基于混沌振子的微弱信号检测方法研究

分析了During方程的基本形式以及During振子的混沌运动，阐述了基于相平面变化进行微弱信号检测的工作原理，并推导出系统发生间歇混沌现象的频差条件和相位差对于系统特性的影响。试验证明：该振子对与参考信号频差较小的周期小信号具有敏感性，对白噪声和与参考信号频差较大的干扰信号具有免疫力。     

基于混沌的故障电弧早期弧声检测方法研究

故障电弧发生之前伴生的微弱电弧声频率主要集中在5～10kHz附近的特征频段里,准确快速检测该频段内特征弧声是否存在,即可判断故障电弧是否将要发生,实现故障电弧的早期预测预警;基于此,提出基于混沌的故障电弧早期弧声信号检测方法,建立以Duffing振子为基础的混沌检测系统;混沌检测系统对可听波7kHz附近3%频段内微弱的早期弧声信号非常敏感,对其它频率的声信号具有良好的抑制作用;当没有电弧声产生时,系统处于混沌状态;而电弧声一旦产生,系统立刻切换到间歇混沌状态;根据间歇混沌的存在与否可以判断特征弧声是否已经产生;试验结果表明,该方法能够可靠检测出微弱故障电弧早期弧声信号.     

基于混沌振子的微弱信号检测

分析了Duffing振子的混沌运动,利用振子相变对与参考信号频差较小的周期小信号具有敏感性和对噪声的免疫力检测微弱周期信号,检测不同频率的信号需要不同频率的参考信号,通过调整系统参数使得振子对不同频率的信号检测具有普遍性.将传感器周期性干扰信号作为对内驱动信号的摄动加入混沌检测中,通过观察混沌振子的状态变量的时间历程图,发现混沌检测系统处于间歇混沌状态,证明了采用Duffing混沌振子检测微弱周期小信号的可行性.     

弱信号检测的混沌模型及应用􀀁

本文给出了一种典型的间歇混沌模型－－Duffing混沌振子,并详细的分析了其间歇混沌特性,基于混沌现象发生随模型参数变化的间歇性,设计了噪声背景下弱信号的检测方案,最后给出仿真结果。     

基于混沌理论的微弱信号检测方法

分析了间歇混沌模型———Duffing振子的混沌特性,利用Duffing振子的非平衡相变对微小信号具有敏感性及对白噪声和与参考信号频差较大的周期干扰信号具有免疫力的性质,采用混沌振子阵列实现对噪声背景下微弱信号的检测;并采用梅尔尼科夫方法作为混沌判据,该方法的优点在于可以直接进行解析计算。仿真实验表明:该检测方法简单、有效,检测的精度比较高。     

Duffing振子的微弱信号检测

分析了Duffing振子的混沌运动，阐述了该振子相变对志参考信号频差较小的周期小信号具有敏感性，对白噪声和与参考信号频差较大的周期干扰信号具有免疫力，使Duffing振子应用于微弱信号检测具有可行性。检测不同频率的信号需要不同频率ω的参考信号，不同的参考信号频率ω会对系统产生很大影响，通过调整系统参数使得振子对不同频率的信号检测具有普遍性，给出了基于混沌微弱信号检测的具体方案。     

一种新型频率测量方法的研究

研究了一种带摄动的Duffing振子混沌数学模型,详细的分析了其间歇混沌特性.根据Duffing振子对噪声的免疫力,提出了一种新型的频率测量方法,并给出了具体的算法.仿真结果表明,在强噪声背景下,该方法可以准确的测出微弱正弦信号的频率.     

基于混沌振子的BPSK信号解调

基于混沌系统对参数的摄动及其敏感性,分析了混沌系统微弱信号检测的基本原理,推导出混沌系统产生相变的相位条件,结合二进制相移键控(BPSK)信号的相位变化特点,提出了利用duffing系统进行强噪声背景中二进制相移键控(BPSK)信号解调的方法。鉴于观察混沌系统相平面判别系统状态的不足,提出了利用功率谱熵对系统不同状态复杂度进行判别的新方法。理论分析和仿真实验都证明了利用混沌振子解调BPSK信号的可行性。     

混沌振子实现微弱周期小信号的检测

通过对混沌振子Duffing方程及其检测原理的介绍,发现混沌振子对周期小信号具有敏感特性,能够在强噪声环境下实现对微弱周期小信号的检测。Matlab实验仿真和分析证明了采用混沌振子Duffing检测微弱周期小信号的可行性。     

分数阶Duffing振子的动力学研究

在经典Dtfffing振子中引入分数微分型阻尼项,推导了高效率的数值计算格式,对其表现出来的特有的非线性现象进行讨论．研究表明：分数微分型阻尼的分数阶值较小时,振子将出现倍周期分岔并导致混沌．在不同的外激励频率下,分数微分型Duffing振子会呈现对称性破缺、分岔、混沌等强烈的非线性现象;在一定参数范围内,分数微分型Duffing振子较经典Duffing振子,在较小的激励下即可进入混沌．     

Host-Parasitoid系统的分岔与混沌控制

用数值模拟的方法,研究了Host-Parasitoid模型.该模型是一类非线性离散系统,反映了在一定的时间和空间内,寄生虫和寄宿主之间的生存状态.通过调节各种影响下的分岔参数,可以观察到系统具有周期泡,倍周期分叉,间歇混沌和Hopf分岔等复杂非线性动力学现象,揭示了系统通向混沌的途径.利用不同周期遍历下的奇怪吸引子和具有分形边界的吸引盆对系统的非线性特性进行了深入的探讨.最后利用参数开闭环控制法对系统的混沌状态进行了有效的控制.数值仿真和理论分析表明,选择相应的控制参数可将该系统的混沌状态控制到不同的稳定周期运动.     

Analysis of complex intermittency in Boost converter from a bifurcation control viewpoint

Due to undesirable interference via unintended coupling paths, switching converters may exhibit complex intermittency, which appears as a form of bifurcation undergoing regular operation, subharmonics, and chaos orderly and repeatedly for a long period of time. Such intermittent operation, being an unwanted operating state, should normally be avoided in power converters. This paper expounds the mechanism and conditions for the emergence of intermittency in a common current-mode controlled Boost converter. It is found that interference at frequencies near the switching frequency or its rational multiples may induce intermittent operation. The strengths and frequencies of the interfering signals determine the type and period of intermittency. The problem is analyzed by transforming the time-bifurcation analysis to a conventional parameter-bifurcation analysis. Based on this transformation, intermittency can be investigated from the bifurcation control viewpoint. Furthermore, the critical circuit parameter conditions for the emergence of intermittency can be predicted and compared with those from circuit simulation.     

An adaptive data detection algorithm based on intermittent chaos with strong noise background

In order to realize the signal detection under the condition of lower SNR, this paper introduced the adaptive phase length based on the Duffing chaotic system and verified the measured signal at the optimal excitation frequency. The existence of the target signal was judged by observing whether there are two consecutive intermittent chaos in the time domain. Then the envelope of the intermittent chaos was obtained by Hilbert transform. Finally, the exact value of envelope spectrum was obtained by using the one-and-half-dimension spectrum, which can calculate the precise value of the frequency of the signal to be measured. The experimental results showed that the proposed algorithm can achieve a lower SNR than the conventional detection. Compared with the general chaotic detection, this algorithm can realize smart self-adaptation. It is unnecessary to specify different excitation frequencies and chaotic thresholds for different frequencies to be measured. In addition to the existence of the target signal judgment, the algorithm can also achieve accurate calculation of the frequency of the signal to be measured.

     

Control of chaos in SEPIC DC-DC converter

DC-DC converters are widely used in power electronic systems where there is a need for stabilizing a given dc voltage to a desired value. It has been reported that DC-DC converters exhibit different non-linear phenomena including bifurcations, quasi-periodicity and chaos under both voltage mode and current mode control schemes. In this work, current mode controlled SEPIC converter operating in continuous conduction mode is considered and by varying the reference current I_ref, the converter exhibits chaos. It has been observed that the system changes from a stable buck-like operation to an unstable boost-like operation by varying I_ref. Bifurcation diagram is plotted for control signal and capacitor voltage with I_ref as bifurcation parameter. Resonant parametric perturbation control technique has been applied to suppress chaos. Effects of phase shift and frequency mismatch are also analyzed. With phase shift, control power required for suppressing chaos has been reduced. Also intermittent chaotic stages are suppressed with the effect of frequency mismatch at the expense of increasing control power. The stability analysis in SEPIC converter is performed by means of discrete model and is validated through the simulated and experimental results.     

基于相位差原理的无线电源定位方法的研究与仿真

为了确定兵器试验场上弹落点的位置,提出了基于多接收天线的接收信号相位差原理,确定近距离无线电发射源位置的方法,建立了一种5个接收天线的菱形测距模型,推导了距离与相位差的关系,通过测量菱形中心与任一顶点间的相位差,从而得出发射源的距离;为了简化接收天线的布置,优化了长、短对角线。得出了简易的方阵测距模型;本文还对此模型进行了计算机模拟仿真,证明了该方法的可行性。     

噪声对基于Duffing方程弱信号检测的影响研究

针对利用混沌临界状态检测弱信号时存在误判、效率低和误差的问题,建立并分析了Duffing方程的基本形式;阐述了基于混沌信号相平面变化进行弱信号检测的工作原理;研究了混沌临界状态检测法中噪声对检测性能的影响,仿真发现了小信号条件下二维双稳非线性系统的随机共振现象,为提高强噪声背景下检测信号的信噪比奠定了一定的基础,为利用随机共振技术检测弱信号提供了一条新的途径。