of the wing aircraft. The control system has seven states, three inputs and three disturbance signals to model the dynamics of …
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 …
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 …
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 …
Manual Tracking Flight Control With Amplitude And Rate Constrained Dynamic Actuators, Russel B. Miller
Manual Tracking Flight Control With Amplitude And Rate Constrained Dynamic Actuators, Russel B. Miller
Theses and Dissertations
A new control methodology for manual flight control, viz., real-time tracking control, is developed. Amplitude and rate constrained dynamic actuators are considered. Optimal tracking control is made possible by the use of unique reference signal prediction strategies which extrapolate the reference signal over the optimization horizon. A receding horizon, linear-quadratic inner-loop controller is employed in conjunction with an outer-loop nonlinear element. The constraint effects mitigation strategy is to optimally track a modified reference signal which yields feasible actuator commands over the optimization horizon when the pilot demanded reference is too aggressive to be tracked by the inner-loop optimal control law. …
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 …
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 …
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 Quantitative Feedback Theory Fcs Design For The Subsonic Envelope Of The Vista F-16 Including Configuration Variation, Scott N. Phillips
A Quantitative Feedback Theory Fcs Design For The Subsonic Envelope Of The Vista F-16 Including Configuration Variation, Scott N. Phillips
Theses and Dissertations
An aircraft's response to control inputs varies widely throughout its flight envelope. The aircraft configuration also impacts control response through variations in center of gravity and moments of inertia. Designing a flight control system (FCS) to accommodate the full flight envelope and configuration set of an aircraft is clearly a complex undertaking. Quantitative feedback theory (QFT) is a design tool which enables the engineer to attack this task in an efficient way. Although QFT is a robust control design technique, it is an interactive algorithm allowing the engineer full control over compensator order and gain. In this research effort, a …
Advanced Formation Flight Control, Michael J. Veth
Advanced Formation Flight Control, Michael J. Veth
Theses and Dissertations
In this thesis, the formation flight control problem is continued from four previous theses. Automatic formation flight involves controlling multiple aircraft equipped with standard Mach-hold, altitude hold, and heading-hold autopilots to maintain a desired distance from a lead aircraft or "rabbit". Changes in the rabbit's states are treated as disturbances to the system and rejected. Previous research is advanced in the following areas: Higher-order aircraft-autopilot models are included into the design and a new feedback control law is employed, resulting in more accurate simulations. An energy tracking scheme is developed and is shown to reduce wing aircraft energy excursions. Finally, …
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 …
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 …
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 …