异结构不确定时变时滞复杂网络的外同步

本文研究了具有时间延迟的异结构不确定网络之间的外同步问题.基于Lyapunov稳定性理论,采用双向耦合自适应方法实现了两个结构互异的复杂网络之间的外同步.并且,网络的拓扑结构以及耦合强度也被同时确定.在数值模拟中,选取Van der Pol系统和Duffing系统作为网络节点进行仿真模拟,验证其理论结果的有效性.     

伪卫星定位系统双向时间同步技术

在外部定位系统(如GPS、Loran-C等)受限的条件下,平流层伪卫星定位系统可以为用户提供定位和授时信息,其中时间同步技术是制约系统授时及定位精度的关键因素之一.为了提高伪卫星时间同步的精度,引入了非等应答对称双边双向时间同步技术(SDS-TWR-URT),解决了常用的微波双向时间同步技术(TWR)中因忽略应答时间差异导致的同步精度低的问题.仿真结果表明与常用的TWR技术相比,SDS-TWR-URT算法同步精度提高了45%.最后给出了提高时间同步精度的一些建议.     

超混沌Lü系统的线性与非线性耦合同步

针对由Aiminchen等人最近提出来的一个新的超混沌系统—超混沌Lü系统的同步问题展开研究.对两个恒同的超混沌Lü系统,分别给出了它们在线性耦合和非线性耦合情形下在全局范围内实现同步的充分条件,用Lyapunov方法从理论上证明了结论,并用数值仿真验证了理论结果.     

不确定离散系统具有H∞性能界的鲁棒LQG状态反馈控制

研究了含有范数有界参数不确定线性离散系统具有H∞性能界的鲁棒LQG状态反馈控制问题,考虑了有限时域时变及无限时域时不变两种情形.所得的控制器对于所有可容许的参数不确定都能满足给定的H∞性能界,且为最坏情形H∞性能指标提供了一个最优上界.对于无限时域时不变情形,该控制器还能保证闭环系统渐近稳定.结果仅需求解一含有一个尺度参数的Riccati方程.     

不确定离散系统的神经网络自适应控制方法研究

本文研究了不确定离散系统的神经网络自适应控制器的设计。因为它不需要假设系统状态是可测的,一个观测器用来估计不可测状态。与现有离散系统的结果相比,该控制器具有较少的直接自适应参数。因此,可以很方便地实现工程算法。利用Lyapunov分析方法,所有的闭环系统的信号是保证最终有界（UUB）,并且能够实现系统输出跟踪参考信号到有界紧集。一个仿真例子,验证了该方法的有效性。     

超混沌Lu系统的线性与非线性耦合同步

针对由Aimin chen等人最近提出来的一个新的超混沌系统一超混沌Lu系统的同步问题展开研究．对两个恒同的超混沌Lu系统，分别给出了它们在线性耦合和非线性耦合情形下在全局范围内实现同步的充分条件，用Lyapunov方法从理论上证明了结论，并用数值仿真验证了理论结果．     

连续时延耦合系统的混沌同步及其在保密通信中的应用

研究了具有连续时延双神经元系统的双向耦合混沌同步问题及在扩展频谱保密通信中的应用。利用Krasovskii-Lyapunov理论,给出了系统同步的一个充分条件,通过选择合适的耦合参数可以保证全局混沌同步。给出了使用混沌掩码技术在扩展频谱保密通信中的应用实例。     

基于syncML的移动数据库双向事务级同步

同步复制技术可以保证移动数据库的一致性,是移动数据库的关键技术之一。本文针对移动数据库的断接性、资源有限性等特点,分析同步复制技术现状,将开放的syncML协议同步协议引入数据库,在分析syncML同步协议组成和特点基础上,研究适用于移动数据库的双向事务级同步过程,克服目前移动数据系统同步处理算法中所存在的缺陷,有效保证移动数据库一致性,提高移动数据库的通用性和适应性;同时实现不同结构数据库间的数据同步,增强系统可扩充性。     

一种适用无人机集群的多段补偿时间同步算法

随着人工智能、传感器以及通信技术的快速发展,无人机集群已经逐渐成为现代军事战争中一个不可或缺的作战因素.为了适应无人机集群网络拓扑内的高动态变化,提高组网节点的时间同步精度,提出一种适用于无人机集群的多段补偿双向时间同步算法.算法基于节点间的双向时间信息交互,同时考虑了时钟偏移率与偏移量对同步的影响,并通过均值滤波和指数平滑法来校正时钟偏移.仿真结果表明,与传统的双向同步算法相比,提出的时间同步算法同步精度更高、同步保持更长,更适用于复杂多变的无人机集群网络的时间同步.     

基于线性反馈控制器的时变时滞动态网络中的同步

主要研究具有时变时滞的动态复杂网络中的同步问题. 考虑两种时变时滞的情况—时滞连续一致有界和时滞可微且导数一致有界. 这里假设耦合结构矩阵非对称并且可约. 提出一些新的时滞相关的同步准则并且利用线性状态反馈控制器得到一些同步控制的结果, 其中控制器可以由Matlab软件求得. 最后给出一些数值仿真例子以说明同步准则的有效性.     

Pinning bipartite synchronization for coupled nonlinear systems with antagonistic interactions and switching topologies

This paper studies the bipartite synchronization in a network of nonlinear systems with antagonistic interactions and switching topologies. In order to obtain some conditions such that the network achieves bipartite synchronization for any initial conditions, we design a pinning scheme to pin a part of agents. Under the assumptions that all signed graphs are structurally balanced and the nonlinear system satisfies a one-sided Lipschitz condition, we derive conditions under which the network reaches bipartite synchronization for any initial conditions and arbitrary switching signals. For a general switching signal (especially the periodic switching signal), some conditions related to switching signal are obtained. Finally, we present two numerical examples to illustrate the effectiveness of the obtained results.     

离散混沌网络系统中共同噪声诱导同步的条件

噪声普遍存在于各种真实系统和人造系统中,它对系统的同步动力学具有多重影响.本文探索外部噪声对高维离散复杂网络系统同步行为的积极作用.首先构建外部共同噪声驱动下两个参数相同、未耦合的离散混沌网络模型,然后利用Birkhoff遍历定理与矩阵论等相关理论,严格证明了噪声诱导两个离散混沌网络系统取得同步的充分条件,进一步借助于具体的混沌网络模型,利用数值仿真验证了理论分析的有效性.数值模拟的结果表明当网络模型参数满足理论分析的充分条件时,共同噪声可以诱导两个参数相同、未耦合的离散混沌网络在随机意义下取得同步,而且同步效果不依赖于复杂网络拓扑结构的选取.     

Solvability conditions and design for synchronization of discrete‐time multiagent systems

This paper provides solvability conditions for state synchronization with homogeneous discrete‐time multiagent systems with a directed and weighted communication network under partial‐ or full‐state coupling. Our solvability conditions reveal that the synchronization problem is solvable for all possible, a priori given, set of graphs associated with a communication network only under the condition that the agents are at most weakly unstable (ie, agents have all eigenvalues in the closed unit disc). However, if an upper bound on the eigenvalues inside the unit disc of the row stochastic matrices associated with any graph in a given set of graphs is known, then one can achieve synchronization for a class of unstable agents. We provide protocol design for at most weakly unstable agents based on a direct eigenstructure assignment method and a standard H₂ discrete‐time algebraic Riccati equation. We also provide protocol design for strictly unstable agents (ie, agents have at least one eigenvalue outside the unit disc) based on the standard H₂ discrete‐time algebraic Riccati equation.     

Adaptive H_∞ Synchronization of Master-slave Systems with Mixed Time-varying Delays and Nonlinear Perturbations： An LMI Approach

This paper proposes an adaptive synchronization problem for the master and slave structure of linear systems with nonlinear perturbations and mixed time-varying delays comprising different discrete and distributed time delays. Using an appropriate Lyapunov-Krasovskii functional, some delay-dependent sufficient conditions and an adaptation law including the master-slave parameters are established for designing a delayed synchronization law in terms of linear matrix inequalities(LMIs). The time-varying controller guarantees the H _∞ synchronization of the two coupled master and slave systems regardless of their initial states. Particularly, it is shown that the synchronization speed can be controlled by adjusting the updated gain of the synchronization signal. Two numerical examples are given to demonstrate the effectiveness of the method.     

Synchronization of Instantaneous Coupled Harmonic Oscillators With Communication and Input Delays

This paper investigates the synchronization issue of instantaneous coupled harmonic oscillators with communication and input delays. A distributed synchronization algorithm is proposed for such oscillator systems, and some general algebraic criteria on exponential convergence are established for the algorithm. The main contributions of the present investigations include: (i) the directed network topology is first considered in the case of instantaneous interaction; (ii) both the time‐varying communication and input delays are simultaneously addressed; (iii) the effects of communication and input delays on synchronization performance of coupled harmonic oscillators are discussed. It is shown the communication delays have a more important impact than the input delays on determining synchronization dynamics of coupled harmonic oscillators. Explicitly, in absence of communication delays, coupled harmonic oscillators can achieve synchronization oscillatory motion, whereas, so long as communication delays are nonzero at infinite multiple impulsive times, its synchronization (or consensus) state is zero. Finally, numerical examples demonstrate the obtained theoretical results.     

Stochastic synchronization of delayed multiagent networks with intermittent communications: An impulsive framework

This paper investigates the stochastic synchronization problem of delayed multiagent networks with intermittent communications. Two kinds of impulsive effects are taken into account, ie, impulsive controller (positive impulsive effect) and impulsive disturbance (negative impulsive effect). Impulsive controller allows the synchronization to be realized and requires only state information exchange at discrete time instants such that the communication cost of bandwidth is reduced. Meanwhile, impulsive disturbance is inevitable in most of practical systems and therefore is taken into consideration at discrete time instants. Sufficient conditions for synchronization are given in terms of the graph topology, the control coupling gains, and the individual agent dynamics parameters, which indicates that synchronization can be realized if the impulsive effects coefficients and communication rate are suitably selected. Simulation results verify the effectiveness of the proposed synchronization protocol.     

Synchronization in a network of identical continuous‐ or discrete‐time agents with unknown nonuniform constant input delay

This paper studies the synchronization problem for multiagent systems with identical continuous‐ or discrete‐time agents with unknown nonuniform constant input delays. The agents are connected via full‐ or partial‐state coupling. The agents are assumed to be asymptotically null controllable, ie, all eigenvalues are in the closed left‐half complex plane for continuous‐time agents or in the closed unit disc for discrete‐time agents. We derive an upper bound for the input delay tolerance, which explicitly depends on the agent dynamics. Moreover, for any unknown delay satisfying this upper bound, a low‐gain–based protocol design methodology is proposed without relying on exact knowledge of the network topology such that synchronization is achieved among agents for any network graph in a given set.     

Clustering in diffusively coupled networks

This paper shows how different mechanisms may lead to clustering behavior in connected networks consisting of diffusively coupled agents. In contrast to the widely studied synchronization processes, in which the states of all the coupled agents converge to the same value asymptotically, in the cluster synchronization problem studied in this paper, we require all the interconnected agents to evolve into several clusters and each agent only to synchronize within its cluster. The first mechanism is that agents have different self-dynamics, and those agents having the same self-dynamics may evolve into the same cluster. When the agents’ self-dynamics are identical, we present two other mechanisms under which cluster synchronization might be achieved. One is the presence of delays and the other is the existence of both positive and negative couplings between the agents. Some sufficient and/or necessary conditions are constructed to guarantee n-cluster synchronization. Simulation results are presented to illustrate the effectiveness of the theoretical analysis.     

Admissible Consensus of Multi‐Agent Singular Systems

Consensus problems are studied for both continuous‐time and discrete‐time multi‐agent singular systems with time‐invariant and directed communication topologies. Under restricted system equivalence of singular agents, sufficient and necessary conditions are obtained for admissible consensus ability with static protocols, which are based on both the relative information of the dynamic states and the absolute information of the static states. For a network of continuous‐time singular systems, the existence of admissible consensualization can be cast into strong stabilizability of the agent dynamics. Once discrete‐time multi‐agent singular systems satisfy the condition of reaching nontrivial final consensus states, strong stabilizability is a sufficient condition to achieve admissible consensualization. Two algorithms are proposed to construct two protocols, which are based on a linear matrix inequality and a modified Riccati equation, respectively. Finally, the algorithms are illustrated by two simulation examples.     

Fault-tolerant cluster-wise clock synchronization for wireless sensor networks

Wireless sensor networks have received a lot of attention recently due to their wide applications, such as target tracking, environment monitoring, and scientific exploration in dangerous environments. It is usually necessary to have a cluster of sensor nodes share a common view of a local clock time, so that all these nodes can coordinate in some important applications, such as time slotted MAC protocols, power-saving protocols with sleep/listen modes, etc. However, all the clock synchronization techniques proposed for sensor networks assume benign environments; they cannot survive malicious attacks in hostile environments. Fault-tolerant clock synchronization techniques are potential candidates to address this problem. However, existing approaches are all resource consuming and suffer from message collisions in most of cases. This paper presents a novel fault-tolerant clock synchronization scheme for clusters of nodes in sensor networks, where the nodes in each cluster can communicate through broadcast. The proposed scheme guarantees an upper bound of clock difference between any nonfaulty nodes in a cluster, provided that the malicious nodes are no more than one third of the cluster. Unlike the traditional fault-tolerant clock synchronization approaches, the proposed technique does not introduce collisions between synchronization messages, nor does it require costly digital signatures.