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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
391

Variable Precision Tandem Analog-to-Digital Converter (ADC)

Parsons, Colton A 01 June 2014 (has links)
This paper describes an analog-to-digital signal converter which varies its precision as a function of input slew rate (maximum signal rate of change), in order to best follow the input in real time. It uses Flash and Successive Approximation (SAR) conversion techniques in sequence. As part of the design, the concept of "total real-time optimization" is explored, where any delay at all is treated as an error (Error = Delay * Signal Slew Rate). This error metric is proposed for use in digital control systems. The ADC uses a 4-bit Flash converter in tandem with SAR logic that has variable precision (0 to 11 bits). This allows the Tandem ADC to switch from a fast, imprecise converter to a slow, precise converter. The level of precision is determined by the input’s peak rate of change, optimized for minimum real-time error; a secondary goal is to react quickly to input transient spikes. The implementation of the Tandem ADC is described, along with various issues which arise when designing such a converter and how they may be dealt with. These include Flash ADC inaccuracies, rounding issues, and system timing and synchronization. Most of the design is described down to the level of logic gates and related building blocks (e.g. latches and flip-flops), and various logic optimizations are used in the design to reduce calculation delays. The design also avoids active analog circuitry whenever possible – it can be almost entirely implemented with CMOS logic and passive analog components.
392

Viewpoint Optimization for Autonomous Strawberry Harvesting with Deep Reinforcement Learning

Sather, Jonathon J 01 June 2019 (has links)
Autonomous harvesting may provide a viable solution to mounting labor pressures in the United States' strawberry industry. However, due to bottlenecks in machine perception and economic viability, a profitable and commercially adopted strawberry harvesting system remains elusive. In this research, we explore the feasibility of using deep reinforcement learning to overcome these bottlenecks and develop a practical algorithm to address the sub-objective of viewpoint optimization, or the development of a control policy to direct a camera to favorable vantage points for autonomous harvesting. We evaluate the algorithm's performance in a custom, open-source simulated environment and observe affirmative results. Our trained agent yields 8.7 times higher returns than random actions and 8.8 percent faster exploration than our best baseline policy, which uses visual servoing. Visual investigation shows the agent is able to fixate on favorable viewpoints, despite having no explicit means to propagate information through time. Overall, we conclude that deep reinforcement learning is a promising area of research to advance the state of the art in autonomous strawberry harvesting.
393

Qualitative Methods Used to Develop and Characterize the Circulation Control System on Cal Poly's AMELIA

Paciano, Eric N 01 September 2013 (has links)
The circulation control system onboard Cal Poly's Advanced Model for Extreme Lift and Improved Aeroacoustics was a critical component of a highly complex wind tunnel model produced in order to fulfill the requirements of a NASA Research Announcement awarded to David Marshall of the Aerospace Engineering Department. The model was based on a next generation, 150 passenger, regional, cruise efficient, short take-off and landing concept aircraft that achieved high lift through circulation control wings and over-the-wing mounted engines. The wind tunnel model was 10-ft in span, used turbine propulsion simulators, and had a functioning circulation control system driven from tunnel supplied high pressure air. Wind tunnel test results will be compiled into an open-source database intended for validation of predictive tools whose purpose is to advance the state- of-the-art in predictive capabilities for the next generation aircraft configurations. The model's circulation control system produced highly directional, nonuniform flow, and required significant modification in order to generate flow suitable for representation in predictive software. The effort and methods used to generate uniform flow along the circulation control slots is detailed herein. Additionally the results of the system characterization are presented and include a thorough analysis of the slot height, the wing symmetry, and total pressure at the circulation control jet exit. These datasets are intended to aid in making adjustments to the simulation such that it accurately reflects the condition at which the model was tested. Many flow visualization results from the wind tunnel test are also presented to serve as a medium of comparison for results from predictive tools. Oil flow visualization was conducted at many test conditions and provides insight to AMELIA's surface flow in blown and unblown regions. Of particular interest were streamlines at the wingblend, which exhibited some outboard turning, and streamlines on the lower surface where the leading edge stagnation point was investigated. Smoke flow visualization was also utilized to explore the flowfield. The deflection of a individual streamline, under the influence of a changing discharge coefficient as investigated along with the discharge coefficients effect on the extended flowfield. Collectively, the images depict the massive augmentation of the flowfield caused by the presence of the circulation control wing.
394

A Methodology for Verification of Structural Standards for a Seating System by Finite Element Analysis

Dworaczyk Wiltshire, Zachary Kelly 01 June 2019 (has links)
Currently California Polytechnic State University has a patent pending on a new type of seating system designed to increase the functionality of public transportation vehicles. The patent is based on the work completed by a senior project group in 2016, whose design showcased the feasibility of the idea. Further development was completed by a second senior project group, the Adjustable Seating Systems, in 2019. The intent of the Adjustable Seating Systems group was to develop a seating system with the intent of commercialization and implementation in paratransit vehicles with future development into large buses and trains. Seating systems used in public transportation are required to meet strict geometric and structural standards by the federal government under FMVSS 207, 208, 209 and 210 to be comfortable and protect the passenger in a wide variety of situations. Included in these standards are quasi-static and dynamic tests developed to simulate the loading conditions of a crash event. Seating systems must be able to withstand the loading conditions with no obvious signs of failure to ensure the safety of the passengers. The work of this thesis was to simulate the loading conditions outlined by the safety standards on the design developed by the Adjustable Seating Systems group using finite element analysis. The results confirm the seating system meets the required safety standards. The largest stresses induced in the system are between the yield stress and ultimate stress of the material, indicating plastic deformation without failure due to fracture.
395

An Application of Sliding Mode Control to Model-Based Reinforcement Learning

Parisi, Aaron Thomas 01 September 2019 (has links)
The state-of-art model-free reinforcement learning algorithms can generate admissible controls for complicated systems with no prior knowledge of the system dynamics, so long as sufficient (oftentimes millions) of samples are available from the environ- ment. On the other hand, model-based reinforcement learning approaches seek to leverage known optimal or robust control to reinforcement learning tasks by mod- elling the system dynamics and applying well established control algorithms to the system model. Sliding-mode controllers are robust to system disturbance and modelling errors, and have been widely used for high-order nonlinear system control. This thesis studies the application of sliding mode control to model-based reinforcement learning. Computer simulation results demonstrate that sliding-mode control is viable in the setting of reinforcement learning. While the system performance may suffer from problems such as deviations in state estimation, limitations in the capacity of the system model to express the system dynamics, and the need for many samples to converge, this approach still performs comparably to conventional model-free reinforcement learning methods.
396

Control and Sensor Development on a Four-Wheel Pyramidal Reaction Wheel Platform

Logan, Jeffery Jay 01 November 2008 (has links)
The Pyramidal Reaction Wheel Platform, or PRWP, is used to simulate three-axis controls in a torque free space-like environment. The primary purpose of the system will be to evaluate the effects of conjoining sensors to maximize pointing accuracy. Furthermore, the system will incorporate a star tracker in conjunction with a Simulated Star Field (SSF) to better estimate the PRWP orientation. For the sake of this document, however, the goal is to implement a gyroscope, wheel rate sensors, and a make-shift accelerometer—to the PRWP—and integrate a controls algorithm such that three-axis controls are achieved for the PRWP. Three sensors were either better integrated into the system or added altogether. Tachometers were created as a form of hardware circuitry to measure each wheel rate with an accuracy of approximately 2.5 Hz (nearly 15 radians per second). The TAC board circuitry converted each motors encoder output into a speed by use of a frequency to voltage converter. Additionally, although three gyroscopes had been implemented previously, the system was better incorporated into the model such that it was directly transformed via a ROBOSTIX ADC converter before being relayed to SIMULINK via a Bluetooth link. The MEMS gyroscopes allowed for very accurate rate measurements—with a minimum resolution of approximately 0.25 radians per second. Finally, a makeshift accelerometer was incorporated into the system for the purpose of system identification. The accelerometer was incorporated into the system by utilizing a discrete time derivative of the gyroscope readings. However, thankfully a system of two accelerometers can be later utilized to achieve an accuracy of approximately 6 degrees per second-second in the x-axis and 2-3 degrees per second-second in the y- and z-axes. A controls test was performed where the starting location was qo=[0, 0, sqrt(2)/2, sqrt(2)/2] and the target location was qc=[0, 0, 0, 1]. At 80 seconds, the pointing accuracy was 70 degrees around the target and the system was unable to settle during the 80 second trial. The inaccuracy was because of the low frequency of operation of the system—1 Hz. Additionally, the platform reacts slowly to sensor readings and commands. The coupling of these issues causes the pointing accuracy to high. Furthermore, through experimental testing, the maximum wheel rate was found to be approximately 6400 RPM at a duty cycle of 50% at an 8000Hz PWM application due to the Pololu MD01B design limitations: low voltage range (up to 16V), low limit current limiter (5A), and high susceptibility to overheating for large currents.
397

Automatické ovládání osvětlení / Automatic lighting controls

Sůra, Lukáš January 2014 (has links)
This diploma work discusses the design of an automatic lighting for the home. Each access point in the rooms is designed to detect with two laser beams. Laser beams can be extended with PIR sensor and a mechanical switch. An access point can be, for example frames . By this is achieved that when entering the room the light is switched on and the light goes off when leaving. Automatic lighting controls consists of the central panel, the remote sensing and the detection frame. The control panel controls laser beams and lights. Remote control is used to switch on/off the light in the certain room. The detection frame is used to detect a person who enters or leaves the room.
398

Complexity Management to design and produce customerspecific hydraulic controls for mobile applications

Krüßmann, Martin, Tischler, Karin January 2016 (has links)
Complexity management is the key to success for mobile machinery where the variety of customers and applications requires individual solutions. This paper presents the way Bosch Rexroth supports each OEM with hydraulic controls – from specification and conception towards application and production. It gives examples how platforms and processes are optimized according to the customer needs. The demand for flexible, short-term deliveries is met by an agile production with the technologies of Industry 4.0.
399

The Effect of Land-Use Controls on Urban Sprawl

Geshkov, Marin V 19 March 2010 (has links)
Chapter 1 provides a discussion of definitions, criticisms, and measurements of urban sprawl. Land-use controls are surveyed in Chapter 2. In Chapter 3, we present the monocentric urban model, followed by a discussion of extensions of that model to include land-use controls. Chapter 4 is a survey of previous empirical analysis of the monocentric model, while Chapters 5 and 6 present our own empirical work. In general, our empirical results support the theoretical predictions as well as providing support for policies to control sprawl. In particular, the results support the use of maximum lot-size zoning, urban growth boundaries, and density restrictions in the form of minimum building heights, minimum square-footage limits, maximum building permits, and minimum persons per room. The importance of this dissertation lies in the fact that it presents the first empirical analysis of the effects of land-use controls on urban sprawl. For this reason, the findings should be of interest to urban planners in their efforts to control urban sprawl. Because we test theoretical hypotheses found in the urban economics literature, the results should also be of interest to academic economists. Finally, the data on land-use controls gathered for the empirical analysis should be of importance to researchers in urban economics.
400

Strategies for Preventing Financial Fraud in Church Organizations in Ghana

Rockson, Albert 01 January 2019 (has links)
Financial fraud in church organizations is increasing rapidly, which can affect the reputation, donation appeal, future funding, and ability of church organizations to meet their planned organizational goals. The purpose of this multiple case study was to explore strategies for preventing financial fraud in church organizations. The conceptual framework for the study was Cressey’s fraud triangle theory. Twenty participants who utilize strategies for preventing financial fraud in their organizations were purposively selected from 5 church organizations in Ghana. Data were collected through semistructured interviews and analysis of organizational financial policy documents. Interview data were transcribed, coded, and analyzed with Saldaña’s coding guidelines. Data analysis followed recommendations from Yin, including examining the data, grouping data into categories, regrouping data in themes, interpreting the data, and producing empirically based findings that answered the central research question of the study. Three significant themes emerged from the data analysis: effective administration, good stewardship and accountability, and caliber of employees. Implementation of the findings may lead to positive social change by enhancing the donation appeal of church organizations, improving their finances, and enabling them to optimize their operations to benefit individuals, families, communities, and society.

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