一类不确定广义周期时变系统的鲁棒H_∞控制

本文研究了状态矩阵具不确定性广义周期时变系统的鲁棒H∞控制问题.利用线性矩阵不等式(LMI)方法,在给出不确定广义周期时变系统广义可镇定和广义二次可镇定且具有H∞性能指标概念的基础上,得到了该系统广义二次可镇定且具有H∞性能指标γ的充要条件,并给出了相应的鲁棒H∞状态反馈控制律的设计方法,推广了周期系统的鲁棒控制理论结果.最后,通过数值算例说明了设计方法的有效性.     

参数不确定性广义周期时变系统的鲁棒H_∞控制

研究状态矩阵和控制输入矩阵均具不确定性广义周期时变系统的鲁棒H_∞控制问题.提出参数不确定性广义周期时变系统广义可镇定和广义二次可镇定且具有H_∞性能指标的概念,利用线性矩阵不等式(LMI)方法,得到了参数不确定性广义周期时变系统广义二次可镇定且具有H_∞性能指标γ的充要条件,给出了相应的鲁棒H_∞状态反馈控制律的设计方法.最后,通过数值算例说明了设计方法的有效性.     

状态与输出均有滞后的不确定广义系统的非脆弱H∞控制

针对带有状态滞后的连续广义系统,给出了其广义二次稳定且满足一定H∞性能的充分条件,并利用线性矩阵不等式技术,得到了带有状态滞后和不确定性的连续广义系统的含有控制器增益扰动的鲁棒H∞控制器的设计方法.最后,所举数值例子说明了该方法的应用.     

状态与输出均有滞后的不确定广义系统的非脆弱$H_\infty$控制

针对带有状态滞后的连续广义系统,给出了其广义二次稳定且满足一定H∞性能的充分条件,并利用线性矩阵不等式技术,得到了带有状态滞后和不确定性的连续广义系统的含有控制器增益扰动的鲁棒H∞控制器的设计方法.最后,所举数值例子说明了该方法的应用.     

时变线性中立型系统的鲁棒H∞性能

考虑了时变线性中立型系统的H∞性能，利用线性矩阵不等式给出了系统扰动衰减具有H∞范数约束的鲁棒稳定性条件．系统在H∞范数有界约束下，给出了时变中立型系统Lyapunov稳定意义下的等价时滞系统，说明了伪二次稳定意义下的不确定性中立型系统等价于一个在Lyapunov稳定意义下的标准线性时滞系统．     

具有饱和因子的时滞广义系统的鲁棒 H SymboleB@ 控制

研究了一类具有饱和因子并含有不确定参数的变时滞广义系统的时滞相关鲁棒H∞控制,系统的状态方程和输出方程均带有时滞,且状态方程的输入和输入时滞中均含饱和因子.通过构造Lya-punov-Krasovskii泛函,利用线性矩阵不等式方法和矩阵奇异值理论,给出了时滞广义系统正则、无脉冲、渐进稳定且满足H∞范数小于给定界γ的充分条件,并给出了H∞控制器的设计方法 .数值算例说明了本文所提方法具有更小的保守性.     

带有结构性不确定的线性时变系统的二次镇定及H~∞控制

本文讨论了带有结构性不确定的线性时变系统的二次镇定问题.建立了H∞指标γ和RDE及RDI之间的等价关系,并给出了带有结构性不确定线性时变系统二次稳定的充分条件;在此基础上将带有结构性不确定线性时变系统的鲁棒动态补偿器设计转化成求解一个相应的确定性辅助线性时变系统的标准H~∞控制问题.     

广义扭仿射李代数及其模

本文首先给出广义扭仿射李代数的概念;然后讨论这种李代数的不可约模H的性质;特别是给出了H的一个自然阶化分解;通过研究扭李代数g的流表示,证明关于扭流的换位关系式;最后证明作用在不可约模上的一类算子的局部幂零性.这一结果对研究共形块空间的广义扭仿射李代数模的实现起着基本的作用.     

基于输出反馈的一类时滞系统鲁棒H∞容错控制

针对状态具有多个时滞的线性不确定性系统,基于李雅普诺夫稳定性理论,矩阵不等式及线性矩阵不等式方法,设计带有多个时滞记忆的输出反馈鲁棒H∞容错控制器.研究了在执行器发生故障的情况下,多时滞不确定性系统的鲁棒H∞容错控制的问题.首先给出了多个时滞记忆的输出反馈鲁棒H∞容错控制器的综合分析,进一步给出参数不确定项的多时滞系统的渐近稳定的充分条件,以及满足给定性能指标鲁棒H∞容错控制器的设计方法.仿真结果证明了该方法的有效性和可行性.     

线性广义时滞系统的H∞输出反馈控制器

本文首先给出了广义时滞系统稳定的一个充分条件，接着讨论了线性广义时滞系统的H∞输出反馈控制，给出了控制器存在的充分条件，同时利用线性矩阵不等式(LMI)的方法，给出控制器的设计，最后举例说明本文方法的可行性．     

Topological Classification of Quadratic Systems at Infinity

It is proved that quadratic systems of autonomous differentialequations in the plane admit forty-five topologically distinctphase configurations at infinity. The related conditions onthe coefficients are given in affine invariant form.     

Geometry of quadratic differential systems in the neighborhood of infinity

In this article we give a complete global classification of the class QS_ess of planar, essentially quadratic differential systems (i.e. defined by relatively prime polynomials and whose points at infinity are not all singular), according to their topological behavior in the vicinity of infinity. This class depends on 12 parameters but due to the action of the affine group and re-scaling of time, the family actually depends on five parameters. Our classification theorem (Theorem 7.1) gives us a complete dictionary connecting very simple integer-valued invariants which encode the geometry of the systems in the vicinity of infinity, with algebraic invariants and comitants which are a powerful tool for computer algebra computations helpful in the route to obtain the full topological classification of the class QS of all quadratic differential systems.     

Design of Norm-Bounded and Sector-Bounded LQG Controllers for Uncertain Systems

The design of linear-quadratic-Gaussian (LQG) controllers is addressed for uncertain linear time-invariant systems that are either norm bounded or belong to a given sector. The system matrices are assumed to be affine functions of parameters confined to a convex polytopic region in the parameter space. Methods are developed for designing controllers which satisfy certain norm or sector conditions and are simultaneously optimal in the LQG sense. The resulting controllers provide robust stability as well as optimal performance.     

Quadratic vector fields in ℂP2 with solvable monodromy group at infinity

Quadratic vector fields for which the line at infinity is a phase curve with three different singular points are considered. It is assumed that the characteristic numbers of these singular points are not multiples of 1/4 or 1/6. It is shown that among the fields with fixed characteristic numbers satisfying this assumption, one can choose seven fields such that any other field with solvable noncommutative monodromy group at infinity is affine equivalent to one of the chosen fields. In addition, quadratic vector fields with commutative monodromy group at infinity are described.     

A piecewise ellipsoidal reachable set estimation method for continuous bimodal piecewise affine systems

In this work, the issue of estimation of reachable sets in continuous bimodal piecewise affine systems is studied. A new method is proposed, in the framework of ellipsoidal bounding, using piecewise quadratic Lyapunov functions. Although bimodal piecewise affine systems can be seen as a special class of affine hybrid systems, reachability methods developed for affine hybrid systems might be inappropriately complex for bimodal dynamics. This work goes in the direction of exploiting the dynamical structure of the system to propose a simpler approach. More specifically, because of the piecewise nature of the Lyapunov function, we first derive conditions to ensure that a given quadratic function is positive on half spaces. Then, we exploit the property of bimodal piecewise quadratic functions being continuous on a given hyperplane. Finally, linear matrix characterizations of the estimate of the reachable set are derived.     

Quadratic optimal synchronization of uncertain chaotic systems

This paper investigates the quadratic optimal synchronization of uncertain chaotic systems with parameter mismatch, parametric perturbations and external disturbances on both master and slave systems. A robust control scheme based on Lyapunov stability theory and quadratic optimal control approach is derived to realize chaotic synchronization. The sufficient criterion for stability condition is formulated in a linear matrix inequality (LMI) form. The effect of uncertain parameters and external disturbance is suppressed to an H_∞ norm constraint. An adaptive algorithm is proposed to adjust the uncertain bound in the robust controller avoiding the chattering phenomena. The simulation results for synchronization of the Chua’s circuit system and the Lorenz system demonstrate the effectiveness of the proposed scheme.     

Stability radius of linear parameter-varying systems and applications

In this paper, we present a unifying approach to the problems of computing of stability radii of positive linear systems. First, we study stability radii of linear time-invariant parameter-varying differential systems. A formula for the complex stability radius under multi perturbations is given. Then, under hypotheses of positivity of the system matrices, we prove that the complex, real and positive stability radii of the system under multi perturbations (or affine perturbations) coincide and they are computed via simple formulae. As applications, we consider problems of computing of (strong) stability radii of linear time-invariant time-delay differential systems and computing of stability radii of positive linear functional differential equations under multi perturbations and affine perturbations. We show that for a class of positive linear time-delay differential systems, the stability radii of the system under multi perturbations (or affine perturbations) are equal to the strong stability radii. Next, we prove that the stability radii of a positive linear functional differential equation under multi perturbations (or affine perturbations) are equal to those of the associated linear time-invariant parameter-varying differential system. In particular, we get back some explicit formulas for these stability radii which are given recently in [P.H.A. Ngoc, Strong stability radii of positive linear time-delay systems, Internat. J. Robust Nonlinear Control 15 (2005) 459-472; P.H.A. Ngoc, N.K. Son, Stability radii of positive linear functional differential equations under multi perturbations, SIAM J. Control Optim. 43 (2005) 2278-2295]. Finally, we give two examples to illustrate the obtained results.     

一类非线性系统的时滞相关H∞控制

本文研究一类非线性控制系统的时滞相关日。控制问题．首先通过构造恰当的Lyapunov泛函,设计非线性H∞控制器,得到了该类非线性控制系统渐近稳定的一个充分条件．其次通过建立具有线性矩阵不等式（LMI）约束的凸优化问题,得到了该类非线性系统的时滞相关H∞性能的一个充分条件．MATLAB仿真验证了本文方法的可行性．     

Global input-to-state stability and stabilization of discrete-time piecewise affine systems

This article presents conditions for global input-to-state stability (ISS) and stabilization of discrete-time, possibly discontinuous, piecewise affine (PWA) systems. Piecewise quadratic, possibly discontinuous candidate ISS Lyapunov functions are employed for both analysis and synthesis purposes. This enables us to obtain sufficient conditions based on linear matrix inequalities, which can be solved efficiently. One of the advantages of using the ISS framework is that additive disturbance inputs are explicitly taken into account in the analysis and synthesis procedures. Furthermore, the results apply to PWA systems in their full generality, i.e. non-zero affine terms are allowed in the regions in the partition whose closure contains the origin.