基于蔡氏电路的混沌保密通信研究

通过对混沌理论研究,对电路产生混沌信号进行了分析设计。同时基于蔡氏电路构建了混沌保密通信系统,并利用multisim软件进行了仿真实验。仿真结果表明,在发送端与接收端传送一个叠加混沌信号的信息信号可以实现高质量的保密通信。     

变型蔡氏电路的混沌保密通信

为了产生更复杂的混沌系统,使通信更安全可靠,设计了一种产生丰富混沌行为的变型蔡氏电路,并进行了理论分析和计算机仿真.在此基础上根据驱动-响应同步原理设计了混沌保密通信电路,以方波作为输入信号进行了相应的硬件实验研究,给出了通信系统中各元件的参数和各部分的波形.结果表明:电路实验结果与计算机模拟结果完全符合,并且在响应电路和驱动电路的元件参数一致,其相对误差小于1%的条件下,当输入方波信号频率在约8 kHz～9 MHz时,该变型蔡氏电路的混沌保密通信系统可以实现保密通信.     

蔡氏电路的仿真研究

从理论分析和仿真两个角度分别研究非线性电路中的混沌现象。蔡氏电路是一个典型的混沌电路,只要改变其中一个元件的参数,就可产生多种类型混沌现象。在Matlab的平台上编制相关系统和蔡氏电路数学模型的计算机仿真程序,就可实现双蜗卷和单蜗卷状态下的同步。研究结果表明在相同的混沌行为下,仿真实验与理论分析结论十分吻合,能准确地观察到混沌吸引子的行为特征。     

基于虚拟仪器技术的蔡氏混沌信号发生器设计

混沌是由非线性系统产生的.蔡氏电路是一个最典型的三阶自治混沌电路.文中结合蔡氏电路模型,利用美国NI公司的虚拟仪器软件LabVIEW的数学处理功能编写混沌信号生成程序,并由数据采集卡输出混沌信号,具有易实现,参数易调节,高可靠性等优点.     

一类电机系统的混沌分析及电路实现

针对无刷直流电机开环系统等效非线性数学模型,运用混沌分析的方法对其存在的混沌现象进行了理论分析和仿真实验,确定了混沌系统的对称性、平衡点稳定性等相关理论问题,揭示了无刷直流电机系统通往混沌之路,并设计出与混沌数学模型相应的模拟电子电路,由虚拟示波器显示对应的电路运行状态图验证了该理论研究,进一步为无刷直流电机的混沌分析...     

电力系统混沌振荡的自适应补偿控制

提出了电力系统混沌振荡自适应控制的一种方法。电力系统混沌振荡状态和它的微分信号由微分跟随器实时提取,并通过微分跟随器对非线性周期性负荷扰动的影响进行自适应补偿。在此基础上,设计线性状态反馈控制规律,使得电力系统的运动状态保持稳定。计算机仿真验证了该方法的正确性。     

永磁同步电动机混沌系统的状态反馈控制

根据永磁同步电动机数学模型,讨论了常输入电压、常外部转矩条件下永磁同步电动机系统的混沌特性.建立了简单的永磁同步电动机混沌仿真模型,该模型通过加入一个状态反馈控制器,可以消除系统的混沌现象,为永磁同步电动机混沌运动分析或控制打下了研究基础.     

一个超混沌系统的设计与电路实现

为了提高超混沌系统的随机性以产生复杂的超混沌信号用于混沌保密通信,通过在一个统一混沌系统中引入一个状态反馈控制器设计一个超混沌系统.利用理论和数值仿真的方法对系统的基本特性,如平衡点及在平衡点的特征值、分形维数、分岔图、Lyapunov指数等进行分析.为验证该系统,利用系统方法设计一个模拟超混沌电路.该设计方法重新标度时间和坐标变量,将状态方程变换为一个无量纲的标准方程,获得了一个确定电路参数的严格公式.实验中观察到了超混沌、混沌、拟周期、周期等动力行为,实验结果与数值仿真结果完全相符.     

混沌及混沌电路的研究

本文给出了混沌的定义和常用的判定混沌方法 ,然后提出了用频变负电阻 (FDNR)实现混沌振荡器的新电路 ,该电路结构简单 ,仅用一个接地的频变负电阻作为有源器件 ,用二极管提供必要的非线性 ,最后文中给出了PSpice仿真验证了结果。     

混沌保密通信实验电路设计

针对通信的安全可靠问题,探讨了利用混沌进行保密通信的可行性。根据Pecora和Carroll提出的驱动一响应同步方法,分析了蔡氏混沌电路的同步原理,设计了混沌掩盖通信的实验电路,给出了元件参数和波形。实验结果表明：当f≥8kHz时,输入方渡信号被掩盖传输,实现了混沌保密通信。     

Some new algebraic criteria for chaos synchronization of Chua's circuits by linear state error feedback control

The research on the sufficient criterion for chaos synchronization of the master–slave Chua's circuits by linear state error feedback control has received much attention and some synchronization criteria for special control matrix were proposed. In this paper, the above synchronization issue is investigated in the situation of general linear state error feedback controller with propagation delay of control signals from the master Chua's circuit. First of all, a master–slave synchronization scheme for Chua's circuits with propagation delay is given and the relevant error system is derived. Using a quadratic Lyapunov function and frequency domain method, three new algebraic synchronization criteria for the synchronization scheme with general control matrix are proven. They are applied to derive the synchronization criteria for simple control matrices. Some examples are given to show the sharpness of these new criteria compared with the known criteria. Copyright © 2006 John Wiley & Sons, Ltd.     

基于变量反馈的电力系统混沌振荡控制

混沌运动是一种普遍存在的现象，表现了系统内部的复杂性、随机性和无序性。电力系统也存在混沌现象，对系统的稳定运行是有害的。采用变量反馈控制法（VFC）控制互联电力系统由周期性负荷扰动引起的混沌振荡，根据混沌运动对初值敏感依赖性，仅采用单一状态变量反馈就能有效地抑制系统的混沌振荡，使系统从混沌或不稳定状态进入稳定的运动状态。该方法具有良好的稳定性和轨道跟踪能力，不改变被控系统的结构，不需要使用除系统输出或状态变量以外的任何有关被控系统的信息。在仿真分析时比较了反馈控制器投入前后的系统动态行为，得到的结果与理论分析相一致。     

基于状态负反馈的电力系统混沌控制

在某些情况下,电力系统可能出现混沌现象,从而对系统的稳定性产生影响。利用状态负反馈控制,通过选取合适的反馈系数,镇定系统的不稳定周期轨道,达到抑制混沌振荡的目的。仿真实验的结果进一步证明了该方法的有效性,其对于保障电力系统的稳定性具有较好价值。     

Adaptive finite-time output feedback control for Markov jumping nonlinear systems

In this article, the problem of output feedback tracking control for uncertain Markov jumping nonlinear systems is studied. A finite-time control scheme based on command filtered backstepping and adaptive neural network (NN) technique is given. The finite-time command filter solves the problem of differential explosions for virtual control signals, the NN is utilized to approximate the uncertain nonlinear dynamics and the adaptive NN observer is applied to restructure the state of system. The finite-time error compensation mechanism is established to compensate the errors brought by filtering process. The proposed finite-time tracking control algorithm can ensure that the solution of the closed-loop system is practically finite-time stable in mean square. Two simulation examples are employed to demonstrate the effectiveness of the proposed control algorithm.     

时空混沌的自适应模糊控制

对模型不确定的子系统是多维的耦合Henon映射链提出用离散自适应模糊的方法控制混沌,该方法综合了自适应模糊逻辑系统的逼近能力和带有域变结构控制策略的优点。仿真结果证明了所提方法的有效性。     

电力系统混沌振荡的自适应最优控制

电力系统在周期性负荷扰动的作用下会发生混沌振荡,甚至由此而失去稳定。为抑制这种情况下的混沌振荡,保证电力系统运行的稳定性,利用自适应最优控制方法设计了在周期性负荷扰动幅值不确定以及系统参数不确定情况下的混沌振荡控制器;并利用Lyapunov稳定性理论证明了受扰的、未精确建模的电力系统在该控制器作用下可以保持渐近稳定。因此,当电力系统所受到的周期性负荷扰动的幅值不确定且引起电力系统混沌振荡甚至失去稳定时,自适应最优控制器可以使电力系统获得渐近稳定,即能回到初始平衡点上。数值仿真也表明了该控制器的控制效果。     

IFOC感应电动机分岔混沌的单双时滞反馈控制

为了研究间接磁场定向控制感应电动机系统的失稳机理,采用分岔图分析了感应电动机系统的动力学特性以及通往混沌的路径,同时,利用最大李雅普诺夫指数给出了混沌产生的参数区间,从而预测感应电动机系统的不规则振荡行为.混沌现象的产生使得感应电动机系统振荡加剧,为抑制这种不规则振荡现象,在感应电动机系统中加入时滞反馈控制项,利用分岔图分析了时滞反馈控制项对整个感应电动机系统的影响,并从中选取合适的控制参数,使感应电动机系统达到平衡点并进入稳定运行状态,数值仿真分析结果表明加入双时滞反馈项可以使系统过渡过程变短,收敛速度变快,控制效果更优.     

Adaptive robust output‐feedback motion control of hydraulic actuators

Most previous advanced motion control of hydraulic actuators used full‐state feedback control techniques. However, in many cases, only position feedback is available, and thus, there are imperious demands for output‐feedback control for hydraulic systems. This paper firstly transforms a hydraulic model into an output feedback–dependent form. Thus, the K‐filter can be employed, which provides exponentially convergent estimates of the unmeasured states. Furthermore, this observer has an extended filter structure so that online parameter adaptation can be utilized. In addition, it is a well‐known fact that any realistic model of a hydraulic system suffers from significant extent of uncertain nonlinearities and parametric uncertainties. This paper constructs an adaptive robust controller with backstepping techniques, which is able to take into account not only the effect of parameter variations coming from various hydraulic parameters but also the effect of hard‐to‐model nonlinearities such as uncompensated friction forces, modeling errors, and external disturbances. Moreover, estimation errors that come from initial state estimates and uncompensated disturbances are dealt with via certain robust feedback at each step of the adaptive robust backstepping design. After that, a detailed stability analysis for the output‐feedback closed‐loop system is scrupulously checked, which shows that all states are bounded and that the controller achieves a guaranteed transient performance and final tracking accuracy in general and asymptotic output tracking in the presence of parametric uncertainties only. Extensive experimental results are obtained for a hydraulic actuator system and verify the high‐performance nature of the proposed output‐feedback control strategy.     

Adaptive fuzzy output‐feedback tracking control for switched stochastic pure‐feedback nonlinear systems

This paper considers the problem of adaptive fuzzy output‐feedback tracking control for a class of switched stochastic nonlinear systems in pure‐feedback form. Unknown nonlinear functions and unmeasurable states are taken into account. Fuzzy logic systems are used to approximate the unknown nonlinear functions, and a fuzzy observer is designed to estimate the immeasurable states. Based on these methods, an adaptive fuzzy output‐feedback control scheme is developed by combining the backstepping recursive design technique and the common Lyapunov function approach. It is shown that all the signals in the closed‐loop system are semiglobally uniformly ultimately bounded in mean square in the sense of probability, and the observer errors and tracking errors can be regulated to a small neighborhood of the origin by choosing appropriate parameters. Finally, a simulation result is provided to show the effectiveness of the proposed control method.