随机激励的耗散的哈密尔顿系统的平稳解

本文首先为一般的随机激励的耗散的哈密尔顿系统得到精确的平稳解,然后在此基础上为类似而更为一般的系统发展了等效非线性系统法。     

随机结构系统的一般实矩阵特征值问题的概率分析

由于工程实际结构的复杂性和所用材料在统计上的离散性以及测量、加工、制造误差的存在，必然导致具有随机参数的随机结构振动系统，按结构参数的性质来划分，随机振动问题包括两方面内容：(1)确定结构问题；(2)随机结构问题。本文以现代数学理论为依托，研究了随机结构系统的一般实矩阵的特征值问题。根据Kronecker代数、向量值和矩阵值函数的灵敏度分析、一般二阶矩法和概率摄动技术给出了计算随机结构系统的一般实矩阵的特征值和特征向量的数值方法，可以有效地得出随机结构系统的一般实矩阵的特征向量的统计量，发展了2D矩阵值函数的随机结构系统的特征值问题概率分析理论。     

广义概率密度演化方程的再生核质点加密算法

采用一般质点近似和再生核质点近似表示系统响应量,给出了动力系统响应量的一般表达式。在此基础上,发展了一类求解广义概率密度演化方程的再生核质点加密算法,给出了详细求解步骤。以单自由度系统为例,从响应概率密度的角度考察了再生核质点加密算法的精度。以多自由度框架结构为例,验证了再生核质点加密算法求取非线性随机动力系统响应概率密度的正确性。     

APPELL方程和TZNOFF方程在一般非完整系统上的推广

本文给出一个适用于任何阶非完整系统的变分原理。Gauss原理可作为推论由之导出。由此原理出发,将Appell方程和Tzènoff方程推广到一般非完整系统,以一个二阶非完整系统为例,说明所得方程的应用。     

几类非线性系统平稳随机响应的概率密度

本文考虑非保守力依赖于系统能量的非线性系统,构造了四类这种系统对白噪声外激与/或参激的平稳响应的精确概率密度,讨论了存在平稳响应的条件。同时指出,迄今为止已有的非线性系统平稳随机响应的精确解皆属本文给出一般结果的特殊情形。最后还给出几个例子说明一般结果。     

运动稳定性的研究进展和趋势

本文概述运动稳定性学科在力学系统、控制系统、大系统、冲击系统、不确定系统以及一般理论等方面的研究进展和趋势。      

方程x=f（t,x,ε）的横截同宿轨道

本文的主要目的是把Ｍｅｌｎｉｋｏｖ方法推广到一般的系统ｘ＝ｆ（ｔ，ｘ，ε），利用指数二分性和Ｌｉａｐｕｎｏｖ－Ｓｃｈｍｉｄｔ方法，我们对一般系统构造了一个Ｍｅｌｎｉｋｏｖ型函数。     

阻尼振动系统存在全实模态的条件

1.引言阻尼矩阵是描述系统运动微分方程的重要物理参数.对于系统的响应分析,阻尼项不可忽略.由于阻尼因素的复杂性,系统运动方程一般难以在对应的实模态空间中解耦.因此需要采用复模态理论进行动力分析,增加了分析计算的复杂性.如何判断阻尼系统能否化为等价的无阻尼系统及相应的形式,十分必要.本文根据矩阵函数的坐标变换关系,将系统化为与之     

非线性系统参数辩识的一种频域模型

本文基于对非线性系统的可分离性假设，将非线性弹性力和阻尼力分别分解为物理坐标下各点间相对位移和相对速度的幂级数函数，导出了一般多自由度非线性系统在恒幅激励下的广义频率响应函数与输入输出之间的迭代关系式，提出了非线性系统中基本线性部分的概念，进而了一种在实验条件下的系统物理参数辩识方法。     

我国运动稳定性研究的新进展

综述了近年来我国运动稳定性(包括力学系统、控制系统、人口系统、生态系统和大系统的稳定性)及其一般理论的研究进展。      

Lagrangian block diagonalization

Relative equilibria, i.e., steady motions associated to specified group motions, are an important class of steady motions of Hamiltonian and Lagrangian systems with symmetry. Relative equilibria can be identified by means of a variational principle on the tangent space of the configuration manifold. We show that relative equilibria can also be found by means of a variational principle on the configuration manifold itself. Formal stability of a relative equilibrium corresponds to definiteness of the second variation of the energymomentum functional, which is a specified combination of the total energy and the group momentum, on an appropriate subspace. We decompose this subspace into three subspaces by means of the Legendre transformation and the group action and show that the second variation block diagonalizes with respect to these subspaces. The techniques employed here are a generalization of the reduced energy-momentum method of Simoet al. (1991), which applies only to simple mechanical systems, to a more general class of conservative systems, including systems on which the symmetry group does not act freely. We briefly discuss a generalization of a result due to Patrick (1990) that provides conditions under which formal stability implies nonlinear orbital stability. Several simple examples, including natural mechanical systems, are used to illustrate the block diagonalization procedure.     

The application of the asymptotic method to a clas of strongly nonlinear systems

In this paper, according to the form of the asymptotic solution of papers [1, 2], the asymptotic method is extended to the following a class of more general strong nonlinear vibration systems where g and f are the nonlinear analytical-functions of x and x, and ε>0 is a small parameter. We assume that the derivative system corresponding to ε=0 has periodic solution. The recurrence equations of the asymptotic solution for the system(0.1)are deduced in this paper, and they are applied to practical examples.     

A study of the construction of lyapunov function for a class of fourth order nonlinear systems

ＡＳＴＵＤＹＯＦＴＨＥＣＯＮＳＴＲＵＣＴＩＯＮＯＦＬＹＡＰＵＮＯＶＦＵＮＣＴＩＯＮＦＯＲＡＣＬＡＳＳＯＦＦＯＵＲＴＨＯＲＤＥＲＮＯＮＬＩＮＥＡＲＳＹＳＴＥＭＳＬｉａｎｇＺａｉ－ｚｈｏｎｇ（梁在中）（ＤｅｐａｒｔｍｅｎｔｏｆＡｐｐｌｉｅｄＭａｔｈｅｍａ...     

Technical stability of nonlinear time-varying systems with small parameters

ＩｎｔｒｏｄｕｃｔｉｏｎＳｔａｂｉｌｉｔｙｐｒｏｂｌｅｍｓａｒｉｓｉｎｇｆｒｏｍｅｎｇｉｎｅｅｒｉｎｇａｐｐｌｉｃａｔｉｏｎｓａｒｅｕｓｕａｌｌｙｒｅｌａｔｅｄｔｏｃｅｒｔａｉｎｑｕａｎｔｉｔｉｅｓｔｈａｔｓｐｅｃｉｆｙｔｈｅｓｔｒｅｎｇｔｈｏｆａｄｍｉｓｓｉｂｌｅｄｉｓｔｕｒｂａｎｃｅｓａｎｄｔｈｅｌｉｍｉｔｓｏｎｄｅｖｉａｔｉｏｎｓｏｆｍｏｔｉｏｎｏｆｔｈｅｄｉｓｔｕｒｂｅｄｓｙｓｔｅｍ .Ｉｎｔｈｉｓｒｅｇａｒｄ ,ｔｈｅｃｏｎｖｅｎｔｉｏｎａｌＬｉａｐｕｎｏｖｓｔａｂｉｌｉｔｙｃｏｎｃｅｐｔ…     

多体系统Lagrange方程数值算法的研究进展

Lagrange方法是建立多体系统动力学方程的普遍方法之一, 其方程的形式为常微分方程组或微分-代数方程组,数值计算与数 值分析是研究多体系统动力学特性的重要方法。本文简要介绍了多 体系统动 力学方程的第一、二类Lagrange方程和修正的Lagrange方 程的基本形式及这些方程的正则形式,着重介绍了正则方程在数值 计算中的特点,就多体系统Lagrange方程的隐式算法、辛算法和多 体系统动力学特性的数值分析方法(包括数值仿真、 Poincarè映射 和Lyapunov指数的计算方法)的研究现状进行了综述。     

Component Mode Synthesis Using Nonlinear Normal Modes

This paper describes a methodology for developing reduced-order dynamic models of structural systems that are composed of an assembly of nonlinear component structures. The approach is a nonlinear extension of the fixed-interface component mode synthesis (CMS) technique developed for linear structures by Hurty and modified by Craig and Bampton. Specifically, the case of nonlinear substructures is handled by using fixed-interface nonlinear normal modes (NNMs). These normal modes are constructed for the various substructures using an invariant manifold approach, and are then coupled through the traditional linear constraint modes (i.e., the static deformation shapes produced by unit interface displacements). A class of systems is used to demonstrate the concept and show the effectiveness of the proposed procedure. Simulation results show that the reduced-order model (ROM) obtained from the proposed procedure outperforms the ROM obtained from the classical fixed-interface linear CMS approach as applied to a nonlinear structure. The proposed method is readily applicable to large-scale nonlinear structural systems that are based on finite-element models.     

强非线性振动系统的渐近解法

本文推广文[1]中方法于求解广泛一类强非线性振动系统,导出了适于近似定性分析和定量计算的简便公式。作为例子研究了修正的Vander Pol振子,最后给出数字Poincaré映射结果,从近似定性分析和定量计算两方面证明了本文求得的方法的有效性。     

Almost disturbance decoupling for a class of minimum-phase higher-order cascade nonlinear systems

IntroductionThealmostdisturbancedecouplingproblemwasformulatedandsolvedforlinearsystemsbyWillems[1,2 ].Fornonlinearsystems,mostoftheexistingsolutionstotheADDproblemareestablishedbasedtheassumptionsonthecontrolledplantsarefeedbacklinearizable (atleastpartially) [3 - 5 ].Especially ,theresultofRef.[4 ]wasextendedtoalargeclassofminimum_phasenonlinearsystems[5 ].Butwhenthesystemunderconsiderationisinherentlynonlinear,thecommonL2 _gaincharacterizationisnotappropriatetodescribetheADDproblemforhi…     

Multiwavelet Constructions and Volterra Kernel Identification

The Volterra series is commonly used for the modeling of nonlinear dynamical systems. In general, however, a large number of terms are needed to represent Volterra kernels, with the number of required terms increasing exponentially with the order of the kernel. Therefore, reduced-order kernel representations are needed in order to employ the Volterra series in engineering practice. This paper presents an approach whereby multiwavelets are used to obtain low-order estimates of first-, second-, and third-order Volterra kernels. A family of multiwavelets is constructed from the classical finite element basis functions using the technique of intertwining. The resulting multiwavelets are piecewise-polynomial, orthonormal, compactly-supported, and can be constructed with arbitrary approximation order. Furthermore, these multiwavelets are easily adapted to the domains of support of the Volterra kernels. In contrast, most wavelet families do not possess this characteristic. Higher-dimensional multiwavelets can easily be constructed by taking tensor products of the original one-dimensional functions. Therefore, it is straightforward to extend this approach to the representation of higher-order Volterra kernels. This kernel identification algorithm is demonstrated on a prototypical oscillator with a quadratic stiffness nonlinearity. For this system, it is shown that accurate kernel estimates can be obtained in terms of a relatively small number of wavelet coefficients. These results indicate the potential of the multiwavelet-based algorithm for obtaining reduced-order models for a large class of weakly nonlinear systems.