<p> Rapid developments in the communications field have created a rising demand for low power, high speed, and low weight communication devices. The current project presents the development of a Viterbi decoder on a chip with a reduced dynamic power consumption, achieved by using an asynchronous design, which is data driven and active only when needed. The Xpower analyzer tool is used to measure the dynamic power on the designed chip, from which it is seen that the proposed design greatly improves power consumption. The results also show that there is a trade-off between dynamic power reduction, larger chip area, and reduced speed. </p>

<p> This research introduces two new methodologies to design a set of controllers such that every controller in the set preserves closed-loop stability of a given multi variable plant under prescribed loop failures. The proposed approaches differ from existing techniques in two ways: First, these methods are strictly based on frequency response data of the plant that can be easily measured by experiments. No mathematical models or system identification processes are used. Second, while most control design methods find one controller, the proposed methods design a set of controllers satisfying the control objective. Two approaches are presented with examples illustrating the controller design. Integrity test results of the designed controllers under pre-specified loop failures are also presented.</p>

<p>Current state of the art techniques for landmine detection in ground penetrating radar (GPR) utilize statistical methods to identify characteristics of a landmine response. This research makes use of 2-D slices of data in which subsurface landmine responses have hyperbolic shapes. Various methods from the field of visual image processing are adapted to the 2-D GPR data, producing superior landmine detection results. This research goes on to develop a physics-based GPR augmentation method motivated by current advances in visual object detection. This GPR specific augmentation is used to mitigate issues caused by insufficient training sets. This work shows that augmentation improves detection performance under training conditions that are normally very difficult. Finally, this work introduces the use of convolutional neural networks as a method to learn feature extraction parameters. These learned convolutional features outperform hand-designed features in GPR detection tasks. This work presents a number of methods, both borrowed from and motivated by the substantial work in visual image processing. The methods developed and presented in this work show an improvement in overall detection performance and introduce a method to improve the robustness of statistical classification.</p> / Dissertation

<p>While molecular and cellular processes are often modeled as stochastic processes, such as Brownian motion, chemical reaction networks and gene regulatory networks, there are few attempts to program a molecular-scale process to physically implement stochastic processes. DNA has been used as a substrate for programming molecular interactions, but its applications are restricted to deterministic functions and unfavorable properties such as slow processing, thermal annealing, aqueous solvents and difficult readout limit them to proof-of-concept purposes. To date, whether there exists a molecular process that can be programmed to implement stochastic processes for practical applications remains unknown. </p><p>In this dissertation, a fully specified Resonance Energy Transfer (RET) network between chromophores is accurately fabricated via DNA self-assembly, and the exciton dynamics in the RET network physically implement a stochastic process, specifically a continuous-time Markov chain (CTMC), which has a direct mapping to the physical geometry of the chromophore network. Excited by a light source, a RET network generates random samples in the temporal domain in the form of fluorescence photons which can be detected by a photon detector. The intrinsic sampling distribution of a RET network is derived as a phase-type distribution configured by its CTMC model. The conclusion is that the exciton dynamics in a RET network implement a general and important class of stochastic processes that can be directly and accurately programmed and used for practical applications of photonics and optoelectronics. Different approaches to using RET networks exist with vast potential applications. As an entropy source that can directly generate samples from virtually arbitrary distributions, RET networks can benefit applications that rely on generating random samples such as 1) fluorescent taggants and 2) stochastic computing.</p><p>By using RET networks between chromophores to implement fluorescent taggants with temporally coded signatures, the taggant design is not constrained by resolvable dyes and has a significantly larger coding capacity than spectrally or lifetime coded fluorescent taggants. Meanwhile, the taggant detection process becomes highly efficient, and the Maximum Likelihood Estimation (MLE) based taggant identification guarantees high accuracy even with only a few hundred detected photons.</p><p>Meanwhile, RET-based sampling units (RSU) can be constructed to accelerate probabilistic algorithms for wide applications in machine learning and data analytics. Because probabilistic algorithms often rely on iteratively sampling from parameterized distributions, they can be inefficient in practice on the deterministic hardware traditional computers use, especially for high-dimensional and complex problems. As an efficient universal sampling unit, the proposed RSU can be integrated into a processor / GPU as specialized functional units or organized as a discrete accelerator to bring substantial speedups and power savings.</p> / Dissertation

Cyber-physical systems are complex engineering systems that integrate computational, communication, and control components with physical components in many applications such as automotive systems, aeronautical systems, industrial process control systems, electrical power grids, and environmental monitoring systems. As the cyber components increase in both number and complexity, technical challenges arise for their integration with the physical domain. As the field of cyber-physical systems continues to grow and evolve, problems emerge from the interaction of heterogeneous domains, hybrid dynamics, and nonlinearities which significantly hamper the system integration. Consequently, rigorous engineering methods are needed for the integration of cyber and physical components in order to achieve predictable, correct behavior. This dissertation presents a model-based design framework based on port-Hamiltonian systems and passivity in order to address the challenges mentioned above. The contributions are threefold: (1) A domain-specific modeling language, (2) a compositional model-based control design method, and (2) a formal safety analysis method for multi-modal port Hamiltonian systems. The Port-Hamiltonian Systems Modeling Language uses the structure of port-Hamiltonian systems to model cyber-physical systems with nonlinearities, hybrid dynamics, and heterogeneous domains in a component-based way. The compositional model-based control design method uses passivity-based methods to ensure stability properties of the overall system in the presence of implementation uncertainties. The safety analysis method utilizes the Hamiltonian function as a barrier function to prevent system trajectories from ending in unsafe regions of the state space. The theoretical contributions are evaluated and validated with an in-depth case study of automotive control software for an autonomous vehicle using a hardware-in-the-loop simulation platform.

There has been a growing interest in electrochemical storage devices such as batteries, fuel cells and supercapacitors in recent years. This interest is due to our increasing dependence on portable electronic devices and on the high demand for energy storage from the electric transport vehicles and electrical power grid industries. As we transition towards cleaner renewable fuel sources such as solar, wind, tidal, etc. our dependence on energy storage devices will continue to grow. Li-air offers much higher energy density than all other batteries based on electrochemical storage. However, these batteries currently suffer from a number of issues such as a low cyclability and a reduced practical energy density compared to the theoretical energy density. The deposition of lithium peroxide on the surface of the cathode is one of the main causes for the low practical specific capacity of lithium-air batteries with organic electrolyte. Electrochemical impedance spectroscopy (EIS) has been used in the past to extract physical parameters such as chemical diffusion coefficient, effective diffusion coefficient, Faradaic reaction rate, degradation and stability of an electrochemical device. In this dissertation, a physics based analytical model is developed to study the EIS of Li-air batteries, in which the mass transport inside the cathode is limited by oxygen diffusion, during charge and discharge. The model takes into consideration the effects of double layer, Faradaic processes, and oxygen diffusion in the cathode, but neglects the effects of anode, separator, conductivity of the deposit layer, and Li-ion transport. The analytical model predicts that the effects of Faradaic impedance can be hidden by the double layer capacitance. Therefore, the dissertation focuses separately on two cases: 1) the case when the Faradaic process and the double layer capacitance are separate and can be observed as two different semicircles on the Nyquist plot and 2) the case when the Faradaic process is shadowed by the double layer capacitance and shows up as only one large semicircle on the Nyquist plot. A simple expression is developed to extract physical parameters such as the values of the diffusion coefficient of oxygen and Faradaic reaction rate from experimental impedance spectrum for each of the two cases. The diffusion coefficient can be determined by using the resistances (real impedance intercept on the Nyquist plot) of both the semicircles for the first case and by using the combined resistance for the second case. Once, the effective oxygen diffusion coefficient is estimated, it can be used to estimate the value of the reaction constant. This method of extracting the values of the diffusion coefficient and reaction constant can serve as a tool in identifying an effective electrolyte or cathode material. It can also serve as a noninvasive technique to identify and also quantify the use of the catalyst to improve the reaction kinetics in an electrochemical system. Finally, finite element simulations are used to validate the analytical models and to study the effects of discharge products on the impedance spectra of Li-air batteries with organic electrolyte. The finite element simulations are based on the theory of concentrated solutions and the complex impedance spectra are computed by linearizing the partial differential equations that describe the mass and charge transport in Li-air batteries. These equations include the oxygen diffusion equation, the Li drift-diffusion equation, and the electron conduction equation. The reaction at the anode and cathode are described by Butler-Volmer kinetics. The total impedance of a Li-air battery increases by more than 200% when the response is measured near the end of the discharge cycle as compared to on a fresh battery. The resistivity of the deposition layer significantly affects the deposition profile and the total impedance. Using electrolytes with high oxygen solubility and concentrated O2 gas at high pressures will reduce the total impedance of Li-air batteries. / A Dissertation submitted to the Department of Electrical and Computer Engineering in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Fall Semester 2015. / August 26, 2015. / analytical modeling, diffusion impedance, EIS, impedance spectroscopy, Li-air / Includes bibliographical references. / Petru Andrei, Professor Directing Dissertation; Joseph B. Schlenoff, University Representative; Jim P. Zheng, Committee Member; Pedro Moss, Committee Member; Hui Li, Committee Member.

The Navy has proposed to use a shipboard power system operating at medium voltage direct current to distribute power for their all-electric ship. The power is generated by electric machines as alternating current and requires power electronic rectifiers to output direct current. Power electronics converters are needed to convert the direct current to alternating current for ship propulsion and service loads. An increase in the use of fast switching power electronics is expected in future ships. The increased voltage rise time on switches is known to produce unwanted high frequencies with corresponding wavelengths of the same order of magnitude as the length of the ship hull. These high frequency transients can cause the ship system to couple with the surrounding ship hull causing adverse effects. The amount of high frequency content and the impact it has on the ship system performance is difficult to calculate with current models. Increased voltage and performance requirements for power electronics has led to advancements in switching frequencies into the 10s to 100s of kilohertz and increased voltage edge rates. The faster switching corresponds to higher frequency responses from the shipboard power system. Research has shown that high frequency content in electrical power systems is responsible for parasitic coupling and ultimately damage to the equipment. Electric machines, for instance, have increased winding and iron losses, overvoltages at the terminals, and even bearing currents via shaft voltages. The Navy is interested in simulating ship systems to test their electromagnetic compatibility before implementing or committing to a specific design. There are numerous techniques used to acquire machine parameters that have been proven to be useful in modeling electric machine behavior. The approaches were considered by the amount of proprietary information needed to acquire accurate results, the complexity of the modeling methods, and the overall time it takes for implementation. A majority of system simulations gravitate towards simple solutions for machine behavior which require assumptions to be made that deviate from the actual machine behavior. Exact inner dimensions, winding layouts, end winding dimensions, insulation thickness, and other information are proprietary and often not accurate representations of the physical machine once built. It is time consuming to obtain an accurate working model when assumptions are made or when detailed computer aided design models are needed to calculate machine response quantities. The research modeling approach put forth in this paper is not aimed at capturing the steady-state behavior of the machine. It is shown that a detailed understanding of the motor may not be necessary to accurately model the high frequency effects. It is the transient behavior at non-operating frequencies that need to be modeled correctly to develop new models of shipboard power systems for grounding research. The frequency dependent information is most useful to determine frequencies of interest that other modeling techniques are less likely to capture and point out. Previously suggested measurement techniques have been considered useful in determining parameters of machines but are not always accurately implemented without in-depth knowledge of the motor that may be proprietary. Lumped-parameter models are based on extracting information at transitional frequencies or looking at the slope of a variable over a frequency range. These models tend to be over simplified representations of the component by averaging the parameters for given ranges. In reality a machine's impedance varies with all frequencies. Lumped parameter based models typically over simplify the grounding behavior of the machine by not varying the impedance as a function of frequency. The technique used in this research is based on scattering parameters, a way of determining the terminal behavior of the machine without the knowledge of the actual inner workings of the machine. The inverse scattering technique uses steady-state stimuli to calculate reflection and transmission coefficients of system components allowing the device to be considered as a black box. This can be understood as electrical snapshots of how the machine would respond when subjected to a range of spectral content. The approach could have a significant impact on the modeling of ground interactions with machines. The machine can now be measured and characterized with no prior knowledge of the machine. The measurements are placed in simulation software in the typical measurement configurations used in other approaches to extract parametric data. It was discovered that these different configuration setups could now be measured in software without the need to physically reconfigure the machine's wiring for each measurement. This modeling approach was coined 'virtual measurement modeling.' To the best of the author's knowledge there are not any known techniques for fast model prototyping of electric machines which cover a broad range of frequencies with high accuracy. This thesis will present a possible solution for consideration in future models developed for grounding studies. This approach outlines a promising technique that can be easily implemented with high accuracy and reproducibility. The technique was derived from inverse scattering theory and was implemented on electric machines for characterizing high frequency behaviors. / A Thesis submitted to the Department of Electrical & Computer Engineering in partial fulfillment of the requirements for the degree of Master of Science. / Fall Semester 2015. / August 3, 2015. / Electric Machines, Electromagnetic Interference, High Frequency, Scattering Parameters, Shipboard Power System, Transient / Includes bibliographical references. / Chris S. Edrington, Professor Directing Thesis; Lukas Graber, Committee Member; Mischa Steurer, Committee Member.

Lithium batteries have played an important role since early 1980’s to provide us with energy for small portable devices. Due to the increasing demand and limited availability of fossil fuels there is a need to shift to renewable energy. In this thesis, the fabrication procedure for the lithium ion coin cell is extensively analyzed. A brief introduction into the lithium ion battery is discussed, the physics and chemistry of the materials is explained. Emphasis is made on the importance of calendaring an electrode. LiFePO4 was mixed with the Super P, PVDF and NMP at appropriate stoichiometric amounts and half coin cells were produced with the reference electrode as lithium foil. The effects of calendaring in terms of discharge capacity, density profile and ac impedance was analyzed. The resulting material sample were analyzed in two parts, Sample A was left as is and Sample B was calendared. The calendared electrode exhibited a lower impedance when observed with the impedance test. The calendared electrode exhibited a higher discharge capacity of about 162 mAh/g at C/10 rate when compared to the uncalendared electrode with a discharge capacity of about 152 mAh/g at C/10. The experimental results were than compared to the simulated model constructed in Comsol Multiphysics. The coin cell model in COMSOL was started with use of the existing model for cylindrical cells. The parameters and equations required for the setup were analyzed and discussed. The comparison of the experimental vs simulated results yielded some preliminary information. However, this work is still in progress, for building further models with different materials for the coin cells. / A Thesis submitted to the Department of Electrical and Computer Engineering in partial fulfillment of the Master of Science. / Summer Semester 2017. / July 17, 2017. / Includes bibliographical references. / Pedro L. Moss, Professor Directing Thesis; Mark H. Weatherspoon, Committee Member; Petru Andrei, Committee Member.

Medium Voltage DC (MVDC) system is becoming a captivating alternative for designing All Electric Ship (AES) for the US Navy. Modular Multilevel Converter (MMC) is considered as an essential component of MVDC systems for its scalability and efficacy. Designing such a power electronic converter for an electric ship is a challenging task in terms of volume constraints in an electric ship.Preliminary naval ship design used point based spiral design techniques, but the complexity and some disadvantages of such design techniques don’t necessarily produce the most feasible cost effective design. To overcome the issue, the US Navy is exploring the application of Set Based Design(SBD) for designing naval architecture through Smart Ship System Design (S3D) to aid the early stage ship design.This thesis explores the areas of SBD to have a better understanding and knowledge of the design techniques. This is accomplished by design exercise employing SBD to design an essential component of the MVDC breaker-less architecture which is Modular Multilevel Converter. The effort begins with investigating the scaling factors for MMC and apply them to estimate the power density of the converter through exploration of SBD.The outcome of this work is expected to aid early stage ship design exercises using S3D which will enable a guideline for applying SBD concepts to integrate into ship system design. / A Thesis submitted to the Department of Electrical and Computer Engineering in partial fulfillment of the requirements for the degree of Master of Science. / Summer Semester 2017. / July 14, 2017. / MMC, MVDC system, Quality function deployment, Scaling factors, Set Based Design, Taguchi method / Includes bibliographical references. / Md Omar Faruque, Professor Directing Thesis; Simon Y. Foo, Committee Member; Shonda Bernadin, Committee Member; Ruturaj Soman, Committee Member.

Grid codes impose immunity requirements to the generation systems that are connected to the transmission lines. Immunity refers to the generator’s capability to overcome grid abnormal conditions. One of the requirements is to remain connected during a certain time when a fault, like voltage sag, is presented. During the fault scenario, a generator unit should remain connected for a pre-determined amount of time, and also provide reactive power to support the grid voltage. This is called low-voltage ride through (LVRT). Initially, LVRT requirements were imposed for large generator units like wind farms connected to the transmission network; however, due to the increased penetration of distributed generation (DG) on the distribution system, new grid codes extend the mentioned capability to generator units connected to the distribution grid. Due to matured photovoltaic (PV) technology and the decreased price of PV panels, PV grid tied installations are proliferating in the utility grids; this is creating new challenges related to voltage control. In the past, DG such as PV were allowed to trip from the grid when a fault or unbalance occurred and reconnect within several seconds (sometimes minutes) once the fault had been cleared. Nevertheless, thanks to high PV penetration nowadays, the same method cannot be used because it will further deteriorate the power quality and potentially end in a power blackout. Different approaches have been considered to fulfill the LVRT requirement on PV systems. A large amount of literature focuses on the control of the grid side converter of the PV installation rather than the control of PV operation during the fault, and most control designs applied to the grid side follow classical control methods. Moreover, the effects of the grid fault on the generator side impose a challenge for controlling the PV systems since the quality of the synthesized converter voltages and currents depends on the dc link power/voltage control. This document proposes a Model based Predictive Control (MPC) for controlling a two stage PV system to fulfill LVRT requirements. MPC offers important advantages over traditional linear control strategies since the MPC cost function can include constraints that are difficult to achieve in classical control. Special attention is given to implementation of the proposed control algorithms. Simplified MPC algorithms that do not compromise the converter performance and immunity requirement are discussed. / A Dissertation submitted to the Department of Electrical and Computer Engineering in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Summer Semester 2017. / July 21, 2017. / LVRT, MPC, Photovoltaic, Renewable Energies, Voltage support / Includes bibliographical references. / Chris S. Edrington, Professor Directing Dissertation; Juan Ordonez, University Representative; Omar Faruque, Committee Member; Simon Y. Foo, Committee Member.