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Articles 61 - 90 of 299
Full-Text Articles in Electrical and Computer Engineering
Real-Time Path Planning And Obstacle Avoidance For Mobile Robots With Actuator Faults, Ravindra Vibha Bellur
Real-Time Path Planning And Obstacle Avoidance For Mobile Robots With Actuator Faults, Ravindra Vibha Bellur
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In this research, a fault-tolerant path planning and obstacle avoidance algorithm is implemented for mobile ground robots. The fault-tolerant system architecture consists of the following three components: (1) an online fault diagnosis module for detecting and estimating actuator faults in the mobile robot; (2) a localization and mapping module for dynamic terrain mapping and obstacle detection; (3) a path planning and obstacle avoidance module for generating way points from a given point to the desired destination, avoiding the detected obstacles and moving along these way points. The online fault diagnostic information is used to compensate for the effect of faults, …
Control And Optimization Of Power In Llc Converter Using Phase Control, Nagasri Kollipara
Control And Optimization Of Power In Llc Converter Using Phase Control, Nagasri Kollipara
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LLC resonant converters are popular among resonant topologies due to their high efficiency and ability to achieve ZVS and ZCS for wide input range. LLC resonant converters are controlled by frequency modulation (FM), which makes converter difficult to optimize the system in terms of achieving efficient power conversion. FM technique also generate wide range of harmonics which leads to a wide sweep in operating frequency, which can run into regulatory EMI test limits and cause electromagnetic compatibility issues. The performance of LLC topology extends to their poor efficiency at lighter loads, due to constant high magnetization current. In order to …
Examination Of Gain Scheduling And Fuzzy Controllers With Hybrid Reachability, Aaron W. Fifarek
Examination Of Gain Scheduling And Fuzzy Controllers With Hybrid Reachability, Aaron W. Fifarek
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Modern aircraft with nonlinear flight envelopes predominately utilize gain scheduled controllers to provide stability of flight. Using gain scheduled control techniques, nonlinear envelopes can be linearized into collections of linear systems that operate under various system dynamics. Linear controllers approximate the nonlinear response over setpoints of operating conditions which allow traditional linear theory to be applied to maintain stability. Techniques to prove linear stability are well understood and realized in control systems, but when controllers are switched, interpolation methods must be used. Interpolation is necessary as gain scheduled systems do not have foundational switching paradigms as part of their realization …
Chaotic Based Self-Synchronization For Rf Steganography Radar/Communication Waveform, Michael A. Gonnella
Chaotic Based Self-Synchronization For Rf Steganography Radar/Communication Waveform, Michael A. Gonnella
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In this project, we continue previous CSR project entitled RF Steganography based Joint Radar/Communication Waveform Design to develop a bio-inspired secure low probability detection (LPD) radio frequency (RF) waveform that can serve multiple purposes simultaneously. Previously, we have developed an RF steganography based RF waveform to conceal a secure digital communication within a linear frequency modulated (LFM) chirp radar signal. By exploiting novel reduced phase shift keying modulation and variable symbol duration, the new waveform is resistant to time domain analysis, frequency domain analysis and cyclostationary analysis. However, to demodulate the hidden communication message, the intended receiver has to know …
Feed-Forward Compensation Of Non-Minimum Phase Systems, Venkatesh Dudiki
Feed-Forward Compensation Of Non-Minimum Phase Systems, Venkatesh Dudiki
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Due to inherent limitations posed by existence of zeros of a transfer function in the righthalfof the complex plane, known as non-minimum phase zeros, the issue of dealing withsuch zeros is extremely important in control of linear systems. Considerable literatureexists in control theory to try and minimize or eliminate the effect of non-minimum phasezeros. These include pole-zero cancellation, feedforward compensation, among others.These methods are only limited only to stable systems (systems with poles in the left halfof the complex plane); and will fail for systems that are unstable as well as non-minimumphase.This research focuses in designing feedforward compensators for unstable …
Temperature Robust Longwave Infrared Hyperspectral Change Detection, Nicholas A. Durkee
Temperature Robust Longwave Infrared Hyperspectral Change Detection, Nicholas A. Durkee
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In this thesis, we develop and evaluate change detection algorithms for longwave infrared (LWIR) hyperspectral imagery. Because measured radiance in the LWIR domain depends on unknown surface temperature, care must be taken to prevent false alarms resulting from in-scene temperature differences that appear as material changes. We consider fewer variables. Examples using synthetic and measured data quantify the computational complexity of the proposed methods and demonstrate orders of magnitude reduction in false alarm rates relative to existing methods. Four strategies to mitigate this effect. In the first, pre-processing via traditional temperatureemissivity separation yields approximately temperature-invariant emissivity vectors for use in …
Fpga-Based Ir Localization Sensor, Samuel I. Susanto
Fpga-Based Ir Localization Sensor, Samuel I. Susanto
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Pursuit-evasion scenarios are common in both natural and man-made systems. Often times, the pursuer and evader maneuver in response to each others actions using relative information based on the geometry of the agents and potential obstacles within the environment. The pursuer needs the target's bearing angle in order to plan a trajectory or path to capture it. We propose an FPGA-based infrared sensor array to detect up to 6 agents' bearing angles simultaneously. The final output of the sensor is the bearing angle of other agents. The sensor was tested and validated experimentally. Implementing the sensor and transmitter pair on …
Analysis Of Evolutionary Algorithms In The Control Of Path Planning Problems, Pavlos Androulakakis
Analysis Of Evolutionary Algorithms In The Control Of Path Planning Problems, Pavlos Androulakakis
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The purpose of this thesis is to examine the ability of evolutionary algorithms (EAs) to develop near optimal solutions to three different path planning control problems. First, we begin by examining the evolution of an open-loop controller for the turn-circle intercept problem. We then extend the evolutionary methodology to develop a solution to the closedloop Dubins Vehicle problem. Finally, we attempt to evolve a closed-loop solution to the turn constrained pursuit evasion problem. For each of the presented problems, a custom controller representation is used. The goal of using custom controller representations (as opposed to more standard techniques such as …
Leveraging 3d Models For Sar-Based Navigation In Gps-Denied Environments, Zachary A. Reid
Leveraging 3d Models For Sar-Based Navigation In Gps-Denied Environments, Zachary A. Reid
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This thesis considers the use of synthetic aperture radar (SAR) to provide absolute platform position information in scenarios where GPS signals may be degraded, jammed, or spoofed. Two algorithms are presented, and both leverage known 3D ground structure in an area of interest, e.g. provided by LIDAR data, to provide georeferenced position information to airborne SAR platforms. The first approach is based on the wide-aperture layover properties of elevated reflectors, while the second approach is based on correlating backprojected imagery with digital elevation imagery. Both of these approaches constitute the system we have designated: SARNAV. Building on 3D backprojection, localization …
Switching Neural Network Systems For Nonlinear Tracking, Manoj Ghimire
Switching Neural Network Systems For Nonlinear Tracking, Manoj Ghimire
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In this thesis, we consider the problem of tracking in complex nonlinear dynamical systems. While the Kalman filter is known to be the mean-squared error optimal tracker under linear dynamics and linear measurements, more sophisticated models and algorithms are required for complex dynamics. Here, we consider switching systems where the dynamical properties vary (''switch modes") over time. For example, the dynamics of a vehicle may switch as it transitions from interstate to urban conditions, human speech dynamics switch as speakers change, and stock market dynamics switch with discrete news events. In this work, we use mode-dependent neural networks to capture …
A Simulation Method For Studying Effects Of Site-Specific Clutter On Sar-Gmti Performance, Marcus James Campbell
A Simulation Method For Studying Effects Of Site-Specific Clutter On Sar-Gmti Performance, Marcus James Campbell
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Synthetic aperture radar (SAR) is an invaluable tool for detection of ground moving targets when combined with processing techniques of ground moving target indication (GMTI). This work investigates a simulation methodology for studying impact of site-specific ground clutter on SAR-GMTI performance. A terrain model is proposed and is based on digital terrain elevation data (DTED) and national land-use land-cover data (NLCD) as provided by the US Geological Survey. The proposed physical optics simulation method capitalizes on high-fidelity digital target models in combination with the proposed terrain model. SAR phase history is generated for a moving commercial target in situ of …
A Robust Low Power Static Random Access Memory Cell Design, A. V. Rama Raju Pusapati
A Robust Low Power Static Random Access Memory Cell Design, A. V. Rama Raju Pusapati
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Stability of a Static Random Access Memory (SRAM) cell is an important factor when considering an SRAM cell for any application. The Static Noise Margin (SNM) of a cell, which determines the stability, varies under different operating conditions. Based on the performance of three existing SRAM cell designs, 6T, 8T and 10T, a 10 Transistor SRAM cell is proposed which has good stability and has the advantage of reduced read power when compared to 6T and 8T SRAM cells. The proposed 10T SRAM cell has a single-ended read circuit which improves SNM over the 6T cell. The proposed 10T cell …
Impact Of Near-Field-To-Far-Field Transformation On Sar Images Formed In An Indoor Non-Anechoic Environment, Jacob D. Compaleo
Impact Of Near-Field-To-Far-Field Transformation On Sar Images Formed In An Indoor Non-Anechoic Environment, Jacob D. Compaleo
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This work investigates the impact of the near-field-to-far-field transformation (NFFFT) algorithm on phase history measurement collections completed in the Sensors and Signals Exploitation Laboratory (SSEL). SSEL is an indoor non-anechoic environ- ment that is at risk to some measurement interferences such as multiple bounces. Complete 360-degree phase history measurements of scale model aircraft are con- ducted at varying range values within the near-field limit. These measurements are calibrated with the Mie series scattering solution for a sphere. After calibration, the measurements are transformed using the NFFFT, with radar cross-section (RCS) estimated. RCS of the transformed data is compared with the …
Wetting Properties Of Structured Interfaces Composed Of Surface-Attached Spherical Nanoparticles, Bishal Bhattarai
Wetting Properties Of Structured Interfaces Composed Of Surface-Attached Spherical Nanoparticles, Bishal Bhattarai
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In this thesis, the effects of the external pressure and surface energy on stability and wetting transition at nanotextured interfaces are studied using molecular dynamics and continuum simulations. The surface roughness of the composite interface is modeled via an array of spherical nanoparticles with controlled wettability. It was found that in the absence of external pressure, the liquid interface is flat and its location relative to the solid substrate is determined by the radius of the particle and the local contact angle. With increasing pressure on the liquid film, its interface becomes more curved and the three-phase contact line is …
Display And Analysis Of Tomographic Reconstructions Of Multiple Synthetic Aperture Ladar (Sal) Images, Bassirou Seck
Display And Analysis Of Tomographic Reconstructions Of Multiple Synthetic Aperture Ladar (Sal) Images, Bassirou Seck
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Synthetic aperture ladar (SAL) is similar to synthetic aperture radar (SAR) in that it can create range/cross-range slant plane images of the illuminated scatters; however, SAL has wavelengths 10,000x smaller than SAR enabling a relatively narrow real aperture, diffraction limited beam widths. The relatively narrow real aperture resolutions allow for multiple slant planes to be created for a single target with reasonable range/aperture combinations. These multiple slant planes can be projected into a single slant plane projections (as in SAR). It can also be displayed as a 3-D image with asymmetric resolutions, diffraction limited in the dimension orthogonal to the …
Steady-State And Small-Signal Modeling Of A-Source Converter, Agasthya Ayachit
Steady-State And Small-Signal Modeling Of A-Source Converter, Agasthya Ayachit
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As the trend towards vehicle electrification, renewable energy, smart systems is increasing, the key enabling technology such as power electronics are becoming ever more important. Power electronics is the vital component of many applications in automotive, computer, data-centers, medical, aerospace, communication, green-energy, and manufacturing sectors. Major advancements in high efficiency, high power density, high voltage conversion ratio, and fast dynamic response power-electronic converters is evident both in research and industry, particularly at the topology level. A major contribution of this dissertation is the analysis, design, development, and dynamic modeling of a novel impedance-source topology termed as A-source converter, which potentially …
Characterization And Design Of Voltage-Mode Controlled Full-Bridge Dc/Dc Converter With Current Limit, Nathaniel R. Smith
Characterization And Design Of Voltage-Mode Controlled Full-Bridge Dc/Dc Converter With Current Limit, Nathaniel R. Smith
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Advancements in Direct Current (DC) electrical power systems have enabled new functionality in many, varied applications. Discrete power semiconductor devices are increasing in efficiency, switching frequency, and power density, resulting in greater usage of DC power management and distribution methods, including DC/DC conversion. DC distribution lacks inherent capability to safely and effectively break fault current, particularly in mobile solutions, where larger and slower electromechanical switching devices are not optimal or feasible. One solution is to design a low-energy breaking point into a switching power supply. Simpler converter designs, with a lower number of switching devices, have been modeled and can …
Effects Of The Kinematic Model On Forward-Model Based Spotlight Sar Ecm, David T. Pyles
Effects Of The Kinematic Model On Forward-Model Based Spotlight Sar Ecm, David T. Pyles
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Spotlight synthetic aperture radar (SAR) provides a high-resolution remote image formation capability for airborne platforms. SAR image formation processes exploit the amplitude, time, and frequency shifts that occur in the transmitted waveform due to electromagnetic propagation and scattering. These shifts are predictable through the SAR forward model which is dependent on the waveform parameters and emitter flight path. The approach to develop an electronic countermeasure (ECM) system that is founded on the SAR forward model implies that the ECM system should alter the radar's waveform in a manner that produces the same amplitude, time, and frequency shifts that a real …
Design Of An 8-Bit Successive Approximation Pipelined Analog To Digital Converter (Sap-Adc) In 90 Nm Cmos, Vivek Kotti
Design Of An 8-Bit Successive Approximation Pipelined Analog To Digital Converter (Sap-Adc) In 90 Nm Cmos, Vivek Kotti
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Analog to Digital Converters bridge the gap between physical world and digital signal processing. Most times analog signals received from the real world needs to be amplified and converted to digital to impart various signal enhancements to the received signal. The digital signal is much suitable to operate on with less noise and well defined logic levels when compared to continuously varying analog signal. Communication systems demand ever-increasing bandwidth which unfortunately has been a huge limitation for present day ADCs. Hence, an architecture which combines the accuracy of a SAR -ADC with the concept of pipelining to increase the bandwidth …
Sv-Means: A Fast One-Class Support Vector Machine-Based Level Set Estimator, Anne M. Pavy
Sv-Means: A Fast One-Class Support Vector Machine-Based Level Set Estimator, Anne M. Pavy
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In this dissertation, a novel algorithm, SV-Means, is developed motivated by the many functions needed to perform radar waveform classification in an evolving, contested environment. Important functions include the ability to: reject classes not in the library, provide confidence in the classification decision, adapt the decision boundary on-the-fly, discover new classes, and quickly add new classes to the library. The SV-Means approach addresses these functions by providing a fast algorithm that can be used for anomaly detection, density estimation, open set classification, and clustering, within a Bayesian generative framework. The SV-Means algorithm extends the quantile one-class support vector machine (q-OCSVM) …
An Optimization Strategy For Hexapod Gait Transition, Naga Harika Darbha
An Optimization Strategy For Hexapod Gait Transition, Naga Harika Darbha
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Legged robots often need to move through different terrains as they function. This requires a change of gaits by the robot in order to move with better efficiency. There has been a lot of research done to find out which gait works better for a given terrain so that the robot can change its gait accordingly. A reliable analysis of when exactly should the transition take place in a walking robot is important, so that there can be an assurance of stability in the locomotion of the robot during the transition between different gaits. This work presents analysis performed on …
Design Of A Programmable Four-Preset Guitar Pedal, Michael Trombley
Design Of A Programmable Four-Preset Guitar Pedal, Michael Trombley
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Many companies in the music industry offer programmable preset guitar pedals. Presets allow musicians to save time and focus on their act by recalling predetermined settings during a performance. A majority of the companies in the music industry offer up to hundreds of presets, but realistically the substantial amount of presets may have a negative effect on the musician’s performance due to time constraints. The main contribution of this thesis is to address the musician by reducing the amount of presets offered in a guitar pedal design. Combining two systems, a digital control and audio processing circuit, will produce a …
Computational Modeling Of A Williams Cross Flow Turbine, Sajjan Pokhrel
Computational Modeling Of A Williams Cross Flow Turbine, Sajjan Pokhrel
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Hydropower is not only the most used renewable energy source in the United States, but in the world. While it is well known that large hydropower facilities, like the Hoover Dam, provide large amounts of electrical power, there is also a tremendous opportunity for hydroelectric power generation from small scale facilities that has largely been overlooked. The work being presented here studies a new cross flow turbine called the Williams Cross Flow Turbine (WCFT), which was designed to extract electric energy from low head, run-of-the-river, small hydropower sites. To spur the implementation of the WCFT in small hydropower applications, and …
Development Of Computer Program For Wind Resource Assessment, Rotor Design And Rotor Performance, Valentina Jami
Development Of Computer Program For Wind Resource Assessment, Rotor Design And Rotor Performance, Valentina Jami
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People understand and have seen that renewable energy has many advantages over conventional energy sources. Because of these advantages, more and more emphasis has been given to generating electrical energy with renewable sources. Among the many renewable and conventional ways currently available for a society to generate electrical power, wind turbines are one of the cheapest ways of doing this. The main objective of this thesis work is to develop a computer program that assesses the wind resource at a given location, designs a wind turbine rotor for optimum power capture for one wind speed, and analyzes the performance of …
Optimal Feature Selection For Spatial Histogram Classifiers, Mandira Thapa
Optimal Feature Selection For Spatial Histogram Classifiers, Mandira Thapa
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Point set classification methods are used to identify targets described by a spatial collection of points, each represented by a set of attributes. Relative to traditional classification methods based on fixed and ordered feature vectors, point set methods require additional robustness to obscured and missing features, thus necessitating a complex correspondence process between testing and training data. The correspondence problem is efficiently solved via spatial pyramid histograms and associated matching algorithms, however the storage requirements and classification complexity grow linearly with the number of training data points. In this thesis, we develop optimal methods of identifying salient point-features that are …
Bistatic Sar Polar Format Image Formation: Distortion Correction And Scene Size Limits, Davin Mao
Bistatic Sar Polar Format Image Formation: Distortion Correction And Scene Size Limits, Davin Mao
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The polar format algorithm (PFA) for bistatic synthetic aperture radar (SAR) image formation offers the compromise between image quality and computational complexity afforded by PFA, while enabling the geometric flexibility of a bistatic collection scenario. The use of the far-field approximation (FFA), which enables the use of the two-dimensional (2D) fast Fourier transform (FFT) in PFA, introduces spatially-varying distortion and defocus effects causing geometric warping and blurring in the resulting image. In this thesis, the residual phase errors due to the FFA are analyzed by decomposing the residual phase errors in the time dimension into their constant, linear, and quadratic …
An Engage Or Retreat Differential Game With Two Targets, Bikash Shrestha
An Engage Or Retreat Differential Game With Two Targets, Bikash Shrestha
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This thesis develops the equilibrium solution for a two-target engage or retreat differential game. In this game, the attacking player is modeled as a massless particle moving with simple motion about an infinite, obstacle-free plane. The opposing player, referred to as the defender, is tasked with the protection of two high-value targets. The mobile attacker must choose to either engage one of the high-value targets or retreat across a predefined boundary. Simultaneously, the defensive player must choose whether to minimize or maximize the attacker's integral utility in an effort to persuade the attacker to choose retreat from certain initial conditions. …
Gnss Receiver Testing And Algorithm Development, Rachael E. Kolker
Gnss Receiver Testing And Algorithm Development, Rachael E. Kolker
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Many current GNSS Software Defined Receivers (SDRs) are often limited in what they can do across a range of developmental applications. They cannot perform acquisition and tracking without several iterations of coding, which does not allow for fast processing. This work provides a Matlab SDR that is based on freely available and optimized components that can be applied to all GNSS signals. A previous basis has been expanded upon to perform tracking of QZSS signals. In addition to this, two separate hardware front ends were compared and their differences analyzed. These hardware systems collected data with different disciplining clocks, but …
Plasma Property Estimation From Dual-Wavelength Interferometry, Andrew J. Hamilton
Plasma Property Estimation From Dual-Wavelength Interferometry, Andrew J. Hamilton
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Diagnostics are necessary for measurement of plasma parameters such as electron, ion and atomic densities, electron temperature, plasma expansion velocity and spatial resolution of density gradients. These parameters play a critical role in defining how a plasma will interact with electromagnetic radiation. For example, the plasma black-out phenomenon occurs when electromagnetic waves are at frequencies below the plasma frequency, where plasma frequency is a function of electron density. Wave propagation diagnostics can improve understanding of a plasma when measurement supports parameter estimation. In this report, the dual-wavelength interferometry method provides a single diagnostic capability to measure plasma expansion velocity, atomic …
Incorporating Passive Compliance For Reduced Motor Loading During Legged Walking, Akhil Sai Pabbu
Incorporating Passive Compliance For Reduced Motor Loading During Legged Walking, Akhil Sai Pabbu
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For purposes of travelling on all-terrains surfaces that are both uneven and discontinuous, legged robots have upper-hand over wheeled and tracked vehicles. The robot used in this thesis is a simulated hexapod with 3 degrees of freedom per leg. The main aim is to reduce the energy consumption of the system during walking by attaching a passive linear spring to each leg which will aid the motors and reduce the torque required while walking. Firstly, the ideal stiffness and location or the coordinates for mounting the spring is found out using gradient based algorithm called `Simultaneous Perturbation and Stochastic Approximation …