多智能体沿多条给定路径编队运动的有向协同控制

研究了在有向通信连接下二阶积分器描述的多智能体沿多条给定路径编队运动的控制器设计及其稳定性分析问题. 智能体的动态和指定路径都是在固定直角坐标系下描述的. 通过引入路径函数来设计路径跟踪控制, 根据路径函数与弧长的关系来设计编队控制律, 使得多智能体沿期望路径的位置和速度在规定队形下达到一致. 利用图论证明, 当通信拓扑对应的有向图具有全局可达点时, 设计的编队控制系统是渐近稳定的. 本文设计的有向协同控制律可以应用于区域的信息优化采集.     

Integral sliding mode-based attitude coordinated tracking for spacecraft formation with communication delays

This paper investigates the attitude coordinated tracking control for a group of rigid spacecraft under directed communication topology, in which inertia uncertainties, external disturbances, input saturation and constant time-delays between the formation members are handled. Initially, the nominal system with communication delays is studied. A delay-dependent controller is proposed by using Lyapunov–Krasovskii function and sufficient condition for system stability is derived. Then, an integral sliding manifold is designed and adaptive control approach is employed to deal with the total perturbation. Meanwhile, the boundary layer method is introduced to alleviate the unexpected chattering as system trajectories cross the switching surface. Finally, numerical simulation results are presented to validate the effectiveness and robustness of the proposed control strategy.     

基于SO(3)的多四旋翼无人机编队协同控制

针对多四旋翼无人机系统的编队飞行问题,提出了基于特殊正交群SO(3)的协同控制设计方法.在给出编队空间队形和通信拓扑描述后,建立了多四旋翼无人机系统SO(3)控制模型.由于SO(3)与传统俯仰/偏航/滚转三通道模型具有不同的结构,文中进一步研究了SO(3)中无人机之间相对误差的表示方法,设计了适用于多飞行器的SO(3)控制器实现对编队和姿态的协同控制.推力控制器用于调节无人机的位置与速度,并在此基础上构造旋转矩阵形式的姿态协同指令.文中相应设计了SO(3)姿态控制器用于实现指令跟踪,最后从理论上对协同稳定性进行了分析.提出的控制方法能够使得多四旋翼无人机形成期望的队形,并且保持姿态一致进行稳定飞行.仿真结果验证了本文方法的有效性.     

基于优化通信质量的PEGASIS协议改进算法

在传统的PEGASIS（power efficient gathering in sensor information system）协议基础上,提出一种可优化全网通信质量的改进算法。新算法在链头生成阶段借鉴了蚁群相遇算法原理,采用双链头成链方法进行数据传输,大大缩短了单链路网络的通信时延;在拓扑成链的过程中引入距离阈值作为限定权重,进而计算出基于能耗均衡与通信质量的最优路径。实验结果表明,该算法有效地优化了整体网络的通信质量。     

An output formation consensus control for leader–follower networked multi-agent systems under communication constraints and switching topologies

In this paper, the formation consensus problem for a class of leader–follower networked multi-agent systems under communication constraints and switching topologies is investigated. A networked predictive control scheme is proposed to achieve stability and output formation consensus with the switching topology, capable of compensating for data loss and time delays in the network. By equating the whole closed-loop networked multi-agent system with the proposed control scheme to the corresponding switched system, the sufficient and necessary condition of output formation consensus and stability for agents is given. Finally, using three-degree-of-freedom air-bearing spacecraft simulators as the control objects, the proposed scheme is demonstrated to be able to actively compensate for the communication constraints through numerical simulations, and it is also verified to have a good control performance by further realizing the formation task of the simulators through practical experiments.     

基于最优方案VANET协议的研究

由于网络拓扑结构频繁变化,节点之间物理物理距离超过通信距离时,消息不能转发,信息没有及时更新。目前市场销售的大部分导航软件一般采用的是最短路径策略或最少收费策略,这种方式在一般情况下能够满足人们的某一出行要求,但对于当前交通路况拥堵的情况下,这几种策略显然是行不通的,最短路径或最少收费的方式不仅不能给使用者节省时间,还可能降低了出行的效率。这种方式以远远不能满足人们出行的需求,如何保障即尽可能选择最短路径又能够保证通信的畅通,是本论文研究的方向。     

基于分布式模型预测控制的无人机编队控制

针对多四旋翼无人机编队在巡航飞行过程中队形形成和保持问题,采用分布式模型预测控制方法将该问题转化为在线滚动优化问题.建立线性时不变的编队运动模型,进而在考虑状态和输入约束,不考虑时延、外界干扰、噪声的情况下,利用领航跟随策略设计一种分布式模型预测控制器,通过引入自身和邻居的假设状态轨迹设计代价函数.其中邻居信息的交互是在有向、时不变通信拓扑结构下进行的.基于该控制器,无人机能够在跟踪目标轨迹的同时,快速形成预先设定的队形并保持队形飞行.通过引入终端等式约束保证系统稳定,进而将目标函数作为Lyapunov函数,给出编队系统渐近稳定的充分条件.最后,利用6架无人机仿真验证控制算法的有效性和优越性.     

Ad Hoc网络下的发布/订阅系统路由协议

发布/订阅系统为分布式网络中系统间的异步通讯提供了便捷的途径,事件的路由策略是基于内容的发布/订阅系统的关键问题之一。文章采用目的地动态更新与划分、逆向最短路径转发等策略,提出一种有环图下支持订阅覆盖的路由算法;通过引入订阅挂起、激活操作,以及与订阅对应的事件缓存方法,设计了一种新型的拓扑重构算法;通过引入网络分簇技术、拓扑重构算法、客户路由切换算法,设计了一种新型的面向移动Ad Hoc网络的发布/订阅系统路由协议,提高了系统的扩展性。     

Leader-following control of multiple nonholonomic systems over directed communication graphs

This paper considers the leader-following control problem of multiple nonlinear systems with directed communication topology and a leader. If the state of each system is measurable, distributed state feedback controllers are proposed using neighbours’ state information with the aid of Lyapunov techniques and properties of Laplacian matrix for time-invariant communication graph and time-varying communication graph. It is shown that the state of each system exponentially converges to the state of a leader. If the state of each system is not measurable, distributed observer-based output feedback control laws are proposed. As an application of the proposed results, formation control of wheeled mobile robots is studied. The simulation results show the effectiveness of the proposed results.     

Weighted predictor‐feedback formation control in local frames under time‐varying delays and switching topology

This article presents a novel control strategy based on predictor‐feedback delay compensation for multiagent systems to reach a prescribed target formation under unknown but bounded communication delays and switching communication topology. Both communication delays and network topology can be subjected to arbitrarily‐fast time variations. The key idea is to implement predictor‐feedback strategies using only relative measurements between agents expressed in each local agent's frame, with the aim to counteract the negative effect of time delays. Nevertheless, due to the decentralized nature of the control, the presence of time‐varying delays and switching communication topology, only partial delay compensation is possible. Despite this, we show that better performance can be achieved with our proposal with respect to nonpredictor control schemes by introducing a weighting factor for predictor‐feedback terms in the control law. Sufficient conditions based on Linear Matrix Inequalities for robust stability are also provided, which allow to easily design the controller parameters in order to maximize the speed of convergence. Finally, simulation results are provided to show the effectiveness of the proposed approach.     

具有定常输入的二阶多智能体系统的平均一致性滤波

本文考察了具有定常输入的二阶多智能体系统平均一致性滤波问题,提出了一种比例-积分一致性滤波算法。在定常输入和固定对称连通拓扑的前提下,根据Routh判据和Nyquist判据分别得到二阶多智能体系统在无时延和相同通信时延约束下渐近收敛一致的收敛条件,且多智能体系统最终一致性状态为定常输入的平均值。最后,通过由5个智能体组成的多智能体系统在连通拓扑结构下的数值仿真,验证了理论结果的正确性。     

Cooperative path following of constrained autonomous vehicles with model predictive control and event‐triggered communications

We present a solution to the problem of multiple vehicle cooperative path following (CPF) that takes explicitly into account vehicle input constraints, the topology of the intervehicle communication network, and time‐varying communication delays. The objective is to steer a group of vehicles along given spatial paths, at speeds that may be path dependent, while holding a feasible geometric formation. The solution involves decoupling the original CPF problem into two subproblems: (i) single path following of input‐constrained vehicles and (ii) coordination of an input‐constrained multiagent system. The first is solved by adopting a sampled‐data model predictive control scheme, whereas the latter is tackled using a novel distributed control law with an event‐triggered communication (ETC) mechanism. The proposed strategy yields a closed‐loop CPF system that is input‐to‐state‐stable with respect to the system's state (consisting of the path following error of all vehicles and their coordination errors) and the system's input, which includes triggering thresholds for ETC communications and communication delays. Furthermore, with the proposed ETC mechanism, the number of communications among the vehicles are significantly reduced. Simulation examples of multiple autonomous vehicles executing CPF maneuvers in 2D under different communication scenarios illustrate the efficacy of the CPF strategy proposed.     

Consensus based overlapping decentralized estimation with missing observations and communication faults

In this paper a new algorithm for discrete-time overlapping decentralized state estimation of large scale systems is proposed in the form of a multi-agent network based on a combination of local estimators of Kalman filtering type and a dynamic consensus strategy, assuming intermittent observations and communication faults. Under general conditions concerning the agent resources and the network topology, conditions are derived for the convergence to zero of the estimation error mean and for the mean-square estimation error boundedness. A centralized strategy based on minimization of the steady-state mean-square estimation error is proposed for selection of the consensus gains; these gains can also be adjusted by local adaptation schemes. It is also demonstrated that there exists a connection between the network complexity and efficiency of denoising, i.e., of suppression of the measurement noise influence. Several numerical examples serve to illustrate characteristic properties of the proposed algorithm and to demonstrate its applicability to real problems.     

太阳能无人机群基于通信决策的节能连接控制

太阳能无人机的展弦比随着续航要求的提高而不断增大,而拥有大展弦比的无人机不利于快速部署,针对该问题提出了一种太阳能无人机群基于通信决策的节能连接控制策略,并给出了确定最优连接顺序的方法,达到将多架中小型太阳能无人机进行连接,组成更节能的大展弦比无人机的目的.首先,利用扩展卡尔曼滤波对无人机的状态进行估算.其次,通过信息熵评估态势对无人机的飞行轨迹和航速进行调整.最后,通过仿真演示了虚拟无人机的实时连接过程.研究结果证明了按最优连接顺序将无人机连接后可以显著降低编队整体的最终能量消耗,而基于态势感知的通信策略能够有效降低通信频次,优化编队的连接控制.     

无标度网络中基于最短路径免疫策略的病毒传播研究

传统病毒免疫策略大多基于网络的全局拓扑信息。然而现实生活中的大部分复杂网络仅仅只能了解其局部 拓扑信息。鉴于许多实际复杂网络具有无标度特性,研究了在无标度复杂演化网络中基于网络局部拓扑信息最短路 径免疫策略的病毒传播现象。利用平均场理论建立含个体抵杭力重要因素的无标度网络病毒传播模型,并引入基于 最短路径的免疫策略。比较了随机免疫、目标免疫和最短路径免疫3种策略对无标度复杂网络病毒传播的影响,结果 表明了基于最短路径免疫策略的有效性。     

Consensus problem of networked multi-agent systems with constant communication delay: stochastic switching topology case

This article proposes an observer-based control strategy for networked multi-agent systems with constant communication delay and stochastic switching topology. First, using the system transformation method, the mean-square consensus problem of multi-agent systems can be converted into the mean-square stability problem of an equivalent system, and some equivalent conditions concerning the mean-square consensus are presented. Then, an example is given to illustrate that the connection weights should be regarded as the parameters to be designed, since they have a great effect on the mean-square consensus of multi-agent systems. By choosing appropriate connection weights, the mean-square consensus problem can be converted into the mean-square stabilisation problem of N-1 delay systems with stochastic switching signal, whose related observer-based stabilisability criteria can be established in the form of linear matrix inequalities (LMIs). Furthermore, if the LMIs are feasible, the multi-agent systems achieve mean-square consensus if and only if the union of graphs in the switching topology set has a directed spanning tree. Finally, numerical simulations are given to illustrate our results.     

多星系统相对轨道的自适应协同控制

基于一致性理论,在无向拓扑结构上对多星系统相对轨道的协同控制问题进行了研究.本文考虑近地卫星相对轨道的非线性方程,首先设计控制律使得多星系统形成目标队形,并给出了速度阻尼和通信拓扑(相对速度间的拓扑关系)连通性之间的关系;其次,针对卫星质量具有不确定性的情形,设计了新的辅助变量,提出了自适应的协同控制律,这里要求传感(相对位置间的拓扑关系)和通信具有相同的拓扑结构.最后对4颗卫星的编队飞行进行了仿真分析,仿真结果表明本文设计的协同控制律是有效可行的.     

无线城域网综合资源调度策略设计与实现

宽带无线城域网是当今无线通信领域中的一个热点,而其中的资源调度策略直接关系到系统性能的优劣。本文针对IEEE802.16标准下的宽带无线接入系统设计了一套能够保证用户QoS的资源调度和分配方案,该方案由接纳控制方案、请求机会分配方案及带宽分配方案三部分组成,它的双层调度机制能够针对不同QoS等级的业务提供不同的调度方案,满足用户的QoS要求。     

On the Rendezvous Problem for Multiple Nonholonomic Agents

In this note, a decentralized feedback control strategy that drives a system of multiple nonholonomic unicycles to a rendezvous point in terms of both position and orientation is introduced. The proposed nonholonomic control law is discontinuous and time-invariant and using tools from nonsmooth Lyapunov theory and graph theory the stability of the overall system is examined. Similarly to the linear case, the convergence of the multi-agent system relies on the connectivity of the communication graph that represents the inter-agent communication topology. The control law is first defined in order to guarantee connectivity maintenance for an initially connected communication graph. Moreover, the cases of static and dynamic communication topologies are treated as corollaries of the proposed framework     

Controllability of heterogeneous multi-agent systems under directed and weighted topology

This paper considers the controllability problem for both continuous- and discrete-time linear heterogeneous multi-agent systems with directed and weighted communication topology. First, two kinds of neighbour-based control protocols based on the distributed protocol of first-order and second-order multi-agent systems are proposed, under which it is shown that a heterogeneous multi-agent system is controllable if the underlying communication topology is controllable. Then, under special leader selection, the result shows that the controllability of a heterogeneous multi-agent system is solely decided by its communication topology graph. Furthermore, some necessary and/or sufficient conditions are derived for controllability of communication topology from algebraic and graphical perspectives. Finally, simulation examples are presented to demonstrate the effectiveness of the theoretical results.