混沌系统的时间延迟同步误差分析

对Pecora和Carroll的混沌自同步方案的延迟同步误差进行了研究.在计算机上对Lorenz混沌系统伪装的延迟同步误差进行了模拟:给定系统参数,对应不同延迟时间,得出了均方误差与采样步长的关系曲线;给定系统参数和延迟时间,对应不同采样步长,得到了混沌时间序列的误差曲线;给定采样步长,对应不同的系统参数,获得了混沌时间序列的尺度效应和均方误差与采样步长的关系曲线.提出了减小延迟同步误差的一些方法,得到一些对混沌同步和混沌控制应用有意义的结果. 关键词： 混沌同步 时间同步 误差分析     

Chaotic synchronization: a nonlinear predictive filtering approach

The synchronization of chaotic systems is a difficult task due to their sensitive dependence on the initial conditions. Perfect synchronization is almost impossible when noise is present in the system. One of the well known stochastic filtering algorithms that is used to synchronize chaotic systems in the presence of noise is the extended Kalman filter (EKF). However, for highly nonlinear systems, the approximation error introduced by the EKF has been shown to be relatively high. In this paper, a nonlinear predictive filter (NPF) is proposed for synchronizing chaotic systems. In this scheme, it is not required to approximate the underlying nonlinearity and hence there is no need to compute the Jacobian of the chaotic system. Numerical simulations are carried out to compare the performances of the NPF and EKF algorithms for synchronizing different sets of chaotic systems and/or maps. The well known Lorenz and Mackey-Glass systems as well as Ikeda map are used for numerical evaluation of the performance. Results clearly show that the NPF based approach is superior to the EKF based approach in terms of the normalized mean square error (NMSE), total NMSE, and the time taken for synchronization (measured in terms of the normalized instantaneous square error) for all the systems and/or maps considered.     

双光头多层数据存储系统同步聚焦误差检测

为实现共焦双光头多层数据存储系统,需要对双光头同步聚焦误差进行检测,以确定聚焦伺服跟踪精度,验证系统的可行性。首先利用几何光学的ABCD变换矩阵计算双光头输出能量与光头间距离的关系,确定其线性工作范围;其次通过输入不同频率的正弦信号驱动音圈电机,获得静止状态、下光头运动状态以及双光头同步运动状态下,四象限探测器的输出信号;最后对输出信号进行频域分析,可计算得到由于双光头参量失配而导致的同步聚焦误差在不同频率下的幅值。实验结果表明,在20 Hz、峰-峰值0.5 V正弦信号作用下,同步聚焦误差幅值在1μm以下,可以满足共焦双光头多层数据存储系统的聚焦伺服跟踪要求。     

Prediction of chaotic time series based on modified minimax probability machine regression

Long-term prediction of chaotic time series is very difficult,for the Chaos restricts predictability.in this paper a new method is studied to model and predict chaotic time series based on minimax probability machine regression （MPMR）. Since the positive global Lyapunov exponents lead the errors to increase exponentially in modelling the chaotic time series, a weighted term is introduced to compensate a cost function. Using mean square error （MSE） and absolute error （AE） as a criterion, simulation results show that the proposed method is more effective and accurate for multistep prediction. It can identify the system characteristics quite well and provide a new way to make long-term predictions of the chaotic time series.[第一段]     

一种基于强跟踪滤波的混沌保密通信方法

提出了一种基于强跟踪滤波器的混沌保密通信方法. 在发送端, 混沌映射和信息符号被建模成非线性状态空间模型, 信息符号被加性混沌掩盖或乘性混沌掩盖调制, 然后通过信道输出. 在接收端, 驱动信号被接收, 使用带有贝叶斯分类器(信息符号估计)的强跟踪滤波器算法动态地恢复信息符号. Logistic混沌映射的仿真表明, 当信息符号为二进制编码时, 不管是加性混沌掩盖调制还是乘性混沌掩盖调制, 强跟踪滤波器均能较好地从混沌信号中恢复信息符号. 与扩展卡尔曼滤波器相比, 由于卡尔曼滤波器对于离散的信息符号跟踪能力差, 混沌映射中信息符号难以恢复, 比特误码率高. 因此, 这种基于强跟踪滤波器的混沌保密通信方法是有效的.     

Study of dual-directional high rate secure communication systems using chaotic multiple-quantum-well lasers

A scheme of synchronized injection multi-quantum-well (MQW) laser system using optical coupling-feedback is presented for performing chaotic dual-directional secure communication. The performance characterization of chaos masking is investigated theoretically, the equation of synchronization demodulation is deduced and its root is also given. Chaos masking encoding with a rate of 5\,Gbit/s and a modulation frequency of 1\,GHz, chaos modulation with a rate of 0.2\,Gbit/s and a modulation frequency of 0.2\,GHz and chaos shifting key with a rate of 0.2\,Gbit/s are numerically simulated, separately. The ratio of the signal to the absolute synchronous error and the time for achieving synchronous demodulation are analysed in detail. The results illustrate that the system has stronger privacy and good performances so that it can be applied in chaotic dual-directional high rate secure communications.     

Error analysis for polychromatic speckle contrast measurements

Revival of interest in speckle technologies raises a curial question on the accuracy calculation of speckle measurements. In particular, the accuracy calculation of speckle contrast, an important metrics of a stochastic process, is quite different from the accuracy calculation of a typical intensity measurement. Speckle contrast depends more on stochastic characteristics of a process rather than on hardware characteristics. In this article, we consider errors introduced by the limited number of available speckle and by intensity saturation for monochromatic and polychromatic speckles. Equations for these types of errors were derived. Particularly, we show that the error due to limited number of speckles is inversely proportional to the square root of the speckle number, in the similar way as the average intensity error. For the error due to limited dynamic range of a recording device, the truncation effect increases the error as the mean intensity increased. Monochromatic speckles are more sensitive to such truncation than polychromatic speckles. We report the optimal mean intensity in terms of the pixel depth of a recording device and the total number of speckle recorded. In addition, a recommendation to minimize the saturation error for a typical camera is included.     

The adaptive synchronization of fractional-order Liu chaotic system with unknown parameters

In this paper, the chaos control and the synchronization of two fractional-order Liu chaotic systems with unknown parameters are studied. According to the Lyapunov stabilization theory and the adaptive control theorem, the adaptive control rule is obtained for the described error dynamic stabilization. Using the adaptive rule and a proper Lyapunov candidate function, the unknown coefficients of the system are estimated and the stabilization of the synchronizer system is demonstrated. Finally, the numerical simulation illustrates the efficiency of the proposed method in synchronizing two chaotic systems.     

高速多量子阱激光器混沌保密通信系统研究

研究了外部光注入高速多量子阱激光器激光混沌全光保密通信系统,导出系统同步方程,理论证明并数值实现了系统的同步,分析了增加反馈系数以缩短同步时间且增强系统同步稳定性的方法。研究分析了多量子阱激光器混沌隐藏和混沌键控保密通信全光调制解调系统模型,数值模拟了具有正弦调制信号的调制频率0．2GHz混沌模拟保密通信和数字信号调制速率20Gb／s的混沌数字保密通信以及调制速率0．05Gb／s混沌键控保密通信的应用,系统确实具有较高的保密性能和反破译能力;分析了混沌数字信号保密通信调制带宽20Gb／s调制解调时的同步误差以及混沌键控调制速率,系统都具有非常好的调制解调特性,且在高速混沌通信中,系统解调具有相对较小的同步误差,而1Gb／s是混沌键控通信的速率上限。     

不确定自催化反应扩散时空混沌系统的延时同步

设计了一种延迟同步控制器实现了时空混沌系统之间的同步控制.基于Lyapunov稳定性定理,确定了延迟同步控制器的结构以及系统状态变量之间的误差方程.以自催化反应扩散时空混沌系统为例,仿真模拟验证了该控制器的有效性.进一步设计了参量辨识器,对不确定自催化反应扩散时空混沌系统中的参量进行了有效辨识.通过研究有界噪声影响下系统的同步效果,表明该同步方法具有较好的抗干扰能力. 关键词： 时空混沌 延时同步 参量辨识 有界噪声     

分数阶Genesio-Tesi系统的混沌动态和同步

本文首先通过数值仿真研究了分数阶Genesio-Tesi系统的混沌动态。发现阶数小于3的分数阶Genesio-Tesi系统存在混沌行为和该分数阶系统存在混沌的最小阶是2.4。然后提出了一种通过标量驱动信号同步分数阶混沌Genesio-Tesi系统的驱动响应同步方法。基于分数阶系统的稳定理论，该同步方法是简单的和理论上严格的。它不需要计算条件Lyapunov指数。仿真结果说明了所提同步方法的有效性。     

Gyrator transform-based optical image encryption,using chaos

We propose a new method for image encryption, using gyrator transform and chaos theory. Random phase masks are generated using chaos functions and are called as chaotic random phase masks. In the proposed technique, the image is encrypted using gyrator transform and two chaotic random phase masks. Three types of chaos functions have been used to generate the chaotic random phase masks. These chaos functions are the logistic map, the tent map and the Kaplan-Yorke map. The computer simulations are presented to verify the validity of the proposed technique. The mean square errors have been calculated. The robustness of the proposed technique to blind decryption in terms of rotation angle and the seed values of the chaotic random phase mask have been evaluated. The optical implementation of the encryption and the decryption technique has been proposed.     

闪电瞬态电场信号波形去噪方法

 通过对传统数字滤波和Birge-Massart小波阈值法的比较，对闪电瞬态电场信号进行了去噪研究。构建了双指数衰减脉冲信号并在其上叠加了高斯白噪声信号来仿真闪电瞬态电场实测波形，通过计算去噪前后信号的均方误差和幅值误差，比较了加权平滑滤波、FIR数字低通滤波器和小波阈值法的去噪效果，从处理仿真波形和实测波形结果可以发现，小波阈值去噪方法明显优于另外两种传统滤波方法。通过比较仿真信号由不同小波分解层数去噪结果的均方误差和幅值误差，确定在对闪电电场实测信号的去噪过程中，小波系数分解层数应选5~7。     

一种改进的弹丸落点声学定位方法

研究了基于传感器阵列的声源定位技术,并在此基础上提出了一种改进的最小二乘声源定位方法。首先,根据风速、风向、温度对声速的影响,建立了观测值修正模型,再根据误差传播特性合理分配权阵,然后用最小二乘法进行定位解算;考虑观测值中可能含有粗差,将IGG3抗差模型加入到数据处理中,以提高系统的抗干扰能力;另外,通过观察残差向量,判断可能出现时序错误的观测值,再对时序不断调整,解决多声源时序混乱的问题。最后,通过对试验数据解算分析,证明本文方法的有效性和可行性。试验结果表明:改进的最小二乘声源定位方法可使定位误差达到4 m以下。本文所提方法不仅能有效降低粗差的影响,而且可准确处理多声源定位中观测值时序关系混乱的问题,可靠性较高。本文的研究内容紧密联系实际,可为声源定位设备的设计和应用提供参考依据。      

非线性光电延时反馈混沌同步复用通信系统研究

提出了一种基于电光调制器的非线性光电延时反馈超混沌复用通信系统.与传统混沌通信系统不同,其混沌波形不是由激光器产生,而是由电光调制器产生,该系统具有非线性维数高、易于再生和精确控制的优势.介绍了信号调制反馈延时的编码方法和相关检测解码方法,数值仿真了三条支路的高速复用与解复用,分析了误码产生的主要原因,并进一步研究了光...     

基于广义窗函数和最小二乘支持向量机的混沌背景下微弱信号检测

为了从混沌背景中检测微弱信号,研究分析了复杂非线性系统的相空间重构理论,提出了一种基于广义窗函数的最小二乘支持向量机的预测法. 该方法以广义嵌入窗为基础,利用自关联函数法确定Lorenz系统的嵌入维数和时间延迟, 实现相空间重构,结合最小二乘支持向量机建立Lorenz系统的误差预测模型, 检测微弱目标信号(瞬态和周期信号).仿真实验表明,该方法的预测模型具有较小的误差, 能够有效地从混沌背景噪声中检测出微弱目标信号,减小噪声对目标信号的影响. 与传统方法相比,在降低检测门限的同时,能够有效地提高预测的精度, 在混沌噪声下信噪比为-87.41 dB的情况下,相对于传统支持向量机方法所得的均方根误差0.049(-54.60 dB时)降低近两个数量级至0.000036123(-87.41 dB时).     

混沌噪声背景下微弱脉冲信号的检测及恢复

构建了一种在混沌噪声背景下检测并恢复微弱脉冲信号的模型.首先,基于混沌信号的短期可预测性及其对微小扰动的敏感性,对观测信号进行相空间重构、建立局域线性自回归模型进行单步预测,得到预测误差,并利用假设检验方法从预测误差中检测观测信号中是否含有微弱脉冲信号.然后,对微弱脉冲信号建立单点跳跃模型,并融合局域线性自回归模型,构成双局域线性(DLL)模型,以极小化DLL模型的均方预测误差为目标进行优化,采用向后拟合算法估计模型的参数,并最终恢复出混沌噪声背景下的微弱脉冲信号.仿真实验结果表明本文所建的模型能够有效地检测并恢复出混沌噪声背景中的微弱脉冲信号.     

Open-loop frequency response for a chaotic masking system

In this paper, a new numerical simulation approach is proposed for the study of open-loop frequency response of a chaotic masking system. Using Chua's circuit and the Lorenz system as illustrative examples, we have shown that one can employ chaos synchronization to separate the feedback network from a chaotic masking system, and then use numerical simulation to obtain the open-loop synchronization response, the phase response, and the amplitude response of a chaotic masking system. Based on the analysis of the frequency response, we have also proved that changing the amplitude of the exciting (input) signal within normal working domain does not influence the frequency response of the chaotic masking system. The new numerical simulation method developed in this paper can be extended to consider the open-loop frequency response of other systems described by differential or difference equations.     

混沌海杂波背景下的微弱信号检测混合算法

基于经验模态分解理论, 提出了一种基于粒子群算法的支持向量机预测方法. 采用总体平均经验模式分解法将混沌信号分解为若干固有模态函数和趋势分量, 将复杂的非线性信号转化为具有不同尺度特征的平稳分量. 利用粒子群算法对支持向量机的惩罚系数和核函数进行优化, 结合支持向量机建立混沌序列的单步预测模型. 从预测误差中检测淹没在混沌背景中的微弱信号(包括瞬态信号和周期信号). 对Lorenz系统和实测IPIX雷达数据进行仿真实验, 结果表明, 该方法能够有效地从混沌背景噪声中检测出微弱目标信号, Lorenz系统得到的均方根误差0.000000339 (-102.8225 dB时)比传统支持向量机方法的均方根误差0.049 (-54.60 dB时)降低了5个数量级, 从海杂波中检测出具有谐波特性的微弱信号, 表明预测模型具有更低的门限和误差.     

Entanglement Dynamics and Chaos in the Dicke Model

We study dynamical properties of quantum entanglement in the Dicke model with and without the rotating-wave approximation. Specifically, we investigate the maximal entanglement and mean entanglement which reflect the underlying chaos in the system, and a good classical-quantum correspondence is found. We also show that the maximal linear entropy can be more sensitive to chaos than the mean linear entropy.