Matching Items (707)
Filtering by

Clear all filters

161495-Thumbnail Image.png
Description
In human-autonomy teams (HATs), the human needs to interact with one or more autonomous agents, and this new type of interaction is different than the existing human-to-human interaction. Next Generation Combat Vehicles (NGCVs), which are envisioned for the U.S. military are associated with the concept of HAT. As NGCVs are

In human-autonomy teams (HATs), the human needs to interact with one or more autonomous agents, and this new type of interaction is different than the existing human-to-human interaction. Next Generation Combat Vehicles (NGCVs), which are envisioned for the U.S. military are associated with the concept of HAT. As NGCVs are in the early stage of development, it is necessary to develop different training methods and measures for team effectiveness. The way team members communicate and task complexity are factors affecting team efficiency. This study analyzes the impact of two interaction strategies and task complexity on team situation awareness among 22 different teams. Teams were randomly assigned different interaction conditions and went through two missions to finish their assigned tasks. Results indicate that the team with the procedural interaction strategy had better team situation awareness according to the Coordinated Awareness of the Situation by Teams (CAST) scores on the artillery calls. However, the difference between the strategies was not found on CAST scores of perturbations, map accuracy, or Situation Awareness Global Assessment Technique (SAGAT) scores. Additionally, the impact of task complexity on the team situation awareness was not found. Implications and suggestions for future work are discussed.
ContributorsKim, Jimin (Author) / Gutzwiller, Rober (Thesis advisor) / Cooke, Nancy (Committee member) / Gray, Robert (Committee member) / Arizona State University (Publisher)
Created2021
161363-Thumbnail Image.png
Description
Two fatigue life prediction methods using the energy-based approach have been proposed. A number of approaches have been developed in the past five decades. This study reviews some common models and discusses the model that is most suitable for each different condition, no matter whether the model is designed

Two fatigue life prediction methods using the energy-based approach have been proposed. A number of approaches have been developed in the past five decades. This study reviews some common models and discusses the model that is most suitable for each different condition, no matter whether the model is designed to solve uniaxial, multiaxial, or biaxial loading paths in fatigue prediction. In addition, different loading cases such as various loading and constant loading are also discussed. These models are suitable for one or two conditions in fatigue prediction. While most of the existing models can only solve single cases, the proposed new energy-based approach not only can deal with different loading paths but is applicable for various loading cases. The first energy-based model using the linear cumulative rule is developed to calculate random loading cases. The method is developed by combining Miner’s rule and the rainflow-counting algorithm. For the second energy-based method, I propose an alternative method and develop an approach to avert the rainflow-counting algorithm. Specifically, I propose to use an energy-based model by directly using the time integration concept. In this study, first, the equivalent energy concept that can transform three-dimensional loading into an equivalent loading will be discussed. Second, the new damage propagation method modified by fatigue crack growth will be introduced to deal with cycle-based fatigue prediction. Third, the time-based concept will be implemented to determine fatigue damage under every cycle in the random loading case. The formulation will also be explained in detail. Through this new model, the fatigue life can be calculated properly in different loading cases. In addition, the proposed model is verified with experimental datasets from several published studies. The data include both uniaxial and multiaxial loading paths under constant loading and random loading cases. Finally, the discussion and conclusion based on the results, are included. Additional loading cases such as the spectrum including both elastic and plastic regions will be explored in future research.
ContributorsTien, Shih-Chuan (Author) / Liu, Yongming (Thesis advisor) / Nian, Qiong (Committee member) / Jiao, Yang (Committee member) / Arizona State University (Publisher)
Created2021
161364-Thumbnail Image.png
Description
The Inverted Pendulum on a Cart is a classical control theory problem that helps understand the importance of feedback control systems for a coupled plant. In this study, a custom built pendulum system is coupled with a linearly actuated cart and a control system is designed to show the stability

The Inverted Pendulum on a Cart is a classical control theory problem that helps understand the importance of feedback control systems for a coupled plant. In this study, a custom built pendulum system is coupled with a linearly actuated cart and a control system is designed to show the stability of the pendulum. The three major objectives of this control system are to swing up the pendulum, balance the pendulum in the inverted position (i.e. $180^\circ$), and maintain the position of the cart. The input to this system is the translational force applied to the cart using the rotation of the tires. The main objective of this thesis is to design a control system that will help in balancing the pendulum while maintaining the position of the cart and implement it in a robot. The pendulum is made free rotating with the help of ball bearings and the angle of the pendulum is measured using an Inertial Measurement Unit (IMU) sensor. The cart is actuated by two Direct Current (DC) motors and the position of the cart is measured using encoders that generate pulse signals based on the wheel rotation. The control is implemented in a cascade format where an inner loop controller is used to stabilize and balance the pendulum in the inverted position and an outer loop controller is used to control the position of the cart. Both the inner loop and outer loop controllers follow the Proportional-Integral-Derivative (PID) control scheme with some modifications for the inner loop. The system is first mathematically modeled using the Newton-Euler first principles method and based on this model, a controller is designed for specific closed-loop parameters. All of this is implemented on hardware with the help of an Arduino Due microcontroller which serves as the main processing unit for the system.
ContributorsNamasivayam, Vignesh (Author) / Tsakalis, Konstantinos (Thesis advisor) / Rodriguez, Armando (Committee member) / Si, Jennie (Committee member) / Shafique, Md. Ashfaque Bin (Committee member) / Arizona State University (Publisher)
Created2021
161788-Thumbnail Image.png
Description
Collision-free path planning is also a major challenge in managing unmanned aerial vehicles (UAVs) fleets, especially in uncertain environments. The design of UAV routing policies using multi-agent reinforcement learning has been considered, and propose a Multi-resolution, Multi-agent, Mean-field reinforcement learning algorithm, named 3M-RL, for flight planning, where multiple vehicles need

Collision-free path planning is also a major challenge in managing unmanned aerial vehicles (UAVs) fleets, especially in uncertain environments. The design of UAV routing policies using multi-agent reinforcement learning has been considered, and propose a Multi-resolution, Multi-agent, Mean-field reinforcement learning algorithm, named 3M-RL, for flight planning, where multiple vehicles need to avoid collisions with each other while moving towards their destinations. In this system, each UAV makes decisions based on local observations, and does not communicate with other UAVs. The algorithm trains a routing policy using an Actor-Critic neural network with multi-resolution observations, including detailed local information and aggregated global information based on mean-field. The algorithm tackles the curse-of-dimensionality problem in multi-agent reinforcement learning and provides a scalable solution. The proposed algorithm is tested in different complex scenarios in both 2D and 3D space and the simulation results show that 3M-RL result in good routing policies. Also as a compliment, dynamic data communications between UAVs and a control center has also been studied, where the control center needs to monitor the safety state of each UAV in the system in real time, where the transition of risk level is simply considered as a Markov process. Given limited communication bandwidth, it is impossible for the control center to communicate with all UAVs at the same time. A dynamic learning problem with limited communication bandwidth is also discussed in this paper where the objective is to minimize the total information entropy in real-time risk level tracking. The simulations also demonstrate that the algorithm outperforms policies such as a Round & Robin policy.
ContributorsWang, Weichang (Author) / Ying, Lei (Thesis advisor) / Liu, Yongming (Thesis advisor) / Zhang, Junshan (Committee member) / Zhang, Yanchao (Committee member) / Arizona State University (Publisher)
Created2021
161871-Thumbnail Image.png
Description
Functional materials can be characterized as materials that have tunable properties and are attractive solutions to the improvement and optimization of processes that require specific physiochemical characteristics. Through tailoring and altering these materials, their characteristics can be fine-tuned for specific applications. Computational modeling proves to be a crucial methodology in

Functional materials can be characterized as materials that have tunable properties and are attractive solutions to the improvement and optimization of processes that require specific physiochemical characteristics. Through tailoring and altering these materials, their characteristics can be fine-tuned for specific applications. Computational modeling proves to be a crucial methodology in the design and optimization of such materials. This dissertation encompasses the utilization of molecular dynamics simulations and quantum calculations in two fields of functional materials: electrolytes and semiconductors. Molecular dynamics (MD) simulations were performed on ionic liquid-based electrolyte systems to identify molecular interactions, structural changes, and transport properties that are often reflected in experimental results. The simulations aid in the development process of the electrolyte systems in terms of concentrations of the constituents and can be invoked as a complementary or predictive tool to laboratory experiments. The theme of this study stretches further to include computational studies of the reactivity of atomic layer deposition (ALD) precursors. Selected aminosilane-based precursors were chosen to undergo density functional theory (DFT) calculations to determine surface reactivity and viability in an industrial setting. The calculations were expanded to include the testing of a semi-empirical tight binding program to predict growth per cycle and precursor reactivity with a high surface coverage model. Overall, the implementation of computational methodologies and techniques within these applications improves materials design and process efficiency while streamlining the development of new functional materials.
ContributorsGliege, Marisa Elise (Author) / Dai, Lenore (Thesis advisor) / Derecskei-Kovacs, Agnes (Thesis advisor) / Muhich, Christopher (Committee member) / Emady, Heather (Committee member) / Zhuang, Houlong (Committee member) / Arizona State University (Publisher)
Created2021
161818-Thumbnail Image.png
Description
Color perception has been widely studied and well modeled with respect to combining visible electromagnetic frequencies, yet new technology provides the means to better explore and test novel temporal frequency characteristics of color perception. Experiment 1 tests how reliably participants categorize static spectral rainbow colors, which can be a useful

Color perception has been widely studied and well modeled with respect to combining visible electromagnetic frequencies, yet new technology provides the means to better explore and test novel temporal frequency characteristics of color perception. Experiment 1 tests how reliably participants categorize static spectral rainbow colors, which can be a useful tool for efficiently identifying those with functional dichromacy, trichromacy, and tetrachromacy. The findings confirm that all individuals discern the four principal opponent process colors, red, yellow, green, and blue, with normal and potential tetrachromats seeing more distinct colors than color blind individuals. Experiment 2 tests the moving flicker fusion rate of the central electromagnetic frequencies within each color category found in Experiment 1 as a test of the Where system. It then compares this to the maximum temporal processing rate for discriminating direction of hue change with colors displayed serially as a test of the What system. The findings confirm respective processing thresholds of about 20 Hz for Where and 2-7 Hz for What processing systems. Experiment 3 tests conditions that optimize false colors based on the spinning Benham’s Top illusion. Findings indicate the same four principal colors emerge as in Experiment 1, but at low saturation levels for trichromats that diminish further for dichromats. Taken together, the three experiments provide an overview of the common categorical boundaries and temporal processing limits of human color vision.
ContributorsKrynen, Richard Chandler (Author) / Mcbeath, Michael K (Thesis advisor) / Homa, Donald (Committee member) / Newman, Nathan (Committee member) / Stone, Greg (Committee member) / Arizona State University (Publisher)
Created2021
161828-Thumbnail Image.png
Description
Modern radio frequency (RF) sensors are digital systems characterized by wide band frequency range, and capable to perform multi-function tasks such as: radar, electronic warfare (EW), and communications simultaneously on different sub-arrays. This demands careful understanding of the behavior of each sub-system and how each sub-array interacts with the others.

Modern radio frequency (RF) sensors are digital systems characterized by wide band frequency range, and capable to perform multi-function tasks such as: radar, electronic warfare (EW), and communications simultaneously on different sub-arrays. This demands careful understanding of the behavior of each sub-system and how each sub-array interacts with the others. A way to estimate and measure the active reflection coefficient (ARC) to calculate the active voltage standing wave ratio (VSWR) of multiple input multiple output (MIMO) radar when elements (or sub-arrays) are driven with different waveforms has been developed. This technique will help to understand and incorporate bounds in the design of MIMO systems and its waveforms to avoid damages by large power reflections and to improve system performance. The methodology developed consists of evaluating the active VSWR at each individual antenna element or sub-array from (1) estimates of the ARC by using computational electromagnetic (CEM) tools or (2) by directly measuring the ARC at each antenna element or sub-array. The former methodology is important especially at the design phase where trade offs between element shapes and geometrical configurations are taking place. The former methodology is expanded by directly measuring ARC using an experimental radar testbed Baseband-digital at Every Element MIMO Experimental Radar (BEEMER) system to assess the active VSWR, side-lobe levels and antenna pattern effects when different waveforms are transmitted. An optimization technique is implemented to mitigate the effects of the ARC in co-located MIMO radars by waveform design.
ContributorsColonDiaz, Nivia (Author) / Aberle, James T. (Thesis advisor) / Bliss, Daniel W. (Thesis advisor) / Diaz, Rodolfo (Committee member) / Janning, Dan (Committee member) / Arizona State University (Publisher)
Created2021
161844-Thumbnail Image.png
Description
Thermal management is a critical aspect of microelectronics packaging and often centers around preventing central processing units (CPUs) and graphics processing units (GPUs) from overheating. As the need for power going into these processors increases, so too does the need for more effective thermal management strategies. One such strategy is

Thermal management is a critical aspect of microelectronics packaging and often centers around preventing central processing units (CPUs) and graphics processing units (GPUs) from overheating. As the need for power going into these processors increases, so too does the need for more effective thermal management strategies. One such strategy is to utilize additive manufacturing to fabricate heat sinks with bio-inspired and cellular structures and is the focus of this thesis. In this study, a process was developed for manufacturing the copper alloy CuNi2SiCr on the 100w Concept Laser Mlab laser powder bed fusion 3D printer to obtain parts that were 94% dense, while dealing with challenges of low absorptivity in copper and its high potential for oxidation. The developed process was then used to manufacture and test heat sinks with traditional pin and fin designs to establish a baseline cooling effect, as determined from tests conducted on a substrate, CPU and heat spreader assembly. Two additional heat sinks were designed, the first of these being bio-inspired and the second incorporating Triply Periodic Minimal Surface (TPMS) cellular structures, with the aim of trying to improve the cooling effect relative to commercial heat sinks. The results showed that the pure copper commercial pin-design heat sink outperformed the additive manufactured (AM) pin-design heat sink under both natural and forced convection conditions due to its approximately tenfold higher thermal conductivity, but that the gap in performance could be bridged using the bio-inspired and Schwarz-P heat sink designs developed in this work and is an encouraging indicator that further improvements could be obtained with improved alloys, heat treatments and even more innovative designs.
ContributorsYaple, Jordan Marie (Author) / Bhate, Dhruv (Thesis advisor) / Azeredo, Bruno (Committee member) / Phelan, Patrick (Committee member) / Arizona State University (Publisher)
Created2021
161909-Thumbnail Image.png
Description
Millions of people around the world daily engage in artisanal and small-scale gold mining (ASGM)––a vital part of total global gold production. For Colombia, this mining accounts for most of the precious metal’s output. It has also made Colombia, per capita, the worst mercury-polluted country in the world. Though cleaner,

Millions of people around the world daily engage in artisanal and small-scale gold mining (ASGM)––a vital part of total global gold production. For Colombia, this mining accounts for most of the precious metal’s output. It has also made Colombia, per capita, the worst mercury-polluted country in the world. Though cleaner, safer, and more effective methods exist, miners yet opt for mercury-use. Any success with interventions in technology, capacitation, or policy has been limited. This dissertation attends to mercury-use in ASGM in Antioquia, Colombia, via two gaps: a descriptive one (i.e., a failure to pay attention to, and to describe, actual practices in ASGM); and, a theoretical one (i.e., explanations as to why some decisions, including but not limited to policy, succeed or fail). In addition to an ecology of practices, embodiment, and situated knowledges, phenomenological interviews with stakeholders illuminate critical lived experience, as well as whether or how it is possible to reduce mercury-use and contamination. Furthermore, a novel application of speculative sound supplements this work. Finally, key findings complement existing scholarship. The presence of gold drives mining, but an increase in mining comes at a cost. Miners know mercury is hazardous, but mining legally, or formally, has proven too onerous. So, mercury-use persists: it is profitable, and the effects on human health can seem delayed. The state is pivotal to change in mercury-use, but its approach has been punitive. Change will invariably require greater attention to the lived experiences of miners.
ContributorsPimentel, Matthew (Author) / Fonow, Mary Margaret (Thesis advisor) / Parmentier, Mary Jane (Thesis advisor) / Coleman, Grisha (Committee member) / Arizona State University (Publisher)
Created2021
161730-Thumbnail Image.png
Description
Robotic assisted devices in gait rehabilitation have not seen penetration into clinical settings proportionate to the developments in this field. A possible reason for this is due to the development and evaluation of these devices from a predominantly engineering perspective. One way to mitigate this effect is to further include

Robotic assisted devices in gait rehabilitation have not seen penetration into clinical settings proportionate to the developments in this field. A possible reason for this is due to the development and evaluation of these devices from a predominantly engineering perspective. One way to mitigate this effect is to further include the principles of neurophysiology into the development of these systems. To further include these principles, this research proposes a method for grounded evaluation of three machine learning algorithms to gain insight on what modeling approaches are able to both replicate therapist assistance and emulate therapist strategies. The algorithms evaluated in this paper include ordinary least squares regression (OLS), gaussian process regression (GPR) and inverse reinforcement learning (IRL). The results show that grounded evaluation is able to provide evidence to support the algorithms at a higher resolution. Also, it was observed that GPR is likely the most accurate algorithm to replicate therapist assistance and to emulate therapist adaptation strategies.
ContributorsSmith, Mason Owen (Author) / Zhang, Wenlong (Thesis advisor) / Ben Amor, Hani (Committee member) / Sugar, Thomas (Committee member) / Arizona State University (Publisher)
Created2021