Browsing by Author "Williams, Keith A"
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Item Analysis and Elicitation of Electroencephalogram Data Pertaining to High Alert and Stressful Situations: Source Localization Through the Inverse Problem(University of Alabama Libraries, 2021) Heim, Isaac C; Fonseca, Daniel J.; University of Alabama TuscaloosaThis dissertation work deals with the design and development of a fuzzy controller to analyze electroencephalogram (EEG) data. The fuzzy controller made use of the multiple functions associated with the different regions of the brain to correlate multiple Brodmann areas to multiple outputs. This controller was designed to adapt to any data imported into it. The current framework implemented supports a math study and a police officer study. The rules for the interactions of the Brodmann areas have been set up for these applications, detailing how well the police subjects’ brains exhibited behavior indicative to activation relating to vision, memory, shape/distance, hearing/sound, and theory of mind. The math subjects’ outputs were attuned to their related study which involved transcranial direct current stimulation (tDCS), which is a form of neurostimulation. Anode affinity, cathode affinity, calculation, memory, and decision making were the outputs focused on for the math study. This task is best suited to a fuzzy controller since interactions between Brodmann areas can be analyzed and the contributions of each area accounted for.The goal of the controller was to determine long-term behavior of the subjects with repeated sampling. With each addition of data, the controller was able to develop new bounds related to the current condition of the data in the study. Processing this data was accomplished by the creation of an automated filtering script for EEGLAB in MATLAB. The script was designed to rapidly load and filter the files associated with any given dataset. These files were also automatically prepared for analysis with a program called Low Resolution Brain Electromagnetic Tomography i.e. (LORETA). LORETA was used to solve the inverse problem, which involves identifying where the signals from the surface electrodes originated within the brain through a process called source localization. Once the sources of the EEG signals were located, they were associated with the Brodmann areas. The fuzzy controller then processed this information to automatically generate heat maps which displayed information such as normalized data, z-score, and rankings. Each set of scores displays how the subject's brain was acting, which lined up with the expected results.Item Intelligent Motion Control, Intent Recognition, and Design of Innovative Wearable Robots(University of Alabama Libraries, 2023) Haque, Md Rejwanul; Shen, XiangrongWearable robots designed to augment, replace, or interact with the human body, have the potential to improve the quality of life; specifically, lower-limb robotic prostheses and exoskeletons can assist mobility-challenged individuals to walk more efficiently, and securely. However, the effectiveness of wearable robots is severely limited by the performance of the robot control system. This research aims to address some of the significant challenges related to the high-level control along with the hardware development of such wearable robots.One of the major challenges in high-level prosthesis controller development is the reliable gait data collection in real-world scenarios, while existing state of the art motion capture-based gait measurement is limited to laboratory environment. To address this challenge, two wearable devices were developed to study human locomotion for the development of an intelligent prosthesis controller.The first one is a novel exoskeleton-based portable gait data collection system. This device provides the capability of high accuracy and reliable gait measurement without the need for stationary instrumentation. Utilizing this exo-skeleton system, a multi-modal gait data collection study was conducted to develop a method for identifying a human's intended mode of motion or intermodal transition for the prosthesis control purpose. This work presents a new multi-dimensional dynamic time warping (mDTW)-based intent recognizer to provide high-accuracy recognition of the locomotion mode/mode transition sufficiently early in the gait cycle ensuring seamless control of the prosthesis.The second one is a shoe-based novel wearable sensor, namely Smart Lacelock device that can provide reliable measurement of the overall motion of the wearer's along with valuable information related to the ankle movement and the foot loading which can potentially be used in the adaptive control of wearable assistive devices.To provide a complete wearable robotic solution for the mobility challenged individuals, this research developed robotic lower limb prostheses and orthosis. The robotic lower limb prostheses in this work adopted a unique design framework of Common Core Components Knee-Ankle Prosthesis. This unified prosthesis is cost effective and light weight while ensures desired dynamic performance of healthy human-like walking. To measure the prosthesis structural load, as well as to quantify the interaction of the amputee user with the environment for prosthesis control purposes, a Force Moment Prosthesis Load Sensor was developed.Finally, this dissertation presents a robotic ankle-foot orthosis, which is essentially a wearable robot that acts in parallel to the user's biological ankle for motion assistance and has complete energy autonomy.Item Mass Flow Control of an Iodine Feed System for an Electrostatic Thruster Using a Throttling Duct and Continuous Ceramic Heating(University of Alabama Libraries, 2023) Sponer, Victor Thomas; Branam, Richard DIodine is an adequate and upcoming replacement for noble gases in their use as propellant in electric propulsion engines. Iodine brings a high molecular mass, low ionization energies, and high storage density to increase the efficiency of our propellant load. Despite the benefits, iodine presents many challenges in storage and transport due its complex chemical properties and high volatility, causing abrupt changes in mass flow and mission lifetime due to chemical reactions. This report aims to design and test a storage vessel and thermally controlled feed system that includes a throttling duct tube for choked flow conditions, and the process of designing, manufacturing, and assembly is underlined. The feed system generated iodine vapor for over 10 different temperature profiles ranging from varied propellant and throttling duct temperatures for around 30 different data points. Thermal control systems kept average feed temperatures within a degree Celsius of input, with upstream components varying up to 10°C from themselves and throttling duct varying 20°C between inlet and outlet in most cases. Computational flow simulations determined preliminary mass flow rates based on high upstream pressures. Experimental data did not reach these pressures greater than 20 Torr and stayed between 7-12 Torr. New simulations showed trends in mass flow rates that reflect the variation shown by experimental data averages, varying by one standard deviation for all but two temperature profiles. These simulations did not reflect the mass flow rates observed by only changing the throttling duct temperature.Item Using Skin-Mounted Microphones for Reconstructing in Vivo Interskeletal Forces: A Feasibility Study(University of Alabama Libraries, 2020) McChristian, Brandon; Shepard, William S; University of Alabama TuscaloosaThis study investigates the feasibility of using a non-invasive external measurement technique utilizing microphones on the surface of human skin to enable characterization of forces transferred through bone structures during natural motion. While the measurement of forces within the skeleton during human movement is of great interest to researchers and clinicians alike, the requirement for non-invasive sensors does not allow for direct measurement of these forces. The conventional inverse dynamical method of determining internal bone-on-bone forces in biomechanics can be limiting due to the necessity of performing measurements in a laboratory environment and the reliance on a link-segment model, which tends to propagate error. The novel method investigated in this study involves the measurement of pressure waves that propagate through human soft tissue during dynamic loading of the skeletal frame. This research uses a simplified anatomical test specimen consisting of a hollow aluminum bar cast in ballistic gelatin, representing a femur and the surrounding soft tissues, to experimentally examine the feasibility of this new measurement technique. In these tests, an impact force representing interskeletal forces is applied to the bar with an impact hammer and surface-mounted electret microphones measure the resulting pressure waves transferred to the surface of the ballistic gel. Feasibility of the measurement technique was determined by applying least squares regression fits to measured acoustic autospectral data treated as a function of impact force characteristics in the time-domain. The acoustic autospectral amplitudes and energy in frequency bands were found to be highly correlated with both the peak impact force and impulse. Ultimately, results show that the measurement technique is feasible, thus providing a motivation for the development of more advanced inverse methods utilizing this measurement technique.