Electrical & Computer Engineering Masters Theses

Permanent URI for this collectionhdl:10365/32560

Browse

Now showing 1 - 20 of 84

A Precision Slip Frequency Detector
(North Dakota State University, 1957) Horvik, Eivind
The problem of measuring low values of slip of induction machines is present in most Electrical Engineering laboratories. A rather high accuracy of the determination is necessary for theoretical calculations of motor loading, using equivalent circuit techniques. Conventional methods of determining slip fail to give high accuracy at low values of slip. This thesis presents a solution to this problem by describing the design and construction of a precision slip frequency detector of nominal cost. The principle employed is that of beat frequency comparison of the rotor shaft speed against line frequency. The output of the beat frequency detector actuates a multivibrator-differentiating circuit, the output of which triggers an electro-mechanical counter. A photoelectric pickup device for determining shaft speed is also discussed.
Impedances of a Cubical Quad Antenna
(North Dakota State University, 1965) Choong, Tsi-lung
Rectangular loop antennas and short electric dipoles are two of the oldest antennas in existence. In 1888, twenty years after Maxwell invented his famous Maxwell's equations, Hertz used these two antennas to prove that high frequency electric energy sources could radiate electro- magnetic waves. The "Cubical Quad" or, simply, "Quad" antenna is a development of the rectangular loop antenna. It consists of a pair of square loops, one-quarter wavelength on a side or one wavelength around the periphery; one loop being driven and the other used as a parasitic reflector. The separation between the two is usually of the order of 0.15 to 0.2 wavelength, with the planes of the loops parallel. While studying the properties of this antenna, it was discovered that little had been done to develop it from a theoretical aspect. The purpose of this thesis is to obtain values of the self and mutual impedances existing in such an antenna array. The values are obtained from mathematical analysis and experimental measurements and may be used in field pattern and gain calculations.
Dc'sign of Piezoelectric Energy Harvesting and Supercnpacitor Charging Circuits Using Optimized Duty-Cycle of Buck Converter
(North Dakota State University, 2009) Zhao, Zhou
Energy harvesting has been proved to be an innovative solution to replace the batteries in remote power supply applications. Unfortunately, the limited capacity aucl low efficiency of power conversion restrict the practical applications of energy harvesting in daily-life. After a systematic review of research on energy harvesting iu power management perspective, a circuit design, which targets low-frequency mechanical vibrations, is presented. With the classical piezoelectric cantilever setup, the maximum charging current of a supercapacitor can be obtained by optimizing the duty-cycle of a buck converter through software implemented pulse width modulation. The results of experiments prove the capacitive electric model of the piezoelectric element, the existence of maximum charging current of the supercapacitor, and the adaptive control of the designed circuits. With the duty-cycle optimized to 2.17%, a maximum charging current of 17.36 mA is measured, which is approximately 4 times that obtained in related researches. An active radio frequency identification (RFID) application is proposed to utilize the harvested power of 67.2 µW. In addition, the digital design in field programmable gate array (FPGA) is integrated using AMIS 0.5 µrn CMOS process technology to reduce system power dissipation.
Refinementbased Verification of Elastic Pipelined System with Early Evaluation
(North Dakota State University, 2010) Cai, Yangwei
This thesis presents a formal verification procedure to check correctness of the synchronous elastic pipelined system that incorporates early evaluation against its synchronous parent system. Note that the goal of the verification procedure is not to establish the correctness of the algorithm for synthesizing elastic circuits, but instead, to find bugs and formally prove the correctness of elasticized designs with early evaluation. Dataflow through elastic architectures is complicated by the insertion of any number of elastic buffers in any place in the design. Elastic token-flow diagrams are introduced, which are used to track the flow of data in elastic architectures. We provide a method to construct such diagrams. The thesis also develops a highly automated and systematic procedure based on elastic token-flow diagrams that compute functions that map states of elastic systems to states of the synchronous parent systems. Such functions, known as refinement maps, are used to compare behaviors of elastic and synchronous systems and hence prove their equivalence. The effectiveness of this method is demonstrated by verifying 8 synchronous elastic pipelined processor models with early evaluation.
Hybrid Renewable Energy System with Wind Turbine and PV Panels
(North Dakota State University, 2010) Kaderbhai, Munir Shabir
In recent years, there has been increasing concern about the world's heavy dependence on fossil-based fuels and the pollution caused by such fuels. This has sparked an increased interest in the use of other renewable sources of energy. In particular, electricity generation from wind and photovoltaic energy has seen a rapid growth in recent years. One of the most widely used electric machines used in wind energy conversion systems is the doubly-fed induction generator (DFIG) which requires a source and power converter system to feed variable frequency AC voltage to its rotor. Power converter schemes currently used with DFIGs, however, do not address issues such as the absence power factor correction in the rectifier (without complicated control loops), soft-switching in the rectifier, and the possibility of integrating photovoltaic power into the system to provide rotor injection power. This thesis presents a hybrid system in which the rotor power can be drawn either from three-phase AC mains or a photovoltaic (PV) panel-battery combination. While drawing power from AC mains, an AC-DC converter with soft switching and power factor correction is used. While supplying rotor injection power from PV panels, one of the MOSFET switches of the AC-DC converter will be used for boosting the PV panel output voltage. Various stages of the system are implemented and the details of implementation and results are discussed for each stage. Suggestions for future research are also offered.
Verification of Synchronous Elastic Pipelined Systems
(North Dakota State University, 2010) Sarker, Koushik
The constant shrinking of technology has lead to several design challenges that the synchronous design paradigm is unable to cope with. Elastic design is a novel and promising design paradigm that overcomes many of these challenges by using components that are insensitive to the latencies of its inputs. Verification is a critical problem for any design paradigm. The complexity of elastic designs arises when the system is pipelined. We develop formal verification techniques to verify synchronous elastic pipelined systems. Note that the goal of verification is not to establish the correctness of the algorithm for synthesizing elastic circuits, but instead, to find bugs and formally prove the correctness of elasticized designs. We develop two formal verification procedures. The first procedure checks the correctness of elastic pipelined systems against their synchronous parent pipelined systems. The second procedure checks the correctness of elastic pipelined systems against their high-level non-pipelined specifications (such as an instruction set architecture). Datatlow through elastic architectures is complicated by the insertion of any number of elastic buffers in any place in the design. We introduce elastic tokenflow diagrams, which arc used to track the flow of data in elastic architectures. We provide a method to construct such diagrams. We also develop highly automated and systematic procedures based on elastic token-flow diagrams that compute functions that map states of elastic systems to states of their specifications. Such functions, known as refinement maps, are used to compare behaviors of elastic and synchronous systems and hence prove their equivalence. We elasticized a 5-stage DLX processor that enables the insertion of buffers in its data path. We constructed several elastic processors by introducing up to 5 elastic buffers at various places in the data path and verified equivalence with both their synchronous parent pipelined systems and also with their instruction set architecture specifications.
A Sensor System Designed for Electrochemical Impedance Spectroscope-based Coating Performance Evaluation
(North Dakota State University, 2010) Shi, Yulong
One of the traditional methods for coating performance evaluation is using Electrochemical Impedance Spectroscopy (EIS). The theory of using EIS to evaluate coating performance is to measure the coating impedance in a frequency range of 0.01 Hz to 100 KHz. Based on the observation of a number of the EIS data, the coating impedance variation trend in low frequency range has a corresponding impedance variation trend in high frequency range. Based on this idea, this work introduces an EIS-based sensor system designed for coating performance evaluation. The sensor system consists of one base station and one sensor node. Wireless communication is realized between the sensor node and the base station. The sensor node is smaller than a business card in size. Evaluation time is less than 10 seconds in the operation frequency range between 20 90 kHz. Three coated panels were used for testing. Testing results are presented for both the EIS instrument and the sensor system. Good correlations indicate that this new technique is valid for EIS based coating performance evaluation in high frequency range. The sensor system is powered by batteries. The power consumption is •120 m W which is lower than the commercial ElS instrument The sensor system is portable and easy to use in real time for fieId coating performance evaluation.
Phasor Measurement Unit Placements for Complete Observability using Linear-Time, Quadratic-Time, and Subquadratic-Time Heuristics
(North Dakota State University, 2010) Saula, Oluwasijibomi
A phasor measurement unit (PMU) is considered to have the potential to improve the efficiency of electric power systems by monitoring, control, and protection. Through measurements of all bus voltages, incoming and outgoing currents, and by subsequent calculation of all phase angles, employing PMUs on every substation in a power system will allow complete observation of a power system. However, having a PMU on every substation may not be economically feasible. Therefore, methodologies must be devised that can monitor a system with the minimum possible number of PMUs. In this paper, we propose six graph theoretical PMU placement heuristics. The proposed heuristics overcome the previous approaches in terms of scalability and execution time. The proposed heuristics are thoroughly compared and benchmarked using standard IEEE bus networks ranging from 14 to 300 buses, and a 2,383 bus system.
Joint Compression and Encryption
(North Dakota State University, 2010) Ghosh, Ahana
This research work proposes two techniques of joint compression and encryption using Shanon Fano Elias coding and Arithmetic coding respectively. The first scheme proposed is called Adaptive Shannon-Fano-Elias code where it has been observed that the complexity of attacks is exponential in m, where m is the length of the string being compressed. Since mis usually very large (> 220 ), the security of our scheme is very high. The main reason why our scheme's security depends on m is the fact that all attacks require the ciphertext to be scanned from left to right. The algorithm proposed does not compromise in the compression ratio produced by normal Shannon Fano Elia coding. The second scheme proposed uses Arithmetic coding as the compression algorithm as Arithmetic coding is one of the optimal compression techniques that can be used in various applications. The algorithm proposed is proved to be secure under an assumption that the attacker would have access to an algorithm which could decrypt any given message without the knowledge of the key. i
Thermo-Mechanical Selective Laser Assisted Die Transfer
(North Dakota State University, 2011) Miller, Ross Alan
Laser Induced Forward Transfer (LIFT) techniques show promise as a disruptive technology which will enable the placement of components smaller than what conventional pick-and-place techniques are capable of today. Limitations of current die-attach techniques are presented and discussed and present the opportunity for a new placement method. This study introduces the Thermo-Mechanical Selective Laser Assisted Die Transfer (tmSLADT) process and is an application of the unique blistering behavior of a dynamic releasing layer when irradiated by low energy focused UV laser pulses. The potential of tmSLADT as the next generation LIFT technique is demonstrated by the "touchless" transfer of 65 μm thick silicon tiles between two substrates spaced 195 μm apart. Additionally, the advantages of an enclosed blister-actuator mechanism over previously studied ablative and thermal releasing techniques are discussed. Finally, experimental results studying transfer precision indicate this non optimized die transfer process compares with, and may exceed, the placement precision of current assembly techniques.
The Effects of Spatial and Temporal Properties on a Viscoelastic Model of the Dyssynchronous Canine Heart
(North Dakota State University, 2011) Satterlee, Cody Michael
In this study, lumped parameter cardiovascular modeling has been used to understand the influence of muscle properties on mechanical dyssynchrony (MD) as well as general muscle dynamics. Incorporating viscous influence into the model allowed for an expanded view when analyzing muscle parameter response to MD. A unique method of ventricle segmentation was introduced that allowed fast analysis of regional and global ventricular properties. This segmentation process produced a ventricle with four identical sections each consisting of separately tunable muscle properties in the form of minimum and maximum elastance, elastance waveform delay, and myocardial viscous friction, yet these regional sections remained globally dependent. Elastance waveform delay proved to be the most influential property on MD as measured by internal flow fraction (IFF), followed by regional elastance magnitude, and finally regional viscosity influence. Due to the unique segmentation of this model, two metrics for IFF were derived: (1) the "true" IFF (IFF-4seg) and (2) the IFF as would be measured by an ideal conductance catheter (IFF-CC). The results of IFF-CC versus IFF-4seg show that conductance catheters are not capable of measuring IFF during a side-to-side volume transfer within the stacked cylinder under measurement. Finally, unique energetic situations were observed with this model that point to likely myocardium remodeling situations.
A New Printed Quasi-Landstorfor Antenna
(North Dakota State University, 2011) Al Aziz, Masud
In this thesis, a new type of printed quasi-Landstorfer antenna is present ed. The proposed antenna utilizes parasitic radiators to realize a higher gain. The antc1ma is measured to have a resonant frequency of 2.45 GHz with a return loss of -43 cll3. The gain of the antenna is measured to be 7.2 dBi and can be increased to 8 dBi with the design of a folded slot. The gain increment is achieved without increasing the overall dimension of the antenna. Both the measured and the stimulated radiation patterns indicate that the antenna has a symmetric radiation pattern in the end-fire direction. Moment method based software has been used to stimulate quasi-Landstorfer antenna and the stimulated results are shown to be in good agreement with measured results. The new quasi-Landstorfer antenna presented in this work is 44% smaller in size when compared to the previous Landstorfer antennas and provides higher gain than that of quasi-Yagi antenna. The antenna is well suited for WLAN band applications, such as wireless communications, phased array antenna, and millimeter wave applications.
Impedance-Based Wireless Sensor Network for Metal-Protective Coating Evaluation
(North Dakota State University, 2011) Yu, Ronghua
Research has focused on the influences of flowing fluid on the corrosion of bare metals, but there is little emphasis on the degradation of metal-protective coating. Evaluating the metal-protective coating usually uses the Electrochemical Impedance Spectroscopy (EIS) method. This paper presents a new impedance-based wireless sensor network for metal-protective coating evaluation. This wireless sensor network consists of two parts: impedance-based wireless sensor nodes and a wireless data base that are equipped with a network analyzer (AD5933) and a RF transceiver (CC1111/CC1110). In the experiment, three coating panels are immersed in flowing deionized water (DI water) and one coating panel immersed in stationary DI water. Experimental results demonstrate that this wireless sensor network is capable of evaluating the coating degradation.
Damping Interarea Oscillations in Power Systems with DFIG
(North Dakota State University, 2011) Thapa, Ravi Chandra
With rapid depletion of fossil fuels and increasing environmental concerns, the trend to capture renewable energy, especially through wind energy resources, is increasing. The doubly fed induction generator (DFIG) is the most widely used generator for wind energy conversion because of its various advantages over other types of generators. In a DFIG, the rotor is fed through back to back converters via slip rings. The converters enable the generation control. This control property can be used to support reliable operation of a grid network system. Interarea oscillation has been a major factor in limiting power transfers in interconnected power systems. Poorly damped modes can trigger oscillatory instability, potentially leading to cascading blackouts in such systems. We consider a two-area system where DFIG based wind generation is integrated with conventional synchronous generators. A simple controller is proposed for the DFIG to improve damping of interarca oscillations. To support the proposition, case studies are conducted in Matlab/Simulink. The effectiveness of the proposed controller is then analyzed by eigenvalue analysis and verified with time domain simulation results. The results show that a properly tuned controller can increase the damping of dominant oscillatory mode by nearly 5% while improving the area transfer by about 200 MW of wind power. The results further show that with the proposed control strategy, damping of dominant oscillatory mode increased by more than 10%.
Solution Processing Electronics Using Si6 H12 Inks: Poly-Si TFTs and Co-Si MOS Capacitors
(North Dakota State University, 2011) Ullah, Syed Shihab
The development of new materials and processes for electronic devices has been driven by the integrated circuit (IC) industry since the dawn of the computer era. After several decades of '"Moore's Law"-type innovation, future miniaturization may be slowed down by materials and processing limitations. By way of comparison, the nascent field of flexible electronics is not driven by the smallest possible circuit dimension, but instead by cost and form-factor where features typical of 1970s CMOS (i.e., channel length - IO μm) will enable flexible electronic technologies such as RFID, e-paper, photovoltaics and health monitoring devices. In this thesis. cyclohexasilane is proposed and used as a key reagent in solution processing of poly-Si and Co-Si thin films with the former used as the active layer in thin film transistors (TFTs) and the latter as the gate metal in metal-oxide-semiconductor (MOS) capacitors. A work function of 4.356 eV was determined for the Co-Si thin films via capacitance-voltage (C-Y) characterization which differs slightly from that extracted from ultraviolet photoemission spectroscopy (UPS) data (i.e., 4.8 eV). Simulation showed the difference between the C-V and UPS-derived data may be attributed to the existence of 8.3 x 10 (exponent 10) cm-2 interface charge density in the oxide-semiconductor junction. Poly-Si TFTs prepared using Si6 H12-based inks maintained the following electrical attributes: field effect mobility of 0.1 cm2V-1s-1; threshold voltage of 66 V; and, an on/off ratio of 1630. A BSIM3 version 3 NFET model was modified through global parametric extraction procedure to match the transfer characteristics of the fabricated poly-Si TFT. It is anticipated that this model can be utilized for future design simulation for solution-processed poly-Si circuits.
Calculating Cardiovascular Lumped-Parameter Model Values by Injecting Small Volume Perturbations in an Isovolumic Heart
(North Dakota State University, 2011) Wandler, Jeff
Diagnosing cardiac patient problems contains many uncertainties, and to fully diagnose the patient's condition usually requires a lengthy drug regimen to see what works and what does not. Compounding this problem is that even after the correct drug regimen has been discovered, the underlying cause for the problem may remain a mystery. Thus, the uncertainty and the length of time required to provide an accurate and adequate solution makes it very difficult to provide quality care to the patient. Templeton and others have shown that lumped cardiac muscle parameters can be extracted from an isolated heart by injecting small volumes at high frequencies relative to the heart rate and measuring the pressure response to this volume change. Using the Hill muscle model of two springs and a dash pot to portray the different elements of the cardiac muscle, the pressure and volume relationship makes it possible to calculate these muscle parameters using frequency response analysis techniques. The hypothesis to be tested is "Is it possible to develop a method to test cardiac muscle for stiffness, resistance, and contractile force from measuring ventricular pressure and injected flow?" To test this hypothesis, an isovolumic heart model is developed and allowed to develop pressure, along with a small volume injected to create a pressure response. Analysis of the pressure and flow waveforms produces a measured value of the cardiac model parameter values to compare to the model values. Results from injecting small volume changes into a mathematical heart model show that it is possible to extract the muscle model parameters of non-linear resistance, inertia of the fluid and muscle, and stiffness of the muscle while filling and contracting. The injected frequency and volume were varied to find usable conditions, both with regard to the calculations and the practical limits. Analyzing the error between the measured and model values for a large number of different combinations of model parameters shows an average error of less than 1%.
Minimum Entropy Generation in the Cardiovascular System
(North Dakota State University, 2011) Schaible, Niccole Stephanie
This study was performed under the motivation to find a scheme that could describe the complex behavior of cardiovascular homeostasis. This is hypothesized to be manifested in a thermodynamic description of the cardiovascular system (CVS). Seen from a thermodynamic framework, the mechanics of blood flow can be gauged in similar terms as metabolic exchange at the capillaries - thereby providing a holistic and novel perspective on overall CVS function. Entropy generation, a thermodynamic calculation, represents lost work and is hypothesized to reveal something about the "optimal" state of the CVS. In particular, it is hypothesized that the CVS state that generates minimal entropy, given certain constraints, will be physiologically preferred and that cardiovascular control operates to find this state. This will be tested by first proposing a method to calculate entropy generation in the CVS, and secondly characterizing entropy generation across unique CVS states by simulation of a mathematical model.
Design of a Reconfigurable Pulsed Quad-Cell for Cellular-Automata-Based Conformal Computing
(North Dakota State University, 2011) Tan, Zhou
This paper presents the design of a reconfigurable asynchronous unit, called the pulsed quad-cell (PQ-cell), for conformal computing. The conformal computing vision is to create computational materials that can conform to the physical and computational needs of an application. PQ-cells, like cellular automata, are assembled into arrays with nearest neighbor communication and are capable of general computation. They operate asynchronously to minimize power consumption and to allow sealing without the limitations imposed by a global clock. Cell operations are stimulated by pulses which use two wires to encode a data bit. Cells are individually reconfirgurable to perform logic, move and store information, and coordinate parallel activity. The PQ-cell design targets a 0.25 μm CMOS technology. Simulation results show that a PQ-cell, when pulsed at 1.3 GHz, consumes 16.9 pJ per operation. Examples of self-timed multi-cell structures include a 98 MHz ring oscillator and a 385 MHz pipeline.
Wireless Health Monitor Design
(North Dakota State University, 2012) Koziy, Kostyantyn V.
In this thesis, a Wireless Health Monitor system for novel spacesuit verification and tests is presented. This system monitors the operator's health-related vital parameters and incorporates data acquisition, collecting and processing, wireless transmission, data displaying and logging. Power-saving technics for battery-powered applications are incorporated. A proprietary communication protocol for multi-node wireless network is developed and integrated. An embedded web interface for system control and data monitoring is utilized to achieve platform independence and reliability. Calculations and simulation results for the algorithms developed for gas flow measurements are presented. Packaging for this system, sensor calibration procedures, final device characteristics, specifications and field test results are described. Finally, future work toward possible device operation, improvement, and additional features is considered.
Hybrid Renewable Energy System Using Doubly-Fed Induction Generator and Multilevel Inverter
(North Dakota State University, 2012) Ahmed, Eshita
The proposed hybrid system generates AC power by combining solar and wind energy converted by a doubly-fed induction generator (DFIG). The DFIG, driven by a wind turbine, needs rotor excitation so the stator can supply a load or the grid. In a variable-speed wind energy system, the stator voltage and its frequency vary with wind speed, and in order to keep them constant, variable-voltage and variable-frequency rotor excitation is to be provided. A power conversion unit supplies the rotor, drawing power either from AC mains or from a PV panel depending on their availability. It consists of a multilevel inverter which gives lower harmonic distortion in the stator voltage. Maximum power point tracking techniques have been implemented for both wind and solar power. The complete hybrid renewable energy system is implemented in a PSIM-Simulink interface and the wind energy conversion portion is realized in hardware using dSPACE controller board.

Browse

Browsing Electrical & Computer Engineering Masters Theses by Issue Date