浅析四阶变型蔡氏电路混沌同步保密通信系统

为了增加混沌行为的复杂性,提高混沌保密通信系统的保密性,在三阶蔡氏电路的基础上,我们采用更为复杂的四阶变型蔡氏电路,该电路具有两个正的李雅普诺夫指数,是超混沌系统,与一般的混沌系统比较,具有更为复杂的动力学行为,具有更强的随机性和不可预测性,更适合应用到保密通信和信息安全领域中,下面就简单介绍一下四阶变型蔡氏电路混沌同步保密通信系统。     

探讨基于混沌理论的通信保密方案

文章基于密码学理论和混沌同步理论,结合混沌序列密码加密、信息置乱、信息隐藏等技术,提出了一个比较安全的通信保密系统的设计方案。该系统具有安全性好、易于使用、速度快等特点。     

解析无刷直流电机的工作原理

近几十年来,随着永磁材料,微电子技术,自动控制技术,电力电子技术,大功率半导体器件的快速发展,无刷直流电机得到迅速发展。并且无刷直流电机由于其自身优点,在当今国民经济各个领域,如医疗器械、化工、及计算机驱动器以及家用电器等方面得到了广泛的应用。直流电机的结构历来是电枢为转子,磁铁作为定子。若仍旧保持这种结构;则要实现无刷直流电机是非常困难的。目前的无刷直流电机的机械结构为：电枢绕组作为定子一部分,转子则是作为磁场的永磁铁,这与称为永磁同步交流电机非常相似。     

输出控制的混沌同步保密通信系统设计和应用

随着信息化时代的不断推进,我国计算机等信息技术也日益完善,特别是对于通信技术而言,可以通过网络、计算机等多个途径进行实现。而对于通信过程来说,传统的通信系统更加追求通信的质量以及效果,而对于目前时期来说,通信信息的保密性也越来越重要。对于通信系统来说,混沌运动具有其独特且多样的轨迹,而且具备非周期及不间断宽带频谱的特性。因而对于通信系统的保密功能具有很大的参考价值,而研究输出控制的混沌同步保密通信系统设计和应用,将为我国通信技术发展带来重要的参考。     

一种新型无刷直流电机驱动板的设计

无刷直流电机在精密传动和大功率驱动系统中应用广泛。但现有无刷直流电机驱动板功能单一,限制了无刷直流电机的研究与发展。本文根据无刷直流电机的驱动和回馈制动工作特点,设计了一种新型无刷直流电机驱动板。其具有回馈过压闭锁保护电路和高精度电流检测电路,适用于大功率驱动及回馈制动等控制需求。     

数字伺服节能控制器的设计与应用

提出了一种无刷直流电机控制器的设计方案,以工业缝纫机为应用背景,设计了基于Microchip的dspic33fj32mc204单片机的控制器软硬件.系统采用PI调节实现了无刷直流电机的无级控制,对控制器用于工业缝纫机进行实测,节能效果显著,动静态指标符合实际使用要求,具有良好的实用价值.     

基于PIC单片机的无刷直流电机控制系统

基于PIC单片机的无刷直流电机控制系统的出现,可以让人们对无刷直流电机控制系统的要求得到满足。无刷直流电机可以在延长电机定期维护修理时间的基础上,促进电机使用效率的提升。本文主要从无刷直流电机控制系统方案入手,对无刷直流电机控制系统的硬件设计和软件设计等问题进行了探究。     

混沌的控制与同步

本文论述了目前常见的几种混沌的控制方法及同步方法;阐明了超混沌与混沌的主要区别;明确提出超混沌比混沌更适用于保密通信的观点。     

浅谈混沌通信

本文介绍了基于混沌理论的通信技术,包括混沌掩盖技术、混沌码分多址技术及混沌扩频技术、混沌通信系统中的同步的发展现状等等。     

超短波无线通信保密技术的应用分析

本文讨论GOLD序列等不同跳频序列的性能,基于队列理论,通过增大跳频序列线性复杂度,提出了混合混沌映射跳频序列方法,仿真证明该方法可增加系统的抗预测能力,且跳频序列的平衡性等性能良好,容易实现,适用于超短波通信系统,基于对无线信道分析,利用训练系列判决反馈均衡快速信道估算方法,运用混沌序列实现保密通信功能。串联结构的混沌扩频序列容易实现,保密性能优异。     

Design of adaptive sliding mode tracking controllers for chaotic synchronization and application to secure communications

Synchronization of two identical chaotic systems with matched and mismatched perturbations by utilizing adaptive sliding mode control (ASMC) technique is presented in this paper. The sliding surface function is specially designed based on the Lyapunov stability theorem and linear matrix inequality (LMI) optimization technique. The designed tracking controller can not only suppress the mismatched perturbations when the controlled dynamics (master–slave) are in the sliding mode, but also drive the trajectories of synchronization errors into a small bounded region whose size can be adjusted through the designed parameters. Adaptive mechanisms are employed in the proposed control scheme for adapting the unknown upper bounds of the perturbations, and the stability of overall controlled synchronization systems is guaranteed. The comparison of the proposed chaotic synchronization technique with an existing generalized chaotic synchronization (GCS) method as well as application of the proposed control method to secure communications is also demonstrated in this paper.     

基于标识的新型智能光网络密钥分配协议研究

基于ECC体制的身份认证和智能光网络节点的身份标识,在密钥协商过程中同步实现通信双方的认证和通信密钥的建立,提出了一种改进的基于标识的密钥分配方案。该方案提供了双重保护,有效地防止了攻击者冒充正在通信的节点进行通信,通信双方可进行相互认证,实现了在公开信道上的安全通信。     

Chaos and control of discrete dynamic traffic model

This study discusses chaotic traffic flow. The discrete dynamic model proposed herein is derived from both the flow-density-speed fundamental diagram and Greenshield's model. The model employs occupancy as its variable and the ratio of free flow and average speed as its control parameter. The function form of the model is equal to logistic map that bifurcates when the value of the control parameter increases. Chaotic traffic means that traffic becomes unstable and unpredictable, which is dangerous for driving. Therefore, this study considers the implementation of chaotic control in signal or ramp metering design so as to stabilize the chaotic traffic phenomena. These results are illustrated by numerical examples.     

Synthesizing antipodal chaotic waveforms

Chaotic waveforms are natural information carriers since a correspondence can be established between the symbolic dynamics of a chaotic oscillator and the symbols of a message. Message symbols can be efficiently encoded in a chaotic waveform by applying vanishingly small perturbations to an oscillator to guide its symbolic dynamics to follow a desired course. Recently, two chaotic hybrid dynamical systems were shown to have matched filters enabling robust reception of chaotic communication waveforms in the presence of noise. The first of these, the exact shift oscillator, produces waveforms with desirable properties similar to antipodal signaling, but a physical implementation may be difficult to control using small perturbations. The second oscillator, the exact folded-band oscillator, produces less optimal waveforms but is more easily controlled. Here we introduce a method for generating waveforms of the exact shift oscillator by summing waveforms from a bank of easily controlled exact folded-band oscillators. We show that any solution of the exact shift oscillator can be so constructed using only three folded-band oscillators. Thus, this scheme allows us to realize the advantages of both chaotic systems while overcoming their individual disadvantages, thereby enabling practical chaos communications.     

Observer design for constrained nonlinear systems with application to secure communication

In this paper, a constrained regularized least square (RLS) state estimator is developed for deterministic discrete-time nonlinear dynamical systems subject to a set of equality and/or inequality constraints. The stability of the estimation error is rigorously analyzed. The proposed estimator is then used to handle the important problem of secure communication. At the transmitting end, the output of the constrained unified chaotic system is used as a chaotic mask to achieve a satisfactory and typical secure communication scheme. The encrypted data signal is injected into the transmitter and simultaneously transmitted to the receiver through a public channel. At the receiving end, the constrained RLS estimator is used to reconstruct the states of the constrained unified chaotic system. Simulation results are presented to show the impact of the imposed constraints on the waveform and the pattern of the generated chaotic signal as well as the ability of the proposed estimator to synchronize the actual and estimated states of the constrained unified chaotic system. Moreover, the proposed estimator is applied to recover discrete signals such as digital images where computer simulation results are provided to show the effectiveness of the proposed estimation scheme.     

Adaptive single input sliding mode control for hybrid-synchronization of uncertain hyperchaotic Lu systems

This paper addresses the problem of hybrid synchronization for hyperchaotic Lu systems without and with uncertain parameters via a single input sliding mode controller (SMC). Based on the SMC approach, the proposed controller not only minimizes the influence of uncertainty but also enhances the robustness of the system. The uncertain parameters are estimated by using new adaptation laws which ensure the uncertain parameters convergence to their original value. A hybrid synchronization scheme is useful to maintain the vastly secured and secrecy in the area of secure communication by using the control theory approach. The proposed hybrid synchronization results are providing a superiority of forming a chaotic secure communication scheme. Finally, a numerical example is provided to demonstrate the validity of the theoretical analysis.     

A new approach for constrained chaos synchronization with application to secure data communication

In this paper, a new technique is introduced for chaos secure data communication. In this approach, in addition to the usually used techniques for data encryption, the concept of carrier encryption is introduced to increase the security level of the secure communication scheme. To fulfill this objective, at the transmitting end, two chaotic oscillators are coupled, and a set of inequality time dependent constraints with time dependent bounds is imposed on the generated chaotic signals. Moreover, to increase system complexity and its security level, the imposed set of constraints and their bounds are allowed to be changeable from one time period to another during the transmission process. As a result, the patterns of the generated chaotic signals are completely changed and the chaotic oscillator is completely encrypted. At the receiving end, the newly developed Constrained Smoothed Regularized Least Square (CSRLS) observer is used to synchronize the received constrained chaotic signals and hence retrieve the transmitted data. Using such an approach, the quality of the received information, measured by the Bit Error Rate (BER), is highly improved due to the superior performance of the developed CSRLS observer. The stability of the observer is analyzed, and simulation results are presented to show the efficiency and effectiveness of the proposed secure communication scheme.     

Secure chaotic communication based on extreme multistability

Extreme multistability is the coexistence of a large number of attractors which can be reached by varying initial conditions. In this paper we show how this fascinating phenomenon can be used for secure communication. The main advantage of the communication system based on extreme multistability over a conventional chaos-based communication system is its exceptionally high security. The proposed system consists of two identical six-order oscillators; one in the transmitter and another one in the receiver, each exhibiting the coexistence of a large number of chaotic attractors. The oscillators are synchronized using a private channel through one of the system variables, while the information is transmitted via a public channel through another variable. The information is encrypted by varying the initial condition of one of the state variables in the transmitter using a chaotic map, adhering message packages in a staggered form to the coexisting attractors within the same time series of another state variable, which leads to switching among the coexisting chaotic attractors. To ensure communication security, the duration of the packages is shorter than synchronization time, so that synchronization attacks are ineffective.     

Chaotic synchronization based on neural filter

Because of the high sensitivity of chaotic systems to their initial conditions, synchronization of chaotic systems with uncertain parameters has been a challenging problem especially in noisy environment. Since synchronization of the transmitter and receiver systems involves recursive estimation, recursive nonlinear filters are called for and the extended Kalman (EKF) filter and unscented Kalman (UKF) filter have been applied. However, such suboptimal filters incur high synchronization errors and provide no capacity for uncertain environment, which motivated the use of the neural filter for chaotic synchronization in this paper. The neural filter, which is a recurrent neural network, can approximate the minimum-variance to any degree. Furthermore, the neural filter can adapt to a uncertain environment without online filter weight adjustment, which is computationally efficient. Numerical experiments show that the chaotic synchronization scheme based on the neural filter outperforms those based on EKF and UKF by a large margin.     

Electronic circuit implementation of the chaotic Rulkov neuron model

Numerical integration is the most common and straightforward approach in computational neuroscience for the study of biological neuron models based on ordinary differential equations. For some purposes, numerical simulations are not enough due to the multiple bottlenecks in computer architectures. However, when electronic circuits are used to simulate in real time large arrays of coupled neurons, the simulations are much faster than the computer simulations. We present here an electronic implementation of a map-based neuron model, a chaotic Rulkov neuron model, that can be easily transferred on a large scale integration circuit and thus provide a framework for the simulation of large networks of neurons. The Rulkov model is a map-based neuron model that has a surprising abundance of features, such as periodic and chaotic spiking and bursting. The discrete time dynamics allows to tune the time scale of the circuit to the needs of the specific application. Since the circuit described here only uses 18 MOS transistors, it offers new perspectives for building large networks of neurons in a single device. This is very relevant for the analysis of large networks of coupled neurons in order to investigate its dynamics over the network and its synchronization properties.