李雅普诺夫指数谱的研究与仿真

李雅普诺夫指数在研究动力系统的分岔、混沌运动特征中起着重要的作用。该文介绍了李雅普诺夫指数的定义、计算原理及数值计算的实现方法，应用Matlab软件，编制了计算李雅普诺夫指数的程序，分析了一维、二维和三维非线性动力系统中分岔和混沌与李雅普诺夫指数之间的关系。绘制了逻辑斯蒂映射、埃农映射和洛仑兹方程的分岔图，并计算了相应的李雅普诺夫指数。实例的计算机仿真表明李雅普诺夫指数是研究分岔、混沌运动，解决工程实际问题的有效方法之一。     

一类离散时滞系统的复杂动力学行为研究

在混沌巨大潜在应用前景的推动下,混沌控制已经引起了学者们越来越浓厚的研究兴趣.混沌的一些特征参量为系统是否呈现混沌行为提供了直接的判断依据.针对一类离散时滞系统,研究系统动力学行为随时滞参数变化的情况.在得到系统有界的前提下,分析一类基于传染病传播机理的复杂网络模型,研究传染病的传播动力学行为随最大李雅普诺夫指数变化的情况.基于Wolf重构法,仿真出系统最大李雅普诺夫指数随着时滞参数变化的曲线图.当最大李雅普诺夫指数大于零,系统呈现混沌行为,传染病在有界区域内传播;反之,系统收敛,传染病则会慢慢的消失.     

基于脉冲耦合神经网络的混沌控制

根据脉冲耦合神经网络(PCNN)能产生混沌现象,研究了对配置混沌PCNN系统的李雅普诺夫指数使其稳定于期望点的方法。根据特定期望点的情况,按需要配置负的李雅普诺夫指数,产生不同的控制序列来改变混沌PCNN系统,达到稳定控制的要求。仿真和实验结果证明了该算法的有效性,实现了混沌PCNN系统从混沌状态到稳定期望点的控制。     

基于混沌理论的工业过程控制

通过改变系统李雅普诺夫指数对工业过程控制 中的混沌现象进行控制，并提出了一种确定控制区域的方法．理论分析和仿真实验结果表明 ，该控制策略是有效的，可以实现系统的快速稳定．     

贵州电网短期负荷时间序列的混沌性仿真检验

不直接考虑气候等随机因素,根据过去贵州电网短期负荷时间序列.利用小数据量方法计算最大李雅普诺夫指数,并通过李雅普诺夫指数定义的性质对贵州电网短期负荷时间序列进行混沌性仿真检验,结果具有混沌性.     

变形Rikitake系统的混沌同步和应用

针对Rikitake混沌系统同步问题,提出一个新的发电机系统,首先通过对新系统的分维、李雅普诺夫指数和功率谱的研究和计算,判定新系统存在混沌行为,接着采用自适应控制方法设计了自适应控制器和参数更新规则,通过李雅普诺夫稳定性理论和Barbalat引理,理论上证明了控制器和参数更新规则可使得驱动系统和未知参数的响应系统渐近地达到同步,并且可以清晰辨识出响应系统的未知参数,并运用混沌掩盖的方法将该同步方法应用于保密通信,数值仿真进一步证明了控制器的有效性和可行性。     

具有有界控制输入的状态反馈控制系统闭环稳定性

本文基于李雅普诺夫定理,给出了具有有界控制输入的离散时间系统和连续时间控制系统的闭环渐近稳定性判据。利用不考虑控制约束时闭环系统李雅普诺夫矩阵方程解,得出了当控制输入有界时,线性状态反馈控制系统为渐近稳定的充分条件。这些判据具有简单的形式,并且易于计算。     

自适应延迟反馈控制混沌

本文在延迟反馈控制混沌方法的基础上,提出了一种自适应调节延时时间,控制刚度的延时反馈控制方法,可以有效地把混沌控制到所需的周期轨道上去,控制时初始微扰较小,控制刚度不需计算李雅普诺夫指数来确定。     

一种带绝对值项系统的分岔、激变与混沌

研究了一种含有绝对值项的三维微分动力系统,用李雅普诺夫方法得到了系统发生第一次Hopf分岔的条件.利用相轨迹图、分岔图、最大李雅普诺夫指数谱等非线性动力学分析方法,分析了该系统从规则运动转化到混沌运动的规律.该系统是按照Feigenbaum途径(倍周期分岔)通向混沌的,在混沌区域存在周期窗口.当参数达到激变临界点时,混沌吸引子和不稳周期轨道在吸引子边界上碰撞,发生边界激变,激变临界值的领域内还存在相对长时间的瞬态混沌过程.     

不确定性离散广义系统带有观测器的控制

利用带参数的李雅普诺夫函数，讨论了一类具有不确定性离散广义系统带有观测器控制的条件，参数的引进使设计具有灵活性。     

基于秩一摄动理论配置Lyapunov指数的新方法

本文提出一种混沌控制与反控制的新算法。利用秩一摄动理论精确摄动离散受控系统矩阵的特征值,来配置Lyapunov指数。新算法完全吻合混沌的Lyapunov指数判据。既能更准确地配置正的Lyapunov指数,又能配置传统算法无法获得的负Lyapunov指数。仿真结果显示了新算法的有效性。     

Distribution of Controlled Lyapunov Exponents via the Lai-Chen Algorithm

The Lai-Chen algorithm, an extended feedback control scheme of the original Chen- Lai algorithm, was proposed to gradually make an arbitrarily given discrete-time dynamical system chaotic in terms of possessing positive Lyapunov exponents with uniformly bounded orbits. In this paper, based on the Monte Carlo method, we further study the distribution of the controlled Lyapunov exponents generated by the Lai-Chen algorithm.     

On the relationship between the sample path and moment lyapunov exponents for jump linear systems

In this paper, we study the relationship between the sample and moment Lyapunov exponents for jump linear systems. Using a large deviation theorem, a modified version of Arnold's formula for connecting sample path and moment Lyapunov exponents for continuous-time linear stochastic systems is extended to discrete-time jump linear systems. Sample path stability properties of linear stochastic systems are determined by the top Lyapunov exponent and relating sample and moment Lyapunov exponents may be useful for developing computationally efficient methods for determining the almost-sure (sample path) stability of linear stochastic systems.     

非高斯列维噪声激励下非线性系统的Lyapunov指数

研究了非高斯列维噪声作用下非线性系统的渐近线性化方法和Lyapunov指数.利用渐近线性化方法将非线性系统线性化,通过系统的响应轨迹验证了该方法的有效性.通过广义的伊藤法则公式,推导出了列维噪声驱动下Lyapunov指数的一般表达式.给出当参数变化时,非线性系统的随机稳定性分析.     

On stability analysis via Lyapunov exponents calculated based on radial basis function networks

The concept of Lyapunov exponents is a powerful tool for analysing the stability of nonlinear dynamic systems, especially when the mathematical models of the systems are available. For real world systems, such models are often unknown. Estimating Lyapunov exponents using a time series has the advantage in that no mathematical model is required. However the time-series-based methods are believed to be reliable only for estimating positive exponents. Furthermore, when nonlinear mapping is applied for deriving the neighbourhood-to-neighbourhood matrices, the loads of mathematical deduction and programming increase significantly, which makes it unfeasible to nonlinear systems with high dimensions. In contrary, the model-based methods are constructive and reliable for calculating both positive and non-positive exponents. The use of the system Jacobians is the key to the advantage of the model-based methods. In this article, a novel approach is proposed, where the system Jacobians are derived based on system approximation using the radial basis function network. The proposed method inherits the advantage of the model-based methods, yet no mathematical model is required. Two case studies are presented to demonstrate the efficacy of the proposed method. We believe that the work can contribute to the stability analysis of nonlinear systems of which the dynamics are either difficult to model due to complexities or unknown.     

带干摩擦的非光滑动力系统Lyapunov指数的数值计算

对带干摩擦的非光滑动力系统,在不连续点利用闭上链(cocycle)得到一个传递矩阵,由此给出一种非光滑动力系统Lyapunov指数的数值计算方法.该方法是根据计算光滑动力系统Lyapunov指数的数值方法而提出的.通过对带干摩擦的动力系统进行Lyapunov指数的数值计算,结合时间历程图和Poincare映射对其动力学特性进行了分析.数值结果表明该方法的可行性和有效性,与一般的计算非光滑动力系统Lyapunov指数的数值算法相比,该方法更便于数值计算.     

A new multi-stable fractional-order four-dimensional system with self-excited and hidden chaotic attractors: Dynamic analysis and adaptive synchronization using a novel fuzzy adaptive sliding mode control method

Four-dimensional chaotic systems are a very interesting topic for researchers, given their special features. This paper presents a novel fractional-order four-dimensional chaotic system with self-excited and hidden attractors, which includes only one constant term. The proposed system presents the phenomenon of multi-stability, which means that two or more different dynamics are generated from different initial conditions. It is one of few published works in the last five years belonging to the aforementioned category. Using Lyapunov exponents, the chaotic behavior of the dynamical system is characterized, and the sensitivity of the system to initial conditions is determined. Also, systematic studies of the hidden chaotic behavior in the proposed system are performed using phase portraits and bifurcation transition diagrams. Moreover, a design technique of a new fuzzy adaptive sliding mode control (FASMC) for synchronization of the fractional-order systems has been offered. This control technique combines an adaptive regulation scheme and a fuzzy logic controller with conventional sliding mode control for the synchronization of fractional-order systems. Applying Lyapunov stability theorem, the proposed control technique ensures that the master and slave chaotic systems are synchronized in the presence of dynamic uncertainties and external disturbances. The proposed control technique not only provides high performance in the presence of the dynamic uncertainties and external disturbances, but also avoids the phenomenon of chattering. Simulation results have been presented to illustrate the effectiveness of the presented control scheme.     

一种Lyapunov指数算法及其实现

提出了一种利用周期轨道不同权重计算Lyapunov指数的算法。对混沌序列的周期轨道进行统计，并计算不同的周期轨道的Lyapunov指数，依据周期轨道的权重加权求和得到整个混沌吸引子的平均Lyapunov指数。深入讨论了初始值等对平均Lyapunov指数的影响。该算法不用舍去开始迭代点，适用于复杂混沌系统。     

基于无退化混沌系统的序列密码研究

针对连续时间混沌系统的退化问题,提出一种基于矩阵特征值配置的方法来构造具有多个正Lyapunov指数的连续时间混沌系统。提出一种基于特征值定义的特征值配置方法,通过设计一个线性反馈控制器,可以配置任何系统为以稳定焦点为原点的渐近稳定线性系统;通过设计一个非线性反馈控制器来配置多个正Lyapunov指数。相比于现有算法,对于任意受控系统,该方法都能系统地配置该受控系统的Lyapunov指数,使之成为无退化混沌系统。将该方法得到的无退化混沌系统转换为二进制序列,对得到的混沌序列进行分析后证明该序列具有良好的加密特性。