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- Title
- Optimal Attitude Control Management for a Cubesat.
- Creator
-
Develle, Michael, Xu, Yunjun, Lin, Kuo-Chi, Chew, Phyekeng, University of Central Florida
- Abstract / Description
-
CubeSats have become popular among universities, research organizations, and government agencies due to their low cost, small size, and light weight. Their standardized configurations further reduce the development time and ensure more frequent launch opportunities. Early cubesat missions focused on hardware validation and simple communication missions, with little requirement for pointing accuracy. Most of these used magnetic torque rods or coils for attitude stabilization. However, the...
Show moreCubeSats have become popular among universities, research organizations, and government agencies due to their low cost, small size, and light weight. Their standardized configurations further reduce the development time and ensure more frequent launch opportunities. Early cubesat missions focused on hardware validation and simple communication missions, with little requirement for pointing accuracy. Most of these used magnetic torque rods or coils for attitude stabilization. However, the intrinsic problems associated with magnetictorque systems, such as the lack of three-axis control and low pointing accuracy, make them unsuitable for more advanced missions such as detailed imaging and on-orbit inspection. Three-axis control in a cubesat can be achieved by combining magnetic torque coils with other devices such as thrusters, but the lifetime is limited by the fuel source onboard. To maximize the missionlifetime, a fast attitude control management algorithm that could optimally manage the usage of the magnetic and thruster torques is desirable. Therefore, a recently developed method, the B-Spline-augmented virtual motion camouflage, is presented in this defense to solve the problem. This approach provides results which are very close to those obtained through other popular nonlinear constrained optimal control methods with a significantly reduced computational time.Simulation results are presented to validate the capabilities of the method in this application.
Show less - Date Issued
- 2011
- Identifier
- CFE0004099, ucf:49102
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004099
- Title
- Virtual Motion Camouflage Based Nonlinear Constrained Optimal Trajectory Design Method.
- Creator
-
Basset, Gareth, Xu, Yunjun, Kassab, Alain, Lin, Kuo-Chi, Cho, Hyoung, Qu, Zhihua, University of Central Florida
- Abstract / Description
-
Nonlinear constrained optimal trajectory control is an important and fundamental area of research that continues to advance in numerous fields. Many attempts have been made to present new methods that can solve for optimal trajectories more efficiently or to improve the overall performance of existing techniques. This research presents a recently developed bio-inspired method called the Virtual Motion Camouflage (VMC) method that offers a means of quickly finding, within a defined but varying...
Show moreNonlinear constrained optimal trajectory control is an important and fundamental area of research that continues to advance in numerous fields. Many attempts have been made to present new methods that can solve for optimal trajectories more efficiently or to improve the overall performance of existing techniques. This research presents a recently developed bio-inspired method called the Virtual Motion Camouflage (VMC) method that offers a means of quickly finding, within a defined but varying search space, the optimal trajectory that is equal or close to the optimal solution.The research starts with the polynomial-based VMC method, which works within a search space that is defined by a selected and fixed polynomial type virtual prey motion. Next will be presented a means of improving the solution's optimality by using a sequential based form of VMC, where the search space is adjusted by adjusting the polynomial prey trajectory after a solution is obtained. After the search space is adjusted, an optimization is performed in the new search space to find a solution closer to the global space optimal solution, and further adjustments are made as desired. Finally, a B-spline augmented VMC method is presented, in which a B-spline curve represents the prey motion and will allow the search space to be optimized together with the solution trajectory.It is shown that (1) the polynomial based VMC method will significantly reduce the overall problem dimension, which in practice will significantly reduce the computational cost associated with solving nonlinear constrained optimal trajectory problems; (2) the sequential VMC method will improve the solution optimality by sequentially refining certain parameters, such as the prey motion; and (3) the B-spline augmented VMC method will improve the solution optimality without sacrificing the CPU time much as compared with the polynomial based approach. Several simulation scenarios, including the Breakwell problem, the phantom track problem, the minimum-time mobile robot obstacle avoidance problem, and the Snell's river problem are simulated to demonstrate the capabilities of the various forms of the VMC algorithm. The capabilities of the B-spline augmented VMC method are also shown in a hardware demonstration using a mobile robot obstacle avoidance testbed.
Show less - Date Issued
- 2012
- Identifier
- CFE0004298, ucf:49493
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004298
- Title
- Chaotification as a Means of Broadband Vibration Energy Harvesting with Piezoelectric Materials.
- Creator
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Geiyer, Daniel, Kauffman, Jeffrey L., Das, Tuhin, Moslehy, Faissal, Shivamoggi, Bhimsen, University of Central Florida
- Abstract / Description
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Computing advances and component miniaturization in circuits coupled with stagnating battery technology have fueled growth in the development of high efficiency energy harvesters. Vibration-to-electricity energy harvesting techniques have been investigated extensively for use in sensors embedded in structures or in hard-to-reach locations like turbomachinery, surgical implants, and GPS animal trackers. Piezoelectric materials are commonly used in harvesters as they possess the ability to...
Show moreComputing advances and component miniaturization in circuits coupled with stagnating battery technology have fueled growth in the development of high efficiency energy harvesters. Vibration-to-electricity energy harvesting techniques have been investigated extensively for use in sensors embedded in structures or in hard-to-reach locations like turbomachinery, surgical implants, and GPS animal trackers. Piezoelectric materials are commonly used in harvesters as they possess the ability to convert strain energy directly into electrical energy and can work concurrently as actuators for damping applications. The prototypical harvesting system places two piezoelectric patches on both sides of the location of maximum strain on a cantilever beam. While efficient around resonance, performance drops dramatically should the driving frequency drift away from the beam's fundamental frequency. To date, researchers have worked to improve harvesting capability by modifying material properties, using alternative geometries, creating more efficient harvesting circuits, and inducing nonlinearities. These techniques have partially mitigated the resonance excitation dependence for vibration-based harvesting, but much work remains.In this dissertation, an induced nonlinearity destabilizes a central equilibrium point, resulting in a bistable potential function governing the cantilever beam system. Depending on the environment, multiple stable solutions are possible and can coexist. Typically, researchers neglect chaos and assume that with enough energy in the ambient environment, large displacement trajectories can exist uniquely. When subjected to disturbances a system can fall to coexistent lower energy solutions including aperiodic, chaotic oscillations. Treating chaotic motion as a desirable behavior of the system allows frequency content away from resonance to produce motion about a theoretically infinite number of unstable periodic orbits that can be stabilized through control. The extreme sensitivity to initial conditions exhibited by chaotic systems paired with a pole placement control strategy pioneered by Ott, Grebogi, and Yorke permits small perturbations to an accessible system parameter to alter the system response dramatically. Periodic perturbation of the system trajectories in the vicinity of isolated unstable orbit points can therefore stabilize low-energy chaotic oscillations onto larger trajectory orbits more suitable for energy harvesting.The periodic perturbation-based control method rids the need of a system model. It only requires discrete displacement, velocity, or voltage time series data of the chaotic system driven by harmonic excitation. While the analysis techniques are not fundamentally limited to harmonic excitation, this condition permits the use of standard discrete mapping techniques to isolate periodic orbits of interest. Local linear model fits characterize the orbit and admit the necessary control perturbation calculations from the time series data.This work discusses the feasibility of such a method for vibration energy harvesting, displays stable solutions under various control algorithms, and implements a hybrid bench-top experiment using MATLAB and LabVIEW FPGA. In conclusion, this work discusses the limitations for wide-scale use and addresses areas of further work; both with respect to chaotic energy harvesting and parallel advances required within the field as a whole.
Show less - Date Issued
- 2017
- Identifier
- CFE0006878, ucf:51718
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006878
- Title
- The Diffusion of Digital Dashboards: An Examination of Dashboard Utilization and the Managerial Decision Environment.
- Creator
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Reinking, Jeffrey, Arnold, Vicky, Roberts, Robin, Sutton, Steven, Hampton, Clark, University of Central Florida
- Abstract / Description
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This dissertation consists of three related studies examining the diffusion of digital dashboard technology throughout today's organizations. Dashboards, once reserved for the executive level, are now available to managers at the lower levels of the organization. For these managers, dashboards have become an integral part of their work life to support their decision environment, to provide consistency in measures, to monitor performance, and to communicate information throughout the...
Show moreThis dissertation consists of three related studies examining the diffusion of digital dashboard technology throughout today's organizations. Dashboards, once reserved for the executive level, are now available to managers at the lower levels of the organization. For these managers, dashboards have become an integral part of their work life to support their decision environment, to provide consistency in measures, to monitor performance, and to communicate information throughout the organization. Prior research in the practice literature has shown that dashboards improve managerial performance and organizational performance as well as communicate organizational goals and objectives; however, empirical research has not been conducted in this area to confirm this anecdotal evidence. Using three theories, the phenomenon surrounding the diffusion of dashboards to the lower levels of the organization are examined based on 1) dashboards as a source of interactive management control and strategy alignment, 2) the impact of dashboard quality on strategy alignment, decision environment, and performance, and 3) the impacts on dashboard utilization from the antecedents of information content and task uncertainty and the consequences of user satisfaction and managerial performance. The first study investigates why dashboards have been diffused to the lowers levels of today's organizations. The primary focus of this study is to develop an understanding about the extent of dashboard utilization by decision-makers and the antecedents and consequences of utilization that is responsible for the widespread acceptance of this technology. The data for this study is collected and analyzed through an explanatory cross-sectional field study utilizing a semi-structured questionnaire. Using data from interviews with 27 managers, a framework is developed that indicates strategy alignment and dashboards associated with interactive management control are the primary antecedents that drive dashboard diffusion. The dimensions of dashboard system quality and dashboard information quality mediate the relationship between an interactive dashboard and the extent of dashboard utilization, which leads to higher levels of managerial performance and organizational performance. This study contributes to the dashboard, strategy, and MCS literature by revealing that dashboards are not isolated technologies, rather they play an important role in the execution of strategy at the operational levels of an organization. In addition, dashboards can also function as an interactive management control, which leads to high levels of diffusion of dashboards throughout organizations. Prior strategy literature has examined strategy alignment at the higher levels and this study extends this research stream by investigating strategy alignment at the lower operational levels of the organization.The second study utilizes the IS Success Model to explore the impacts of the antecedents of dashboard system quality and dashboard information quality on the managerial decision environment in addition to the resulting consequences or 'net benefit' of managerial performance and organizational performance. A field survey is used to collect data from 391 dashboard using managers to enable the analysis of the relationships predicted in the theoretical model. The theoretical model is analyzed utilizing PLS. The results show that two dimensions of dashboard quality, system flexibility and information currency, have a positive effect the managerial decision environment. The model indicates support for the consequences of managerial performance and organizational performance resulting from higher levels of decision quality in the managerial decision environment. The model also reveals that when the dashboard measures are strategy aligned, lower levels of dashboard system flexibility are associated with improved managerial decision environment. Therefore, when organizations design their dashboard systems to support strategy alignment, managers should not be afforded high levels of system flexibility to maintain their attention on the key performance indicators selected to align with strategy. This result is a primary contribution to the strategy literature that reveals that strategy aligned dashboards are more effective in environments where the dashboard flexibility is lower. Additionally, study two also extends the strategy literature by examining strategy alignment at the lower levels of the organization, since prior research has concentrated on the higher level strategic outcomes.As dashboards become highly diffused and more managers utilize the technology, the likelihood that dashboard designers cannot provide dashboard content that fits the tasks performed by managers is higher. The third study investigates this fit between dashboard information content and task uncertainty to understand if the fit between the technology and task impacts the extent of dashboard utilization by managers based on the theory of task-technology fit (TTF). TTF predicts higher levels of utilization will increase user satisfaction and managerial performance. Data is collected from 391 managers that utilize dashboards in their weekly work life to analyze the relationships predicted in the theoretical model. PLS is utilized to analyze the theoretical model and indicates weak support of TTF impacting the extent of dashboard utilization. The model supports the hypotheses for the links between the extent of dashboard utilization and user satisfaction and managerial performance. Based on the weak findings from this theoretical model, a second model is developed and analyzed. The second model measures TTF through the mediation of task uncertainty between dashboard information content and the extent of dashboard utilization, while the first model measured TTF through interacting task uncertainty and dashboard information content. The results of the second model show strong support that TTF, as measured through mediation, increases the extent of dashboard utilization. This study contributes to the literature by empirically showing that more extensive levels of dashboard utilization are achieved through the antecedent of TTF, resulting in increased managerial satisfaction and managerial performance.
Show less - Date Issued
- 2013
- Identifier
- CFE0005052, ucf:49969
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005052
- Title
- THE EFFECTIVENESS OF A SPECIFICALLY DESIGNED GREEN ROOF STORMWATER TREATMENT SYSTEM IRRIGATED WITH RECYCLED STORMWATER RUNOFF TO ACHIEVE POLLUTANT REMOVAL AND STORMWATER VOLUME REDUCTION.
- Creator
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Hardin, Michael, Wanielista, Marty, University of Central Florida
- Abstract / Description
-
One of our greatest threats to surface-water quality is polluted stormwater runoff. In this research, investigated is the use of a green roof irrigated with recycled stormwater runoff to remove pollutants from stormwater runoff and reduce the volume of stormwater runoff leaving developed areas. The green roof properties of interest are the filtration and biological processes as well as the roof's ability to hold water and increase evapotranspiration, reducing the volume of stormwater...
Show moreOne of our greatest threats to surface-water quality is polluted stormwater runoff. In this research, investigated is the use of a green roof irrigated with recycled stormwater runoff to remove pollutants from stormwater runoff and reduce the volume of stormwater runoff leaving developed areas. The green roof properties of interest are the filtration and biological processes as well as the roof's ability to hold water and increase evapotranspiration, reducing the volume of stormwater runoff from the source. Because of the above mentioned reasons the experiment consists of a water quality analysis and a water budget done on several experimental chambers modeled after the green roof on the student union building at the University of Central Florida. The green roof chambers are used to study different types of growing media, different irrigation rates, and the addition of plants and how stormwater runoff quality and quantity is affected. There are also control chambers built to model the conventional roof on the student union building. The purpose of the control is to determine the effectiveness of the different media's filtration/adsorption processes and ability to hold water, in addition to identifying the benefits of adding a green roof to both water quality and the water budget. This research showed that a specifically designed green roof stormwater treatment system with a cistern is an effective way to reduce both the volume of and mass of pollutants of stormwater runoff. The year long water budget showed that this system can reduce the volume of stormwater runoff by almost 90%. The green roof model developed within this work showed similar results for the same conditions. Design curves produced by the model have also been presented for several different geographic regions in Florida. The green roof stormwater treatment system presented within this work was effective at reducing the mass of pollutants. However, the concentration of several of the examined pollutants in the effluent of the cistern was higher or equivalent to that of a control roof. Nitrate and ammonia were two that had a lower concentration than the control roof. The use of a pollution control growing media was also examined. The results of this study show that the Black & GoldTM growing media is effective at removing both ortho-phosphorus and total phosphorus. Isotherm analysis was also preformed to quantify the adsorption potential. Despite the promise of the Black & GoldTM growing media to remove phosphorus the plants did not grow as well as in the expanded clay growing media. It is suggested that the pollution control media be used as a layer under the growing media in order to get the benefits of both media.
Show less - Date Issued
- 2006
- Identifier
- CFE0001423, ucf:47058
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0001423
- Title
- THERMAL MANAGEMENT, BEAM CONTROL,AND PACKAGING DESIGNS FOR HIGH POWER DIODE LASER ARRAYS AND PUMP CAVITY DESIGNS FOR DIODE LASER ARRAY PUMPED ROD SHAPED LASERS.
- Creator
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Chung, Te-yuan, Bass, Michael, University of Central Florida
- Abstract / Description
-
Several novel techniques for controlling, managing and utilizing high power diode lasers are described. Low pressure water spray cooling for a high heat flux system is developed and proven to be an ideal cooling method for high power diode laser arrays. In order to enable better thermal and optical performance of diode laser arrays, a new and simple optical element, the beam control prism, is invented. It provides the ability to accomplish beam shaping and beam tilting at the same time....
Show moreSeveral novel techniques for controlling, managing and utilizing high power diode lasers are described. Low pressure water spray cooling for a high heat flux system is developed and proven to be an ideal cooling method for high power diode laser arrays. In order to enable better thermal and optical performance of diode laser arrays, a new and simple optical element, the beam control prism, is invented. It provides the ability to accomplish beam shaping and beam tilting at the same time. Several low thermal resistance diode packaging designs using beam control prisms are proposed, studied and produced. Two pump cavity designs using a diode laser array to uniformly pump rod shape gain media are also investigated.
Show less - Date Issued
- 2004
- Identifier
- CFE0000259, ucf:46222
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000259
- Title
- General Vector Explicit - Impact Time and Angle Control Guidance.
- Creator
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Robinson, Loren, Qu, Zhihua, Behal, Aman, Xu, Yunjun, University of Central Florida
- Abstract / Description
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This thesis proposes and evaluates a new cooperative guidance law called General Vector Explicit -Impact Time and Angle Control Guidance (GENEX-ITACG). The motivation for GENEX-ITACGcame from an explicit trajectory shaping guidance law called General Vector Explicit Guidance(GENEX). GENEX simultaneously achieves design specifications on miss distance and terminalmissile approach angle while also providing a design parameter that adjusts the aggressiveness ofthis approach angle. Encouraged by...
Show moreThis thesis proposes and evaluates a new cooperative guidance law called General Vector Explicit -Impact Time and Angle Control Guidance (GENEX-ITACG). The motivation for GENEX-ITACGcame from an explicit trajectory shaping guidance law called General Vector Explicit Guidance(GENEX). GENEX simultaneously achieves design specifications on miss distance and terminalmissile approach angle while also providing a design parameter that adjusts the aggressiveness ofthis approach angle. Encouraged by the applicability of this user parameter, GENEX-ITACG is anextension that allows a salvo of missiles to cooperatively achieve the same objectives of GENEXagainst a stationary target through the incorporation of a cooperative trajectory shaping guidancelaw called Impact Time and Angle Control Guidance (ITACG).ITACG allows a salvo of missile to simultaneously hit a stationary target at a prescribed impactangle and impact time. This predetermined impact time is what allows each missile involvedin the salvo attack to simultaneously arrived at the target with unique approach angles, whichgreatly increases the probability of success against well defended targets. GENEX-ITACG furtherincreases this probability of kill by allowing each missile to approach the target with a uniqueapproach angle rate through the use of a user design parameter.The incorporation of ITACG into GENEX is accomplished through the use of linear optimal controlby casting the cost function of GENEX into the formulation of ITACG. The feasibility GENEXITACGis demonstrated across three scenarios that demonstrate the ITACG portion of the guidancelaw, the GENEX portion of the guidance law, and finally the entirety of the guidance law. Theresults indicate that GENEX-ITACG is able to successfully guide a salvo of missiles to simultaneouslyhit a stationary target at a predefined terminal impact angle and impact time, while alsoallowing the user to adjust the aggressiveness of approach.
Show less - Date Issued
- 2015
- Identifier
- CFE0005876, ucf:50868
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005876
- Title
- A Triangulation Based Coverage Path Planning For a Mobile Robot With Circular Sensing Range.
- Creator
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An, Vatana, Qu, Zhihua, Haralambous, Michael, Mikhael, Wasfy, University of Central Florida
- Abstract / Description
-
In this dissertation, two coverage path planning (CPP) approaches for a nonholonomic mobile robot are proposed. The first approach is the Local Coverage Path Planning (LCPP) approach which is designed for all sensing ranges. The second approach is the Global Coverage Path Planning (GCPP) approach which is designed for sufficient sensing range that can observe all points of interests in the target region (TR). The LCPP approach constructs CP after finding observer points for all local regions...
Show moreIn this dissertation, two coverage path planning (CPP) approaches for a nonholonomic mobile robot are proposed. The first approach is the Local Coverage Path Planning (LCPP) approach which is designed for all sensing ranges. The second approach is the Global Coverage Path Planning (GCPP) approach which is designed for sufficient sensing range that can observe all points of interests in the target region (TR). The LCPP approach constructs CP after finding observer points for all local regions in the TR. The GCPP approach computes observer points after CP construction. Beginning with the sample TR, the LCPP approach requires 8 algorithms to find a smooth CP and sufficient number of observers for complete coverage. The Global Coverage Path Planning approach requires 17 algorithms to find the smooth CP with sufficient number of observers for completed coverage. The worst case running time for both approaches are quadratic which is consider to be very fast as compared to previous works reported in the literature. The main technical contributions of both approaches are to provide a holistic solution that segments any TR, uses triangulation to determine the line of sights and observation points, and then compute the smooth and collision-free CP. Both approaches provide localization, speed control, curvature control, CP length control, and smooth CP control. The first approach has applications in automate vacuum cleaning, search and rescue mission, spray painting, and etc. The second approach is best used in military and space applications as it requires infinite sensing range which only resource rich organizations can afford. At the very least, the second approach provides simulation opportunity and upper bound cost estimate for CPP. Both approaches will lead to a search strategy that provides the shortest CP with the minimum number of observer and with the shortest running time for any sensing range.
Show less - Date Issued
- 2017
- Identifier
- CFE0006853, ucf:51745
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006853
- Title
- INTEGRATION OF COMMUNICATION CONSTRAINTS INTO PHYSIOCOMIMETICSWARMS VIA PLACEMENT OF LOCATION BASED VIRTUAL PARTICLES.
- Creator
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Haley, Joshua, Wiegand, R. Paul, University of Central Florida
- Abstract / Description
-
This thesis describes a change to the Physiocomimetics Robotic Swarm Control framework that implements communication constraints into swarm behavior. These constraints are necessary to successfully implement theoretical applications in the real world. We describe the basic background of swarm robotics, the Physiocomimetics framework and methods that have attempted to implement communications constraints into robotic swarms. The Framework is changed by the inclusion of different virtual...
Show moreThis thesis describes a change to the Physiocomimetics Robotic Swarm Control framework that implements communication constraints into swarm behavior. These constraints are necessary to successfully implement theoretical applications in the real world. We describe the basic background of swarm robotics, the Physiocomimetics framework and methods that have attempted to implement communications constraints into robotic swarms. The Framework is changed by the inclusion of different virtual particles at a global and local scale that only cause a force on swarm elements if those elements are disconnected from a swarm network. The global particles introduced are a point of known connectivity and a global centroid of the swarm. The local particles introduced are the point of last connectivity and a local centroid. These particles are tested in various simulations and the results are discussed. The global particles are very effective at insuring the communication constraints of the swarm, but the local particles only have partial success. Additionally, some observations are made about swarm formations and the effect of the communication range used during swarm formation.
Show less - Date Issued
- 2011
- Identifier
- CFH0003812, ucf:44747
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH0003812
- Title
- THE EFFECT OF DIFFERENT PRESENTATION FORMATS OF HYPERTEXTANNOTATIONS ON COGNTIVE LOAD, LEARNING AND LEARNER CONTROL.
- Creator
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Yao, Yuanming, Orwig, Gary, University of Central Florida
- Abstract / Description
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This dissertation study was intended to verify whether the positive effects of the roll-over annotation presentation format on reducing cognitive load and enhancing vocabulary and comprehension of 5th-grade children (Morrison, 2004) can be extended to college students' learning from a web-delivered text. In order to answer this research question, relevant constructs, such as cognitive load, learner control and learning, have been examined in this experimental study of 149 undergraduate...
Show moreThis dissertation study was intended to verify whether the positive effects of the roll-over annotation presentation format on reducing cognitive load and enhancing vocabulary and comprehension of 5th-grade children (Morrison, 2004) can be extended to college students' learning from a web-delivered text. In order to answer this research question, relevant constructs, such as cognitive load, learner control and learning, have been examined in this experimental study of 149 undergraduate students in a state university at College of Education.No single effect of annotation presentation format on cognitive load was found, but an interaction effect on cognitive load was revealed between annotation presentation formats and pre-existing knowledge in this study of online education, similar to the interaction effect between annotation presentation formats and learners' reading experience found in traditional textbook learning (Yeung, Jin and Sweller, 1998; Yeung, 1999). Besides, students' computer experience also had a significant impact on their perceived cognitive load. One more key finding from this study was that the embedded annotation presentation format generated the least learner control, significantly different from other annotation presentation formats.
In conclusion, an adaptive approach to the design of annotation presentation formats is recommended, for example, individual differences including learners' familiarity with content should be considered along with different annotation presentation formats so as to reduce learners' overall cognitive load. Additionally, learners' computer experience should be examined when hypertext annotations are used. Finally, choices of annotation presentation formats should be well-conceived to balance cognitive load, learning, and learner control.
Show less - Date Issued
- 2006
- Identifier
- CFE0001201, ucf:46950
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0001201
- Title
- NON-SILICON MICROFABRICATED NANOSTRUCTURED CHEMICAL SENSORS FOR ELECTRIC NOSE APPLICATION.
- Creator
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Gong, Jianwei, Chen, Quanfang, University of Central Florida
- Abstract / Description
-
A systematic investigation has been performed for "Electric Nose", a system that can identify gas samples and detect their concentrations by combining sensor array and data processing technologies. Non-silicon based microfabricatition has been developed for micro-electro-mechanical-system (MEMS) based gas sensors. Novel sensors have been designed, fabricated and tested. Nanocrystalline semiconductor metal oxide (SMO) materials include SnO2, WO3 and In2O3 have been studied for gas sensing...
Show moreA systematic investigation has been performed for "Electric Nose", a system that can identify gas samples and detect their concentrations by combining sensor array and data processing technologies. Non-silicon based microfabricatition has been developed for micro-electro-mechanical-system (MEMS) based gas sensors. Novel sensors have been designed, fabricated and tested. Nanocrystalline semiconductor metal oxide (SMO) materials include SnO2, WO3 and In2O3 have been studied for gas sensing applications. Different doping material such as copper, silver, platinum and indium are studied in order to achieve better selectivity for different targeting toxic gases including hydrogen, carbon monoxide, hydrogen sulfide etc. Fundamental issues like sensitivity, selectivity, stability, temperature influence, humidity influence, thermal characterization, drifting problem etc. of SMO gas sensors have been intensively investigated. A novel approach to improve temperature stability of SMO (including tin oxide) gas sensors by applying a temperature feedback control circuit has been developed. The feedback temperature controller that is compatible with MEMS sensor fabrication has been invented and applied to gas sensor array system. Significant improvement of stability has been achieved compared to SMO gas sensors without temperature compensation under the same ambient conditions. Single walled carbon nanotube (SWNT) has been studied to improve SnO2 gas sensing property in terms of sensitivity, response time and recovery time. Three times of better sensitivity has been achieved experimentally. The feasibility of using TSK Fuzzy neural network algorithm for Electric Nose has been exploited during the research. A training process of using TSK Fuzzy neural network with input/output pairs from individual gas sensor cell has been developed. This will make electric nose smart enough to measure gas concentrations in a gas mixture. The model has been proven valid by gas experimental results conducted.
Show less - Date Issued
- 2005
- Identifier
- CFE0000377, ucf:46328
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000377
- Title
- ANALYSIS AND DESIGN OF A MODULAR SOLAR-FED FAULT-TOLERANT POWER SYSTEM WITH MAXIMUM POWER POINT TRACKING.
- Creator
-
Al-Atrash, Hussam, Batarseh, Issa, University of Central Florida
- Abstract / Description
-
Solar power is becoming ever more popular in a variety of applications. It is particularly attractive because of its abundance, renewability, and environment friendliness. Solar powered spacecraft systems have ever-expanding loads with stringent power regulation specifications. Moreover, they require a light and compact design of their power system. These constraints make the optimization of power harvest from solar arrays a critical task. Florida Power Electronics Center (FPEC) at UCF set to...
Show moreSolar power is becoming ever more popular in a variety of applications. It is particularly attractive because of its abundance, renewability, and environment friendliness. Solar powered spacecraft systems have ever-expanding loads with stringent power regulation specifications. Moreover, they require a light and compact design of their power system. These constraints make the optimization of power harvest from solar arrays a critical task. Florida Power Electronics Center (FPEC) at UCF set to develop a modular fault-tolerant power system architecture for space applications. This architecture provides a number of very attractive features including Maximum Power Point Tracking (MPPT) and uniform power stress distribution across the system. MPPT is a control technique that leads the system to operate its solar sources at the point where they provide maximum power. This point constantly moves following changes in ambient operating conditions. A digital controller is setup to locate it in real time while optimizing other operating parameters. This control scheme can increase the energy yield of the system by up to 45%, and thus significantly reduces the size and weight of the designed system. The modularity of the system makes it easy to prototype and expand. It boosts its reliability and allows on-line reconfiguration and maintenance, thus reducing down-time upon faults. This thesis targets the analysis and optimization of this architecture. A new modeling technique is introduced for MPPT in practical environments, and a novel digital power stress distribution scheme is proposed in order to properly distribute peak and thermal stress and improve reliability. A 2kW four-channel prototype of the system was built and tested. Experimental results confirm the theoretical improvements, and promise great success in the field.
Show less - Date Issued
- 2005
- Identifier
- CFE0000469, ucf:46357
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000469
- Title
- MODELING AND ANALYSIS OF THE EDS MAGLEV SYSTEM WITH THE HALBACH MAGNET ARRAY.
- Creator
-
Ko, Wonsuk, Ham, Chan, University of Central Florida
- Abstract / Description
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The magnetic field analysis based on the wavelet transform is performed. The Halbach array magnetic field analysis has been studied using many methods such as magnetic scalar potential, magnetic vector potential, Fourier analysis and Finite Element Methods. But these analyses cannot identify a transient oscillation at the beginning stage of levitation. The wavelet transform is used for analyzing the transient oscillatory response of an EDS Maglev system. The proposed scheme explains the under...
Show moreThe magnetic field analysis based on the wavelet transform is performed. The Halbach array magnetic field analysis has been studied using many methods such as magnetic scalar potential, magnetic vector potential, Fourier analysis and Finite Element Methods. But these analyses cannot identify a transient oscillation at the beginning stage of levitation. The wavelet transform is used for analyzing the transient oscillatory response of an EDS Maglev system. The proposed scheme explains the under-damped dynamics that results from the cradle's dynamic response to the irregular distribution of the magnetic field. It suggests this EDS Maglev system that responds to a vertical repulsive force could be subject to such instability at the beginning stage of a low levitation height. The proposed method is useful in analyzing instabilities at the beginning stage of levitation height. A controller for the EDS maglev system with the Halbach array magnet is designed for the beginning stage of levitation and after reaching the defined levitation height. To design a controller for the EDS system, two different stages are suggested. Before the object reaches a stable position and after it has reached a stable position. A stable position can be referred to as a nominal height. The former is the stage I and the latter is the stage II. At the stage I, to achieve a nominal height the robust controller is investigated. At the stage II, both translational and rotational motions are considered for the control design. To maintain system stability, damping control as well as LQR control are performed. The proposed method is helpful to understand system dynamics and achieve system stability.
Show less - Date Issued
- 2007
- Identifier
- CFE0001697, ucf:47196
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0001697
- Title
- MODELING AND DIGITAL CONTROL OF HIGH FREQUENCY DC-DC POWER CONVERTERS.
- Creator
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Wen, Yangyang, Batarseh, Issa, University of Central Florida
- Abstract / Description
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The power requirements for leading edge digital integrated circuits have become increasingly demanding. Power converter systems must be faster, more flexible, more precisely controllable and easily monitored. Meanwhile, in addition to control process, the new functions such as power sequencing, communication with other systems, voltage dynamic programming,load line specifications, phase current balance, protection, power status monitoring and system diagnosis are going into today's power...
Show moreThe power requirements for leading edge digital integrated circuits have become increasingly demanding. Power converter systems must be faster, more flexible, more precisely controllable and easily monitored. Meanwhile, in addition to control process, the new functions such as power sequencing, communication with other systems, voltage dynamic programming,load line specifications, phase current balance, protection, power status monitoring and system diagnosis are going into today's power supply systems. Digital controllers, compared withanalog controllers, are in a favorable position to provide basic feedback control as well as those power management functions with lower cost and great flexibility. The dissertation gives an overview of digital controlled power supply systems bycomparing with conventional analog controlled power systems in term of system architecture,modeling methods, and design approaches. In addition, digital power management, as one of the most valuable and "cheap" function, is introduced in Chapter 2. Based on a leading-edge digital controller product, Chapter 3 focuses on digital PID compensator design methodologies, design issues, and optimization and development of digital controlled single-phase point-of-load (POL)dc-dc converter. Nonlinear control is another valuable advantage of digital controllers over analogcontrollers. Based on the modeling of an isolated half-bridge dc-dc converter, a nonlinear control method is proposed in Chapter 4. Nonlinear adaptive PID compensation scheme is implemented based on digital controller Si8250. The variable PID coefficient during transients improves power system's transient response and thus output capacitance can be reduced to save cost. In Chapter 5, another nonlinear compensation algorithm is proposed for asymmetric flybackforward half bridge dc-dc converter to reduce the system loop gain's dependence on the input voltage, and improve the system's dynamic response at high input line. In Chapter 6, a unified pulse width modulation (PWM) scheme is proposed to extend the duty-cycle-shift (DCS) control, where PWM pattern is adaptively generated according to the input voltage level, such that the power converter's voltage stress are reduced and efficiency is improved. With the great flexibility of digital PWM modulation offered by the digital controller Si8250, the proposed control scheme is implemented and verified. Conclusion of the dissertation work and suggestions for future work in related directions are given in final Chapter.
Show less - Date Issued
- 2007
- Identifier
- CFE0001612, ucf:47172
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0001612
- Title
- DESIGN, MODELING, AND CONTROL OF THREE-PORT CONVERTERS FOR SOLAR POWER APPLICATIONS.
- Creator
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Reese, Justin, Batarseh, Issa, University of Central Florida
- Abstract / Description
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This paper describes the results of research into multi-port converter design and control, specifically a pair of three-port topologies based on the half-bridge and full-bridge topologies. These converters are capable of simultaneous and independent regulation of two out of their three ports, while the third port provides the power balance in the system. A dynamic model was developed for each topology to aid in testing and for designing the control loops. The models were then used to design...
Show moreThis paper describes the results of research into multi-port converter design and control, specifically a pair of three-port topologies based on the half-bridge and full-bridge topologies. These converters are capable of simultaneous and independent regulation of two out of their three ports, while the third port provides the power balance in the system. A dynamic model was developed for each topology to aid in testing and for designing the control loops. The models were then used to design the control structures, and the results were tested in Simulink. In addition, a basic outline of a system level architecture to control multiple converters working in parallel is presented. To improve the reliability of this system, output current sharing controls were also developed. Finally, one of the topologies is analyzed in detail in order to obtain a set of design equations that can be used to improve the efficiency, weight, and cost of the converter for a specific application.
Show less - Date Issued
- 2007
- Identifier
- CFE0001921, ucf:47487
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0001921
- Title
- AN IMPROVED THERMOREGULATORY MODEL FOR COOLING GARMENT APPLICATIONS WITH TRANSIENT METABOLIC RATES.
- Creator
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Westin, Johan, Kapat, Jayanta, University of Central Florida
- Abstract / Description
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Current state-of-the-art thermoregulatory models do not predict body temperatures with the accuracies that are required for the development of automatic cooling control in liquid cooling garment (LCG) systems. Automatic cooling control would be beneficial in a variety of space, aviation, military, and industrial environments for optimizing cooling efficiency, for making LCGs as portable and practical as possible, for alleviating the individual from manual cooling control, and for improving...
Show moreCurrent state-of-the-art thermoregulatory models do not predict body temperatures with the accuracies that are required for the development of automatic cooling control in liquid cooling garment (LCG) systems. Automatic cooling control would be beneficial in a variety of space, aviation, military, and industrial environments for optimizing cooling efficiency, for making LCGs as portable and practical as possible, for alleviating the individual from manual cooling control, and for improving thermal comfort and cognitive performance. In this study, we adopt the Fiala thermoregulatory model, which has previously demonstrated state-of-the-art predictive abilities in air environments, for use in LCG environments. We validate the numerical formulation with analytical solutions to the bioheat equation, and find our model to be accurate and stable with a variety of different grid configurations. We then compare the thermoregulatory model's tissue temperature predictions with experimental data where individuals, equipped with an LCG, exercise according to a 700 W rectangular type activity schedule. The root mean square (RMS) deviation between the model response and the mean experimental group response is 0.16°C for the rectal temperature and 0.70°C for the mean skin temperature, which is within state-of-the-art variations. However, with a mean absolute body heat storage error (e_BHS_mean) of 9.7 W·h, the model fails to satisfy the ±6.5 W·h accuracy that is required for the automatic LCG cooling control development. In order to improve model predictions, we modify the blood flow dynamics of the thermoregulatory model. Instead of using step responses to changing requirements, we introduce exponential responses to the muscle blood flow and the vasoconstriction command. We find that such modifications have an insignificant effect on temperature predictions. However, a new vasoconstriction dependency, i.e. the rate of change of hypothalamus temperature weighted by the hypothalamus error signal (DThy·dThy/dt), proves to be an important signal that governs the thermoregulatory response during conditions of simultaneously increasing core and decreasing skin temperatures, which is a common scenario in LCG environments. With the new DThy·dThy/dt dependency in the vasoconstriction command, the e_BHS_mean for the exercise period is reduced by 59% (from 12.9 W·h to 5.2 W·h). Even though the new e_BHS_mean of 5.8 W·h for the total activity schedule is within the target accuracy of ±6.5 W·h, e_BHS fails to stay within the target accuracy during the entire activity schedule. With additional improvements to the central blood pool formulation, the LCG boundary condition, and the agreement between model set-points and actual experimental initial conditions, it seems possible to achieve the strict accuracy that is needed for automatic cooling control development.
Show less - Date Issued
- 2008
- Identifier
- CFE0002460, ucf:47707
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002460
- Title
- AUTONOMOUS ROBOTIC AUTOMATION SYSTEMWITH VISION FEEDBACK.
- Creator
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Rosino, Jeffery, Qu, Zhihua, University of Central Florida
- Abstract / Description
-
In this thesis, a full design, development and application of an autonomous robotic automation system using vision feedback is performed. To realize this system, a cylindrical manipulator configuration is implemented, using a personal computer (PC) based PID controller from National Instruments. Full autonomous control will be achieved via a programmable human machine interface (HMI) developed on a PC using Borland C++ Builder. The vision feedback position control is accomplished using an...
Show moreIn this thesis, a full design, development and application of an autonomous robotic automation system using vision feedback is performed. To realize this system, a cylindrical manipulator configuration is implemented, using a personal computer (PC) based PID controller from National Instruments. Full autonomous control will be achieved via a programmable human machine interface (HMI) developed on a PC using Borland C++ Builder. The vision feedback position control is accomplished using an ordinary "off-the-shelf" web camera. The manuscript is organized as follows; After Chapter 1, an introduction to automation history and its role in the manufacturing industry, Chapter 2 discusses and outlines the development of the robotic kinematics and dynamics of the system. A control strategy is also developed and simulated in this chapter. Chapter 3 discusses color image processing and shows the development of the algorithm used for the vision feedback position control. Chapter 4 outlines the system development, which includes the hardware and software. Chapter 5 concludes with a summary, and improvement section. The process used as a basis for the design and development of this thesis of this thesis topic was constructed from a manual capacitor orientation check test station. A more detailed definition and objective is presented in the introduction.
Show less - Date Issued
- 2004
- Identifier
- CFE0000277, ucf:46220
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000277
- Title
- THE SECOND AMENDMENT IN THE 21ST CENTURY: AN IN-DEPTH EXAMINATION OF FIREARM FREEDOMS AND THEIR RELATIONSHIP WITH PUBLIC SAFETY AND INTERESTS.
- Creator
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Klein, Mathew E, Slaughter, David, University of Central Florida
- Abstract / Description
-
One of the most hotly contested topics in the world today revolves around an object. An object that has caused debate among all members of society both in the United States, and all across the globe. But how could an object, something that on its own does nothing, spur such heated argument? This object is the evolution of invention and the product of fighting amongst each other. This object changes the way people think and how they act. This object can be used for both good and bad. This...
Show moreOne of the most hotly contested topics in the world today revolves around an object. An object that has caused debate among all members of society both in the United States, and all across the globe. But how could an object, something that on its own does nothing, spur such heated argument? This object is the evolution of invention and the product of fighting amongst each other. This object changes the way people think and how they act. This object can be used for both good and bad. This object is a gun. This research project will explore the Second Amendment of the United States Constitution in the 21st century, providing an in depth examination of firearm freedoms and their relationship with public safety and interests. This research is integral to our society, both politically and publically. Firearms are a significant aspect of our country, a longstanding right that many people view as one of the most essential rights of a United States citizen. The research presented will examine vital aspects of the debate regarding firearm rights, and analyze the relationship between firearm freedoms and public safety. This thesis will examine the benefits and detriments regarding firearm freedoms and their relationship with public safety. This thesis will first establish the necessary background information, including general information, legislation, and statistics, in order to analyze the aforementioned relationship. The next step in the analysis is to examine the benefits of firearm freedoms, as well as the problems with having unlimited firearm freedoms. This thesis will also examine other essential areas regarding this debate, including political impact, public opinion, and global comparisons. The thesis will conclude with possible alternatives for legislation regarding firearms, and an analysis of the likely proper path upon which to proceed.
Show less - Date Issued
- 2016
- Identifier
- CFH2000135, ucf:45997
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH2000135
- Title
- NEW OPTIMAL HIGH EFFICIENCY DSP-BASED DIGITAL CONTROLLER DESIGN FOR SUPER HIGH-SPEED PERMANENT MAGNET SYNCHRONOUS MOTOR.
- Creator
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zhao, limei, Wu, Thomas, University of Central Florida
- Abstract / Description
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This dissertation investigates digital controller and switch mode power supply design for super high-speed permanent magnet synchronous motors (PMSM). The PMSMs are a key component for the miniaturic cryocooler that is currently under development at the University of Central Florida with support from NASA Kennedy Space Center and the Florida Solar Energy Center. Advanced motor design methods, control strategies, and rapid progress in semiconductor technology enables production of a highly...
Show moreThis dissertation investigates digital controller and switch mode power supply design for super high-speed permanent magnet synchronous motors (PMSM). The PMSMs are a key component for the miniaturic cryocooler that is currently under development at the University of Central Florida with support from NASA Kennedy Space Center and the Florida Solar Energy Center. Advanced motor design methods, control strategies, and rapid progress in semiconductor technology enables production of a highly efficient digital controller. However, there are still challenges for such super high-speed controller design because of its stability, high-speed, variable speed operation, and required efficiency over a wide speed range. Currently, limited research, and no commercial experimental analysis, is available concerning such motors and their control system design. The stability of a super high-speed PMSM is an important issue particularly for open-loop control, given that PMSM are unstable after exceeding a certain applied frequency. In this dissertation, the stability of super high-speed PMSM is analyzed and some design suggestions are given to maximize this parameter. For ordinary motors, the V/f control curve is a straight line with a boost voltage because the stator resistance is negligible and only has a significant effect around the DC frequency. However, for the proposed super high-speed PMSM the situation is quite different because of the motor's size. The stator resistance is quite large compared with the stator reactive impedance and cannot be neglected when employing constant a V/f control method. The challenge is to design an optimal constant V/f control scheme to raise efficiency with constant V/f control. In the development, test systems and prototype boards were built and experimental results confirmed the effectiveness of the dissertation system.
Show less - Date Issued
- 2005
- Identifier
- CFE0000856, ucf:46651
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000856
- Title
- TECHNOLOGIES TO ENHANCE OPTIMAL GLYCEMIC CONTROL IN YOUNG ADULTS WITH TYPE 1 DIABETES.
- Creator
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Hassett, Shannon L, Gonzalez, Laura, University of Central Florida
- Abstract / Description
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Background People with type 1 diabetes make up approximately two million of the American population. Every day, these two million people struggle to fight this lifelong, sometimes life threatening disease. While type 1 diabetes currently has no cure, there are technologies that can make diabetes management more effective. This study surveyed the type 1 diabetes (T1D) young adult population aged 18-30, to evaluate what technologies and tools are most often associated with achieving optimal...
Show moreBackground People with type 1 diabetes make up approximately two million of the American population. Every day, these two million people struggle to fight this lifelong, sometimes life threatening disease. While type 1 diabetes currently has no cure, there are technologies that can make diabetes management more effective. This study surveyed the type 1 diabetes (T1D) young adult population aged 18-30, to evaluate what technologies and tools are most often associated with achieving optimal glycemic control (OGC). Methodology The instrument is a 35 question, investigator developed survey that is designed to measure how often a participant utilizes the technology identified in each question, with the response choices ranging from 0 (never) to 5 (multiple times daily). In addition, there were some yes/no and fill-in-the-blank questions to identify demographic variables. The technology topics that were explored are 1) mode of insulin therapy, 2) mode of blood glucose monitoring therapy, 3) mode of communication with designated care provider, 4) electronic applications used, 5) demographic variables, and 6) pertinent comorbidities. This information was used to evaluate variables that assist T1Ds in achieving optimal glycemic control. Participants were invited to participate in this study via email using the Students with Diabetes email listserv. The email contained the IRB approved explanation of research letter, which informed participants of the study and the research being conducted. If the student chose to participate, they checked a box that served as an electronic signature, and they continued on to the 35-question survey. All responses to the survey will be kept confidential; as the survey and research did not require any personal identifying information. Data regarding the specific demographics, technologies used for diabetes control, and hemoglobin A1C levels were recorded and analyzed. The results of the survey will be shared with the participants via the same email list-serv by which they were originally recruited. Results There were 59 participants. A total of 21 out of 59 respondents had optimal glycemic control (A1C less than 7.0, per American Diabetes Association guidelines). Eighty eight percent of those with OGC wore their CGMs all the time, while only 66% of those with IGC wore their CGMs all the time. Ninety five percent of those with OGC used their insulin pumps all the time, while 89% of those with IGC did. It is likely that the combination of both CGMs and insulin pumps worn all the time are the most powerful tools to achieving OGC. Students that were employed, enrolled in classes, and still under their parent�s insurance plans had a higher incidence of optimal glycemic control. Discussion It was hypothesized that those with OGC would have a higher incidence of diabetes technology use. This PI found that even though almost all participants had access to the diabetes technology, still only 37% of the participants had optimal glycemic control. There are many components to diabetes care that impact glycemic control that were not explored within this scope of this diabetes technology study. Conclusions It is likely that both CGMs and insulin pumps worn all the time are the most powerful tools to achieving OGC. Students who graduate from college and transition to adulthood are vulnerable as they may encounter added stressors such as employment, and financial responsibility that cause them to deviate from the recommendations for diabetes technology use. Care providers need to be cognizant that young adulthood is a vulnerable time in terms of OGC and optimal diabetes management. Providers need to work with young adults, and encourage them to adhere to the recommended diabetes care regime.
Show less - Date Issued
- 2016
- Identifier
- CFH2000030, ucf:45592
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH2000030
