Nonlinear Circuit Analysis via Perturbation Methods and Hardware Prototyping

Nonlinear signal processing is necessary in many emerging applications where form factor and power are at a premium. In order to make such complex computation feasible under these constraints, it is necessary to implement the signal processors as analog circuits. Since analog circuit design is largely based on a linear systems perspective, new tools are being introduced to circuit designers that allow them to understand and exploit circuit nonlinearity for useful processing. This paper discusses two such tools, which represent nonlinear circuit behavior in a graphical way, making it easy to develop a qualitative appreciation for the circuits under study

Novel Computing Paradigms using Oscillators

This dissertation is concerned with new ways of using oscillators to perform computational tasks. Specifically, it introduces methods for building finite state machines (for general-purpose Boolean computation) as well as Ising machines (for solving combinatorial optimization problems) using coupled oscillator networks.But firstly, why oscillators? Why use them for computation?An important reason is simply that oscillators are fascinating. Coupled oscillator systems often display intriguing synchronization phenomena where spontaneous patterns arise. From the synchronous flashing of fireflies to Huygens' clocks ticking in unison, from the molecular mechanism of circadian rhythms to the phase patterns in oscillatory neural circuits, the observation and study of synchronization in coupled oscillators has a long and rich history. Engineers across many disciplines have also taken inspiration from these phenomena, e.g., to design high-performance radio frequency communication circuits and optical lasers. To be able to contribute to the study of coupled oscillators and leverage them in novel paradigms of computing is without question an interesting andfulfilling quest in and of itself.Moreover, as Moore's Law nears its limits, new computing paradigms that are different from mere conventional complementary metal–oxide–semiconductor (CMOS) scaling have become an important area of exploration. One broad direction aims to improve CMOS performance using device technology such as fin field-effect transistors (FinFET) and gate-all-around (GAA) FETs. Other new computing schemes are based on non-CMOS material and device technology, e.g., graphene, carbon nanotubes, memristive devices, optical devices, etc.. Another growing trend in both academia and industry is to build digital application-specific integrated circuits (ASIC) suitable for speeding up certain computational tasks, often leveraging the parallel nature of unconventional non-von Neumann architectures. These schemes seek to circumvent the limitations posed at the device level through innovations at the system/architecture level.Our work on oscillator-based computation represents a direction that is different from the above and features several points of novelty and attractiveness. Firstly, it makes meaningful use of nonlinear dynamical phenomena to tackle well-defined computational tasks that span analog and digital domains. It also differs from conventional computational systems at the fundamental logic encoding level, using timing/phase of oscillation as opposed to voltage levels to represent logic values. These differences bring about several advantages. The change of logic encoding scheme has several device- and system-level benefits related to noise immunity and interference resistance. The use of nonlinear oscillator dynamics allows our systems to address problems difficult for conventional digital computation. Furthermore, our schemes are amenable to realizations using almost all types of oscillators, allowing a wide variety of devices from multiple physical domains to serve as the substrate for computing. This ability to leverage emerging multiphysics devices need not put off the realization of our ideas far into the future. Instead, implementations using well-established circuit technology are already both practical and attractive.This work also differs from all past work on oscillator-based computing, which mostly focuses on specialized image preprocessing tasks, such as edge detection, image segmentation and pattern recognition. Perhaps its most unique feature is that our systems use transitions between analog and digital modes of operation --- unlike other existing schemes that simply couple oscillators and let their phases settle to a continuum of values, we use a special type of injection locking to make each oscillator settle to one of the several well-defined multistable phase-locked states, which we use to encode logic values for computation. Our schemes of oscillator-based Boolean and Ising computation are built upon this digitization of phase; they expand the scope of oscillator-based computing significantly.Our ideas are built on years of past research in the modelling, simulation and analysis of oscillators. While there is a considerable amount of literature (arguably since Christiaan Huygens wrote about his observation of synchronized pendulum clocks in the 17th century) analyzing the synchronization phenomenon from different perspectives at different levels, we have been able to further develop the theory of injection locking, connecting the dots to find a path of analysis that starts from the low-level differential equations of individual oscillators and arrives at phase-based models and energy landscapes of coupled oscillator systems. This theoretical scaffolding is able not only to explain the operation of oscillator-based systems, but also to serve as the basis for simulation and design tools. Building on this, we explore the practical design of our proposed systems, demonstrate working prototypes, as well as develop the techniques, tools and methodologies essential for the process

A Fuzzy Logical-Based Variable Step Size P&O MPPT Algorithm for Photovoltaic System

The research presents a high-performance maximum power point tracking (MPPT) algorithm for Photovoltaic (PV) power generation systems. The proposed MPPT technique was simulated and validated via constructed PV emulator and dSPACE based rapid control prototyping system. Test results show that the proposed algorithm has significantly improved the tracking efficiency of PV energy conversion systems. The constructed test platform also provides a fast implementation of control algorithms in a real-time environment. The advantage of implementing the test platform is to give industries easy implementation of various control strategies for PV converters without dependency on atmospheric conditions”

Reduced-order modeling of power electronics components and systems

This dissertation addresses the seemingly inevitable compromise between modeling fidelity and simulation speed in power electronics. Higher-order effects are considered at the component and system levels. Order-reduction techniques are applied to provide insight into accurate, computationally efficient component-level (via reduced-order physics-based model) and system-level simulations (via multiresolution simulation). Proposed high-order models, verified with hardware measurements, are, in turn, used to verify the accuracy of final reduced-order models for both small- and large-signal excitations. At the component level, dynamic high-fidelity magnetic equivalent circuits are introduced for laminated and solid magnetic cores. Automated linear and nonlinear order-reduction techniques are introduced for linear magnetic systems, saturated systems, systems with relative motion, and multiple-winding systems, to extract the desired essential system dynamics. Finite-element models of magnetic components incorporating relative motion are set forth and then reduced. At the system level, a framework for multiresolution simulation of switching converters is developed. Multiresolution simulation provides an alternative method to analyze power converters by providing an appropriate amount of detail based on the time scale and phenomenon being considered. A detailed full-order converter model is built based upon high-order component models and accurate switching transitions. Efficient order-reduction techniques are used to extract several lower-order models for the desired resolution of the simulation. This simulation framework is extended to higher-order converters, converters with nonlinear elements, and closed-loop systems. The resulting rapid-to-integrate component models and flexible simulation frameworks could form the computational core of future virtual prototyping design and analysis environments for energy processing units

Model Reference Adaptive Control Laws: Application to Nonlinear Aeroelastic Systems

Nonlinear Aeroelastic Control has been a research topic of great interest for the past few decades. Dierent approaches has been attempted aiming to obtain better accuracy in the model dynamics description and better control performance. As far as the aeroelastic mathematical model is concerned, the scientic world converged in the use of a bi-dimension, two degree of freedom, plunging and pitching, wing section model, of which the bigger advantages are to be reproducible experimentally with an appropriate wind tunnel apparatus and to allow LCO (Limit Cycle Oscillation) exhibition at low values of wind speed, facilitating parametric studies of the nonlinear aeroelastic system and its control architecture. A parametric analysis of the linearized system, typical of aircraft ight dynamic studies, is employed to verify and validate the model dynamic properties dependency, focusing in particular to the eect of stiness reduction as means of failure simulation. In fact, despite of the recent years ourishing literature on aeroelastic adaptive controls, there is a noted lack of robustness and sensitivity analysis with respect to structural proprieties degradation which might be associated with a structural failure. Structural mode frequencies and aeroelastic response, including Limit Cycle Oscillations (LCOs) characteristics, are signicantly aected by changes in stiness. This leads to a great interest in evaluating and comparing the adaptation capabilities of dierent control architectures subjected to large plant uncertainties and unmodeled dynamics. Motivated by the constantly increasing diusion of the new L adaptive control theory, developed for the control of uncertain non-autonomous nonlinear systems, and by the fact that its application to aeroelasticity is in its infancy, a deep investigation of this control scheme properties and performance drew our attention. The new control theory is conceptually similar to the Model Reference Adaptive Control (MRAC) theory to which has often been compared indeed for performance evaluation purpose. In this dissertation, a comprehensive analysis of the new control theory is obtained by performance evaluation and comparison of four dierent control schemes, two MRAC and two L 1 , focusing the attention on the states and control input time response, adaptive law parameters' convergence, transient evolution and fastness, and robustness in terms of tolerance of uncertainties in o-design conditions. The objective is pursued by re- writing the aeroelastic model nonlinear equations of motion in an amenable form to the development of the four dierent control laws. The control laws are then derived for the appropriate class of plant which the system belongs to, and design parameter obtained, when necessary, following the mathematical formulation of the control theories developers. A simulation model is employed to carry out the numerical analysis and to outline pros and cons of each architecture, to obtain as nal result the architecture that better ts the nonlinear aeroelastic problem proposed. This methodology is used to guarantee a certain robustness in controlling a novel actuation architecture, developed for utter suppression of slender/highly exible wing, based on a coordinated multiple spoiler stripe, located at fteen percent of the mean aerodynamic chord. The control actuation system design, manufacturing and experimental wind tunnel test is part of the dissertation. Two dierent experimental setup are developed for two dierent purpose. First, a six-axis force balance test is carried out to validate the numerical aerodynamic results obtained during the validation process, and to collect the aerodynamic coecient date base useful for the development of the simulation model of the novel architecture. The second experimental apparatus, is a two degree of freedom, plunging/pitching, system on which the prototyped wing section is mounted to obtain LCO aeroelastic response during wind tunnel experiment. The nonlinear aeroelastic mathematical formulation is modied to take into account of the novel actuation architecture and, coupled with the more robust MRAC control laws derived for the previous model, serves as benchmark for properties assessment of the overall architecture, for utter suppression. The novel control actuation architecture proposed, is successfully tested in wind tunnel experimentation conrming the validity of the proposed solution. This dissertation provides a step forward to the denition of certain MRAC control schemes properties, and together provides a novel actuation solution for utter suppression which demonstrates to be a viable alternative to classical leading and/or trailing-edge ap architecture or to be used as redundancy to them

Research reports: 1990 NASA/ASEE Summer Faculty Fellowship Program

Reports on the research projects performed under the NASA/ASEE Summer Faculty Fellowship Program are presented. The program was conducted by The University of Alabama and MSFC during the period from June 4, 1990 through August 10, 1990. Some of the topics covered include: (1) Space Shuttles; (2) Space Station Freedom; (3) information systems; (4) materials and processes; (4) Space Shuttle main engine; (5) aerospace sciences; (6) mathematical models; (7) mission operations; (8) systems analysis and integration; (9) systems control; (10) structures and dynamics; (11) aerospace safety; and (12) remote sensin

Programmable photonics : an opportunity for an accessible large-volume PIC ecosystem

We look at the opportunities presented by the new concepts of generic programmable photonic integrated circuits (PIC) to deploy photonics on a larger scale. Programmable PICs consist of waveguide meshes of tunable couplers and phase shifters that can be reconfigured in software to define diverse functions and arbitrary connectivity between the input and output ports. Off-the-shelf programmable PICs can dramatically shorten the development time and deployment costs of new photonic products, as they bypass the design-fabrication cycle of a custom PIC. These chips, which actually consist of an entire technology stack of photonics, electronics packaging and software, can potentially be manufactured cheaper and in larger volumes than application-specific PICs. We look into the technology requirements of these generic programmable PICs and discuss the economy of scale. Finally, we make a qualitative analysis of the possible application spaces where generic programmable PICs can play an enabling role, especially to companies who do not have an in-depth background in PIC technology