Computing upper-bounds of the minimum dwell time of linear switched systems via homogenous polynomial lyapunov functions

Regular Session - Switched Systems IIThis paper investigates the minimum dwell time for switched linear systems. It is shown that a sequence of upper bounds of the minimum dwell time can be computed by exploiting homogeneous polynomial Lyapunov functions and convex optimization based on LMIs. This sequence is obtained by adopting two possible representations of homogeneous polynomials, one based on Kronecker products, and the other on the square matrix representation. Some examples illustrate the use and the potentialities of the proposed approach.published_or_final_versionThe 2010 American Control Conference (ACC), Baltimore, MD., 30 June-2 July 2010. In Proceedings of the American Control Conference, 2010, p. 2487-249

A nonconservative LMI condition for stability of switched systems with guaranteed dwell time

Ensuring stability of switched linear systems with a guaranteed dwell time is an important problem in control systems. Several methods have been proposed in the literature to address this problem, but unfortunately they provide sufficient conditions only. This technical note proposes the use of homogeneous polynomial Lyapunov functions in the non-restrictive case where all the subsystems are Hurwitz, showing that a sufficient condition can be provided in terms of an LMI feasibility test by exploiting a key representation of polynomials. Several properties are proved for this condition, in particular that it is also necessary for a sufficiently large degree of these functions. As a result, the proposed condition provides a sequence of upper bounds of the minimum dwell time that approximate it arbitrarily well. Some examples illustrate the proposed approach. © 2012 IEEE.published_or_final_versio

A note on the robust control of Markov jump linear uncertain systems

This note addresses a robust control problem of continuous-time jump linear Markovian systems subject to-norm bounded parametric uncertainties. The problem is expressed in terms of a H-infinity control problem as in the purely deterministic case. The present formulation is simpler and it contains previous results in the literature as particular cases. Robust state feedback controllers are parameterized by means of a set of linear matrix inequalities. The result is illustrated by solving some examples numerically. Copyright (C) John Wiley Sons, Ltd.23210511

Effects of Inhibiting CoQ10 Biosynthesis with 4-nitrobenzoate in Human Fibroblasts

Coenzyme Q10 (CoQ10) is a potent lipophilic antioxidant in cell membranes and a carrier of electrons in the mitochondrial respiratory chain. We previously characterized the effects of varying severities of CoQ10 deficiency on ROS production and mitochondrial bioenergetics in cells harboring genetic defects of CoQ10 biosynthesis. We observed a unimodal distribution of ROS production with CoQ10 deficiency: cells with <20% of CoQ10 and 50–70% of CoQ10 did not generate excess ROS while cells with 30–45% of CoQ10 showed increased ROS production and lipid peroxidation. Because our previous studies were limited to a small number of mutant cell lines with heterogeneous molecular defects, here, we treated 5 control and 2 mildly CoQ10 deficient fibroblasts with varying doses of 4-nitrobenzoate (4-NB), an analog of 4-hydroxybenzoate (4-HB) and inhibitor of 4-para-hydroxybenzoate:polyprenyl transferase (COQ2) to induce a range of CoQ10 deficiencies. Our results support the concept that the degree of CoQ10 deficiency in cells dictates the extent of ATP synthesis defects and ROS production and that 40–50% residual CoQ10 produces maximal oxidative stress and cell death

CONVEX-ANALYSIS AND GLOBAL OPTIMIZATION OF JOINT ACTUATOR LOCATION AND CONTROL-PROBLEMS

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DECENTRALIZED STABILIZATION AND STABILITY DOMAIN ESTIMATION OF CONTINUOUS AND DISCRETE NON-LINEAR SYSTEMS

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FREQUENCY-DOMAIN APPROACH TO THE ABSOLUTE STABILITY ANALYSIS OF DISCRETE-TIME LINEAR-QUADRATIC REGULATORS

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Robust H2 filtering for LTI systems with linear fractional representation

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)This article introduces a new approach to H2 robust filtering design for continuous and discrete-time LTI systems subjected to linear fractional parameter uncertainty representation. The novelty consists on the determination of a performance certificate in terms of the gap between lower and upper bounds of a minimax programming problem which defines the optimal robust filter and the associated equilibrium cost. The calculations are performed through convex programming methods, applying slack variables, known as multipliers, to handle the fractional dependence of the plant transfer function with respect to the parameter uncertainty. The theory is illustrated by means of an example borrowed from the literature and a practical application involving the design of a robust filter for the load voltage estimation on a transmission line with a stub feeding an unknown resistive load.821121272136Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq