Stability Analysis of Systems With Time-varying Delay via a Novel Lyapunov Functional

This paper investigates the stability problem for time-varying delay systems.To obtain a larger delay bound,this paper uses the second-order canonical Bessel-Legendre(BL)inequality.Secondly,using four couples of integral terms in the augmented Lyapunov-Krasovskii function(LKF)to enhance the relationship between integral functionals and other vectors.Furthermore,unlike the construction of the traditional LKF,a novel augmented LKF is constructed with two new delayproduct-type terms,which adds more state information and leads to less conservative results.Finally,two numerical examples are provided to demonstrate the effectiveness and the significant improvement of the proposed stability criteria.

Stability Analysis of T-S Fuzzy Control Systems Based on Parameter-dependent Lyapunov Function

For discrete-time T-S fuzzy systems, the stability and controller design method are in-vestigated based on parameter-dependent Lyapunov function (PDLF). T-S fuzzy systems di?er fromnon-fuzzy systems with polytopic description or multi-model description in that the weighting coef-ficients have respective meanings. They, however, have stability aspect in common. By adopting astability condition for polytopic systems obtained via PDLF, and combining the properties of T-Sfuzzy systems, new results are given in this paper. An example shows that by applying the newresults, the stability conditions that can be distinguished are less conservative.

Stability Analysis on Speed Control System of Autonomous Underwater Vehicle

The stability of the motion control system is one of the decisive factors of the control quality for Autonomous Underwater Vehicle（AUV）.The divergence of control,which the unstable system may be brought about,is fatal to the operation of AUV.The stability analysis of the PD and S-surface speed controllers based on the Lyapunov＇s direct method is proposed in this paper.After decoupling the six degree-of-freedom（DOF）motions of the AUV,the axial dynamic behavior is discussed and the condition is deduced,in which the parameters selection within stability domain can guarantee the system asymptotically stable.The experimental results in a tank and on the sea have successfully verified the algorithm reliability,which can be served as a good reference for analyzing other AUV nonlinear control systems.

Stability analysis of helical rod based on exact Cosserat model

Helical equilibrium of a thin elastic rod has practical backgrounds, such as DNA, fiber, sub-ocean cable, and oil-well drill string. Kirchhoff＇s kinetic analogy is an effective approach to the stability analysis of equilibrium of a thin elastic rod. The main hypotheses of Kirchhoff＇s theory without the extension of the centerline and the shear deformation of the cross section are not adoptable to real soft materials of biological fibers. In this paper, the dynamic equations of a rod with a circular cross section are established on the basis of the exact Cosserat model by considering the tension and the shear deformations. Euler＇s angles are applied as the attitude representation of the cross section. The deviation of the normal axis of the cross section from the tangent of the centerline is considered as the result of the shear deformation. Lyapunov＇s stability of the helical equilibrium is discussed in static category. Euler＇s critical values of axial force and torque are obtained. Lyapunov＇s and Euler＇s stability conditions in the space domain are the necessary conditions of Lyapunov＇s stability of the helical rod in the time domain.

Asymptotic stability for impulsive functional differential equations

In this paper, we investigate the stability of a class of impulsive functional differential equations by using Lyapunov functional and Jensen＇s inequality. Some new stability theorems are obtained. Examples are given to demonstrate the advantage of the obtained results.

Stability of a Neutral Stochastic Functional Differential Equations

Sufficient condition for stochastic unifrom stability of a neutral stochastic functional differential equation is given, especially, new techniques are developed to cope with the neutral delay case, we obtained the sufficient condition for asymptotic stability of neutral stochastic differential delay equations. Due to the new techniques developed in this paper, the results obtained arc very general and useful. The theory developed here gives a unified treatment for various asymptotic estimates e.g. exponential and polynomial bounds.

Absolute Stability of Nonlinear Systems with Two Additive Time-varying Delay Components

In this paper, we present a new sufficient condition for absolute stability of Lure system with two additive time-varying delay components. This criterion is expressed as a set of linear matrix inequalities （LMIs）, which can be readily tested by using standard numerical software. We use this new criterion to stabilize a class of nonlinear time-delay systems. Some numerical examples are given to illustrate the applicability of the results using standard numerical software.

Stability of Nonlinear Differential-Algebraic Systems Via Additive Identity

The stability analysis for nonlinear differentialalgebraic systems is addressed using tools from classical control theory. Sufficient stability conditions relying on matrix inequalities are established via Lyapunov Direct Method. In addition, a novel interpretation of differential-algebraic systems as feedback interconnection of a purely differential system and an algebraic system allows reducing the stability analysis to a smallgain-like condition. The study of stability properties for constrained mechanical systems, for a class of Lipschitz differential-algebraic systems and for an academic example is used to illustrate the theory.

Stability and stabilization of discrete T-S fuzzy time-delay system based on maximal overlapped-rules group

The problems of stability and stabilization for the discrete Takagi-Sugeno（T-S） fuzzy time-delay system are investigated.By constructing a discrete piecewise Lyapunov-Krasovskii function（PLKF） in each maximal overlapped-rules group（MORG）,a new sufficient stability condition for the open-loop discrete T-S fuzzy time-delay system is proposed and proved.Then the systematic design of the fuzzy controller is investigated via the parallel distributed compensation control scheme,and a new stabilization condition for the closed-loop discrete T-S fuzzy time-delay system is proposed.The above two sufficient conditions only require finding common matrices in each MORG.Compared with the common Lyapunov-Krasovskii function（CLKF） approach and the fuzzy Lyapunov-Krasovskii function（FLKF） approach,these proposed sufficient conditions can not only overcome the defect of finding common matrices in the whole feasible region but also largely reduce the number of linear matrix inequalities to be solved.Finally,simulation examples show that the proposed PLKF approach is effective.

Roust Power System Stabilizer Design Using Kharitonov’s Theorem:A Case Study

This paper proposes a robust power system stabilizer(PSS)for a steam synchronous generator in Barka II power station.The PSS should be capable of damping small-disturbance oscillations(inherently existing in power systems due to e.g.load changes,lines switching...etc.)within a certain settling time for different load conditions.Also,the proposed PSS must have the conventional structure and its parameters must not be violated.To achieve this goal,robust control provides many advantages.The suggested controller is tuned by the Kharitonov’s theorem and uses the standard structure employed in industry.The problem is cast into a nonlinear constrained optimization problem to achieve the desired settling time without violating the practical values of the controller parameters.Performance of the robust PSS is evaluated by several simulations in the presence of system uncertainty due to load changes.

基于模糊Lyapunov-Krasovskii函数的离散时滞T-S模糊模型的非二次镇定条件

研究了离散时滞T-S模糊模型基于模糊Lyapunov-Krasovskii函数的稳定性分析及控制器设计问题.首先,构造出离散型模糊Lyapunov-Krasovskii函数,此函数是系数与T-S模糊模型的模糊规则权重相对应的复合型Lyapunov-Krasovskii函数.然后,基于一系列线性矩阵不等式,得到了开环系统稳定的充分条件,进而又基于非二次PDC控制律,设计出了模糊控制器.最后,仿真实例验证了该方法的有效性和优越性.

基于Lyapunov方法T-S模糊系统的H_∞控制

针对Takagi-Sugeno(T-S)模糊系统,研究了H∞状态反馈控制器的设计问题.利用Lyapunov稳定性理论,采用线性矩阵不等式(LM I)技术,以矩阵不等式和线性矩阵不等式(LM Is)的形式给出2个新的确保T-S模糊系统存在H∞状态反馈控制器的充分条件.已有的结果没有考虑各个子系统之间的联系,致使所得的条件过于保守,而所提出的方法充分考虑了每个模糊子系统之间的联系,所得到的条件具有更大的宽松性.数值算例说明了该方法的有效性.

Stabilization and trajectory tracking of autonomous airship's planar motion

The stabilization and trajectory tracking problems of autonomous airship＇s planar motion are studied. By defining novel configuration error and velocity error, the dynamics of error systems are derived. By applying Lyapunov stability method, the state feedback control laws are designed and the close-loop error systems are proved to be uniformly asymptotically stable by Matrosov theorem. In particular, the controller does not need knowledge on system parameters in the case of set-point stabilization, which makes the controller robust with respect to parameter uncertainty. Numerical simulations illustrate the effectiveness of the controller designed.

Fixed-Time Lyapunov Criteria and State-Feedback Controller Design for Stochastic Nonlinear Systems

This paper investigates the fixed-time stability theorem and state-feedback controller design for stochastic nonlinear systems.We propose an improved fixed-time Lyapunov theorem with a more rigorous and reasonable proof procedure.In particular,an important corollary is obtained,which can give a less conservative upper-bound estimate of the settling time.Based on the backstepping technique and the addition of a power integrator method,a state-feedback controller is skillfully designed for a class of stochastic nonlinear systems.It is proved that the proposed controller can render the closed-loop system fixed-time stable in probability with the help of the proposed fixed-time stability criteria.Finally,the effectiveness of the proposed controller is demonstrated by simulation examples and comparisons.

Improvements of LaSalle's Theorem

In this paper, we improve LaSalle＇s invariance theorem based on Li＇s work （Li Yong, Asymptotic stability and ultimate boundedness, Northeast. Math. J., 6（1）（1990）, 53-59） by relaxing the restrictions, which make the theorem more easy to apply. In addition, we also improve LaSalle＇s theorem for stochastic differential equation established by Mao （Mao Xuerong, Stochastic versions of the LaSalle theorem, J. Differential Equations, 153（1999）, 175-195）.

带有扰动的适型分数阶时滞系统的稳定分析

基于非线性系统Lyapunov稳定理论,在适型分数阶导数意义下,针对带有扰动的导数阶数在开区间(0,1)的分数阶时滞非线性系统,研究其稳定与镇定.首先,基于Lyapunov-Krasovskii泛函思想,给出带有扰动的适型分数阶时滞系统稳定定理.其次,基于TP管控策略,在Filippov解的意义下,给出带有扰动的时滞适型分数阶系统反馈镇定定理.最后,举例说明结果的正确性.

离散模糊系统分析与设计的模糊Lyapunov方法

研究离散T-S模糊控制系统基于模糊Lyapunov函数的稳定性分析及控制器设计问题.首先,构造出离散型模糊Lyapunov函数,模糊Lyapunov函数是系数与T-S模糊系统的模糊规则权重相对应的复合型Lyapunov函数.然后,得到了开环系统新的稳定性充分条件,与公共Lyapunov方法的结果相比,这一条件更为宽松.进而,基于一系列线性矩阵不等式设计出模糊控制器.最后,仿真实例说明了该方法的算法和本文条件的优越性.

基于Lyapunov稳定理论设计MRAC系统的简单方法

基于李雅普诺夫稳定理论,用统一格式研究单输入单输出模型参考自适应控制系统,提出一种利用模型输出微分测量值来设计控制系统的方法,避免了被控对象输出微分不可测的问题,从而省掉一组滤波器,不需要辅助信号,而且结构上大为简化。由于采用从模型取状态的方法,增加了抗噪声干扰的能力。

T-S模糊系统的稳定性分析与镇定控制器设计

应用广义模糊Lyapunov函数方法研究T-S模糊系统的稳定性与控制器设计问题.首先,将T-S模糊系统表示成模糊广义系统的形式;然后利用广义模糊Lyapunov函数得到模糊系统稳定的充分条件,并且给出基于线性矩阵不等式(LMI)的PDC控制器设计方法.该方法与已有的模糊Lyapunov函数方法相比,计算量小,并且表达成LMI形式,容易求解.最后,通过例子验证方法的优越性和有效性.