Non-Monotonic Lyapunov-Krasovskii Functional Approach to Stability Analysis and Stabilization of Discrete Time-Delay Systems

In this paper, a novel non-monotonic Lyapunov-Krasovskii functional approach is proposed to deal with the stability analysis and stabilization problem of linear discrete time-delay systems. This technique is utilized to relax the monotonic requirement of the Lyapunov-Krasovskii theorem. In this regard, the Lyapunov-Krasovskii functional is allowed to increase in a few steps, while being forced to be overall decreasing. As a result, it relays on a larger class of Lyapunov-Krasovskii functionals to provide stability of a state-delay system. To this end, using the non-monotonic Lyapunov-Krasovskii theorem, new sufficient conditions are derived regarding linear matrix inequalities(LMIs)to study the global asymptotic stability of state-delay systems.Moreover, new stabilization conditions are also proposed for time-delay systems in this article. Both simulation and experimental results on a p H neutralizing process are provided to demonstrate the efficacy of the proposed method.

A new approach to stability analysis of neural networks with time-varying delay via novel Lyapunov-Krasovskii functional

In this paper, new delay-dependent stability criteria for asymptotic stability of neural networks with time-varying delays are derived. The stability conditions are represented in terms of linear matrix inequalities （LMIs） by constructing new Lyapunov-Krasovskii functional. The proposed functional has an augmented quadratic form with states as well as the nonlinear function to consider the sector and the slope constraints. The less conservativeness of the proposed stability criteria can be guaranteed by using convex properties of the nonlinear function which satisfies the sector and slope bound. Numerical examples are presented to show the effectiveness of the proposed method.

New Approach of Stability for Time-Delay Takagi-Sugeno Fuzzy System Based on Fuzzy Weighting-Dependent Lyapunov Functionals

This paper deals with the stability of Takagi-Sugeno fuzzy models with time delay. Using fuzzy weighting- dependent Lyapunov-Krasovskii functionals, new sufficient stability criteria are established in terms of Linear Matrix Inequality;hence the stability bound of upper bound delay time can be easily estimated. Finally, numeric simulations are given to validate the developed approach.

连续广义时滞系统L-K泛函

连续广义时滞系统容许性的研究,通过构造具有一定结构的Lyapunov-Krasovskii泛函(简称L-K泛函),对泛函求导,利用一些积分不等式处理泛函求导后的某些积分项,得到以线性矩阵不等式(简称LMI)给出的容许性条件。综合已有的相关研究成果,一方面总结归纳了L-K泛函形式:双重积分型、多重积分型、增广型以及松弛型;另一方面列举比较了几种处理L-K泛函求导后产生积分项常用的积分不等式:Jensen积分不等式、Wirtinger积分不等式、辅助函数积分不等式以及Bessel-Legendre积分不等式(简称B-L积分不等式)。运用这些积分不等式的目的是以LMI的形式给出连续广义时滞系统容许性条件,利于Matlab求解。并且,对这些积分不等式的放缩程度进行比较,因为这直接关系到连续广义时滞系统容许性条件的保守性。

一类综合控制系统的动态输出反馈H_(∞)控制器设计

基于稳定性分析理论,利用线性矩阵不等式方法和交叉项界定法,设计无记忆和记忆的动态输出反馈H_(∞)控制器,构造新的Lyapunov-Krasovskii(L-K)泛函,推出动态输出反馈控制在满足H_(∞)性能指标条件下渐近稳定的充分性判据,所得定理适用于标准和非标准情形.通过算例验证控制方法有效.

Input-to-State Stability of Switched Nonlinear Delay Systems Based on a Novel Lyapunov-Krasovskii Functional Method

In this paper, the input-to-state stability （ISS） analysis is addressed for switched nonlinear delay systems. By introducing a novel Lyapunov-Krasovskii functional with indefinite derivative and the merging switching signal techniques, some new- criteria are established for switched nonlinear delay systems under asynchronous switching, which extends the existing results to the nonlinear systems with switching rules and delays. The ISS problem is also considered under synchronous switching for switched nonlinear systems by employing the similar techniques. Finally, a nonlinear delay model is provided to show the effectiveness of the proposed results.

New Lyapunov-Krasovskii Functional for Stability Analysis of Linear Systems with Time-Varying Delay

This paper focuses on the problem of delay-dependent stability of linear systems with time-varying delay.A new delay-product-type augmented Lyapunov-Krasovskii functional(LKF)is constructed.Based on the LKF and by employing a generalized free-matrix-based integral inequality,less conservative delay-dependent stability criteria are obtained.Finally,two well-known numerical examples are used to confirm the effectiveness and the superiority of the presented stability criteria.

Event-triggered state estimation for T-S fuzzy affine systems based on piecewise Lyapunov-Krasovskii functionals

This paper investigates the problem of event-triggered H∞state estimation for Takagi-Sugeno (T-S) fuzzy affine systems. The objective is to design an event-triggered scheme and an observer such that the resulting estimation error system is asymptotically stable with a prescribed H∞performance and at the same time unnecessary output measurement transmission can be reduced. First, an event-triggered scheme is proposed to determine whether the sampled measurements should be transmitted or not. The output measurements, which trigger the condition, are supposed to suffer a network-induced time-varying and bounded delay before arriving at the observer. Then, by adopting the input delay method, the estimation error system can be reformulated as a piecewise delay system. Based on the piecewise Lyapunov-Krasovskii functional and the Finsler's lemma, the event-triggered H∞observer design method is developed. Moreover, an algorithm is proposed to co-design the observer gains and the event-triggering parameters to guarantee that the estimation error system is asymptotically stable with a given disturbance attenuation level and the signal transmission rate is reduced as much as possible. Simulation studies are given to show the effectiveness of the proposed method.

具有分布时滞的广义系统的容许性条件

利用李雅普诺夫第二方法,研究了一类具有分布时滞的连续广义系统的容许性问题,得到了连续广义系统容许性时滞的相关条件。首先,在保证具有分布时滞的广义系统是正则、无脉冲的基础上,选取增广的Lyapunov-Krasovskii泛函(简称L-K泛函),并在L-K泛函中增加三重积分项以获得更多的时滞信息。然后,采用相对于Wirtinger积分不等式保守性更小的Bessel-Legendre积分不等式来估计L-K泛函求导后产生的一重积分项和二重积分项,得到广义时滞系统的稳定性条件。进而,利用线性矩阵不等式(简称LMI)给出具有分布时滞的连续广义系统的容许性条件。最后,通过数值算例验证了所得结果的可行性和有效性。同现有文献相比,运用的方法得到的结果具有更小的保守性。

时变时滞奇异摄动Lurie系统的控制器设计

为进一步加强对洛尔系统的鲁棒控制,基于前期稳定性分析理论基础上,研究含有不确定性结构的时变时滞奇异摄动Lurie系统在扇形区域[V1,V2]内的控制器设计问题。通过构造新的李雅普诺夫泛函利用新的交叉项界定法,由Lurie系统的特性,设计含有不确定性结构的时变时滞奇异摄动Lurie系统在一般的扇形区域[V1,V2]内的状态反馈控制器,推出时滞依赖和时滞独立两种情形下新的状态反馈控制率。最后,通过数值样例证明所设计方法的有效性和可行性。

Improved results on synchronization in arrays of coupled delayed neural networks with hybrid coupling

In order to investigate the influence of hybrid coupling on the synchronization of delayed neural networks, by choosing an improved delay-dependent Lyapunov-Krasovskii functional, one less conservative asymptotical criterion based on linear matrix inequality （LMI） is established. The Kronecker product and convex combination techniques are employed. Also the bounds of time-varying delays and delay derivatives are fully considered. By adjusting the inner coupling matrix parameters and using the Matlab LMI toolbox, the design and applications of addressed coupled networks can be realized. Finally, the efficiency and applicability of the proposed results are illustrated by a numerical example with simulations.

基于时滞理论的火箭发动机燃烧过程有记忆反馈控制

在控制系统中,时滞的存在往往引起系统性能变差,甚至不稳定。文中针对线性时滞系统,基于时滞分割方法分析建立了系统稳定新条件,在此基础上,设计了有记忆反馈控制器,该方法通过求解线性矩阵不等式(LMI)的可行解得到控制器的参数化表达式。该控制器应用于液体火箭发动机燃烧室燃烧过程的仿真表明,所提方法扩大了系统稳定的最大时滞上界范围,具有更低的保守性,同时具有更好的控制效果。

Global stabilization for a class of nonlinear time-delay systems using linear output feedback

The stabilization problem via the linear output feedback controller is addressed for a class of nonlinear systems subject to time-delay.The uncertainty of the system satisfies the lower-triangular growth condition and it is affected by time-delay. A linear output feedback controller with a tunable scaling gain is constructed.By selecting an appropriate Lyapunov-Krasovskii functional the scaling gain can be adjusted to render the closed-loop system globally asymptotically stable.The results can also be extended to the non-triangular nonlinear time-delay systems. The proposed control law together with the observer is linear and memoryless in nature and therefore it is easy to implement in practice. Two computer simulations are conducted to illustrate the effectiveness of the proposed theoretical results.

变时滞不确定中立型系统鲁棒稳定新判据

在工程实际当中,时变时滞和不确定的存在往往使得系统的性能变差甚至不稳定。针对一类含混合变时滞的不确定中立系统,研究了时滞相关鲁棒稳定性问题。在考虑不确定性为泛数有界的条件下,首先通过构造包含三重积分项的Lyapunov-Krasovskii(L-K)的泛函,其次利用新的积分不等式更紧的界定条件,引入相关项自由权矩阵的方法,处理泛函沿系统的导数产生的交叉项,建立了基于线性矩阵不等式(LMI)形式的鲁棒稳定新判据。该方法不涉及复杂的模型变换,减小了理论推导和计算上的复杂性,所提出判据与离散时滞和中立时滞均相关,且扩大了系统稳定所允许的最大时滞上界范围,具有更低的保守性。仿真算例表明所提出的稳定性判据是有效的。

Delay-range-dependent Stability Criterion for Interval Time-delay Systems with Nonlinear Perturbations

In this paper, we consider the problem of robust stability for a class of linear systems with interval time-varying delay under nonlinear perturbations using Lyapunov-Krasovskii （LK） functional approach. By partitioning the delay-interval into two segments of equal length, and evaluating the time-derivative of a candidate LK functional in each segment of the delay-interval, a less conservative delay-dependent stability criterion is developed to compute the maximum allowable bound for the delay-range within which the system under consideration remains asymptotically stable. In addition to the delay-bi-segmentation analysis procedure, the reduction in conservatism of the proposed delay-dependent stability criterion over recently reported results is also attributed to the fact that the time-derivative of the LK functional is bounded tightly using a newly proposed bounding condition without neglecting any useful terms in the delay-dependent stability analysis. The analysis, subsequently, yields a stable condition in convex linear matrix inequality （LMI） framework that can be solved non-conservatively at boundary conditions using standard numerical packages. Furthermore, as the number of decision variables involved in the proposed stability criterion is less, the criterion is computationally more effective. The effectiveness of the proposed stability criterion is validated through some standard numerical examples.

Robust Adaptive Control for Robotic Systems With Input Time-Varying Delay Using Hamiltonian Method

This paper addresses the problem of robust adaptive control for robotic systems with model uncertainty and input time-varying delay. The Hamiltonian method is applied to develop the stabilization results of the robotic systems. Firstly, with the idea of shaping potential energy and the pre-feedback skill, the n degree-of-freedom(DOF) uncertain robotic systems are realized as an augmented dissipative Hamiltonian formulation with delay.Secondly, based on the obtained Hamiltonian system formulation and by using of the Lyapunov-Krasovskii(L-K) functional method, an adaptive controller is designed to show that the robotic systems can be asymptotically stabilized depending on the input delay. Meanwhile, some sufficient conditions are spelt out to guarantee the rationality and validity of the proposed control law. Finally, study of an illustrative example with simulations shows that the controller obtained in this paper works very well in handling uncertainties and input delay in the robotic systems.

Tracking Control of Uncertain Nonlinear Systems With Unknown Constant Input Delay

A robust delay compensator has been developed for a class of uncertain nonlinear systems with an unknown constant input delay.The control law consists of feedback terms based on the integral of past control values and a novel filtered tracking error,capable of compensating for input delays.Suitable Lyapunov-Krasovskii functionals are used to prove global uniformly ultimately bounded(GUUB)tracking,provided certain sufficient gain conditions,dependent on the bound of the delay,are satisfied.Simulation results illustrate the performance and robustness of the controller for different values of input delay.

Robust stability and stabilization for uncertain discrete-time switched singular systems with time-varying delays

The problems of robust stability and stabilization via memoryless state feedback for a class of discrete-time switched singular systems with time-varying delays and linear fractional uncertainties are investigated.By constructing a novel switched Lyapunov-Krasovskii functional,a delay-dependent criterion for the unforced system to be regular,causal and uniformly asymptotically stable is established in terms of linear matrix inequalities（LMIs）.An explicit expression for the desired memoryless state feedback stabilization controller is also given.The merits of the proposed criteria lie in their less conservativeness and relative simplicity,which are achieved by considering additionally useful terms（ignored in previous methods） when estimating the upper bound of the forward difference of the Lyapunov-Krasovskii functional and by avoiding utilizing any model augmentation transformation.Some numerical examples are provided to illustrate the validity of the proposed methods.

New Stability Criteria for Recurrent Neural Networks with a Time-varying Delay

This paper deals with the stability of static recurrent neural networks （RNNs） with a time-varying delay. An augmented Lyapunov-Krasovskii functional is employed, in which some useful terms are included. Furthermore, the relationship among the timevarying delay, its upper bound and their difierence, is taken into account, and novel bounding techniques for 1- τ（t） are employed. As a result, without ignoring any useful term in the derivative of the Lyapunov-Krasovskii functional, the resulting delay-dependent criteria show less conservative than the existing ones. Finally, a numerical example is given to demonstrate the effectiveness of the proposed methods.

A delay-dependent passivity criterion of linear neutral delay systems

The problem of delay-dependent stability and passivity for linear neutral systems is discussed. By constructing a novel type Lyapunov-krasovskii functional, a new delay-dependent passivity criterion is presented in terms of linear matrix inequalities （LMIs）. Model transformation, bounding for cross terms and selecting free weighting matrices [12-14] are not required in the arguments. Numerical examples show that the proposed criteria are available and less conservative than existing results .