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时滞Lienard非线性系统的Hopf分岔 总被引:3,自引:0,他引:3
本文研究了Lienard非线性时滞系统的线性稳定性和Hopf分岔,考究了特征方程随两参数变化时根的分布,应用中心流形和范式分析失去线性稳定性出现的Hopf分岔及其稳定性。 相似文献
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复杂气固两相系统的微观结构 总被引:2,自引:0,他引:2
流化床中的气固两相流动是一个高度复杂的非线性混沌系统。本文利用激光粒子动态分析仪(PDA)得到的循环流化床中颗粒脉动速度信号,采用FFT分析了脉动信号的宽频谱特征,在此基础上应用小波法分析了脉动信号的动态特征,得到了颗粒脉动速度的微观结构,指出颗粒脉动速度的非线性特性是流化床具有混沌特性的根源,且在不同的尺度上颗粒脉动速度表现出各向异性的特征。 相似文献
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本文根据直梁有限元模型的特点将特征方程KX=λMX中K、M矩阵表为若干结构参数的函数,即K=K(p_1,p_2,…p_m),M=M(q_1q,q_2,…q_m).从而导出以结构参数为未知量的逆特征方程,并分析了可解的条件及结构参数对特征数据的敏感性等问题. 相似文献
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二次特征矩阵表示的特征值有界性分析 总被引:1,自引:0,他引:1
采用二次特征矩阵近似表示精确有限元和精确动态子结构分析中得出的超越或非线性动态刚度阵,并证明了在满足一定条件的前提下,二次特征阵给出的特征值是精确刚度阵特征值的上界或下界。 相似文献
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冲击载荷作用下韧——脆复合板结构中脆性材料破碎的实验和数值模拟 总被引:1,自引:0,他引:1
本文以冲击实验和有限元分析研究了韧-脆复合材料结构中脆性材料的破碎问题,材料的破碎图具有一定的分形特征,其分形维数随冲击载荷的增大而增加,基于实验结果的非线性动力有限元分析对这类破碎图样的演化给出了动态过程模拟。 相似文献
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声系统特征频率的灵敏度分析为其优化设计提供了基础,具有重要意义。边界元法在声学问题的求解中具有独特优势,但因其系统方程系数矩阵的频率相关性导致的非线性特征值问题给声学特征频率的灵敏度分析带来了很大困难。为此,本文首先对非线性特征值问题进行了线性化处理,利用围道积分投影方法将非线性特征方程转换为小规模广义特征方程,然后对其关于设计变量直接求导,并引入左特征向量和转换矩阵构造了一种适用于内外声场的三维声学单/重特征频率灵敏度分析的边界元法。数值算例验证了该方法的适用性,以及对单/重特征频率灵敏度的计算精度。 相似文献
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用带奇性分离的Fourier级数解平面边值问题,改进了不能满足全部边界条件的一般级数解法,得到收敛较好的解析算法。文中证明了级数解法与分离变量法的等价性,由此将分离变量解所得的非线性特征方程转化为多项式方程,为近似算法与渐近分析提供了依据。 相似文献
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研究了反平面状态下压电-压磁夹层结构的圣维南端部效应的衰减特征.夹层结构端部的力-电-磁载荷是自平衡的;外层的边界是应力自由的,但承受四种不同的电磁边界条件,即电学短路/磁学短路、电学短路/磁学开路、电学开路/磁学开路和电学开路/磁学短路.基于磁电弹全耦合的控制方程,推导了问题的精确解和关于衰减率的特征方程.利用得到的特征方程,计算了压电-压磁-压电和压磁-压电-压磁两种夹层结构的衰减率,结果表明电磁边界条件、压电层的材料性能和体积分数对衰减特征有显著的影响.作为特例,分析了压电-弹性-压电夹层结构的衰减特征. 相似文献
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In this paper, the decentralized stabilization control approach based on the dynamic surface control (DSC) is proposed for
a class of large-scale interconnected stochastic nonlinear systems. The proposed approach combined the existing dynamic surface
control (DSC) with back-stepping technique. This approach can overcome the problem of “explosion of complexity” inherent in
the back-stepping method. Thus, the proposed control approach is simpler than the traditional back-stepping control method
for the large-scale interconnected stochastic nonlinear systems. The stability analysis shows that all the signals in the
closed-loop system are uniformly ultimately bounded (UUB). Finally, an example is provided to illustrate the effectiveness
of the proposed control system. 相似文献
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高维、非线性气动弹性系统的模型降阶是当前气动弹性力学与控制领域的研究热点之一.然而国内外现有的非线性模型降阶方法仍存在辨识算法复杂、精度有待提高等问题.本研究提出了一种基于非线性状态空间辨识的跨音速气动弹性模型降阶方法.首先,该方法基于非定常空气动力的单位脉冲响应数据,采用特征系统实现算法对非线性状态空间模型的线性动力学部分进行系统辨识.其次,引入状态和控制输入的非线性函数,采用优化算法对非线性函数的系数矩阵进行优化,进而得到考虑非线性效应的空气动力降阶模型.为了验证该降阶模型在预测跨音速气动弹性力学行为的精确性,本文以三维机翼为研究对象,分别从基于非线性降阶模型的气动力辨识、跨声速颤振边界计算和极限环振荡预测三方面进行了算例验证,并与现有的模型降阶方法进行了对比,进一步说明本文所提出方法的有效性.研究结果表明,该降阶模型对上述三类问题的计算精度与直接流-固耦合方法相吻合,可用于高效预测飞行器跨声速气动弹性力学行为. 相似文献
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In this paper, an adaptive fuzzy backstepping output feedback dynamic surface control (DSC) approach is developed for a class of multiinput and multioutput (MIMO) stochastic nonlinear systems with immeasurable states. Fuzzy logic systems are firstly utilized to approximate the unknown nonlinear functions, and then a fuzzy state observer is designed to estimate the immeasurable states. By combining adaptive backstepping technique and dynamic surface control (DSC) technique, an adaptive fuzzy output feedback backstepping DSC approach is developed. The proposed control method not only overcomes the problem of ??explosion of complexity?? inherent in the backstepping design methods, but also the problem of the immeasurable states. It is proved that all the signals of the closed-loop adaptive control stochastic system are semiglobally uniformly ultimately bounded (SUUB) in probability, and the observer errors and the output of the system converge to a small neighborhood of the origin. Simulation results are provided to show the effectiveness of the proposed approach. 相似文献
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Microbeams are widely seen in micro-electro-mechanical systems and their engineering applications. An active control strategy based on the fuzzy sliding mode control is developed in this research for controlling and stabilizing the nonlinear vibrations of a micro-electro-mechanical beam. An Euler-Bernoulli beam with a fixed-fixed boundary is employed to represent the microbeam, and the geometric nonlinearity of the beam and loading nonlinearity from the electrostatic force are considered. The governing equation of the microbeam is established and transformed into a multi-dimensional dynamic system with the third-order Galerkin method. A stability analysis is provided to show the necessity of the derived multi-dimensional dynamic system, and a chaotic motion is discovered. Then, a control approach is proposed, including a control strategy and a two-phase control method. For describing the application of the control approach developed, control of a chaotic motion of the microbeam is presented. The effectiveness of the active control approach is demonstrated via controlling and stabilizing the nonlinear vibration of the microbeam. 相似文献
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Nonlinear Dynamics - This paper addresses a new nonlinear gain feedback-based neural adaptive dynamic surface control (DSC) method for a sort of strict-feedback nonlinear systems in the presence of... 相似文献
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An Optimal Nonlinear Feedback Control Strategy for Randomly Excited Structural Systems 总被引:16,自引:0,他引:16
A strategy for optimal nonlinear feedback control of randomlyexcited structural systems is proposed based on the stochastic averagingmethod for quasi-Hamiltonian systems and the stochastic dynamicprogramming principle. A randomly excited structural system isformulated as a quasi-Hamiltonian system and the control forces aredivided into conservative and dissipative parts. The conservative partsare designed to change the integrability and resonance of the associatedHamiltonian system and the energy distribution among the controlledsystem. After the conservative parts are determined, the system responseis reduced to a controlled diffusion process by using the stochasticaveraging method. The dissipative parts of control forces are thenobtained from solving the stochastic dynamic programming equation. Boththe responses of uncontrolled and controlled structural systems can bepredicted analytically. Numerical results for a controlled andstochastically excited Duffing oscillator and a two-degree-of-freedomsystem with linear springs and linear and nonlinear dampings, show thatthe proposed control strategy is very effective and efficient. 相似文献
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Edward I-Ho Lin Jerome L. Sackman 《International Journal of Solids and Structures》1975,11(10):1145-1159
A method is developed for the identification of the dynamic properties of nonlinear viscoelastic materials using transient response information arising from impact tests. The solutions of the identification problem and that of the associated nonlinear wave propagation problem are shown to be coupled. They are accomplished via application of the method of lines, the Runge-Kutta-Pouzet integration scheme with automatic step size control and Powell's method of unconstrained optimization. Numerical experiments are performed to demonstrate the feasibility, accuracy and stability of the solution procedure established, and wave propagation experiments are conducted to investigate the applicability of the method to a real physical system. The results are of particular interest in the modeling of nonlinear viscoelastic materials and the identification of systems governed by nonlinear hyperbolic partial-integro-differential equations. 相似文献
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In order to promote the development of chaos in nonlinear systems, and explore more convenient controllers for the engineering
application, a four-dimensional nonlinear dynamic system with only one nonlinear term was constructed and its complex dynamic
characteristics were analyzed, including the phase trajectory map, Lyapunov exponents, and so on. Furthermore, the recursive
backstepping method was proposed to design a different controller; the hyperchaotic system was controlled to an equilibrium
point and a periodic orbit. Theoretical analysis is in agreement with simulation results. The results show that the recursive
backstepping control method can wipe off chaos, and make the hyperchaotic system achieve stable states. The control process
is a smooth transition, and the transition time is short. 相似文献