Theses and Dissertations - Department of Electrical & Computer Engineering (ECE)

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Analysis of a percussive bucket wheel implementation for a robotic planetary excavator
(University of Alabama Libraries, 2015) Headley, Justin Kyle; Ricks, Kenneth G.; University of Alabama Tuscaloosa
Percussive digging methods have shown to reduce excavation forces when applied in a regolith (extraterrestrial) environment. Similarly bucket wheel excavators lend themselves to be favorable for future robotic planetary or Lunar missions due to their simple construction and continuous operation. This thesis analyzes the possibility of combining these technologies and the effects they would have when implemented into a planetary rover. Specific focus is placed on electrical robustness, power systems, and autonomous operation. Contributions include an experimental prototype and a simulated power analysis. Results conclude that a percussive bucket wheel would suffer from increased power consumption while gaining the benefit of increased electrical robustness, improved autonomous operation, and reduced launch mass. Finally, future improvements are discussed and a concluding statement is provided.
Comparing the performance of structured light depth sensors and traditional time-of-flight depth sensors for use in a lunar mining environment
(University of Alabama Libraries, 2014) Hall, Christopher; Ricks, Kenneth G.; University of Alabama Tuscaloosa
Autonomous robots are seen as a necessary component for long term manned missions to the Moon. The robots are necessary to excavate lunar soil for processing for in situ resource utilization. The lunar environment poses several challenges to autonomous robotic navigation and the choice of sensor technologies is more restricted than on Earth. Without GPS and ultrasonic technologies, localization and obstacle detection are often performed using data from a laser-based scanner. Laser scanners have been used in robotics on Earth for many years to provide the distances to surrounding objects. Newer sensors, based upon the use of structured light, can provide range data faster and at a lower cost than traditional laser scanners. The purpose of this project is to evaluate a structured light depth sensor, the Microsoft Kinect for Xbox 360, and a traditional multi-echo laser scanner, the Hokuyo UTM-30LX-EW, to determine if they are suitable for autonomous robotic navigation tasks in a lunar mining application. Experimental results are presented that indicate that IR saturation will prevent the Kinect from producing usable distance data. While IR does not affect the lidar, suspended dust in the environment adversely affect both sensors, differently. In dusty environments, the Kinect performs better at shorter distances while the lidar performs better at longer distances to target. The results indicate that a hybrid system utilizing a Kinect for short range obstacle detection and avoidance combined with a lidar for long range landmark identification and localization could serve as a solution in dusty lunar mining environments protected from excessive IR saturation.
A custom printed circuit board design for microcontroller education
(University of Alabama Libraries, 2011) Taylor, Ryan Andrew; Jackson, Jeff; University of Alabama Tuscaloosa
Much time and effort has been spent attempting to discover the best approach to the problem of microcontroller education. In electrical and computer engineering curricula, much consideration is given to the topic of hardware interfacing. For the potential computer engineer, this is an important concept to master, in view of its significance in the current state of technology. Unfortunately, in many curricula, the student is introduced to digital circuitry and immediately thrust into interfacing, due to the pressures of time in a traditional four-year academic career. Often, the student's understanding of the basics of microcontroller operation and control are not to a satisfactory level before the student is expected to use a processor to control other, more complex, systems. This research attempts to compile a solution to allow a student to be well versed in microcontroller operation while he or she begins to work with additional interfacing requirements. A prototype printed circuit board has been assembled that works in close harmony with the National Instrument ELVIS prototyping system that attempts to alleviate this problem. This prototype daughter card rests on top of the breadboarding area of the ELVIS system and allows the student full access to all of the tools and contacts that would be available without the card. The student is required to make the connections necessary for a fully-functional microcontroller system, as opposed to the method of using a pre-fabricated microcontroller development board. When using a board such as this, the student may not fully understand the individual components and their interconnections. This process of connecting components requires the student to understand the physical interface between the microcontroller and the peripheral device(s). Anticipated results from this research are an increased aptitude in peripheral interfacing and a greater level of success in more complex courses following in the curriculum. By allowing the student to interact with the interfacing process on a lower level, a more complete understanding of microcontroller-based systems and peripheral interfacing is obtained.
Digital pulse width modulation techniques for power converters
(University of Alabama Libraries, 2010) Arunachalam, Thanukamalam; Abu Qahouq, Jaber A.; University of Alabama Tuscaloosa
Recently, digital controls are becoming dominant in almost every power electronic application because of the advantage when compared to analog control. This includes the ability of digital controllers to perform more advanced and sophisticated functions that potentially result in improving power conversion efficiency and/or the dynamic performance of the power converter, the ease of digital control function and loop upgradeability (or revision), and reduced sensitivity to component variations. However, there are also some challenges in digital control such as control loop delays that impact the dynamic performance of the power converters and the additional controller power consumption in some digital control implementations. Digital Pulse Width Modulation (DPWM) is one of the most important parts in digital control systems which control the power switch of the power converters. Modulation technique plays a vital role in causing control delays. There are several implementation schemes of digital pulse width modulation such as counter based DPWM, delay line based DPWM, and hybrid based DPWM. The output voltage is required to have little deviation from the reference voltage and fast settling times under transient events. Therefore, in order to maintain a well regulated output voltage, the control signal must instruct the power converter to either turn on (when there is undershoot in output voltage) or turn off (when there is overshoot in output voltage), as fast as possible. The work presented in this thesis suggests a modulation technique that reduces the turn on delay caused by trailing-edge digital modulation and turn off delay caused by leading-edge digital modulation. Reducing the digital pulse width modulation delay reduces the overshoot and undershoot in the output voltage in power converters with digital closed loop control. The proposed modified digital pulse width modulation scheme is verified using computer simulations and experimental results.
Electrical and computer architecture of an autonomous mars sample return rover prototype
(University of Alabama Libraries, 2016) Leslie, Caleb Thomas; Ricks, Kenneth G.; University of Alabama Tuscaloosa
Space truly is the final frontier. As man looks to explore beyond the confines of our planet, we use the lessons learned from traveling to the Moon and orbiting in the International Space Station, and we set our sights upon Mars. For decades, Martian probes consisting of orbiters, landers, and even robotic rovers have been sent to study Mars. Their discoveries have yielded a wealth of new scientific knowledge regarding the Martian environment and the secrets it holds. Armed with this knowledge, NASA and others have begun preparations to send humans to Mars with the ultimate goal of colonization and permanent human habitation. The ultimate success of any long term manned mission to Mars will require in situ resource utilization techniques and technologies to both support their stay and make a return trip to Earth viable. A sample return mission to Mars will play a pivotal role in developing these necessary technologies to ensure such an endeavor to be a successful one. This thesis describes an electrical and computer architecture for autonomous robotic applications. The architecture is one that is modular, scalable, and adaptable. These traits are achieved by maximizing commonality and reusability within modules that can be added, removed, or reconfigured within the system. This architecture, called the Modular Architecture for Autonomous Robotic Systems (MAARS), was implemented on the University of Alabama’s Collection and Extraction Rover for Extraterrestrial Samples (CERES). The CERES rover competed in the 2016 NASA Sample Return Robot Challenge where robots were tasked with autonomously finding, collecting, and returning samples to the landing site.
Evaluation of ros slam gmapping for extraterrestrial robotic mining
(University of Alabama Libraries, 2018) Koehr, Camden Mark; Ricks, Kenneth G.; University of Alabama Tuscaloosa
Advancements in technology have allowed considerable progress toward putting humans on Mars. The next major hurtle in this endeavor is to resolve the lack of necessary resources available on Mars for maintaining human life. Recent discoveries present the possibility of In-Situ Resource Utilization (ISRU) on Mars. The presence of ice presents the potential for living off the land. Specifically, by mining material from the surface and processing said material for usable water. It is evident an autonomous solution will be necessary to make ISRU possible. The greater the autonomy, the greater the potential. Increased autonomy leads to less human supervision and interaction which will save not only time but also reduce cost. This thesis evaluates the capabilities of Gmapping, a ROS based SLAM algorithm and its applicability to extraterrestrial mining for ISRU. The out-of-the-box implementation of this SLAM node illustrates a strong potential for mission success, however, preliminary results highlight potential issues when operating on unpredictable terrain.
Kinect-based object reconstruction
(University of Alabama Libraries, 2012) Price, Andrew R.; Ricks, Kenneth G.; University of Alabama Tuscaloosa
The Microsoft Kinect has recently grown to prominence as a widely used 3D sensor for both academics and hobbyists alike. This thesis presents a Kinect-oriented framework for reproducing physical objects using open or closed source software, GPU-accelerated hardware, and a 3D printer. Specifics of data capture, surface reconstruction, and manufacture are discussed, along with examples of reproducing mechanical and biological models. Finally, future systematic improvements and additional application areas are discussed.
Sensor stabilization, localization, obstacle detection, and path planning for autonomous rovers: a case study
(University of Alabama Libraries, 2015) Faulkner, Andrew Aubrey; Ricks, Kenneth G.; University of Alabama Tuscaloosa
Autonomous rovers are the next step in exploration of terrestrial planets. Current rovers contain some forms of semi-autonomy, but many functions are still performed by remote human operators. As the distance between Earth and the exploration target increases, communication delays will make teleoperation of rover platforms increasingly difficult. Through the use of autonomous systems, operators may give mission parameters to autonomous exploration rovers and allow onboard systems to carry out the task. In addition, if future exploration requires a repetitive task, such as resource gathering, autonomous rovers represent the best technology for the job. Autonomous rovers face many challenges. Among them are sensor stabilization, localization, obstacle detection, and path planning. This thesis describes an approach for each of the above mentioned challenges. Sensor stabilization was performed using an inertial measurement unit (IMU) and the reverse angle method of stabilization. A 2D Light Detection and Ranging (LIDAR) sensor provided input data for a landmark-based localization algorithm. The same LIDAR unit was actuated to perform 3D scans used in an obstacle detection method based upon ground plane removal, via random sample consensus (RANSAC), and Euclidean Clustering. A modified A* algorithm was used as an occupancy grid-based path planner. The approaches were verified through implementation on the University of Alabama Modular Autonomous Robotic Terrestrial Explorer (MARTE) platform as part of the 2014 NASA Robotic Mining Competition.
A simultaneous localization and mapping implementation using inexpensive hardware
(University of Alabama Libraries, 2010) Aycock, Todd Michael; Ricks, Kenneth G.; University of Alabama Tuscaloosa
Autonomous mobile robots have become more popular over the past few decades, influencing both industry and academia. The strategy of making robots navigate autonomously adds many problems however. Many of these problems are directly related to the robot's ability to localize and autonomously map its environment. A solution to this problem is called simultaneous localization and mapping (SLAM). SLAM is the concept of localizing the robot while simultaneously generating a map of the environment, and then using the map in subsequent localization steps. The success of SLAM lies in a filter algorithm. One of the more common and successful filters is the extended Kalman filter (EKF), and there are many different algorithms that could be used to implement this filter. However, the computational complexity and physical cost of implementing the algorithm place the SLAM solution beyond the scope of many low-cost robotics projects. This thesis analyzes many of these cost issues related to the implementation of SLAM on autonomous robots. First, the types of sensing hardware are discussed, and potential low-cost solutions are suggested. Next, timing aspects of two different methods for data association are examined in order to evaluate tradeoffs between speed and accuracy. Finally, optimizations to the filter's update step involving matrix multiplication are presented. These three changes are presented as a customized EKF SLAM algorithm, called inexpensive hardware SLAM (IH-SLAM), which is applicable to small-scale robotics applications.
A teleoperation and autonomous capable modular robot architecture and implementation
(University of Alabama Libraries, 2015) Sandel, David; Ricks, Kenneth G.; University of Alabama Tuscaloosa
Robots are an integral part of contemporary society with ever increasing use in resource collection, industrial, military, and exploration-based applications. The degree of human intervention necessary for a robot to successfully operate varies from system to system and depends heavily on the application, resources available, and knowledge of the operational environment. A system that can operate either autonomously or under control of a human operator provides the flexibility to adapt to the requirements of a specific mission and to unexpected situations as they are encountered. Similarly, a platform that can be quickly and easily modified is capable of being utilized in a larger number of applications. This thesis describes a generalized computational architecture for a robotic platform that allows the system to be either teleoperated by a remote human operator or completely autonomous. In addition, the architecture is designed specifically to support a modular platform upon which various modules can be attached or removed to provide the functionality needed to complete specific tasks. This architecture was implemented on the University of Alabama Modular Autonomous Robotic Terrestrial Explorer (MARTE) platform as part of the 2014 NASA Robotic Mining Competition to ultimately result in a robot capable of collecting and delivering regolith in a simulated lunar or Martian environment. MARTE was successfully used at the competition and demonstrated the capabilities of the architecture both during testing and in the competition environment.

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Browsing Theses and Dissertations - Department of Electrical & Computer Engineering (ECE) by Author "Anderson, Monica D."

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