Elsevier

Chaos, Solitons & Fractals

Volume 23, Issue 4, February 2005, Pages 1285-1298
Chaos, Solitons & Fractals

Synchronization criteria of Lur’e systems with time-delay feedback control

https://doi.org/10.1016/j.chaos.2004.06.025Get rights and content

Abstract

In this paper time-delay effects on the master–slave synchronization scheme are studied by a time-delay feedback control technique. Several new delay-independent and delay-dependent sufficient conditions are presented for master–slave synchronization of Lur’e systems based upon Lyapunov method and linear matrix inequalities (LMI’s) approaches. These new synchronization criteria are easily verifiable and offer some fairly adjustable real parameters, which are of important significance in the design and applications of such chaos synchronization systems, and the proposed results improve and generalize the earlier works.

Introduction

In recent times, the subject of chaotic synchronization has received considerable attentions, e.g., [2], [3], [14], [16], [19], [21], [22], [23], [24], [25] and references cited therein. One unified approach to chaos synchronization is to reformulate it as a (generalized) Lur’e system and then discuss the absolute stability of its error dynamics [5], [6], [12], [16], [17], [20]. A typical approach in the Lur’e system approach to chaos synchronization problems is to derive a sufficient condition in the form of a special Lyapunov functional or a linear matrix inequality. In [18], several sufficient conditions were obtained for synchronization of identical or nonidentical systems. Synchronization schemes were investigated in the literature [10], [11], [12], [17], [20]. In [3], an overview of synchronization methods has been recently presented. Synchronization has opened the way to investigate an engineering application of chaos such as chaotic communications. In [4], it was reported for propagation delay in master–slave synchronization schemes, the authors introduced the possibility of applying chaotic synchronization to optical communication, called this problem a phase sensitivity due to the distance between two remote chaotic systems and reported that the existence of a time-delay may destroy synchronization, however, theoretical studies of this problem are few, and delays often result in instabilities. Therefore, stability analysis of time-delay systems is an important topic in control theory [9], [13].

In this paper, we will continue the study of the master–slave type of chaos synchronization problems, for a general form of Lur’e systems by a time-delay feedback control technique, initiated in [12], [20]. Several delay-independent and delay-dependent criteria for global asymptotic stability of the error system are given which is expressed as matrix inequalities and are derived from several new extended Lyapunov–Krasovskii functionals and inequalities techniques. It shows that the obtained results also improve and generalize the earlier works. In addition, the obtained criteria offer several adjustable real parameters, and are easy to verify, which are of important significance in the design and application of such chaos synchronization systems.

The organization of this paper is as follows. In Section 2, problem formulation and the master–slave synchronization scheme are presented for Lur’e systems with time-delay. In Section 3, based on several new Lyapunov–Krasovskii functional and linear matrix inequalities (LMI), several new delay-independent and delay-dependent criteria are given to ascertain the global asymptotic stability of the error system such that the master–slave system synchronizes. In Section 4, we provide an example for Lur’e systems and demonstrate the effectiveness of the proposed results. In Section 5, concluding remarks are given.

Section snippets

Problem formulation

Consider a general master–slave synchronization scheme with static error feedback and time-delay τM:x˙(t)=Ax(t)+Bσ(Cx(t)),p(t)=Hx(t),S:y˙(t)=Ay(t)+Bσ(Cy(t))+u(t),q(t)=Hy(t),C:u(t)=-K(x(t)-y(t))+M(p(t-τ)-q(t-τ)),with master system M, slave system S and controller C, see Fig. 1, where the time-delay τ > 0. The master and slave systems are Lur’e systems with state vectors x,yRn, output of subsystems p,qRl respectively, and matrices HRl×n,K,ARn×n,BRn×nh,CRnh×n. σi(·) satisfies a sector

Synchronization criteria of Lur’e systems

To give our main results, we need the following lemmas which could be found in [1], [8], [15].

Lemma 1

[15]

Given any real matrices W1, W2, Q of appropriate dimensions and a number ν > 0 such that 0 < Q = QT. Then the following inequality holds:W1TW2+W2TW1νW1TQW1+ν-1W2TQ-1W2.

Lemma 2

Schur complement [1]

For a given matrixS=S11S12S12TS22>0,where S11=S11T,S12=S12T, is equivalent toS22>0,S11-S12S22-1S12T>0.

Proof

Note thatI-S12S22-10IS11S12S12TS22I-S12S22-10IT=S11-S12S22-1S12T00S22.This completes the proof. 

Lemma 3

Jensen inequality [8]

For any constant matrix WRm×m, W = WT > 0, scalar

An example

Example

Consider the following scroll circuit given byx˙=a(y-h(x)),y˙=x-y+z,z˙=-by,with nonlinear characteristich(x)=m1x+12(m0-m1)(|x+c|-|x-c|),and parameters a = 9, b = 14.28, c = 1, m0 =  (1/7), m1 = 2/7. The system can be represented in Lur’e form byA=-am1a01-110-b0,B=-a(m0-m1)00,C = H = [1, 0, 0], and σ(ξ)=12(|ξ+c|-|ξ-c|) belonging to sector [0, k] with k = 1. This representation results in nh = 1. Let M = [4.0229, 1.3367, −2.1264]T, α = 0.8, K = −8I and F = MH. By direct computation with Matlab tools, when τ = 0.01, there exist Λ

Conclusion

A master–slave synchronization scheme has been addressed for Lur’e systems with a known delay existing between master and slave systems. Several new delay-independent and delay-dependent synchronization criteria, which have been expressed as matrix inequalities, have been given for Lur’e systems by introducing several new Lyapunov–Krasovskii functionals and LMI approach. These synchronization criteria are easily verifiable and offer some fairly adjustable real parameters α, β and γ, and the

Acknowledgments

This work was jointly supported by the National Natural Science Foundation of China under Grant 60373067 and S0390064, the National Basic Research Program of China under Grant 2003CB716206, and the Natural Science Foundation of Jiangsu Province, China under Grants BK2003053.

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