Theses and Dissertations from UMD
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New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM
More information is available at Theses and Dissertations at University of Maryland Libraries.
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Item COMPUTATIONAL THINKING IN EARLY GRADE CLASSROOMS: HOW YOUNG LEARNERS INTERACT WITH PHYSICAL DEVICES TO GROUND THEIR UNDERSTANDING OF COMPUTATIONAL THINKING(2024) Bih epse Fofang, Janet Shufor; Weintrop, David; Education Policy, and Leadership; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Computational thinking (CT) has been supported as an important skill every young person should possess for the 21st century, with possible implications for problem-solving, self-expression, and creativity. Numerous initiatives, both within and outside classroom settings, have been developed in response to policy mandates aiming at broadening participation for all K-12 learners to acquire CT skills. Consequently, there has been a proliferation of computational toys and tools specifically designed for young learners, including codable robots introduced into classrooms and educational environments. With the growing prevalence of computational devices in educational settings, educators, curriculum designers, and researchers must cultivate diverse teaching approaches and deepen their understanding of how young learners engage with these devices to acquire CT skills effectively within classroom contexts. In this dissertation, I present findings of how elementary-grade learners develop CT skills when they program Sphero robots in mathematics classroom activities. I specifically focused on the kinds of representations students developed, considering their perspectives (understanding) of the environment, and the practices they engaged in to accomplish given tasks.To understand how young learners acquired CT skills, I observed fourth-grade learners as they interacted with activities on the Sphero.Math curriculum to program the Sphero robot in mathematics classrooms. The Sphero.Math curriculum was developed through a collaborative effort between researchers and DCPS partners. Findings from this work revealed that representations play an important role in supporting young learners to engage in CT practices such as Pattern recognition, algorithm design, problem decomposition, and abstraction (PRADA). Findings showed that representations such as (1) concrete manipulatives, (2) language, (3) graphic, (4) symbolic and (5) embodied representations provide scaffolds for learners to gain (PRADA), CT skills through iterating, testing, debugging, abstracting, modularizing, and reusing code. Additionally, the design features of the Sphero robot and its programming environment support CT knowledge acquisition. Features such as (1) programmable LEDs provided opportunities for learners to break down tasks and create opportunities to organize and structure components to get visual feedback that helped them recognize patterns. (2) Taillight (“aim”) LED provided visual cues, that facilitated the involvement of geocentric orientation and embodied practices that empowered students to establish sensorimotor references. (3) Sphero’s virtual protractor supported students through the CT component of abstraction to address the geocentric aspects of the Sphero robot. (4) block-based environment/language, that involves the use of shapes and colors as effective visual aids and abstraction tools, to support the learners’ construct to algorithms. This research can serve as a resource for researchers, curriculum designers, educators, and designers to answer questions about design, choice of computational tools, and their respective programming environments that can afford meaningful CT experiences. Familiarizing learners with representations within CT robotics learning environments serves as a gentle initiation into emerging topics in education such as AI, ML, and data science, given the pivotal role representations play within these fields.Item ESTIMATION AND CONTROL OF A DISTRIBUTED PARAMETER SYSTEM BY A TEAM OF MOBILE SENSORS AND ACTUATORS(2021) Cheng, Sheng; Paley, Derek A; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The recent development of mobile robots has dramatically extended the scenarios where robots can be deployed to complete tasks autonomously. One of the tasks is monitoring and controlling large-scale spatiotemporal processes, e.g., oil spills and forest fires, which is mainly conducted by human operators. These tasks can pose health threats, cause severe environmental issues, and incur substantial financial costs. Autonomous robots can free human operators from danger and complete tasks in a timely and economically efficient manner. In this dissertation, estimation and control of spatiotemporal processes using mobile sensors and actuators are studied. Spatiotemporal processes vary in both space and time, whose dynamics can be characterized by partial differential equations (PDEs). Since the state space of a PDE is infinite-dimensional, a system with PDE dynamics is also known as a distributed parameter system (DPS). The performance of the estimation and control of a DPS can be enhanced (compared to stationary sensors and actuators) due to the additional degree of freedom induced from the mobility of the sensors and actuators. However, the vehicles carrying sensors and actuators usually have limited onboard resources (e.g., fuels and batteries) whose usage requires judicious decisions. Hence, we propose a new optimization framework that addresses the goal of estimation and control of a spatiotemporal process while considering the limited onboard resources. In the first part of this dissertation, an optimization framework is proposed to control a DPS modeled by a 2D diffusion-advection equation using a team of mobile actuators. The framework simultaneously seeks optimal control of the DPS and optimal guidance of the mobile actuators such that a cost function associated with both the DPS and the mobile actuators is minimized subject to the dynamics of each. We establish conditions for the existence of a solution to the proposed problem. Since computing an optimal solution requires approximation, we also establish the conditions for convergence to the exact optimal solution of the approximate optimal solution. That is, when evaluating these two solutions by the original cost function, the difference becomes arbitrarily small as the approximation gets finer. Two numerical examples demonstrate the performance of the optimal control and guidance obtained from the proposed approach. In the second part of this dissertation, an optimization framework is proposed to design guidance for a possibly heterogeneous team of multiple mobile sensors to estimate a spatiotemporal process modeled by a 2D diffusion-advection process. Owing to the abstract linear system representation of the process, we apply the Kalman-Bucy filter for estimation, where the sensors provide linear outputs. We propose an optimization problem that minimizes the sum of the trace of the covariance operator of the Kalman-Bucy filter and a generic mobility cost of the mobile sensors, subject to the sensors' motion modeled by linear dynamics. We establish the existence of a solution to this problem. Moreover, we prove convergence to the exact optimal solution of the approximate optimal solution. That is, when evaluating these two solutions using the original cost function, the difference becomes arbitrarily small as the approximation gets finer. To compute the approximate solution, we use Pontryagin's minimum principle after approximating the infinite-dimensional terms originating from the diffusion-advection process. The approximate solution is applied in simulation to analyze how a single mobile sensor's performance depends on two important parameters: sensor noise variance and mobility penalty. We also illustrate the application of the framework to multiple sensors, in particular the performance of a heterogeneous team of sensors. In the third part of this dissertation, a cooperative framework for estimating and controlling a spatiotemporal process using collocated mobile sensors and actuators is proposed. We model the spatiotemporal process by a 2D diffusion equation that represents the dynamics. Measurement and actuation of the process dynamics are performed by mobile agents whose motion is described by single-integrator dynamics. The estimation and control framework is formulated using a Kalman filter and an optimization problem. The former uses sensor measurements to reconstruct the process state, while the latter uses the estimated state to plan the actuation and guidance of the mobile agents. The optimization problem seeks the actuation and guidance that minimize the sum of the quadratic costs of the process state, actuation input, and guidance effort. Constraints include the process and agent dynamics as well as actuation and speed bounds. The framework is implemented with the optimization problem solved periodically using a nonlinear program solver. Numerical studies analyze and evaluate the performance of the proposed framework using a nondimensional parameterization of the optimization problem. The framework is also implemented on an outdoor multi-quadrotor testbed with a simulated spatiotemporal process and synthetic measurement and actuation.Item EVALUATION OF A SPACE ROBOTICS CONTROL CONSOLE USING EYE TRACKING GLASSES(2020) Kracinovich, Casey; Akin, David; Aerospace Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This thesis seeks to evaluate the human factors of the design of the space robotics control console to be used at NASA Goddard in the OSAM-1 mission, using eye tracking glasses to gain insights into the ways in which operators interact with the various console elements. An experiment was performed in which trained robot operators wearing eye tracking glasses executed a simplified task on the ground, representative of an attention-intensive in-flight task. As the OSAM-1 mission is not scheduled to launch until 2023, the configuration of this console is still somewhat in flux, so this task was repeated three times in different possible console configurations. Drawing on previous eye tracking literature in combination with the gathered eye tracking data, conclusions were developed about this particular console and task, and more broadly, insights were gained into robot control console design in general.Item MULTI-VEHICLE ROUTE PLANNING FOR CENTRALIZED AND DECENTRALIZED SYSTEMS(2019) Patel, Ruchir; Herrmann, Jeffrey W; Azarm, Shapour; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Multi-vehicle route planning is the problem of determining routes for a set of vehicles to visit a set of locations of interest. In this thesis, we describe a study of a classical multi-vehicle route planning problem which compared existing solutions methods on min-sum (minimizing total distance traveled) and min-max (minimizing maximum distance traveled) cost objectives. We then extended the work in this study by adapting approaches tested to generate robust solutions to a failure-robust multi vehicle route planning problem in which a potential vehicle failure may require modifying the solution, which could increase costs. Additionally, we considered a decentralized extension to the multi-vehicle route planning problem, also known as the decentralized task allocation problem. The results of a computational study show that our novel genetic algorithm generated better solutions than existing approaches on larger instances with high communication quality.Item Seeing Behind The Scene: Using Symmetry To Reason About Objects in Cluttered Environments(2017) Ecins, Aleksandrs; Aloimonos, Yiannis; Computer Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Rapid advances in robotic technology are bringing robots out of the controlled environments of assembly lines and factories into the unstructured and unpredictable real-life workspaces of human beings. One of the prerequisites for operating in such environments is the ability to grasp previously unobserved physical objects. To achieve this individual objects have to be delineated from the rest of the environment and their shape properties estimated from incomplete observations of the scene. This remains a challenging task due to the lack of prior information about the shape and pose of the object as well as occlusions in cluttered scenes. We attempt to solve this problem by utilizing the powerful concept of symmetry. Symmetry is ubiquitous in both natural and man-made environments. It reveals redundancies in the structure of the world around us and thus can be used in a variety of visual processing tasks. In this thesis we propose a complete pipeline for detecting symmetric objects and recovering their rotational and reflectional symmetries from 3D reconstructions of natural scenes. We begin by obtaining a multiple-view 3D pointcloud of the scene using the Kinect Fusion algorithm. Additionally a voxelized occupancy map of the scene is extracted in order to reason about occlusions. We propose two classes of algorithms for symmetry detection: curve based and surface based. Curve based algorithm relies on extracting and matching surface normal edge curves in the pointcloud. A more efficient surface based algorithm works by fitting symmetry axes/planes to the geometry of the smooth surfaces of the scene. In order to segment the objects we introduce a segmentation approach that uses symmetry as a global grouping principle. It extracts points of the scene that are consistent with a given symmetry candidate. To evaluate the performance of our symmetry detection and segmentation algorithms we construct a dataset of cluttered tabletop scenes with ground truth object masks and corresponding symmetries. Finally we demonstrate how our pipeline can be used by a mobile robot to detect and grasp objects in a house scenario.Item Novel Integrated System Architecture for an Autonomous Jumping Micro-Robot(2010) Churaman, Wayne Anthony; Goldsman, Neil; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)As the capability and complexity of robotic platforms continue to evolve from the macro to micro-scale, innovation of such systems is driven by the notion that a robot must be able to sense, think, and act [1]. The traditional architecture of a robotic platform consists of a structural layer upon which, actuators, controls, power, and communication modules are integrated for optimal system performance. The structural layer, for many micro-scale platforms, has commonly been implemented using a silicon die, thus leading to robotic platforms referred to as "walking chips" [2]. In this thesis, the first-ever jumping microrobotic platform is demonstrated using a hybrid integration approach to assemble on-board sensing and power directly onto a polymer chassis. The microrobot detects a change in light intensity and ignites 0.21mg of integrated nanoporous energetic silicon, resulting in 246µJ of kinetic energy and a vertical jump height of 8cm.Item An Architecture for the Autonomous Generation of Preference-Based Trajectories(2006-05-04) Lennon, Jamie; Atkins, Ella M.; Aerospace Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Numerous techniques exist to optimize aircraft and spacecraft trajectories over cost functions that include terms such as fuel, time, and separation from obstacles. Relative weighting factors can dramatically alter solution characteristics, and engineers often must manually adjust either cost weights or the trajectory itself to obtain desirable solutions. Further, when humans and robots work together, or when humans task robots, they may express their performance expectations in a "fuzzy" natural language fashion, or else as an uncertain range of more or less acceptable values. This work describes a software architecture which accepts both fuzzy linguistic and hard numeric constraints on trajectory performance and, using a trajectory generator provided by the user, automatically constructs trajectories to meet these specifications as closely as possible. The system respects hard constraints imposed by system dynamics or by the user, and will not let the user's preferences interfere with the system and user needs. The architecture's evaluation agent translates these requirements into cost functional weights expected to produce the desired motion characteristics. The quality of the resulting full-state trajectory is then evaluated based on a set of computed trajectory features compared to the specified constraints. If constraints are not met, the cost functional weights are adjusted according to precomputed heuristic equations. Heuristics are not generated in an ad hoc fashion, but are instead the result of a systematic testing of the simulated system under a range of simple conditions. The system is tested in a 2DOF linear and a 6DOF nonlinear domain with a variety of constraints and in the presence of obstacles. Results show that the system consistently meets all hard numeric constraints placed on the trajectory. Desired characteristics are often attainable or else, in those cases where they are discounted in favor of the hard constraints, failed by small margins. Results are discussed as a function of obstacles and of constraints.Item ON-ORBIT SPACE SHUTTLE INSPECTION SYSTEM UTILIZING AN EXTENDABLE BOOM(2004-08-12) Michael, Sadie Kathleen; Akin, David; Aerospace Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)An extension to the existing shuttle remote manipulator system (SRMS) on the space shuttle orbiter was developed to provide on-orbit inspection capabilities to survey the thermal protection system (TPS). Following the space shuttle Columbia tragedy, the ability to adequately inspect the orbiter TPS is required for every flight. The inspection system proposed here entails the design of a deployable boom extension to the SRMS that meets the system kinematic and structural requirements. Aiming for a compact and maneuverable system, an extendable boom was designed as an alternative to the boom system planned by NASA. Using requirements derived from of the inspection task, a preliminary design for the boom was developed using a lenticular extendable boom. The inspection system was designed to be compatible with existing orbiter systems while minimizing risk to the shuttle. This project confirmed the feasibility of an on-orbit extendable boom-based inspection system for the orbiter TPS.