Distributed consensus algorithm for networked Euler-Lagrange systems with self-delays and uncertainties

A distributed coordinated consensus problem for multiple networked Euler-Lagrange systems is studied. The communication between agents is subject to time delays, unknown parameters and nonlinear inputs, but only with their states available for measurement. When the communication topology of the system is connected, an adaptive control algorithm with selfdelays and uncertainties is suggested to guarantee global full-state synchro-nization that the difference between the agent’s positions and ve-locities asymptotically converges to zero. Moreover, the distributed sliding-mode law is given for chaotic systems with nonlinear inputs to compensate for the effects of nonlinearity. Finally, simulation results show the effectiveness of the proposed control algorithm.     

Distributed tracking for networked Euler-Lagrange systems without velocity measurements

The problem of distributed coordinated tracking control for networked Euler-Lagrange systems without velocity measurements is investigated. Under the condition that only a portion of the followers have access to the leader, sliding mode estimators are developed to estimate the states of the dynamic leader in finite time. To cope with the absence of velocity measurements, the distributed observers which only use position information are designed. Based on the outputs of the estimators and observers, distributed tracking control laws are proposed such that all the fol- lowers with parameter uncertainties can track the dynamic leader under a directed graph containing a spanning tree. It is shown that the distributed observer-controller guarantees asymptotical stability of the closed-loop system. Numerical simulations are worked out to illustrate the effectiveness of the control laws.     

Fast consensus seeking for multi-agent systems

For multi-agent systems based on the local information,the agents automatically converge to a common consensus state and the convergence speed is determined by the algebraic connectivity of the communication network.To study fast consensus seeking problems of multi-agent systems in undirected networks,a consensus protocol is proposed which considers the average information of the agents’ states in a certain time interval,and a consensus convergence criterion for the system is obtained.Based on the frequency-domain analysis and algebra graph theory,it is shown that if the time interval is chosen properly,then requiring the same maximum control effort the proposed protocol reaches consensus faster than the standard consensus protocol.Simulations are provided to demonstrate the effectiveness of these theoretical results.     

Multi-agent consensus with time-varying delays and switching topologies

The consensus problems of multi-agents with time-varying delays and switching topologies are studied. First, assume that an agent receives state information from its neighbors with fixed communication delays and processes its own state information with time-varying self-delay respectively. The state time-delay feedback is introduced into the existing consensus protocol to begenerate an improved protocol. Then a sufficient condition is derived which can make the system with time-varying self-delays achieve the consensus. On this basis, a specific form of consensus equilibrium influenced by the initial states of agents, time-delays and state feedback intensity is figured out. In addition, the multi-agent consensus is considered with time-varying topologies. Finally, simulations are presented to il ustrate the validity of theoretical results.     

Improvement for consensus performance of multi-agent systems based on delayed-state-derivative feedback

The delayed-state-derivative feedback (DSDF) is introduced into the existing consensus protocol to simultaneously improve the robustness to communication delay and accelerate the convergence speed of achieving the consensus. The frequency-domain analysis, together with the algebra graph the- ory, is employed to derive the sufficient and necessary condition guaranteeing the average consensus. It is shown that introducing the DSDF with the proper intensity in the existing consensus protocol can improve the robustness to communication delay. By analyzing the effect of DSDF on the closed-loop poles, this paper proves that for a supercritical-delay multi-agent system, this strategy can also accelerate the convergence speed of achieving the consensus with provided the proper intensity of the DSDF. Simulations are provided to demonstrate the effectiveness of the theoretical results.     

Consensus design for continuous-time multi-agent systems with communication delay

This paper investigates a consensus design problem for continuous-time first-order multiagent systems with uniform constant communication delay.Provided that the agent dynamic is unstable and the diagraph is undirected,sufficient conditions are derived to guarantee consensus.The key technique is the adoption of historical input information in the protocol.Especially,when agent＇s own historical input information is used in the protocol design,the consensus condition is constructed in terms of agent dynamic,communication delay,and the eigenratio of the network topology.Simulation result is presented to validate the effectiveness of the theoretical result.     

Leader-following consensus protocols for formation control of multi-agent network

Two protocols are presented,which can make agents reach consensus while achieving and preserving the desired formation in fixed topology with and without communication timedelay for multi-agent network.First,the protocol without considering the communication time-delay is presented,and by using Lyapunov stability theory,the sufficient condition of stability for this multi-agent system is presented.Further,considering the communication time-delay,the effectiveness of the protocol based on Lyapunov-Krasovskii function is demonstrated.The main contribution of the proposed protocols is that,as well as the velocity consensus is considered,the formation control is concerned for multi-agent systems described as the second-order equations.Finally,numerical examples are presented to illustrate the effectiveness of the proposed protocols.     

Consensus algorithm for multiple quadrotor systems under fixed and switching topologies

The distributed leadless consensus problem for multiple quadrotor systems under fixed and switching topologies is investigated. The objective is to design protocols achieving consensus for networked quadrotors＇ positions and attitudes. Because the model of a quadrotor is a strong high-order nonlinear coupling system, the approach of feedback linearization is employed to transform the model into a group of four linear subsystems among which there is no coupling. Then, a consensus algorithm is proposed which consists of a local feedback controller and interactions from the finite neighbors under fixed undirected topologies. Especially, the problem of choosing the parameters in the consensus algo-rithm is also addressed, enlightened by the results of the robust control theory. Furthermore, it is proved that the proposed algo-rithm also guarantees the consensus under undirected switching topologies. Simulation results show the effectiveness of the pro- posed algorithm.     

Robust H∞ controller design for sampled-data systems with parametric uncertainties

This article investigates the problem of robust H∞ controller design for sampled-data systems with time-varying norm-bounded parameter uncertainties in the state matrices. Attention is focused on the design of a causal sampled-data controller, which guarantees the asymptotical stability of the closed-loop system and reduces the effect of the disturbance input on the controlled output to a prescribed H∞ performance bound for all admissible uncertainties. Sufficient condition for the solvability of the problem is established in terms of linear matrix inequalities (LMIs). It is shown that the desired H∞ controller can be constructed by solving certain LMIs. An illustrative example is given to demonstrate the effectiveness of the proposed method.     

单边Lipschitz非线性多智能体系统一致性追踪控制

针对单边Lipschitz非线性多智能体系统,提出了一种分布式一致性控制方法.首先,构建了领导-跟随者动力学结构,用于实现单边Lipschitz多智能体系统的追踪控制.然后,设计了单边Lipschitz非线性多智能体系统的一致性控制协议,可根据智能体之间局部交互信息构建分布式反馈控制,并将系统的一致性追踪问题转化为系统...     

Robust decentralized H∞ control of multi-channel systems with norm-bounded parametric uncertainties

A robust decentralized H∞ control problem for uncertain multi-channel systems is considered. The uncertainties are assumed to be time-invariant, norm-bounded, and exist in both the system and control input matrices. The dynamic output feedback is mainly dealt with. A necessary and sufficient condition for the uncertain multi-channel system to be stabilized robustly with a specified disturbance attenuation level is derived based on the bounded real lemma, which is reduced to a feasibility problem of a nonlinear matrix inequality (NMI). A two-stage homotopy method is used to solve the NMI iteratively. First, a decentralized controller for the nominal system with no uncertainty is computed by imposing structural constraints on the coefficient matrices of the controller gradually. Then the decentralized controller is modified, again gradually, to cope with the uncertainties. On each stage, a variable is fixed alternately at the iterations to reduce the NMI to a linear matrix inequality (LMI). A given example shows the efficiency of this method.     

Uniformed model of networked control systems with long time delay

Feedback control systems wherein the control loops are closed through a real-time network are called networked control systems （NCS）. The defining feature of an NCS is that information is exchanged using a network among control system components. Two new concepts including long time delay and short time delay are proposed. The sensor is almost always clock driven. The controller or the actuator is either clock driven or event driven. Four possible driving modes of networked control systems are presented. The open loop mathematic models of networked control systems with long time delay are developed when the system is driven by anyone of the four different modes. The uniformed modeling method of networked control systems with long time delay is proposed. The simulation results are given in the end.     

基于不确定理论的退化数据分析方法

作为可靠性领域传统的数学工具,概率论难以解决现代可靠性工程面临的难题。本文以不确定理论在退化数据分析中的应用为切入点,阐述了不确定理论的基本公理、运算法则与不确定统计方法,给出了基于确信可靠性理论的可靠性建模思路,提出了不确定失效阈值情形下的退化数据分析与可靠性建模方法。利用时变不确定正态分布建立产品的退化方程,根据专家知识建立失效阈值的不确定分布进而构建裕量方程,最终根据度量方程推导出产品可靠性模型。使用不确定统计中的极大似然估计法与假设检验法解决参数估计与模型验证问题。案例分析说明如果不考虑失效阈值的不确定性,会造成可靠性评估结果较大偏差。研究表明不确定理论适合处理退化数据分析中的不确定性难题,具有广阔的应用前景。     

一类参数不确定非线性系统的故障检测与重构

飞行器在全包络上表现出明显的气动参数不确定性,以某无人机纵向模型为研究对象,提出一种不确定参数在线估计的自适应观测器故障重构方法。首先,将系统状态方程描述为一类带时变参数的仿射非线性结构,在参数增广系统能观性分析基础上,采用增广容积卡尔曼滤波(augmented cubature Kalman filter, ACKF)算法实现气动参数在线估计,以克服鲁棒性死区故障检测方法的保守性,提高检测灵敏度。其次,将所估计参数用于自适应观测器设计,由于Lie导数分析方法保证了对象系统的能观性,故系统不必满足文献方法中的特定规范形式;在此基础上,给出了故障检测自适应阈值和故障参数调节律,并分析了估计误差的收敛性。仿真实验表明了所提方法的有效性。     

Decentralized robust stabilization of discrete-time fuzzy large-scale systems with parametric uncertainties: a LMI method

1. INTRODUCTION Large-scale dynamic system theory has been intensi- vely studied during the past decade[1～3], but for fuzzy large-scale systems, namely large-scale systems comp- osed of a series of fuzzy subsystems, has been seldom done in literature. In Ref.[4], decentralized stabiliz- ation problem of fuzzy large-scale systems composed of a series of fuzzy subsystems was considered. Sufficient conditions for asymptotic stability of the fuzzy large-scale system and design methods of dec…     

一类非线性大系统的鲁棒变结构观测器

研究了一类具有结构和参数不确定性的非线性关联大系统状态观测器设计问题。在假定非线性系统的线性部分是可观测、不确定性和关联项满足Lipschitz条件的情况下,利用变结构控制的思想提出了一种非线性状态观测器设计方案,并证明了该观测器的指数收敛特性。所设计的观测器对结构和参数不确定性具有较强的鲁棒性。最后给出仿真研究说明了所提方法的有效性。     

Consensus problem of second-order multi-agent systems with time-varying communication delay and switching topology

Leader-following stationary consensus problem is investigated for the second-order multi-agent systems with timevarying communication delay and switching topology.Based on Lyapunov-Krasovskii functional and Lyapunov-Razumikhin functions respectively,consensus criterions in the form of linear matrix inequality (LMI) are obtained for the system with time-varying communication delays under static interconnection topology converging to the leader’s states.Moreover,the delay-dependent consensus criterion in the form of LMI is also obtained for the system with time-invariant communication delay and switching topologies by constructing Lyapunov-Krasovskii functional.Numerical simulations present the correctness of the results.     

有包丢失的动态输出反馈奇异网络化系统稳定性分析

基于正则、无脉冲的奇异被控对象,研究了同时具有时延和数据包丢失的动态输出反馈网络控制系统的建模和稳定性问题。 当时延不大于一个采样周期、数据包丢失率一定时,将动态输出反馈网络控制系统建模为数据包丢失率约束的异步动态切换系统,利用切换系统和线性矩阵不等式方法,推导出数据包丢失率约束的系统指数稳定的充分条件,并且给出了系统指数稳定的指数衰减率以及最大容许数据包丢失率。仿真实验说明分析方法和研究结果是有效可行的。     

Guaranteed cost control for discrete-time networked control systems with random Markov delays

The guaranteed cost control for a class of uncertain discrete-time networked control systems with random delays is addressed.The sensor-to-controller (S-C) and contraller-to-actuator (C-A) random network-induced delays are modeled as two Markov chains.The focus is on the design of a two-mode-dependent guaranteed cost controller,which depends on both the current S-C delay and the most recently available C-A delay.The resulting closed-loop systems are special jump linear systems.Sufficient conditions for existence of guaranteed cost controller and an upper bound of cost function are established based on stochastic Lyapunov-Krasovakii functions and linear matrix inequality (LMI) approach.A simulation example illustrates the effectiveness of the proposed method.     

凸多面体不确定随机时滞系统的非脆弱鲁棒镇定

针对具有凸多面体不确定性的随机时滞系统,讨论了非脆弱鲁棒指数镇定问题,其中非脆弱控制器中的不确定性采用的是凸多面体不确定描述。基于Lyapunov直接法,采用了与参数相关的Lyapunov krasovskii泛函,并结合自由权矩阵方法, 使得Lyapunov矩阵与系统矩阵分离,从而获得了系统的完全基于线性矩阵不等式的时滞相关非脆弱鲁棒镇定的充分条件。最后,用例子说明了结果的有效性。