Stability analysis of a feedback-controlled resonant DC-DC converter

This paper reports on the stability analysis of one member of a dual-channel resonant DC-DC converter family. The study is confined to the buck configuration in symmetrical operation. The output voltage of the converter is controlled by a closed loop applying constant-frequency pulsewidth modulation. The dynamic analysis reveals that a bifurcation cascade develops as a result of increasing the loop gain. The trajectory of the variable-structure piecewise-linear nonlinear system pierces through the Poincare plane at the fixed point in state space when the loop gain is small. For stability criterion the positions of the characteristic multipliers of the Jacobian matrix belonging to the Poincare map function defined around the fixed point located in the Poincare plane is applied. In addition to the stability analysis, a bifurcation diagram is developed showing the four possible states of the feedback loop: the periodic, the quasi-periodic, the subharmonic, and the chaotic states. Simulation and test results verify the theory.     

A new approach to predict ulcerative colitis activity through standard clinical–biological parameters using a robust neural network model

Neural Computing and Applications - Colonoscopy is the “gold” standard for evaluating disease activity in ulcerative colitis (UC). An important area of research is finding a...     

Matrix equation for the motion of planar mechanisms with one degree of mobility using transmission functionsL'équation matricielle du mouvement des mécanismes plans avec un degré de mobilité, en utilisant les fonctions de transmission

The equations which describe the motion of mechanisms under the action of given forces (“dynamic response”) are generally complicated. That is why graphical methods are preferred. In the paper an algorithm is presented for writing the equation of motion of planar mechanisms with one degree of mobility in a matrix form, and to determine the dynamic response using automatic computer system. An example is given.     

Fast-scale instability of single-stage power-factor-correction power supplies

This paper describes the fast-scale bifurcation phenomena of a single-stage power-factor-correction (PFC) power supply which is a cost effective design for low-power applications. The circuit employs a cascade configuration of a boost converter and a forward converter, which share an active switch and operate in discontinuous conduction mode, to provide input PFC and tight output regulation. Main results are illustrated by "exact" circuit simulations as well as theoretical analysis based on the use of Jacobians. This work provides a convenient means of predicting stability boundaries which can facilitate the selection of practical parameter values for maintaining stable operation.     

Stability analysis of nonlinear power electronic systems utilizing periodicity and introducing auxiliary state vector

Variable-structure piecewise-linear nonlinear dynamic feedback systems emerge frequently in power electronics. This paper is concerned with the stability analysis of these systems. Although it applies the usual well-known and widely used approach, namely, the eigenvalues of the Jacobian matrix of the Poincare/spl acute/ map function belonging to a fixed point of the system to ascertain the stability, this paper offers two contributions for simplification as well that utilize the periodicity of the structure or configuration sequence and apply an alternative simpler and faster method for the determination of the Jacobian matrix. The new method works with differences of state variables rather than derivatives of the Poincare/spl acute/ map function (PMF) and offers geometric interpretations for each step. The determination of the derivates of PMF is not needed. A key element is the introduction of the so-called auxiliary state vector for preserving the switching instant belonging to the periodic steady-state unchanged even after the small deviations of the system orbit around the fixed point. In addition, the application of the method is illustrated on a resonant dc-dc buck converter.     

Comparative Study of Bifurcation in Single and Parallel-Connected Buck Converters Under Current-Mode Control: Disappearance of Period-Doubling

This paper studies a single buck converter and a system of parallel-connected dc/dc buck converters under current-mode control. The effects of variations of the reference current are studied. It has been observed that the system exhibits low-frequency bifurcation behaviour while period-doubling at switching frequency is suppressed. Extensive simulations are used to capture the behaviour. Time domain waveforms, stroboscopic maps, and trajectories are shown. The paper reveals the drastic alteration of bifurcation behaviour of dc/dc converters due to subtle coupling.     

Beiträge zur analyse der dynamischen antwortDynamic response analysis of some complex mechanisms by means of matrices

In two previous papers[2,3] the concept of “transmission vector” was defined and a numerical algorithms was presented for the dynamic response of plane mechanisms having one degree of freedom. This paper treats the problem of “transmission vectors” for plane, multiple-loop mechanisms. The method is applied to the problem of motion analysis for a complex mechanism having variable dimensions (Structure).