Finite‐time stability of switched nonlinear time‐varying systems via indefinite Lyapunov functions

This note considers the problem of finite‐time stability (FTS) for switched nonlinear time‐varying systems. First, a relaxed condition is proposed to verify the FTS of nonlinear time‐varying systems by using an indefinite Lyapunov function. Then, the result obtained is extended to study the FTS of switched nonlinear time‐varying systems. Several relaxed conditions are given by using a common indefinite Lyapunov function and multiple indefinite Lyapunov functions. Moreover, the corresponding estimates on convergence regions and times of systems are also given. Comparing with the existing results, the conditions obtained allow the time derivative of Lyapunov functions of subsystems (or systems) to be indefinite and all subsystems to be not finite‐time stable or even unstable. Finally, a numerical example is given to illustrate the theoretical results.     

Improved stability and instability theorems for stochastic nonlinear systems

This paper focuses on sufficient conditions which make stochastic nonlinear systems stable and unstable. A series of new stability (instability) criteria, which admit the infinitesimal operator of Lyapunov (Lyapunov‐like or Chetaev) functions to be indefinite, are proposed using the uniformly asymptotically stable function. The obtained stability and instability theorems weaken the constraints on Lyapunov and Lyapunov‐like (or Chetaev) functions, respectively. Many existing classical stability and instability criteria can be regarded as special cases of the stability and instability results in this paper. Finally, the presented theoretical results are illustrated by some simulation examples.     

LMI‐based stability analysis of linear hybrid systems with application to switched control of a refrigeration process

We consider continuous‐time switched linear systems associated with linear state reset during mode switches, which are called linear hybrid systems and can be commonly found in switched control systems via bumpless transfer during controller switches. We use a multiple Lyapunov functions approach to develop constructive tools for stability analysis of linear hybrid systems. In particular, we derive a linear‐matrix‐inequalities based procedure to compute upper bounds of dwell time for uniform global exponential stability in linear hybrid systems, and we apply it to a refrigeration process that is regulated by several switched proportional‐integral controllers via bumpless transfer. Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

Exponential stability of nonlinear impulsive switched systems with stable and unstable subsystems

Exponential stability and robust exponential stability relating to switched systems consisting of stable and unstable nonlinear subsystems are considered in this study. At each switching time instant, the impulsive increments which are nonlinear functions of the states are extended from switched linear systems to switched nonlinear systems. Using the average dwell time method and piecewise Lyapunov function approach, when the total active time of unstable subsystems compared to the total active time of stable subsystems is less than a certain proportion, the exponential stability of the switched system is guaranteed. The switching law is designed which includes the average dwell time of the switched system. Switched systems with uncertainties are also studied. Sufficient conditions of the exponential stability and robust exponential stability are provided for switched nonlinear systems. Finally, simulations show the effectiveness of the result.     

Switched nonlinear singular systems with time‐delay: Stability analysis

This paper presents an approach to the stability analysis of a class of nonlinear interconnected continuous‐time singular systems with arbitrary switching signals. This class of interconnected subsystems consists of unknown but bounded state delay and nonlinear terms, and each subsystem can be globally stable, unstable, or locally stable. By constructing a new Lyapunov‐like Krasovskii functional, sufficient conditions are derived and formulated to check the asymptotic (exponential) stability of such systems with arbitrary switching signals. Then, some new general criteria for asymptotic (exponential) stability with average dwell‐time switching signals are also established. The theoretical developments are demonstrated by two numerical simulations. Copyright © 2014 John Wiley & Sons, Ltd.     

External stability of Caputo fractional‐order nonlinear control systems

This paper investigates external stability of Caputo fractional‐order nonlinear control systems. Following the idea of a traditional Lyapunov function method, we point out the problems that would appear when applying it for fractional external stability. These problems are shown to be solvable by employing results on smoothness of solutions, but this method generalized for Caputo fractional‐order nonlinear control systems requires strong conditions to be imposed on vector field functions and inputs. To further explore the fractional external stability, diffusive realizations and Lyapunov‐like functions are taken into consideration. Specifically, a Caputo fractional‐order nonlinear control system with certain assumptions proves to be equivalent to its diffusive realization; a Lyapunov‐like function based on the realization exhibits properties useful to prove the external stability. As expected, this Lyapunov‐like method has weaker requirements. Finally, it is applied to the external stabilization of a Caputo fractional‐order Chua's circuits with inputs.     

Stability and stabilization of continuous‐time switched systems: A multiple discontinuous convex Lyapunov function approach

In this paper, the problems of stability and stabilization are considered for a class of switched linear systems with slow switching and fast switching. A multiple convex Lyapunov function and a multiple discontinuous convex Lyapunov function are first introduced, under which the extended stability and stabilization results are derived with a mode‐dependent average dwell time switching strategy, where slow switching and fast switching are exerted on stable and unstable subsystems, respectively. These two types of Lyapunov functions are established in a constructive manner by virtue of a set of time‐varying functions. By using our proposed approaches, larger stability regions of system parameters are identified, and tighter bounds can be obtained for the mode‐dependent average dwell time. New mode‐dependent and time‐varying controllers are constructed for a class of switched control systems with stabilizable and unstabilizable subsystems as well. All the stability and stabilization conditions can be given in terms of strict linear matrix inequalities (LMIs), which can be checked easily by using recently developed algorithms in solving LMIs. Finally, two numerical examples are provided to show the effectiveness of the obtained results compared with the existing results.     

Stability analysis of switched nonlinear delay systems with sampled‐data inputs

This study addresses the uniformly globally asymptotically stability (UGAS) problem of switched nonlinear delay systems (SNDSs) with sampled‐data inputs (SDIs). By using multiple Lyapunov functionals (MLFs) method, mode‐dependent average dwell times, and the total activating time length of MLFs, some stability criteria are explicitly obtained for SNDSs with SDIs. Meanwhile, the UGAS property for SNDSs with some or all unstable modes is investigated. For unstable modes and stable modes, we adopt different switching signals. Besides, we establish some sufficient stability conditions in the form of an upper bound on the sum of dwell times and sampling intervals. Simulation examples are adopted to illustrate and verify the effectiveness of our proposed methods.     

具有非线性扰动多时滞系统鲁棒稳定性分析与分散鲁棒控制

研究一类非线性参数扰动满足范数有界条件时多重时滞系统的鲁棒稳定性及其分散鲁棒控制。首先利用Lyapunov函数方法分析系统的鲁棒稳定性,获得一种新的稳定性条件,然后利用标量Lyapunov方程方法讨论系统指数稳定的条件,通过对系统采取分散反馈控制,进一步得到系统可鲁棒镇定和可指数镇定的条件。     

Adaptive fuzzy semi‐decentralized control for a class of large‐scale nonlinear systems with unknown interconnections

In this paper, a general method is developed to generate a stable adaptive fuzzy semi‐decentralized control for a class of large‐scale interconnected nonlinear systems with unknown nonlinear subsystems and unknown nonlinear interconnections. In the developed control algorithms, fuzzy logic systems, using fuzzy basis functions (FBF), are employed to approximate the unknown subsystems and interconnection functions without imposing any constraints or assumptions about the interconnections. The proposed controller consists of primary and auxiliary parts, where both direct and indirect adaptive approaches for the primary control part are aiming to maintain the closed‐loop stability, whereas the auxiliary control part is designed to attenuate the fuzzy approximation errors. By using Lyapunov stability method, the proposed semi‐decentralized adaptive fuzzy control system is proved to be globally stable, with converging tracking errors to a desired performance. Simulation examples are presented to illustrate the effectiveness of the proposed controller. Copyright © 2006 John Wiley & Sons, Ltd.     

Stability of simultaneously block triangularisable switched systems with partial state reset

We study the stability of a certain class of switched systems where discontinuous jumps (resets) on some of the state components are allowed, at the switching instants. It is known that, if all components of the state are available for reset, the system can be stabilisable by an adequate choice of resets. However, this question may have negative answer if there are forbidden state components for reset. We give a sufficient condition for the stabilisability of a switched system, under arbitrary switching, by partial state reset in terms of a block simultaneous triangularisability condition. Based on this sufficient condition, we show that the particular class of systems with partially commuting stable system matrices is stabilisable by partial state reset. We also provide an algorithm that allows testing whether a switched system belongs to this particular class of systems.     

Reset与嵌入式系统应用的稳定性

嵌入式系统的应用领域越来越广泛,干扰或者恶劣环境常影响嵌入式系统运行的稳定性和可靠性。Reset是维护系统稳定的一个关键因素,正确地设计复位电路,巧妙地应用复位操作,能使整个系统更可靠、稳定地运行。本文结合实际项目经验分析Reset的相关应用与设计,展示Reset对系统稳定性的重要性。     

On the stability issues of switched singular time‐delay systems with slow switching based on average dwell‐time

The issue of exponential stability analysis of continuous‐time switched singular systems consisting of a family of stable and unstable subsystems with time‐varying delay is investigated in this paper. It is very difficult to analyze the stability of such systems because of the existence of time‐delay and unstable subsystems. In this regard, on the basis of the free‐weighting matrix approach, by constructing the new Lyapunov‐like Krasovskii functional, and using the average dwell‐time approach, delay‐dependent sufficient conditions are derived and formulated in terms of LMIs to check the exponential stability of such systems. This paper also highlights the relationship between the average dwell‐time of the switched singular time‐delay system, its stability, exponential convergence rate of differential states, and algebraic states. Finally, a numerical example is given to confirm the analytical results and illustrate the effectiveness of the proposed strategy. Copyright © 2012 John Wiley & Sons, Ltd.     

PIECEWISE LYAPUNOV FUNCTIONS FOR SWITCHED SYSTEMS WITH AVERAGE DWELL TIME

The stability properties of linear switched systems consisting of both Hurwitz stable and unstable subsystems are investigated by using piecewise Lyapunov functions incorporated with an average dwell time approach. It is shown that if the average dwell time is chosen sufficiently large and the total activation time ratio between Hurwitz stable and unstable subsystems is not smaller than a specified constant, then exponential stability of a desired degree is guaranteed. The above result is also extended to the case where nonlinear norm‐bounded perturbations exist.     

网络化线性系统的重置控制

针对经由具有通信带宽限制的网络通道构成反馈的重置控制系统，分析了网络延时对重置控制系统和稳定性的影响，在考虑传感器．控制器延时和控制器．执行器延时的情况下，利用Kalman-Yakubovich-Popov(KYP)引理，获得了由线性被控对象和线性状态反馈控制器组成的重置系统的类Lyapunov指数稳定性判据和鲁棒稳定性判据。进而得到一种实用的二次稳定性条件。     

一类脉冲切换系统的有限时间稳定性

针对一类具有脉冲现象的非线性切换系统,提出了一种基于有限时间稳定lyapunov函数技术和多Lyapunov函数技术相结合的有限时间稳定性分析方法。该方法首先将非线性系统的有限时间稳定性的概念推广到所考虑的脉冲切换系统。然后,利用有限时间Lyapunov函数技术,确保各个子系统达到有限时间稳定。进一步,给出一个有限时间稳定的非线性比较系统。通过多Lyapunov函数技术,保证原系统的Lyapunov函数值不超过比较系统的状态值,由此得到原脉冲非线性切换系统有限时间稳定的充分条件。最后,一个数值例子说明文中方法的有效性。本文所得的研究结果能应用于生产线控制,交通管理,网络控制等实际系统。     

Economic MPC with a contractive constraint for nonlinear systems

In this paper, we consider the stability issue of economic model predictive control (EMPC) for constrained nonlinear systems and propose a new contractive constraint formulation of nonlinear EMPC schemes. This formulation is one of Lyapunov‐based approaches in which the contractive function chosen a priori can be used as a Lyapunov function. Some conditions are given to guarantee recursive feasibility and asymptotic stability of the EMPC. Moreover, we analyze the transient economic performance of the EMPC closed‐loop system in some finite‐time intervals. The proposed EMPC scheme is applied to a chemical reactor model to illustrate its utility and benefits. Copyright © 2016 John Wiley & Sons, Ltd.     

Lipschitz广义非线性系统观测器设计

研究一类广义非线性系统的观测器设计问题．首先讨论了半正定Lyapunov函数下指数1广义非线性系统稳定及渐近稳定性,然后对一类由线性和Lipschitz非线性项组成的广义非线性系统,给出了渐近稳定观测器存在的条件,并把观测器反馈增益矩阵的设计归结为广义线性系统容许控制以及奇异值计算问题,证明了若容许广义线性系统矩阵的最小奇异值大于系统的Lipschitz常数,容许控制器增益矩阵就是待求的观测器反馈增益矩阵。     

Stability Analysis and Controller Design of Discrete Interval Type‐2 Fuzzy Systems

This paper is concerned with trajectory stabilization of a computer simulated model car with uncertain velocity via type‐2 fuzzy control systems. First, stability conditions of discrete interval type‐2 fuzzy control systems are given in accordance with the definition of stability in the sense of Lyapunov. Then, we approximate a computer simulated model car, whose dynamics are nonlinear and velocity is uncertain. A type‐2 Takagi–Sugeno TS fuzzy controller is designed to handle system uncertainty. The control rules, which guarantee stability of the system, are derived from the approximated model. The simulation results show that the type‐2 fuzzy control rules can effectively stabilize the car model.