Adaptive Control For Autonomous Navigation Of Mobile Robots Considering Time Delay And Uncertainty,
2015
North Carolina Agricultural and Technical State University
Adaptive Control For Autonomous Navigation Of Mobile Robots Considering Time Delay And Uncertainty, Stephen Kofi Armah
Dissertations
Autonomous control of mobile robots has attracted considerable attention of researchers in the areas of robotics and autonomous systems during the past decades. One of the goals in the field of mobile robotics is development of platforms that robustly operate in given, partially unknown, or unpredictable environments and offer desired services to humans. Autonomous mobile robots need to be equipped with effective, robust and/or adaptive, navigation control systems. In spite of enormous reported work on autonomous navigation control systems for mobile robots, achieving the goal above is still an open problem. Robustness and reliability of the controlled system can always …
Topology Optimization For Thin Walled Structures Utilizing Simp Method By Additive Manufacturing Using Optimized Conditions,
2015
University of Texas at Arlington
Topology Optimization For Thin Walled Structures Utilizing Simp Method By Additive Manufacturing Using Optimized Conditions, Sajith Anantharaman
Mechanical and Aerospace Engineering Theses - Archive
The objective of this research is to manufacture topology optimized structure by additive manufacturing. Topology Optimization is a method of structural optimization which gives the optimum material distribution in a design domain. This material distribution is then manufactured by additive manufacturing. Additive manufacturing can manufacture complex shapes quite easily since it works by layer-by-layer. This is an on-going field of research and not many optimization algorithms make use of the advantages of additive manufacturing. Numerous researches are done in the field of optimization which are directed towards Homogenization and Solid Isotropic material with Penalization (SIMP). But most of the methods …
Autoignition Behavior Of Synthetic Alternative Jet Fuels: An Examination Of Chemical Composition Effects On Ignition Delays At Low To Intermediate Temperatures,
2015
University of Illinois at Urbana-Champaign
Autoignition Behavior Of Synthetic Alternative Jet Fuels: An Examination Of Chemical Composition Effects On Ignition Delays At Low To Intermediate Temperatures, Daniel Valco, Gerald Gentz, Casey Allen, Meredith Colket, Tim Edwards, Sandeep Gowdagiri, Matthew A. Oehlschlaeger, Elisa Toulson, Tonghun Lee
United States Air Force: Publications
The autoignition characteristics of military aviation fuels (JP-5 and JP-8), proposed camelina-derived hydroprocessed renewable jet fuel replacements (HRJ-8 and HRJ-5), Fischer–Tropsch fuels (Shell and Sasol), three Sasol isoparaffinic solvents, as well as 50/50 volumetric blends of the alternative fuels with the conventional fuels are examined. Experiments were conducted in a rapid compression machine and shock tube at compressed temperatures of 625 K ≤ Tc ≤ 1000 K, a compressed pressure of 20 bar, and under stoichiometric and lean conditions. Several implicit properties of the alternative fuels prompted a study of the influence of chemical composition on autoignition, including the influence …
Discrete-Time Neural Network Based State Observer With Neural Network Based Control Formulation For A Class Of Systems With Unmatched Uncertainties,
2015
Missouri University of Science and Technology
Discrete-Time Neural Network Based State Observer With Neural Network Based Control Formulation For A Class Of Systems With Unmatched Uncertainties, Jason Michael Stumfoll
Masters Theses
"An observer is a dynamic system that estimates the state variables of another system using noisy measurements, either to estimate unmeasurable states, or to improve the accuracy of the state measurements. The Modified State Observer (MSO) is a technique that uses a standard observer structure modified to include a neural network to estimate system states as well as system uncertainty. It has been used in orbit uncertainty estimation and atmospheric reentry uncertainty estimation problems to correctly estimate unmodeled system dynamics. A form of the MSO has been used to control a nonlinear electrohydraulic system with parameter uncertainty using a simplified …
Parameter Determination And Experimental Validation Of A Wire Feed Additive Manufacturing Model,
2015
Missouri University of Science and Technology
Parameter Determination And Experimental Validation Of A Wire Feed Additive Manufacturing Model, Kannan Suresh Kumar
Masters Theses
“Laser metal deposition is an additive manufacturing method with great scope and robustness. The wire fed additive manufacturing method has great opportunities in space applications and other zero gravity manufacturing processes. Process parameters play an important role in controlling the complex phenomenon and obtaining an ideal manufactured part. These parameters can be efficiently determined using simulation tools which are highly essential in visualizing real world experiments, therefore saving time and experimental costs. The objective of this study is to develop a transient 3D model of laser aided wire feed metal deposition which realizes the heat transfer and fluid flow behavior …
Hybrid Manufacturing Process Of SicF/Sic Composite Using Preceramic Polymer,
2015
Missouri University of Science and Technology
Hybrid Manufacturing Process Of SicF/Sic Composite Using Preceramic Polymer, Robert Raymond Meinders
Masters Theses
"Continuous fiber-reinforced silicon carbide (SiCf/SiC) ceramic composites have been increasingly used due to their high temperature strength and graceful failure mechanisms. A disadvantage is the high cost and lengthy production processes that are required to develop these materials. Polymer infiltration and pyrolysis (PIP) is one of the most attractive fabrication processes for composites due to shape flexibility, mass production and relatively low cost; however, the quality of material obtained by this method has been considered insufficient due to the microstructure defects of the material obtained. This study investigated a hybrid of multiple polymer manufacturing processes to maximize quality …
Adjoint-Based Airfoil Shape Optimization In Transonic Flow,
2015
Missouri University of Science and Technology
Adjoint-Based Airfoil Shape Optimization In Transonic Flow, Joe-Ray Gramanzini
Masters Theses
"The primary focus of this work is efficient aerodynamic shape optimization in transonic flow. Adjoint-based optimization techniques are employed on airfoil sections and evaluated in terms of computational accuracy as well as efficiency. This study examines two test cases proposed by the AIAA Aerodynamic Design Optimization Discussion Group. The first is a two-dimensional, transonic, inviscid, non-lifting optimization of a Modified-NACA 0012 airfoil. The second is a two-dimensional, transonic, viscous optimization problem using a RAE 2822 airfoil. The FUN3D CFD code of NASA Langley Research Center is used as the ow solver for the gradient-based optimization cases. Two shape parameterization techniques …
Uncertainty Quantification Of Turbulence Model Closure Coefficients For Transonic Wall-Bounded Flows,
2015
Missouri University of Science and Technology
Uncertainty Quantification Of Turbulence Model Closure Coefficients For Transonic Wall-Bounded Flows, John Anthony Schaefer
Masters Theses
"The goal of this work was to quantify the uncertainty and sensitivity of commonly used turbulence models in Reynolds-Averaged Navier-Stokes codes due to uncertainty in the values of closure coefficients for transonic, wall-bounded flows and to rank the contribution of each coefficient to uncertainty in various output flow quantities of interest. Specifically, uncertainty quantification of turbulence model closure coefficients was performed for transonic flow over an axisymmetric bump at zero degrees angle of attack and the RAE 2822 transonic airfoil at a lift coefficient of 0.744. Three turbulence models were considered: the Spalart-Allmaras Model, Wilcox (2006) k-ω Model, and the …
Adaptive Double Chain Quantum Genetic Algorithm For Constrained Optimization Problems,
2015
Old Dominion University
Adaptive Double Chain Quantum Genetic Algorithm For Constrained Optimization Problems, Kong Haipeng, Li Ni, Yuzhong Shen
Computational Modeling & Simulation Engineering Faculty Publications
Optimization problems are often highly constrained and evolutionary algorithms (EAs) are effective methods to tackle this kind of problems. To further improve search efficiency and convergence rate of EAs, this paper presents an adaptive double chain quantum genetic algorithm (ADCQGA) for solving constrained optimization problems. ADCQGA makes use of double-individuals to represent solutions that are classified as feasible and infeasible solutions. Fitness (or evaluation) functions are defined for both types of solutions. Based on the fitness function, three types of step evolution (SE) are defined and utilized for judging evolutionary individuals. An adaptive rotation is proposed and used to facilitate …
Diffusion And Elastoplastic Analyses Of Polycrystalline Magnesium For Solid State Hydrogen Storage Application,
2015
University of Texas at Arlington
Diffusion And Elastoplastic Analyses Of Polycrystalline Magnesium For Solid State Hydrogen Storage Application, Amey Mathakari
Mechanical and Aerospace Engineering Theses - Archive
Solid state hydrogen storage can be an effective way of storing hydrogen as an energy source for mobile applications. The advantage includes high energy density, low setup cost, safe operation, abundance of metal hydrides, low maintenance, etc. Magnesium is one of the potential metals for the application. However, sluggish desorption kinetics of magnesium requiring relatively high operation temperature has hindered its practical realization. In the present study, an attempt is made to analyze effects of grain boundary on diffusion and diffusion induced stresses in polycrystalline magnesium. Grain boundaries in nanostructured magnesium can undergo severe plastic deformations during the hydrogen insertion …
Simulation And Performance Analysis Of Ejector Nozzle In A Low-Bypass Turbofan Engine Using Npss,
2015
University of Texas at Arlington
Simulation And Performance Analysis Of Ejector Nozzle In A Low-Bypass Turbofan Engine Using Npss, Hatim Soeb Rangwala
Mechanical and Aerospace Engineering Theses - Archive
Nozzles for propulsive applications in airbreathing engines have long been studied to augment thrust and reduce the size of the engine. They are critical elements of the engine as they convert the internal energy into kinetic energy, thereby producing thrust. Fixed-geometry nozzles are operated optimally only at a particular set of flight conditions and are not efficient at off-design conditions. To improve off-design performance, variable geometry nozzles can be utilized which require complex mechanisms that ultimately increase weight and susceptibility to failure. Ejector nozzles provide variable geometry capability via aerodynamically varying the effective area ratios of the core and bypass …
Assessing Interlaminar Shear Stress-Strain Curves In Tape Composites Based On The Flat-Plate Torsion Method,
2015
University of Texas at Arlington
Assessing Interlaminar Shear Stress-Strain Curves In Tape Composites Based On The Flat-Plate Torsion Method, Gary Steven Grohman
Mechanical and Aerospace Engineering Theses - Archive
Composites are attractive for structural applications in the aerospace industry for their high strength to weight ratio, stiffness, and low density. The development and implementation of composite structures has grown rapidly through the aerospace industry exceeding our ability to characterize the material properties due to costly and time consuming test methods. The ability to fully characterize the nonlinear stress-strain relationship in the 1-3 and 2-3 principal planes up to the point of failure is extremely important for predicting failures in composites. The principal directions for composites are the fiber direction, transverse direction, and the thru thickness direction, commonly referred to …
Heat Removal Analysis Using Ntu Microscopic Theory And Experimental Fluid Testing Of Radaitors, Pumps And Fans For The Thermal Management System Of Formula Sae Electric Racecar,
2015
University of Texas at Arlington
Heat Removal Analysis Using Ntu Microscopic Theory And Experimental Fluid Testing Of Radaitors, Pumps And Fans For The Thermal Management System Of Formula Sae Electric Racecar, Shahzad Shahrukh Bulsara
Mechanical and Aerospace Engineering Theses - Archive
Formula SAE at UT Arlington has always been building well engineered race cars, further being one of the top teams in The United States. However, an electric race car being first in the fleet, cooling of electric motors played a vital role. The thermal system being significantly different from combustion cars, consists of a lower heat application. It is always favorable to maintain electronics as close to ambient temperature as compared to its counter hydro-mechanical engines. To attain the objective, a complete thermal & fluid analysis was carried out using the NTU method/ microscopic theory and experimental results associated towards …
Icao Aviation System Block Upgrades: A Method For Identifying Training Needs,
2015
University of Nebraska at Omaha
Icao Aviation System Block Upgrades: A Method For Identifying Training Needs, Rebecca K. Lutte
Aviation Institute Faculty Publications
Since the mid-1970s, air traffic growth has expanded two-fold once every fifteen years (ICAO, 2013). The ICAO Global Air Navigation Plan (GANP) is a roadmap to achieve a “vision of an integrated, harmonized, and globally interoperable air traffic management (ATM) system” (ICAO, 2012, p. 1). A component of the GANP is the Aviation System Block Upgrades (ASBU), a framework for achieving that vision. A collaborative approach led by ICAO between public and private organizations and member states resulted in the development of the ASBU framework. However, obstacles exist for successful implementation. One area of concern is the need for training …
Analysis Of Thin-Walled Cylindrical Composite Shell Structures Subject To Axial And Bending Loads: Concept Development, Analytical Modeling And Experimental Verification,
2015
University of Texas at Arlington
Analysis Of Thin-Walled Cylindrical Composite Shell Structures Subject To Axial And Bending Loads: Concept Development, Analytical Modeling And Experimental Verification, Sthanu Mahadev
Mechanical and Aerospace Engineering Dissertations - Archive
Several studies have focused on the modeling and response characterization of composite structural members, with particular emphasis on thin-walled cylindrical composite shells. This class of shell configurations is explored to determine their mechanical response in primary aerospace structural members. The present work is focused on formulating a modified composite shell theory prognosis methodology for investigating the structural response of thin-walled cylindrical shell type composite configurations under axial and bending loads, respectively. The prime motivation to develop this theory arises from its capability to generate simple yet accurate closed-form analytical results that can efficiently charecterize cylindrical composite shell constructions. This work …
Design Of Next Generation Antenna Mounts In Telecommunication Towers With Low Effective Projected Area,
2015
University of Texas at Arlington
Design Of Next Generation Antenna Mounts In Telecommunication Towers With Low Effective Projected Area, Ruben Gregory Puthota Dominic Savio
Mechanical and Aerospace Engineering Theses - Archive
Design of new antenna mount with low effective projected area (EPA) and high load carrying capacity for telecommunication towers is the purpose of this thesis. The main aim is to reduce the EPA of the mount against the wind pressure direction at the desired elevation from ground by reducing the mount frame structure parts compared to the previous mount designs used in the market. The model in itself has to withstand its dead weight, operator’s weight along with five antenna-radio units. The new model has been designed with a single horizontal frame and four supporting structure for EPA reduction and …
Characterization Of Flapping Wing Aerodynamics And Flight Dynamics Analysis Using Computational Methods,
2015
University of Texas at Arlington
Characterization Of Flapping Wing Aerodynamics And Flight Dynamics Analysis Using Computational Methods, Alok Ashok Rege
Mechanical and Aerospace Engineering Dissertations - Archive
Insect flight comes with a lot of intricacies that cannot be explained by conventional aerodynamics. Even with their small-size, insects have the ability to generate the required aerodynamic forces using high frequency flapping motion of their wings to perform different maneuvers. The maneuverability obtained by these flyers using flapping motion belies the classical aerodynamics theory and calls for a new approach to study this highly unsteady aerodynamics. Research is on to find new ways to realize the flight capabilities of these insects and engineer a micro-flyer which would have various applications, ranging from autonomous pollination of crop fields and oil …
Comprehensive Design Analysis Of Thick Fr-4 Qfn Assemblies For Enhanced Board Level Reliability,
2015
University of Texas at Arlington
Comprehensive Design Analysis Of Thick Fr-4 Qfn Assemblies For Enhanced Board Level Reliability, Abhishek Nitin Deshpande
Mechanical and Aerospace Engineering Theses - Archive
Quad Flat No-lead package (QFN) is one of the most cutting-edge technologies emerged in the market, exhibiting high performance and efficiency with unparalleled cost effectiveness. QFN, a leadless package, is an ideal choice for applications where size, weight thermal and electrical characteristics are critical, particularly in mobile and handheld devices. Applications like automotive, defense and high current circuits require the package to be mounted on thick printed circuit boards (PCB). But using thick PCBs (>3mm) is detrimental to the package reliability. The motivation of this work is to understand the effect of several package parameters affecting reliability and optimize …
Experimental Investigation Of Wall Shear Stress Modifications Due To Turbulent Flow Over An Ablative Thermal Protection System Analog Surface,
2015
University of Kentucky
Experimental Investigation Of Wall Shear Stress Modifications Due To Turbulent Flow Over An Ablative Thermal Protection System Analog Surface, Jacob Helvey
Theses and Dissertations--Mechanical and Aerospace Engineering
Modifications were made to the turbulent channel flow facility to allow for fully developed rough quasi-2D Poiseuille flow with flow injection through one surface and flow suction through the opposing surface. The combination of roughness and flow injection is designed to be analogous to the flow field over a thermal protection system which produces ablative pyrolysis gases during ablation. It was found that the additional momentum through the surface acted to reduce skin friction to a point below smooth-wall behavior. This effect was less significant with increasing Reynolds number. It was also found that the momentum injection modified the wake …
Modeling Of Spallation Phenomenon In An Arc-Jet Environment,
2015
University of Kentucky
Modeling Of Spallation Phenomenon In An Arc-Jet Environment, Raghava Sai Chaitanya Davuluri
Theses and Dissertations--Mechanical and Aerospace Engineering
Space vehicles, while entering the planetary atmosphere, experience high loads of heat. Ablative materials are commonly used for a thermal protection system, which undergo mass removal mechanisms to counter the heat rates. Spallation is one of the ablative processes, which is characterized by the ejection of solid particles from the material into the flow. Numerical codes that are used in designing the heat shields ignore this phenomenon. Hence, to evaluate the effectiveness of spallation phenomenon, a numerical model is developed to compute the dynamics and chemistry of the particles. The code is one-way coupled to a CFD code that models …
