Stability of networked control systems with multi-step delay based on time-division algorithm

1IntroductionFeedback control systems in which the control loops areclosed through a real_time network are called networkedcontrol systems(NCS)[1,2].Conventional controltheories should be reevaluated before they are applied toNCS because of the existence of sensor_to_controller delayτscand controller_to_actuator delayτca.They may degradethe performance of control systemand even destabilize thesystem.There are two kinds of design methods for NCS:deterministic design methods and stochastic…     

一类网络化串级控制系统的分析与建模

针对基于现场总线的一类网络化串级控制系统,分析了其结构及系统模型,指出了网络诱导时延存在的位置,主控制器和副控制器均采用了增量式数字PID;在网络诱导时延常数小于、大于一个采样周期以及等于采样周期的整数倍的情况下,分别利用增广状态向量法,将系统建模为有限维离散时间线性时不变系统。最后,给出了网络化串级控制系统(NCCS)在不同时延的仿真实例。     

Modelling and control of Zigbee-based wireless networked control system with both network-induced delay and packet dropout

A new stochastic switched linear model is established to describe the Zigbee-based wireless networked control system (WNCS) with both network-induced delay and packet dropout. The network-induced delay can be less or longer than one sampling period. A sufficient condition is presented for the exponentially mean square stability of the closed-loop WNCS, and corresponding state feedback controller is designed by using the augmenting technique and multi-Lyapunov approach. Then, combined with carrier sense multiple access with collision avoidance (CSMA-CA) algorithm, a method is given to choose proper parameter values. Finally, a numerical example is provided to demonstrate the effectiveness of the proposed method.     

多包传输网络控制系统的对象建模

由于将通讯网络的引入,不可避免地引起传输延时。网络传输延时的存在使网络控制系统的分析和设计更加复杂和困难,尤其是多包传输的网络控制系统。在分析网络多包传输原因的基础上,研究了多包传输网络控制系统的对象建模。系统中传感器采用时间驱动的方式,控制器和执行器采用事件驱动的方式。在考虑系统噪声和网络诱导延时大于一个采样周期的情况下,给出了多包传输的网络控制系统模型。此模型可以用来分析系统的性能。     

Modelling and robust stability of networked control systems with packet reordering and long delay

In this article, modelling and robust stability of networked control systems (NCS) are discussed. Considering the existence of packet reordering and network-induced delay, a new mathematical model of NCS whose network-induced delay is longer than one sampling period is obtained, which can fully describe packet reordering and effectively eliminate the impact of packet reordering on the performance of NCS such that the newest control input can be executed by the actuator. Based on this model, the time-varying NCS is converted into an uncertain discrete linear system with multi-step delay in terms of matrix theory. Furthermore, a sufficient condition for robust stability of NCS is presented. Linear matrix inequality approach has been employed to solve the controller design problems. Numerical examples are compared with previous schemes to demonstrate the effectiveness of the proposed method.     

具有时延和数据包丢失的动车组网络控制系统建模方法研究

提出了一种具有时延和数据包丢失的动车组网络控制系统(NCSs)建模方法。假设网络时延小于采样周期,数据包传输成功率是固定的。动车组网络控制系统可以被描述为一个事件驱动的异步动态系统,使用动态输出反馈控制方法,讨论了闭环网络控制系统的稳定性。     

A robust control approach to stabilization of networked control systems with time-varying delays

The stabilization problem is studied for networked control systems (NCSs) with time-varying delay that may be larger than one sampling period. By considering state feedback controllers, the closed-loop NCS is described as a switched delay system, which is then represented as an interconnected feedback system. A sufficient BIBO stability condition is derived for the closed-loop NCS by using the small gain theorem and the average dwell time technique. Design procedures for the BIBO stabilizing controllers are also presented. An example is given to demonstrate the effectiveness of the proposed method.     

基于延时预测的模型状态反馈网络控制方法

网络延时的存在不仅会使控制系统的动、静态性能变差,还可能会破坏系统的稳定性,造成既有控制方法的失效。针对带有随机延时的网络控制系统,提出了一种基于网络延时实时预测和系统状态逼近的控制方法。首先,建立无延时的理想控制系统模型作为标准控制系统模型;其次,应用基于隐马尔可夫模型(HMMs)的延时预测算法预测网络延时,该方法能够实时自适应学习,以适应网络负载情况的变化,得到更符合实际情况的延时预测值;最后,根据网络延时的预测值、实际网络控制系统与标准控制系统模型的状态之差,来调整控制信号,从而使实际网络控制系统的状态与标准控制系统模型接近、甚至相等,达到期望的控制效果。数字仿真结果表明,这一方法是可行的,能够获得更加快速的动态性能和稳定的静态性能。     

自适应Smith补偿器在基于IP的网络控制系统中的应用

在基于IP网络的网络控制系统(NCS s)中,网络诱导时延变化显著且往往大于一个采样周期.本文引用数据通信中应用广泛的网络回程时间来估计NCS s中时变的全回路网络诱导时延,并提出了一种新的自适应Sm ith补偿器.仿真结果表明,该补偿器能够有效地消除网络诱导时延变化对控制性能的负面影响;结合该自适应Sm ith补偿器所设计的控制系统能够获得很好的控制性能与较强的鲁棒性.     

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.     

一个提高网络化控制系统性能的算法研究

针对网络诱发延迟大于一个采样周期的网络化控制系统,文章提出了一种新的控制模式,为实现这种控制模式和系统的数学建模,给出了一个分时算法,仿真结果验证了算法的有效性。     

MIMO网络控制系统的建模与分析

针对网络只存在于传感器节点与控制器节点之间的多输入多输出(MIMO)网络控制系统,研究了系统建模和稳定性问题.设传感器节点和控制器节点均为时间驱动,且它们的采样存在着固定的时间差,网络诱导时延的上界大于一个采样周期,建立了此类网络控制系统的模型.基于Lyapunov函数和线性矩阵不等式(LMIs)方法,给出了闭环系统渐近稳定的充分条件.仿真表明本文的方法是有效的.     

Modelling and control of networked control systems with both network-induced delay and packet-dropout

A new switched linear system model is proposed to describe the networked control system (NCS) with both network-induced delay and packet-dropout. A sufficient condition is derived for the exponential stability of the closed-loop NCS, and the obtained condition establishes the quantitative relation between the packet-dropout rate and the stability of the NCS. Design procedures for the state feedback stabilising controllers are also presented by using the augmenting technique. An illustrative example is provided to demonstrate the effectiveness of the proposed method.     

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.     

网络控制系统时变采样周期的建模与切换控制*

针对具有双边随机时延和丢包的网络控制系统,首先采用了主动时变采样周期的方法,利用事件和时间驱动相结合方式,传感器的采样周期可实时地跟随网络延时和丢包的变化而改变,克服了长时延和数据包错序的问题。然后将系统建立为统一的切换系统模型,结合基于平均驻留时间的方法,给出了系统状态满足指数稳定的条件,并且描述了其指数衰减率和丢包率之间的定量关系。最后通过数值例仿真验证了本文所提方法的有效性。     

Output feedback guaranteed cost control of networked linear systems with random packet losses

This article is concerned with the output feedback guaranteed cost control problem for a class of networked control systems (NCSs) with both packet losses and network-induced delays. The packet-loss processes in the forward channel and the backward channel are modelled as two Markov chains. The dynamic output feedback controllers are considered, and the closed-loop NCS is modelled as a discrete-time Markovian system with two modes and unit time delay. By using a properly constructed Lyapunov function and the state transformation technique, a sufficient condition is derived for the closed-loop NCS to be mean-square exponentially stable and ensure a decay rate that can be tuned according to the packet loss situations in the networks. Moreover, design procedures for the guaranteed cost controllers are also presented based on the obtained stability condition and guaranteed cost performance result. Finally, an illustrative example is given to demonstrate the effectiveness of the proposed results.     

Fault detection of NCS based on eigendecomposition,adaptive evaluation and adaptive threshold

A method for fault detection (FD) of networked control systems with unknown network-induced delay and unknown input based on eigendecomposition, adaptive evaluation and adaptive threshold is proposed in this paper. In the method, a known structure matrix of network-induced delay which is supposed to be smaller than one sampling period is extracted by eigendecomposition and an observer based residual generator is constructed. Then an adaptive evaluation function is proposed to ensure the optimal robustness to network-induced delay and unknown input at the evaluation stage based on the Parity Space approach. Finally, based on the estimation of the maximal influence of unknown random delay and unknown input on the evaluation function, adaptive threshold is designed to enhance robustness of the FD system and reduce the miss detection rate as much as possible.     

模糊逻辑补偿的网络PI控制系统及稳定性分析

针对现代工业过程中常用的网络PI控制系统, 分析了网络所诱导的时滞对PI控制系统性能的影响, 设计了一个模糊逻辑补偿器来实现对网络所诱导的时滞的补偿. 利用Hermite-Biehler引理在准多项式稳定性问题上的推广, 研究了具有模糊逻辑补偿的网络PI控制系统的稳定性问题, 给出了使闭环系统稳定的模糊逻辑调节参数的取值范围. 仿真结果验证了理论分析结果的有效性.     

一种基于最优鲁棒故障检测滤波器的网络化控制系统故障检测方法

研究了时延可能大于采样周期情况下的网络化控制系统的故障检测问题. 首先, 时延造成的影响被转化成了范数有界的不确定性, 接下来现有的基于参考模型的连续系统故障检测方法被推广到离散系统, 并应用于前面得到的含参数有界不确定性的系统. 本文提出的算法可以通过 Matlab LMI 工具箱实现. 仿真结果证实了算法的有效性.     

具有短时延的网络控制系统的一种鲁棒控制方法

针对具有短时延的网络控制系统, 本文提出了一种基于鲁棒控制的方法来解决该类系统的稳定化控制问题. 考虑状态反馈控制律, 将闭环网络控制系统描述为一个离散时间线性不确定系统模型, 其中的不确定部分反映了时延的时变特性对系统动态的影响. 得到了该闭环网络控制系统的渐近稳定性条件, 且该条件建立了闭环网络控制系统稳定性与两个时延参数, 即允许时延上界和允许时延变换范围, 之间的定量关系. 进一步的, 还给出了稳定化反馈控制器的设计步骤. 最后通过一个示例验证了本文所提出方法的有效性.