无领航者的多Euler-Lagrange系统有限时间一致性算法

本文针对无领航者的多Euler-Lagrange系统,设计了一种分布式有限时间一致性控制算法.该算法只利用相邻个体的位置信息和自身的速度信息作为输入,使得网络化Euler-Lagrange系统在有限时间内达到一致性.考虑到闭环Euler-Lagrange系统的非自主性,运用Matrosov定理、Lyapunov稳定性定理和有限时间稳定性定理等对所设计的控制器的稳定性进行了证明,并进行了数值仿真实验,验证了控制器的有效性.     

含自时延和通信时延的Euler-Lagrange系统自适应一致性算法

针对动力学方程中含未知参数的多Euler-Lagrange系统的一致性控制问题,设计了一种分布式自适应协调控制器.该控制器容许多Euler-Lagrange系统的通信拓扑为一般的有向图,并允许通信时延和自时延的同时存在.利用Barblata定理、Lyapunov稳定性定理和LMI方法等对控制器的稳定性进行了证明,并设计了数值仿真实验,仿真结果证明了控制算法的有效性.     

通信时延下多智能体系统的安全一致性控制

研究了离散时间多智能体系统存在通信时延条件下的安全一致性问题.本文的目标是设计一种一致性控制算法能够使得网络中各正常智能体抵御敌对智能体的攻击并实现最终状态一致.该算法仅利用个体的自身状态和相邻个体的时延信息作为控制输入,并根据控制器参数、拓扑属性和通信时延,获得了所提算法实现收敛的充要条件.最后,通过仿真实例对理论结果进行了验证.     

复杂动态网络自适应有限时间同步控制

本文利用自适应控制的方法,研究了复杂动态网络有限时间同步控制问题.针对网络的耦合权重已知和耦合权重未知两种情况,分别设计了相应的自适应控制器和参数自适应律.利用有限时间稳定性定理和Lyapunov稳定性理论,证明了复杂动态网络的误差动态系统是有限时间稳定的,并给出了同步过渡时间上界的估计.最后,利用数值算例验证了本文结论的有效性.     

基于快速反射镜的自适应控制算法研究

捕获、跟踪和瞄准(ATP)系统是进行高速大容量激光通信的核心,在长距离激光通信中大气等外界扰动产生的光斑抖动严重影响了激光通信终端间的精确对准,大大降低了通信链路的稳定性和通信质量.为抑制光斑抖动造成的影响,提高对目标的跟踪精度,提出一种改进的快速反射镜(FSM)控制方法.分析了自适应控制和常规比例-积分-微分(PID)控制的特点,并论述了结合两种算法进行复合控制的优势,根据李雅普诺夫(Lyapunov)理论提出参考模型自适应PID控制算法,并对常规PID和参考模型自适应PID复合控制算法进行仿真分析和对实际光斑抖动的闭环跟踪实验.实验结果显示:自适应PID控制器获得的超调为2％,上升时间为3 ms,跟踪精度优于2μrad,全面优于常规PID控制算法.与传统PID控制相比,文中提出的控制算法对抑制光斑抖动具有更好的控制效果.     

联合连通时变时延网络中多EL系统协调控制北大核心CSCD

针对非线性Euler-Lagrange(EL)系统中通信时延和网络切换并存的情形,在把网络化EL系统分为连通个体和孤立个体两种类型的控制架构中,分别对这两种个体设计不同的协调控制律,连通个体将自身与邻居个体的状态差作为输入,孤立个体将其自身目前状态与过去状态差作为输入。针对时变时延网络设计控制器,通过构造Lyapunov-Krasovskii函数对系统稳定性进行了证明。设计数值仿真实验,验证了算法的有效性。     

网络稳定性与控制的小增益原理:回顾与近期进展

小增益定理是现代控制理论中极为重要的基本工具之一,它在关联系统和不确定系统的鲁棒稳定性分析以及鲁棒控制器设计的许多工作中都发挥着极大的作用.基于输入到状态稳定性的概念,笔者于1994年首次提出了广义非线性小增益定理.与之前的小增益定理不同,这一结果为同时刻画关联系统的内部稳定性和外部稳定性提供了一个统一的框架.从镇定与鲁棒自适应控制到分散式或分布式控制以及输出调节(抗干扰渐近跟踪),基于非线性小增益定理已经发展出一系列的鲁棒非线性控制器设计新工具.在过去10年间,复杂非线性大系统已成为研究热点,驱动着小增益定理向更加完备的网络小增益定理方向发展,以期解决网络稳定性与控制中的新问题.对此,针对非线性小增益理论的一些最新研究进展及其在通讯和计算约束下的网络化控制和事件驱动控制应用结果进行综述,并对该理论的未来研究方向给出一些建议.     

面向博弈的无线传感器网络自适应路由算法

在无线传感器网络聚簇路由算法基础上,提出了一种面向博弈的自适应路由优化算法.网络中以总体通信能耗最小和延长个体寿命为首要原则,建立源簇到基站的路径;簇首之间相互通信时,在直接、中继以及协作通信方式中,自适应选择路径策略;在路由建立过程中,引入基于博弈论的路由选择算法和路由转发算法,通过两两博弈找出最可靠的下一跳节点,自组织地建立可靠有效的路由路径.仿真实验表明,所提出的路由算法能有效减少通信能耗,延长网络生命周期.     

多无人机完全分布式有限时间编队控制

针对分布式通信网络,研究多无人机完全分布式编队生成和保持控制问题.基于滑模和自适应方法设计自适应耦合增益,进而结合与邻居无人机之间的相对状态设计一种新的有限时间编队控制器.该算法去掉了传统编队控制器依赖通信网络范围和拓扑及Leader无人机状态等全局信息的限制,基于Lyapunov理论证明无人机编队误差在有限时间可以收敛到边界可调的邻域内.对三维运动的多无人机编队进行仿真验证,结果显示,所设计的编队控制算法可以实现多无人机有限时间完全分布式编队生成和保持.     

非连续Lur’e时滞网络的有限时间聚类同步与自适应控制

本文主要研究一类由非恒同非连续Lur’e系统耦合而成复杂动态网络的自适应有限时间聚类同步问题.首先,通过引入Filippov微分包含理论和测度选择定理,本文设计了一类有效的牵制反馈控制器,该控制器只控制当前聚类中与其他聚类有直接连接的部分节点.为了有效节省控制成本,本文基于反馈控制强度设计了一类自适应更新定律以获取实现网络同步的最优控制强度.其次,利用有限时间稳定性理论和Lyapunov稳定性定理,本文得到时变时滞耦合和非线性耦合Lur’e网络实现有限时间聚类同步的判定条件,并给出该网络达到聚类同步的收敛时间估计.最后,通过一个算例仿真验证了本控制方案和同步判据的有效性及正确性.     

Force Reflecting Bilateral Control of Master–Slave Systems in Teleoperation

In this paper, a simple structure design with arbitrary motion/force scaling to control teleoperation systems, with model mismatches is presented. The goal of this paper is to achieve transparency in presence of uncertainties. The master–slave systems are approximated by linear dynamic models with perturbed parameters, which is called the model mismatch. Moreover, the time delay in communication channel with uncertainties is considered. The stability analysis will be considered for two cases: (1) stability under time delay uncertainties and (2) stability under model mismatches. For the first case, two local controllers are designed. The first controller is responsible for tracking the master commands, while the second controller is in charge of force tracking as well as guaranteeing stability of the overall closed-loop system. In the second case, an additional term will be added to the control law to provide robustness to the closed-loop system. Moreover, in this case, the local slave controller guarantees the position tracking and the local master controller guarantees stability of the inner closed-loop system. The advantages of the proposed method are two folds: (1) robust stability of the system against model mismatches is guaranteed and (2) structured system uncertainties are well compensated by applying independent controllers to the master and the slave sites. Simulation results show good performance of the proposed method in motion tracking as well force tracking in presence of model mismatches and time delay uncertainties.     

Preserving stability/performance when facing an unknown time-delay

Embedded controllers executed in real-time are, frequently, subject to a time-varying delay induced by task prioritization or communication over prioritized communication networks. Depending on the microprocessor or network load the delay value may vary. The control design that is based on the worst case assumption with respect to the delay may be very conservative and fail to deliver the adequate performance. On the other hand, the price for not properly dealing with the delay is instability. In this paper some of these issues are discussed in more detail and a control scheme is proposed which combines an unknown input observer to estimate the delayed value of the input, an on-line estimation scheme for the delay and a controller that adjusts its gains as needed to preserve system stability. Some of the aspects of the proposed scheme are discussed and illustrated with simulations on an automotive example.     

Event-triggered controller design of nonlinear discrete-time networked control systems in T-S fuzzy model

This article is concerned with event-triggered fuzzy control design for a class of discrete-time nonlinear networked control systems (NCSs) with time-varying communication delays. Firstly, a more general mixed event-triggering scheme (ETS) is proposed. Secondly, considering the effects of the ETS and communication delays, based on the T-S fuzzy model scheme and time delay system approach, the original nonlinear NCSs is reformulated as a new event-triggered networked T-S fuzzy systems with interval time-varying delays. Sufficient conditions for uniform ultimately bound (UUB) stability are established in terms of linear matrix inequalities (LMIs). In particular, the quantitative relation between the boundness of the stability region and the triggering parameters are studied in detail. Thirdly, a relative ETS is also provided, which can be seen as a special case of the above proposed mixed ETS. As a difference from the preceding results, sufficient conditions on the existence of desired fuzzy controller are derived to ensure the asymptotic stability of the closed-loop system with reduced communication frequency between sensors and controllers. Moreover, a co-design algorithm for simultaneously determining the gain matrices of the fuzzy controller and the triggering parameters is developed. Finally, two illustrative examples are presented to demonstrate the advantage of the proposed ETS and the effectiveness of the controller design method.     

Resource Allocation for Reliable Communication Between Controllers and Switches in SDN

In software-defined networking (SDN), the communication between controllers and switches is very important, for switch can only work by relying on flow tables received from its controller. Therefore, how to ensure the reliability of the communication between controllers and switches is a key problem in SDN. In this paper, we study this problem from two aspects: the controller placement and the resource backup aspect. Firstly, in order to implement the reliable communication and meet the required propagation delay between controllers and switches, a min-cover based controller placement approach is proposed. Then, in order to protect both controllers and control paths from regional failure, a backup method based on an exponential decay failure model is proposed, which considers the regional influence and the survivability of backup controllers and control paths. Simulations show that our controller placement approach can meet the reliability and delay requirement with appropriate controller allocation scheme, and our backup method can improve the survivability of backup controllers and control paths while ensuring the performance of control network.     

Design and Implementation of Robust-Fixed Structure Controller for Telerobotic Systems

The controller design for bilateral teleoperation systems involves a delicate trade-off between performance and stability. To achieve high performance, high order robust controllers may not be feasible for real-time implementation because of hardware and computational limitations. The main purpose of this paper is to achieve stability and transparency in the presence of time delay in communication channel as well as model uncertainty. To address these problems, a novel robust fixed-structure controller is proposed for uncertain bilateral teleoperation systems. Here, the traditional conventional Proportional-Integral-Derivative (PID) controller is employed to achieve the requirements. The simplicity and straightforward design are the significant advantageous of the proposed method. Robust stability analysis of the proposed technique is also provided. Results demonstrate that the structure is effective in providing stability and transparency in teleoperation systems.     

A distributed leader‐following tracking controller using delayed control input information from neighbors

In this paper, we propose a simple, continuous, and distributed controller for the second‐order multiagent system to achieve leader‐following trajectory tracking, by exploiting the control input information of neighbors (CIIN) and using proportional‐derivative (PD) control in terms of local neighborhood synchronization error. A constant time delay is introduced in the CIIN as a design parameter to avoid the algebraic loop issue arising from the control input coupling. We develop an easily testable condition on the PD gains to ensure that the resulting neutral‐type error system is input‐to‐state stable for an arbitrary bounded delay, and prove that when the leader's acceleration is a Lipschitz continuous function with respect to time, the ultimate bound of tracking errors is strictly increasing with respect to the introduced time delay. Moreover, we analyze the robustness of the controller with respect to model uncertainties and show its potential advantages over two existing controllers in balancing the steady‐state tracking precision, the communication cost, and the continuity of controller signal. Finally, extensive simulations are conducted to show the effect of the delay on system stability, to verify the condition on PD gains, to confirm the robustness of the controller, and to demonstrate the detailed advantages.     

A vehicle cloud control system considering communication quantization and stochastic delay

A novel kind of networked feedback controller is designed for the vehicle cloud control system in the presence of both sensor-controller/controller-actuator delay and communication quantization. Firstly, the vehicle cloud control system with delayed and quantized communication is modeled using the lateral/longitudinal vehicle dynamic and Markovian jump linear system (MJLS) theory. Then, some efficient stabilization conditions in matrix inequalities forms are derived for the considered cloud-controlled vehicles. Furthermore, a cone complementary linearization method is utilized to solve the nonlinear matrix inequalities involved in the stabilization conditions. Simulation tests on connected vehicle lateral and longitudinal control are conducted to verify the effectiveness of the analytical results. Compared with the commonly used constant-parameter controllers, the proposed method is practical to design vehicle cloud controllers under stochastic delay and communication quantization scenarios, with known delay distribution. Lastly, the stability of the vehicle cloud control system is guaranteed under the infection of unreliable communication factors with the proposed control method.     

Robust exponential stabilization for network-based switched control systems

It has become a common practice to employ networks in control systems for connecting controllers and sensors/actuators on controlled plants and processes. A network-based switched control system, as a special case of networked control systems, is studied. Such a system is represented with network-induced delays and packet dropout as a switched delay system. Sufficient conditions for robust exponential stability are derived for a class of switching signals with average dwell time. A stabilization design for continuous-time, linear switched plant with nonlinear perturbation under a given communication network via a hybrid state feedback controller is proposed. A hybrid controller design is network-dependent and given in terms of linear matrix inequalities.     

Distributed adaptive attitude synchronization of multiple spacecraft

This paper addresses the distributed attitude synchronization problem of multiple spacecraft with unknown inertia matrices. Two distributed adaptive controllers are proposed for the cases with and without a virtual leader to which a time-varying reference attitude is assigned. The first controller achieves attitude synchronization for a group of spacecraft with a leaderless communication topology having a directed spanning tree. The second controller guarantees that all spacecraft track the reference attitu...     

Distributed adaptive output feedback tracking control for a class of uncertain nonlinear multi-agent systems

This paper addresses the distributed output feedback tracking control problem for multi-agent systems with higher order nonlinear non-strict-feedback dynamics and directed communication graphs. The existing works usually design a distributed consensus controller using all the states of each agent, which are often immeasurable, especially in nonlinear systems. In this paper, based only on the relative output between itself and its neighbours, a distributed adaptive consensus control law is proposed for each agent using the backstepping technique and approximation technique of Fourier series (FS) to solve the output feedback tracking control problem of multi-agent systems. The FS structure is taken not only for tracking the unknown nonlinear dynamics but also the unknown derivatives of virtual controllers in the controller design procedure, which can therefore prevent virtual controllers from containing uncertain terms. The projection algorithm is applied to ensure that the estimated parameters remain in some known bounded sets. Lyapunov stability analysis shows that the proposed control law can guarantee that the output of each agent synchronises to the leader with bounded residual errors and that all the signals in the closed-loop system are uniformly ultimately bounded. Simulation results have verified the performance and feasibility of the proposed distributed adaptive control strategy.