Browsing by Subject "control"
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Item Analysis and Design of Smart PV Module(2012-12-10) Mazumdar, PoornimaThis thesis explores the design of a smart photovoltaic (PV) module- a PV module in which PV cells in close proximity are electrically grouped to form a pixel and are connected to dc-dc converter blocks which reside embedded in the back pane of the module. An auto-connected flyback converter topology processing less than full power is used to provide high gain and perform maximum power point tracking (MPPT). These dc-dc converters interface with cascaded H-bridge inverter modules operating on feed forward control for dc-link voltage ripple rejection. By means of feed forward control, a significant reduction in dc link capacitance is achieved by enduring higher dc link ripple voltages. The dc link electrolytic capacitors are replaced with film capacitors thus offering an improvement in the reliability of the smart PV module. The proposed configuration is capable of producing 120V/ 240V AC voltage. The PV module now becomes a smart AC module by virtue of embedded intelligence to selectively actuate the individual dc-dc converters and control the output AC voltages directly, thus becoming a true plug and power energy system. Such a concept is ideal for curved surfaces such as building integrated PV (BIPV) system applications where gradients of insolation and temperature cause not only variations from PV module-to-PV module but from group-to-group of cells within the module itself. A detailed analysis along with simulation and experimental results confirm the feasibility of the proposed system.Item Controller design and implementation for a 6-degree-of-freedom magnetically levitated positioner with high precision(Texas A&M University, 2005-11-01) Yu, HoThis thesis presents the controller design and implementation of a high-precision 6-degree-of-freedom (6-DOF) magnetically levitated (maglev) positioner. This high-precision positioning system consists of a novel concentrated-field magnet matrix and a triangular single-moving part that carries three 3-phase permanent-magnet linear-levitation-motor armatures. Since only a single levitated moving part, namely the platen, generates all required fine and coarse motions, this positioning system is reliable and low-cost. Three planar levitation motors based on the Lorentz-force law not only generate the vertical force to levitate the triangular platen but control the platen??s position and orientation in the horizontal plane. All 6-DOF motions are controlled by magnetic forces only. The platen is regarded a pure mass system, and the spring and damping coefficients are neglected except for the vertical directions. Single-input single-output (SISO) digital lead-lag controllers are designed and implemented on a digital signal processor (DSP). This 6-DOF fully magnetically levitated positioner has a total mass of 5.91 kg and currently exhibits a 120 mm ?? 120 mm travel range. This positioner is highly suitable for semiconductor-manufacturing applications such as wafer steppers. Several experimental motion profiles are presented to demonstrate the maglev stage??s capability of accurately tracking any planar and 3-D paths.Item Design of a Control Strategy for a Fuel Cell/Battery Hybrid Power Supply(2010-01-14) Smith, Richard C.The purpose of this thesis is to design hardware and a control strategy for a fuel cell/battery hybrid power supply. Modern fuel cell/battery hybrid power supplies can have 2 DC/DC converters: one converter for the battery and one for the fuel cell. The hardware for the power supply proposed in this thesis consists of a single DC/DC buck converter at the output terminals of the fuel cell. The battery does not have a DC/DC converter, and it is therefore passive in the system. The use of one single converter is attractive, because it reduces the cost of this power supply. This thesis proposes a method of controlling the fuel cell's DC/DC buck converter to act as a current source instead of a voltage source. This thesis will explain why using the fuel cell's buck converter to act as a current source is most appropriate. The proposed design techniques for the buck converter are also based on stiff systems theory. Combining a fuel cell and a battery in one power supply allows exploitation of the advantages of both devices and undermines their disadvantages. The fuel cell has a slow dynamic response time, and the battery has a fast dynamic response time to fluctuations in a load. A fuel cell has high energy density, and a battery has high power density. And the performance of the hybrid power supply exploits these advantages of the fuel cell and the battery. The controller designed in this thesis allows the fuel cell to operate in its most efficient region: even under dynamic load conditions. The passive battery inherits all load dynamic behavior, and it is therefore used for peaking power delivery, while the fuel cell delivers base or average power. Simulations will be provided using MATLAB/Simulink based models. And the results conclude that one can successfully control a hybrid fuel cell/battery power supply that decouples fluctuations in a load from the fuel cell with extremely limited hardware. The results also show that one can successfully control the fuel cell to operate in its most efficient region.Item Design of active suspension control based upon use of tubular linear motor and quarter-car model(Texas A&M University, 2008-10-10) Allen, Justin AaronThe design, fabrication, and testing of a quarter-car facility coupled with various control algorithms are presented in this thesis. An experimental linear tubular motor, capable of producing a 52-N force, provides control actuation to the model. Controllers consisting of two designs were implemented: a classical controller employing lead and lag networks and a state-space feedback design. Each design was extensively simulated to screen for receptiveness to actuation force limitations and robustness regarding the inexact tire modeling. The goal of each controller was to minimize the acceleration of the sprung mass in the presence of simulated road disturbances, modeled by both sinusoidal and step input excitation wheels. Different reference velocity inputs were applied to the control scheme. Responses to a zero reference were juxtaposed to those that resulted from tracking a reference built off a model that incorporated inertial-frame damping attached to the sprung mass. The outcome of this comparison was that low-frequency disturbances were attenuated better when tracking a zero reference, but the reference relaxation introduced by the inertialframe damping model allowed for better-attenuated high frequency signals. Employing an inertial-frame damping value of 250 N-s/m, the rejected frequency component of the system response synchronous with the disturbance input excitation of 40 rad/s bettered by 33% and 28% when feeding control force from the classical controller and state-space controller, respectively. The experimental analysis conducted on the classical and state-space controllers produced sinusoidal disturbance rejection of at worst 50% within their respective bandwidths. At 25 rad/s, the classical controller was able to remove 80% of the base component synchronous with the disturbance excitation frequency, while the state-space controller filtered out nearly 60%. Analysis on the system's ability to reject step disturbances was greatly confounded with the destructive lateral loading transferred during the excitation process. As a result, subjection to excitation could only occur up to 25 rad/s. At the 20 rad/s response synchronous to the disturbance excitation, the classical and state-space controllers removed 85% and 70% of the disturbance, respectively. Sharp spikes in timebased amplitude were present due to the binding that ensued during testing.Item Development of dynamic models of reactive distillation columns for simulation and determination of control(Texas A&M University, 2005-02-17) Chakrabarty, ArnabDynamic models of a reactive distillation column have been developed and implemented in this work. A model describing the steady state behavior of the system has been built in a first step. The results from this steady state model have been compared to data provided from an industrial collaborator and the reconciled model formed the basis for the development of a dynamic model. Four controlled and four manipulated variables have been determined in a subsequent step and step tests for the manipulated variables were simulated. The data generated by the step responses was used for fitting transfer functions between the manipulated and the controlled variables. RGA analysis was performed to find the optimal pairing for controller design. Feedback controllers of PID type were designed between the paired variables found from RGA and the controllers were implemented on the column model. Both servo and regulatory problems have been considered and tested.Item Estimation algorithm for autonomous aerial refueling using a vision based relative navigation system(Texas A&M University, 2005-11-01) Bowers, Roshawn ElizabethA new impetus to develop autonomous aerial refueling has arisen out of the growing demand to expand the capabilities of unmanned aerial vehicles (UAVs). With autonomous aerial refueling, UAVs can retain the advantages of being small, inexpensive, and expendable, while offering superior range and loiter-time capabilities. VisNav, a vision based sensor, offers the accuracy and reliability needed in order to provide relative navigation information for autonomous probe and drogue aerial refueling for UAVs. This thesis develops a Kalman filter to be used in combination with the VisNav sensor to improve the quality of the relative navigation solution during autonomous probe and drogue refueling. The performance of the Kalman filter is examined in a closed-loop autonomous aerial refueling simulation which includes models of the receiver aircraft, VisNav sensor, Reference Observer-based Tracking Controller (ROTC), and atmospheric turbulence. The Kalman filter is tuned and evaluated for four aerial refueling scenarios which simulate docking behavior in the absence of turbulence, and with light, moderate, and severe turbulence intensity. The docking scenarios demonstrate that, for a sample rate of 100 Hz, the tuning and performance of the filter do not depend on the intensity of the turbulence, and the Kalman filter improves the relative navigation solution from VisNav by as much as 50% during the early stages of the docking maneuver. For the aerial refueling scenarios modeledin this thesis, the addition of the Kalman filter to the VisNav/ROTC structure resulted in a small improvement in the docking accuracy and precision. The Kalman filter did not, however, significantly improve the probability of a successful docking in turbulence for the simulated aerial refueling scenarios.Item How Journalists Sustain Their Autonomy under Ownership Change: A Case Study in Taiwan(2014-08-04) Yeh, Yu-ChuanThe purpose of this research is to explore how changes in the structure of the print media in Taiwan affect journalists? autonomy, a key element of free speech in a democracy. The case of China Times faces the change of managerial practice and the formalization of control after the changes in ownership. This research attempts to examine how these changes influence journalists? autonomy, and further clarify how journalists react to the change of their autonomy. To examine the problem, I interviewed seven journalists who work or have worked in China Times. In addition, I conducted the archival analysis based on interviewees? blogs and the on-line publications of union at China Times. The results show that with change of managerial practice, which decreased journalists? autonomy, there is a formalization of control. There were three different owners at China Times, each representing three work regimes: paternalist hegemony, market hegemony and subsidiary hegemonic despotism. The changes in ownership resulted in the formalization of control resulting in the break between managers and employees. This division resulted in journalists feeling less autonomous than before. Faced with less autonomy, journalists had to choose whether to stay or to exit.Item Impact of Herbicides on Winter Canola (Brassica napus L.) Production and Fatty Acid Composition in South Texas(2013-01-16) Cogdill, Todd JosephCanola is a cool-season, oilseed crop grown throughout Europe, Canada, and the Northern Great Plains region of the United States. The expansion of canola production into new growing regions, such as the Southern Plains region, has resulted in new production challenges. The Southern Plains region cultivates canola as a winter annual compared to a spring annual for the Northern Great Plains and Canada. Given the difference in climate and weed spectrum, region-specific weed management systems need to be developed. Agronomic practices can affect seed oil content, protein content, and fatty acid composition, however the effect of herbicides on these and other characteristic of canola are unknown. Therefore, experiments were conducted in 2010 and 2011 to evaluate a broad spectrum of herbicides for potential use in South Texas canola production with respect to crop injury, effects on canola seed oil content, fatty acid composition, weed control, biomass yield, and forage quality. Visual crop injury at 42 DAE was unacceptable for saflufenacil at both 0.12 and 0.06 kg ai ha-1 and ethalfluralin at 1.05 kg ai ha-1. Trifluralin at 1.12 and 0.56 kg ai ha-1, S-metolachlor at 2.14 and 1.07 kg ai ha-1, pyroxasulfone at 0.24 and 0.12 kg ai ha-1, and pendimethalin at 0.8 kg ai ha-1 had lowest visual injury of all treatments. Fluroxypyr applied EPOST caused severe injury at both 0.21 and 0.11 kg ae ha-1. All other EPOST treatments did not cause any visible injury. Seed oil content was not affected by the herbicides evaluated. Fatty acid composition, specifically stearic acid, oleic acid, linolenic acid, and oleic to linolenic acid ratio, was affected by herbicide treatments. This research found that protoporphyrinogen oxidase (PPG oxidase) inhibitor herbicides, such as carfentrazone-ethyl and saflufenacil, negatively affect canola oil quality. Biomass yield was improved for all herbicide treatments except pendimethalin PRE when compared to the untreated plots. Crude protein content of canola forage was not affected by herbicide treatment. Digestible dry matter appeared to be reduced by treatments that included an EPOST application of sethoxydim. The research shows that pendimethalin and S-metolachlor may be suitable for canola production in South Texas based on low crop injury and effective weed control. Neither pendimethalin nor S-metolachlor is currently labeled for use in canola. The herbicides trifluralin, ethalfluralin, quizalofop P-ethyl, ethametsulfuron-methyl, sethoxydim, glyphosate, clethodim, and clopyralid are currently labeled for use in canola and were confirmed suitable for canola production in South Texas. Carfentrazone-ethyl is currently labeled for use in canola but the effects on oil quality should be considered.Item Modelling and control of a symmetric flapping wing vehicle: an optimal control approach(2009-05-15) Jackson, Justin PatrickThis thesis presents a method for designing a flapping wing stroke for a flapping wing vehicle. A flapping wing vehicle is a vehicle such as a bird or an insect that uses its wings for propulsion instead of a conventional propeller or a jet engine. The intent of this research is to design a wing stroke that the wings can follow which will maintain the vehicle at a desired longitudinal flight path angle and velocity. The cost function is primarily a function of the flight path angle error, velocity error and control rate. The objective maneuver is to achieve a flight condition similar to the trim of a conventional fixed wing aircraft. Gliding configurations of the vehicle are analyzed to better understand flight in minimal energy configurations as well as the modes of the vehicle. A control law is also designed using Lyapunov?s direct method that achieves stable tracking of the wing stroke. Results are presented that demonstrate the ability of the method to design wing strokes that can maintain the vehicle at various flight path angles and velocities. The results of this research show that an optimal control problem can be posed such that the solution of the problem results in a wing stroke that a flapping wing vehicle can use to achieve a desired maneuver. The vehicle velocity is shown to be stable in controlled gliding flight and flapping flight.Item Tuberculosis: Epidemiology, Diagnosis, Treatment, Prevention and Control in the United States and Worldwide(2013-06-03) Calderon, Veronica Elena; Mayhall, C. Glen; Arcari, Christine; de Boer, MelanieTB is one of the most common infectious diseases worldwide. Approximately one-third of the world’s population is infected with TB. In 2011, there are about 9 million new infections and almost 1.4 million deaths. Furthermore, TB is the leading cause of death in HIV-positive individuals. With the global HIV pandemic and the emergence of MDR- and XDR-TB, new diagnostics and treatments are urgently needed for the control and prevention of TB. Ultimately, the coordinated efforts of international and national government agencies, non-government agencies, healthcare professionals, and the public is needed to ensure the implementation and adherence of control strategies that will lead to the eradication of TB. This capstone will focus on the epidemiological and clinical aspects of TB, and the TB prevention and control measures as recommended by national and international organizations. The objectives of this project were accomplished through the direct observation of TB control and prevention measures in the hospital (UTMB) and public health (Galveston County Health District) settings. In addition, an extensive literature review was performed to gain a complete understanding of TB epidemiology, diagnostics, treatments, and prevention and control strategies.Item Use of Drop-nets for Wild Pig Damage and Disease Abatement(2012-11-15) Gaskamp, Joshua AldenNumerous trap designs have been used in efforts to capture wild pigs (Sus scrofa); however, drop-nets have never been examined as a potential tool for wild pig control. I implemented a 2-year study to compare the effectiveness and efficiency of an 18.3 x 18.3 m drop-net and a traditional corral trap for trapping wild pigs. In spring 2010, treatment units were randomly selected and multiple trap sites were identified on 4,047 ha in Love County, Oklahoma. Trap sites were baited with whole corn and monitored with infrared-triggered cameras during pre-construction and capture periods. Unique pigs using trap sites were identified 5 days prior to trap construction and used in mark-recapture calculations to determine trap effectiveness. Three hundred fifty-six pigs were captured in spring of 2010 and 2011. I documented maximum captures of 27 and 15 pigs with drop-nets and corral traps, respectively. I removed 86 and 49% of the unique pigs from treatment units during the course of the study using drop-nets and corral traps, respectively. Catch per unit effort was 1.9 and 2.3 h/pig for drop-nets and corral traps, respectively. Wild pigs did not appear to exhibit trap shyness around drop-nets, which often facilitated the capture of entire sounders in a single drop. Use of drop-nets also eliminated capture of non-target species. During my study, damage by wild pigs was reduced by 90% across the study area, verifying control reduces damage on native rangelands. Population monitoring for pseudorabies virus, brucellosis, and porcine reproductive and respiratory syndrome resulted in exposure rates of 24, 0.4, and 0.4%, respectively. Removal of wild pigs reduced rooting damage and probability of encountering pig borne diseases of importance to livestock and human health. My research confirms drop-nets can be an effective tool for removal of wild pigs.