Minor Self-conjugate and Skewpositive Semidefinite Solutions to a System of Matrix Equations over Skew Fields

Minor self conjugate (msc) and skewpositive semidefinite (ssd) solutions to the system of matrix equations over skew fields [A mn X nn =A mn ,B sn X nn =O sn ] are considered. Necessary and sufficient conditions for the existence of and the expressions for the msc solutions and the ssd solutions are obtained for the system.

THE SYMMETRIC AND SYMMETRIC POSITIVE SEMIDEFINITE SOLUTIONS OF LINEAR MATRIX EQUATION——B^TXB = D ON LINEAR MANIFOLDS

This paper discusses the solutions of the linear matrix equation BT X B=Don some linear manifolds.Some necessary and sufficient conditions for the existenceof the solution and the expression of the general solution are given.And also someoptimal approximation solutions are discussed.

COMPUTING THE NEAREST BISYMMETRIC POSITIVE SEMIDEFINITE MATRIX UNDER THE SPECTRAL RESTRICTION

Let A and C denote real n × n matrices. Given real n-vectors x1,……… ,xm,m≤n,and a set of numbers (L)={λ1,λ2…λm}，We descrbe(Ⅰ)the set( ) of all real n × n bisymmetric positive seidefinite matrices A such that Axi is the "best"approximate to λixi, i = 1, 2,..., m in Frobenius norm and (Ⅱ) the Y in set ( )which minimize Frobenius norm of ||C - Y||.An existence theorem of the solutions for Problem Ⅰ and Problem Ⅱ is given andthe general expression of solutions for Problem Ⅰ is derived. Some sufficient conditionsunder which Problem Ⅰ and Problem Ⅱ have an explicit solution is provided. A numer-ical algorithm of the solution for Problem Ⅱ has been presented.

THE POSITIVE SEMIDEFINITE SOLUTION OF THE MATRIX EQUATION (A^TXA, B^TXB) = (C, D)

In this paper, we consider the positive semidefinite solution of the matrix equation (AT X A, BT X B) - (C, D). A necessary and sufficient condition for the existence of such solution is derived using the generalized singular value decomposition.The general forms of positive semidefinite solution are given.

THE OPPENHEIM-TYPE INEQUALITIES FORTHE HADAMARD PRODUCT OF M-MATRIXAND POSITIVE DEFINITE MATRIX

For the lower bound about the determinant of Hadamard product of A and B, where A is a n × n real positive definite matrix and B is a n × n M-matrix, Jianzhou Liu [SLAM J. Matrix Anal. Appl., 18(2)(1997): 305-311]obtained the estimated inequality as follows det(A o B)≥a11b11 nⅡk=2(bkk detAk/detAk-1+detBk/detBk-1(k-1Ei=1 aikaki/aii))=Ln(A,B),where Ak is kth order sequential principal sub-matrix of A. We establish an improved lower bound of the form Yn(A,B)=a11baa nⅡk=2(bkk detAk/detAk-1+akk detBk/detBk-1-detAdetBk/detak-1detBk-1)≥Ln(A,B).For more weaker and practical lower bound, Liu given thatdet(A o B)≥(nⅡi=1 bii)detA+(nⅡi=1 aii)detB(nⅡk=2 k-1Ei=1 aikaki/aiiakk)=(L)n(A,B).We further improve it as Yn(A,B)=(nⅡi=1 bii)detA+(nⅡi=1 aii)detB-(detA)(detB)+max1≤k≤n wn(A,B,k)≥(nⅡi=1 bii)detA+(nⅡi=1 aii)detB-(detA)(detB)≥(L)n(A,B).

THE NECESSARY AND SUFFICIENT CONDITIONS FOR THE SOLVABILITY OF A CLASS OF THE MATRIX INVERSE PROBLEM

Censider the solutions of the matrix inverse problem, which are symmetric positive semide finite on a subspace. Necessary and sufficient conditions for the solvability, as well as the general solution are obtained. The best approximate solution by the above solution set is given. Thus the open problem in [1] is solved.

A MATRIX EQUATION FROM AN INVERSE PROBLEM OF VIBRATION THEORY

The symmetric,positive semidefinite,and positive definite real solutions of the matrix equation XA=YAD from an inverse problem of vibration theory are considered.When D=T the necessary and sufficient conditions for the existence of such solutions and their general forms are derived.

LEAST-SQUARES SOLUTIONS OF X^TAX = B OVER POSITIVE SEMIDEFINITE MATRIXES A

This paper is mainly concerned with solving the following two problems: Problem Ⅰ. Given X ∈ Rn×m, B . Rm×m. Find A ∈ Pn such thatwhereProblem Ⅱ. Given A ∈Rn×n. Find A ∈ SE such thatwhere F is Frobenius norm, and SE denotes the solution set of Problem I.The general solution of Problem I has been given. It is proved that there exists a unique solution for Problem II. The expression of this solution for corresponding Problem II for some special case will be derived.

线性对象的正实控制问题

在时域中考虑线性对象的正实控制（ＰＲＣ）问题．对于一般的广义对象，在状态空间中提出了一个基于线性矩阵不等式（ＬＭＩ）的统一处理ＰＲＣ问题的方法，指出ＰＲＣ问题可解的充分必要条件是与系统的实现有关的三个ＬＭＩ可解，并可利用ＬＭＩ的解构造出所有的正则ＰＲ控制器．此外还提出了降价ＰＲ控制器的存在条件并讨论了可行的综合方法．

半正定的中心对称矩阵反问题

讨论了一类半正定的中心对称矩阵反问题 ,得到了解的具体表达式 ;并就这类矩阵的最佳逼近问题进行了讨论 ,得到了解的存在唯一性 .

输出反馈严格正实控制器设计

基于强严格正实引理，采用线性矩阵不等式方法讨论一般严格正实控制问题的解，给出了任意阶输出反馈严格正实控制器的存在条件和所有控制器的参数化形式。

离散广义系统的鲁棒严格正实控制

研究确定的以及具有范数有界不确定性的离散广义系统的严格正实分析和控制问题.首先给出了确定离散广义系统状态反馈扩展严格正实控制器的存在条件和设计方法;然后利用线性矩阵不等式分析了不确定离散广义系统广义二次稳定且扩展严格正实的条件,讨论了状态反馈使闭环系统广义二次稳定且扩展严格正实问题,给出了状态反馈鲁棒扩展严格正实控制器的综合方法;最后通过数值算例说明了所提出方法的有效性.

线性流行上一类矩阵方程的对称和对称半正定最小二乘解

导出了在两类线性流形上对称矩阵类和对称半正定矩阵类中一类矩阵方程的最小二乘解的一般表达式,并讨论了解对于已知矩阵的最佳逼近问题.

鲁棒严格正实控制器设计

基于强严格正实引理使用线性矩阵不等式方法讨论了参数不确定线性系统鲁棒严格正实控制器的综合问题 ,提出了二次严格正实的新概念 ,证明了静态状态反馈解的存在性 。

酉不变范数不等式

针对酉不变范数不等式问题,先给出一组新的标量不等式,进而利用新标量不等式与谱分解定理,得到关于矩阵酉不变范数新的不等式。与前人的结果相比较,新不等式推广了相关文献的结果。

应用LMI设计鲁棒严格正实传递函数

讨论稳定的实区间多项式族是否存在一个实多项式使之严格正实化问题。通过线性矩阵不等式（ＬＭＩ）给出了存在此多项式的充要条件，并利用Ｍａｔｌａｂ 中的ＬＭＩ软件包求解满足条件的不变多项式。具体算例说明了该算法的有效性。

矩阵乘积的特征值与奇异值不等式

获得矩阵乘积的特征值与奇异值的不等式。(1 )设 A、B为非负定 Hermite阵 ,1≤ i1 <… <ik≤ l≤ n,则∏kt=1λl- it+1 (AB)≥ ∏kt=1λl- t+1 (A)λn- it+1 (B) ;∏kt=1λn- l+it(AB)≤ ∏kt=1λn- l+t(A)λit(B)。 (2 )设 A、B∈ Cn× n,1≤ i1 <… <ik≤ l≤ n,则∏kt=1σl- it+1 (AB)≥ ∏kt=1σl- t+1 (A)σn- it+1 (B) ;∏kt=1σn- l+it(AB)≤ ∏kt=1σn- l+t(A)σit(B)。

逆向Styan矩阵不等式的推广

对Hermitian半正定矩阵来说,无论其经典形式还是推广形式,Styan矩阵不等式都是互为确定的,因此可称为互逆矩阵不等式.本文给出了一对互逆的无约束条件的Hermitian半正定矩阵的矩阵不等式,以此为基本工具,得到了原已有文献给出的Hermitian半正定矩阵的Styan矩阵不等式的逆向表达式.由文中讨论方法可得到这些互逆的矩阵不等式等式成立的充分必要条件.

奇异系统时滞依赖的非脆弱鲁棒正实控制

研究了非脆弱鲁棒正实控制的问题,针对不确定时变时滞奇异系统,同时考虑对象和控制器本身的不确定性,选取了适当的Lyapunov函数,以线性矩阵不等式的形式给出了存在时滞依赖鲁棒正实控制器的充分条件.

严格正实广义系统的鲁棒性分析与输出反馈控制

讨论了一类广义系统的鲁棒严格正实分析与综合问题,其中各个不确定参数矩阵具有线性分式形式.基于线性矩阵不等式,给出了这类系统对所有容许不确定性扩展严格正实的条件,并设计动态输出反馈控制器,使闭环系统容许且扩展严格正实.结果表明,这一问题可以转化为确定广义系统的正实控制问题.