Navigation, Guidance, Control and Dynamics Commons^™

Polarimetric Enhancements To Electro-Optical Aided Navigation Techniques, Jeremiah D. Johnson

Theses and Dissertations

Navigation in indoor and urban environments by small unmanned systems is a topic of interest for the Air Force. The Advanced Navigation Technology Center at the Air Force Institute of Technology is continually looking for novel approaches to navigation in GPS deprived environments. Inertial sensors have been coupled with image aided concepts, such as feature tracking, with good results. However, feature density in areas with large, flat, smooth surfaces tends to be low. Polarimetric sensors have been used for surface reconstruction, surface characterization and outdoor navigation. This thesis combines aspects of some of these algorithms along with a realistic, micro-facet …

Long Term Quadrotor Stabilization, Nicolas S. Hamilton

Theses and Dissertations

The work of this thesis focuses on the IMU and getting the best performance possible out of the IMU to achieve better long term stability and a better navigation solution. This is done in two ways. First, the IMU accelerometer output is examined to determine if it is possible to use accelerometers to determine attitude. If the quadrotor is stationary or moving at constant velocity, the roll and pitch angles can be determined. Additionally, the accelerometers can be used to determine angular accelerations and angular rates which are integrated to determine heading. The second approach models the quadrotor and uses …

Non-Gps Navigation Using Vision-Aiding And Active Radio Range Measurements, Erich H. Lichtfuss

Theses and Dissertations

The military depends on the Global Positioning System (GPS) for a wide array of advanced weaponry guidance and precision navigation systems. Lack of GPS access makes precision navigation very difficult. Inclusion of inertial sensors in existing navigation systems provides short-term precision navigation, but drifts significantly over long-term navigation. This thesis is motivated by the need for inertial sensor drift-constraint in degraded and denied GPS environments. The navigation system developed consists of inertial sensors, a simulated barometer, three Raytheon DH500 radios, and a stereo-camera image-aiding system. The Raytheon DH500 is a combat communication radio which also provides range measurements between radios. …

Vision Aided Inertial Navigation System Augmented With A Coded Aperture, Jamie R. Morrison

Theses and Dissertations

Navigation through an indoor environment is a formidable challenge for an autonomous micro air vehicle. One solution is a vision aided inertial navigation system using depth-from-defocus to determine heading and depth to features in the scene. Depth-from-defocus uses a focal blur pattern to estimate depth. As depth increases, the observable change in the focal blur is generally reduced. Consequently, as the depth of a feature to be measured increases, the measurement performance decreases. The Fresnel zone plate, used as an aperture, introduces multiple focal planes. Interference between the multiple focal planes produce changes in the aperture that extend the depth …

Coupling Vanishing Point Tracking With Inertial Navigation To Estimate Attitude In A Structured Environment, Dayvid Prahl

Theses and Dissertations

This research aims to obtain accurate and stable estimates of a vehicle's attitude by coupling consumer-grade inertial and optical sensors. This goal is pursued by first modeling both inertial and optical sensors and then developing a technique for identifying vanishing points in perspective images of a structured environment. The inertial and optical processes are then coupled to enable each one to aid the other. The vanishing point measurements are combined with the inertial data in an extended Kalman filter to produce overall attitude estimates. This technique is experimentally demonstrated in an indoor corridor setting using a motion profile designed to …

Effects Of Cyclic Prefix Jamming Versus Noise Jamming In Ofdm Signals, Amber L. Scott

Theses and Dissertations

Signal jamming of an orthogonal frequency-division multiplexing (OFDM) signal is simulated in MATLAB. Two different means of jamming are used to see, which is a more efficient way to disrupt a signal using the same signal power. The first way is a basic additive white Gaussian noise (AWGN) jammer that equally jams the entire signal. The second way is an AWGN jammer that targets only the cyclic prefix (CP) of the signal. These two methods of jamming are simulated using different channel models and unknowns to get varying results. The three channel models used in the simulations are the no …

Multiple Integrated Navigation Sensors For Improving Occupancy Grid Fastslam, Christopher P. Weyers

Theses and Dissertations

An autonomous vehicle must accurately observe its location within the environment to interact with objects and accomplish its mission. When its environment is unknown, the vehicle must construct a map detailing its surroundings while using it to maintain an accurate location. Such a vehicle is faced with the circularly defined Simultaneous Localization and Mapping (SLAM) problem. However difficult, SLAM is a critical component of autonomous vehicle exploration with applications to search and rescue. To current knowledge, this research presents the first SLAM solution to integrate stereo cameras, inertial measurements, and vehicle odometry into a Multiple Integrated Navigation Sensor (MINS) path. …

Kernelized Locality-Sensitive Hashing For Fast Image Landmark Association, Mark A. Weems

Theses and Dissertations

As the concept of war has evolved, navigation in urban environments where GPS may be degraded is increasingly becoming more important. Two existing solutions are vision-aided navigation and vision-based Simultaneous Localization and Mapping (SLAM). The problem, however, is that vision-based navigation techniques can require excessive amounts of memory and increased computational complexity resulting in a decrease in speed. This research focuses on techniques to improve such issues by speeding up and optimizing the data association process in vision-based SLAM. Specifically, this work studies the current methods that algorithms use to associate a current robot pose to that of one previously …

Signals Of Opportunity Navigation Using Wi-Fi Signals, Wilfred E. Noel

Theses and Dissertations

Since GPS is generally limited to areas with clear sky view, additional methods of navigation are currently being explored. This thesis explores navigation using Signals of Opportunity(SoOP). The signals chosen for evaluation in this thesis are the common Internet IEEE 802.11a/g signals, or Wi-Fi. This thesis presents SoOP navigation based on cross-correlations of received data from multiple Wi-Fi stations. It shows the effectiveness of the methods using collected Wi-Fi signals in a real-world environment. By using simple statistical representations of collected data in large groups, or windows, cross-correlation calculations can produce timing offsets between simulated stations. The timing offsets, or …

Image Dependent Relative Formation Navigation For Autonomous Aerial Refueling, James M. Howard

Theses and Dissertations

This research tests the feasibility, accuracy, and reliability of a predictive rendering and holistic comparison algorithm with use of an optical sensor to provide relative distance and position behind a lead or tanker aircraft. Using an accurate model of a tanker, an algorithm renders image(s) for comparison with actual collected images by a camera installed on the receiver aircraft. Based on this comparison, information used to create the rendered image(s) is used to provide the relative navigation solution required for autonomous air refueling. Given enough predicted images and processing time, this approach should reliably find an accurate solution. Building on …

Integration Of Aeroservoelastic Properties Into The Nasa Dryden F/A-18 Simulator Using Flight Data From The Active Aeroelastic Wing Program, Alexander Wong Chin

Master's Theses

Aircraft structures have varying stiffness levels making them flexible. Consequently, this elastic property becomes increasingly important at high speeds affecting the flight dynamics of the aircraft.  In high speed aircraft such as the F/A-18, elastic structural properties must be accounted for to ensure confidence in predicted flight dynamics in order to avoid adverse aeroelastic phenomena throughout flight.

Data from the F/A-18 Active Aeroelastic Wing (AAW) program was used to create aeroservoelastic (ASE) models at varying flight conditions. The discretized ASE models were integrated into the NASA Dryden F/A-18 simulator in parallel with the traditional 6-DOF (degrees-of-freedom) flight dynamics calculations to …

Modeling And Control Of Space Vehicles With Fuel Slosh Dynamics, Mahmut Reyhanoglu

Physical Sciences - Daytona Beach

"Ever since the launch of the early high-efficiency rockets, controlling liquid fuel slosh within a launch vehicle has been a major design concern. Moreover, with today's large and complex spacecraft, a substantial mass of fuel is necessary to place them into orbit and to perform orbital maneuvers."--from the book's introduction

Terminal Guidance Of Autonomous Parafoils In High Wind-To-Airspeed Ratios, Nathan Slegers, O A. Yakimenko

Faculty Publications - Biomedical, Mechanical, and Civil Engineering

Autonomous precision placement of parafoils is challenging because of their limited control authority and sensitivity to winds. In particular, when wind speed is near the airspeed, guidance is further complicated by the parafoils inability to penetrate the wind. This article specifically addresses the terminal phase and develops an approach for generating optimal trajectories in real-time based on the inverse dynamics in the virtual domain. The method results in efficient solution of a two-point boundary-value problem using only a single optimization parameter allowing the trajectory to be generated at a high rate, mitigating effects of the unknown winds. It is shown …

Tethered Aerostat Modeling Using An Efficient Recursive Rigid-Body Dynamics Approach, Brad Hembree, Nathan Slegers

Faculty Publications - Biomedical, Mechanical, and Civil Engineering

A tethered aerostat model is developed using a computationally efficient recursive tether model. The recursive rigid-body tether model results in unconstrained ordinary differential equations and maintains much of the simplicity of simple lumped-mass tether models, while avoiding numerical difficulties associated with using many stiff elastic elements with low mass. Further efficiency is achieved by treating each tether link as a body of revolution and assuming that tether spin is negligible to the dynamics. The tether is attached to a six-degree-of-freedom aerostat model using a single viscoelastic element. The final recursive tethered aerostat model is well suited for a variety of …

Retrieval Of Canopy Height Using Moderate-Resolution Imaging Spectroradiometer (Modis) Data, Zhuosen Wang, Crystal B. Schaaf, Philip Lewis, Yuri Knyazikhin, Mitchell A. Schull, Alan H. Strahler, Tian Yao, Ranga B. Myneni, Mark J. Chopping, Bryan J. Blair

United States National Aeronautics and Space Administration: Publications

In this study we use the 500 m Moderate Resolution Imaging Spectroradiometer (MODIS) Bidirectional Reflectance Distribution Function (BRDF) product to develop multivariate linear regression models that estimate canopy heights over study sites at Howland Forest, Maine, Harvard Forest, Massachusetts and La Selva Forest, Costa Rica using (1) directional escape probabilities that are spectrally independent and (2) the directional spectral reflectances used to derive the directional escape probabilities. These measures of canopy architecture are compared with canopy height information retrieved from the airborne Laser Vegetation Imaging Sensor (LVIS). Both the escape probability and the directional reflectance approaches achieve good results, with …

Aether, Thomas Cameron, Kristine Colton, Daren Childers

Electrical Engineering

Aether is a RC-style autonomous air vehicle that utilizes GPS positioning along with a wireless communication system to achieve a computer-controlled flight.

This report will incorporate the acquisition, design, integration, implementation and testing phases of the UAV development. Furthermore a discussion of troubleshooting as well as improvements for future projects will be included.

Translational And Rotational Control Of An Asteroid Orbiting Satellite, Takahiro Kuhara

Doctoral Dissertations and Master's Theses

The objective of this thesis is to analyze an effective control scheme for an asteroid orbiting satellite. The thesis first summarizes the progress made in the dynamics formulation of such satellites and then provides a theoretical framework for the control system design. The control objective is to maintain a nadir pointing attitude on a circular equatorial orbit. Using established control design techniques, feedback laws are constructed to control both rotational and translational motion of the satellite so that the control objective is achieved. Computer simulations are carried out to illustrate the effectiveness of the control laws.

Flight Testing In A Simulation Based Environment, David W. Babka

Aerospace Engineering

Over the past two decades performance flight testing of full scale aircraft has transferred some of the testing workload to simulation based systems.  Flight testing full scale aircraft in the real world environment has always been expensive, especially now with the rise in aviation fuel costs. Additionally, new emerging technologies require extensive testing and doing so in the full scale environment is cost prohibitive.  A cheaper alternative is to test systems in a simulation based environment.  Not only can aircraft be simulated via a computer, but all the aircrafts systems can be modeled in the simulation.  Furthermore, most of the …

Navigation With Limited Prior Information Using Time Difference Of Arrival Measurements From Signals Of Opportunity, Christopher M. Rondeau

Theses and Dissertations

The Global Positioning System (GPS) provides world-wide availability to high-accuracy navigation and positioning information. However, the threats to GPS are increasing, and many limitations of GPS are being encountered. Simultaneously, systems previously considered as viable backups or supplements to GPS are being shut down. This creates the need for system alternatives. Navigation using signals of opportunity (SoOP) exploits any signal that is available in a given area, regardless of whether or not the original intent of the signal was for navigation. Common techniques to compute a position estimate using SoOP include received signal strength, angle of arrival, time of arrival, …

Modeling Of A Gyro-Stabilized Helicopter Camera System Using Neural Networks, Nicholas Joseph Layshot

Master's Theses

On-board gimbal systems for camera stabilization in helicopters are typically based on linear models. Such models, however, are inaccurate due to system nonlinearities and complexities. As an alternative approach, artificial neural networks can provide a more accurate model of the gimbal system based on their non-linear mapping and generalization capabilities.

This thesis investigates the applications of artificial neural networks to model the inertial characteristics (on the azimuth axis) of the inner gimbal in a gyro-stabilized multi-gimbal system. The neural network is trained with time-domain data obtained from gyro rate sensors of an actual camera system. The network performance is evaluated …