Robust stability for affine T-S fuzzy impulsive control systems subject to parametric uncertainties
Iman Zamani Electrical and Electronic Engineering Department, Shahed University, Tehran, Iran
Amir Hossein Amiri Mehra Electrical and Electronic Engineering Department, Shahed University, Tehran, Iran
Zohreh Abbasi Electrical and Computer Engineering Department, Qom
University of Technology, Qom, Iran, [email protected]
Masoud Shafiee Department of Electrical
Engineering, Amirkabir University of Technology,
Tehran, Iran, [email protected]
AbstractโThe main objective of this paper is to investigate the robust stability problem of affine fuzzy impulsive control systems in which the system is presented by affine Takagi-Sugeno fuzzy model. By using extended Lyapunov stability theory, some matrix inequalities conditions are derived to guarantee the stability of affine Takagi-Sugeno fuzzy impulsive control systems subject to parametric uncertainties. A numerical example is given to confirm the analytical results and illustrate the effectiveness of the proposed strategy.
Keywords- Affine Takagi-Sugeno Fuzzy system; Impulsive control strategy; Parametric uncertainties
I. INTRODUCTION
Motivated from impulsive differential equations, the effects of impulses can be used as a strategy in control theory which is named as โโimpulsive control strategyโโ. The main idea of impulsive control strategy is to change the states of continuous dynamic systems via discontinuous control inputs at certain time moments. Impulsive control strategy has attracted many literatures [1, 2] and have been widely used for stabilization and synchronization of complex delayed dynamical networks [1-4], switched systems [5-7], optimal control for switched systems [8], large-scale systems [9], control of biological models [10], control of chaotic systems [11] and etc. Among of these systems, which have used impulsive control strategy, fuzzy systems have attracted many interests [12-17]. Many theories and relevant method were developed for fuzzy systems in previous decade and applied with more or less success depending on the specific problem [18-23]. Extended and innovative methods and relevant conditions for stability analysis of fuzzy impulsive control systems were found. Some methods and conditions for stability in continuous and discrete fuzzy impulsive control systems are presented in [24-27]. To the best of our knowledge, stability analysis of affine T-S fuzzy impulsive control system has not yet been fully investigated and this will be the goal of this paper.
Another important subject that should be attended is stability analysis in the presence of uncertainties, which is considered in this paper.
In this correspondence, we consider two classes of uncertain affine T-S fuzzy impulsive control systems. By using impulsive control strategy, we obtain some sufficient conditions to analyze (uniformly, asymptotically) stability of uncertain affine T-S fuzzy impulsive control systems in the presence of parametric uncertainties will be given.
The contributions of this paper are organized as follows.
After an introduction, we introduce the concepts of impulsive differential equations and then affine T-S fuzzy impulsive control system is explained in section three. In the section four, stability analysis of two classes of uncertain affine T-S fuzzy impulsive control systems are considered. Base on extended Lyapunov theory, sufficient conditions for stability analysis in the presence of parametric uncertainties are extracted in terms of matrix inequalities. Finally, results are argued in conclusion section.
II. IMPULSIVE CONTROL STRATEGY
In this section, we present the concepts and definitions of impulsive control strategy that we need to introduce affine T-S fuzzy impulsive control systems. First, we address the issues which concern the necessity of impulsive control strategy from [10] and mentioned previously in [28-30] by the authors of the paper. This part is given originally from [10]. Consider the
following impulsive functional equation
{๐ฅฬ (๐ก)= ๐(๐ก, ๐ฅ(๐ก)), ๐ก โฅ ๐ก0,
๐ฅ(๐ก๐)= ๐ผ(๐ก๐, ๐ฅ(๐ก๐โ)), ๐ โ โค+, (1a) where ๐: [๐ก0, โ) ร ๐๐ถ โ โ๐ and ๐ผ: [๐ก0, โ) ร ๐ (๐) โ โ๐. Here, ๐ (๐) = {๐ฅ(๐ก) โ โ๐: โ๐ฅ(๐ก)โ < ๐}, PC denotes the space of piecewise right-continuous function. โโโ is a norm in โn, 0 <
๐ก๐< ๐ก๐+1 with ๐ก๐โ โ as ๐ โ โ. ๐ฅฬ (๐ก) denotes the right-hand derivative of ๐ฅ(๐ก) and โค+denotes the set of all positive integers.
For stability analysis, we assume that ๐(๐ก, 0) = 0 and ๐ผ(๐ก๐, 0)=0 so that ๐ฅ(๐ก) = 0 is a solution of (1a). Motivated from the nonlinear impulsive equation (1a), the following impulsive control system (strategy) can be considered
๐ฅฬ (๐ก)= ๐(๐ก, ๐ฅ(๐ก)),
๐ฆ(๐ก) = ๐(๐ฅ(๐ก)), (1b) where ๐ฅ(๐ก) โ โ๐ is the state variable, ๐ฆ(๐ก) โ โ๐ is the output variable, ๐(๐ก, ๐ฅ(๐ก)) and ๐(๐ฅ(๐ก)) are continuous function in their respective domains of definition. An impulsive control law of (1b) is given by a sequence {๐๐, ๐ผ๐(๐ฆ(๐๐))}, where 0 < ๐1<
๐2< โฏ < ๐๐< ๐๐+1 < โฏ , ๐๐ โโ ๐๐ ๐ โโ , and ๐ผ๐(๐ฆ(๐ก)) is a continuous function which maps โm to โn for all ๐ = 1,2, โฏ which is named as โโimpulsive functionโโ. Clearly, if the solution of (1b) exists, we can rewrite (1b) as follows:
๐ฅฬ (๐ก)= ๐(๐ก, ๐ฅ(๐ก)), ๐ก โ ๐๐, ๐ฆ(๐ก) = ๐(๐ฅ(๐ก)), ๐ก โ ๐๐,
โ๐ฅ(๐ก) = ๐ผ๐(๐ฆ(๐ก)), ๐ก = ๐๐,
๐ฅ(๐ก0) = ๐ฅ0, ๐ = 1,2, โฏ. (2) where โ๐ฅ(๐๐) = ๐ฅ(๐๐+) โ ๐ฅ(๐๐โ), ๐ฅ(๐๐+) = ๐๐๐
๐กโ๐๐+๐ฅ(๐ก). We call (2) as โโimpulsive control systemโโ. Without loss of generality, we assume ๐(๐ก, 0) โก 0 and ๐(0) = 0, so that system (2) admits a trivial solution. Our impulsive control problem may now be stated formally as follow. Subject to the dynamical system (1b), find an impulsive control law {๐๐, ๐ผ๐(๐ฆ(๐๐))} such that the impulsive control system (2) is stable, uniformly stable, asymptotically stable or uniformly asymptotically stable.
Here, we denote ๐พ the class of continuous functions ๐(๐ ) โถ โ+โ โ+ such that ๐(๐ ) is strictly increasing and ๐(0) = 0; โ the class of functions ๐(๐ก, ๐ฅ(๐ก)): โ+ร โ๐โ โ+ such that ๐(๐ก, ๐ฅ(๐ก)) is positive definite, locally Lipschitzian in ๐ฅ(๐ก), continuous everywhere except possibly at a sequence of point {๐๐} at which ๐(๐ก, ๐ฅ(๐ก)) is left continuous and the right limit ๐(๐๐+, ๐ฅ(๐๐+)) exists for all ๐ฅ(๐ก) โ โ๐. We assume that there exists a ๐1โ (0, ๐) such that ๐ฅ(๐ก) โ ๐ (๐1) implies๐ฅ(๐ก) + ๐ผ๐(๐ฅ(๐ก)) โ ๐ (๐). The following theorem gives sufficient conditions for various stability criteria. For more details see [10].
Theorem 1 (Liu et al. ้่ฏฏ!ๆชๆพๅฐๅผ็จๆบใ[10]). Assume that i) There exist โkโ โ and ๐๐โ ๐พ such that
๐ท+๐(๐ก, ๐ฅ(๐ก))โคโ๐โ๐
๐๐๐(๐(๐ก, ๐ฅ(๐ก))),(๐ก, ๐ฅ(๐ก))โ (๐๐โ1, ๐๐) ร ๐ (๐),
ii) There exist ๐ฃ๐โ โ and ๐๐โ ๐พ such that ๐ (๐๐+, ๐ฅ(๐ก) + ๐ผ๐(๐ฅ(๐ก))) โค ๐(๐๐, ๐ฅ(๐ก)) + ๐ฃ๐๐๐(๐(๐๐, ๐ฅ(๐ก))) , ๐ฅ(๐ก) โ ๐ (๐) ,
iii) โ๐+ ๐ฃ๐โค 0, for ๐ โ (0, ๐), ๐๐(๐ ) โค ๐๐(๐ ) if ๐ฃ๐< 0 and ๐๐(๐ ) โค ๐๐(๐ ) if โ๐< 0.
Then the system (1b) is stable. In addition to all above condition, suppose further that ๐(๐ก, ๐ฅ(๐ก)) is deceasing and iv) For any ๐ > 0, there exist a ๐ > 0 such that
๐ + |๐ฃ๐|๐๐(๐ ) < ๐, โ๐ โ (0, ๐), โ๐ = 1,2, โฏ,
Then the system (1b) is uniformly stable. Also if (i), (ii) and (iii) and the following condition hold
โ(โ๐+ ๐ฃ๐)
โ ๐=1
๐๐(๐ฝ)= โโ, โ ๐ฝ > 0 ,
where ๐๐(๐ )= ๐๐๐ฅ{๐๐(๐ ), ๐๐(๐ )} , then system (1b) is asymptotically stable. Finally, if (i), (ii), (iii), (iv) hold and there exist positive integer ๐ such that
โ (โ๐+ ๐ฃ๐)
๐+๐ ๐=๐+1
๐๐(๐ฝ)< โ๐ถ, โ ๐ โฅ 0, ๐ฝ, ๐ถ > 0,
where ๐๐(๐ )= ๐๐๐ฅ{๐๐(๐ ), ๐๐(๐ )}, and the sequence {โ๐๐} is bounded for any ๐ฝ, ๐ถ > 0. Then, system (1b) is uniformly asymptotically stable. โ๐๐= ๐๐โ ๐๐โ1, and
๐ท+๐(๐ก, ๐ฅ(๐ก))= ๐๐๐
๐ฟโ0+๐ ๐ข๐1
๐ฟ[๐(๐ก + ๐ฟ, ๐ฅ(๐ก)+ ๐ฟ)๐(๐ก,๐ฅ(๐ก))
โ ๐(๐ก, ๐ฅ(๐ก))]
If ๐(๐ก, ๐ฅ(๐ก)) is continuously differentiable, then ๐ท+๐(๐ก, ๐ฅ(๐ก))=๐๐ก๐๐(๐ก, ๐ฅ(๐ก))+๐๐ฅ๐๐(๐ก, ๐ฅ(๐ก))โ ๐(๐ก, ๐ฅ(๐ก)).
Remark 1. If ๐๐(๐ )= ๐๐(๐ ) = ๐ , then the condition (iii) is reduced to
โ๐+ ๐ฃ๐โค 0 and ๐ฃ๐ โฅ โ1.
III. ROBUST STABILITY SUBJECT TO PARAMETRIC UNCERTAINTIES
Consider an affine T-S fuzzy impulsive control system under discussion, which has bounded parametric uncertainties as
IF ๐1 ๐๐ ๐1๐ ๐๐๐ โฏ ๐๐๐ ๐๐ ๐๐ ๐๐ ๐ THEN {๐ฅฬ = ๐ดฬ๐(๐ก)๐ฅ + ๐๐๐ฬ๐(๐ก) + ๐ตฬ๐(๐ก)๐ข
๐ข = โโ๐=1๐ฟ(๐ก โ ๐๐)๐ผ๐๐(๐ฅ) ,( ๐ = 1,2, โฏ , ๐)(3) where ๐ is the number of fuzzy rules, ๐(๐ก) is vector of premise variables such that
๐(๐ก) = [๐1(๐ก), ๐2(๐ก), โฏ , ๐๐ (๐ก)]๐ = ๐ช๐ฅ(๐ก), ๐๐๐๐(๐ช) = ๐ (1 โค ๐ โค n),
๐ฅ(๐ก) = [๐ฅ1(๐ก), ๐ฅ2(๐ก), โฏ , ๐ฅ๐(๐ก)]๐โ โ๐ is state vector at time ๐ก, ๐ is the number of states variable, (๐ดฬ๐(๐ก), ๐ตฬ๐(๐ก)) is controllable pair of system matrices, ๐ฬ๐(๐ก) is offset terms, ๐ข(๐ก) = [๐ข1(๐ก), ๐ข2(๐ก), โฏ , ๐ข๐(๐ก)]๐โ โ๐ is control input at time t with appropriate dimension, and ๐๐๐(๐ = 1,2, , โฏ , ๐, ๐ = 1,2, โฏ , ๐ ) stands for the fuzzy set of jth antecedent variable in the ith rule.
Also,
{
๐ดฬ๐(๐ก)= ๐ด๐+ โ๐ด๐(๐ก) , โ๐ด๐(๐ก)= ๐ป๐๐๐น๐๐(๐ก)๐ฟ๐๐ , ๐น๐๐๐(๐ก)๐น๐๐(๐ก)โค ๐ ๐๐
๐ตฬ๐(๐ก)= ๐ต๐+ โ๐ต๐(๐ก) , โ๐ต๐(๐ก)= ๐ป๐๐๐น๐๐(๐ก)๐ฟ๐๐ , ๐น๐๐๐(๐ก)๐น๐๐(๐ก)โค ๐ ๐๐
๐ฬ๐(๐ก)= ๐๐+ โ๐๐(๐ก) , โ๐๐(๐ก)= ๐ป๐๐๐น๐๐(๐ก)๐ฟ๐๐ , ๐น๐๐๐(๐ก)๐น๐๐(๐ก)โค ๐ ๐๐
and {โ๐ด๐(๐ก), โ๐ต๐(๐ก), โ๐(๐ก)} are the system uncertainties satisfying the norm bounded condition. ๐ป๐โ [๐ป๐๐, ๐ป๐๐, ๐ป๐๐] and ๐ฟ๐โ [๐ฟ๐๐, ๐ฟ๐๐, ๐ฟ๐๐] are known constant matrices, ๐น๐๐(๐ก), ๐น๐๐(๐ก), and ๐น๐๐(๐ก) belong to the following set
๐บ โ
{๐น(๐ก)|๐น๐(๐ก)๐น(๐ก)โค ๐ผ, element of ๐น(๐ก) are Lebesgue measurment} Based on impulsive controller techniques [28], [30], the closed- loop system can be described by
{๐ฅฬ =โ๐๐=1๐๐(๐ดฬ๐(๐ก)๐ฅ + ๐๐๐ฬ๐(๐ก)) ๐ก โ ๐๐
โ๐ฅ = ๐ฅ(๐๐+)โ ๐ฅ(๐๐โ)= ๐ผ๐(๐ฅ)=โ๐๐=1๐๐๐ตฬ๐(๐ก)๐ผ๐๐(๐ฅ)๐ก = ๐๐ (4) The rule set of the system is divided into ๐ผ0 and ๐ผ1. ๐ผ0
represents the rules which contain the origin and ๐ผ1 is the remaining rules which do not contain the origin. So, if ๐ โ ๐ผ0,
we get ๐ฬ๐= 0 which guarantee the trivial solution for ๐ฅฬ (๐ก)โก 0. By noting mentioned description we define ๐๐ as ๐๐= {0 , ๐๐ ๐ โ ๐ผ0
1 , ๐๐ ๐ โ ๐ผ1.
Our task is to design an impulsive control law {๐๐, ๐ผ๐๐(๐ฅ(๐๐))} such that the overall affine T-S fuzzy impulsive control system is stabilized (asymptotically, uniformly). For stability analysis of (4), the following theorem is given in which impulsive function (๐ผ๐๐(๐ฅ)) is considered as ๐ผ๐๐(๐ฅ) = ๐ท๐๐๐ฅ + ๐๐๐๐๐(๐ฅ) and โ๐๐๐(๐ฅ)โโค ๐๐๐โ๐ฅโ in which ๐๐๐ is a positive scalar.
Theorem 2: The origin of the affine T-S fuzzy impulsive control system (4) is stable if there exist positive definite matrix ๐, scalars โ๐'s, ๐ฃ๐'s, positive scalars โ๐๐'s, ๐๐'s, ๐๐๐'s, ๐๐๐'s, and matrices ๐ฃ๐๐'s such that the following conditions hold
โ๐+ ๐ฃ๐โค 0 , ๐ฃ๐โฅ โ1, (5a) for ๐ โ ๐ผ0
(
โณ๐๐๐ โ โ
โ๐ โ๐๐๐๐๐ โ ๐๐๐โ๐๐ 0 โ๐๐๐๐ผ๐
)โค 0, ๐ = 1,2, (5b) for ๐ โ ๐ผ1
( โณ๐๐๐ โ โ
โ๐ โ๐๐๐๐๐ โ ๐๐๐โ๐๐ 0 โ๐๐๐๐ผ๐
)โค 0, ๐ = 3,4, (5c) where
โณ๐๐1 = ๐๐ด๐๐ + ๐ด๐๐ โโ๐๐๐
๐๐, โ1= ๐ป๐๐, โ1= ๐ฟ๐๐๐,๐1= ๐, โณ๐๐2 = (๐ต๐๐ฃ๐๐+ ๐ฃ๐๐๐๐ต๐๐โ ๐ฃ๐๐ โ
๐ฃ๐๐๐๐ต๐๐ โ๐) , โ2= (๐ป๐๐ ๐ป๐๐ 0 0 ) , โ2= ๐๐๐๐(๐ฟ๐๐๐ฃ๐๐, ๐ฟ๐๐๐ฃ๐๐),๐2= ๐๐๐๐(๐, ๐),
โณ๐๐3 = (๐๐ด๐๐ + ๐ด๐๐ โโ๐๐๐
๐๐ โ
๐๐๐+ ๐๐๐ฅ๐๐๐๐๐๐๐ ๐๐๐๐
), โ3= (๐ป๐๐ ๐ป๐๐
0 0 ), โ3= ๐๐๐๐(๐ฟ๐๐๐, ๐ฟ๐๐), ๐3= ๐๐๐๐(๐, ๐),
โณ๐๐4 = (
๐บฬ๐๐๐ โ โ โ โ
๐ โ๐พ๐๐๐ผ โ โ โ
๐ 0 โ(1 + ๐๐๐)๐ โ โ
๐๐๐ฅ๐๐๐๐๐๐๐ 0 0 ๐๐๐๐ โ
๐ต๐๐ฃ๐๐ 0 ๐ 0 โ๐)
,
โ4= ๐๐๐๐(๐ฟ๐๐๐ฃ๐๐, 0,0,0,0), ๐4= ๐๐๐๐(๐, ๐, ๐, ๐, ๐)
โ4= (
๐ป๐๐ โ โ โ 0
0 0 โ โ โ
0 0 0 โ โ
0 0 0 0 โ
๐ป๐๐ 0 0 0 0) ,
๐ผ๐ is identity matrix with appropriate dimension.
Then ๐ท๐๐= ๐ฃ๐๐๐โ1, ๐๐= โ๐๐+ ๐๐โ1(๐0= ๐ก0), and ๐๐๐(๐ฅ) is any continuous function in respect to ๐ฅ such that โ๐๐๐(๐ฅ)โ โค ๐๐๐โ๐ฅโ.
Proof. Consider the Lyapunov function ๐(๐ก, ๐ฅ) = ๐ฅ๐๐๐ฅ for the uncertain affine T-S fuzzy impulsive control system (4). Now, from Theorem 1, Remark 1, and by taking the upper right-hand
generalized derivative of the Lyapunov function along the trajectories of the system (4), the following is obtained ๐ท+๐(๐ก, ๐ฅ) โ โ๐
โ๐๐๐ฅ๐๐๐ฅ
= ๐ฅฬ๐๐๐ฅ + ๐ฅ๐๐๐ฅฬ โ โ๐
โ๐๐๐ฅ๐๐๐ฅ
= โ ๐๐(๐ดฬ๐(๐ก)๐ฅ + ๐๐๐ฬ๐(๐ก))๐๐๐ฅ
๐
๐=1
+ โ๐๐=1๐๐๐ฅ๐๐ (๐ดฬ๐(๐ก)๐ฅ + ๐๐๐ฬ๐(๐ก))โโ๐โ๐
๐๐ฅ๐๐๐ฅ (6) If ๐ โ ๐ผ0(i. e. ๐๐= 0), we can show if the following term is negative then ๐ท+๐(๐ก, ๐ฅ) โโ๐โ๐
๐๐ฅ๐๐๐ฅ < 0. ๐๐ดฬ๐๐(๐ก) + ๐ดฬ๐(๐ก)๐ โ ๐๐
โ๐๐๐
= ๐๐ด๐๐+ ๐ด๐๐ + ๐(๐ป๐๐๐น๐๐(๐ก)๐ฟ๐๐)๐ +๐ป๐๐๐น๐๐(๐ก)๐ฟ๐๐๐ โ ๐๐
โ๐๐๐
= โณ๐๐1 + โ1โฑ1(๐ก)โ1+ โ1๐โฑ1(๐ก)๐โ1๐, (7) where โฑ1(๐ก) = ๐น๐๐(๐ก), ๐ดฬ๐๐(๐ก) = ๐ด๐+ ๐ป๐๐๐น๐๐(๐ก)๐ฟ๐๐. By using Lemma A.1 (๐ = ๐โ1) and Schur's complement, it is easy to see that inequality (5b) (โ ๐ = 1) implies (7) is negative.
In a similar manner, also if, we get (๐ตฬ๐(๐ก)๐ฃ๐๐+ ๐ฃ๐๐๐๐ตฬ๐(๐ก)๐โ ๐ฃ๐๐ โ
๐ฃ๐๐๐๐ตฬ๐(๐ก)๐ โ๐)
= โณ๐๐2 + (๐ป๐๐๐น๐๐(๐ก)๐ฟ๐๐๐ฃ๐๐+ ๐ฃ๐๐๐(๐ป๐๐๐น๐๐(๐ก)๐ฟ๐๐)๐ โ ๐ฃ๐๐๐(๐ป๐๐๐น๐๐(๐ก)๐ฟ๐๐)๐ 0)
= โณ๐๐2 + โ2โฑ2(๐ก)โ2+ โ2๐โฑ2(๐ก)๐โ2๐ (8) where โฑ2(๐ก) = ๐๐๐๐ (๐น๐๐(๐ก), ๐น๐๐(๐ก)) , ๐ตฬ๐๐(๐ก) = ๐ต๐+ ๐ป๐๐๐น๐๐(๐ก)๐ฟ๐๐. By using Lemma A.1 (๐ = (๐๐๐๐(๐, ๐))โ1) and Schur's complement, we can conclude that (5b) (โ ๐ = 2) implies (8) is negative.
Now, consider ๐ โ ๐ผ1(๐. ๐. ๐๐= 1); Because ๐ท+๐(๐ก, ๐ฅ) โ
โ๐
โ๐๐๐ฅ๐๐๐ฅ has to be given in terms of matrix inequalities, by following ้ ่ฏฏ!ๆช ๆพ ๅฐ ๅผ ็จ ๆบ ใ[31], positive scalars
โ๐โ๐ผ1๐๐๐๐(1 โ ๐ฅ๐๐๐๐๐ฅ + ๐ฅ๐๐๐๐๐ฅ๐๐+ ๐ฅ๐๐๐๐๐๐๐ฅ โ ๐ฅ๐๐๐๐๐๐๐ฅ๐๐) are added to (6). This implies that each rule of ๐ผ1 is encircled by a hyper ellipsoid in which ๐๐ is a positive scalar and (1 โ ๐ฅ๐๐๐๐๐ฅ + ๐ฅ๐๐๐๐๐ฅ๐๐+ ๐ฅ๐๐๐๐๐๐๐ฅ โ ๐ฅ๐๐๐๐๐๐๐ฅ๐๐) is the definition of the hyper ellipsoid which includes the region of the ๐th rule (๐ โ ๐ผ1). In here, ๐๐๐ is the positive definite matrix. Therefore, we get
๐ท+๐(๐ก, ๐ฅ) โ โ๐
โ๐๐๐ฅ๐๐๐ฅ = ๐ฅฬ๐๐๐ฅ + ๐ฅ๐๐๐ฅฬ โ โ๐
โ๐๐๐ฅ๐๐๐ฅ
= โ ๐๐(๐ด๐๐ฅ + ๐๐๐๐)๐๐๐ฅ
๐
๐=1
+ โ ๐๐๐ฅ๐๐(๐ด๐๐ฅ + ๐๐๐๐)
๐ ๐=1
+ โ ๐๐๐๐(1 โ ๐ฅ๐๐๐๐๐ฅ + ๐ฅ๐๐๐๐๐ฅ๐๐+ ๐ฅ๐๐๐๐๐๐๐ฅ โ ๐ฅ๐๐๐๐๐๐๐ฅ๐๐)
๐โ๐ผ1
โ โ๐
โ๐๐๐ฅ๐๐๐ฅ
(9) Then for ๐ โ ๐ผ1, if ( ๐ฬ๐๐ โ
๐๐๐+ ๐๐๐ฅ๐๐๐๐๐๐๐ ๐๐๐๐) < 0, we can get (๐๐ดฬ๐๐(๐ก) + ๐ดฬ๐(๐ก)๐ โ ๐๐
โ๐๐๐ โ ๐ฬ๐๐(๐ก) + ๐๐๐ฅ๐๐๐๐๐๐๐ ๐๐๐๐
)
= โณ๐๐3 + (๐(๐ป๐๐๐น๐๐(๐ก)๐ฟ๐๐)๐+ ๐ป๐๐๐น๐๐(๐ก)๐ฟ๐๐๐ โ (๐ป๐๐๐น๐๐(๐ก)๐ฟ๐๐)๐ 0)
= โณ๐๐3 + โ3โฑ3(๐ก)โ3+ โ3๐โฑ3(๐ก)๐โ3๐ (10) where โฑ3(๐ก) = ๐๐๐๐ (๐น๐๐(๐ก), ๐น๐๐(๐ก)) , ๐ฬ๐๐(๐ก) = ๐๐+ ๐ป๐๐๐น๐๐(๐ก)๐ฟ๐๐. By using Lemma A.1 (๐ = (๐๐๐๐(๐, ๐))โ1) and Schur's complement, it is easy to see that (5c) (โ ๐ = 3) implies (10) is negative.
Now, for ๐ โ ๐ผ1 , we get ๐(๐๐+, ๐ฅ + ๐ผ๐(๐ฅ)) โ ๐(๐๐, ๐ฅ) + ๐ฃ๐๐๐(๐(๐๐, ๐ฅ)) and By repeating the same manner, we get
(
(๐ตฬ๐(๐ก)๐ฃ๐๐+ ๐ฃ๐๐๐๐ตฬ๐(๐ก)๐
โ๐ฃ๐๐ ) โ โ โ โ
๐ โ๐พ๐๐๐ผ โ โ โ
๐ 0 โ(1 + ๐๐๐)๐ โ โ
๐๐๐ฅ๐๐๐๐๐๐๐ 0 0 ๐๐๐๐ โ
๐ตฬ๐(๐ก)๐ฃ๐๐ 0 ๐ 0 โ๐)
= โณ๐๐4 +
(
( ๐ป๐๐๐น๐๐(๐ก)๐ฟ๐๐๐ฃ๐๐
+๐ฃ๐๐๐(๐ป๐๐๐น๐๐(๐ก)๐ฟ๐๐)๐) โ โ โ โ
0 0 โ โ โ
0 0 0 โ โ
0 0 0 0 โ
๐ป๐๐๐น๐๐(๐ก)๐ฟ๐๐๐ฃ๐๐ 0 0 0 0)
= โณ๐๐4 + โ4โฑ4(๐ก)โ4+ โ4๐โฑ4(๐ก)๐โ4๐, (11) where โฑ4(๐ก) = ๐๐๐๐(๐น๐๐(๐ก), 0,0,0,0) . Eq. (5c) (โ ๐ = 4) implies (11) is negative.
Also based on condition (ii) of Theorem 1 and by assuming ๐๐(๐ ) = ๐๐(๐ ) = ๐ , we get
๐(๐๐+, ๐ฅ + ๐ผ๐(๐ฅ)) โ ๐(๐๐, ๐ฅ) โ ๐ฃ๐๐๐(๐(๐๐, ๐ฅ))
= (๐ฅ + ๐ผ๐(๐ฅ))๐๐(๐ฅ + ๐ผ๐(๐ฅ)) โ ๐(๐๐, ๐ฅ) โ ๐ฃ๐๐๐(๐(๐๐, ๐ฅ))
= ๐ฅ๐๐๐ฅ + ๐ฅ๐๐๐ผ๐(๐ฅ) + ๐ผ๐(๐ฅ)๐๐๐ฅ + ๐ผ๐(๐ฅ)๐๐๐ผ๐(๐ฅ) โ ๐ฅ๐๐๐ฅ โ ๐ฃ๐๐ฅ๐๐๐ฅ, (12)
By considering ๐ผ๐(๐ฅ) = โ ๐๐๐=1 ๐๐ตฬ๐(๐ก)๐ผ๐๐(๐ฅ) , and the proof of Theorems in [14] and [30], for ๐ โ ๐ผ0, it can be shown that (5b) yields to ๐(๐๐+, ๐ฅ + ๐ผ๐(๐ฅ)) โ ๐(๐๐, ๐ฅ) + ๐ฃ๐๐๐(๐(๐๐, ๐ฅ)) is negative and similarly to , for ๐ โ ๐ผ1, we can conclude that (5c) yields to ๐(๐๐+, ๐ฅ + ๐ผ๐(๐ฅ)) โ ๐(๐๐, ๐ฅ) + ๐ฃ๐๐๐(๐(๐๐, ๐ฅ)) is negative. The proof is now completed.
Now, consider a PDC based affine T-S fuzzy impulsive control system [28] as follows:
{
๐ฅฬ(๐ก) = โ๐๐(๐ดฬ๐(๐ก)๐ฅ + ๐๐๐ฬ๐(๐ก))
๐ ๐=1
, ๐ก โ ๐๐
โ๐ฅ = ๐ฅ(๐๐+) โ ๐ฅ(๐๐โ) = ๐ผ๐(๐ฅ) = โ โ ๐๐
๐ ๐=1
๐๐(๐ตฬ๐(๐ก)๐ผ๐๐(๐ฅ))
๐ ๐=1
, ๐ก = ๐๐
(10) The stability conditions of PDC based affine T-S fuzzy impulsive control system (10) with linear impulsive function (๐ผ๐๐(๐ฅ) = ๐ท๐๐๐ฅ), can now be summarized by the following theorem.
Theorem 3: The origin of the PDC-based affine T-S fuzzy impulsive control system (10) is stable if there exist positive definite matrices ๐, scalars โ๐'s, ๐ฃ๐'s, positive scalars โ๐๐'s, ๐๐'s, ๐๐๐'s, ๐๐๐'s, and matrices ๐ฃ๐๐'s such that (5a) and the following conditions hold
for ๐ โ ๐ผ0
(5b), โ๐ = 1, for ๐ โ ๐ผ1
(5c), โ๐ = 3,
for (๐, ๐) โ {(๐, ๐)|1 โค ๐ โค ๐ โค ๐, } (
โณ๐๐5 โ โ
โ5 โ๐๐5๐5 โ ๐๐5โ5๐ 0 โ๐๐5๐ผ5
) < 0, (11a)
๐ฏ = (๐11 โฏ ๐1๐
โฎ โฑ โฎ
๐1๐ โฏ ๐๐๐
) < 0, (11b) where
โณ๐๐5 = ( (
๐ต๐๐ฃ๐๐+ ๐ฃ๐๐๐๐ต๐๐โ 2๐ฃ๐๐ +๐ต๐๐ฃ๐๐+ ๐ฃ๐๐๐๐ต๐๐โ ๐โ2๐๐๐
) โ โ
๐๐ต๐๐ฃ๐๐ โ๐ โ
๐๐ต๐๐ฃ๐๐ 0 โ๐)
โ5= (โ51 โ51), โ5= (โโ5152) โ51= (
๐ป๐๐ 0 0
0 0 0
๐๐ป๐๐ 0 0) , โ52= (
๐ป๐๐ 0 0 ๐๐ป๐๐ 0 0
0 0 0
),
โ51= ๐๐๐๐ (๐ฟ๐๐๐ฃ๐๐, 0,0), โ52= ๐๐๐๐ (๐ฟ๐๐๐ฃ๐๐, 0,0) , ๐5= ๐๐๐๐(๐, ๐, ๐, ๐, ๐, ๐),
then ๐ท๐๐= ๐ฃ๐๐๐โ1, ๐๐ = โ๐๐+ ๐๐โ1(๐0= ๐ก0).
All notations are similar to Theorem 2.
Proof. Similar to the proof of Theorem 2, we recall that
( (
๐ตฬ๐(๐ก)๐ฃ๐๐+ ๐ฃ๐๐๐๐ตฬ๐(๐ก)๐โ 2๐ฃ๐๐ +๐ตฬ๐(๐ก)๐ฃ๐๐+ ๐ฃ๐๐๐๐ตฬ๐(๐ก)๐โ ๐โ2๐๐๐
) โ โ
๐๐ตฬ๐(๐ก)๐ฃ๐๐ โ๐ โ
๐๐ตฬ๐(๐ก)๐ฃ๐๐ 0 โ๐)
= โณ๐๐5 +
( (
๐ป๐๐๐น๐๐(๐ก)๐ฟ๐๐๐ฃ๐๐+ ๐ฃ๐๐๐(๐ป๐๐๐น๐๐(๐ก)๐ฟ๐๐)๐
+๐ป๐๐๐น๐๐(๐ก)๐ฟ๐๐๐ฃ๐๐+ ๐ฃ๐๐๐(๐ป๐๐๐น๐๐(๐ก)๐ฟ๐๐)๐) โ โ ๐๐ป๐๐๐น๐๐(๐ก)๐ฟ๐๐๐ฃ๐๐ 0 โ
๐๐ป๐๐๐น๐๐(๐ก)๐ฟ๐๐๐ฃ๐๐ 0 0)
= โณ๐๐5 + โ5โฑ5(๐ก)โ5+ โ5๐โฑ5(๐ก)๐โ5๐ (12) where โฑ5(๐ก) = ๐๐๐๐ (โฑ51(๐ก), โฑ52(๐ก)), โฑ51(๐ก) = ๐๐๐๐(๐น๐๐(๐ก), 0,0), and โฑ52(๐ก) = ๐๐๐๐ (๐น๐๐(๐ก), 0,0).
By using Lemma A.1 (๐ = (๐๐๐๐(๐, ๐, ๐, ๐, ๐, ๐))โ1) and Schur's complement, (11a) and (11b) imply (12) is negative.
Regarding the proof of Theorem 2, the above proof is now completed.
IV. ILLUSTRATIVE EXAMPLES
In this section, a numerical example is presented to verify the results of the proposed stabilization procedure of the affine T-S fuzzy impulsive control system. Based on proposed method, Theorem 3 is applied for a system given by the following T-S fuzzy system as follow
Rule๐: ๐ผ๐น ๐ฅ1 ๐๐ ๐1๐ ๐๐๐ ๐ฅ2 ๐๐ ๐2๐ ๐๐ป๐ธ๐
{
๐ฅฬ = ๐ดฬ๐(๐ก)๐ฅ + ๐๐๐ฬ๐(๐ก) , (๐ = 1,2,3).
๐ข = โ ๐ฟ(๐ก โ ๐๐)๐ผ๐๐(๐ฅ)
โ ๐=1
which yields to
{
๐ฅฬ (๐ก)=โ๐๐(๐ดฬ๐(๐ก)๐ฅ + ๐๐๐ฬ๐(๐ก))
3 ๐=1
, ๐ก โ ๐๐
โ๐ฅ = ๐ฅ(๐๐+)โ ๐ฅ(๐๐โ)= ๐ผ๐(๐ฅ) =โ โ๐๐
๐ ๐=1
๐๐(๐ตฬ๐(๐ก)๐ผ๐๐(๐ฅ))
๐ ๐=1
, ๐ก = ๐๐
where
๐ดฬ1=[๐ฟ1 ๐ฟ1
โ๐ฟ2 โ4], ๐ดฬ2=[๐ฟ3 ๐ฟ2
0 2] , ๐ดฬ3=[๐ฟ1 3
โ1 ๐ฟ3], ๐ฬ1=[0
โ1], ๐ฬ2=[0
0], ๐ฬ3=[1 0].
The normalized membership functions of subsystem 1 are shown in Fig. 1. The uncertainties are considered as follows. It is also assumed that ๐ดฬ๐๐
= ๐ด๐๐+ ๐ป๐๐๐ ๐น๐๐๐ ๐ฟ๐๐๐ , where ฮด1=[(1 โ 0.25%)(1 + 0.25%)],
ฮด2=[(2
โ3โ 10%) (2
โ3โ 10%)], ฮด3=[(0 โ 0.5%)(0 + 0.5%)]
and
๐ด1=[1 2 3โ
โ1 โ4] , ๐ด2=[2 2 3โ
0 2 ], ๐ด3=[1 3
โ1 2] ๐น๐1= ๐๐๐๐(๐1, ๐2) , ๐น๐2=[0 ๐1
๐2 0], ๐น๐3= ๐๐๐๐(๐1, ๐3) ๐ป๐1=[0.25 0
0 0.1] , ๐ป๐2=[0.1 0.4
0 0 ], ๐ป๐3=[0.25 0 0 0.4] ๐ฟ๐1=[1 1
1 0], ๐ฟ๐2= ๐ฟ๐3=[1 0 0 1]
where ๐๐, ๐ = 1, โฏ ,5 are random numbers on interval [โ1, 1]. Now by using the MATLAB LMI Toolbox, Theorem 3, the following solution is obtained.
๐ = ( 2.1630 โ0.0112
โ0.0112 2.0250 ) โ๐= 0.98, ๐ฃ๐= โ0.998 (1
โ๐๐
โ )= 1.0๐ + 004 ร[2.6313 2.6313]. ๐ต1๐ท1๐=[โ0.9837 0.0020
0.0020 โ0.9774] ๐ต2๐ท2๐=[โ0.8849 0.0031
0.0031 โ0.8776] ๐ต3๐ท3๐=[โ0.8042 0.0039
0.0039 โ0.7998], ๐ต4๐ท4๐=[โ0.8197 0.0007
0.0007 โ0.8215].
CONCLUSION
In this paper, a new approach based on extended Lyapunov theory is proposed to stabilize the uncertain affine T-S fuzzy impulsive control systems. Two classes of uncertain affine T-S fuzzy impulsive control systems have been presented and it is shown that under some sufficient conditions, impulsive controller can be developed to stabilize uncertain affine T-S fuzzy systems. It has been also shown that the stabilization parameters can be determined by solving a set of matrix inequalities. Through this conditions, there is no need to set pre- defined controller parameters to solve matrix inequalities where there solutions indicates the stability (uniformly, asymptotically) of affine T-S fuzzy systems.
APPENDIX
Lemma A.1 (Xie [32]). Given matrices ๐, ๐ป, ๐ , ๐ธ of appropriate dimensions with ๐ = ๐๐ , ๐ = ๐ ๐ and ๐ > 0 then
๐ + ๐ป๐น๐ธ + ๐ธ๐๐น๐๐ป๐ < 0,
For all F satisfying ๐น๐๐น < ๐ , if and only if there exists some ฯต > 0 such that๐ + ๐๐ป๐ป๐+ ๐โ1๐ธ๐๐ ๐ธ < 0
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