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 Title
 Identification of the Inertial Parameters of Manipulator Payloads.
 Creator

Reyes, RyanDavid, Department of Electrical and Computer Engineering
 Abstract/Description

Momentum based motion planning allows small and lightweight manipulators to lift loads that exceed their rated load capacity. One such planner, Sampling Based Model Predictive Optimization (SBMPO) developed at the Center for Intelligent Systems, Control, and Robotics (CISCOR), uses dynamic and kinematic models to produce trajectories that take advantage of momentum. However, the inertial parameters of the payload must be known before the trajectory can be generated. This research utilizes a...
Show moreMomentum based motion planning allows small and lightweight manipulators to lift loads that exceed their rated load capacity. One such planner, Sampling Based Model Predictive Optimization (SBMPO) developed at the Center for Intelligent Systems, Control, and Robotics (CISCOR), uses dynamic and kinematic models to produce trajectories that take advantage of momentum. However, the inertial parameters of the payload must be known before the trajectory can be generated. This research utilizes a method based on least squares techniques for determining the inertial parameters of a manipulator payload. It is applied specifically to a two degree of freedom manipulator. A set of exciting trajectories, i.e., trajectories that sufficiently excite the manipulator dynamics, in task space will be commanded to the system. Inverse kinematics are then used to determine the desired angle, angular velocity, and angular acceleration for the manipulator joints. Using the sampled torque, joint position, velocity, and acceleration data, the least squares technique produces an estimate of the inertial parameters of the payload. This paper focuses on determining which trajectories produce sufficient excitation so that an adequate estimate can be obtained.
Show less  Date Issued
 2014
 Identifier
 FSU_migr_uhm0418
 Format
 Thesis
 Title
 Modeling and Application of Effective Channel Utilization in Wireless Networks.
 Creator

Ng, Jonathan, Yu, Ming (Professor of scientific computing), Zhang, Zhenghao, Harvey, Bruce A., Andrei, Petru, Florida State University, College of Engineering, Department of...
Show moreNg, Jonathan, Yu, Ming (Professor of scientific computing), Zhang, Zhenghao, Harvey, Bruce A., Andrei, Petru, Florida State University, College of Engineering, Department of Electrical and Computer Engineering
Show less  Abstract/Description

As a natural scarcity in wireless networks, radio spectrum becomes a major investment in network deployment. How to improve the channel utilization (CU) of the spectrum is a challenging topic in recent research. In a network environment, the utilization of a channel is measured by the effective CU (ECU), i.e., the effective time for transmission or when the medium being sensed busy over its total operation time. However, existing work does not provide a valid model for ECU. We investigate the...
Show moreAs a natural scarcity in wireless networks, radio spectrum becomes a major investment in network deployment. How to improve the channel utilization (CU) of the spectrum is a challenging topic in recent research. In a network environment, the utilization of a channel is measured by the effective CU (ECU), i.e., the effective time for transmission or when the medium being sensed busy over its total operation time. However, existing work does not provide a valid model for ECU. We investigate the relationship between ECU and the interference from other wireless transmission nodes in a wireless network, as well as from potential malicious attacking interfering sources. By examining the relationship between their transmission time and cotransmission time ratios between two or more interferers, we propose a new model based on the channel occupation time of all nodes in a network. The model finds its mathematical foundation on the set theory. By eliminating the overlapping transmission time intervals instead of simply adding the transmission time of all interferers together, the model can obtain the expected total interference time by properly combining the transmission time of all individual nodes along with the time when two or more nodes transmit simultaneously. Through dividing the interferers into groups according to the strength levels of their received interference power at the interested node, less significant interfering signals can be ignored to reduce the complexity when investigating real scenarios. The model provides an approach to a new detection method for jamming attacks in wireless networks based on a criterion with combined operations of ECU and CU. In the experiments, we find a strong connection between ECU and the received interference power and time. In many cases, strong and frequent interference is accompanied by a declination of ECU. The descending slope though may be steep or flat. When the decrease of ECU is not significant, CU can be observed with a sharp drop instead. Therefore, the two metrics, ECU and CU when properly combined together, demonstrate to be an effective measurement for judging strong interference. In addition, relating to other jamming detection methods in the literature, we build a mathematical connection between the new jamming detection conditions and PDR, the Packet Delivery Ratio, which has been proved effective by previous researchers. Thus, the correlation between the new criteria and PDR guarantees the validity of the former by relating itself to a tested mechanism. Both the ECU model and the jamming detection method are thoroughly verified with OPNET through simulation scenarios. The experiment scenarios are depicted with configuration data and collected statistical results. Especially, the radio jamming detection experiments simulate a dynamic radio channel allocation (RCA) module with a userfriendly graphical interface, through which the interference, the jamming state, and the channel switching process can be monitored. The model can further be applied to other applications such as global performance optimization based on the total ECU of all nodes in a wireless communications environment because ECU relates one node's transmission as the interference for others using the same channel for its global attribute, which is our work planned for the next step. We would also like to compare its effectiveness with other jamming detection methods by exploring more extensive experiment research.
Show less  Date Issued
 2017
 Identifier
 FSU_SUMMER2017_Ng_fsu_0071E_14083
 Format
 Thesis
 Title
 Study of 2D Square RodinAir Photonic Crystal Optical Switch and Design of Fast Planar Laser Shutter.
 Creator

Wang, Huazhong, Zheng, Jim P., Cao, Jim, Andrei, Petru, Li, Hui, Department of Electrical and Computer Engineering, Florida State University
 Abstract/Description

This dissertation is made of two parts. Part I, chapter 1 to chapter 7, is 2D square rodinair photonic crystal optical switch; Part II, chapter 8 to chapter 12, is design of fast laser shutter. Photonic crystal is a kind of materials with periodic structures. Moreover the lattice constant of photonic crystals is on the same scale as the wavelength of electromagnetic waves. One of photonic crystal's specific properties is that only allowable electromagnetic wave states could propagate...
Show moreThis dissertation is made of two parts. Part I, chapter 1 to chapter 7, is 2D square rodinair photonic crystal optical switch; Part II, chapter 8 to chapter 12, is design of fast laser shutter. Photonic crystal is a kind of materials with periodic structures. Moreover the lattice constant of photonic crystals is on the same scale as the wavelength of electromagnetic waves. One of photonic crystal's specific properties is that only allowable electromagnetic wave states could propagate inside. This property presents a new way of controlling the propagation of light inside materials. In this paper, a 2D photonic crystal optical switch is proposed. This is a rodsinair structure device by removing two crosslines of rods from a 2D squarerod photonic crystal. The optical switch feature is achieved by inserting a single rod along the line segment from (0.7, 0.7) to (0.7, 0.7) in coordinate. In fact, this line segment is the diagonal line of the intersection area of two removed crosslines of rods. The position of the inserted single rod determines how much the total source energy propagates into the upper channel. In the case of transverse magnetic Gaussian point source, up to 41.38% of the total source energy goes into the upper channel and is shown by time domain simulation. It is also found that the magnitude of the reflected wave in the left channel varies greatly with spatial position of the single inserted rod. The larger the magnitude of the reflected wave in the left channel, the less energy goes into the upper channel. The time delay between the incident wave and the reflected wave in the left channel is also related to the position of the single inserted rod. In addition, the extremely large time delay between the incident wave and the reflected wave in the left channel shows that the reflected wave encounters many reflections with the walls of the left channel, instead of reflected back from the single inserted rod directly. Simulations also demonstrate that the control effect of this 2D photonic crystal optical switch exists under the cases of Gaussian/continuous wave, point/line source. The advantage of this photonic crystal optical switch presented here is operational simplicity because the change of the position of only one rod is needed to finish the switching function. This operational simplicity is critical in microoptoelectromechanical system (MOEMS) device. Consequently, this 2D photonic crystal optical switch is an attractive design in the study of integrating optical circuit. The goal of Part II is to design a laser shutter to protect eyes from fast laser pulse. The width of targeted laser pulse is 30 ns. It is proposed to apply Pockels cell intensity modulator with longitudinal configuration to block the laser pulse. The Pockels cell material is Deuterated Potassium Dihydrogen Phosphate KD2PO4 (DKDP) because its electrooptic parameter, r63, is highest among popular nonlinear electrooptic materials. The laser shutter is controlled by a semiconductor photon sensor. When photon sensor probes laser pulse, laser shutter starts to block off the laser pulse. The performance of laser shutter is also investigted under variant condictions: laser pulse intensity, semiconductor carrier lifetime, size of Pockels cell.
Show less  Date Issued
 2009
 Identifier
 FSU_migr_etd1259
 Format
 Thesis
 Title
 Formation of RuO₂.Xh₂O Supported Pt Anode Electrode for Direct Methanol Fuel Cells.
 Creator

Tiwari, Vivek, Zheng, Jim P., Li, Hui, Andrei, Petru, Department of Electrical and Computer Engineering, Florida State University
 Abstract/Description

Thesis starts with the introduction and literature review of energy storage and conversion devices, which lay the background for motivation and purpose of this research. The fundamental background behind this work was laid by Zheng et al in 1995 [1], wherein they proposed a new charge storage mechanism of hydrous form of ruthenium oxide (i.e. RuO2.xH2O). They proposed this material as a prospective material for super capacitors and direct methanol fuel cells (DMFCs). Later, Wang et al...
Show moreThesis starts with the introduction and literature review of energy storage and conversion devices, which lay the background for motivation and purpose of this research. The fundamental background behind this work was laid by Zheng et al in 1995 [1], wherein they proposed a new charge storage mechanism of hydrous form of ruthenium oxide (i.e. RuO2.xH2O). They proposed this material as a prospective material for super capacitors and direct methanol fuel cells (DMFCs). Later, Wang et al proposed a monolithic hybrid direct methanol fuel cell, employing a layer of RuO2.xH2O between anode catalyst and membrane [3]. In the same paper, they discussed the probability of RuO2.xH2O supported Pt anode catalyst material. The first section of this work, which is covered in chapter 3, comprises of fundamental research and involves proposing and developing an electrode catalyst material for DMFC. It explains the heuristic approach, leading towards the methodical approach  which finally leads to the development of a catalyst material which, in addition to its remarkable feature of possessing high specific capacitance, could be compared with commercially available materials. The same section also covers the extensive study, testing and electrochemical results of this catalyst material, which included cyclic voltammetery, TEM, XRD and EDAX tests and results. The later segment of this work covers the application of this catalyst material in DMFC. Results from the same show that there is a significant improvement in dynamic response of the DMFC prepared using the proposed catalyst material, when compared to the one prepared using commercial catalyst. Steady state response, on the other hand is slightly degraded. It is discussed as what could be the probable reasons behind the reduced steady state response of the monolithic hybrid DMFC prepared using the new proposed catalyst material. High charge transfer resistance, poor mass transfer, poor dispersion and poor porosity could be few of the reasons behind reduced steady state performance of DMFC. Finally, we conclude that since the improved dynamic response of DMFC is evident using this catalyst material, combined with the fact that it exhibits excellent electrochemical surface area, good methanol oxidation activity, high specific capacitance and small particle size  one could very well extend this research in dealing with the aforementioned short comings. The necessity to extend this research could be estimated from the fact that once commercially realized, DMFCs could easily replace chargeable batteries in automobiles (and other applications). Unlike batteries, which are energy storage devices, DMFCs are energy conversion devices which run directly on fuel (methanol) and don't be to be recharged. Few of the issues which are hindering the commercialization of DMFCs are its low power density (poor energy density and poor dynamic response) and size. The catalyst material developed in this research is easy to synthesize in laboratory and promises to improve the dynamic response of DMFC, eliminating the need of an external battery or super capacitor for instantaneous power demands – hence, reducing its size and weight.
Show less  Date Issued
 2009
 Identifier
 FSU_migr_etd1355
 Format
 Thesis
 Title
 BioInspired Stereoscopic Ranging Imager for Robot Obstacle Avoidance.
 Creator

Stegeman, Thomas, DeBrunner, Victor, Roberts, Rodney, Foo, Simon, Brooks, Geoffery, Department of Electrical and Computer Engineering, Florida State University
 Abstract/Description

This thesis presents and evaluates a bioinspired vision system design to increase the depth field of a stereoscopic ranging imager. Two key attributes of the human vision system are leveraged in this design. The first attribute is image stabilization similar to the inner ear semicircular canals and neck muscles. To accomplish this, an accelerometer and servos were used to stabilize the imager platform. The second human vision attribute used by the design is the ability to change the focal...
Show moreThis thesis presents and evaluates a bioinspired vision system design to increase the depth field of a stereoscopic ranging imager. Two key attributes of the human vision system are leveraged in this design. The first attribute is image stabilization similar to the inner ear semicircular canals and neck muscles. To accomplish this, an accelerometer and servos were used to stabilize the imager platform. The second human vision attribute used by the design is the ability to change the focal vector. This is accomplished by a servo that tilts the imagers in unison and separate servos that enable each imager to pan independently. The performance metrics of depth field size and resolution of this method are compared to a system that has staticallymounted imagers and a fixed video platform.
Show less  Date Issued
 2011
 Identifier
 FSU_migr_etd1562
 Format
 Thesis
 Title
 A 'ProtonFree' Coil for Magnetic Resonance Imaging of Porous Media.
 Creator

Seshadhri, Madhumitha, Foo, Simon Y., Brey, William W., Andrei, Petru, Arora, Rajendra K., Department of Electrical and Computer Engineering, Florida State University
 Abstract/Description

Nuclear Magnetic Resonance Imaging or MRI is a non invasive imaging technique which exploits the inherent magnetic field produced by nuclei of atoms with a nonzero spin. Since hydrogen is the most abundant atom, it forms the basis of NMR imaging techniques. The transparency of many materials to RF irradiation coupled with the access to a large variety of contrast parameters and the nondestructiveness of the method may make it highly useful in materials imaging. In a number of situations...
Show moreNuclear Magnetic Resonance Imaging or MRI is a non invasive imaging technique which exploits the inherent magnetic field produced by nuclei of atoms with a nonzero spin. Since hydrogen is the most abundant atom, it forms the basis of NMR imaging techniques. The transparency of many materials to RF irradiation coupled with the access to a large variety of contrast parameters and the nondestructiveness of the method may make it highly useful in materials imaging. In a number of situations there is a critical need to evaluate the distribution of small amounts of water adsorbed throughout a solid sample. One of these pertains to SprayOn Foam Insulation (SOFI), a thermal insulation material used on liquid hydrogen and oxygen tanks on space shuttles. The basic components of an NMR spectrometer are the magnet, amplifiers, transceiver and imaging coils. In MRI, imaging coils are radiofrequency coils that serve two purposes: the excitation of nuclear spins and the detection of nuclear precession. This thesis aims to successfully design a RF coil for 1H imaging of foam and the water trapped within it. The single turn solenoid is probably the most simple and efficient RF coil design. This type was selected as it has high sensitivity and uniform homogeneity throughout the volume of the coil. The coil has been optimized in terms of dimension, feasibility, strategies for tuning and matching and performance.
Show less  Date Issued
 2011
 Identifier
 FSU_migr_etd1806
 Format
 Thesis
 Title
 Processing, Microstructure, and Critical Current Density of AgSheathed Bi₂Sr₂CaCu₂Oₓ Multifilamentary Round Wire.
 Creator

Shen, Tengming, Hellstrom, Eric, Schwartz, Justin, Larbalestier, David, Andrei, Petru, DeBrunner, Victor, Zheng, Jim P., Department of Electrical and Computer Engineering,...
Show moreShen, Tengming, Hellstrom, Eric, Schwartz, Justin, Larbalestier, David, Andrei, Petru, DeBrunner, Victor, Zheng, Jim P., Department of Electrical and Computer Engineering, Florida State University
Show less  Abstract/Description

Agsheathed multifilamentary Bi2Sr2CaCu2Ox round wire is one of the leading hightemperature superconductors that can generate a magnetic field exceeding the maximum of ~23 T available in present Nbbased lowtemperature superconducting magnet technology. However, the magnet fabrication of powerintube (PIT) AgBi2Sr2CaCu2Ox multifilamentary round wire to develop critical current density Jc > 105 A/cm2 in magnetic fields up to 45 T is difficult, due to complicated material processing, asyet...
Show moreAgsheathed multifilamentary Bi2Sr2CaCu2Ox round wire is one of the leading hightemperature superconductors that can generate a magnetic field exceeding the maximum of ~23 T available in present Nbbased lowtemperature superconducting magnet technology. However, the magnet fabrication of powerintube (PIT) AgBi2Sr2CaCu2Ox multifilamentary round wire to develop critical current density Jc > 105 A/cm2 in magnetic fields up to 45 T is difficult, due to complicated material processing, asyet incompletely understood microstructure, and the problem that Jc is sensitive to hightemperature reactions. This thesis analyzed the critical steps of melt processing PIT Bi2Sr2CaCu2Ox multifilamentary wires, systematically investigating the relationships between processing, microstructure, and conductor & magnet performance. The phase transformation and microstructure development during the melt processing of Bi2Sr2CaCu2Ox wires were thoroughly examined using a brinequench technique that preserves the hightemperature microstructures. On heating to the maximum temperature (~890 °C), Bi2Sr2CaCu2Ox powder melts incongruently, producing a mixture of liquid and secondary solid phases. On subsequent cooling, the liquid reacts with the solid phases and Bi2Sr2CaCu2Ox reforms. The phase reaction to Bi2Sr2CaCu2Ox is often incomplete, leaving remnant nonsuperconducting phases from the melt and the Bi2Sr2CaCu2Ox phase and intergrowth in the superconducting matrix, all of which become current limiting mechanisms (CLMs) and block current flow. Moreover, the gas between precursor powder grains accumulates into large pores upon melting, which divide the filament into segments. The consequence of having large pores in the melt is that the pore regions may become bottlenecks for current flow in fully reacted wires. The high population of CLMs strongly indicates that the fraction of oxide filament area that is effectively used for carrying current is low and increasing the connectivity is the key to improving Jc of Bi2Sr2CaCu2Ox wires. The formation mechanisms of filament bridges that populate melt processed PIT multifilamentary wires were studied. Two types of filament bridges were found. TypeA bridges are singlegrain Bi2Sr2CaCu2Ox that couple multiple filaments. TypeA bridges were suggested to enable an interfilament current flow that may be important for increasing the superconducting crosssection for effectively carrying current. The TypeA bridges form because filaments can bond to adjacent filaments in the melt by Ag preferentially dissolving into liquid at Ag grain boundaries. This discovery of filament bonding and Ag&liquid transport has general application to the design and optimization of multifilamentary Bi2Sr2CaCu2Ox wires. Jc development through the melt processing was examined. Jc of wires doubled during the final cooling stage to room temperature. The fundamental cause of this Jc increase was identified as oxygen overdoping, which reduces the superconducting transition temperature, but increases the flux pinning and most importantly, improves the grain boundary current transport and connectivity. A critical limitation of Bi2Sr2CaCu2Ox for magnet fabrication is that melt processing yields an optimum Jc only within a narrow processing window (both maximum temperature Tmax and soaking time tmax need to be precisely controlled), which makes uniform heat treatment of large coils with large thermal mass difficult. The systematics of this temperature and time dependence were probed by examining the microstructure evolution and Jc of wires prepared at various tmax and Tmax using different melt processing schedules. The final Jc of wires was found to correlate weakly to Tmax or tmax, but it strongly correlates to tmelt, a hidden processing parameter that measures how long conductor spends in the melt state. This strong correlation between Jc and tmelt suggests that the Jc of wires is dominantly controlled by tmelt, not by Tmax or tmax, and careful control of tmelt creates a wider processing window for coils. Raising tmelt above an optimum time caused a decrease in connectivity and Jc. This Jc degradation was found to be associated with lower Bi2Sr2CaCu2Ox nucleation temperature and inhomogeneous Bi2Sr2CaCu2Ox nucleation. The fundamental cause of Jc decreasing with extended tmelt appears to be the Cu loss from the Bi2Sr2CaCu2Ox melt. There are three known ways of Cu loss in the literature; the new finding in the study is that Cu can be lost from wire by a fourth mechanism: Cu diffuses through the Ag from the filament to the surface of the wire where it evaporates as a copper oxide. Cu loss is a pervasive process during melt processing that can explain why nearly all windandreact Bi2Sr2CaCu2Ox coils have Jc values much lower than those of bare, short samples of Bi2Sr2CaCu2Ox wires melt processed at the same time. The study indicates that eliminating Cu loss would potentially raise the Jc of Bi2Sr2CaCu2Ox coils.
Show less  Date Issued
 2010
 Identifier
 FSU_migr_etd1778
 Format
 Thesis
 Title
 Adaptive Subband Array Techninques for Structural Health Monitoring.
 Creator

Medda, Alessio, DeBrunner, Victor E., Chicken, Eric, DeBrunner, Linda, Roberts, Rodney, Department of Electrical and Computer Engineering, Florida State University
 Abstract/Description

Modal based traditional Structural Health Monitoring techniques are limited because of several factors – including a poorlyformed aggregate system model, very low SNR, and unrealistic boundary conditions. Moreover, global techniques often rely on modal damage indicators that are not sensitive to localized damage. In this dissertation, the author proposes a new Damage Detection technique that addresses the spacefrequency localization of damage artifacts in a reference and noreference...
Show moreModal based traditional Structural Health Monitoring techniques are limited because of several factors – including a poorlyformed aggregate system model, very low SNR, and unrealistic boundary conditions. Moreover, global techniques often rely on modal damage indicators that are not sensitive to localized damage. In this dissertation, the author proposes a new Damage Detection technique that addresses the spacefrequency localization of damage artifacts in a reference and noreference framework. For the first situation of referenced damage detection, the author employs the use of compactly supported subband space/frequency and time/frequency analysis using local vibration characteristics, overcoming the signal to noise ration problem with a nearfield adaptive beamformer filter bank. The beamformer filter bank operates on the subband space and provides accurate spatial selectivity and high signal to noise ratio for any given scan direction. Subband analysis is performed using wavelet packets and Daubechies mother wavelets. The system is simulated using a one dimensional Finite Element model of a simply supported beam with simple constraints as a good approximation of a real situation. The local damage is simulated as a reduction of the Young's modulus over a selected group of elements. The Damage Detection is performed using as a damage feature the subband energy for any given scan direction and for each subband center frequency. The energy signature for every location/frequency is compared to the energy signature obtained for the equivalent undamaged structure. The obtained results are validated against the analysis obtained before the beamforming stage, and the algorithm localizes the damage in areas of high probability around the direction of the simulated discontinuity. Moreover, the proposed technique shows a very high accuracy and it is able to detect variations on the structure parameters as low as 1%, with a signal near the noise level. For the second situation of Damage Detection performed without an undamaged reference for the analysis, the author proposes a new statistical method based on the density estimation of the vibration signal. This technique is based in the Gaussian Mixture estimation of the probability density function of the vibration signal, using a greedy EM approach with a new model order selection criteria. This model order is based on global measurement on the cumulative density function as well as on local measurement on density indicators, such as the KullbackLeibler divergence and the estimated Correlation Coefficient. The technique is used to estimate the density of time domain signal and frequency domain signal. As damage indicators, the technique uses the first two principal components from measurements of standard deviation, kurtosis, skewness and entropy on the estimated density. The obtained damage indicators perform better in frequency domain and damage as low as 30% can be detected in a noisy environment.
Show less  Date Issued
 2009
 Identifier
 FSU_migr_etd2507
 Format
 Thesis
 Title
 Microscopic Observations of Quenching and the Underlying Causes of Degradation in YBa₂Cu₃O[subscript 7δ] Coated Conductor.
 Creator

Song, Honghai, DeBrunner, Victor, Schwartz, Justin, Larbalestier, David C., Andrei, Petru, Baldwin, Thomas, Zheng, Jim P., Department of Electrical and Computer Engineering,...
Show moreSong, Honghai, DeBrunner, Victor, Schwartz, Justin, Larbalestier, David C., Andrei, Petru, Baldwin, Thomas, Zheng, Jim P., Department of Electrical and Computer Engineering, Florida State University
Show less  Abstract/Description

Significant advances have been made in the processing and scaleup of YBa2Cu3O7δ (YBCO) coated conductor (CC) and sufficient lengths up to 1 km for YBCO coils are now available. This progress is very promising for a wide range of applications, including high field magnets and electric power systems. One of the remaining issues in the transition from long length conductor to functional coils which needs to be addressed, however, is quench protection, which requires a detailed understanding of...
Show moreSignificant advances have been made in the processing and scaleup of YBa2Cu3O7δ (YBCO) coated conductor (CC) and sufficient lengths up to 1 km for YBCO coils are now available. This progress is very promising for a wide range of applications, including high field magnets and electric power systems. One of the remaining issues in the transition from long length conductor to functional coils which needs to be addressed, however, is quench protection, which requires a detailed understanding of dynamic thermal and nonlinear electromagnetic behaviors during a quench. These behaviors remain poorly understood. Foremost, to have a complete description of macroscopic behaviors of YBCO using traditional voltage and temperature characterization, from high temperature to 4.2 K, and from short, straight sample to long length coil, we carried out measurements on short straight YBCO CC at 4.2 K and conductioncooled YBCO CC pancake coils. We found that, for the same fraction of critical current (I/Ic) at 4.2 K, YBCO CCs have similar minimum quench energy (MQE) and normal zone propagation velocity (NZPV) to that of Agalloy clad Bi2Sr2CaCu2Ox wires and significantly higher MQE and lower NZPV than MgB2 round wires of similar Ic(4.2 K). In the conduction cooled YBCO coils, the longitudinal NZPV (10 – 40 mm/s) is about one order of magnitude larger than the transverse NZPV (1 – 2 mm/s). Moreover, when coil results are compared to those of a short straight sample at 50 K, the longitudinal propagation in the short sample is significantly faster than the longitudinal propagation in the coil. This is due to transverse heat conduction (transverse propagation) which reduces the temperature gradients in the coil but also slows down the longitudinal propagation. Moreover, we simultaneously observe normal zone propagation during a heaterinduced quench using a highspeed, highresolution CCD camera with magnetooptical imaging (MOI) and monitor the voltage and temperature distribution as a function of time. We for the first time present the realtime, dynamic observation of magnetic field redistribution during a thermal disturbance via magnetooptical imaging. The optical images are converted to a twodimensional, timedependent data set that is then analyzed quantitatively. We found that the normal zone propagates nonuniformly in two dimensions within the YBCO layer and that its normal front has a diagonal shape while propagating along the length. Two stages of normal zone propagation are observed. The normal zone propagation velocity at 45 K, I = 50 A (~50% Ic), is determined as 22.7 mm/s using the timedependent optical light intensity data. If time for current redistribution can be reduced, the quench propagation velocity is likely to be increased. Lastly, to understand the failure mechanisms during quenching, YBCO coated conductors were quenched such that the samples were degraded at different levels and the microstructure was locally evaluated in the degraded zones. To evaluate the microstructures, the Cu and Ag layers were etched from both quenched and unquenched control samples for comparison. In the control samples, the YBCO layer is found to have some porosity and a few distributed particles in and above the YBCO surface. Two types of quenched samples were prepared. One quenched sample showed nearly no reduction in endtoend Ic after the quench series and the other was somewhat damaged. In the sample without any reduction in Ic, the Ag cap, however, was found to be partially broken, which is likely due to inhomogeneous heat deposit from the quench heater. In the sample with degradation in superconducting properties, although the degradation zone was eroded by the etchant, the reactants became a signature of the Ag delamination where there is degradation. Quench propagation induced damage is believed to originate from preexisting edge damage in the YBCO CC. The damage propagation starts from the damaged edge was influenced by a thermal gradient along the normal zone. Meanwhile, more damage is likely happen to the other edge of the conductor due to current redistribution starting from both edges. For the first time, we report that quench induced degradation has a dendritic structure, which may come from the thermomagnetic instability in YBCO layer during quenching. The presence of dendritic structure implies that the YBCO has delamination from the Ag/Cu layers. The damage caused by the point defects in the YBCO structure is circular in shape and is not dependent on normal zone propagation. Another interesting feature among the results is that melted Ag particles were found in the degradation zone which implies that the local temperature at defects is very high during quenching.
Show less  Date Issued
 2010
 Identifier
 FSU_migr_etd1628
 Format
 Thesis
 Title
 RealTime Switched Reluctance Machine Emulation via Magnetic Equivalent Circuits.
 Creator

Fleming, Fletcher, Edrington, Chris S., Ordonez, Juan, Foo, Simon, MeyerBaese, Uwe, Weatherspoon, Mark H., Department of Electrical and Computer Engineering, Florida State...
Show moreFleming, Fletcher, Edrington, Chris S., Ordonez, Juan, Foo, Simon, MeyerBaese, Uwe, Weatherspoon, Mark H., Department of Electrical and Computer Engineering, Florida State University
Show less  Abstract/Description

Electrical power systems utilizing electromagnetic devices, namely those of electrical ships, are subject to nonlinearities from regenerative loads, distributed energy storage systems, and onboard loads such as air handling and fluid pumps. Thus, accurate and timely electromagnetic (EM) device models are required in order to fully assess the impact of such transient and/or nonlinear activity. Specifically, by exploiting an often overlooked technique, i.e. the magnetic equivalent circuit (MEC)...
Show moreElectrical power systems utilizing electromagnetic devices, namely those of electrical ships, are subject to nonlinearities from regenerative loads, distributed energy storage systems, and onboard loads such as air handling and fluid pumps. Thus, accurate and timely electromagnetic (EM) device models are required in order to fully assess the impact of such transient and/or nonlinear activity. Specifically, by exploiting an often overlooked technique, i.e. the magnetic equivalent circuit (MEC) modeling method, a solution of adequate granularity for the EM device may be attained while still obeying a faster time commitment when compared to the simulation standard for EM devices, the finite element analysis (FEA) technique. The Hardware in the Loop (HIL) concept synergizes with expedient modeling methods, potentially allowing a wider range of dynamics to be observed in large scale simulations or even tested hardware systems. By scaling down the next generation all electric ships integrated power system (NGIPS) to a power level suitable for an academic laboratory environment, the nonlinear effects of EM devices may be investigated via the HIL concept and the MEC modeling method, given that the runtime is acceptable. This work proposes to develop a novel "real time" MEC (RT MEC) machine model, to ensure the aforementioned runtime. A switched reluctance machine (SRM) is used as a case study device due to both its inherent nonlinearity and it providing an ideal foundation for incorporating various characteristics of the MEC modeling technique. The proposed RT MEC concept will be implemented on a field programmable gate array (FPGA). The advantages of FPGA realization include the inherently parallel nature, a substantially cheaper real time (RT) platform when compared to computationally efficient FEA methods that require dedicated, elaborate resources and application specific hardware. Furthermore, FPGA realization provides a fully customizable solution in terms of numerical methods, time step, HIL interfacing and system expansion. The primary contribution of this work is the RT MEC methodology; more specifically, a high fidelity, real time platform exploited for dynamic SRM modeling, an undoubtedly nonlinear device. RTMEC contributes higher accuracy and lighter computational loads when compared to commercially available modeling techniques adhering to similar time constraints; ultimately, this yields faster simulation times and more accurate HIL simulation or Power Hardware in the Loop (PHIL) emulations. Further exercising the RT MEC concept, a variety of novel applications can arise that are uniquely capable of accentuating the nonlinear intricacies and effects assimilated into machine connected systems. Expanding, RT MEC can provide a state of the art tool useful for assessing overall system impact when subjected to electromechanical transients, control strategies and power electronics; providing pertinence and merit to the principal contribution. Potential applications include investigating the nonlinear effects of loading the NGIPS via a PHIL implementation, emulated via SRM winding pulses or utilizing SRM RT MEC models with large scale wind system simulations to study the impact an SRM motor type has on wind farm design.
Show less  Date Issued
 2014
 Identifier
 FSU_migr_etd8987
 Format
 Thesis
 Title
 A Particle Swarm Optimization Based Maximum Torque Per Ampere Control for a Switched Reluctance Motor.
 Creator

Griffin, Lee, Edrington, Chris S., Andrei, Petru, Moss, Pedro, Department of Electrical and Computer Engineering, Florida State University
 Abstract/Description

The Switched Reluctance Machine (SRM) is known for being one of the oldest electric machine designs. Unfortunately, it is usually assumed that this implies that the machine is outdated. However with the advent of microprocessors, the SRM has become a suitable option for a number of applications because the shortcomings of the machine can be mitigated with control. Compared to other machines, the SRM is more rugged, has a simpler structure, and is less expensive to manufacture. The machine has...
Show moreThe Switched Reluctance Machine (SRM) is known for being one of the oldest electric machine designs. Unfortunately, it is usually assumed that this implies that the machine is outdated. However with the advent of microprocessors, the SRM has become a suitable option for a number of applications because the shortcomings of the machine can be mitigated with control. Compared to other machines, the SRM is more rugged, has a simpler structure, and is less expensive to manufacture. The machine has two control regions: when the speed of the machine is beneath a value called the base speed and when the speed is above the base speed. The base speed is the speed at which the back electromotive force (EMF) of the motor becomes substantial when compared to the source voltage. In both regions, the turnon and turnoff angles of the machine can be used to control the machine. This thesis proposes a method of generating optimal turnon and turnoff angles. The method presented in this thesis is concerned with finding the turnon and turnoff angles needed to generate maximum torque per ampere (MTA). The strategy applies a particle swarm optimization (PSO) technique that searches for the angles that maximize the inductance of the SRM in order to achieve MTA. The inductance function was obtained via Finite Element Analysis (FEA) and experimentally. The method was applied to a 4phase 8/6 SRM. The proposed strategy was found to be effective at both low speeds (beneath the base speed) and high speeds (above the base speed), but MTA could only be asserted for low speeds.
Show less  Date Issued
 2014
 Identifier
 FSU_migr_etd8994
 Format
 Thesis
 Title
 A SamplingBased Model Predictive Control Approachto Motion Planning Forautonomous Underwater Vehicles.
 Creator

Caldwell, Charmane Venda, Collins, Emmanuel G., Roberts, Rodney G., Cartes, David, DeBrunner, Linda S., Department of Electrical and Computer Engineering, Florida State University
 Abstract/Description

In recent years there has been a demand from the commercial, research and military industries to complete tedious and hazardous underwater tasks. This has lead to the use of unmanned vehicles, in particular autonomous underwater vehicles (AUVs). To operate in this environment the vehicle must display kinematically and dynamically feasible trajectories. Kinematic feasibility is important to allow for the limited turn radius of an AUV, while dynamic feasibility can take into consideration...
Show moreIn recent years there has been a demand from the commercial, research and military industries to complete tedious and hazardous underwater tasks. This has lead to the use of unmanned vehicles, in particular autonomous underwater vehicles (AUVs). To operate in this environment the vehicle must display kinematically and dynamically feasible trajectories. Kinematic feasibility is important to allow for the limited turn radius of an AUV, while dynamic feasibility can take into consideration limited acceleration and braking capabilities due to actuator limitations and vehicle inertia. Model Predictive Control (MPC) is a method that has the ability to systematically handle multiinput multioutput (MIMO) control problems subject to constraints. It finds the control input by optimizing a cost function that incorporates a model of the system to predict future outputs subject to the constraints. This makes MPC a candidate method for AUV trajectory generation. However, traditional MPC has difficulties in computing control inputs in real time for processes with fast dynamics. This research applies a novel MPC approach, called SamplingBased Model Predictive Control (SBMPC), to generate kinematically or dynamically feasible system trajectories for AUVs. The algorithm combines the benefits of samplingbased motion planning with MPC while avoiding some of the major pitfalls facing both traditional samplingbased planning algorithms and traditional MPC, namely large computation times and local minimum problems. SBMPC is based on sampling (i.e., discretizing) the input space at each sample period and implementing a goaldirected optimization method (e.g., A?) in place of standard nonlinear programming. SBMPC can avoid local minimum, has only two parameters to tune, and has small computational times that allows it to be used online fast systems. A kinematic model, decoupled dynamic model and full dynamic model are incorporated in SBMPC to generate a kinematic and dynamic feasible 3D path. Simulation results demonstrate the efficacy of SBMPC in guiding an autonomous underwater vehicle from a start position to a goal position in regions populated with various types of obstacles.
Show less  Date Issued
 2011
 Identifier
 FSU_migr_etd4518
 Format
 Thesis
 Title
 Development of a Virtual Grid Interface for Phev Integration Analysis.
 Creator

Hacker, Brian, Edrington, Chris S., Foo, Simon Y., DeBrunner, Linda, Department of Electrical and Computer Engineering, Florida State University
 Abstract/Description

Recent increased popularity in plugin hybrid electric vehicles (PHEVs) has been influenced by their ability to relieve the economic dependence on oil, meanwhile reducing the carbon footprint through the decreased level of harmful emissions. However, PHEV popularity has not come without a cost. PHEVs main source of power are their internal energy storage systems which require energy from the grid through a form of charging station. This need to charge creates a power consumption dilemma on...
Show moreRecent increased popularity in plugin hybrid electric vehicles (PHEVs) has been influenced by their ability to relieve the economic dependence on oil, meanwhile reducing the carbon footprint through the decreased level of harmful emissions. However, PHEV popularity has not come without a cost. PHEVs main source of power are their internal energy storage systems which require energy from the grid through a form of charging station. This need to charge creates a power consumption dilemma on the everstrained power system from population growth and the consumer use of power for current everyday technologies. To study the effects that the charging PHEVs will have on the system, two studies were performed within the scope of this thesis: a system study involving the IEEE 14Bus and a subsystem study that will incorporate the development of a virtual grid interface. The system study populated the IEEE 14Bus system with constant power loads to observe the additional power requirements on the supply generators when integrating PHEVs into the system in an incremental fashion. Also, charging method impacts were conducted by creating uncontrolled and controlled charging profile loadings with the PHEVs. The second study developed a laboratory environment with the intent of emulating a gridconnected charging PHEV, also known as a virtual grid interface. This grid interface will be tested to show proof of concept and then applied to a set of hardware to demonstrate the negative effects of uncontrolled front ends within charging station. Subsequently, the mitigation of the aforementioned negative effects will be illustrated through the employment of an active front end within the charging station. The conclusion provides an understanding for affects from charging PHEVs and the importance in developing controls within the charging stations in order to mitigate undesirable charging impacts. Additionally, the vast range of applications for which the developed virtual grid interface can be used for is discussed, along with some of the limitations and future works of the system.
Show less  Date Issued
 2010
 Identifier
 FSU_migr_etd4341
 Format
 Thesis
 Title
 Experimental and Mathematical Modeling Studies on Current Distribution in High Temperature Superconducting DC Cables.
 Creator

Pothavajhala, Venkata, Edrington, Chris, Graber, Lukas, Andrei, Petru, Department of Electrical and Computer Engineering, Florida State University
 Abstract/Description

High temperature superconducting power cables have the advantage of high current density and low losses over conventional cables. One of the factors that affect the stability and reliability of a superconducting cable is the distribution of current among the tapes of cable. Current distribution was investigated as a function of variations in contact resistance, individual tape critical current (Ic), and index (n)value of individual tapes. It has been shown that besides contact resistances,...
Show moreHigh temperature superconducting power cables have the advantage of high current density and low losses over conventional cables. One of the factors that affect the stability and reliability of a superconducting cable is the distribution of current among the tapes of cable. Current distribution was investigated as a function of variations in contact resistance, individual tape critical current (Ic), and index (n)value of individual tapes. It has been shown that besides contact resistances, variations in other superconducting parameters affect current distribution. Variations in critical current and nvalue become important at low contact resistances. The effects of collective variations in contact resistances, individual tape Ic, and nvalues were studied through simulations using Monte Carlo method. Using an experimentally validated mathematical model, 1000 cables were simulated with normally distributed random values of contact resistances, individual tape Ics, and nvalues. Current distribution in the 1000 simulated cables demonstrated the need for selecting tapes with a narrow distribution in the superconducting parameters to minimize the risk of catastrophic damage to superconducting cables during their operation. It has been demonstrated that there is a potential danger of pushing some tapes closer to their Ic before the current in the cable reaches its design critical current. Mathematical models were also used to study the effect of longitudinal variations in the tape parameters on superconducting cable using Monte Carlo simulations. Each tape of a 30 meter long, 3 kA model cable with 30 tapes was considered to have longitudinal variations in Ic, and n values for every 1 cm section, thus generating particular standard deviation in Ic and n for all 3000 sections of each tape. The results indicate that the apparent critical current and index value of the cable are reduced by a certain percentage depending upon the extent of variation in the characteristics along the length of the tapes.
Show less  Date Issued
 2014
 Identifier
 FSU_migr_etd9071
 Format
 Thesis
 Title
 Spectrum Management in Wireless Networks.
 Creator

Ma, Xiaoguang, Yu, Ming, Duan, Zhenhai, Harvey, Bruce A., Kwan, Bing W., Department of Electrical and Computer Engineering, Florida State University
 Abstract/Description

The limited spectrum provided by the IEEE 802.11 standard is not efficiently utilized in the existing wireless networks. The inefficiency comes from three issues in spectrum management. First, the utilization of the available nonoverlapping channels is not evenly distributed, that is, closely deployed users tend to congregate in the same or interfering channels. This issue incurs an excessive amount of cochannel interference (CCI), causing collisions, and thus decreases network throughput....
Show moreThe limited spectrum provided by the IEEE 802.11 standard is not efficiently utilized in the existing wireless networks. The inefficiency comes from three issues in spectrum management. First, the utilization of the available nonoverlapping channels is not evenly distributed, that is, closely deployed users tend to congregate in the same or interfering channels. This issue incurs an excessive amount of cochannel interference (CCI), causing collisions, and thus decreases network throughput. Second, the dynamic radio channel allocation (RCA) problem is nondeterministic polynomialtime hard (NPhard). The employed heuristic optimization methods can not efficiently find a global optimum, including simple minimization or maximization processes, or certain slow learning processes. Third, the default transmission power of a user reserves unnecessarily large deference areas, in which the collision avoidance (CA) mechanisms prohibit simultaneous transmissions in a given channel. Consequently, the spatial channel reuse is significantly reduced. For the first issue, many RCA algorithms have been proposed. The objective is to minimize CCI among cochannel users while increasing network throughput. Most RCA algorithms use heuristic optimization methods, which have restricted performance limited by one or more of the following aspects. 1)Their evaluation variables may not properly reflect the CCI levels in a network, e.g., the number of cochannel users, the local energy levels, etc.. 2)The dynamic RCA problem is nondeterministic polynomialtime hard (NPhard). The employed heuristic optimization methods can not efficiently find a global optimum, e.g., simple minimization or maximization processes, or certain slow learning processes. 3)The information gathering and processing approaches in these RCA algorithms require prohibitive overheads, such as a common control channel or a central controller. 4)Some unrealistic premises are used, e.g., all users in the same channel can hear each other. 5)Most RCA algorithms are designed for some specific networks. For example, an algorithm designed for organizedorinformation sharing (OIS) networks does not work properly in nonorganizednorinformationSharing (NOIS) networks. For the second issue, it is worth pointing out that the complexity of the existing distributed RCA algorithms has not been studied. For the third issue, various power control algorithms, including courtesy algorithms and opportunistic algorithms, have been introduced to restrain transmission power and thus to minimize deference areas, which in turn to maximize the spatial channel reuse. The courtesy algorithms assign a node with a specific power level according to the link length, which is the distance between the transmitter and the receiver, and the noise and interference power level. These algorithms can be further classified into linear power assignment algorithms and nonlinear power assignment algorithms. The linear power assignment algorithms are so aggressive that they may introduce extra hidden terminals, which cause additional unregulated collisions. However, the nonlinear algorithms are too conservative to maximize the power control benefits. The opportunistic power control algorithms allow conditional violations of the CA mechanisms, i.e., a deferring node can initiate a transmission with a deliberately calculated transmission power so that the ongoing transmission will not be affected. However, the power calculation is based on the constants that are only valid in certain wireless scenarios. Related to this issue, a more difficult problem is how to improve network throughput when the demanded data rate within a certain area exceeds the limit of throughput density, which is defined as the upper limit of the total throughput constrained by the modulation techniques and CA mechanisms in the area. Note that no existing algorithm, neither RCA nor the power control, is able to solve this problem. In this work, we focus our study on the above issues in the spectrum management of wireless networks. Our contributions can be summarized as follows. Firstly, to solve the first issue, we propose an annealing Gibbs sampling (AGS) based distributive RCA (ADRCA) algorithm. The ADRCA algorithm has the following advantages: 1)It uses average effective channel utilization (AECU) to evaluate the channel condition. AECU has a simple relationship with CCI and can accurately reflect the channel congestion conditions. 2)It employs the AGS optimization method, which divides a global optimization problem into a set of distributed local optimization problems. Each of those problems can be solved by simulating a Markov chain. The stationary distribution of the Markov chains is a globally optimized solution. 3)It includes three different cases, namely AGS1, AGS2 and AGS3, which adapt to various types of wireless networks with different optimization objectives. AGS1 is designed to search for a global optimal channel assignment in OIS networks; AGS2 is proposed to work in NOIS networks and pursue maximum individual performance. Added with a prerequisite for RCA procedures, AGS3 focuses on costeffectiveness, reduces channel reallocation attempts, and enhances system stability without significantly downgrading its optimization performance. To further study the costeffectiveness of ADRCA, an upper limit of the computational scale (CS) is found for AGS3 based on an innovative neighboring relationship model in a practical network scenario. Secondly, to solve the second issue, we propose a hybrid approach to study the computational scale (CS), which is defined as the number of channel reallocations until a network reaches a convergent state. First, we propose a simple relationship model to describe the interference relation between an AP and its neighboring APs. Second, for one of the simplest cases in the relationship model, we find an analytical solution for the CS and validate it by simulations. Third, for more general cases, we combine the cases with a similar CS means by using oneway analysis of variance (ANOVA) and find the upper bound of the CS with extensive simulations. The simulation results demonstrate that the hybrid approach is simple and accurate as compared to traditional intuitive comparison methods. Based on the aforementioned hybrid approach, an upper limit of the CS is found for AGS3 in a practical network scenario. Thirdly, to solve the third issue and also raise the limit of throughput density, we propose the channel allocation with powercontrol (CAP) strategy which integrates the ADRCA algorithm and the digitized adaptive power control (DAPC) algorithm, to achieve a synergetic benefit between power control and RCA, which is not considered by the existing RCA algorithms. The synergy comes from the following two aspects: • By reducing the transmission power of each node, DAPC can lower CCI levels, allow more simultaneous transmissions within a certain area, increase spatial reuse, and raise the limit of the throughput density. It also reduces the number of nodes competing for a given channel, and thus significantly decreases the CS of ADRCA. • By striving to assign interfering neighbors to nonoverlapping channels, ADRCA minimizes the number of hidden terminals introduced by the power control processes. The integration causes two potential problems. First, since most RCA algorithms are heuristic, after a system converges, any change in transmission power may trigger unnecessary channel reallocation processes, which then would lead to extra computational costs. Second, channel reallocations can also invalidate current transmission power assignments. The above two problems significantly impair system stability. The CAP strategy overcomes the following two problems as follows: to mitigate the impact of the first problem, a node must estimate the conditions of a new channel and use adaptive transmission power accordingly; for the second problem, the node must calculate the transmission power using linear power control algorithms and round it up to the next larger level in a given set of predetermined power levels. There are several statistical methods applied in our study, including the Markov chain Monte Carlo (MCMC) method, distribution model fitting, paired ttest, and the ANOVA test. They are more accurate and efficient than traditional intuitive comparison methods, making this study an important cornerstone for further research. In this work, we have conducted extensive simulations to demonstrate the effectiveness of the proposed methods. Our simulation results show that AGS1 can achieve a global optimum in most OIS network scenarios. With a 95% confidence level, it achieves 99.75% of the global maximum throughput. AGS2 performs on par with AGS1 in NOIS networks. AGS3 reduces the CS by as much as 98% compared to AGS1 and AGS2. The simulation results also demonstrate that compared with the standard MAC protocol, CAP increases the overall throughput by up to 9.5 times and shortens the endtoend delay by up to 80% for UDP traffic.
Show less  Date Issued
 2010
 Identifier
 FSU_migr_etd2818
 Format
 Thesis
 Title
 Dynamic Resource Management in Wireless Networks.
 Creator

Malvankar, Aniket A. (Aniket Ashok), Yu, Ming, Duan, Zhenhai, Harvey, Bruce, Foo, Simon, Department of Electrical and Computer Engineering, Florida State University
 Abstract/Description

Wireless Communication has been a rapidly growing industry over the past decade. The mobile and portable device market has boomed with the advent of new data, multimedia and voice technologies. The technical advances in mobile and personalized computer fields have accelerated wireless communication into a crucial segment of the communication industry. Introduction of smart phones and hand held devices with internet browsing, email, and multimedia services, has made it essential to add...
Show moreWireless Communication has been a rapidly growing industry over the past decade. The mobile and portable device market has boomed with the advent of new data, multimedia and voice technologies. The technical advances in mobile and personalized computer fields have accelerated wireless communication into a crucial segment of the communication industry. Introduction of smart phones and hand held devices with internet browsing, email, and multimedia services, has made it essential to add features like security, reliability etc over the wireless network. Wireless sensor networks which are a subset of the wireless ad hoc networks have been deployed in various military and defense applications. The popularity of 802.11 technologies have led to large scale manufacturing of 802.11 chipsets and reduced the cost drastically. Thus enabling deployment of large scale wifi networks resembling sensor environment. As wireless communication uses air interface it is challenging to support such advanced QoS (Quality Of Service), features due to external interference. Some of the typical interference encountered is from other electronic devices like microwaves, environmental interference like rain, and from physical structures like buildings. Also it is a known fact that battery technology hasn't kept pace with the electronics industry. Consequently to add portability to these wireless devices it has become essential to cut down on energy sources embedded within these devices. Hence wireless equipment designers have to combat interference with minimal power expenditure. To best utilize the limited resources of these wireless devices and guarantee QoS it is essential to design specialized algorithms spanning across all layers of the network. These algorithms should not only take into account the network parameters but also dynamically adapt to the changes in the network configurations, traffic etc. The complete set of such techniques constitutes what can be described as Dynamic Resource Management In Wireless Networks. The proposed research was aimed to design techniques such as dynamic channel allocation, energy efficient clustering and reliable power aware routing. Clustering is one of the energy efficient architecture in wireless ad hoc networks and more specifically used in sensor network like environment. Clustering is achieved by grouping devices together based on location, traffic generation etc. Clustering not only limits energy spent by devices in communication, but also aids in better utilization of channel by avoiding collisions. Clustering makes sure that devices communicate with their respective cluster head with minimal required power thereby causing very less interference to the devices in the neighboring cluster. It also makes it possible to combine and compress the information at the CH (Cluster Head) before relaying it to the central collection or base station
Show less  Date Issued
 2008
 Identifier
 FSU_migr_etd2762
 Format
 Thesis
 Title
 Luminous Intensity Measurements for LED Related Traffic Signals and Signs.
 Creator

Jiang, Zhaoning, Zheng, Jim P., Tung, Leonard J., Kwan, Bing W., Department of Electrical and Computer Engineering, Florida State University
 Abstract/Description

The proper intensity and chromaticity of traffic signals and signs play a key role in the safe management of the traffic environment. Light Emitting Diode (LED) becomes the most important light emitting device for traffic signals and signs. This thesis describes an experimental measurement system which will measure the luminous intensity of several types of traffic signals and signs, which are made of LEDs. Although chromaticity measurement will be mentioned, the thesis is focused on luminous...
Show moreThe proper intensity and chromaticity of traffic signals and signs play a key role in the safe management of the traffic environment. Light Emitting Diode (LED) becomes the most important light emitting device for traffic signals and signs. This thesis describes an experimental measurement system which will measure the luminous intensity of several types of traffic signals and signs, which are made of LEDs. Although chromaticity measurement will be mentioned, the thesis is focused on luminous intensity measurement. While there are many different types of traffic signals, this thesis will focus on the current measurement procedure of the 12inch traffic signal and the improvement of the procedure. The measurement procedure for other types of LEDrelated signals and future development are also discussed.
Show less  Date Issued
 2004
 Identifier
 FSU_migr_etd3516
 Format
 Thesis
 Title
 Antenna Array Synthesis Using the Cross Entropy Method.
 Creator

Connor, Jeffrey D. (Jeffrey David), Foo, Simon Y., Weatherspoon, Mark H., ChanHilton, Amy, MeyerBaese, Anke, Department of Electrical and Computer Engineering, Florida State...
Show moreConnor, Jeffrey D. (Jeffrey David), Foo, Simon Y., Weatherspoon, Mark H., ChanHilton, Amy, MeyerBaese, Anke, Department of Electrical and Computer Engineering, Florida State University
Show less  Abstract/Description

This dissertation addresses the synthesis of antenna arrays using the CrossEntropy (CE) method, marking the first application of the CE method for solving electromagnetic optimization problems. The CE method is a general stochastic optimization technique for solving both continuous and discrete multiextremal, multiobjective optimization problems. The CE method is an adaptive importance sampling derived from an associated stochastic problem (ASP) for estimating the probability of a rare...
Show moreThis dissertation addresses the synthesis of antenna arrays using the CrossEntropy (CE) method, marking the first application of the CE method for solving electromagnetic optimization problems. The CE method is a general stochastic optimization technique for solving both continuous and discrete multiextremal, multiobjective optimization problems. The CE method is an adaptive importance sampling derived from an associated stochastic problem (ASP) for estimating the probability of a rareevent occurrence. The estimation of this probability is determined using a loglikelihood estimator governed by a parameterized probability distribution. The CE method adaptively estimates the parameters of the probability distribution to produce a random variable solution in the neighborhood of the globally best outcome by minimizing cross entropy. In this work, single and multiobjective optimization using both continuous and combinatorial forms of the CE method are performed to shape the sidelobe power, mainlobe beamwidth, null depths and locations as well as number of active elements of linear array antennas by controlling the spacings and complex array excitations of each element in the array. Specifically, aperiodic arrays are designed through both nonuniform element spacings and thinning active array elements, while phased array antennas are designed by controlling the complex excitation applied to each element of the array. The performance of the CE method is demonstrated by considering different scenarios adopted from literature addressing more popular stochastic optimization techniques such as the Genetic Algorithm (GA) or Particle Swarm Optimization. The primary technical contributions of this dissertation are the simulation results computed using the Cross Entropy method for the different scenarios adopted from literature. Cursory comparisons are made to the results from the literature, but the overall goal of this work is to expose the tendencies of the Cross Entropy method for array synthesis problems and help the reader to make an educated decision when considering the Cross Entropy method for their own problems. Overall, the CE method is a competitive alternative to these more popular techniques, possessing attractive convergence properties, but requiring larger population sizes.
Show less  Date Issued
 2008
 Identifier
 FSU_migr_etd3444
 Format
 Thesis
 Title
 Performance Analysis of a Synchronous Coherent Optical Code Division Multiple Access Networks.
 Creator

Chanila, Mohan, Arora, Krishna, Foo, Simon, MeyerBaese, Anke, Department of Electrical and Computer Engineering, Florida State University
 Abstract/Description

In this master's thesis a performance analysis of Optical CDMA systems is conducted. This is accomplished by simulating and analyzing various CDMA code sequences. These are modified and implemented for all optical networks, in OCDMA systems. These include msequences, Gold codes, Prime sequences and Modified prime code sequences. A simulation model of an OCDMA network for the analysis and performance of these sequences is developed and analyzed. From these studies it has been shown that for a...
Show moreIn this master's thesis a performance analysis of Optical CDMA systems is conducted. This is accomplished by simulating and analyzing various CDMA code sequences. These are modified and implemented for all optical networks, in OCDMA systems. These include msequences, Gold codes, Prime sequences and Modified prime code sequences. A simulation model of an OCDMA network for the analysis and performance of these sequences is developed and analyzed. From these studies it has been shown that for a large number of simultaneous users in the network, Modified Prime codes give the best system performance. Also, for a coherent system, bipolar codes have a significantly better performance. The hardware technology used in the implementation of an OCDMA system is studied. It includes the transmitter structures and receivers with various modifications that can be implemented. The synchronous and asynchronous techniques, coherent and noncoherent with electrical or optical processing are examined for CDMA.
Show less  Date Issued
 2006
 Identifier
 FSU_migr_etd3889
 Format
 Thesis
 Title
 Guiding the Selection of Physical Experiments for the Validation of a Model Designed to Study Grounding in DC Distribution Systems.
 Creator

Infante, Diomar, Edrington, Chris S., Baldwin, Tom, Steurer, Mischa, Foo, Simon Y., Department of Electrical and Computer Engineering, Florida State University
 Abstract/Description

The following work establishes a process for model validation and its application to the study of grounding in DC shipboard power systems. The aim of the thesis is to create a general procedure detailing how to appropriately select physical experiments that validate the simulation model under use. The procedure presented can be applied to any physical system. In the work presented here, the procedure is implemented on a physical setup representational of a shipboard power system. This set up...
Show moreThe following work establishes a process for model validation and its application to the study of grounding in DC shipboard power systems. The aim of the thesis is to create a general procedure detailing how to appropriately select physical experiments that validate the simulation model under use. The procedure presented can be applied to any physical system. In the work presented here, the procedure is implemented on a physical setup representational of a shipboard power system. This set up is used for the study of grounding. Grounding in the context used in this work refers to the intentional physical connection from the power carrying elements in the electrical system to the ship hull. Grounding practices are generally well understood for AC shipboard power system. However, the same cannot be said for MVDC systems. There is a growing interest in medium voltage DC systems to be implemented on shipboard power systems. This new type of distribution systems posse many unanswered questions. One of those questions is in regards to the selection of the grounding scheme. The selection of the grounding scheme for a MVDC system is a question of optimization once the designer has a good understanding of the key parameters found in the system. The key parameters in the systems are those that have a large impact on the system's responses. This work provides the designer with a tool to assess the impact each of those parameters has on the responses of the system. These system responses can be labeled as metrics and are encapsulated under the two main objectives of shipboard power systems grounding: safety and continuity of service. Thus, the aim of this work, to establish a procedure, which regardless of the shipboard power system under study, can deliver a validated simulation model for the designer to optimize. The proposed procedure was applied to a representative physical set up of a shipboard power system. The physical model contains most of the requirements to understand to issues associated with DC shipboard grounding. Certain aspects of DC shipboard power systems have not been implemented in the physical model due to material constraints. However, the physical system still holds enough value to gain insight into what happens in a DC shipboard power system. In addition, the physical model has enough complexity to use as a test case for the application of the procedure proposed. The work presented herein focuses on the selection of physical experiments in order to validate the simulation model in a qualitative fashion. The process is presented and its major components are discussed. It is important to note that the design process yields, as a byproduct, insight into the system under study. In the case presented here, in which the process is used with a focus in system grounding, a good explanation of rail to ground harmonics is obtained. In summary, the contributions of this work are twofold. The thesis provides a layout for obtaining confidence in the models being used for the system under study. In addition, this work establishes the important parameters in regards to grounding in DC shipboard power system based on the simplified model used.
Show less  Date Issued
 2011
 Identifier
 FSU_migr_etd3875
 Format
 Thesis
 Title
 Kernel Methods and Component Analysis for Pattern Recognition.
 Creator

Isaacs, Jason C., Foo, Simon Y., MeyerBaese, Anke, Liu, Xiuwen, ChanHilton, Amy, Department of Electrical and Computer Engineering, Florida State University
 Abstract/Description

Kernel methods, as alternatives to component analysis, are mathematical tools that provide a higher dimensional representation, for feature recognition and image analysis problems. In machine learning, the kernel trick is a method for converting a linear classification learning algorithm into nonlinear one, by mapping the original observations into a higherdimensional space so that the use of a linear classifier in the new space is equivalent to a nonlinear classifier in the original space...
Show moreKernel methods, as alternatives to component analysis, are mathematical tools that provide a higher dimensional representation, for feature recognition and image analysis problems. In machine learning, the kernel trick is a method for converting a linear classification learning algorithm into nonlinear one, by mapping the original observations into a higherdimensional space so that the use of a linear classifier in the new space is equivalent to a nonlinear classifier in the original space. In this dissertation we present the performance results of several continuous distribution function kernels, lattice oscillation model kernels, Kelvin function kernels, and orthogonal polynomial kernels on select benchmarking databases. In addition, we develop methods to analyze the use of these kernels for projection analysis applications; principal component analysis, independent component analysis, and optimal projection analysis. We compare the performance results with known kernel methods on several benchmarks. Empirical results show that several of these kernels outperform other previously suggested kernels on these data sets. Additionally, we develop a genetic algorithmbased kernel optimal projection analysis method which, through extensive testing, demonstrates a ten percent average improvement in performance on all data sets over the kernel principal component analysis projection. We also compare our kernels methods for kernel eigenface representations with previous techniques. Finally, we analyze the benchmark databases used here to determine whether we can aid in the selection of a particular kernel that would perform optimally based on the statistical characteristics of each database.
Show less  Date Issued
 2007
 Identifier
 FSU_migr_etd3861
 Format
 Thesis
 Title
 Efficient Hardware Implementation Techniques for Digital Filters.
 Creator

Guo, Rui, DeBrunner, Linda, Harvey, Bruce, DeBrunner, Victor, Roberts, Rodney, Department of Electrical and Computer Engineering, Florida State University
 Abstract/Description

This dissertation addresses the development of efficient digital filter implementation techniques. Measures for area, latency, and throughput are used to quantify the benefits of the proposed implementation schemes, as well as consideration of the digital signal processing algorithm performance. Multipleconstant multiplication (MCM) is a popular approach for implemented fixed coefficient finite impulse response (FIR) filters. We propose two methods for truncating addition results in an MCM...
Show moreThis dissertation addresses the development of efficient digital filter implementation techniques. Measures for area, latency, and throughput are used to quantify the benefits of the proposed implementation schemes, as well as consideration of the digital signal processing algorithm performance. Multipleconstant multiplication (MCM) is a popular approach for implemented fixed coefficient finite impulse response (FIR) filters. We propose two methods for truncating addition results in an MCM implementation that reduce the area required while decreasing latency. The effects of filter order and coefficient quantization are explored by the proposed search technique that reduces the computations required by an MCM implementation. Two new adaptive filter implementation techniques based on distributed arithmetic (DA) are proposed that provide reduced area and speed without loss of filter performance. Adaptive filter implementations can also be based on realtime conversion of the adapted coefficients into a canonicalsigneddigit (CSD) representation. We propose a new conversion circuit that reduces both latency and area. Finegrained parallelism and relaxed lookahead techniques are applied to develop a pipelined GaussSeidel fast affine projection (GSFAP) adaptive filter implementation that allow degradation to the adaptive filter performance and increases area to achieve significantly faster performance. These proposed techniques for fixed coefficient and adaptive filters can be used for applications in which low area and high speed implementations are required.
Show less  Date Issued
 2011
 Identifier
 FSU_migr_etd3897
 Format
 Thesis
 Title
 Optimization of a Parallel Cordic Architecture to Compute the Gaussian Potential Function in Neural Networks.
 Creator

Chandrasekhar, Nanditha, Baese, Anke Meyer, Baese, Uwe Meyer, Foo, Simon, Department of Electrical and Computer Engineering, Florida State University
 Abstract/Description

Many pattern recognition tasks employ artificial neural networks based on radial basis functions. The statistical characteristics of pattern generating processes are determined by neural networks. The Gaussian potential function is the most common radial basis function considered which includes square and exponential function calculations. The Coordinate Rotations Digital Computer, CORDIC algorithm which is used to compute the exponential function and the exponent was first derived by Volder...
Show moreMany pattern recognition tasks employ artificial neural networks based on radial basis functions. The statistical characteristics of pattern generating processes are determined by neural networks. The Gaussian potential function is the most common radial basis function considered which includes square and exponential function calculations. The Coordinate Rotations Digital Computer, CORDIC algorithm which is used to compute the exponential function and the exponent was first derived by Volder in 1959 for calculating trigonometric functions and conversions between rectangular and polar coordinates. It was later developed by Walther, the CORDIC is a class of shiftadd algorithms for rotating vectors in a plane. In a nutshell, the CORDIC rotator performs a rotation using a series of specific incremental rotation angles selected so that each is performed by a shift and add operation. This thesis focuses on implementation of new parallel hardware architecture to compute the Gaussian Potential Function in neural basis classifiers for pattern recognition. The new hardware proposed computes the exponential function and the exponent simultaneously in parallel thus reducing computational delay in the output function. The new CORDIC is synthesized by Altera's MAX PLUS II software for FLEX 10 K device and improvised for calculation of Radix 4. Case studies are presented and compared on the performance of Radix 2 and Radix 4 design based on the speed and the size occupied respectively. It is observed that though the area occupied by Radix 4 is more as compared to Radix 2 there is speed improvement which is desirable.
Show less  Date Issued
 2005
 Identifier
 FSU_migr_etd3905
 Format
 Thesis
 Title
 Realization of Swarm Behavior in Wireless Communication Systems and Ad Hoc Sensor Networks.
 Creator

Hoang, Hai H. (Hai Hung), Kwan, Bing W., Liu, Xiuwen, Roberts, Rodney, Foo, Simon, MeyerBaese, Anke, Department of Electrical and Computer Engineering, Florida State University
 Abstract/Description

Swarm behavior indicates the direct or indirect interactions among relatively simple agents to perform a particular task that is unknown to the individual agent. The study of swarm behavior originates from the research of swarms in nature such as schools of fish or flocks of birds. The attraction of swarm behavior comes from the collective behavior of independent simple agents, each responding to local information without supervision, to perform a global behavior of the entire swarm. The...
Show moreSwarm behavior indicates the direct or indirect interactions among relatively simple agents to perform a particular task that is unknown to the individual agent. The study of swarm behavior originates from the research of swarms in nature such as schools of fish or flocks of birds. The attraction of swarm behavior comes from the collective behavior of independent simple agents, each responding to local information without supervision, to perform a global behavior of the entire swarm. The first part of the dissertation investigates the incorporation of swarm behavior in particle filtering to improve the performance of channel estimation in narrowband multipleinput multipleoutput (MIMO) wireless communication systems. Channel estimation is required at the receiver to coherently detect the transmitted symbols and has significant impact on the reliability of the systems. Particle filter is a powerful method to approximate the posterior distribution of the channel information given the received signals in the case of nonlinear nonGaussian systems. However, the particle filter method based on importance sampling has problems of importance density selection and noise uncertainty. The suboptimal particle filters with swarm behavior incorporation in part I are proposed to overcome these problems. On the other hand, part II of the dissertation focuses on class of wireless sensor networks utilizing ultra wideband (UWB) technology in the physical layer. UWB technology has potential applications in wireless sensor networks with attractive features such as low cost, low complexity, low power, and multiple access efficiency. A network of large number of eventually identical sensor nodes are considered, in which each node has limited resources and capabilities. There are similarities between the sensor node in the network and the agent in a swarm. The second part proposes a selforganizing protocol based on swarm behavior to the UWB wireless sensor networks. The sensor nodes are grouped into clusters, each of which is able to transfer the information toward a datacollecting node along a steep decent path.
Show less  Date Issued
 2010
 Identifier
 FSU_migr_etd4016
 Format
 Thesis
 Title
 Physical Based Modeling and Simulation of LiFePO₄ Secondary Batteries.
 Creator

Greenleaf, Michael, Zheng, Jim P., Andrei, Petru, Li, Hui, Department of Electrical and Computer Engineering, Florida State University
 Abstract/Description

LiFePO4 batteries have been in existence since 1997 through the work of Padhi et al and showed promise early on due to its material abundance, low cost, low environmental impact, high temperature tolerance and theoretical capacity of 170mAh/g. Much work has been done in optimizing the cathode, electrolyte and anode materials to yield excellent results. In contrast, little work has been done in developing an accurate, physicalbased model for LiFePO4 behavior. Most "models" are based from...
Show moreLiFePO4 batteries have been in existence since 1997 through the work of Padhi et al and showed promise early on due to its material abundance, low cost, low environmental impact, high temperature tolerance and theoretical capacity of 170mAh/g. Much work has been done in optimizing the cathode, electrolyte and anode materials to yield excellent results. In contrast, little work has been done in developing an accurate, physicalbased model for LiFePO4 behavior. Most "models" are based from Electrochemical Impedance Spectroscopy (EIS) and used to fit the data obtained. It is easy to build several vastly different models to describe the same data, so it is therefore important to define a model based upon the physical properties of the cell. In doing so correctly it may then be possible to simplify that model while maintaining precision allowing it to be more useful to other fields. In this work, different EIS measurements were taken at uniform states of charge (SOC) and from a developed physicalbased model a LiFePO4 battery was accurately described for steadystate conditions.
Show less  Date Issued
 2010
 Identifier
 FSU_migr_etd3991
 Format
 Thesis
 Title
 Edge Detection of Noisy Images Using 2D Discrete Wavelet Transform.
 Creator

Chaganti, Venkata Ravikiran, Foo, Simon Y., MeyerBaese, Anke, Roberts, Rodney, Department of Electrical and Computer Engineering, Florida State University
 Abstract/Description

Wavelets are mathematical functions that cut up data into different frequency components, and then study each component with a resolution matched to its scale. Wavelets are an extremely useful tool for coding images and other real signals. Because the wavelet transform is local in both time (space) and frequency, it localizes information very well compared to other transforms. Wavelets code transient phenomena, such as edges, efficiently, localizing them typically to just a few coefficients....
Show moreWavelets are mathematical functions that cut up data into different frequency components, and then study each component with a resolution matched to its scale. Wavelets are an extremely useful tool for coding images and other real signals. Because the wavelet transform is local in both time (space) and frequency, it localizes information very well compared to other transforms. Wavelets code transient phenomena, such as edges, efficiently, localizing them typically to just a few coefficients. This thesis deals with the different types of edge detection techniques, mainly concentrating on the two major categories Gradient and Laplacian. The gradient method detects the edges by looking for the maximum and minimum in the first derivative of the image. The Laplacian method searches for zerocrossings in the second derivative of the image to find edges. Given the wavelet transforms values wavelet analysis can be done in the wavelet domain by comparison of wavelet coefficients that account for the edges. The detection of the maxima or inflection points is generally a key factor for analyzing the characteristics of the nonstationary signals. The wavelet transformation has been proved to be a very promising technique for the multiscale edge detection applied both to 1D and 2D signals. The dyadic wavelet transforms at two adjacent scales are multiplied as a product function to magnify the edge structures and suppress the noise. Unlike many multiscale techniques that first form the edge maps at several scales and then synthesize them together, we determined the edges as the local maxima directly in the scale product after an efficient thresholding. It is shown that the scale multiplication achieves better results than either of the two scales, especially on the localization performance. The thesis deals with the comparison of edge detection of images using traditional edge detection operators (Prewitt, Sobel, Freichen and Laplacian of Gaussian) and Discrete Wavelet Transformation (DWT) using Haar, Daubechies, Coifman and Biorthogonal wavelets. It also deals with the edge detection of noisy images and the optimization of the wavelets for edge detection.
Show less  Date Issued
 2005
 Identifier
 FSU_migr_etd3948
 Format
 Thesis
 Title
 Wavelet Transform Based Image Compression on FPGA.
 Creator

Iqbal, Faizal, Foo, Simon Y, MeyerBaese, Uwe, Roberts, Rodney, Department of Electrical and Computer Engineering, Florida State University
 Abstract/Description

Wavelet Transform has been successfully applied in different fields, ranging from pure mathematics to applied sciences. Numerous studies carried out on Wavelet Transform have proven its advantages in image processing and data compression. Recent progress has made it the basic encoding technique in data compression standards. Pure software implementations of the Discrete Wavelet Transform, however, appear to be the performance bottleneck in realtime systems. Therefore, hardware acceleration...
Show moreWavelet Transform has been successfully applied in different fields, ranging from pure mathematics to applied sciences. Numerous studies carried out on Wavelet Transform have proven its advantages in image processing and data compression. Recent progress has made it the basic encoding technique in data compression standards. Pure software implementations of the Discrete Wavelet Transform, however, appear to be the performance bottleneck in realtime systems. Therefore, hardware acceleration of the Discrete Wavelet Transform has become a topic of interest. The goal of this work is to investigate the feasibility of hardware acceleration of Discrete Wavelet Transform for image compression applications, and to compare the performance improvement against the software implementation. In this thesis, a design for efficient hardware acceleration of the Discrete Wavelet Transform is proposed. The hardware is designed to be integrated as an extension to customcomputing platform and can be used to accelerate multimedia applications as JPEG2000 or MPEG4.
Show less  Date Issued
 2004
 Identifier
 FSU_migr_etd3864
 Format
 Thesis
 Title
 Inferences in Shape Spaces with Applications to Image Analysis and Computer Vision.
 Creator

Joshi, Shantanu H., Srivastava, Anuj, MeyerBaese, Anke, Klassen, Eric, Roberts, Rodney, Foo, Simon Y., Fisher, John W., Department of Electrical and Computer Engineering,...
Show moreJoshi, Shantanu H., Srivastava, Anuj, MeyerBaese, Anke, Klassen, Eric, Roberts, Rodney, Foo, Simon Y., Fisher, John W., Department of Electrical and Computer Engineering, Florida State University
Show less  Abstract/Description

Shapes of boundaries can play an important role in characterizing objects in images. Shape analysis involves choosing mathematical representations of shapes, deriving tools for quantifying shape differences, and characterizing imaged objects according to the shapes of their boundaries. We describe an approach for statistical analysis of shapes of closed curves using ideas from differential geometry. In this thesis, we initially focus on characterizing shapes of continuous curves, both open...
Show moreShapes of boundaries can play an important role in characterizing objects in images. Shape analysis involves choosing mathematical representations of shapes, deriving tools for quantifying shape differences, and characterizing imaged objects according to the shapes of their boundaries. We describe an approach for statistical analysis of shapes of closed curves using ideas from differential geometry. In this thesis, we initially focus on characterizing shapes of continuous curves, both open and closed, in R^2 and then propose extensions to more general elastic curves in R^n. Under appropriate constraints that remove shapepreserving transformations, these curves form infinitedimensional, nonlinear spaces, called shape spaces. We impose a Riemannian structure on the shape space and construct geodesic paths under different metrics. Geodesic paths are used to accomplish a variety of tasks, including the definition of a metric to compare shapes, the computation of intrinsic statistics for a set of shapes, and the definition of intrinsic probability models on shape spaces. Riemannian metrics allow for the development of a set of tools for computing intrinsic statistics for a set of shapes and clustering them hierarchically for efficient retrieval. Pursuing this idea, we also present algorithms to compute simple shape statistics  means and covariances,  and derive probability models on shape spaces using local principal component analysis (PCA), called tangent PCA (TPCA). These concepts are demonstrated using a number of applications: (i) unsupervised clustering of imaged objects according to their shapes, (ii) developing statistical shape models of human silhouettes in infrared surveillance images, (iii) interpolation of endo and epicardial boundaries in echocardiographic image sequences, and (iv) using shape statistics to test phylogenetic hypotheses. Finally, we present a framework for incorporating prior information about highprobability shapes in the process of contour extraction and object recognition in images. Here one studies shapes as elements of an infinitedimensional, nonlinear quotient space, and statistics of shapes are defined and computed intrinsically using differential geometry of this shape space. Prior models on shapes are constructed using probability distributions on tangent bundles of shape spaces. Similar to the past work on active contours, where curves are driven by vector fields based on image gradients and roughness penalties, we incorporate prior shape knowledge also in form of gradient fields on curves. Through experimental results, we demonstrate the use of prior shape models in estimation of object boundaries, and their success in handling partial obscuration and missing data. Furthermore, we describe the use of this framework in shapebased object recognition or classification. This Bayesian shape extraction approach is found to yield a significant improvement in detection of objects in presence of occlusions or obscurations.
Show less  Date Issued
 2007
 Identifier
 FSU_migr_etd3697
 Format
 Thesis
 Title
 Minimizing FIR Filter Designs Implemented in FPGAs Utilizing Minimized Adder Graph Techniques.
 Creator

Howard, Charles D., DeBrunner, Linda S., DeBrunner, Victor, Harvey, Bruce A., Department of Electrical and Computer Engineering, Florida State University
 Abstract/Description

Multiple constant multiplications (MCM) is an optimization technique that is wellsuited to DSP implementations. Using MCM, all coefficient multiplications are grouped into one efficient block of wired shifts and adds. A disadvantage of using MCM is the requirement of knowing the filter coefficients {it a priori}. Due to this limitation, MCM optimizations cannot be used in many applications. We propose a programmable adder graph (PAG) circuit that can implement multiplication using shift and...
Show moreMultiple constant multiplications (MCM) is an optimization technique that is wellsuited to DSP implementations. Using MCM, all coefficient multiplications are grouped into one efficient block of wired shifts and adds. A disadvantage of using MCM is the requirement of knowing the filter coefficients {it a priori}. Due to this limitation, MCM optimizations cannot be used in many applications. We propose a programmable adder graph (PAG) circuit that can implement multiplication using shift and add techniques without prior knowledge of the multiplier value. The PAG circuit allows any programmable device to be optimized using MCM for a wide range of DSP applications, including adaptive filters.
Show less  Date Issued
 2009
 Identifier
 FSU_migr_etd3725
 Format
 Thesis
 Title
 Statistical Modeling of SmallScale Fading Channels.
 Creator

Hekeno, Mahinga, Kwan, Bing W., Yu, Ming, Arora, Krishna, Department of Electrical and Computer Engineering, Florida State University
 Abstract/Description

With the increase of wireless networks, consumers are increasingly aware of the importance and convenience of wireless technology. Wireless technologies such as WLANs, mobile phones, blue tooth or PCS rely on a range of mechanisms to provide for high Quality of Service (QoS), the core of which would be accurate modeling of the wireless channels. The radio channel emanates timevariant linear channel characteristics. In this research, the analysis of the statistics of the underlying channel...
Show moreWith the increase of wireless networks, consumers are increasingly aware of the importance and convenience of wireless technology. Wireless technologies such as WLANs, mobile phones, blue tooth or PCS rely on a range of mechanisms to provide for high Quality of Service (QoS), the core of which would be accurate modeling of the wireless channels. The radio channel emanates timevariant linear channel characteristics. In this research, the analysis of the statistics of the underlying channel behavior is investigated using a developed physicsbased channel model that characterizes smallscale fading behavior the wireless channels. Specifically, we investigate Flat Slow Fading, Flat Fast Fading, FrequencySelective Slow Fading and FrequencySelective Fast Fading propagation channels. This thesis will provide for computer simulation of a physicsbased channel model to define the essential channel parameters, and subsequently reproduce the characterized channel by appropriately utilizing the autoregressive process to remodel the attained channel data. The principal method for this study is the use of LevinsonDurbin recursion to build a signal model for channel analysis. The motivation for this research is, given a set of channel parameters obtained from the physicsbased channel model, the proposed autoregressive signal model can reproduce the physical channel parameters and accurately predict the nature of small scale fading present in a channel whether it is Flat Slow Fading, Flat Fast Fading, FrequencySelective Slow Fading or FrequencySelective Fast Fading. Performance comparisons are then made from the generated physical properties of the channel with the simulation results of the constructed autoregressive model built by the use of statistical comparison analysis such as autocorrelation properties to demonstrate the merits of the approach. This manuscript is organized as follows; Chapter one provides an introduction and background information of communication systems. Chapter two describes random timevarying channels, different parameters affecting the propagation of signals in the communication channel; phenomena such as Doppler shift and multipath delay are discussed. The physicsbased channel is developed in chapter two. Chapter three discusses different parameters that can be used to categorize wireless channels and types of multipath fading that can happen in a wireless channel. Autoregressive channel modeling using LevinsonDurbin recursion is discussed in chapter four. Simulation results of the developed model are provided and discussed in chapter five. Chapter six gives a conclusion and discusses areas where further studies need to be carried out.
Show less  Date Issued
 2008
 Identifier
 FSU_migr_etd4134
 Format
 Thesis
 Title
 SAS Yaw Motion Compensation Using AlongTrack Phase Filtering.
 Creator

Joshi, Shantanu H., Gross, Frank B., Arora, Krishna R., Roberts, Rodney R., Department of Electrical and Computer Engineering, Florida State University
 Abstract/Description

In order to image or map targets on an ocean floor, a synthetic aperture sonar platform is moved underwater over the ocean floor. The platform pings or transmits acoustic signals, which reflect off the target back to the receiver. A target image is generated after applying a focusing or a beamforming algorithm on the processed received signal. However the moving platform, when pinging, undergoes motions like yaw, sway, surge, which produce distortions in the final target image. The main...
Show moreIn order to image or map targets on an ocean floor, a synthetic aperture sonar platform is moved underwater over the ocean floor. The platform pings or transmits acoustic signals, which reflect off the target back to the receiver. A target image is generated after applying a focusing or a beamforming algorithm on the processed received signal. However the moving platform, when pinging, undergoes motions like yaw, sway, surge, which produce distortions in the final target image. The main objective of this thesis is to geometrically model yaw motion and apply the motion compensation scheme to correct for the yaw motion causing target image distortion. The compensation scheme makes use of phase filtering of the received signals to improve the target image quality. The results obtained, demonstrate effectiveness of the method to compensate for the target image distortion due to yaw motion.
Show less  Date Issued
 2002
 Identifier
 FSU_migr_etd3691
 Format
 Thesis
 Title
 A Study of DespreadRespread Multitarget Adaptive Algorithms in an AWGN Channel.
 Creator

Connor, Jeffrey D., Gross, Frank B., Foo, Simon, Kwan, Bing W., Department of Electrical and Computer Engineering, Florida State University
 Abstract/Description

Typical adaptive algorithms attempt to exploit some characteristic of a desired mobile user's signal incident upon an array of antenna elements to form a blind estimate of the user's signal, wherein this estimate is used to update weights added to each element of the array in order to perform beamsteering. Generally, when mobile user's operate in a CDMA mobile environment two particular characteristics are exploited: 1.) Minimizing the Mean Square Error (MSE) between the array output and the...
Show moreTypical adaptive algorithms attempt to exploit some characteristic of a desired mobile user's signal incident upon an array of antenna elements to form a blind estimate of the user's signal, wherein this estimate is used to update weights added to each element of the array in order to perform beamsteering. Generally, when mobile user's operate in a CDMA mobile environment two particular characteristics are exploited: 1.) Minimizing the Mean Square Error (MSE) between the array output and the blind estimate of the desired user. 2.) Restoring the constant modulus to the output of the adaptive array corrupted by noise in the channel. These typical adaptive algorithms do not utilize knowledge of the spreading sequences used in a CDMA system, which separate users occupying the same frequency and time channels. However, this knowledge is exploited by DespreadRespread Multitarget Arrays (DRMTA). The four DRMTA algorithms which currently exist are: 1.) Least Squares DespreadRespread Multitarget Constant Modulus Array (LSDRMTCMA) 2.) Least Squares DespreadRespread Multitarget Array (LSDRMTA) 3.) Block Based RLS DespreadRespread Multitarget Array (BRLSDRMTA) 4.) DespreadRespread Kalman Predictor Multitarget Array (DRKPMTA) The objective of this thesis is to develop a comparison between these four algorithms for a stationary, additive white Gaussian noise (AWGN) channel in a CDMA mobile environment using MATLAB computer simulations for the following metrics: 1.) Analyzing Array Factor Patterns (Beampatterns) 2.) SignaltoInterferenceplusNoise Ratio (SINR) 3.) Convergence Degree of Weight (CDW) 4.) Bit Error Rate (BER) These comparisons are performed for several different scenarios:  Highly corruptive AWGN channel.  Low SINR environment.  Response to poor initial conditions.  Measuring Convergence characteristics.  Number of users greater than or equal to number of elements in array.  Response to a sudden increase in total number of users in environment  Reduced orthogonality of spreading sequences.  Minimizing MSE by maximizing CDW.
Show less  Date Issued
 2005
 Identifier
 FSU_migr_etd3454
 Format
 Thesis
 Title
 Gallium Arsenide Mesfet SmallSignal Modeling Using Backpropagation & RBF Neural Networks.
 Creator

Langoni, Diego, Weatherspoon, Mark H., MeyerBäse, Anke, Department of Electrical and Computer Engineering, Florida State University
 Abstract/Description

The smallsignal intrinsic ECPs (equivalent circuit parameters) of a 4x50 µm gate width, 0.25 µm gate length GaAs (gallium arsenide) MESFET (metal semiconductor fieldeffect transistor) were modeled versus bias (voltage and current) and temperature using backpropagation and RBF (radial basis function) ANNs (artificial neural networks). The resulting ANNs consisted of 3input, 8output models of the MESFET ECPs and were compared to each other in terms of memory usage, convergence speed, and...
Show moreThe smallsignal intrinsic ECPs (equivalent circuit parameters) of a 4x50 µm gate width, 0.25 µm gate length GaAs (gallium arsenide) MESFET (metal semiconductor fieldeffect transistor) were modeled versus bias (voltage and current) and temperature using backpropagation and RBF (radial basis function) ANNs (artificial neural networks). The resulting ANNs consisted of 3input, 8output models of the MESFET ECPs and were compared to each other in terms of memory usage, convergence speed, and accuracy. Also, each network's performance was evaluated under "normal" training conditions (75% training data with a uniform distribution) and "stressed" training conditions (50% and 25% training data with a uniform distribution, 75%, 50%, and 25% training data with a skewed distribution). The results showed that for the RBF network, much better overall convergence speed as well as better accuracy under both "normal" and "moderately stressed" training conditions were obtained. However, the backpropagation network yielded better accuracy for the "extremely stressed" training conditions and better overall memory usage.
Show less  Date Issued
 2005
 Identifier
 FSU_migr_etd3286
 Format
 Thesis
 Title
 Throughput Improvement in Multihop Ad Hoc Network Using Adaptive Carrier Sensing Range and Contention Window.
 Creator

Acholem, Onyekachi, Harvey, Bruce, Zhang, Zhenghao, Srivastava, Anuj, Roberts, Rodney, Foo, Simon, Department of Electrical and Computer Engineering, Florida State University
 Abstract/Description

Demand for decentralized, wireless, adhoc systems, where hosts are free to leave or join, to replace wired communication systems has seen a phenomenal growth. Such networks need little or no infrastructure support to operate. Deploying these networks such as in wireless sensor networks (WSN) enables new frontiers in developing opportunities to collect and process data from remote locations. The large number of nodes in these wireless networks invariably results in higher node densities and...
Show moreDemand for decentralized, wireless, adhoc systems, where hosts are free to leave or join, to replace wired communication systems has seen a phenomenal growth. Such networks need little or no infrastructure support to operate. Deploying these networks such as in wireless sensor networks (WSN) enables new frontiers in developing opportunities to collect and process data from remote locations. The large number of nodes in these wireless networks invariably results in higher node densities and increased levels of network interference. Interference mitigation is therefore crucial in ensuring these networks operate efficiently. Often the lack of network planning and regulations for such networks require the targeted access strategy to be adaptive to network conditions and distributed. The goal of this research is to design an algorithm employing mathematical tools in optimizing spatial reuse among nodes in the ad hoc network so that multiple communications between nodes can proceed simultaneously thereby maximizing the network throughput. To maximize spatial reuse, the IEEE 802.11 Medium Access Control (MAC) protocol would be modified so that each transmitting node can finetune its data rate and carrier sense range adaptively depending on minimal receiver response local data. All nodes must be able to detect and communicate with their neighbors in order to determine the network structure, to execute network functions and transmit collated information back to the remote node. The network topology will be discovered using clustering schemes such as the Kmeans technique that minimizes the Euclidean distance between random nodes. Each cluster will have a cluster head that would keep track of local information about nodes in its cluster. A further goal of this research would be to demonstrate that the physical carrier sensing incorporated in the 802.11 MAC protocol can adaptively optimize the sensing threshold of the nodes and minimize interference within the network without the benefit of the requesttosend and cleartosend handshake of the virtual carrier sensing. Considerable nodal energy and packet overhead would be saved by turning off the RTS/CTS handshake process. An analytic design will be presented for acquiring the optimal sensing threshold given a network topology; data rate and transmit/receive power of the nodes. Two major issues to be addressed in improving spatial reuse are: 1. The optimal range of transmit data rate/ carrier sense threshold for maximum network capacity 2. The relationship between the carrier sense threshold and contention window. Furthermore, results from this research will show that tuning the carrier sense threshold and contention window offers several advantages including delivering considerable aggregate throughput more than that obtained from a static carrier sense threshold network with no previous knowledge of the network topology. This will enable nodes sustain a high data rate, while maintaining the adverse effect of collision on other neighboring simultaneous communications at minimum. In the end, the communication protocol will be improved to achieve better utilization of the scarce wireless spectrum. The simulation and performance evaluation tools required for this work would be Network Simulator2 (NS2) simulator, AWK and PERL programming languages.
Show less  Date Issued
 2010
 Identifier
 FSU_migr_etd0108
 Format
 Thesis
 Title
 Analysis of Aftereffect Phenomena and Noise Spectral Properties of Magnetic Hysteretic Systems Using Phenomenological Models of Hysteresis.
 Creator

Adedoyin, Ayodeji Adeoye, Andrei, Petru, Chiorescu, Irinel, Arora, Rajendra K., Foo, Simon Y., Zheng, Jim P., Department of Electrical and Computer Engineering, Florida State...
Show moreAdedoyin, Ayodeji Adeoye, Andrei, Petru, Chiorescu, Irinel, Arora, Rajendra K., Foo, Simon Y., Zheng, Jim P., Department of Electrical and Computer Engineering, Florida State University
Show less  Abstract/Description

A robust and computationally efficient MonteCarlo based technique is developed to analyze the magnetic aftereffect and noise passage phenomena in magnetic hysteretic systems by using phenomenological models of hysteresis. The technique is universal and can be applied to model the aftereffect and noise passage phenomena in the framework of both scalar and vector models of hysteresis. Using this technique, we analyze a variety of magnetic viscosity phenomena. Numerical results related to the...
Show moreA robust and computationally efficient MonteCarlo based technique is developed to analyze the magnetic aftereffect and noise passage phenomena in magnetic hysteretic systems by using phenomenological models of hysteresis. The technique is universal and can be applied to model the aftereffect and noise passage phenomena in the framework of both scalar and vector models of hysteresis. Using this technique, we analyze a variety of magnetic viscosity phenomena. Numerical results related to the decay of the magnetization as a function of time as well as to the viscosity coefficient are presented. It is shown that a logt (logarithmic time)  type dependence of the average value of the magnetization can be predicted qualitatively in the framework of phenomenological models of hysteresis, such as the Preisach, Energetic, JilesAtherton, and Hodgdon models. The basic assumption of the techniques developed in this dissertation is that the total applied field is equal to the external applied field plus a random perturbation field. The total magnetic field is used as input in the scalar or vector models of hysteresis (vector models of hysteresis are defined in this dissertation as a superposition of scalar models of hysteresis distributed along all possible spatial directions). A statistical approach is developed to compute the average value and direction of the magnetization vector as a function of time. Whereas in the case of isotropic materials the magnetization vector usually moves on a straight line oriented towards the direction of the applied field, in the case of anisotropic materials the magnetization vector can switch from one easy axis to another and cross the direction of the applied field. It is shown that, depending on the initial hysteretic state, the trajectory of the magnetization vector can deviate substantially from the straight line, which is a pure vectorial relaxation effect. The vectorial properties of magnetic viscosity and data collapse phenomena are also investigated. The definition of the viscosity coefficient, which has been traditionally used to model aftereffect phenomena in scalar magnetic systems, is generalized in order to describe three dimensional systems, where both the direction and the magnitude of the magnetization vector can change in time. Using this generalization of the vector viscosity coefficient, we have analyzed data collapse phenomena in vectorial magnetization processes. It was found that the traditional bellshaped curves of the scalar viscosity coefficient as a function of the applied field can have one or more maxima in the case of vectorial systems. The data collapse phenomena seem to apply to simple magnetization processes (such as firstorder rotational reversal curves); however, it cannot be generalized to more complex magnetization processes because of the relatively complicated magnetization dynamics. In the final part of this dissertation we present a statistical technique based on MonteCarlo simulations, which we developed to compute the spectral densities of the output variable in phenomenological models of hysteresis. The input signal is described by an OrnsteinUhlenbeck process and the magnetization is computed by using various phenomenological models of hysteresis: the Energetic, JilesAtherton, and Preisach models. General qualitative features of these spectral densities are examined and their dependence on various parameters is discussed. For values of the diffusion coefficient near and smaller than the coercive field, the output spectra deviate significantly from the Lorentzian shape, characteristic to the input process. The intrinsic differences between the transcendental, differential, and integral modeling of hysteresis yield significantly different spectra at low frequency region, which reflect the longtime correlation behavior.
Show less  Date Issued
 2009
 Identifier
 FSU_migr_etd0119
 Format
 Thesis
 Title
 Techniques to Improve the Accuracy of System Identification in NonGaussian and Time Varying Environments.
 Creator

Ta, Minh Quang, DeBrunner, Victor, Chicken, Eric, DeBrunner, Linda, Roberts, Rodney, Department of Electrical and Computer Engineering, Florida State University
 Abstract/Description

Estimation of a dynamical system under unknown influences is always subjected to uncertainty. Thus, reducing the estimation variance under external influences is absolutely desired and becomes the motivation for the field of System Identification. In this dissertation, the author proposes new techniques for system identification under two major general situations: offline estimation of fixed systems under the unknown nonGaussian distributed measurement noise, and onlineestimation of time...
Show moreEstimation of a dynamical system under unknown influences is always subjected to uncertainty. Thus, reducing the estimation variance under external influences is absolutely desired and becomes the motivation for the field of System Identification. In this dissertation, the author proposes new techniques for system identification under two major general situations: offline estimation of fixed systems under the unknown nonGaussian distributed measurement noise, and onlineestimation of timevarying systems undergoing systematic (long term correlated) changes. For the first situation of offline estimating of fixed systems under the unknown nonGaussian distributed measurement noise, a technique called Minimum Entropy Estimation is employed, which promises to be better than the traditional Least Square (LS) estimation method due to the ability to simultaneously estimate the system and the statistical property of the unknown measurement noise sequence. This method gives rise to two novel classes of generalized offline estimation algorithms being proposed in this dissertation: a method of estimating a MultipleInputMultipleOutput (MIMO) systems under unknown, independent and identically distributed (iid) nonGaussian measurement noise, and a more general method of estimating a feedback structure under unknown, possibly colored, nonGaussian distributed measurement noise. For the second situation of online estimation of timevarying systems undergoing systematic changes, a new method of ParameterFiltering Adaptation (PFA) algorithm is proposed for the first time as an attempt to solve this problem and improve the estimation quality. Instead of updating the parameter based on the prediction error and an estimated value of the parameter at single time iteration (before the current one) as in the traditional adaptive algorithms, the new method improves the estimation quality of the system parameter by incorporating its prediction from all previous estimated values. The parameter prediction transfer function itself is also updated adaptively. The PFA algorithm is firstly considered in the context of IIR filter estimation to show the benefit of better local quadratic approximation for the timevarying, nonquadratic error surface. Its application in the spectral estimation of timevarying chirps utilizing Adaptive Notch Filters has shown an enormously better estimation of the instantaneous frequency. In the context of estimating timevarying systems using FIR filters, it is discovered that the PFA has a filtering effect on the sequence of the (estimated) parameters. Consequently it is shown in the dissertation that the sparser in the frequency domain (less frequency bandwidth) the parameter variations are, the better their estimation quality. Simulation on tracking of sinusoidal timevarying systems, as well as periodically switching systems shows that the PFA has a superior estimation quality with virtually no lag comparing to the traditional tracking methods.
Show less  Date Issued
 2008
 Identifier
 FSU_migr_etd0311
 Format
 Thesis
 Title
 A Computer Simulation Model for Microwave Link Path Loss Prediction.
 Creator

Khong, Hung Huy, Kwan, Bing W., Tung, Leonard J., Foo, Simon Y., Department of Electrical and Computer Engineering, Florida State University
 Abstract/Description

In this manuscript, a computer simulation model for the study of the largescale effects on narrowband transmission systems is proposed to validate the existing semiempirical models. The development of the computer simulation pathloss model is based on the ray tracing technique. It is emphasized that multipath signals are considered in this model. This study only concentrates on the firstorder scattering effects, namely each multipath signal is a twohop signal that involves a single...
Show moreIn this manuscript, a computer simulation model for the study of the largescale effects on narrowband transmission systems is proposed to validate the existing semiempirical models. The development of the computer simulation pathloss model is based on the ray tracing technique. It is emphasized that multipath signals are considered in this model. This study only concentrates on the firstorder scattering effects, namely each multipath signal is a twohop signal that involves a single scattering object. The first hop is directed toward the scatterer from the transmitter (TX); and the second hop goes from the scatterer to the receiver (RX). Each hop signal is described using a tworay model due to directpath propagation and groundreflected path propagation. When the number of scattering objects is large, the simulation results are consistent with the semiempirical models that are based on measurements, including the Hata model, the Lee model, and the model reported in [3]. Typically, the pathloss increases linearly with log distance. However, when the number of scattering objects is small, the linear model for path loss is not universally valid. In particular, when the path loss and log distance are weakly correlated in a linear manner, the linear model may lead to physically unrealizable results. This observation has not been made by the various groups that studied channel modeling based on measurements. In addition, the proposed model enjoys the flexibility in studying the effects of scattering object density in the channel, the radar cross section of the scattering objects, the ground reflection coefficients, and the distance between the TX and the RX. Furthermore, coherent multipath signals can cause the pathloss exponent to fall below 2, which corresponds to freespace propagation.
Show less  Date Issued
 2009
 Identifier
 FSU_migr_etd3143
 Format
 Thesis
 Title
 Birdcage Coils for MRI: In Vivo Imaging of 35Chlorine and 1Hydrogen Nuclei.
 Creator

Elumalai, Malathy, Foo, Simon Y., Brey, William W., Andrei, Petru, Arora, Rajendra K., Department of Electrical and Computer Engineering, Florida State University
 Abstract/Description

In this thesis, three different RF coils were investigated for their application in Magnetic Resonance Imaging (MRI). We developed transmit/receive birdcage volume coils since they provide better B1 field homogeneity than other coils. Coils were developed for in vivo imaging of chlorine and hydrogen nuclei. Chlorine is a low γ nucleus, therefore its sensitivity is very low. The high field of 21.1 T at NHMFL was exploited in order to obtain better signal strength from chlorine. Also, a...
Show moreIn this thesis, three different RF coils were investigated for their application in Magnetic Resonance Imaging (MRI). We developed transmit/receive birdcage volume coils since they provide better B1 field homogeneity than other coils. Coils were developed for in vivo imaging of chlorine and hydrogen nuclei. Chlorine is a low γ nucleus, therefore its sensitivity is very low. The high field of 21.1 T at NHMFL was exploited in order to obtain better signal strength from chlorine. Also, a comparative study was conducted between the linear coil and the quadrature coil of chlorine. Quadrature excitation helps in increasing the RF power efficiency, and results in up to √2 improvement in signaltonoise ratio. In this work, strategies are presented for tuning, matching and isolating the two ports. We developed a third coil for proton imaging which incorporated the sliding ring tuning mechanism. The principle of sliding ring is to provide distributed capacitance. This results in tuning across all legs which in turn helps to maintain the symmetry of the birdcage coil. The resonance and quality factor was measured for all the three coils when loaded with saline, oil and poly ethylene glycol (PEG) solutions. In vivo experiments were carried out in order to image phantoms and rats in the 21.1 T magnet. It was observed that the quadrature chlorine coil provided 1.18 times improvement in sensitivity when compared to the linear coil. The sliding ring coil for proton helped in preserving the symmetry; it offered better tuning range when compared to the fixed lumped element design. RF coils are critically important in the performance of MRI scanners. We believe that the studies conducted in this project are contributions toward obtaining better imaging systems.
Show less  Date Issued
 2011
 Identifier
 FSU_migr_etd0566
 Format
 Thesis
 Title
 FPGABased Real Time Processing of TimeVarying Waveform Distortions and Power Disturbances in Power Systems.
 Creator

Xu, Jinglin, MeyerBaese, Uwe, Ordóñez, Juan, Li, Hui, MeyerBaese, Anke, Department of Electrical and Computer Engineering, Florida State University
 Abstract/Description

Waveform distortions in power systems are inherently timevarying due to continuous changes in system configurations, load types, and load levels. The timevarying nature of waveform distortions requires a real time tool to process that is essential in several applications including control, protection, and monitoring in power systems. The traditional fast Fourier transform (FFT) is known to lost accuracy in nonstationary conditions. Some techniques for examining the timevarying nature of...
Show moreWaveform distortions in power systems are inherently timevarying due to continuous changes in system configurations, load types, and load levels. The timevarying nature of waveform distortions requires a real time tool to process that is essential in several applications including control, protection, and monitoring in power systems. The traditional fast Fourier transform (FFT) is known to lost accuracy in nonstationary conditions. Some techniques for examining the timevarying nature of the waveform have been proposed in the past. But most of proposed techniques are not suitable for real time processing and practical implementations. There is still a need for developing faster, more precise and more robust algorithms with simple structure for real time processing and implementation purposes. Generalpurpose programmable Digital Signal Processors (PDSPs) have enjoyed tremendous success in implementing most Digital Signal Processing (DSP) algorithm in power systems for the last two decades and work as the real time task processor in power quality monitoring systems. Field Programmable Gate Arrays (FPGAs) are becoming more and more affordable and the performance of FPGAs continues to increase. The FPGA is used in many applications as an alternative device to the PDSP. Most algorithms for power quality monitoring are digital filtering based algorithms. The FPGA is known to be more efficient than PDSP in implementing digital filtering algorithms, which makes the FPGAbased architecture an attractive option for power quality monitoring systems. In the past, very little FPGA implementation of power quality algorithms was provided. In this dissertation, an amplitude tracking algorithm derived from universal Amplitude Demodulation (AMDemodulation) method in telecommunications is proposed for real time tracking of timevarying waveform distortions in power systems. The proposed algorithm also works for real time tracking of power disturbances. The amplitude tracking algorithm consists of frequency mixer calculations, lowpass filtering, and coordinate transformation. The IIR (Infinite Impulse Response) filter was considered as the most efficient computation path and was selected to implement the required lowpass filtering. The COordinate Rotation DIgital Computer (CORDIC) algorithm is used for required rectangular to polar coordinate conversions. The CORDIC algorithm needs only addition and shift operations and greatly reduces the circuit complexity. The proposed algorithm has a linear computational complexity of . The propose amplitude tracking algorithm has real time characteristics of mathematical simplicity, accuracy, low latency, and robustness. Compared with the traditional FFT algorithm, one advantage of the proposed algorithm is that the proposed algorithm does not need integer periods sampled. In this dissertation, the FPGA is introduced in the power quality monitoring for processing of real time tasks. The FPGA implementation of the proposed algorithm is presented. Appropriate choice of word length and implementation method, such as the Canonical signed digit (CSD) coding and the zero first implementation, achieves large circuit savings. The amplitude tracking circuit has been built on a Xilinx Spartan3 XC3S200 FPGA. The real time capability of the proposed algorithm and circuit was verified through experiments. This dissertation provides an alternative method for real time processing of timevarying waveform distortions and power disturbances in power systems. The proposed algorithm is suitable for practical implementations. This dissertation also indicates that the FPGAbased architecture could be an alternative to the traditional PDSPbased architecture of power quality monitoring systems.
Show less  Date Issued
 2009
 Identifier
 FSU_migr_etd0418
 Format
 Thesis
 Title
 Response Surface Methodology for the Analysis of Grounding in a Medium Voltage DC Shipboard Power System.
 Creator

Lee, Dorca D., Baldwin, Thomas, Edrington, Chris S., DeBrunner, Victor, Steurer, Michael, Department of Electrical and Computer Engineering, Florida State University
 Abstract/Description

Response surface methodology is used to study the effectiveness of different grounding schemes implemented for the mitigation of a singlelinetoground fault in a medium voltage DC (MVDC) power system. Multivariate adaptive regression splines (MARS) models are used to obtain preliminary functional relationships between the input parameters and response variables of the MVDC power system. From the MARS models, probability density plots are constructed for each response variable under all...
Show moreResponse surface methodology is used to study the effectiveness of different grounding schemes implemented for the mitigation of a singlelinetoground fault in a medium voltage DC (MVDC) power system. Multivariate adaptive regression splines (MARS) models are used to obtain preliminary functional relationships between the input parameters and response variables of the MVDC power system. From the MARS models, probability density plots are constructed for each response variable under all grounding schemes. Additionally, for the different grounding schemes, Sobol total sensitivity indices are computed to gauge the impact of the input parameters on the response variables. Lastly, for response surface models in which MARS shows significant prediction error, maximum likelihood estimation Gaussian process (MLEGP) models are built.
Show less  Date Issued
 2010
 Identifier
 FSU_migr_etd3154
 Format
 Thesis
 Title
 A Comparitive Study of Supervised and Unsupervised Learning Methods in Forecasting the U.S. 30Year Treasury Bond Yield.
 Creator

Powell, Nicole Andrea, Foo, Simon Y., MeyerBaese, Anke, Weatherspoon, Mark H., Department of Electrical and Computer Engineering, Florida State University
 Abstract/Description

The prediction of any aspect of the future has always fascinated mankind because of the possible benefits of this knowledge, especially financial benefits. From year to year, many stockholders would like to be able to know if the price of their commodity will increase or decrease, and in turn this prediction may help them in the decision to buy more or sell what they currently have. It is widely known that the stock market is a volatile and complex entity which is affected by various factors...
Show moreThe prediction of any aspect of the future has always fascinated mankind because of the possible benefits of this knowledge, especially financial benefits. From year to year, many stockholders would like to be able to know if the price of their commodity will increase or decrease, and in turn this prediction may help them in the decision to buy more or sell what they currently have. It is widely known that the stock market is a volatile and complex entity which is affected by various factors such as government policies, political situations, public events, internal company politics and much more. However there is no way of knowing exactly which factor will affect stock prices and how much the price will be affected. Financial trend forecasting is a major component in corporate finance because predictions of future prices, indices, volumes and several other values are often incorporated into the economic decisionmaking process for a particular company. For the average investor financial trend forecasting would mean a greater profit (or smaller loss). To recognize specific trends for forecasting capabilities, it is important to develop a method for eliminating speculation and to investigate new algorithms for detecting patterns. Although there are many different approaches available, in this thesis a comparison between an unsupervised classification technique, namely Kmeans clustering, and supervised learning algorithms, namely support vector machines and radial basis functions, will be performed. The three pattern recognition systems will be tested against realworld data concerning the U.S. 30Year Treasury bond yield. Determining the yield trend is approached as a technical analysis problem for this particular study: ignoring underlying factors and focusing on finding patterns directly from historical data. The results from each of the three networks are compared and analyzed. The performance measures analyzed include accuracy percentages, return on investment ratios, as well as capital gains/losses. From this analysis, a general network model can be decided upon to forecast the U.S. 30Year Treasury bond yield.
Show less  Date Issued
 2008
 Identifier
 FSU_migr_etd0447
 Format
 Thesis
 Title
 Design of a Compact Microstrip Patch Antenna for Use in Wireless/Cellular Devices.
 Creator

Nakar, Punit S., Gross, Frank, Arora, Krishna, Roberts, Rodney, Department of Electrical and Computer Engineering, Florida State University
 Abstract/Description

The cellular industry came into existence 25 years ago and as of today, there are approximately 150 million subscribers worldwide. The cellular industry generates $30 billion in annual revenues and is one of the fastest growing industries. The cellular handsets being used in the 1980s were bulky and heavy. Advancements in VLSI technology have enabled size reduction for the various microprocessors and signal processing chips being used in cellular phones. Another method for reducing handset...
Show moreThe cellular industry came into existence 25 years ago and as of today, there are approximately 150 million subscribers worldwide. The cellular industry generates $30 billion in annual revenues and is one of the fastest growing industries. The cellular handsets being used in the 1980s were bulky and heavy. Advancements in VLSI technology have enabled size reduction for the various microprocessors and signal processing chips being used in cellular phones. Another method for reducing handset size is by using more compact antennas. The aim of this thesis is to design such a compact antenna for use in wireless/cellular devices. A Microstrip Patch Antenna consists of a dielectric substrate on one side of a patch, with a ground plane on the other side. Due to its advantages such as low weight and volume, low profile planar configuration, low fabrication costs and capability to integrate with microwave integrated circuits (MICs), the microstrip patch antenna is very well suited for applications such as cellular phones, pagers, missile systems, and satellite communications systems. A compact microstrip patch antenna is designed for use in a cellular phone at 1.9 GHz. The results obtained provide a workable antenna design for incorporation in a cellular phone.
Show less  Date Issued
 2004
 Identifier
 FSU_migr_etd2790
 Format
 Thesis
 Title
 Implementation of Chirpz Discrete Fourier Transform on Virtex II FPGA.
 Creator

Natarajan, Hariharan, Department of Electrical and Computer Engineering, Florida State University
 Abstract/Description

The application of Fourier results in conversion in representation of a signal in time domain to frequency domain. Hence, it forms an important tool for frequency analysis. With advent of digital computers, we can perform frequency analysis faster and more efficiently. Thus discrete Fourier transform is important for frequency analysis of signal in discrete form. Discrete Fourier Transform (DFT) and Fast Fourier Transform (FFT) algorithms have been invented in several variations. This thesis...
Show moreThe application of Fourier results in conversion in representation of a signal in time domain to frequency domain. Hence, it forms an important tool for frequency analysis. With advent of digital computers, we can perform frequency analysis faster and more efficiently. Thus discrete Fourier transform is important for frequency analysis of signal in discrete form. Discrete Fourier Transform (DFT) and Fast Fourier Transform (FFT) algorithms have been invented in several variations. This thesis focuses on implementation of the Bluestein Chirpz transform algorithm. This method uses chirp signals, which are complex exponential signals, which increase linearly with time. Hence, the name chirpz Transform. The transform is implemented on Xilinx Inc.'s Virtex II FPGA. Virtex II family has two of the world's largest programmable device with gate count up to 8 million. It's features like embedded multiplier and memory make it ideal for digital signal processing applications. The implementation of chirpz transform would involve designing a ROM to store the twiddle factors; a complex number multiplier and FIR filter for convolution. Again, we look at various algorithms for calculation of filter coefficient for minimum cost of adder and multiplier. DFT are implemented for length 4 point, 16 point, 32 point and 64 point. We analyze each of the abovementioned implementations and especially the space occupied and the speed of the device.
Show less  Date Issued
 2004
 Identifier
 FSU_migr_etd2725
 Format
 Thesis
 Title
 Predictive Harmonic Cancellation Using Neural Networks.
 Creator

Malinconico, Brian, Foo, Simon, Roberts, Rodney, MeyerBaese, Anke, Department of Electrical and Computer Engineering, Florida State University
 Abstract/Description

Filtering is an important aspect of the modern power system. By reducing the effects of harmonics, power transmission and utilization becomes more efficient. This research examines the use of neural networks for the estimation and prediction of harmonics. The utilization of neural networks for adaptive harmonic prediction, allows the cancellation of harmonics before their creation. A large part of this research focuses on the estimation of Fourier coefficients. By identifying the strengths...
Show moreFiltering is an important aspect of the modern power system. By reducing the effects of harmonics, power transmission and utilization becomes more efficient. This research examines the use of neural networks for the estimation and prediction of harmonics. The utilization of neural networks for adaptive harmonic prediction, allows the cancellation of harmonics before their creation. A large part of this research focuses on the estimation of Fourier coefficients. By identifying the strengths and weaknesses of neural networks for Fourier coefficient estimation future direction for research was determined. The deficiencies of the developed networks prevent the application of this system in reallife situations. Despite the need for future research, the performance of the neural networks shows significant possibilities.
Show less  Date Issued
 2010
 Identifier
 FSU_migr_etd2770
 Format
 Thesis
 Title
 Phenomenological Equivalent Circuit Modeling of Various Energy Storage Devices.
 Creator

Greenleaf, Michael C., Zheng, Jim, Shih, Chiang, Li, Helen, Andrei, Petru, Moss, Pedro, Department of Electrical and Computer Engineering, Florida State University
 Abstract/Description

In this body of work, various energy storage devices have been modeled using phenomenological equivalent circuit modeling and impedance spectroscopy. Through this impedancebased modeling various electrochemical energy storage devices were modeled, providing accurate simulations of performance, as well as characterizing specific electrochemical processes and properties inherent in each system.
 Date Issued
 2014
 Identifier
 FSU_migr_etd8794
 Format
 Thesis
 Title
 Utilizing Ultracapacitor Energy Storage in Motor Drives with Cascaded Multilevel Converters.
 Creator

Azongha, Sardis, Li, Hui, Ordonez, Juan, Zheng, Jim P., Foo, Simon Y., Department of Electrical and Computer Engineering, Florida State University
 Abstract/Description

Ultracapacitors are increasingly becoming important in onboard energy storage applications in electric ship, and electric and hybrid electric vehicles where they provide peak power demands during acceleration and also absorb regenerative energy during breaking, thereby improving on power quality and reliability. While active research is continuously being pursued in the use of ultracapacitors as energy storage in motor drive applications, the topologies reported so far in literature have...
Show moreUltracapacitors are increasingly becoming important in onboard energy storage applications in electric ship, and electric and hybrid electric vehicles where they provide peak power demands during acceleration and also absorb regenerative energy during breaking, thereby improving on power quality and reliability. While active research is continuously being pursued in the use of ultracapacitors as energy storage in motor drive applications, the topologies reported so far in literature have drawbacks such as limited real power compensation with no reactive power compensation, reactive power compensation with no real power compensation, and the use of DCDC converters for interfacing, which have significant advantages in low to medium power applications, but degraded performance for high power applications such as in electric ship. Cascaded multilevel converters have been at the center of research for the past several years due to their inherent advantages in medium and high power applications, especially in motor drive applications. A cascaded multilevel converter is a power electronics device designed to synthesize a staircase AC voltage output from several DC sources. The advantages of cascaded multilevel converters include: (1) higher voltage levels can be obtained, thus eliminating the need for costly, bulky, and weighty transformers, (2) lower dv/dt leading to lower electromagnetic interference (EMI), (3) fundamental switching scheme resulting to lower switching losses, (4) lower harmonic distortion with increase in the number of DC voltage levels, thus leading to a lower requirement for output filter. The traditional cascaded multilevel converter interfaces DC energy sources. This research proposes two hybrid cascaded multilevel converter (HCMC) topologies and corresponding control strategies applied to motor drive, interfacing both dc sources and capacitor energy storage elements. In the first topology, the capacitor is controlled to provide reactive power to cancel lower order harmonics through a conditioning converter. The main converter supplied by a DC source can therefore be controlled to provide real power with reduced switching loss and improved efficiency and EMI. Analysis approach for the interaction between modulation index and displacement power factor has been developed to establish the capacitor charging and discharging conditions for induction machine load. A dynamic control strategy for energy storage elements is also developed. A major advantage of the proposed control method is the ability of the capacitor voltage to be successfully maintained at the desired value when the machine is in transient state, which is a key contribution. In the second proposed HCMC topology, the capacitor energy storage can be controlled not only to provide reactive power compensation to improve on power quality, but also to provide real power during acceleration, and absorb regenerative power during deceleration or braking period. Each phase of the proposed converter topology splits the supply of real power between a "main" converter supplied by a dc source, and two "auxiliary" converters supplied by energy storage elements. A hybrid modulation strategy combining sinusoidal pulse width modulation (SPWM) with phaseshift control is adopted for this topology. The motor drive control scheme is divided into three main parts: (1) Indirect or feedforward vector control of the induction motor to generate the output voltage reference, (2) power distribution control to split the supply of real power between the main and auxiliary converters, (3) voltage balancing control of energy storage elements, firstly to ensure that each capacitor voltage is regulated to the desired value, secondly to ensure voltage balance between all the capacitors in each cascaded converter phase or cluster, thirdly to ensure voltage balance between the three clusters of singlephase cascade converters, and lastly to obtain balanced ac output current by forcing the converter neutral point current to zero. The two multilevel converter topologies and their respective control strategies each have some inherent advantages that make them suitable for different motor drive applications. System level simulation results are provided to verify the proposed converter topologies and their corresponding control methods.
Show less  Date Issued
 2008
 Identifier
 FSU_migr_etd0270
 Format
 Thesis
 Title
 SingleStage GridInteractive Inverter for Distributed Energy and Integrated Storage with Enhanced Power Flow Control.
 Creator

Wu, Zhichao, Li, Hui, Ordóñez, Juan Carlos, Foo, Simon Y., MeyerBaese, Uwe H., Department of Electrical and Computer Engineering, Florida State University
 Abstract/Description

Nowadays, relatively smallscale distributed generation (DG) technologies are developing rapidly in an effort to both protect the environment and to address the bottleneck of centralized power systems. DG tends to utilize diverse renewable energy sources (RES) such as solar power, wind power, etc. which lessen the emission of greenhouse gases and other pollutants. Except for its islanded operation in some remote areas, DG tends to interconnect with existing utilities owing to benefits in...
Show moreNowadays, relatively smallscale distributed generation (DG) technologies are developing rapidly in an effort to both protect the environment and to address the bottleneck of centralized power systems. DG tends to utilize diverse renewable energy sources (RES) such as solar power, wind power, etc. which lessen the emission of greenhouse gases and other pollutants. Except for its islanded operation in some remote areas, DG tends to interconnect with existing utilities owing to benefits in supporting voltage, improving power quality, trading surplus power and serving as backup power. A gridinteractive inverter is crucial to any DG interconnection system, and there are two types of gridinteractive converters: those with energy storage (ES) and those without. Compared to those without ES, inverters with ES can achieve more flexible real/reactive power management and energy management. This allows them to tackle nondeterministic RES output, slow RES dynamics and fluctuating loads. And also this capability is significant as increasing numbers of DG units begin penetrating utilities. Generally speaking, today's gridinteractive inverters still need greater improvement in functionality, efficiency, cost, size and weight. This paper proposed a gridinteractive inverter for smallscale residential application consisting of one bulk converter and two conditioning converters in cascade that features single stage, multilevel structure, transformerless conversion, and integrated ES. Single stage offers a simpler configuration favorable to cost, efficiency and inverter reliability. Multilevel structure contributes its wellknown benefits in efficiency, power quality, device stress, EMI, etc. The transformerless conversion waives the need for dedicated high frequency (HF) and bulky line frequency (LF) transformers, which is advantageous to inverter efficiency, cost, size and weight. And integrated ES equips the inverter with flexible power and energy management functionality interacting with grid. Based on the proposed inverter for typical home application (3.5KW), circuit parameters are designed in detail especially for LCL filter. To design a control system and analyze system characteristics in gridconnected mode, dynamic average model (DAM) of the proposed inverter was derived in three forms: (1) equation sets in input side, inverter side and output side; (2) equivalent circuit; and (3) transfer function (TF) diagram. As detailed in this paper, ES (common capacitor or supercapacitor) interfaced with conditioning converters only supply reactive power, so the capacitor balance voltage control (CVBC) was developed to keep the auxiliary DC bus voltage constant. To track power flow accurately, high performance grid current control was achieved using a dual loop strategy. In the inner filter capacitor current feedback loop, proportional (P) regulator actively damps LCL filter resonance to gain sufficient stability margin. In the outer grid current feedback loop, proportional + resonant (PR) controller contributes to a nearzero steadystate error. A dedicated reactive power allocation (RPA) strategy was developed for the proposed inverter to supply wide range reactive power ranging from inductive rating to capacitive rating, which can mitigate grid voltage fluctuation, undervoltage and overvoltage, and also can adjust power factor to any expected value according to gridside demand. Combining controllable real power with wide range reactive power, the proposed inverter can broadly operate with pure real power, pure reactive power, and the mix of both. Phasor analysis was introduced to illustrate the principle of RPA. And to make RPA effective in wide power region, the proper reactive power allocation coefficient (RPAC) was theoretically derived to ensure unsaturated duty cycle in the bulk converter and conditioning converters. Accordingly, power area effective to RPA was analyzed with different RPAC selections. Five typical cases were analyzed to clarify this strategy. Cosimulation using PSIM plus Matlab/Simulink is executed to prove the viability of proposed technique. Besides, results from RTDS platform validate the performance of the whole scheme. Finally, a 3.5 KW prototype is built to verify the feasibility of proposed technology.
Show less  Date Issued
 2010
 Identifier
 FSU_migr_etd0692
 Format
 Thesis
 Title
 SmallSignal and Noise Temperature Modeling of Microwave Mesfets Using Artificial Neural Networks.
 Creator

Martinez, Hector Abel, Weatherspoon, Mark H., Foo, Simon Y., Arora, Rajendra, Department of Electrical and Computer Engineering, Florida State University
 Abstract/Description

This thesis presents a study of modeling of metal semiconductor field effect transistors (MESFETs) characteristics using artificial neural networks. A radial basis function artificial neural network (RBFANN) model is developed for scattering parameters and equivalent circuit parameters (ECPs), and a multilayer perceptron neural network (MLPANN) model is developed for incident available noise temperature parameters (TBs1B) of MESFETs. The training and testing data for these models is...
Show moreThis thesis presents a study of modeling of metal semiconductor field effect transistors (MESFETs) characteristics using artificial neural networks. A radial basis function artificial neural network (RBFANN) model is developed for scattering parameters and equivalent circuit parameters (ECPs), and a multilayer perceptron neural network (MLPANN) model is developed for incident available noise temperature parameters (TBs1B) of MESFETs. The training and testing data for these models is obtained from measured twoport scattering parameters, extracted ECPs, and measured TBs1B of a 4x50µm gate width, 0.25µm gate length gallium arsenide (GaAs) MESFET. A fourinput, eightoutput ANN is used to model the Sparameters of a microwave MESFET versus bias, temperature, and frequency; a threeinput, eightoutput ANN is used to model the ECPs of a microwave MESFET versus bias and temperature; and a twoinput, oneoutput ANN is used to model the TBs1B of a microwave MESFET versus load reflection coefficients and load impedances. Comparisons of measured and modeled data are presented and the results show very good agreement. The average relative errors using the RBFANN models for the Sparameters and ECPs were 0.81% and 0.77% respectively. The results of the Sparameters and ECPs represent about 60% reduction in error when compared to Backpropagation ANN models of similar parameters of the same device. The incident available noise temperature model is a novel study and results are in very good agreement with the measured data with the best average relative errors of 0.0008% obtained for TBs1B versus load impedance Backpropagation ANN.
Show less  Date Issued
 2005
 Identifier
 FSU_migr_etd2690
 Format
 Thesis
 Title
 Novel High Energy Density LiIon Capacitors.
 Creator

Cao, Wanjun, Zheng, Jim P., Shih, Chiang, Li, Hui, Foo, Simon Y., Andrei, Petru, Department of Electrical and Computer Engineering, Florida State University
 Abstract/Description

The energy density of conventional electric doublelayer capacitors is about 67 Wh/kg and due to the limited specific capacitance and cell voltage, and a large amount of electrolyte which is required to build a layer of charge of the doublelayer. The energy density theory guide clearly shows that the energy density of doublelayer capacitors is ultimately limited by how many ions are available in the electrolyte or the salt concentration in the electrolyte.We demonstrate a lithium capacitor...
Show moreThe energy density of conventional electric doublelayer capacitors is about 67 Wh/kg and due to the limited specific capacitance and cell voltage, and a large amount of electrolyte which is required to build a layer of charge of the doublelayer. The energy density theory guide clearly shows that the energy density of doublelayer capacitors is ultimately limited by how many ions are available in the electrolyte or the salt concentration in the electrolyte.We demonstrate a lithium capacitor which is capable of achieving high energy density over 20 Wh/kg, long cycle life and high power density. The lithium capacitor consists of a battery electrode with lithium intercalated hard carbon anode and a doublelayer activated carbon cathode electrode with the opencircuit potential at or near the maximum potential when the cell is fully charged. The stabilized lithium metal powder was applied onto the surface of prefabricated hard carbon anode electrodes.
Show less  Date Issued
 2013
 Identifier
 FSU_migr_etd7742
 Format
 Thesis
 Title
 Application of an Intelligent Tuning Algorithm for ThreeLevel NPC Rectifier for Shipboard Power Distribution.
 Creator

Liu, Yusi, Edrington, Chris S., Foo, Simon Y., Weatherspoon, Mark H., Department of Electrical and Computer Engineering, Florida State University
 Abstract/Description

The demand for highvoltage and highpower power electronics devices, especially for the next generation electrical ship system, has increased rapidly these years. The threephase threelevel neutral point clamped (NPC) rectifier attracts more and more engineers' attention due to it has many advantages: sinusoidal input current which contains low harmonics, unity power factor, bidirectional power flow, low voltage and switching loss for each switch and so on. It could potentially provide DC...
Show moreThe demand for highvoltage and highpower power electronics devices, especially for the next generation electrical ship system, has increased rapidly these years. The threephase threelevel neutral point clamped (NPC) rectifier attracts more and more engineers' attention due to it has many advantages: sinusoidal input current which contains low harmonics, unity power factor, bidirectional power flow, low voltage and switching loss for each switch and so on. It could potentially provide DC power to medium voltage DC distribution system on ships. A NPC rectifier system is introduced in this thesis and the hardware test bed for validating is built successfully. Base on the topology of NPC rectifier, the PWM math model in ABC stationary frame is set up first. In order to obtain constant control variables as in DC motor control, the NPC rectifier PWM math model in DQ0 reference frame is built. And then for design the control loop, the NPC rectifier average models are developed in both ABC stationary frame and DQ0 reference frame. Threelevel SVM is used for achieving sinusoidal input current, lower current THD and lower switching loss. Neutral point voltage balance problem is an inherent problem of threelevel PWM rectifier. Without neutral point voltage control, the harmonic components of input current will greatly increase, and the DClink capacitors and the switching devices may probably be destroyed. The influences of every switching state on neutralpoint are analyzed and the smallvector is actively utilized to solve the neutral point balance problem. When to design the PI controller gains, the classic Nichols and Ziegler rules and the NPC system responses to this tuning algorithm are showed firstly. Further optimization for the system PI controller gains, which base on Particle Swarm Optimization (PSO), is used and the system responses are compared to the classic Nichols and Ziegler rules'. Hardware data validate the improvement of PSO contributes to the NPC system. A NPC rectifier realtime Controllerhardwareintheloop (CHIL) test is completed before the real hardware experiment since it could derisk the controller for hardware experiment. The realtime simulation is compared to the hardware experiment, the CHIL methodology is approved.
Show less  Date Issued
 2011
 Identifier
 FSU_migr_etd1103
 Format
 Thesis