Engineering Commons^™

Differential-Algebraic Approach To Speed And Parameter Estimation Of The Induction Motor, Mengwei Li

Doctoral Dissertations

This thesis considers a differential-algebraic approach to estimating the speed and rotor time constant of an induction motor using only the measured terminal voltages and currents. It is shown that the induction motor speed satisfies both a second-order and a third-order polynomial equation whose coefficients depend the stator voltages, stator currents, and their derivatives. Further, it is shown that as long as the stator electrical frequency is nonzero, the speed is uniquely determined by these polynomials. The speed so determined is then used to stabilize a dynamic (Luenberger type) observer to obtain a smoothed speed estimate. With full knowledge of …

A Methodology For Solving The Equations Arising In Nonlinear Parameter Identification Problems: Application To Induction Machines, Kaiyu Wang

Doctoral Dissertations

This dissertation presents a method that can be used to identify the parameters of a class of systems whose regressor models are nonlinear in the parameters. The technique is based on classical elimination theory, and it guarantees that the solution for the parameters which minimize a least-squares criterion can be found in a finite number of steps. The proposed methodology begins with an input-output linear overparameterized model whose parameters are rationally related. After making appropriate substitutions that account for the overparameterization, the problem is transformed into a nonlinear least-squares problem that is not overparameterized. The extrema equations are computed, and …

Design And Development Of Poly -(3 -Hexylthiophene) Field Effect Transistors, Fengliang Xue

Doctoral Dissertations

Organic field effect transistors (OFETs) with poly(3-hexylthiophene) (P3HT) as the active layer are developed and studied. The device characteristics are significantly affected by source/drain contact resistance, and P3HT-SiO 2 interface and the traps. These results are verified by the numerical device simulations. The temperature dependence of device mobility is studied, which indicates that the carrier transport is either heat-assisted or heat-limited at different temperature ranges. The on/off ratio and threshold voltage are found to be dependent on the temperature. Hysteresis effect due to gate electric stress is investigated. The silanol groups present at the SiO2 surface are thought to be …

Low-Voltage Analog Circuit Design Using The Adaptively Biased Body-Driven Circuit Technique, Stephen Christopher Terry

Doctoral Dissertations

The scaling of MOSFET dimensions and power supply voltage, in conjunction with an increase in system- and circuit-level performance requirements, are the most important factors driving the development of new technologies and design techniques for analog and mixed-signal integrated circuits. Though scaling has been a fact of life for analog circuit designers for many years, the approaching 1-V and sub-1-V power supplies, combined with applications that have increasingly divergent technology requirements, means that the analog and mixed-signal IC designs of the future will probably look quite different from those of the past. Foremost among the challenges that analog designers will …

Study On Poly[2-Methoxy-5-(2'-Ethylhexyloxy)-1,4-Phenylenevinylene] Polymer Based Photodetectors, Difei Qi

Doctoral Dissertations

This thesis is dedicated to the development of novel and efficient polymer photodetectors based on MEH-PPV conjugated polymers. The polymer-based photodetectors have the advantages of easy processing, low weight, and low cost, and thus are promising candidates for future generations of photodetectors. At present, the quantum efficiency of polymer photodetectors is still low and not comparable to inorganic photodetectors. Therefore, in this thesis we explore ways to enhance the quantum efficiency of polymer photodetectors by using different electron donors, configurations, and implementation of the diffraction optical grating into photodetector structure. We designed, fabricated, and characterized several original types of devices: …

Dna-Templated Assembly Of Metallic Nanowires, Qun Gu

Doctoral Dissertations

Nanowires are widely recognized as key elements in the development of futuristic nanoscale devices of nanoelectronics, optoelectronics and nano-electro-mechanic systems. Lithographic fabrication, however, faces increasing difficulties in the realization of continuously miniaturized features. The “Bottom-up” approach is a promising successor to lithography for fabrication of nanostructures. DNA is a natural template for nanowire assembly. The linear polynucleotide chain has a width of 2 nm and a length of 0.34 run per nucleoside subunit.

One-dimensional magnetic Co and Ni nanoparticles have been assembled in-situ for the first time by use of single DNA molecules as templates. Target metallic nanowires that are …

Coupling Analysis, Simulation, And Experimentation In Natural And Engineered Biological Systems At The Molecular Scale, Derek W. Austin

Doctoral Dissertations

Cellular functions are controlled by genetic regulatory networks called gene circuits. Recently, there has been much interest in how gene circuits deal with or even exploit stochastic fluctuations in molecular species within the cellular environment. Through a coupling of analysis and simulation with experimentation, this dissertation work furthers the understanding of gene circuit noise behavior and makes significant contributions to the analytical and experimental tools that are currently available for the study and design of natural and synthetic gene circuits. In this study, models are developed for unregulated and autoregulated gene circuits. Results from the analysis are compared to computer …

Energy Efficient Designs For Collaborative Signal And Information Processing Inwireless Sensor Networks, Yingyue Xu

Doctoral Dissertations

Collaborative signal and information processing (CSIP) plays an important role in the deployment of wireless sensor networks. Since each sensor has limited computing capability, constrained power usage, and limited sensing range, collaboration among sensor nodes is important in order to compensate for each other’s limitation as well as to improve the degree of fault tolerance. In order to support the execution of CSIP algorithms, distributed computing paradigm and clustering protocols, are needed, which are the major concentrations of this dissertation.

In order to facilitate collaboration among sensor nodes, we present a mobile-agent computing paradigm, where instead of each sensor node …

Multimodal Three Dimensional Scene Reconstruction, The Gaussian Fields Framework, Fayçal Boughorbel

Doctoral Dissertations

The focus of this research is on building 3D representations of real world scenes and objects using different imaging sensors. Primarily range acquisition devices (such as laser scanners and stereo systems) that allow the recovery of 3D geometry, and multi-spectral image sequences including visual and thermal IR images that provide additional scene characteristics. The crucial technical challenge that we addressed is the automatic point-sets registration task. In this context our main contribution is the development of an optimization-based method at the core of which lies a unified criterion that solves simultaneously for the dense point correspondence and transformation recovery problems. …

Active Harmonic Elimination In Multilevel Converters, Zhong Du

Doctoral Dissertations

The modulation technique for multilevel converters is a key issue for multilevel converter control. The traditional pulse width modulation (PWM), space vector PWM, and space vector control methods do not completely eliminate specified harmonics. In addition, space vector PWM and space vector control method cannot be applied to multilevel converters with unequal DC voltages. The carrier phase shifting method for traditional PWM method also requires equal DC voltages. The number of harmonics that can be eliminated by the selective harmonic elimination method is restricted by the number of unknowns in the harmonic equations and available solutions.

For these reasons, this …

Mosfet Modeling, Simulation And Parameter Extraction In 4h- And 6h- Silicon Carbide, Md Hasanuzzaman

Doctoral Dissertations

This thesis presents the work on analytical modeling and simulation of a silicon carbide (SiC) power MOSFET, model verification with test data, and device characterization and parameter extraction of the SPICE model. The development of temperature models for a lateral as well as a vertical MOSFET in SiC are also presented.

The model takes into account the various short channel effects in the DIMOS channel region as well as the velocity saturation effect in the drift region. Considering the SiC material processing limitations and feedback from the system level application group, an application specific SiC power MOSFET structure has been …

Load Balancing In Parallel And Distributed Databases, Zhong Tang

Doctoral Dissertations

This dissertation addresses the load balancing problem for parallel computations in the presence of time delays from a control system design perspective. Extensive experiments in a parallel computing environment have been made to evaluate load balancing strategies, and have driven the continued evolution of the parallel computation model and the load balancing strategies.

The critical feature of the load balancing problem is the delayed receipt of information and transferred load. In this work, load balancing in a parallel computer architecture is first modeled as a deterministic time-delay system with saturations. Three essential properties of the load balancing strategy, including consistency, …

Biosensing With Microcantilever-Based Sensors, Xiaodong Yan

Doctoral Dissertations

Microcantilevers provide an ideal platform for biosensors. The micron-sized transducer brings several advantages, such as high sensitivity, small sample quantity for analysis, portability, implantable sensor devices, and the ability to be mass produced and integrated into standard microelectronic processing technologies like complementary metal oxide seminconductors (CMOS).

The objective of this research is to investigate and develop modification methods of microcanitlevers for biosensing applications.

Two microcantilever modification methods were investigated. They are self-assembly monolayer method and layer-by-layer method. A fundamental procedure for modification of microcantilevers using the layer-by-layer approach was developed for the first time in this research. These modification methods …

Intelligent Control Of Nonlinear Systems With Actuator Saturation Using Neural Networks, Wenzhi Gao

Doctoral Dissertations

Common actuator nonlinearities such as saturation, deadzone, backlash, and hysteresis are unavoidable in practical industrial control systems, such as computer numerical control (CNC) machines, xy-positioning tables, robot manipulators, overhead crane mechanisms, and more. When the actuator nonlinearities exist in control systems, they may exhibit relatively large steady-state tracking error or even oscillations, cause the closed-loop system instability, and degrade the overall system performance. Proportional-derivative (PD) controller has observed limit cycles if the actuator nonlinearity is not compensated well. The problems are particularly exacerbated when the required accuracy is high, as in micropositioning devices. Due to the non-analytic nature of the …

Cad Model Extraction Of Pcb Signal Discontinuity Using A Circuit Extraction Approach Based On Mixed-Potential Integral Equation Formulation, Shaofeng Luan

Doctoral Dissertations

"In high-speed digital design, signal via transitions on printed circuit boards (PCBs) are becoming an important signal integrity issue. Efficient and accurate models for via transitions are necessary to analyze high bit-rate digital circuit system. The circuit extraction approach based on a mixed-potential integral equation formulation (CEMPIE) is an extension of the Partial Element Equivalent Circuit approach (PEEC) to general multi-layered media. CEMPIE was further developed to include the horizontal current components on the vertical surface and extended to model the discontinuities on multilayer PCBs. A procedure of building SPICE models for signal via transitions between printed circuit board layers …