Local Lyapunov Exponents and characteristics of fixed／periodic points embedded within a chaotic attractor

A chaotic dynamical system is characterized by a positive averaged exponential separation of two neighboring trajectories over a chaotic attractor. Knowledge of the Largest Lyapunov Exponent λ1 of a dynamical system over a bounded attractor is necessary and sufficient for determining whether it is chaotic (λ1＞0) or not (λ1≤0). We intended in this work to elaborate the connection between Local Lyapunov Exponents and the Largest Lyapunov Exponent where an altemative method to calculate λ1has emerged. Finally, we investigated some characteristics of the fixed points and periodic orbits embedded within a chaotic attractor which led to the conclusion of the existence of chaotic attractors that may not embed in any fixed point or periodic orbit within it.     

Optimization of total harmonic current distortion and torque pulsation reduction in high-power induction motors using genetic algorithms

This paper presents a powerful application of genetic algorithm （GA） for the minimization of the total harmonic current distortion （THCD） in high-power induction motors fed by voltage source inverters, based on an approximate harmonic model. That is, having defined a desired fundamental output voltage, optimal pulse patterns （switching angles） are determined to produce the fundamental output voltage while minimizing the THCD. The complete results for the two cases of three and five switching instants in the first quarter period of pulse width modulation （PWM） waveform are presented. Presence of harmonics in the stator excitation leads to a pulsing-torque component. Considering the fact that if the pulsing-torques are at low frequencies, they can cause troublesome speed fluctuations, shaft fatigue, and unsatisfactory performance in the feedback control system, the 5th, 7th, 1 lth, and 13th current harmonics （in the case of five switching angles） are constrained at some pre-specified values, to mitigate the detrimental effects of low-frequency harmonics. At the same time, the THCD is optimized while the required fundamental output voltage is maintained.     

三相软开关PWM变流器电流极性检测与电流补偿方法

A novel software implementation for current polarity detection and current compensation is presented. For a three-phase zero-voltage soft-switching （ZVS） PWM converter based on phase and amplitude control （PAC）, when saw-tooth carriers with alternate positive and negative slopes are adopted, the positive or negative slopes are chosen according to the phase current polarity. Since polarity reversal causes current distortion, current at the instant of reversal should be compensated for. Based on the characteristic of unity power factor converter in rectification and regeneration modes, a software implementation for current polarity detection is proposed. Distortion of current zero-crossing caused by using saw-tooth carriers with alternate positive and negative slopes is analyzed, and the relevant compensation method is proposed. Experimental study with a 1.5 kW device shows that phase current has a small harmonic content and power factor is high both in rectification and regeneration modes.     

Translational torsional coupled model based nonlinear dynamic analysis of an NGW planetary gear train

This paper aims to investigate the nonlinear dynamic behaviors of an NGW planetary gear train with multi-clearances and manufacturing/assembling errors. For this purpose, an analytical translational ? torsional coupled dynamic model is developed considering the effects of time-varying stiffness, gear backlashes and component errors. Based on the proposed model, the nonlinear differential equations of motion are derived and solved iteratively by the Runge-Kutta method. An NGW planetary gear reducer with three planets is taken as an example to analyze the effects of nonlinear factors. The results indicate that the backlashes induce complicated nonlinear dynamic behaviors in the gear train. With the increment of the backlashes, the gear system has experienced periodic responses, quasi-periodic response and chaos responses in sequence. When the planetary gear system is in a chaotic motion state, the vibration amplitude increases sharply, causing severe vibration and noise. The present study provides a fundamental basis for design and parameter optimization of NGW planetary gear trains.     

Equivalent response estimation of structural systems subjected to long-period ground motion

Long-period ground motion has become an important consideration because of the increasing number of large and long-period structures. Therefore, a thorough investigation on the formation and characteristics of longperiod ground motion is desirable for engineering applications. In this work, an analytical study is performed to examine the effect of several parameters and the combining mode for equivalent harmonic components on the dynamic response of systems. The results of the work show that the harmonic components in equivalent ground motion are evidently influenced by the intensity rise time, duration, phase and combining mode. Moreover, the long-period ground motions are simplified and simulated by separate harmonic components through proper combination. The findings of the work are believed to be useful in the selection of input ground motion in structural seismic analysis.     

Position Sensorless Control for Permanent Magnet Synchronous Motor Using Sliding Mode Observer

An approach of position sensorless control for permanent magnet synchronous motor （ PMSM ） is put forward based on a sliding mode observer. The mathematical model of PMSM in a stationary αβ reference frame is adopted, and the system is controlled by the digital signal processor （ DSP; TMS320LF2407 according to the control achieve closed loop operation of the motor, the stator theory of sliding mode observer. In order to magnetic field should be vertical with the rotor magnetic field and be synchronous with rotor rotating, so the position and speed of PMSM is estimated in real time and the estimated position is modified continuously. The simulation results indicate that the proposed observer has high precision is more robust to the parametric variation and load in estimation of PMSM position and speed, and torque disturbance.     

Complex Dynamics Caused by Torus Bifurcation in Power Systems

Torus bifurcation is a relatively complicated bifurcation caused by a pair of complex conjugate Floquet multipliers coming out of unit circle on the Poincare section. A three-bus system is employed to reveal the relationship between torus bifurcation and some complex dynamics. Based on theoretical analysis and simulation studies, it is found that torus bifurcation is a typical route to chaos in power system. Some complex dynamics usually occur after a torus bifurcation, such as self-organization, deep bifurcations, exquisite structure, coexistence of chaos and divergence. It is also found that chaos has close relationship with various instability scenarios of power systems. Studies of this paper are helpful to understand the mechanism of torus bifurcation in power system and relationship of chaos and power system instabilities.     

A new optimization algorithm based on chaos

INTRODUCTION Chaos (Wang et al., 2002) is a common nonlin- ear phenomenon, whose action is complex and similar to that of randomness. The characteristics of chaos being highly sensitive to the initial value of chaos make a world of differences due to the ergodic prop- erty of the phase space—chaos can go through all states in certain ranges without repetition; the inher- ent randomness of the system—means that chaos behavior is similar to randomness which is disorderly; but at the same t…     

关于混沌洛伦兹系统和陈系统中的广义投影同步

1 Introduction Since Pecora and Carroll[1]showed that it is possibleto synchronize two identical chaotic systems , chaossynchronization has been intensively and extensivelystudied due to its potential applications in secure com-munication,ecological systems ,systemidentification,etc.(see [2] and a huge volume of references citedtherein) . Among all kinds of chaos synchronizations ,projec-tive synchronization is one of the most noticeableones .This kind of synchronization was first observedin …     

Optimal state feedback control of brushless direct-current motor drive systems based on Lyapunov stability criterion

This paper develops a unified methodology for a real-time speed control of brushless direct-current motor drive systems in the presence of measurement noise and load torque disturbance. First, the mathematical model and hardware structure of system is established. Next, an optimal state feed back controller using the Kalman filter state estimation technique is derived. This is followed by an adaptive control algorithm to compensate for the effects of noise and disturbance. Those two algorithms working together can provide a very-high-speed regulation and dynamic response over a wide range of operating conditions. Simulated responses are presented to highlight the effectiveness of the proposed control strategy.     

混沌频率调制技术在移相全桥变换器抑制EMI的应用

由于混沌信号的连续频谱的特性,可将其用于开关电源消除开关信号谐波的尖峰,从而抑制EMI。本文提出一种将混沌调制技术应用于移相全桥变换器的方法,该方法利用蔡氏电路设计了混沌信号电路,通过产生的混沌信号驱动开关电源PWM芯片的振荡器,实现开关频率的调制,使原本离散的开关信号频谱拓展到一定的频率范围。仿真结果表明该方法在确保系统稳定的基础上,能实现EMI的抑制。     

简谐激励下输流管的稳定性和混沌运动

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混沌调制对改善直流变换器电磁兼容性的研究及仿真

混沌信号具有类随机、连续频谱的特性,混沌调制用于直流开关变换器可以扩展频谱,抑制电磁干扰（EMI）。但实际产生的混沌信号频谱具有一定的范围,如由蔡氏电路产生的模拟混沌信号,具有一个特殊频率并以之为中心左右基本对称的频谱范围,这个频率为中心频率并由电路的实际参数所决定。本文以BUCK变换器为例,采用外接蔡氏电路作为模拟混沌信号发生器,分别选用合适中心频率的混沌信号,实施混沌化占空比和混沌化频率的方案,通过计算机仿真结果进行对比,验证了混沌调制具有改善电磁兼容（EMC）的性能,且混沌化频率的方案抑制EMI效果更明显。     

一类新混沌系统的同步控制研究

新Lu混沌系统是一类重要的新混沌系统,它显示了不同于以往混沌系统的复杂的动力学特性．文章主要研究了新Lu混沌系统与统一混沌系统的同步控制问题．基于Lyapunov稳定性定理,利用主动控制和非线性反馈控制均实现了两混沌系统的异结构同步．同时,严格的数学理论分析和数据仿真结果都证明了控制方法的有效性．     

Impulsive homoclinic chaos in Van der Pol Jerk system

A 3D continuous autonomous chaotic system is reported, which contains a cubic term and six system parameters. Basic dynamic properties of the new Van der Pol Jerk system are studied by means of theoretical analysis and numerical simulation. Based on the Silnikov theorem, the chaotic characterisitics of the dynamic system are discussed. Using Cardano formula and series solution of differential equation, eigenvalue problem and the existence of homoclinic orbit are studied. Furthermore, a rigorous proof for th...     

激光混沌的广义同步

光学泵浦单模环形铵分子激光器能显示包括信周期分岔混沌，间歇性混沌以及类洛仑兹螺旋形混沌等各种混沌动力学特性，基于该激光器的混沌特性，作者设计了不同的实验研究耦合混沌系统间的相互作用，文中报道了研究结果，展示了以下方面的实验证据，单向耦合混沌系统间的频率锁定及广义混沌同步双向耦合混沌激光模间的反位相频率锁定，反位相混沌同步以及完全严格混沌同步，通过分析所观察到的不同混沌同步形式，得出耦合混沌系统间同步的物理起源的仍然是系统间的位相相互作用，特别是所观察到的不同形式的混沌同步是由于不同程度位相锁定的结果。     

一个混沌纠缠系统的动力学分析

通过一系列动力学分析,验证了一个纠缠系统是混沌的.当混沌纠缠实现时,所有的平衡点是不稳定的鞍结点.数值计算显示这个系统有一个正的Lyapunov指数,这表明该系统是混沌的.通过局部放大的分岔图验证了系统由倍周期分岔通向混沌的过程,并分析了该混沌系统的Hopf分岔现象.     

混沌信号对通信系统攻击方法的研究

设想把混沌理论应用到电子对抗中,提出混沌信号干扰攻击敌方通信系统思想方法,提出混沌屏蔽攻击方法.混沌屏蔽攻击的物理机制是:强混沌信号可以直接屏蔽信息信号,小混沌信号可以扰乱信息信号.还发现联合混沌信号和噪声信号其攻击效果确能增加了通信系统的解调难度.     

Control uncertain continuous-time chaotic dynamical system

INTRODUCTIONChaoticmotionisacomplexnonlinearmo tion ,whoseorbitstrajectoryinthephaseplaneisverycomplexbutnotstochastic.Chaosplaysanimportantroleindynamicalsystemsandisap pliedinmanyfieldssuchasphysics ,chemistry,economics,andsoon (Heetal.,2 0 0 2 ;Tongeta…     

论高校图书馆管理中的混沌序

高校图书馆管理系统是复杂混沌系统,混沌是这个管理系统的一种本真性态。高校图书馆管理系统的混沌特性体现它的开放性、内禀随机性和对初始条件的敏感依赖性。现代混沌理论意义上的混沌序是一个复杂序。这一复杂序本身表征为有序中有无序、无序中有有序,并且二者是可以相互转化的。高校图书馆管理系统也存在着这样的混沌序,这表明混沌管理理论中的混沌序为高校图书馆管理提供了正确的管理方法和管理模式。