This thesis presents an analytical approach using Root-Loci method for designing optimum passive series RC snubbers for continuous-current synchronous buck switch mode power supply (SMPS). Synchronous buck SMPS is the most popular power converter topology found in modern consumer electronics. It offers relatively good efficiency to target the high-current and low-voltage requirements while it is also relatively inexpensive to implement. Passive series RC snubbers are simple, efficient and cost-effective open-loop equalizer circuit for synchronous buck SMPS. Its purpose is to control and to balance between the rate of rise and the overshoots of transient switching waveform in order to optimize efficiency and reliability Existing methods of RC snubber design are solely based on second-order approximation. It is investigated in this research that this approximation is highly inaccurate in SMPS applications because higher order equivalent models are required for the load path of the SMPS. The results using the RC snubbers obtained from existing method are shown to be unsatisfactory without correlation to the calculations and simulations based on second-order approximation. Optimum RC values obtained using Root-Loci approach presented in this thesis are shown to correlate to both Spice simulation and lab measurements.

This thesis presents an analytical approach using Root-Loci method for designing optimum passive series RC snubbers for continuous-current synchronous buck switch mode power supply (SMPS). Synchronous buck SMPS is the most popular power converter topology found in modern consumer electronics. It offers relatively good efficiency to target the high-current and low-voltage requirements while it is also relatively inexpensive to implement. Passive series RC snubbers are simple, efficient and cost-effective open-loop equalizer circuit for synchronous buck SMPS. Its purpose is to control and to balance between the rate of rise and the overshoots of transient switching waveform in order to optimize efficiency and reliability Existing methods of RC snubber design are solely based on second-order approximation. It is investigated in this research that this approximation is highly inaccurate in SMPS applications because higher order equivalent models are required for the load path of the SMPS. The results using the RC snubbers obtained from existing method are shown to be unsatisfactory without correlation to the calculations and simulations based on second-order approximation. Optimum RC values obtained using Root-Loci approach presented in this thesis are shown to correlate to both Spice simulation and lab measurements.

This thesis presents rules that characterize the root locus for polynomials that are nonlinear in the root-locus parameter k. Classical root locus applies to polynomials that are affine in k. In contrast, this thesis considers polynomials that are quadratic or cubic in k. In particular, we focus on constructing the root locus for linear feedback control systems, where the closed-loop denominator polynomial is quadratic or cubic in k. First, we present quadratic root-locus rules for a controller class that yields a closed-loop denominator polynomial that is quadratic in k. Next, we develop cubic root-locus rules for a controller class that yields a closed-loop denominator polynomial that is cubic in k. Finally, we extend the quadratic root-locus rules to accommodate a larger class of controllers. We also provide controller design examples to demonstrate the quadratic and cubic root locus. For example, we show that the triple integrator can be high-gain stabilized using a controller that yields a closed-loop denominator polynomial that is quadratic in k. Similarly, we show that the quadruple integrator can be high-gain stabilized using a controller that yields a closed-loop denominator polynomial that is cubic in k.

In recent years, more and more light aircraft enter our daily life, from Agricultural applications, emergency rescue, flight experiment and training to Barriers to entry, light aircraft always have their own advantages. Thus, they have become more and more popular. However, in the process of GDP research about Flight Control System design for the Flying Crane, the author read a lot of literature about Flight Control System design, then noticed that the research in Flight Control System have apparently neglected to Low-cost vehicles. So it is necessary to do some study about Flight Control System for this kind of airplane. The study will more concern the control law design for ultra-light aircraft, the author hopes that with an ‘intelligence’ Flight Control System design, this kind of aircraft could sometimes perform flying tasks according to a prearranged flight path and without a pilot. As the Piper J-3 cub is very popular and the airframe data can be obtained more easily, it was selected as an objective aircraft for the control law design. Finally, a ¼ scale Piper J-3 cub model is selected and the aerodynamics coefficients are calculated by DATCOM and AVL. Based on the forces and moments acting on the aircraft, the trim equilibrium was calculated for getting proper dynamics coefficients for the selected flight conditions. With the aircraft aerodynamics coefficients, the aircraft dynamics characteristics and flying qualities are also analyzed. The model studied in this thesis cannot answer level one flying qualities in the longitudinal axis, which is required by MIL-F- 8785C. The stability augment system is designed to improve the flying qualities of the longitudinal axis. The work for autopilot design in this thesis includes five parts. First, the whole flight profile is designed to automatically control aircraft from takeoff to landing. Second, takeoff performance and guidance law is studied. Then, landing performance and trajectory is also investigated. After that, the control law design is decoupled into longitudinal axis and later-directional axis. Finally, simulation is executed to check the performance for the auto-controller.

Submitted by Maria Medeiros (maria.dilva1@ufcg.edu.br) on 2018-11-08T12:05:44Z No. of bitstreams: 1 JOSÉ NILTON SILVA - TESE (PPGEQ) 2013.pdf: 1910479 bytes, checksum: 59c6bfc5fdbee46bc17470e9b2c8c2e5 (MD5) / Made available in DSpace on 2018-11-08T12:05:44Z (GMT). No. of bitstreams: 1 JOSÉ NILTON SILVA - TESE (PPGEQ) 2013.pdf: 1910479 bytes, checksum: 59c6bfc5fdbee46bc17470e9b2c8c2e5 (MD5) Previous issue date: 2013-08-01 / Este trabalho trata do desenvolvimento de uma metodologia baseada nos conceitos clássicos de estatística e probabilidade para a análise e avaliação da robustez da estabilidade e do desempenho de sistemas de controle, particularmente àqueles que usam o PID (Proporcional, Integral, Derivativo) como lei de controle. Visando estabelecer as condições para a aplicação da metodologia, um sistema de identificação do processo foi desenvolvido de forma recursiva, no qual modelos de convolução e fenomenológico foram empregados como representação do modelo e processo, agrupado a um procedimento de auto sintonia, necessário para considerar os parâmetros de sintonia como variáveis aleatórias e, por conseguinte as raízes da equação característica do sistema em malha fechada.O mapeamento da região de robustez tem sido realizado a partir das raízes da equação característica, considerando a distância estatística como a métrica representativa da robustez da estabilidade a qual permite estabelecer a região com certo grau de significância.Os resultados obtidos demonstram o potencial analítico exigido pela metodologia, permitindo também a análise online, com baixo esforço computacional e operacional mostrando ser um poderoso instrumento de avaliação de sistema de controle. / This study discusses the development of a methodology based on classical concepts of statistics and probability to analyze and evaluate the robustness of the stability and performance of the control system, particularly those that use the PID as control law. To establish the conditions for the application of the methodology, a recursive system identification method process was developed, in which convolution and phenomenological models were used to represent model and process, together with a self-tuning procedure that is necessary to consider tuning parameters as random variables, and hence the roots of the characteristic equation of the closed loop system. The mapping of the region of robustness has been achieved from the roots of the characteristic equation, considering the statistical distance as the metric represented to the robustness of stability which allows the region to establish a degree of significance. The results obtained demonstrate the potential analytical and evaluation required by the methodology, allowing such analysis also "online" with low computational effort and operational proving to be a powerful tool in the analysis of control system.

This thesis deals with the identification and regulation of the "Ball & Plate" model. The thesis contains a description of the existing real model and the relevant mathematical and simulation model. The root hodograph method and the state space method are used to calculate the controller, especially the feedback controller with integrator. The final part of the work is devoted to the 3D model construction using Simulink and SimScape, which describes and visualizes the behavior of the real model and enables simulation experiments to be performed quickly and easily.

No description available.

Ultra narrow-band filters and the use of two loops in a cascade configuration dominate current clock conditioners based on phase-locked-loop (PLL) schemes. Since a PLL exhibits a low-pass transfer function with respect to the reference clock, the noise performance at very close-to-carrier offset frequencies is still determined by the input signal. Although better cleaning can be achieved with extremely narrow loops, an ultra low cut-off frequency could not be selected since the stability of the configuration deteriorates as the filter bandwidth is reduced. This fact suggests that a full-spectrum clock conditioning is not possible using traditional PLL architectures, and an alternative scheme is necessary to attenuate the very-close-to-carrier phase noise (PN). In addition, ultra-narrow loop filters can compromise on-chip integration because of the large size capacitors needed when chosen as passive. Input signal attenuation with relaxed bandwidth requirements becomes the main aspect that a comprehensive clock cleaner must address to effectively regenerate a reference signal. This dissertation describes the Band-Reject Nested-PLL (BRN-PLL) scheme, a modified PLL-based architecture that provides an effective signal cleaning procedure by introducing a notch in the input transfer function through inner and outer loops and a high-pass filter (HPF). This modified response attenuates the reference-signal PN and reduces the size of the loop-filter capacitors substantially. Ultra narrow loops are no longer required because the notch size is related to the system bandwidth. The associated transfer function for the constitutive blocks (phase detectors and local oscillators) show that the output close-to-carrier and far-from-carrier PN sections are mainly dominated by the noise from the inner-PLL phase detector (PD) and local oscillator (LO) located in the outer loop, respectively. The inner-PLL PD transfer function maintains a low-pass characteristic with a passband gain inversely proportional to the PD gain becoming the main contribution around the carrier signal. On the other hand, the PN around the transition frequency is determined mainly by the reference and the inner-PLL LO. Their noise contributions to the output will depend on the associated passband local maxima, which is located at the BRN-PLL transition frequency. Hence, in this region, the inner-PLL LO is selected so that its effect can be held below that of the outer-PLL PD. The BRN-PLL can use a high-Q MEMS-based VCO to further improve the transition region of the output PN profile and an LC-VCO as outer-PLL LO to reduce the noise floor of the output signal. In particular, two tuning mechanisms are explored for the MEMS-VCO: series tuning using varactors and phase shifting of a resonator operating in nonlinear regime. Both schemes are implemented to generate a tunable oscillator with no PN-performance degradation.

No description available.

This dissertation is concerned with the potential multistability of protein concentrations in the cell that can arise in biochemical networks. That is, situations where one, or a family of, proteins may sit at one of two or more different steady state concentrations in otherwise identical cells, and in spite of them being in the same environment. Models of multisite protein phosphorylation have shown that this mechanism is able to exhibit unlimited multistability. Nevertheless, these models have not considered enzyme docking, the binding of the enzymes to one or more substrate docking sites, which are separate from the motif that is chemically modified. Enzyme docking is, however, increasingly being recognised as a method to achieve specificity in protein phosphorylation and dephosphorylation cycles. Most models in the literature for these systems are deterministic i.e. based on Ordinary Differential Equations, despite the fact that these are accurate only in the limit of large molecule numbers. For small molecule numbers, a discrete probabilistic, stochastic, approach is more suitable. However, when compared to the tools available in the deterministic framework, the tools available for stochastic analysis offer inadequate visualisation and intuition. We firstly try to bridge that gap, by developing three tools: a) a discrete `nullclines' construct applicable to stochastic systems - an analogue to the ODE nullcines, b) a stochastic tool based on a Weakly Chained Diagonally Dominant M-matrix formulation of the Chemical Master Equation and c) an algorithm that is able to construct non-reversible Markov chains with desired stationary probability distributions. We subsequently prove that, for multisite protein phosphorylation and similar models, in the deterministic domain, enzyme docking and the consequent substrate enzyme-sequestration must inevitably limit the extent of multistability, ultimately to one steady state. In contrast, bimodality can be obtained in the stochastic domain even in situations where bistability is not possible for large molecule numbers. We finally extend our results to cases where we have an autophosphorylating kinase, as for example is the case with $Ca^{2+}$/calmodulin-dependent protein kinase II (CaMKII), a key enzyme in synaptic plasticity.