Adaptive Control For A Class Of Nonlinear, Time Varying Rotational Systems,
2024
Embry-Riddle Aeronautical University
Adaptive Control For A Class Of Nonlinear, Time Varying Rotational Systems, John Zelina
Doctoral Dissertations and Master's Theses
Aerospace systems often exhibit nonlinear, time varying dynamics. Expansive mission profiles, fuel burn or transfer and payload deployments or slung loads can supply additional complexity that can excite the plant dynamics and result in undesirable performance. Because of these often unknown dynamical effects in aerospace systems, an emphasis is placed on controller robustness as significant safety risks are present. Due to the difficulty of predicting uncertainties, robust control can be achieved in two distinct ways. The first approach is to design a control law to be tolerant to a large amount of uncertainty, and the second is to design a …
A Variable Shape Metastructure Based On Controlled Bistable Structural Elements,
2024
Old Dominion University
A Variable Shape Metastructure Based On Controlled Bistable Structural Elements, Mehmet R. Simsek
Mechanical & Aerospace Engineering Theses & Dissertations
The so-called hybrid position feedback controller is an unstable-then-stable position feedback controller, which is a second-order single-degree-of-freedom system in nature. This hybrid controller takes advantage of the resonant mode of a bistable system about one equilibrium position, destabilizes the system, and dynamically induces snap-through between the two equilibria. In this dissertation, a new multi degree of freedom metastructure concept that utilizes the hybrid position feedback controller is introduced. An arbitrary number of bistable “segments” or “structural elements” are attached to each other in a serial (or parallel) manner to generate a “distributed” bistable structure – also referred to as a …
Effect Of Lunar Magnetic Field And Lunar Regolith Simulant On The Growth And Bioactive Compounds Production Of Chlorella Vulgaris Microalgae,
2024
Old Dominion University
Effect Of Lunar Magnetic Field And Lunar Regolith Simulant On The Growth And Bioactive Compounds Production Of Chlorella Vulgaris Microalgae, Jeries Philip Butros Abedrabbo
Mechanical & Aerospace Engineering Theses & Dissertations
Since humans last went to the moon on the Apollo missions, there has been a fascination with inhabiting and colonizing other planetary objects, starting with the Earth’s Moon, Mars, and recently Jupiter’s moon, Europa. However, there is still lack of knowledge and science behind many of the extraterrestrial environmental effects on biological organisms living on Earth. Therefore, there is a need to study how such environments would affect these organisms. Moreover, how can we attain sustainable living in such environments as well through self-providing life support systems (LSS), without the need to provide for additional necessities back and forth from …
Application Of The Fokker-Planck Equation For Quantifying Initial Condition Uncertainty Of Reversible Dynamic Systems,
2024
Old Dominion University
Application Of The Fokker-Planck Equation For Quantifying Initial Condition Uncertainty Of Reversible Dynamic Systems, Troy S. Newhart
Mechanical & Aerospace Engineering Theses & Dissertations
Characterizing the behavior of dynamic systems requires the inclusion of initial conditions to propagate behavior forward in time. More realistic representations of system behavior quantify uncertainty about the initial conditions to assess sensitivity, reliability, and other stochastic response parameters. In many engineering applications, the uncertain initial conditions may be unknown given a desired response. This research applies the Fokker-Planck equation to reversible dynamic systems of select multi-dimensional nonlinear differential equations as a means for predicting the uncertainty about initial conditions. An alternating directions implicit numerical scheme is used to numerically solve the Fokker-Planck equation for both forward and reversed equations …
Convolutional Spiking Neural Networks For Intent Detection Based On Anticipatory Brain Potentials Using Electroencephalogram,
2024
Missouri University of Science and Technology
Convolutional Spiking Neural Networks For Intent Detection Based On Anticipatory Brain Potentials Using Electroencephalogram, Nathan Lutes, V. Sriram Siddhardh Nadendla, K. Krishnamurthy
Computer Science Faculty Research & Creative Works
Spiking neural networks (SNNs) are receiving increased attention because they mimic synaptic connections in biological systems and produce spike trains, which can be approximated by binary values for computational efficiency. Recently, the addition of convolutional layers to combine the feature extraction power of convolutional networks with the computational efficiency of SNNs has been introduced. This paper studies the feasibility of using a convolutional spiking neural network (CSNN) to detect anticipatory slow cortical potentials (SCPs) related to braking intention in human participants using an electroencephalogram (EEG). Data was collected during an experiment wherein participants operated a remote-controlled vehicle on a testbed …
Friction Stir Welding Of Tube-To-Tubesheet And Spot Joints For Virgin And Recycled Thermoplastic Materials,
2024
United Arab Emirates University
Friction Stir Welding Of Tube-To-Tubesheet And Spot Joints For Virgin And Recycled Thermoplastic Materials, Syed Haris Iftikhar
Dissertations
Thermoplastic materials are becoming popular, due to their chemically inert and anti-fouling properties, for use in industrial heat exchanger applications involving heating/cooling of highly reactive fluids like acids. A novel non-conventional joining framework, based on the Friction Stir Welding (FSW) technique, is developed to create high-quality thermoplastic Tube-to-Tubesheet Joints (TTJs). The proposed technique has applications in the thermoplastic shell-and-tube heat exchanger and piping industries (as flange-to-pipe joints). The primary objective is to study the feasibility of the FSW technique for developing thermoplastic TTJs, followed by optimization of the process parameters and detailed material characterizations. This work used workpieces (tube, tubesheet) …
A Comparison Of Beamforming Characteristics In Isotropic And Composite Plate Structures For Use In Structural Health Monitoring,
2024
Embry-Riddle Aeronautical University
A Comparison Of Beamforming Characteristics In Isotropic And Composite Plate Structures For Use In Structural Health Monitoring, Sarah Ketchersid
Doctoral Dissertations and Master's Theses
Structural health monitoring in plate-like simple structures using phased array beamsteering of guided Lamb waves is useful in damage detection and evaluation efforts. Lamb waves can be effectively used for beamsteering using a linear array. The experimentation primarily focuses on beamsteering in the aluminum panel, which involves developing a simulation based on extracted data to visualize the dispersion of waves across the panel. By evaluating parameters such as slowness, velocity, and amplitude direction and variation for a specific metallic plate, the wavefront generated by a single wave source can be represented as a function of propagation angle and distance from …
Understanding Lightning Damage Formation In A Carbon-Epoxy Pultruded Rod Stitched Efficient Unitized Structure (Prseus) Composite,
2024
Texas A&M University
Understanding Lightning Damage Formation In A Carbon-Epoxy Pultruded Rod Stitched Efficient Unitized Structure (Prseus) Composite, Dounia Boushab, Aniket Mote, Khari Harrison, Juhyeong Lee, Charles U. Pittman Jr., Thomas E. Lacy Jr.
Mechanical and Aerospace Engineering Faculty Publications
Lightning damage to composite aircraft structures results from a concurrent and sequential interaction between arc discharge multi-physics and the anisotropic electrical and thermal composite properties. In this study, the impact of nominal 50 and 125 kA lightning strikes on damage formation in a carbon-epoxy Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) was investigated. A combination of visual inspection, ultrasonic phased array testing, destructive sectioning, and various microscopy techniques was employed to characterize the damage. Localized damage, including severe matrix decomposition, melting of polyester warp-knitting yarns, fiber splitting, and large-scale delamination, was confined to the immediate vicinity of the lightning attachment …
A Machine Learning Model Of Perturb-Seq Data For Use In Space Flight Gene Expression Profile Analysis,
2024
Purdue University
A Machine Learning Model Of Perturb-Seq Data For Use In Space Flight Gene Expression Profile Analysis, Liam F. Johnson, James Casaletto, Lauren Sanders, Sylvain Costes
Graduate Industrial Research Symposium
The genetic perturbations caused by spaceflight on biological systems tend to have a system-wide effect which is often difficult to deconvolute it into individual signals with specific points of origin. Single cell multi-omic data can provide a profile of the perturbational effects, but does not necessarily indicate the initial point of interference within the network. The objective of this project is to take advantage of large scale and genome-wide perturbational datasets by using them to train a tuned machine learning model that is capable of predicting the effects of unseen perturbations in new data. Perturb-Seq datasets are large libraries of …
Farmer Perceptions Of Land Cover Classification Of Uas Imagery Of Coffee Agroecosystems In Puerto Rico,
2024
Embry-Riddle Aeronautical University
Farmer Perceptions Of Land Cover Classification Of Uas Imagery Of Coffee Agroecosystems In Puerto Rico, Jose Cabrera, Blake Neal, Kevin Adkins, Ronny Schroeder, Gwendolyn Klenke, Shannon Brines, Nayethzi Hernandez, Kevin Li, Riley Glancy, Ivette Perfecto
Publications
Highly diverse agroecosystems are increasingly of interest as the realization of farms’ invaluable ecosystem services grows. Simultaneously there has been an increased use of uncrewed aerial systems (UAS) in remote sensing as drones offer a finer spatial resolution and faster revisit rate than traditional satellites. With the combined utility of UAS and the attention on agroecosystems, there exists an opportunity to assess UAS practicality in highly biodiverse settings. In this study, we utilized UAS to collect fine-resolution 10-band multispectral imagery of coffee agroecosystems in Puerto Rico. We created land cover maps through a pixel-based supervised classification of each farm and …
Relative Vectoring Using Dual Object Detection For Autonomous Aerial Refueling,
2024
Air Force Institute of Technology
Relative Vectoring Using Dual Object Detection For Autonomous Aerial Refueling, Derek B. Worth, Jeffrey L. Choate, James Lynch, Scott L. Nykl, Clark N. Taylor
Faculty Publications
Once realized, autonomous aerial refueling will revolutionize unmanned aviation by removing current range and endurance limitations. Previous attempts at establishing vision-based solutions have come close but rely heavily on near perfect extrinsic camera calibrations that often change midflight. In this paper, we propose dual object detection, a technique that overcomes such requirement by transforming aerial refueling imagery directly into receiver aircraft reference frame probe-to-drogue vectors regardless of camera position and orientation. These vectors are precisely what autonomous agents need to successfully maneuver the tanker and receiver aircraft in synchronous flight during refueling operations. Our method follows a common 4-stage process …
Optimal Abort Guidance And Experimental Verification Based On Feature Learning,
2024
Missouri University of Science and Technology
Optimal Abort Guidance And Experimental Verification Based On Feature Learning, Vinay Kenny, Sixiong You, Chaoying Pei, Godfrey Hendrix, Roha Gul, Ran Dai, Jeremy Rea
Mechanical and Aerospace Engineering Faculty Research & Creative Works
The abort mission refers to the mission where the landing vehicle needs to terminate the landing mission when an anomaly happens and be safely guided to the desired orbit. This paper focuses on solving the time-optimal abort guidance (TOAG) problem in real-time via the feature-based learning method. First, according to the optimal control theory, the features are identified to represent the optimal solutions of TOAG using a few parameters. After that, a sufficiently large data set of time-optimal abort trajectories is generated offline by solving the TOAG problems with different initial conditions. Then, the features are extracted for all generated …
Hardware-In-The-Loop Autonomous Trajectory Generations For On-Orbit Rendezvous And Proximity Operations,
2024
Air Force Institute of Technology
Hardware-In-The-Loop Autonomous Trajectory Generations For On-Orbit Rendezvous And Proximity Operations, Connor Slattery
Theses and Dissertations
Utilizing the C++ version of GPOPS within a robotic operating system to assess efficacy on flight-ready hardware is a vital interest of the space industry today. The findings in this paper show the ability of employing GPOPS in C++ on flight-ready hardware, leveraging optimal control as the main driver to creating a control pipleline to allow a robotic platform to generate and follow an optimized trajectory with minimal user input.
Characterization Of Additively Manufactured Ti-6al-4v Yield Behavior And The Influence Of Varied Build Layer Heights,
2024
Air Force Institute of Technology
Characterization Of Additively Manufactured Ti-6al-4v Yield Behavior And The Influence Of Varied Build Layer Heights, Joseph Puglisi
Theses and Dissertations
This study evaluates the yield behavior of additively manufactured Ti-6-4 specimens in combined loading. Specimens were probed for yield across multiple load combinations along a given yield surface, holding pin one mode while applying load increments in the other mode until yield was detected. In combined loading, the yield surfaces across varied print parameters showed statistically significant, but negligible differences. This research sought to characterize the yield behavior across print parameters with the goal of increasing manufacturability. Ultimately, the benefits of the smaller print powder did not outweigh the increased manufacturing time. Furthermore, the comparison of material behavior in subsequent …
Trajectory Optimization Via Direct Collocation Methods Of Boost-Glide Vehicle With Newtonian Aerodynamic Model,
2024
Air Force Institute of Technology
Trajectory Optimization Via Direct Collocation Methods Of Boost-Glide Vehicle With Newtonian Aerodynamic Model, Andrew Bonavita
Theses and Dissertations
In this work, a Newtonian aerodynamic model was developed for an elliptic cone glide geometry at a variety of angles of attack, and a functional relationship between an input angle of attack and the vehicle lift and drag coefficients was developed. This model was used in a direct orthogonal collocation framework to simulate a series of boost-glide trajectories, with objectives of minimum distance to target, minimum time to target, and maximum velocity to target. The optimal control problem was then expanded into a reachability study, considering a wide range of additional scenarios, along with studies on the vehicle range capabilities. …
Computational Modeling Of Single Shear Bolted Joints In Hybrid Composite Laminates With And Without Film Adhesive,
2024
Air Force Institute of Technology
Computational Modeling Of Single Shear Bolted Joints In Hybrid Composite Laminates With And Without Film Adhesive, Cameron S. Mcmahan
Theses and Dissertations
This research explores the effectiveness of predicting composite failure subject to quasi-static loading conditions using computational methods. FEA models were created using Abaqus and were employed to predict composite yield and initial failure behavior. Boundary conditions are generated to replicate the loading scenario seen in the experimental tests. Computationally predicted structural response of the composite range in accuracy from a 2% difference compared to experimental values to a maximum of 63%.
Positioning, Navigation, And Timing (Pnt) Study For Select Multibody Environments,
2024
Air Force Institute of Technology
Positioning, Navigation, And Timing (Pnt) Study For Select Multibody Environments, Kaitlin R. Roberts
Theses and Dissertations
In the renewed 21st-century race to the Moon, the demand for heightened mission capabilities in the cislunar region, lunar surface, and beyond is imperative. With an escalating number and complexity of lunar missions, persistent positioning, navigation, and timing (PNT) capabilities are becoming paramount. This thesis presents innovative lunar PNT architectures designed to provide continuous coverage of the lunar South Pole, near-continuous coverage of the entire lunar surface, and coverage of the Earth-Moon Corridor. As space faring countries advance from lunar exploration to Mars, similar assets are essential for astronaut exploration in this extraterrestrial environment. Additionally, this thesis introduces and meticulously …
Statistical Reliability Estimation Of Space Launch Vehicles,
2024
Air Force Institute of Technology
Statistical Reliability Estimation Of Space Launch Vehicles, Brooke N. Wagenblast
Theses and Dissertations
Space launch vehicle reliability is imperative to understand since launch vehicles are crucial in getting payloads into space for a hopefully successful mission. This thesis examines the reliability of commercial, civil, and military space launch vehicles through trend analysis and a variety of statistical methods. Data sets obtained from the Seradata database are analyzed for trends by looking at data subsets including launch date, launch country, final mission orbit, section (commercial, civil or military), launch vehicle family and failed subsystem. First-level Bayesian analysis and mean success rates are performed, primarily split up by launch vehicle family and total launches, and …
Discerning Satellite Subsystem Costs To Improve Cost Estimation,
2024
Air Force Institute of Technology
Discerning Satellite Subsystem Costs To Improve Cost Estimation, Ryan A. Candella
Theses and Dissertations
The race for supremacy in the space environment is accelerating, with the United States taking a significant step by establishing its dedicated military branch for space operations. Achieving dominance in this realm relies on efficiently managing costs and securing rapid funding to initiate new programs. One step towards accomplishing this goal is to comprehend the cost distribution across the primary components of a Space Vehicle Bus and to delve into lower-level Work Breakdown Structure (WBS) elements for more precise and expeditious cost estimations. To achieve this, descriptive statistics for a variety of Bus subsystem WBS elements are provided in this …
Standardization Of Risk Classifications For Unmanned Space Vehicle Missions,
2024
Air Force Institute of Technology
Standardization Of Risk Classifications For Unmanned Space Vehicle Missions, Collin A. Gwaltney
Theses and Dissertations
This paper seeks to model risk classification levels (A-D) for 122 Space Vehicle programs. Models include multinomial logistic regression as well as random forest, a machine learning technique based on decision trees. We use independent variables (IVs) which are theoretically correlated to risk class for the regression and one random forest model. We then include all IVs and allow the random forest technique to use those which provide the most information on risk class before paring down the number of IVs to only 7. We show that the accuracy of predictions increases from 62% to 87% by using random forest …
