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Articles 1 - 28 of 28
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Dynamics And Control Of Tethered Satellite Formations For The Purpose Of Space-Based Remote Sensing, Kurt A. Vogel
Dynamics And Control Of Tethered Satellite Formations For The Purpose Of Space-Based Remote Sensing, Kurt A. Vogel
Theses and Dissertations
This dissertation assesses the utility of tethered satellite formations for the space-based remote sensing mission. Energy dissipation is found to have an adverse effect on foundational rigid body (Likins-Pringle) equilibria. It is shown that a continuously earth-facing equilibrium condition for a fixed-length tethered system does not exist since the spin rate required for the proper precession would not be high enough to maintain tether tension. The range of required spin rates for steady-spin motion is numerically defined here, but none of these conditions can meet the continuously earth-facing criteria. Of particular note is the discovery that applying certain rigid body …
Scaling Flight Tests Of Unmanned Air Vehicles, Jeevani I. Abeygoonewardene
Scaling Flight Tests Of Unmanned Air Vehicles, Jeevani I. Abeygoonewardene
Theses and Dissertations
Increasing technological advances and research interest in unmanned air vehicles (UAVs), have led to the need for having safe, inexpensive and effective means of experimenting with their fight performance and surveillance capabilities. Work has previously been done in areas of controlling, analyzing, and predicting cooperative and autonomous operations of UAVs and other vehicles. In addition, there are well established guidelines for scaling experiments in fluid mechanics, where geometric, kinematic and dynamic similarity is obtained by formulating problems in terms of non dimensional variables using dimensional analysis. However, little or no work has been done in developing experiments or guidelines for …
New Tracking Filter Algorithm Using Input Parameter Estimation, Corey M. Broussard
New Tracking Filter Algorithm Using Input Parameter Estimation, Corey M. Broussard
Theses and Dissertations
A new method for the design of tracking filters for maneuvering targets, based on kinematic models and input signals estimation, is developed. The input signal's level, u is considered a continuous variable and consequently the input estimation problem is posed as a purely parameter estimation problem. Moreover, the application of the new tracking filter algorithm is not contingent on distinguishing maneuvering and non-maneuvering targets, and does not require the detection of maneuver onset. The filter will automatically detect the onset of a maneuver. Furthermore, an estimate of the target's acceleration is also obtained with reasonable precision. This opens the door …
Navigation Using Signals Of Opportunity In The Am Transmission Band, Jonathan A. Mcellroy
Navigation Using Signals Of Opportunity In The Am Transmission Band, Jonathan A. Mcellroy
Theses and Dissertations
Maintaining a precision navigation solution both in a GPS hostile jamming environment and also in a GPS non-compatible terrain area is of great importance. To that end, this thesis evaluates the ability to navigate using signals from the AM band of the electromagnetic spectrum (520 to 1710 kHz). Navigation position estimates are done using multi-lateration techniques similar to GPS. However, pseudoranges are created using Time Difference of Arrival (TDOA) distances between a reference receiver and a mobile receiver, allowing the mobile receiver to obtain absolute position estimates over time. Four methods were developed for estimating the cross-correlation peak within a …
Development And Testing Of A High-Speed Real-Time Kinematic Precise Dgps Positioning System Between Two Aircraft, Christopher J. Spinelli
Development And Testing Of A High-Speed Real-Time Kinematic Precise Dgps Positioning System Between Two Aircraft, Christopher J. Spinelli
Theses and Dissertations
This research involves the design, implementation, and testing of a high-speed, real-time kinematic, precise differential GPS positioning system for use in airborne applications such as automated aerial-refueling and close formation flying. Although many of the current ambiguity resolution techniques use the residuals from the least squares position estimation to determine the true ambiguity set, this thesis presents a novel approach to the ambiguity resolution problem, called the minimum indicator. Instead of assuming the ambiguity set with the lowest residuals is the true set, other special characteristics of the residuals are examined. This increases the confidence that the algorithm has selected …
Optimal Dynamic Soaring For Full Size Sailplanes, Randel J. Gordon
Optimal Dynamic Soaring For Full Size Sailplanes, Randel J. Gordon
Theses and Dissertations
Dynamic soaring is a unique flying technique designed to allow air vehicles to extract energy from horizontal wind shears. Dynamic soaring has been used by seabirds like the Albatross to fly hundreds of kilometers a day across the ocean. Small hobby radio controlled sailplanes have also used this technique to achieve sustained speeds of over 200 miles per hour from just a simple hand toss. Dynamic soaring, however, has never before been studied for use on full size aircraft. The primary goal of this research was to prove or disprove the viability of dynamic soaring for enhancing a full size …
An Investigation Of The Effects Of Boundary Avoidance On Pilot Tracking, Randy D. Warren
An Investigation Of The Effects Of Boundary Avoidance On Pilot Tracking, Randy D. Warren
Theses and Dissertations
Pilot-Involved Oscillations (PIOs) remain a significant issue in the design, testing and operations of aerospace vehicles. Traditional methods for predicting, describing, and analyzing these events have provided the community with improved methods for minimizing the occurrences of PIOs. However, these events continue to occur over a wide range of aerospace vehicle types and over a wide range of pilot acumen. The introduction of boundary avoidance tracking (BAT) by Mr. William Gray in 2004 added a missing piece to the PIO puzzle. This theory presented that PIOs may result from increasing pilot gain resulting not from maintaining a specified condition, but …
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 …
Fusion Of Imaging And Inertial Sensors For Navigation, Michael J. Veth
Fusion Of Imaging And Inertial Sensors For Navigation, Michael J. Veth
Theses and Dissertations
The motivation of this research is to address the limitations of satellite-based navigation by fusing imaging and inertial systems. The research begins by rigorously describing the imaging and navigation problem and developing practical models of the sensors, then presenting a transformation technique to detect features within an image. Given a set of features, a statistical feature projection technique is developed which utilizes inertial measurements to predict vectors in the feature space between images. This coupling of the imaging and inertial sensors at a deep level is then used to aid the statistical feature matching function. The feature matches and inertial …
Robot Localization Using Visual Image Mapping, Carrie D. Crews
Robot Localization Using Visual Image Mapping, Carrie D. Crews
Theses and Dissertations
One critical step in providing the Air Force the capability to explore unknown environments is for an autonomous agent to be able to determine its location. The calculation of the robot's pose is an optimization problem making use of the robot's internal navigation sensors and data fusion of range sensor readings to find the most likely pose. This data fusion process requires the simultaneous generation of a map which the autonomous vehicle can then use to avoid obstacles, communicate with other agents in the same environment, and locate targets. Our solution entails mounting a Class 1 laser to an ERS-7 …
Optimal Geometric Deployment Of A Ground Based Pseudolite Navigation System To Track A Landing Aircraft, Matthew P. Crawford
Optimal Geometric Deployment Of A Ground Based Pseudolite Navigation System To Track A Landing Aircraft, Matthew P. Crawford
Theses and Dissertations
With much of the military and civilian communities becoming dependent on GPS technology to navigate it has become imperative that the navigation systems be tested in situations in which GPS does not work. This testing is especially necessary for precise tasks such as landing an aircraft. Currently, research is being conducted into using a pseudolite-based reference system to use as a truth model for the GPS jamming test. Pseudolite systems have been proven to provide sub-centimeter level accuracy in the horizontal plane; however in the vertical plane the position error is still in the decimeter to meter level range. This …
Characterization Of Uav Performance And Development Of A Formation Flight Controller For Multiple Small Uavs, Patrick A. Mccarthy
Characterization Of Uav Performance And Development Of A Formation Flight Controller For Multiple Small Uavs, Patrick A. Mccarthy
Theses and Dissertations
The Air Force Institute of Technology's (AFIT) Advanced Navigation Technology (ANT) Center has recently delved into the research topic of small Unmanned Aerial Vehicles (UAV). One area of particular interest is using multiple small UAVs cooperatively to improve mission efficiency, as well as perform missions that couldn't be performed using vehicles independently. However, many of these missions require that the UAVs operate in close proximity of each other. This research lays the foundation required to use the ANT Center's UAVs for multi-vehicle missions (e.g. cooperatively) by accomplishing two major goals. First, it develops test procedures that can be used to …
An Investigation Into Robust Wind Correction Algorithms For Off-The Shelf Unmanned Aerial Vehicle Autopilots, Brent K. Robinson
An Investigation Into Robust Wind Correction Algorithms For Off-The Shelf Unmanned Aerial Vehicle Autopilots, Brent K. Robinson
Theses and Dissertations
The research effort focuses on developing methods to design efficient wind correction algorithms to "piggyback" on current off-the-shelf Unmanned Aerial Vehicle (UAV) autopilots. Autonomous flight is certainly the near future for the aerospace industry and there exists great interest in defining a system that can guide and control aircraft with high levels of accuracy. The primary systems required to command the vehicles are already in place, but with only moderate abilities to adjust for dynamic environments (i.e. wind effects), if at all. The goal of this research is to develop a systematic procedure for implementing efficient and robust wind effects …
Situational Awareness And Synthetic Vision For Unmanned Aerial Vehicle Flight Testing, Joseph M. Dugan
Situational Awareness And Synthetic Vision For Unmanned Aerial Vehicle Flight Testing, Joseph M. Dugan
Theses and Dissertations
The Advanced Navigation Technology (ANT) Center at the Air Force Institute of Technology (AFIT) is currently exploring ways to develop and advance the employment of autonomous Unmanned Aerial Vehicles (UAV) by the Department of Defense for military purposes. The research in this thesis describes the development of a tool that enhances situational awareness and provides synthetic vision in a program called the Aviator Visual Display Simulator (AVDS) during UAV flight. During flight testing, the Situational Awareness and Synthetic Vision Relay Tool (SASVRT) developed provides the test coordinator and pilot, as well as the safety observers, with the most pertinent information …
Evaluation Of Energy Costs And Error Performance Of Range-Aware Anchor-Free Localization Algorithms For Wireless Sensor Networks, Gustav Julio Jordt
Evaluation Of Energy Costs And Error Performance Of Range-Aware Anchor-Free Localization Algorithms For Wireless Sensor Networks, Gustav Julio Jordt
Theses and Dissertations
This research examines energy and error tradeoffs in Anchor-Free Range-Aware Wireless Sensor Network (WSN) Localization algorithms. A concurrent and an incremental algorithm (Anchor Free Localization (AFL) and Map Growing) are examined under varying network sizes, densities, deployments, and range errors. Despite current expectations, even the most expensive configurations do not expend significant battery life (at most 0.4%), implying little energy can be conserved during localization. Due to refinement, AFL is twice as accurate, using 6 times the communication. For both, node degree affects communication most. As degree increases, Map Growing communication increases, while AFL transmissions drop. Nodes with more neighbors …
Evaluating The Correlation Characteristics Of Arbitrary Am And Fm Radio Signals For The Purpose Of Navigation, Bryan S. Kim
Evaluating The Correlation Characteristics Of Arbitrary Am And Fm Radio Signals For The Purpose Of Navigation, Bryan S. Kim
Theses and Dissertations
The Global Positioning System (GPS) provides position estimates on the Earth at anytime, anywhere and in any weather. However, to provide robust positioning, GPS requires an unobstructed path to satellite signals. As such, GPS performance generally degrades or becomes non-existent in environments such as large urban areas. This research investigates and analyzes the correlation characteristics of arbitrary AM and FM radio signals for the purpose of navigation. Simulations are conducted with different combinations of correlation methods (`fixed' or `varying'), modulation types (AM or FM), and signal types (song or voice). Out of the eight different variations considered, only two provided …
A Minimum Effort Control Approach To Guided Munition Path Planning, Jeffrey M. Borkowski
A Minimum Effort Control Approach To Guided Munition Path Planning, Jeffrey M. Borkowski
Theses and Dissertations
An advance in the development of smart munitions entails autonomously modifying target selection during flight to maximize the value of the target being destroyed. Target identification and classification provides a basis for target value, which is used in conjunction with multi-target tracks to determine an optimal aim point for the munition. A unique guidance law can be constructed that exploits attribute and kinematic data from an onboard video sensor. This thesis develops an innovative path planning algorithm that provides an obstacle avoidance function while navigating the munition toward the highest value target. The foundation of this path planning method is …
Methods For Aiding Height Determination In Pseudolite-Based Reference Systems Using Batch Least-Squares Estimation, John H. R. Amt
Methods For Aiding Height Determination In Pseudolite-Based Reference Systems Using Batch Least-Squares Estimation, John H. R. Amt
Theses and Dissertations
There are many situations in which GPS is either unable to provide the desired level of accuracy or is unavailable. Use of a pseudolite-based reference system for navigation can be a means for positioning during these times. While there are advantages in using a pseudolite-based reference system, there are still implementation issues and deficiencies that must be addressed. In many cases, a pseudolite system with ground-based transmitters has difficulty determining the height of the receiver accurately. This is due to the poor vertical observability inherent in the geometry of the system. A common approach in naval applications for solving the …
Bio-Inspired, Odor-Based Navigation, Maynard John Porter Iii
Bio-Inspired, Odor-Based Navigation, Maynard John Porter Iii
Theses and Dissertations
The ability of moths to locate a member of the opposite sex, by tracking a wind-borne plume of odor molecules, is an amazing reality. Numerous scenarios exist where having this capability embedded into ground-based or aerial vehicles would be invaluable. The main crux of this thesis investigation is the development of a navigation algorithm which gives a UAV the ability to track a chemical plume to its source. Inspiration from the male moth's, in particular Manduca sexta, ability to successfully track a female's pheromone plume was used in the design of both 2-D and 3-D navigation algorithms. The algorithms were …
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 …
Estimation And Mitigation Of Unmodeled Errors For A Pseudolite Based Reference System, Jeremiah A. Shockley
Estimation And Mitigation Of Unmodeled Errors For A Pseudolite Based Reference System, Jeremiah A. Shockley
Theses and Dissertations
Current flight reference systems rely heavily on the Global Positioning System (GPS), causing susceptibility to GPS jamming. Additionally, an increasing number of tests involve jamming the GPS signal. A need exists to develop a system capable of GPS-level accuracy during these outages. One promising solution is a ground-based pseudolite system capable of delivering sub-centimeter level accuracy, yet operating at non-GPS frequencies. This thesis attempts to determine the unknown errors in the Locata system, one such pseudolite-based system, to achieve the accuracy required. The development of a measurement simulation tool along with a Kalman filter algorithm provides confirmation of filter performance …
Evaluation And Analysis Of Node Localization Power Cost In Ad-Hoc Wireless Sensor Networks With Mobility, Brian A. Sessler
Evaluation And Analysis Of Node Localization Power Cost In Ad-Hoc Wireless Sensor Networks With Mobility, Brian A. Sessler
Theses and Dissertations
One of the key concerns with location-aware Ad-hoc Wireless Sensor Networks (AWSNs) is how sensor nodes determine their position. The inherent power limitations of an AWSN along with the requirement for long network lifetimes makes achieving fast and power-efficient localization vital. This research examines the cost (in terms of power) of network irregularities on communications and localization in an AWSN. The number of data bits transmitted and received are significantly affected by varying levels of mobility, node degree, and network shape. The concurrent localization approach, used by the APS-Euclidean algorithm, has significantly more accurate position estimates with a higher percentage …
A Monocular Vision Based Approach To Flocking, Brian Kirchner
A Monocular Vision Based Approach To Flocking, Brian Kirchner
Theses and Dissertations
Flocking is seen in nature as a means for self protection, more efficient foraging, and other search behaviors. Although much research has been done regarding the application of this principle to autonomous vehicles, the majority of the research has relied on GPS information, broadcast communication, an omniscient central controller, or some other form of "global" knowledge. This approach, while effective, has serious drawbacks, especially regarding stealth, reliability, and biological grounding. This research effort uses three Pioneer P2-AT8 robots to achieve flocking behavior without the use of global knowledge. The sensory inputs are limited to two cameras, offset such that the …
Performance Analysis Of A Cooperative Search Algorithm For Multiple Unmanned Aerial Vehicles Under Limited Communication Conditions, Kevin M. Morris
Performance Analysis Of A Cooperative Search Algorithm For Multiple Unmanned Aerial Vehicles Under Limited Communication Conditions, Kevin M. Morris
Theses and Dissertations
This research investigates the impacts of realistic wireless communications upon a group of unmanned aerial vehicles (UAVs) utilizing a distributed search algorithm. The UAVs are used to survey an area for mobile targets and they require communication to cooperatively locate the targets. The mobile targets do not continually radiate energy, which exacerbates the search effort; a UAV could fly directly over a target and not detect it. A simulation of cooperative UAVs is implemented using the OPNET Modeler network simulation tool. The search performance of a group of UAVs is observed when communication range, data rate, and the number of …
Application Of Fuzzy State Aggregation And Policy Hill Climbing To Multi-Agent Systems In Stochastic Environments, Dean C. Wardell
Application Of Fuzzy State Aggregation And Policy Hill Climbing To Multi-Agent Systems In Stochastic Environments, Dean C. Wardell
Theses and Dissertations
Reinforcement learning is one of the more attractive machine learning technologies, due to its unsupervised learning structure and ability to continually even as the operating environment changes. Applying this learning to multiple cooperative software agents (a multi-agent system) not only allows each individual agent to learn from its own experience, but also opens up the opportunity for the individual agents to learn from the other agents in the system, thus accelerating the rate of learning. This research presents the novel use of fuzzy state aggregation, as the means of function approximation, combined with the policy hill climbing methods of Win …
Development Of Autonomous Unmanned Aerial Vehicle Platform: Modeling, Simulating, And Flight Testing, Nidal M. Jodeh
Development Of Autonomous Unmanned Aerial Vehicle Platform: Modeling, Simulating, And Flight Testing, Nidal M. Jodeh
Theses and Dissertations
The Advanced Navigation Technology (ANT) Center at the Air Force Institute of Technology (AFIT) conducts extensive research in advanced guidance, navigation, and control to exploit the full potential of autonomous Unmanned Aerial Vehicles (UAV). The research in this thesis describes a UAV research platform developed to support the ANT Center's goals. This platform is now the bedrock for UAV simulation and local flight test at AFIT. The research has three major components. The first component is development of a physical, inertial, and aerodynamic model representing an existing aircraft. A systematic analysis of the airframe leads to a complete geometric, inertial, …
Image Processing Resource Allocation Methods For Multi-Target Tracking Of Dismounted Targets In Urban Environments, Jonathan P. Champion
Image Processing Resource Allocation Methods For Multi-Target Tracking Of Dismounted Targets In Urban Environments, Jonathan P. Champion
Theses and Dissertations
Dismounted targets can be tracked in urban environments with video sensors. Real-time systems are unable to process all of the imagery, demanding some method for prioritization of the processing resources. Furthermore, various segmentation algorithms exist within image processing, each algorithm possesses unique capabilities, and each algorithm has an associated computational cost. Additional complexity arises in the prioritization problem when targets become occluded (e.g., by a building) and when the targets are intermixed with other dismounted entities. This added complexity leads to the question "which portions of the scene warrant both low cost and high cost processing?" The approach presented in …
Characterizing The Impact Of Precision Time And Range Measurements From Two-Way Time Transfer Systems On Network Differential Gps Position Solutions, Kendra L. B. Cook
Characterizing The Impact Of Precision Time And Range Measurements From Two-Way Time Transfer Systems On Network Differential Gps Position Solutions, Kendra L. B. Cook
Theses and Dissertations
Precise positioning plays an important role for both military and civilian users, from cell phones and OnStar to precision munitions and swarms of UAVs. Many applications require precise relative positioning of a network of vehicles (such as aircraft, tanks, troops, etc). Currently, the primary means for performing precise positioning is by using the Global Positioning System (GPS), and although GPS has become commonplace in today’s society, there are still limitations affecting the system. Recent advances in dynamic Two-Way Time Transfer (TWTT) have potentially provided a means to improve precise relative positioning accuracy over differential GPS (DGPS)-only approaches. TWTT is a …