On stability of discrete-time systems under nonlinear time-varying perturbations

Ngoc Pham, Hieu, Hieu Le

Description

We give some explicit stability bounds for discrete-time systems subjected to time-varying and nonlinear perturbations. The obtained results are extensions of some well-known results in (Hinrichsen and Son in Int. J. Robust Nonlinear Control 8:1169-1188, 1998; Shafai et al. in IEEE Trans. Autom. Control 42:265-270, 1997) to nonlinear time-varying perturbations. Two examples are given to illustrate the obtained results. Finally, we present an Aizerman-type conjecture for discrete-time systems and show that this conjecture is valid for positive systems. MSC: 39A30, 93D09.

Sujets

• Discrete system
• Exponential stability

Informations

• Publié par: biomed
• Publié le: 01 janvier 2012
• Nombre de lectures: 24

Extrait

Ngoc and HieuAdvances in Difference Equations2012,2012:120 http://www.advancesindifferenceequations.com/content/2012/1/120

R E S E A R C HOpen Access On stability of discrete-time systems under nonlinear time-varying perturbations

1* 2 Pham Huu Anh Ngocand Le Trung Hieu

* Correspondence: [e-mail] 1 Department of Mathematics, International University, VNU-HCMC, Thu Duc, Sai Gon, Vietnam Full list of author information is available at the end of the article

Abstract We give some explicit stability bounds for discrete-time systems subjected to time-varying and nonlinear perturbations. The obtained results are extensions of some well-known results in (Hinrichsen and Son in Int. J. Robust Nonlinear Control 8:1169-1188, 1998; Shafaiet al.in IEEE Trans. Autom. Control 42:265-270, 1997) to nonlinear time-varying perturbations. Two examples are given to illustrate the obtained results. Finally, we present an Aizerman-type conjecture for discrete-time systems and show that this conjecture is valid for positive systems. MSC:39A30; 93D09 Keywords:discrete system; exponential stability; nonlinear time-varying perturbation

1 Introductionand preliminaries Discrete-time equations have numerous applications in science and engineering. They are used as models for a variety of phenomena in the life sciences, population biology, computing sciences, economics,etc.; see,e.g., [, , ]. Motivated by many applications in control engineering, problems of stability and robust stability of dynamical systems have attracted much attention from researchers for a long time, see,e.g., [, , , –, –] and references therein. In this paper, we investigate exponential stability of discrete-time systems subjected to nonlinear time-varying pertur- bations. Some explicit stability bounds for discrete-time systems subjected to nonlinear time-varying perturbations are given. Furthermore, we present an Aizerman-type conjec- ture for discrete-time systems and show that it is valid for positive systems. Two examples are given to illustrate the obtained results. + LetRbe the set of all real numbers and letNbe the set of all natural numbers. SetZ:= N∪ {}. For givenN∈N, let us denoteN:={, , . . . ,N}. Letn,l,qbe positive integers. Inequalities between real matrices or vectors will be understood componentwise,i.e., for two reall×q-matricesA= (a ij ) andB= (b ij ), the inequalityA≥Bmeansa ij ≥b ij for i= , . . . ,l;j= , . . . ,q. In particular, ifa ij >b ij fori= , . . . ,l;j= , . . . ,q, then we writeA l×q Binstead ofA≥B. The set of all nonnegativel×q-matrices is denoted byR + . Ifx= n l×q (x  ,x  , . . . ,x n )∈RandP= (p ij )∈Rwe define|x|= (|x i |) and|P|= (|p ij |). It is easy to see n×n that|CD| ≤ |C||D|. For any matrixA∈Rthespectral radiusofAis denoted byρ(A) = max{|λ|:λ∈σ(A)}, whereσ(A) :={z∈C:det(zI n –A) = }is the set of all eigenvalues n ofA. A norm ∙ onRis said to bemonotonicif|x| ≤ |y|impliesx ≤ yfor all  n np pp p x,y∈R. Everyp-norm onR(x p = (|x  |+|x  |+∙ ∙ ∙+|x n |) ,≤p<∞andx ∞ =

©2012 Ngoc and Hieu; licensee Springer. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.