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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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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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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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一种桁架结构损伤识别的柔度阵法 总被引:27,自引:2,他引:25
利用试验获得的一阶模态参数,提出了一种桁架结构损伤识别的柔度阵法,应用有限元方法柔度阵,建立结构振动特征方程,结构损伤后,引起柔度阵发生改变,从结构振动特征方程出发,对柔度矩阵做关于结构物理参数变化量的一阶泰勒展开,可以确定结构物理参数的变化量,识别结构损伤部位及损伤程度,通过一个桁架结构损伤识别的数值模拟证明了该方法的有效性。 相似文献
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磁场环境对导电薄板磁弹性振动的影响 总被引:2,自引:0,他引:2
给出了磁各导电薄板磁弹性振动的非线性耦合基本方程式,并推得了四边固支矩形薄板振动的特征方程,算例表明,适当给定磁场的强度,可控制该磁场环境中薄板的磁弹性振动特性。 相似文献
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本文基于电子信息设备振冲防护中抗大冲击并兼顾衰减振动要求,通过巧妙的油阻尼结构和金属弹性元件相耦合设计了结构微小的产品样机;样机的多参数匹配冲击试验研究表明该耦合减振器具有强非线性冲击动态特征,在此基础上本文结合理论分析形成复合建模方法建立了原理样机冲击动态特性模型,该建模方法直接引入结构参数,为直接设计具体的器件建立了理论基础;研究表明该减振器性能优越并具有良好的设计可控性,具有广泛的应用前景。 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