基于时延预估的网络控制系统研究

针对基于Internet环境下的控制系统中，网络时延、丢包、包序颠倒等问题对闭环实时控制系统性能造成的影响，提出了一种基于时延预估补偿控制的闭环实时控制方法。该方法引入一个网络时延存储队列，对网络时延进行在线预估，通过Smith预估器对控制系统进行动态补偿。同时，利用一类非线性PID的非线性特性对传统PID控制器进行改进，以改善时延随机性对控制系统的影响。仿真结果证明，该方法对模型精确已知的一类控制对象有较好的控制效果。     

基于时延预测模型的网络补偿控制器设计*

针对网络控制系统中随机双向通道时延引起的不确定性问题,提出一种基于时延在线预测模型改进的补偿控制方法。首先,基于自回归模型构建时延预测模型,通过递推最小二乘法实时更新模型参数以预测前向通道时延,并由区间分割法获得高精度的环回时延;然后,设计状态预估器、网络预测器和时延补偿器对环回时延进行补偿,进一步提高系统性能。采用TrueTime工具箱构建网络闭环仿真系统以仿真实际的网络传输情况,同时对PI控制、传统的时延补偿控制以及改进后的时延补偿控制进行对比实验,验证该方法的优越性。     

网络化控制系统的预测控制方法设计

网络化控制系统(NCSs)是一种通过实时化网络进行数据传输的控制系统.控制系统中的传感器、控制器、执行器等往往通过网络连接起来形成闭环控制系统.然而实际系统中由于带宽限制等客观因素,存在有因网络诱导延迟而引起的系统性能下降问题.考虑了前向通道,反馈通道中同时存在网络诱导时延情况下的网络预测控制(NPC)设计问题,提出了一种新的网络预测控制方法,用以克服网络诱导时延对系统性能带来的影响.     

基于ARM的网络远程闭环控制机理研究与实现

针对网络远程控制的研究大部分还只是停留在开环控制或工业专用网络的问题,本文提出了一种基于Internet的远程闭环控制方案,根据该方案设计并实现了一个基于Internet的ARM网络远程控制器和本地控制器,在实验室搭建了网络远程闭环控制物理模拟实验平台,并在该平台上,针对大惯性水位控制对象和网络传输延时的不确定性问题,设计了一种基于在线信息排队的网络延时补偿方法,该方法克服了网络拥塞与不确定性延时对系统的影响,进行了网络远程闭环实时控制实验,得到了较好的控制效果。     

基于群决策考虑属性效用一致性的DEA他评交叉效率公共权重排序法

针对一类主从式异构线性网络化多智能体系统,考虑每个智能体的反馈通道和前向通道中存在随机网络诱导时延和数据包丢失问题,采用预测控制方法,提出一种基于观测器的网络化多智能体协同输出跟踪控制方案.在该方案中,主智能体在每一时刻基于自身滞后输出和系统参考信号,计算一组控制预测序列和输出预测序列,前者用以主动补偿主智能体控制回路中的随机网络诱导时延和数据包丢失,后者被发往从智能体;从智能体在每一时刻基于主智能体发送过来的输出预测序列和自身滞后输出,计算一组控制预测序列,用以主动补偿从智能体控制回路中的随机网络诱导时延和数据包丢失;随后推导闭环网络化多智能体控制系统的稳定性,并通过实验验证该方案的有效性和可行性.     

时戳PI广义预测在网络控制系统中的应用

网络随机时延的存在使得控制系统的性能受到很大的负面影响,甚至引起系统的不稳定,为此提出了基于时戳的PI型广义预测控制算法.在给出了系统环路时延的获取方法的基础上,运用PI型广义预测算法求得系统的未来信息,并将此信息发送到执行器,在执行器端给出了网络补偿器的设计.之后对控制系统的稳定性进行了分析,得到了闭环网络控制系统稳定的条件.最后利用TrueTime工具箱进行仿真研究,验证了该算法的有效性.     

网络控制系统补偿器设计及稳定性分析

为解决网络延时对网络化控制系统性能的影响, 从控制的角度提出基于系统模型的补偿器设计方案以解决网络延时问题. 通过对广义预测控制算法GPC状态空间形式的推导, 设计具有多步预测功能的网络控制器, 实现前向通道的延时补偿; 构造具有延时补偿功能的状态观测器以补偿反馈通道延时. 分析了使用上述延时补偿策略所构成的闭环网络控制系统的稳定性. 通过对不同网络延时补偿的仿真实验, 证实了该补偿算法能有效改善控制系统性能并保持系统的稳定.     

一类具有随机时延的网络化控制系统的广义预测控制

网络化控制系统中,各种恒定、时变或者随机的网络时延会导致系统控制性能的下降甚至不稳定。针对基于交换式以太网所造成的随机网络时延问题,结合对系统结构及时延特征的分析,给出了一种基于广义预测控制的控制方法,该方法采用网络时间戳机制和模型的在线辨识,能够准确地测量系统输出并及时对预测值进行在线修正,实现对随机时延的网络化控制系统的有效控制。最后通过仿真验证了该方法的有效性。     

具有随机长时延的网络控制系统保性能控制

本文研究了一类具有随机长时延离散时间网络控制系统(NCSs)的建模和保性能控制问题.用两个马尔可夫链分别来描述反馈通道和前向通道的网络诱导时延,基于采用现有最新数据的原则,将闭环NCS建模成一个与当前时刻和过去时刻网络诱导时延有关的马尔可夫随机时滞系统.应用线性矩阵不等式技术和李亚普诺夫方法得到了闭环NCS随机稳定且具有二次性能指标上界的充分条件,并给出了状态反馈保性能控制器的设计方法.最后,通过数值算例验证了本文方法的有效性.     

基于T-S模型的网络控制系统故障诊断

针对一类参数不确定并具有时延和丢包情况的非线性网络控制系统,为达到快速准确的进行故障诊断的目的,提出了一种基于T-S模糊模型的故障诊断方法.通过建立此系统的T-S模糊模型,利用平行分布补偿时延的思想设计了满足系统稳定性条件的状态反馈控制器,以及通过引入随机切换系统表示数据有无丢失情况下的基于模糊观测器的鲁棒故障诊断方法,然后基于 Lyapunov函数和线性矩阵不等式方法给出了该闭环网络控制系统渐近稳定的充分条件,最后通过仿真例子验证了该方法能够使闭环控制系统渐进稳定以及能够准确的进行故障诊断,验证了所设计方法的有效性.     

虚拟仿真技术在网络闭环控制中的应用

Internet上数据传输的不确定延时妨碍了远程被控对象和操作者之间迅捷而透明的交互,严重限制了网络远程控制系统的性能和应用。为了解决网络延时问题,提出一种基于虚拟仿真的网络三闭环控制结构。该方法依照开环系统实现闭环控制的思想,在客户端构造虚拟被控对象模型,使虚拟仿真系统与实际系统的运行状态相似甚至相同,同时又使操作者能依据虚拟仿真系统一端的运行情况决定下一步的控制指令,从而准确地对实际系统发出所需的控制指令,最终达到远程实时控制的目的。仿真结果证明了所提方法的有效性和可行性。     

无源散射变换的双边移动机器人网络遥操作

网络遥操作系统的随机时延给控制器设计带来巨大挑战,严重时破坏系统的稳定性。首先对遥操作无源理论及其波变量控制方法做了简单综述,然后提出直接无源散射变换方法,它将无源双边控制方法推广到具有随机时延的网络遥操作系统中去,保证网络遥操作系统在任何不对称随机网络时延情况下稳定。最后基于此变换方法设计了一个虚拟主从手双边移动机器人网络遥操作方案,并进行了仿真验证,结果表明结出的设计方法能满足系统性能要求。     

A new networked predictive control approach for systems with random network delay in the forward channel

This article is concerned with the design of a networked predictive control (NPC) scheme with random network delay in the forward channel. A new design method of NPC is proposed. Correspondingly, the necessary and sufficient conditions on the stability of the closed-loop networked control system are derived. The merit of the proposed design method lies in its decreased conservativeness, which is achieved by packing the current predictive control signal with history predictive signals. By this means, the future plant input is known. Therefore, the state predictor can be designed such that its performance and stability will not be affected by the future input of the plant, while the existing design methods of NPC cannot do so. The proposed design method is shown to be much less conservative than the existing result through several examples.     

H ∞ predictive control of networked control systems

This article is concerned with the problem of H _∞ predictive control of networked control system with random network delay. A new control scheme termed networked predictive control is proposed. This scheme mainly consists of the control prediction generator and network delay compensator. While designing the predictor, the control input to the actuator may be different due to networked induced time-delay and data dropout, and two cases are considered depending on the way that the observer obtains the plant control input u _t . The necessary and sufficient conditions are given for the closed-loop networked predictive control system to be stochastically stable for different u _t and random network delays in controller to actuator channel (CAC) and sensor to controller channel (SCC). A simulation study shows the effectiveness of the proposed scheme.     

Observer-based controller design for networked control systems with sensor quantisation and random communication delay

This article addresses the study of observer-based controller design for network-based control systems in the presence of output quantisation and random communication delay simultaneously. In the communication channel, the output measurement are quantised before transmission, and two kinds of network-induced delays are taken into account simultaneously: (i) random delay from sensor to controller and (ii) random delay from controller to actuator. These two types of random delays are modelled as two independent Bernoulli distributed white sequences. The observer-based controller is synthesised to stabilise the networked closed-loop system in the sense of stochastic stability. Sufficient conditions for the existence of the controller are provided by stochastic Lyapunov method. An illustrative numerical example is employed to demonstrate the applicability and flexibility of the proposed design strategy.     

Robust stability analysis of Smith predictor-based congestion control algorithms for computer networks

Congestion control is a fundamental building block in packet switching networks such as the Internet due to the fact that communication resources are shared. It has been shown that the plant dynamics is essentially made up of an integrator plus time delay and that a proportional controller plus a Smith predictor defines a simple and effective controller. It has also been shown that the TCP congestion control can be modelled using a Smith predictor plus a proportional controller. Due to the importance of this control structure in the field of data network congestion control, we analyse the robust stability of the closed-loop system in the face of delay uncertainties that are present in data networks due to queuing. In particular, by applying a geometric approach, we derive a bound on the proportional controller gain which is necessary and sufficient to guarantee the closed-loop stability for a given bound on the delay uncertainty.     

基于网络模型的综合多速率采样预测控制器

针对网络控制系统(NCS)中存在的网络延迟和数据丢包问题以及网络控制系统的多采样率特性,将预测控制器和网络延迟补偿器相结合,提出一种基于网络模型的综合多速率采样预测控制器.预测控制器利用多步预测、滚动优化、反馈校正控制策略补偿了传感器-控制器传输延迟,网络延迟补偿器补偿了控制器-执行器传输时延和一些未知网络延迟.仿真试验表明,该算法对网络延迟和数据丢包具有一定的补偿作用,提高了网络资源利用率并且保证闭环网络控制系统渐近稳定.     

Stable Queue Management in communication networks

Since Active Queue Management (AQM) was recommended by the Internet Engineering Task Force (IETF) as an efficient way to overcome performance limitations of Transmission Control Protocol (TCP), several studies have proven control theory to be a promising field for the design and analysis of congestion control in homogenous communication networks. AQM is gaining increased importance due to reports of buffer-induced latencies throughout the Internet. The increasing volume and diversity of traffic types (i.e., data, voice, and video) suggests that traffic management mechanisms, in general, and AQM schemes, specifically, must not only focus on the critical issue of congestion control but must also consider the QoS demands of heterogeneous traffic. However, to combine quality-of-service provisioning with congestion control, AQM design needs to be reconsidered. In this paper, we propose a state feedback controller design scheme for heterogeneous networks preserving the closed-loop system stability. Delay dependant stability conditions of the closed loop system are derived based on the Lyapunov-Krasovskii method. The proposed approach offers flexible choice of control parameters allowing the network administrator to control fairness and response time for each individual source node in a network of multiple links with different delay properties. The performance and robustness of the proposed controller were illustrated and analyzed using event-based computer simulations.     

具有时变时滞和多包丢失的网络控制系统量化H∞控制

研究了具有时变时滞与多数据包丢失的网络控制系统(networked control systems,NCSs)的量化H∞控制问题.同时考虑传感器-控制器间的测量通道及控制器-执行器间的控制通道的多数据包丢失,并将其用满足Bernoulli分布的随机变量来表示.控制输入信号和测量输出信号分别在传感器和控制器两侧进行对数量化,量化误差描述为扇区有界不确定性.利用Lyapunov理论和线性矩阵不等式方法,得到了使得闭环NCSs满足一定H∞性能指标的均方意义下指数稳定充分条件,并给出了基于观测器的时滞相关控制器设计方法.最后,通过实例证明了该方法的有效性.