Asynchronous Distributed Algorithms for Heading Consensus of Multi‐Agent Systems with Communication Delay

In this paper, we propose two asynchronous distributed protocols for the heading consensus of a multi‐agent group which cannot access a global coordinate system and a global time. Both the leaderless and leader‐following cases are addressed, and inter‐agent communication delay is taken into account. It is proved, under some standard connectivity assumptions, that our leaderless algorithm ensures the heading consensus provided the initial headings are not balanced; and the leader‐based algorithm guarantees the global heading consensus.     

Mach的面向对象的虚存管理实现方法

Ｍａｃｈ是一个新兴的操作系统，Ｍａｃｈ的虚存管理别具特色，本文介绍了Ｍａｃｈ的虚存环境、虚存管理的数据结构，算法及虚存实现。     

多自主体量化趋同与有限数据率趋同综述

对近年来系统控制学科的一个前沿热点领域——多自主体系统的量化趋同和有限数据率趋同问题进行了回顾和总结. 介绍了该领域产生和发展的背景及意义; 分门别类地回顾了该领域一些代表性成果和研究方法; 并结合多自主体系统和网络化控制的大背景,对该领域未来可能的研究方向进行了展望.     

均值模型下满足对数级收敛速度的动态系统

文章研究了在均值模型下,动态系统收敛至一致性状态所需的时间。在每一时间步内,节点计算其邻居的均值,并以计算结果作为自己的新值。我们考虑了当节点间的网络结构处于动态变化状态的情况。我们的分析证明了当节点的度在相邻时间点之间变化较小的情况下,即使仅满足微弱的连通性条件,动态变化的网络仍然可以保证动态系统会快速收敛到一致性状态。     

线性均方一致性问题的偏差估计

多智能体协同在传感网、社交网、分布式控制等诸多领域有着广泛的实际应用背景,一致性问题作为多智能体协同的基础,受到越来越多研究者的关注.在实际环境中,由于设备、通信干扰等诸多原因,信息在传递过程中通常会携有噪声,本文对噪声条件下一致性问题的系统偏差进行了研究,将求解一致性协议噪声偏差问题转化成矩阵范数的积分问题,根据矩阵迹与特征值的关系,利用范数不等式及积分中值定理,给出仅与增益函数和网络结构相关的一致性协议噪声偏差上界,为一致性系统在实际应用中的噪声估计奠定了理论基础.     

离散异质多智能体系统的分组一致性控制

针对一类混合异质多智能体系统的分组一致性控制问题进行了研究。具体分析了由一阶智能体和二阶智能体组成的混合异质系统,研究其在离散情况下的分组一致性。基于两个合理的假设提出了线性控制协议,运用代数图论、稳定性理论和矩阵理论,分析协议作用下闭环系统的系统矩阵及动态特性,取得了系统渐近实现分组一致性的充分条件,该条件与系统拓扑结构、采样周期以及控制参数有关。结论同时适用于有向拓扑与无向拓扑,最后通过仿真实例对所得分析结果进行了验证。     

A liveness condition for concurrent objects: x‐wait‐freedom

The liveness of concurrent objects despite asynchrony and failures is a fundamental problem. To that end several progress conditions have been proposed. Wait‐freedom is the strongest of these conditions: it states that any object operation must terminate if the invoking process does not crash. Obstruction‐freedom is a weaker progress condition as it requires progress only when a process executes in isolation for a long enough period. This paper explores progress conditions in n‐process asynchronous read/write systems enriched with base objects with consensus number x, 1<x≤n(i.e. objects that wait‐free solve consensus in a set of x processes). It is easy to solve consensus in such a system if progress is required only when one of the x processes allowed to access the underlying consensus object invokes this object and does not crash. This paper proposes and investigates a stronger progress condition that we call x‐wait‐freedom (n‐wait‐freedom is wait‐freedom). This condition includes additional scenarios in which progress is required even when none of the x processes allowed to access the underlying consensus object participates. The paper then presents and proves correct a consensus algorithm that satisfies this progress condition. Copyright © 2011 John Wiley & Sons, Ltd.     

Objects shared by Byzantine processes

Work to date on algorithms for message-passing systems has explored a wide variety of types of faults, but corresponding work on shared memory systems has usually assumed that only crash faults are possible. In this work, we explore situations in which processes accessing shared objects can fail arbitrarily (Byzantine faults). Received: December 2000 / Accepted: July 2002 RID="*" ID="*" A preliminary version of the results presented in this paper appeared in Proceedings of the 14th International Symposium on Distributed Computing, Toledo, Spain, October 2000.     

一类异质多智能体系统的一致性控制

针对一类由连续时间一阶和二阶智能体组成的异质多智能体系统,首先给出一阶和二阶智能体实现一致性的算法,其次利用图论和矩阵理论相关知识,在固定有向拓扑结构下,给出异质多智能体系统实现一致性的充要条件,且在一致性实现时给出一致性状态的确切表达式;在切换拓扑结构下,给出异质多智能体系统实现一致性的充分条件。最后给出数值算例验证了相关结论的有效性。     

类Paxos共识算法研究进展

随着互联网数据量和业务量的快速增长,集群规模越来越大,由于机器和网络等故障使得业务中断的可能性越来越高.如何实现一个容错的分布式系统十分重要.多机达成共识是分布式容错系统中一个最基础,最核心的问题.Paxos等一系列共识算法的出现有效地解决了这个问题.近年来,越来越多的系统使用共识相关技术,关于分布式共识算法的研究也层出不穷.这些共识算法可以被划分成2个大类：强领导者共识算法和弱领导者共识算法.随着远程直接内存访问(remote direct memory access, RDMA)等网络技术和现场可编程门阵列(field-programmable gate array, FPGA)等硬件技术的发展,又出现了一些结合新型网络和硬件技术的共识算法研究,用来提升分布式系统的性能.将从分布式共识算法发展历程的角度,介绍Paxos系列算法,阐述算法演进过程中的关键研究,讨论相关算法在不同场景下的优劣势,并展望该类算法的未来发展方向与前景.     

离散时间多智能体系统的一致性

研究了离散时间高维线性系统的一致性问题. 所考虑的系统可视为包含多个个体的多智能体系统, 每个个体的动力学行为与其他个体不同并受其他个体状态的影响. 本文建立了系统具有一致性的若干充分必要条件. 如果一致性函数存在, 文章给出了该函数的显式表达. 文末用一个数值例子说明了所得的理论结果.     

Consensus of nonlinear multi-agent systems with observer-based protocols

This paper is concerned with distributed pinning consensus problem for a class of nonlinear multi-agent system with observer-based protocols. Two types of state observers including local observer and distributed pinning observer are proposed for the single nonlinear agent with the first one designed by the local output information and the second one designed via the relative output information of its neighboring agents. According to the state information observed, a distributed pinning observer-based protocol is proposed for the leader-following consensus of the multi-agent system. Furthermore, two multi-step algorithms are presented to construct the observer gains and the protocol parameters for the proposed protocols respectively. It is shown that under the condition that the pinning joint communication topology contains a directed spanning tree, the sufficient criteria established can not only ensure the observation error to be globally asymptotically stable, but also guarantee the consensus of the multi-agent system to be solved asymptotically. Finally, two numerical examples are provided to demonstrate the effectiveness of the observer-based protocols.     

线性多智能体系统一致性问题的部分稳定性方法

提出了处理高阶线性多智能体系统一致性问题的线性变换.该线性变换将一致性问题转化为一个部分稳定问题.研究了一般线性协议下线性多智能体系统的三个问题: 1) 寻找一致性收敛判据; 2) 计算一致性函数; 3) 设计线性一致性协议的增益矩阵.具体来说,提出了基于矩阵 Hurwitz 稳定的一致性收敛的充分必要条件,给出了一致性函数的解析表达式,同时建立了一致性协议的增益矩阵与多智能体系统收敛时间和一致性精度的关系,并针对预先给定的收敛时间和精度要求设计了增益矩阵.     

异质相依群体系统的协同一致性追踪

针对具有固定通信拓扑的异质相依群体系统的协同一致性追踪问题,从个体性质不同和子群体拓扑结构不同的角度出发,构建异质系统的相依模型.为了通过局部信息实现异质相依群体系统的一致性追踪,设计了一类分布式一致性追踪控制协议.随后,对于固定通信拓扑的情况,给出相应的充分条件确保一致性追踪的实现.定义了相依个体比例参数Pr并且分析了该参数对群体系统协同一致性追踪的影响.最后,通过仿真实例说明理论分析的有效性.     

Consensus problems in networks of agents with double-integrator dynamics and time-varying delays

In this article, we consider consensus problems in networks of agents with double-integrator dynamics and non-uniform time-varying delays. The agent dynamics is adopted as a typical point mass model based on Newton's law. Without assuming that the weighting factors in the information update schemes are non-negative, we propose two protocols such that both the state and the velocity of agents achieve consensus. An equivalent reduced-order system is introduced to analyse the convergence of the protocols. Some necessary and (or) sufficient conditions for consensus are established in terms of linear matrix inequalities. Simulation results are provided that demonstrate the effectiveness of our theoretical results.     

远端内存交换系统的设计与实现

随着高带宽和低延迟的网络的出现,远端内存到本地内存的传输速率大于本地磁盘到本地内存的传输速率,使用远端内存代替磁盘缓存应用程序的数据将成可能。RMSS是一个基于Linux2.4内核的远端内存交换系统,它以内核模块的形式提供给用户。通过RMSS,应用程序可以透明的访问远端内存。根据本文实验结果,得出在快速网络中,使用RMSS会比交换到磁盘的性能要好。本文也对RMSS中的可靠性进行了分析,并提出了几种解决方案。     

基于事件触发的二阶多智能体系统平均一致性

针对二阶多智能体系统在固定无向拓扑下的平均一致性问题,为减少不必要的资源浪费,给出一种基于事件触发控制的一致性算法．首先,针对每个智能体设计基于状态误差形式的触发函数,只有当状态误差达到特定值时智能体才触发事件,在两个相邻事件触发时刻之间保持控制输入不变．然后,利用模型转换思想将系统的一致性问题转化为稳定性问题,并利用矩阵理论和李亚普诺夫理论给出系统达到平均一致的充分条件．最后,通过仿真实验验证该理论方案的有效性.     

基于事件触发的离散多智能体二分一致性

针对一阶离散多智能体系统,研究了事件触发控制下的二分一致性问题.首先考虑智能体间通信拓扑结构为无向连通结构平衡图的情形,针对各智能体设计事件触发控制,包括仅依赖于自身及邻居智能体采样状态的控制输入,以及仅依赖自身状态的事件触发条件,实现了对通信资源的节约利用.基于图论、离散系统稳定性理论,证明系统能够实现二分一致性.同时,合理设置控制输入及事件触发条件中参数,保证系统不存在Zeno现象.之后,进一步分析设计了包含有向生成树的结构平衡图下,多智能体系统的事件触发控制.最后利用仿真实例验证了理论结果的有效性.     

Consensus for formation control of multi‐agent systems

This study considers the formation problem for multi‐agent systems, which are described by the second‐order dynamics on nonlinear manifolds SE(2) and SE(3). In particular, the model of each agent contains information about its attitude. Using a consensus strategy, a control law is developed to guarantee that any desired formation can be achieved asymptotically under the conditions of complete or tree‐shaped communication topologies. Numerical simulations are presented to verify the theoretical results. Copyright © 2014 John Wiley & Sons, Ltd.     

离散线性一致性算法噪声问题研究

多智能体一致性问题在传感网、社交网、协同控制等诸多领域有着广泛的实际应用背景, 本文对离散线性一致性算法的噪声问题进行了研究, 证明了离散线性 一致性算法的噪声不可控性; 提出基于抑噪算子ε(t)的噪声控制策略, 指出当ε(t)为t-0.5的高阶无穷小时, 抑噪后的一致性算法噪声可控; 分析了抑噪算子对一致性 算法收敛性的影响, 证明了在无噪声条件下, 当抑噪算子ε(t为t-1的低阶无穷小时, 抑噪后的一致性算法依然可以使Agent收敛至原收敛状态x*.在上述结论基础上进一步指出, 当t→∞ 时, 若抑噪算子ε(t)的阶在t-0.5~t-1之间, 所有Agent 的状态将以原收敛状态x* 为中心呈正态分布. 最后, 以DHA 为例对相应理论结果进行了验证和讨论. 本文为线性一致性算法的噪声控制提供了理论依据, 对抑噪算s子的确定有较强的指导意义.