不同一维混沌映射的优化性能比较研究*

选择Logistic、Tent、ICMIC、Bernouilli shift、Chebyshev和Sine映射进行分析,比较不同一维混沌映射在解决非线性优化问题时的混沌搜索效果。使用了四种二维函数测试六种映射的全局寻优能力、收敛速度和解的精度,仿真比较了它们的优化性能,得出六种映射在收敛速度和解的精度方面的性能比较结论。     

混沌序列在DS-CDMA中的应用研究

相对于伪随机序列(PN)码,混沌序列码具有较好的自相关和互相关性能,它有望替代PN码在直序扩谱码分多址(DS-CDMA)通讯系统中得到应用,以提高通讯系统的容量及性能。该文通过介绍IS-95CDMA的标准,说明了混沌数字CDMA的兑现原理,并以蔡氏混沌电路为例,分析了混沌序列信号的随机性和相关性及其电路的同步功能。最后,通过计算机数值仿真来进一步验证混沌随机序列在DS-CDMA系统中应用的可能性。     

级联混沌系统Lyapunov指数研究

在现有变参级联混沌通信系统中,系统密钥出现短周期态会导致密钥泄漏。针对该问题,分析级联混沌系统中Lyapunov指数随级联子系统参量变化的分布情况以及实时加解密系统的安全性,指出即使各独立子系统的Lyapunov指数均为正,其级联系统的Lyapunov指数也可能为负,负Lyapunov指数将导致密钥泄漏。为此,设计一个短程相关性线程对系统密钥进行实时监测,防止短周期态的发生,从而较好解决密钥泄漏问题。     

一个新超混沌系统的混沌控制比较研究

通过分析研究四维混沌吸引子数学模型的特征,构造了一个新超混沌动力系统.通过对其复杂混沌动力学特征进行分析,表明该四维动力系统含有超混沌吸引子.分别用线性反馈控制、自适应控制方法对该新超混沌系统进行控制,利用Matlab仿真实现了一个新超混沌系统的混沌控制.结果表明,利用线性反馈控制和自适应控制都可以很好地消除混沌,使方程达到一个稳定的状态.     

基于混沌算法信息安全系统的研究

随着网络技术、信息技术的快速发展,信息安全越来越受到人们的关注,在众多信息加密方法中,混沌算法具有良好的伪随机性、敏感性、历遍性等应用性。文章设计基于混沌算法的信息安全系统,该系统利用分段线性混沌映射、k阶Chebychev映射和Logistic映射进行复合实现信息安全传输过程中的一次一密。     

三维复合混沌系统及其在图像加密的应用

混沌是非线性学的一个重要学科,在信息安全、物理学和经济学等领域得到了广泛应用,持续构造新的混沌系统是有意义的。针对这一情况,构造了一类包含迭代次数t的三维三角函数复合混沌系统,对系统的动力学行为进行测试和分析,通过对系统分岔图、Lyapunov指数、周期点导数、谱熵等进行分析,确定其具有较强的混沌特性和较大的混沌区间,同时证明了混沌系统满足Devaney混沌定义,通过对系统随机生成的混沌序列进行0-1测试和NIST测试确定其混沌序列质量良好。因此基于该系统的混沌序列对图像进行加密,实现简单,加密速度快,同时对加密结果的各项指标系数进行了计算和分析,测试结果均非常接近理论最优值。其中,密钥空间很大,可达10252。与最近的其他方法进行对比,结果表明,基于该系统的加密方案可以具有较强的安全性和可靠性。     

超混沌系统自周期轨道链接式控制

基于混沌同步和周期轨道理论提出一种超混沌系统自周期轨道链接式控制法。从超混沌系统状态变量的时间序列中提取周期轨道并用于对系统的实时控制,可使混沌系统稳定运行于某一周期轨道。将提周期轨道经链接组合后用于系统控制,可得到大量的大周期轨道。对4阶蔡氏电路进行数字仿真实验,获得了满意的结果。     

混沌系统的一种自学习模糊控制

提出一种基于遗传算法的自学习模糊控制方法控制混沌系统。用一种改进的遗传算法学习模糊控制器的隶属度函数，以改善模糊控制器的性能，使其达到良好的控制效果。用此方法控制Ｈｅｎｏｎ系统的混沌行为，效果良好。     

连续混沌系统的混沌同步控制

给出了一种实现混沌系统混沌同步的控制方法．通过引入一待定的控制项,将两系统的混沌同步问题转化为讨论与其对应的线性系统的0解渐近稳定性问题,然后根据线性系统控制理论确定此控制项,以实现两混沌系统的同步目的．该方法简单易行,可有效的实现两个混沌系统的混沌同步,且其同步是全局渐近稳定的．     

基于多涡卷混沌系统的数字保密通信方案

为增强传统的混沌保密通信系统抗干扰能力和提高其保密性,提出了一种基于多涡卷混沌系统同步的数字保密通信方案.在该加密方案中,利用多涡卷混沌系统的特点来构造流密码.数值模拟结果表明:该保密通信系统具有很高的抗差函数攻击能力,在同步信号被干扰时,保密通信系统具有一定的抗误码率.     

Performance comparison of some discrete service time systems

This paper analyzes and compares the slotted time operation and the non-slotted time operation of a singleserver system with deterministic service time. These two operations are commonly used to model discrete service time systems in computer or digital communications. But due to the similarity in their operations and performance, the two models may be mixed up with each other. This paper examines by means of queueing analysis the performance of a few classes of systems that differ in the service order of their customers. The means and variances of the queue lengths, waiting times and interdeparture times of FCFS systems using the slotted time operations are first obtained from their respective LST and generating function equations. These are then used for comparison with those in non-slotted time systems. The results show that although the slotted time operation in the FCFS systems can be approximated by the non-slotted time operations under heavy traffic condition, the performances under other regions and service disciplines (e.g., the LCFS and the priority systems) may deviate significantly. They must be properly adjusted if one wishes to use the simpler equations of the non-slotted time operations to approximate the slotted time operations. The comparison graphs provided in this paper supply adjustments guidelines for the careful designers.     

用Matlab仿真非线性混沌振动的主动隔振研究

应用主动隔振原理对Duffing非线性振子设计了参数自调节的PID控制算法，并用Matlab对Duffing振子混沌振动进行主动隔振数值仿真实验，实现了对混沌振动的良好隔振，仿真结果表明，在混沌振动中应用主动隔振技术是有效的。     

Controlling chaotic dynamical systems

We review the major ideas involved in the control of chaos. We present the Ott-Grebogi-Yorke (OGY) method of controlling chaos, which is a particular case of the pole placement technique, but which is the one leading to the shortest time to achieve the control of chaotic systems. Implementation using only measured time series in experimental settings is also described.     

Feedback control of chaotic systems

A suboptimal feedback controller implemented by a multilayer feed-forward neural network is presented to control the unpredictable behavior of chaotic systems. The controller has been tested on the Lorenz and the Rössler systems using numerical simulation. Results show that chaotic systems, subject to feedback control, can be tamed to behave like a system having point attractors with associated basins of attraction.     

非光滑系统的混沌同步

通过广义哈密顿系统和观测器法，本文将非光滑混沌系统的同步问题转化成了研究光滑系统零解的稳定性，从而给出了混沌同步的条件．对具体的带于摩擦，碰撞的Duffing振子分别进行研究，使其达到了完全同步，表明该方法的正确性．     

On feedback-controlled synchronization of chaotic systems

This paper studies a general setting of chaos synchronization in the form of a generalized Lur’e system, which includes both the classical and an earlier version of generalized Lur’e systems as special cases. More significantly, for this general setting, some fairly simple and easily used algebraic conditions are derived for verification and design of unidirectional feedback-controlled chaos synchronization. The Chen and Rössler systems are used as examples for illustration.     

Synchronisation control of composite chaotic systems

Synchronisation conditions are studied for composite chaotic systems with complex compound structure and the signum function based on the theorem of zero-solution stability for a class of linear time-varying systems with countable discontinuous points. The synchronisation controller and its gain range are deduced according to the stability theorem, where the gain of the controller can speed synchronisation. Numerical simulation further proves the control theory and the validity of the synchronisation controller. The proposed controller can be widely applied in those chaotic systems with switch functions or other hybrid chaotic systems.     

Reliable synchronization of nonlinear chaotic systems

This article addresses the reliable synchronization problem for a general class of chaotic systems. By combining the Lyapunov stability theory with the linear matrix inequality (LMI) optimization technique, a reliable feedback controller is established to guarantee synchronization between the master and slave chaotic systems even though some control component (actuator) failures occur. Finally, an illustrative example is provided to demonstrate the effectiveness of the results developed in this paper.     

Digital secure communication via chaotic systems

This paper presents a novel secure communication system for digital signal transmissions. It contains four important parts: modulation, chaotic transmitter, chaotic receiver, and demodulation. The modulation mechanism is to modulate each of delivered bit information to be a carrier signal in the continuous form. Then this carrier signal is taken as a parameter of the chaotic system, called the unified chaotic system. Such a system possesses three different types of chaos characterizations depending on its system's parameter, and this guarantees the communication security more. In the public channel, only three chaotic state variables are delivered and this means that the important carrier information is efficiently screened. According to chaotic states received in the receiver terminal, the continuous carrier signal is decrypted using certain adaptation mechanisms. Finally, the proposed demodulation method can successfully recover the original bit information which is embedded in the communication systems. Some simulation results are provided to verify the efficiency of the proposed secure communication system.