Theses and Dissertations - Department of Electrical & Computer Engineering (ECE)

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Correlation of low energy electrical measurements with the second breakdown characteristics of semiconductor devices
(University of Alabama Libraries, 1973) Friday, Edward Carney; University of Alabama Tuscaloosa
Coordination of systems of mobile robots with social potential functions
(University of Alabama Libraries, 2009) Samples, Richard Patrick; Leland, R. P.; University of Alabama Tuscaloosa
The research in this dissertation is concerned with developing a method to produce flocking behavior in a swarm of mobile robots. The dissertation itself is divided into three articles. The research in the first article is a proof-of-concept that demonstrates that one can create a swarm of mobile robots that engage in flocking behavior by the use of a position tracking controller in concert with a method for defining the desired trajectory for each object. The research in the second article develops a method for implementing both attractive and repulsive artificial potential functions with a position tracking controller. The research in the third article builds on that in the first two articles in order to construct a large swarm of mobile robots that engages in flocking behavior using a social potential function that is contructed from the attractive and repulsive functions of the second article. Each article contains both control-theoretic analysis of robot behavior and demonstrations of the behavior using Matlab simulations. The overall result is a successful, yet relatively simple, method for creating a swarm of mobile robots in which each robot has a degree of freedom of action.
Control of power converter for grid integration of renewable energy conversion and STATCOM systems
(University of Alabama Libraries, 2009) Xu, Ling; Li, Shuhui; University of Alabama Tuscaloosa
Investment in renewable energy is rapidly increasing worldwide. This is in response to a number of global challenges and concerns, including climate change, increasing energy demand, and energy security. The investment is widely spread over the leading renewable energy technology sectors: wind, solar, biofuels, biomass, and fuel cells. Among those, wind, solar photovoltaic, and fuel cells require power electronic converters for grid integration. This thesis investigates advanced control technology for grid integration control of renewable energy sources and STATCOM systems. First, the conventional control mechanism of power converters applied in renewable energy conversion and STATCOM systems is studied. Through both theoretical and simulation studies, a deficiency of the conventional control mechanism is identified. It is found that malfunctions of traditional power converter control techniques may occur when the controller output voltage exceeds the converter linear modulation limit. Then, the thesis proposes a novel control mechanism consisting of a current control loop and a voltage control loop. The proposed control mechanism integrates PID, adaptive, and fuzzy control techniques. An optimal control strategy is developed to ensure effective active power delivery and to improve system stability. The behaviors of conventional and proposed control techniques are compared and evaluated on both simulation and laboratory hardware testing systems, which demonstrates that the proposed control mechanism is effective for grid integration control over a wide range of system operating conditions while the conventional control mechanism may behave improperly, especially when the converter operates beyond its linear modulation limit and under variable system conditions.
Pac-man shaped magnetic tunnel junctions for SEU-resistant CMOS-based magnetic flip flops for space applications
(University of Alabama Libraries, 2009) Abo, Gavin S.; Hong, Yang-Ki; University of Alabama Tuscaloosa
Pac-man shaped magnetic tunnel junctions are proposed for CMOS-based magnetic flip flops for space applications. Micromagnetic simulation was performed on single layer elongated Pac-man shape, modified rectangular shape, and square shaped bilayer for magnetization process. The experimental effect of CoFe and IrMn thickness on the exchange field and coercivity of a Co₉₀Fe₁₀/Ir₂₀Mn₈₀ bilayer was studied. Metal mask process was used to fabricate rectangular shaped MTJ devices and the devices were characterized for magnetoresistance. In regards to micromagnetic simulation, the lowest coercivity of the elongated Pac-man element was found at an applied field direction at 45° with respect to the long axis of the element. Coherent switching of modified rectangular shapes was observed by simulation with a base height from 0.25 μm to 0.5 μm. In addition, simulation results of a 7 μm square shaped Ni₈₀Fe₂₀/antiferromagnetic bilayer are in fairly good agreement with experimental results for that of a 10 μm square shaped Ni₈₀Fe₂₀/Ir₂₀Mn₈₀ bilayer. Finally, CoFe thickness was found to be dominant in control of coercivity, while a combined effect of both CoFe and IrMn thickness has a major role in controlling of the exchange bias for a deposited CoFe/IrMn bilayer. The highest exchange of 87 Oe was achieved for Co₉₀Fe₁(8.5 nm)/Ir₂₀Mn₈₀ (17.5 nm). Magnetoresistance of four rectangular shaped MTJ device was measured to be 21% on average, but average resistance of the devices was 27 ohm. The resistance does not yet meet the targeted 10 kohm.
Compressive gait biometric with wireless distributed pyroelectric sensors
(University of Alabama Libraries, 2009) Li, Nanxiang; Hao, Qi; University of Alabama Tuscaloosa
Human tracking and recognition are desirable yet challenging for many applications including surveillance, computer vision, robotics, virtual reality, etc. Many biometric modalities have been used on these applications. Compared to other biometric modalities, such as fingerprints, face, and iris, gait biometrics are advantageous in their capability of recognition at a distance under changing environmental and cosmetic conditions. Despite having many limitations, from clothing changes to gait variation due to different physical and emotional conditions, the discrimination power of gait can still serve as a unique and useful component in human tracking and recognition systems. The work presented in this thesis aims at developing a distributed wireless sensor human recognition and tracking system, in order to improve the performance of previously established centralized pyroelectric sensor system. Our final goal is to provide wireless distributed pyroelectric sensor nodes as an alternative to the centralized infrared video sensors, with lower cost, lower detectability, lower power consumption and computation, and less privacy infringement. In previous related study, the system was able to succeed in identifying individuals walking along the same path, or just randomly inside a room, with an identification rate higher than 80% for around 10 subjects. For the human recognition system, innovations and adaptations are developed in: (1) sampling structure, multiple modified two-column sensor nodes are engaged to leverage the ability of effective acquisition of both the shape and dynamic gait attribution. (2) sensing protocols, different compressive measurement functions are provided for accomplishing the central task of compressive sensing protocol - choosing a proper scheme of the random projection encoding. (3) processing architecture, different levels of fusion schemes performed at data level, feature level, score level, and decision level constitute the processing architecture. Along with the advent of several new digital features, a higher recognition rate for both path dependent human recognition and path independent human recognition is achieved. For the human tracking system, a distributed tracking method was proposed to replace the previous centralized algorithm. Both recognition and tracking system will eventually be combined together and work cooperatively to form the human tracking and identification system. Real time implementation results are presented in the thesis. Moreover, experimental work and the related results are also discussed.
Oxygen depletion shutdown algorithm for portable gasoline generators
(University of Alabama Libraries, 2009) Smelser, Jennifer Beasley; Haskew, Tim A.; University of Alabama Tuscaloosa
Portable gasoline generators are very useful during power outages caused by snow storms, hurricanes, tornadoes, and earthquakes. If not used outdoors and away from the home, the consequences can be deadly. Due to the fatality rate caused by the poisonous carbon monoxide (CO) gas emitted from portable gasoline generators, the need for CO reduction and automatic generator shutdown has increased. This thesis presents the Engine Management System (EMS) used to reduce CO emissions from a commercial off-the-shelf Coleman Powermate 7000 Watt generator. Although reduced emissions was accomplished, there was still a need for an automatic shutdown feature in the event the generator was operated in an enclosed environment. Having operated in this type of environment, the generator's poisonous exhaust depletes the environment's oxygen (O2) content causing the intake air temperature (IAT), fuel pulse width (FPW), and fuel pulse width correction of the engine to change. The O2 depletion shutdown algorithm uses these variables as inputs in order to calculate a pseudo-derivative based upon a moving average for each input. A comparison is performed on each pseudo-derivative and if all three have met unacceptable limits for a predetermined period of samples, the engine will be shut down. The algorithm implemented in the engine control module (ECM) was tested under various loading conditions and proven to be successful under all loading conditions. This thesis presents the algorithm and test results from The University of Alabama and the National Institute of Standards and Technology.
Control design and analysis of doubly-fed induction generator in wind power application
(University of Alabama Libraries, 2009) Mazari, Shukul; Li, Shuhui; University of Alabama Tuscaloosa
The work presented in this thesis includes control system design, analysis and grid synchronization of a DFIG (doubly-fed induction generator) driven by a wind turbine using stator-voltage and stator-flux oriented frames. The DFIG is a special type of induction machine which is comprised of two back-to-back converters. One converter connects the DFIG stator to the grid, and the second converter is connected to the rotor of the machine through a DC-link capacitor. In this work, DFIG steady-state and transient models have been created in the d-q reference frame. The steady-state model is used to obtain the relationship between the rotor d-q currents and stator real/reactive power references in a particular orientation frame. The transient model is used to develop the DFIG power control mechanisms. The wind turbine driving torque is modeled by considering typical wind turbine aerodynamic characteristics under variable wind and pitch angle conditions. Comparisons are made to evaluate the differences between DFIG current/power controller in stator-voltage and stator-flux oriented frames. A speed control system has been designed to analyze maximum energy extraction from a DFIG for a particular wind speed. Lastly, the grid synchronization control technique and synchronization method have been proposed as this system requires some care during the machine start-up and integration with the grid. The main aim of the synchronization control process is to avoid heavy start-up currents and mechanical stresses on the turbine shaft and other integrated components. This is achieved by properly matching the phase angle, frequency, and magnitude of the grid voltage and the stator induced voltage irrespective of whether it is a stator-voltage or stator-flux oriented frame used for modeling the generator. Instead of a traditional control scheme using a PLL (phase-locked loop), the rotor d-q reference current is generated with grid voltage as the reference so as to induce identical voltage in the stator as that of the grid. The machine is started by a driving torque and the switch between stator and the grid can be closed for synchronization. However, appropriate timing of switch closure plays a critical role in satisfying the magnitude condition of synchronization. Simulation models have been developed using Matlab®/Simulink® for a GE 1.5 MW generator.
Development of high-density RF board diagnostic program
(University of Alabama Libraries, 2010) Kannan, Sukeshwar; Kim, Bruce C.; University of Alabama Tuscaloosa
This thesis describes the development and application of a software tool. RF Analyzer and Diagnostic Program Generation Tool (RADPro) has been developed to automate the process of testing the RF Device Interface Boards (DIB). DIBs are essential components for testing ICs and they contain mixed-signal and RF circuits with several active and passive components that are needed to simulate test conditions for ICs. A new integrated software environment has been developed to automatically generate functional tests for board verification. This software environment utilizes the schematic information, DIB-specific constraints, accessibility provided by the test hardware and instrument automation tools to generate a functional test program. The output of the tool is a generic test specification that is independent of test hardware platform. RADPro has been developed for testing RF DIBs at Texas Instruments Inc. Test execution has been performed on several RF DIBs and the test results have been recorded in the pseudocode format as well as look up table which provides a detailed analysis of all possible faults that can occur in the passive components. Complete automation of DIB test methodology implementation has been presented in this thesis. Automatic test generation by RADPro reduces design expenses and time to market significantly in comparison with the existing techniques. The testing methodology presented in this thesis produces the pseudocode for automating the test procedure on Very Low Cost Tester (VLCT) systems.
Fabrication and reliability testing of copper-filled through-silicon vias for three-dimensional chip stacking applications
(University of Alabama Libraries, 2010) Kamto Tegueu, Alphonse Marie; Burkett, Susan L.; University of Alabama Tuscaloosa
Through-silicon vias (TSVs) have been extensively studied because of their ability to achieve chip stacking for enhanced system performance. The fabrication process is becoming somewhat mature. However, reliability issues need to be addressed in order for an eventual transition from laboratory to production. This dissertation discusses the TSV fabrication process, testing results for TSV reliability investigation of an integration of TSVs and capacitor devices. In our laboratory, vias with tapered sidewalls are formed through a modified Bosch process using deep reactive ion etching (DRIE). Cryogenic etching is also considered as a means to etch vias without sidewall scalloping that is observed for the Bosch process. Vias are lined with silicon dioxide using plasma enhanced chemical vapor deposition (PECVD) followed by a sputter deposited titanium barrier and a copper seed layer before filling by a reverse pulse copper electroplating process. Following attachment of the process wafer to a carrier wafer, the process wafer is thinned from the backside by a combination of mechanical methods and reactive ion etching (RIE). Fabricated vias are subjected to thermal cycling with temperatures ranging from 25 °C to 125 °C. TSVs are shown to be stable with small increases in measured resistance for 200 cycles. In addition, small changes in resistance are observed when vias are held at elevated temperatures for extended periods of time. Integration of decoupling capacitors with TSVs represents a good alternative to conventional 2-D layouts to achieve miniaturization and increased density. Therefore, decoupling capacitors can be brought in close proximity to the active elements, thereby, reducing their parasitic inductance and allowing higher clock rates. In this study, capacitors with anodized tantalum as the dielectric are integrated with TSVs without negatively impacting their operation. The performance of these capacitors was evaluated by measuring resonant frequency, parasitic inductance, and parasitic resistance.
Analysis of low voltage regulator efficiency based on ferrite inductor
(University of Alabama Libraries, 2010) Kothakonda, Mridula; Hong, Yang-Ki; University of Alabama Tuscaloosa
Low voltage regulator based on ferrite inductor, using single- and two-phase topologies, were designed and simulated in MATLAB. Simulated values of output voltage and current were used to evaluate the buck converter (i.e., low voltage regulator) for power efficiency and percentage ripple reduction at frequencies between 1 and 10 MHz with variable loads from 0.024 to 4 ohms. The parameters, such as inductance of 20 nH, quality factor of 15 of fabricated ferrite inductor and DC resistance (DCR) of 8.3 milli ohms, were used for efficiency analysis of the converter. High current around 40 A was achieved by the converter at low load values. Low output voltage in the range of 0.8-1.2 V was achieved. The simulated results for the single- and two-phase converter were compared for maximum efficiency and lowest ripple in output voltage and current. The maximum efficiency of 97 % with load of 0.33 ohms and the lowest ripple current of about 2.3 mA were estimated for the two-phase converter at 10 MHz. In summary, the two-phase converter showed higher efficiency and lower ripple voltage and current than those of the single-phase converter. In addition, the efficiency of single- and two-phase converters based on ferrite inductor was compared to single- and two-phase converters based on air-core inductor. It was found that the power efficiency of the two-phase converter using ferrite inductor was 10 % higher than the converter using air-core inductor at 10 MHz with a load of 0.024 ohms.
A simultaneous localization and mapping implementation using inexpensive hardware
(University of Alabama Libraries, 2010) Aycock, Todd Michael; Ricks, Kenneth G.; University of Alabama Tuscaloosa
Autonomous mobile robots have become more popular over the past few decades, influencing both industry and academia. The strategy of making robots navigate autonomously adds many problems however. Many of these problems are directly related to the robot's ability to localize and autonomously map its environment. A solution to this problem is called simultaneous localization and mapping (SLAM). SLAM is the concept of localizing the robot while simultaneously generating a map of the environment, and then using the map in subsequent localization steps. The success of SLAM lies in a filter algorithm. One of the more common and successful filters is the extended Kalman filter (EKF), and there are many different algorithms that could be used to implement this filter. However, the computational complexity and physical cost of implementing the algorithm place the SLAM solution beyond the scope of many low-cost robotics projects. This thesis analyzes many of these cost issues related to the implementation of SLAM on autonomous robots. First, the types of sensing hardware are discussed, and potential low-cost solutions are suggested. Next, timing aspects of two different methods for data association are examined in order to evaluate tradeoffs between speed and accuracy. Finally, optimizations to the filter's update step involving matrix multiplication are presented. These three changes are presented as a customized EKF SLAM algorithm, called inexpensive hardware SLAM (IH-SLAM), which is applicable to small-scale robotics applications.
Software implementation of a terahertz imaging and spectroscopy platform
(University of Alabama Libraries, 2010) Ajilore, Babatunde; Kim, Seongsin; Kung, Patrick; University of Alabama Tuscaloosa
A terahertz imaging system was built from commercially available hardware whose functionality was integrated through home-made software with the goal of building a terahertz imaging platform for which other terahertz technologies would be born out of. The core of the system is based on terahertz time domain spectroscopy; a technique in which terahertz radiation is generated and detected by optically gating an emitter and detector respectively. Terahertz images of common objects found in a laboratory were produced primarily to test and calibrate the system and a new modality for achieving three-dimensional terahertz imaging for systems setup in transmission geometry is proposed based on these images.
Digital pulse width modulation techniques for power converters
(University of Alabama Libraries, 2010) Arunachalam, Thanukamalam; Abu Qahouq, Jaber A.; University of Alabama Tuscaloosa
Recently, digital controls are becoming dominant in almost every power electronic application because of the advantage when compared to analog control. This includes the ability of digital controllers to perform more advanced and sophisticated functions that potentially result in improving power conversion efficiency and/or the dynamic performance of the power converter, the ease of digital control function and loop upgradeability (or revision), and reduced sensitivity to component variations. However, there are also some challenges in digital control such as control loop delays that impact the dynamic performance of the power converters and the additional controller power consumption in some digital control implementations. Digital Pulse Width Modulation (DPWM) is one of the most important parts in digital control systems which control the power switch of the power converters. Modulation technique plays a vital role in causing control delays. There are several implementation schemes of digital pulse width modulation such as counter based DPWM, delay line based DPWM, and hybrid based DPWM. The output voltage is required to have little deviation from the reference voltage and fast settling times under transient events. Therefore, in order to maintain a well regulated output voltage, the control signal must instruct the power converter to either turn on (when there is undershoot in output voltage) or turn off (when there is overshoot in output voltage), as fast as possible. The work presented in this thesis suggests a modulation technique that reduces the turn on delay caused by trailing-edge digital modulation and turn off delay caused by leading-edge digital modulation. Reducing the digital pulse width modulation delay reduces the overshoot and undershoot in the output voltage in power converters with digital closed loop control. The proposed modified digital pulse width modulation scheme is verified using computer simulations and experimental results.
Simulation of a radio frequency identification system utilizing direct sequence spread spectrum and additional improvement techniques
(University of Alabama Libraries, 2010) Bostick, Brian Gregory; Stern, Harold P. E.; University of Alabama Tuscaloosa
Radio Frequency Identification (RFID) is a technology that has been in use since World War II and has evolved from the means by which an army was able to identify approaching aircraft to a versatile data gathering tool which is used in a variety of applications. Paramount concerns to any RFID system include accuracy, data security, system capacity and efficiency as well as system architectures to take into consideration the unique aspects of particular applications. In this work, a generalized RFID system is developed to allow multiple passive RFID tags to simultaneously communicate with a single reader. Applications include inventory, retail checkout, industrial process tracking, and security. The system uses direct sequence spread spectrum (DSSS) as its multiple access technique, and several unique system modifications are proposed to improve the accuracy and capacity of the generalized system. Simulation results show the performance of the generalized system and show that the proposed modifications to the system do in fact improve the system's accuracy and capacity, both in a noiseless environment and in an environment with additive white Gaussian noise. A comparison of the proposed modifications is performed and suggestions for their implementation are discussed.
Compressive brain neural activity detection using functional magnetic resonance images
(University of Alabama Libraries, 2010) Li, Chuan; Hao, Qi; University of Alabama Tuscaloosa
The goal of our research is to develop a framework of data processing and logic inference which can identify the neural activity patterns using fMRI measurements with high accuracy at low computational cost. Throughout the development, the following issues have been focused and investigated: 1) Selection and modeling of a priori. The prior knowledge includes the sparse nature of neural activities, the spatial/temporal correlations and the structural measurement invariance. Proper mathematical models should be developed and utilized to reduce the data volume, to restore the image distortions, and to remove the false alarms. We have developed a series of models including wavelet/contourlet hidden Markov tree, hidden Markov chain and multi-layer/multi-scale neural hemodynamic model. Based on those models, the fMRI data can reveal more statistical patterns with respect to specific subject behavior. 2) Algorithmic tradeoff between performance and cost. This requirement needs efficient representation of fMRI information and fast convergent detection. In this respect, we have explored several high efficiency methods including linear predictive coding, contourlet decomposition, and random projection to reduce the data dimensionality without losing information of interest. In addition, various learning/regularization approaches have been investigated to increase the convergence speed as well as robustness. 3) Combination of information processing techniques in the logic and data layers. Most conventional techniques process information in data layer. We further generate logical events and probabilistic structures out of the original measurements through data modeling and information learning. The logic layers feature fast speed and high robustness against measurement noise, motion artifacts and false alarms. By using various logic models and inference methods, conventional fMRI data processing techniques can be enhanced. The main accomplishments of this thesis include three components. 1) Image restoration using wavelet/contourlet hidden Markov tree (HMT) models. 2) Independent component analysis (ICA) with L1 norm regularization. 3) Graphical model inference for compressive neural activity detection. Through developing these three components, this dissertation provides a complete robust neural activity identification/detection framework, from image restoration to signal decomposition and finally to signal inference, with high accuracy and low computational cost.
Study of vibration and audible noise generated by shunt capacitor banks at substations serving non-linear loads
(University of Alabama Libraries, 2011) Roget, Adam Brent; Haskew, Tim A.; University of Alabama Tuscaloosa
At the request of a local utility provider, a study was conducted to determine why capacitor banks located at two substations supplying power to a steel mill are creating audible noise. A method to decrease the amount of audible noise was also requested. The construction of the banks and the possible cause of excitation are discussed. Electrical current and acoustic harmonic measurements taken at each substation are presented. Vibration testing of the banks was conducted to determine the mechanical natural frequencies, and the results are given. Possible solutions to reduce the amount of audible noise from the capacitors conclude the discussion.
A custom printed circuit board design for microcontroller education
(University of Alabama Libraries, 2011) Taylor, Ryan Andrew; Jackson, Jeff; University of Alabama Tuscaloosa
Much time and effort has been spent attempting to discover the best approach to the problem of microcontroller education. In electrical and computer engineering curricula, much consideration is given to the topic of hardware interfacing. For the potential computer engineer, this is an important concept to master, in view of its significance in the current state of technology. Unfortunately, in many curricula, the student is introduced to digital circuitry and immediately thrust into interfacing, due to the pressures of time in a traditional four-year academic career. Often, the student's understanding of the basics of microcontroller operation and control are not to a satisfactory level before the student is expected to use a processor to control other, more complex, systems. This research attempts to compile a solution to allow a student to be well versed in microcontroller operation while he or she begins to work with additional interfacing requirements. A prototype printed circuit board has been assembled that works in close harmony with the National Instrument ELVIS prototyping system that attempts to alleviate this problem. This prototype daughter card rests on top of the breadboarding area of the ELVIS system and allows the student full access to all of the tools and contacts that would be available without the card. The student is required to make the connections necessary for a fully-functional microcontroller system, as opposed to the method of using a pre-fabricated microcontroller development board. When using a board such as this, the student may not fully understand the individual components and their interconnections. This process of connecting components requires the student to understand the physical interface between the microcontroller and the peripheral device(s). Anticipated results from this research are an increased aptitude in peripheral interfacing and a greater level of success in more complex courses following in the curriculum. By allowing the student to interact with the interfacing process on a lower level, a more complete understanding of microcontroller-based systems and peripheral interfacing is obtained.
Adaptive control methods for DC-DC switching power converters
(University of Alabama Libraries, 2011) Arikatla, VaraPrasad; Abu Qahouq, Jaber A.; University of Alabama Tuscaloosa
Tight regulation of the output voltage is often required in many power supply applications, despite the highly dynamic nature of the loads. This is conventionally obtained by the design of high bandwidth feedback loop or recently by using adaptive control methods. The control loop is designed with specified safe bandwidth and gain and phase margins such that it maintains stable operation under variable conditions and parameters. However, this results in a compromise between achievable dynamic performance and robustness of control loop. The large variations in operating points and load makes the system design challenging. The tight regulation requirements, in addition to size and weight requirements, are getting stricter by time, which makes it necessary to investigate new control concepts in order to meet these requirements. Not meeting the tight regulation requirements may result in either the malfunctioning of the device (load) being powered or the destruction of that device. This work focuses on the development and implementation of adaptive control methods that result in the improvement of the dynamic performance of power converter, by utilizing the flexibility of digital controllers to realize advanced control schemes. Four different methods are proposed that improve the dynamic performance of converter without compromising the steady-state performance. A Sensorless Adaptive Voltage Positioning (SLAVP) control scheme is proposed in Chapter 2, in order to realize Adaptive Voltage Positioning (AVP) control without the need for load or inductor current sensing and high-resolution high-speed Analog-to-Digital Converter (ADC) sampling. The SLAVP control law utilizes the readily available error signal of the conventional voltage-mode closed-loop compensated controller, or in other words the duty cycle of a DC-DC buck converter, in order to realize AVP control. The elimination of the need for high-speed and accurate sensing and sampling of currents using the proposed SLAVP control reduces the size and cost of the digital controller, reduces the power losses associated with current sensing and sampling, and simplifies hardware design, apart from improving dynamic performance. In Chapter 3, an Adaptive Digital PID (AD-PID) controller scheme is proposed. The controller adaptively adjusts the integral constant (K_i) and the proportional constant (K_p) of the compensator following a new control law. The control law is a function of the magnitude change in the error signal and its peak value during dynamic transients. The proposed AD-PID controller adaptively detects the peak value of the error signal which is a function of the transient nature and magnitude and utilize it in the control law such that no ocillations are generated as a result of the adaptive operation. As a result, the dynamic output voltage deviation and the settling time of the output voltage are reduced. A novel Compensator Error Observe and Modulate method (CEO&M) for online closed-loop-compensator auto-tuning of digital power controller is proposed in Chapter 4. The proposed method is relatively simple and does not require the knowledge and/or measurement of the power stage or closed-loop frequency response. Moreover, the proposed method does not depend on conventional design methods and the associated rule of thumb design criteria in order to tune closed-loop feedback controllers of power converter for high, and possibly optimum, dynamic performance. Furthermore, two approaches for dynamic variable switching frequency digital control scheme under dynamic transients are proposed in Chapter 5 in order to improve the dynamic performance of the DC-DC switching power converter. The proposed controller varies the switching frequency of the converter, higher or lower than the steady-state frequency, during the transient as a function of peak and magnitude of error signal depending on the amount and type of the transient. Finally, Chapter 6 summarizes this work and provides conclusions before discussing future related research direction.
An experimental investigation of an on-chip interconnect fabric using a multiprocessor system-on-chip architecture
(University of Alabama Libraries, 2011) Bangal, Priya; Ricks, Kenneth G.; University of Alabama Tuscaloosa
Recent advances in technology have made it possible to integrate systems with CPUs, memory units, buses, specialized logic, other digital functions and their interconnections on a single chip, giving rise to the concept of system-on-chip (SoC) architectures. In order to keep up with the incoming data rates of modern applications and to handle concurrent real-world events in real-time, multiprocessor SoC implementations have become necessary. As more processors and peripherals are being integrated on a single chip, providing an efficient and a functionally optimum interconnection has become a major design challenge. The traditional shared-bus-based approach is quite popular in SoC architectures as it is simple, well-understood and easy to implement. However, its scalability is limited, since the bus invariably becomes a bottleneck as more processors are added. Switch-based networks can overcome this bottleneck while providing true concurrency and task-level parallelism, resulting in a higher throughput. However, switch-based networks are complex and consume considerable amounts of logic resources on a chip, thus increasing the cost. Hence, the choice of switch-based networks over a bus-based architecture is an important design consideration in SoC architectures. This choice hinges on the trade-off between design simplicity and low cost vs. high communication bandwidth. This research investigates the logic resource utilization of a switch-based on-chip interconnect to analyze its scalability for multiprocessor systems. It also experimentally demonstrates the true concurrency provided by the interconnect, investigates the arbitration mechanism used, and suggests the use of a real-time operating system (RTOS) as a more effective way of managing on-chip interconnections.
Design and self-calibration scheme for RF circuits using mems in 3D packages
(University of Alabama Libraries, 2011) Evana, Naga Sai Shravan; Kim, Bruce C.; University of Alabama Tuscaloosa
This thesis presents a novel on-chip testing and self-calibration methodology of a 5 GHz Low Noise Amplifier (LNA) with micro electro-mechanical switches (MEMS) using three dimensional (3D) through-silicon via (TSV) packaging technology. The LNA can self-calibrate its gain and noise figure (NF). On-chip testing is performed using a peak detector and a digital signal processor (DSP). A low-cost self-calibration scheme is proposed which utilizes a tuning circuit consisting of an inductor and capacitor bank and a MEMS switch matrix. The MEMS switch matrix and the analog circuitry are fabricated on two separate dies and stacked using TSV. With increasing demand for integrating analog, digital and RF circuits on a single chip, 3D packaging is the best way to realize this. The utilization of 3D-TSV technology in this work optimized the usage of real estate without compromising on the signal integrity of the complete circuit. MEMS switches provided high isolation and lesser parasitic effects than conventional transistor based switches. Most of the parametric variations within the LNA were identified by the testing circuit. The self-calibration circuit is capable of correcting these variations. The testing and self-calibration circuits successfully accomplished the task of keeping the gain of the LNA > 8 dB, noise figure < 2 dB and stability factor > 1.

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