Delay-dependent robust stability of uncertain fuzzy large-scale systems with time-varying delays

This paper addresses the stability problem of fuzzy large-scale systems (FLSSs) with uncertainties and arbitrary time-varying delays. The stability conditions, which are less conservative and more applicable than the existing results, are derived by a novel Lyapunov-Krasovskii functional method and expressed in terms of linear matrix inequalities (LMIs). Two examples are given to demonstrate the correctness and advantage of our theoretical results.     

Stability analysis of neutral systems with mixed delays

The stability of neutral systems with mixed delays is studied in this paper. A new discretized Lyapunov functional method is proposed. The method in this paper is less conservative than the existing ones and the results are very close to the analytical results. In addition, this method allows the coefficient matrix of the neutral term to have time-varying uncertainties.     

混合变时滞不确定中立型系统鲁棒稳定性分析

研究一类含混合变时滞不确定中立系统时滞相关鲁棒稳定性问题。基于时滞中点值,把时滞区间均分成两部分,通过构造包含时滞中点信息的增广泛函和三重积分项的Lyapunov-Krasovskii (L-K)泛函,利用L-K稳定性定理、积分不等式方法和自由权矩阵技术,建立了一种基于线性矩阵不等式(LMI)的、与离散时滞和中立时滞均相关的鲁棒稳定性判据。数值算例表明,该判据改善了已有文献的结论,具有更低的保守性。     

Stability analysis of neutral systems with distributed delays

The stability of neutral systems with distributed delays is investigated in this paper. A modified Lyapunov-Krasovskii functional is constructed to study this class of systems. The proposed stability criterion is discrete-, distributed- and neutral-delay-dependent. In addition, by this method one can study the case when the coefficient matrix of the neutral delay term is time-varying uncertain. The reduced conservatism is illustrated in a numerical example.     

Stability problem of systems with multiple delay channels

A new form of coupled differential-difference equations with one delay in each channel is proposed to model systems with multiple delays. This formulation has significant advantage over the traditional differential-difference equations or the prevailing form of coupled differential-difference equations with multiple delays. Fundamental solutions, general solutions, and the construction of the Lyapunov-Krasovskii functional are discussed. For systems with a large number of state variables with multiple low-dimensional delay elements, this formulation allows a drastic reduction of computational cost as compared to the traditional differential-difference equation formulation when the discretized Lyapunov-Krasovskii functional method is used.     

采用双交叠模糊分划的T-S模糊系统的稳定性分析

研究前件变量采用双交叠模糊分划的T-S模糊系统的稳定性问题．首先针对自由系统,将连续时间系统的、基于最大交叠规则组的稳定性分析方法推广应用于离散时间系统,并采用模糊Lyapunov方法得到了稳定性的新结论．采用非并行分布补偿控制律,针对受控系统也得到了相应的结论．这些结论比已有的结果更加宽松．仿真例子验证了该稳定性结论．     

Stability analysis of large-scale systems with delays

New sufficient conditions for delay-independent asymptotic stability of large-scale systems are presented by using the properties of matrix norm and measure. The proposed method is simple and effective.     

时滞非线性随机大系统的指数稳定性

建立了一般随机泛函微分方程p阶均值指数稳定与几乎必然指数稳定的新型判据, 然后应用所得判据到具有可变多时滞的非线性随机大系统, 得到了这种随机大系统时滞无关的均方指数稳定与几乎必然指数稳定的代数判据.     

Lyapunov-Krasovskii functional for uniform stability of coupled differential-functional equations

This article discusses the Lyapunov-Krasovskii functional approach for the stability problem of coupled differential-functional equations. Such systems include, as special cases, many types of time-delay systems, including the lossless propagation model, some neutral time-delay systems and singular time-delay systems. After the general stability theory, the special case of coupled differential-difference equations is discussed, and the necessity for the existence of quadratic Lyapunov-Krasovskii functional is established. Discretization is used to render the stability criterion to an LMI form.     

Stability analysis of systems with stochastically varying delays

A stability analysis of linear systems with stochastically varying delay is performed. It is assumed that the delay function has the form of a sawtooth with switches occurring at the arrival times of a homogeneous Poisson process. Several notions of stochastic stability are considered and corresponding stability criteria are derived. For two examples the different criteria are compared and the effect on stability of various deterministic approximations is examined.     

Linear quadratic suboptimal control for time delays systems

A simple method is developed for determining an output feedback matrix which places m+l—?1 poles of a linear multivariate system at any specified locations, where m and l are the input and output dimensions respectively. The feedback matrix is constructed as the sum of two unity rank matrices. The first places m— 1 poles and the second, while preserving these m— 1 poles, places I additional poles. A numerical example is given for illustration.     

带有混合时滞的切换系统的耗散性分析与控制

本文研究了一类具有不稳定子系统和混合时滞的切换系统的耗散性和指数镇定问题. 首先, 为了消除不稳 定子系统给这类时滞系统带来的不利影响, 采用了一种新颖的切换信号设计方法–将模态依赖平均驻留时间的慢切 换和快切换方法相结合, 并通过利用Lyapunov相关理论, 给出了全局指数稳定的充分条件. 然后, 利用耗散性理 论、多重Lyapunov-Krasovskii泛函技术、积分不等式、与Schur补引理等方法, 以线性矩阵不等式的形式给出了耗散 性能的相关判据, 使闭环系统实现全局指数稳定性的同时具有严格耗散性能. 进一步, 在给定扰动衰减水平的前提 下, 通过求解一些严格的LMI条件, 建立了一组可行控制器. 最后, 通过仿真实例验证了该方法的有效性.     

Stability of stochastic interval systems with time delays

Consider a given exponentially stable system undergoing a random perturbation which is dependent on a past state of the solution of the system. Suppose this stochastically perturbed system is described by a stochastic differential-functional equation. In this paper, we establish a sufficient condition that the perturbed system remains exponentially stable. Using a specific example, we show how this condition may be used, and we extend it to deal with multiple time delays.     

PID controller design for fractional-order systems with time delays

Classical proper PID controllers are designed for linear time invariant plants whose transfer functions are rational functions of s^α, where 0<α<1, and s is the Laplace transform variable. Effect of input-output time delay on the range of allowable controller parameters is investigated. The allowable PID controller parameters are determined from a small gain type of argument used earlier for finite dimensional plants.     

Stability of stochastic systems with uncertain time delays

For linear delay systems with bilinear noise sufficient conditions are given for the global asymptotic stochastic stability independent of the length of the delay(s). For linear stochastic noise terms, sufficient conditions for the existence of an invariant distribution, for all values of the delay are given. It is shown that the gaussian distribution is the unique invariant distribution. The covariance and correlation matrix function of the resulting stationary process are completely characterized by a Lyapunov-type equation. All these sufficient conditions are obtained in the form of the existence of some positive definite matrices satisfying certain Riccati-type equations.     

Decentralized adaptive tracking control of nonaffine nonlinear large-scale systems with time delays

This paper addresses the problem of decentralized tracking control of large-scale systems with uncertain nonaffine nonlinear isolated subsystems and nonlinear interconnections with time-varying delays. Based on Lyapunov-Krasovskii functional approach and implicit function theorem, a delay-independent decentralized tracking controller is proposed. Due to functional approximation capability of fuzzy logic systems (FLS), neither strict structure restrictions on the isolated subsystems nor a priori knowledge of the strong interconnections with time-varying delays is required in our control design. Furthermore, transient performance of the resulting closed-loop system is also addressed under an analytical framework. Finally, two numerical examples are provided to show the effectiveness of the proposed controller.     

Stability connection between sampled-data fuzzy control systems with quantization and their approximate discrete-time model

This paper concerns the stability of a sampled-data Takagi-Sugeno (T-S) fuzzy control system with quantization, when a controller design is based on an approximate discrete-time model of the plant without quantization. The motivations come from the facts that digital devices for interfacing a plant with a controller quantize signals and an exact discrete-time model of the T-S fuzzy system is generally not amenable to synthesis process. We show that the concerned system is Lagrange stabilizable by the controller asymptotically stabilizing the approximate discrete-time model. A constructive design algorithm for the developed stability analysis is proposed in terms of linear matrix inequalities.     

多输入多输出非线性多时滞系统的直接自适应模糊跟踪控制

针对多输入多输出非线性多时滞系统,提出了一种直接自适应模糊跟踪控制方案．该方案有机综合了自适应控制和H∞ 控制,构建了一种自适应时滞模糊逻辑系统用来逼近有多重时滞的未知函数;设计了H∞ 补偿器来抵消模糊逼近误差和外部扰动．根据跟踪误差给出了参数调节规律,构造了包含时滞的李亚普诺夫函数,从而证明了误差闭环系统满足期望的H∞ 跟踪性能．仿真结果表明了该方案的可行性．     

时滞系统稳定性分析:一种积分等式方法

提出一种积分等式方法研究时滞系统稳定性问题.该方法是已有积分不等式方法的改进.结合自由权矩阵构建积分等式,且自由权矩阵的选取由Lyapunov-Krasovskii泛函的导数确定,从而在稳定条件的推导过程中,不引入任何模型转换及限界方法.基于该方法,可得到具有更低保守性的稳定条件.仿真例子说明了所提方法的有效性.     

带有非线性扰动的时变时滞系统的稳定性准则

研究了带有非线性扰动的时变时滞系统的稳定性问题.基于时滞分割方法,提出了保守性更小的系统稳定性分析准则.利用一个自由参数将时滞区间分割为2个子区间,进而构造了含有时滞分割点状态信息和3重积分项的Lyapunov-Krasovskii泛函,并采用自由矩阵积分不等式界定泛函导数中的交叉项.基于Lyapunov稳定性定理,得到了以线性矩阵不等式描述的时滞相关型稳定性准则.数值算例表明该稳定性准则能够得到更大的时滞上界,与已有结果相比具有更小的保守性.