混沌细胞神经网络的自适应同步及其在保密通信中的应用

针对具有时变时滞和扰动的混沌细胞神经网络的同步问题,提出一种自适应同步方法。利用Lyapunov稳定性理论、Barbalat引理和自适应控制方法,给出易于实现的自适应同步控制律,实现了误差系统的全局渐近稳定。所得自适应同步控制律具有一定的鲁棒性。最后利用混沌掩盖技术将研究结果应用到保密通信中。数值仿真结果表明,该方法所设计的自适应控制律具有良好的控制效果。     

Schwarz lemma for driving point impedance functions and its circuit applications

In this paper, a boundary version of the Schwarz lemma is investigated for driving point impedance functions and its circuit applications. It is known that driving point impedance function, Z(s) = 1 + c_p(s − 1)^p + c_{p + 1}(s − 1)^{p + 1} + ..., p > 1, is an analytic function defined on the right half of the s-plane. Two theorems are presented using the modulus of the derivative of driving point impedance function, |Z′(0)|, by assuming the Z(s) function is also analytic at the boundary point s = 0 on the imaginary axis with . In the obtained inequalities, the value of the function at s = 1 and the derivatives with different orders have been used. Finally, the sharpness of the inequalities obtained in the presented theorems is proved. Simple LC circuits are obtained using the obtained driving point impedance functions.     

State‐space characterization of all solutions to a positive real control problem

Abstract

The purpose of this paper is to give a state‐space characterization of all internally stabilizing finite‐dimensional linear time‐invariant output feedback controllers for a given finite‐dimensional linear time‐invariant plant which ensure that the resulting closed‐loop transfer function is extended strictly positive real(ESPR). All such controllers are parameterized by a fixed linear fractional transformation with an ESPR, stable free parameter. The parameterized controllers have a state dimension not less than that of the open‐loop plant. The development uses only elementarily algebraic ideas beginning with a change of variables, an extended version of Kalman‐Yacubovich‐Popov positive real lemma, and Youla parameterization, thus the proofs given are simple and clear.     

Synchronisation of a class of networked passive systems with switching topology

This article considers the output synchronisation of a class of networked agents. Each agent is a passive system. Local information, used by each agent to adjust its movement, forms a network with switching adjacent topology. First, we consider the asymptotic stability of switched non-linear time-varying systems with delayed measurement feedback by using multiple Lyapunov function. A Barbalat-like lemma is obtained. Then the result is applied to the output synchronisation of a class of networked passive systems with switching topology. A verifiable sufficient condition is presented.     

An H∞ deconvolution filter and its application to ultrasonic nondestructive evaluation of materials

Deconvolution can be a valuable technique for interpreting results of ultrasonic nondestructive evaluation (NDE) tests of materials. This is especially true for state of the art hybrid materials. In this paper, a new H_∞ deconvolution filter is presented. The filter is applied to typical ultrasonic NDE data, including through-transmission data for aluminum and composite samples. The results are compared to those obtained from a Wiener deconvolution filter. The performance of the H_∞ filter is as good or better than the performance of the Wiener filter.     

Linear Operator Inequalities for Strongly Stable Weakly Regular Linear Systems

We consider the question of the existence of solutions to certain linear operator inequalities (Lur'e equations) for strongly stable, weakly regular linear systems with generating operators A, B, C, 0. These operator inequalities are related to the spectral factorization of an associated Popov function and to singular optimal control problems with a nonnegative definite quadratic cost functional. We split our problem into two subproblems: the existence of spectral factors of the nonnegative Popov function and the existence of a certain extended output map. Sufficient conditions for the solvability of the first problem are known and for the case that A has compact resolvent and its eigenvectors form a Riesz basis for the state space, we give an explicit solution to the second problem in terms of A, B, C and the spectral factor. The applicability of these results is demonstrated by various heat equation examples satisfying a positive-real condition. If (A, B) is approximately controllable, we obtain an alternative criterion for the existence of an extended output operator which is applicable to retarded systems. The above results have been used to design adaptive observers for positive-real infinite-dimensional systems. Date received: July 25, 1997. Date revised: February 10, 2001.     

Existence of unmixed solutions of the discrete-time algebraic Riccati equation and a nonstrictly bounded real lemma

The existence of a solution of the discrete-time algebraic Riccati equation is established assuming modulus controllability and positive semidefiniteness on the unit circle of the Popov function. As an application a nonstrictly bounded real lemma is obtained.     

稳定化的有限频段H∞控制及有限频段跟踪问题

基于GKYP引理的动态输出反馈设计,未保证设计后闭环系统的稳定性。针对以小增益作为指标的有限频段动态输出反馈问题,在不增加新变量的前提下,增加稳定性约束,使得设计后的闭环系统渐近稳定且满足有限频段性能指标。针对增加约束后难以找到可行解的情况,基于零空间条件的不惟一性,补充了另一种零空间条件,从而扩大了问题的可行域。将改进后的方法应用于有限频段跟踪问题的研究,通过仿真例子验证,有限频段动态输出反馈虽然存在保守性,但在合理选择基矩阵R的情况下,仍然可以使得其保守性小于传统的全频段最优H∞控制的保守性。     

Minimal representations of continuous-time processes having spectral density with zeros in the extended imaginary axis

Given a process y with stationary increments and rational incremental spectral density Φ(s), we parametrize minimal state-space representations of dy. We consider the case when Φ(s) may have zeros on the imaginary axis including infinity and we analyze the zero structure of each state-space representation.     

Neumann引理的一个推广及其应用

给出了经典Neumann引理的一个推广，并给出这一推广在研究算子扰动及Bessel列与框架的扰动问题中的一些应用．