Fault detection for discrete-time networked nonlinear systems with incomplete measurements

This article addresses the problem of fault detection (FD) for discrete-time networked systems with global Lipschitz nonlinearities and incomplete measurements, including time delays, packet dropouts and signal quantisation. By utilising a discrete-time homogeneous Markov chain, an improved model which considers packet dropout compensation has been proposed to describe the above network-induced phenomena. We aim to design a mode-dependent fault detection filter (FDF) such that the FD system is asymptotically mean-square stable and satisfies a prescribed attenuation level. The addressed FD problem is then converted into an auxiliary H _∞ filtering problem of Markov jump system with time-varying delay. A sufficient condition for the existence of the FDF is derived in terms of certain linear matrix inequalities (LMIs). When these LMIs are feasible, the explicit expression of the desired FDF can also be characterised. A numerical example is exploited to show the effectiveness of the results obtained.     

Optimal regulation performance of discrete time-delay systems based on quantization and input energy constraints

In this paper, we study the optimal regulation problem of networked control systems and propose a new performance index for a given discrete time-delay system. The regulation performance of the controlled plant is investigated by considering the effects of various constraints on the communication channel such as quantization, bandwidth, and packet dropouts using frequency domain methods and two-degree-of-freedom control techniques. The results show that the regulation performance is not only related to the location and direction of the non-minimum phase zeros and unstable poles of a given system but also related to the internal time delay of the controlled plant. Packet dropouts, quantization, and bandwidth limitations can also negatively affect the optimal performance. In addition, the trade-off of the input energy constraint can also make the optimal regulation performance suffer. Finally, the reliability of this innovative result is illustrated by some simulation examples.     

网络化系统周期信号的跟踪

研究线性时不变、单变量、离散网络化系统对周期信号的跟踪问题.与现有文献考虑的参考输入信号大都为常见的能量信号所不同的是,本文参考输入信号是离散时间周期方波功率信号.相应地,研究系统对基于功率谱的参考输入信号功率的响应,系统的跟踪性能通过输入信号与受控对象输出之差的功率来衡量,而最优跟踪性能采用跟踪误差的平均功率来度量.考虑的网络化控制系统仅上行通道存在丢包误差的影响,把丢包过程看作两个信号的合成,一是确定性信号,二是随机过程,进而丢包误差描述为源信号和白噪声之间乘积.根据被控对象和随机过程的性质,采用Parseval等式、维纳–辛钦定理和范数矩阵理论得到该系统跟踪性能极限的下界表达式.仿真结果表明,所设计的控制器能实现对周期信号的有效跟踪,进而验证了结论的正确性.     

多通道网络化系统跟踪性能极限

本文基于白噪声和编码影响研究多通道网络化系统跟踪性能极限.网络化系统的跟踪性能指标是通过跟踪误差的能量来定义的,采用谱分解技术和范数矩阵理论得到多通道网络化系统跟踪性能极限的下界表达式.研究结果显示了对象的固有特性(非最小相位零点、零点方向、不稳定极点和极点方向)和多通道的编码器及白噪声决定网络化系统跟踪性能极限;同时也说明了多通道网络是如何影响系统跟踪性能极限.仿真结果验证了该结论的正确性.     

Sliding mode stabilisation of networked systems with consecutive data packet dropouts using only accessible information

This paper develops a novel stabilising sliding mode for systems involving uncertainties as well as measurement data packet dropouts. In contrast to the existing literature that designs the switching function by using unavailable system states, a novel linear sliding function is constructed by employing only the available communicated system states for the systems involving measurement packet losses. This also equips us with the possibility to build a novel switching component for discrete-time sliding mode control (DSMC) by using only available system states. Finally, using a numerical example, we evaluate the performance of the designed DSMC for networked systems.     

编解码和时延约束下的网络化控制系统最优跟踪性能

本文研究了具有丢包、时延、编解码等通信资源受限下多输入多输出离散时间网络控制系统的最优跟踪性能. 基于频域方法, 采用二元随机过程来模拟数据包丢失, 并假设信道噪声是加性高斯白噪声(AWGN), 推导了在丢包、信道噪声、时延和编解码影响下的跟踪性能极限. 采用单参数补偿器(SDOF), 利用互质分解、Youla参数化等工具得到了编解码和时延约束下的网络控制系统最优跟踪性能的显式表达式. 结果表明, 跟踪性能与对象的固有特性(非最小相位零点与不稳定极点的位置和方向)、时延、丢包率和AWGN 功率谱密度密切相关.     

Optimal tracking performance of communication-constrained systems under energy constraints

This paper investigates the optimal tracking performance of systems by considering packet dropouts, additive white Gaussian noise(AWGN), and coding under energy constraints. The optimal tracking performance of communication-constrained systems is obtained by spectral decomposition and partial factorization. The results show that the optimal tracking performance of the system is related to intrinsic properties such as non-minimum phase zeros and unstable poles. What's more, encoding, data loss rate, and AWGN are also able to affect the performance of the system. Finally, the correctness of the results is verified by specific examples.     

不确定时延输出反馈网络化系统保性能控制

研究了一类具有不确定时延的动态输出反馈网络控制系统的保性能控制问题．针对小于等于一个采样周期的不确定时延,利用Lyapunov理论和线性矩阵不等式方法,推导出了动态输出反馈网络控制系统保性能控制律存在的条件,给出了动态输出反馈保性能控制律设计方法．利用LMI工具箱中的目标函数最小化工具,可以求得该类系统优化的保性能控制律参数和优化的性能指标,从而获得该系统的保性能控制律．给出的仿真算例说明了设计方法是有效的所得结果是可行的．     

基于局部交叠异步切换的网络控制系统故障检测

针对存在时变短时延和丢包的网络控制系统故障检测问题,将非线性对象建模为线性切换系统.考虑工程中存在的局部交叠切换律,将切换系统划分为若干局部交叠切换于系统.同时,考虑滤波器切换滞后引起的异步切换问题,进一步将系统增广为局部交叠异步切换系统.在此基础上,结合公共Lyapunov函数和平均驻留时间方法,以LMI形式给出检测滤波器设计方法.最后,通过某网络化飞行器的全包线飞行验证了所提出方法的有效性.     

具有数据包丢失的网络控制系统保性能控制

本文研究了一类具有数据包丢失的网络控制系统(NCSs)的建模和保性能控制问题.通过用两个马尔可夫链分别来描述前向通道和反馈通道的丢包过程,将闭环网络控制系统建模成具有两个模式的马尔可夫随机切换系统.基于线性矩阵不等式技术和李亚普诺夫方法得到了闭环系统随机稳定的充分条件,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本文结果的有效性.     

具有时延和数据包丢失的网络控制系统稳定性

针对单数据包传输情况,将同时存在网络诱导时延和数据包丢失的网络控制系统建模为具有事件约束的异步动态系统,依据Lyapunov稳定性原理,提出了同时存在网络诱导时延和数据包丢失的网络控制系统指数稳定的网络诱导时延条件和数据包丢失条件,对条件进行了实例仿真验证,仿真结果表明该条件是有效的.     

有时延和丢包的网络控制系统的补偿策略

由于网络控制系统中网络诱导时延和数据包丢失等问题的存在,使得网络控制系统控制性能下降甚至导致系统地不稳定。同时在实际应用中,一些系统的状态是不可测量的。针对上述问题,设计了状态观测器,利用测量输出进行了状态重构,并利用状态观测器对丢包进行了补偿。最后应用指数稳定定理分析了整个系统的闭环稳定性,给出了状态控制率的求解方法,并对一直流电机进行了仿真,仿真实验结果表明,该方法能有效地补偿网络控制系统的性能,保证了在时延和有数据包丢失的情况下网络控制系统的稳定性。     

Necessary and sufficient optimal control conditions for networked control systems with input delay and Markovian packet dropouts

This article studies the optimal control for networked control systems (NCSs) subject to Markovian packet dropouts and input delay. In this scenario, Markovian packet dropouts occur in two channels, that is, from sensor to controller and from controller to actuator. Meanwhile, the input delay arises in the channel from controller to actuator. The contributions of this paper are as the following two aspects: Firstly, based on Pontryagin's maximum principle, the solution to the forward and backward stochastic difference equations (FBSDEs) is obtained. Secondly, in virtue of the obtained solution to the FBSDEs, sufficient and necessary optimal control conditions are derived and the explicit expression of the optimal controller is presented. The validity of the results is illustrated by numerical examples.     

具有长时延和丢包的网络控制系统的故障检测

针对同时具有网络诱导时延和数据包丢失的异步时钟网络控制系统,假设数据包丢失率一定,网络诱导时延大于一个采样周期,根据执行器接收数据包的情况,设计了系统的故障观测器,将其建模为具有事件率约束的异步动态系统,基于该模型进行了稳定性分析,当条件满足时,整个系统是指数稳定的。在此基础上研究了系统的故障检测,当系统发生故障时,观测器残差能够迅速发生跳变,从而检测出故障的发生。仿真示例验证了所提出方法的有效性。     

具有时变采样周期网络控制系统的严格耗散控制

研究具有时变采样周期和数据丢包的网络控制系统的渐近稳定和严格耗散控制问题.针对采样周期时变且在标称周期上下波动,数据丢包数有界,利用参数不确定的方法,网络控制系统建模为一类带有参数不确定的离散时滞系统.构造一个改进的李雅普诺夫-卡拉索夫斯基函数,基于线性矩阵不等式方法及Jensen不等式方法,给出系统严格(Q,S,R)-耗散的充分条件,得到控制器的设计方法.数值实例表明所提出的方法具有较小的保守性,同时也减少了计算量.     

Observer-based H-infinity control in multiple channel networked control systems with random packet dropouts

This paper investigates the observer-based $H_{\infty}$ control problem for networked control systems (NCSs) with random packet dropouts. A general packet dropout model with multiple independent stochastic variables in multiple channels case is adopted to describe the data missing in the limited communication channels. With the consideration of the sensor-to-controller and controller-to-actuator packet dropouts at the same time, a new method is proposed based on a separation lemma to design an observer-based $H_{\infty}$ controller, which exponentially stabilizes the closed-loop system in the sense of mean square and also achieves a prescribed $H_{\infty}$ disturbance attenuation level. A numerical example is given to illustrate the effectiveness of the proposed control method.     

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.     

时延网络控制系统的稳定性

针对网络控制系统中存在的不确定时延 ,首先讨论了系统的建模问题 .系统中传感器采用时间驱动 ,执行器与控制器采用事件驱动 ,传感器的数据采用单包传输 .假设传输时延小于采样周期 ,网络控制系统可以建模为一类具有不确定性的线性离散时延系统 .利用Lyapunov方法 ,给出了闭环系统渐近稳定的充分条件 ,基于相应的线性矩阵不等式可行解 ,可以求解状态反馈控制律 .最后 ,用仿真例子验证了该方法的有效性     

Predictive control for networked systems affected by correlated packet loss

In this paper, we consider the predictive control problem of designing receding horizon controllers for networked linear systems subject to random packet loss in the controller to actuator link. The packet dropouts are temporarily correlated in the sense that they obey a Markovian transition model. Our design task is to solve the optimal controller that minimizes a given receding horizon cost function, using the available packet loss history. Due to the correlated nature of the packet loss, standard linear quadratic regulator methods do not apply. We first present the optimal control law by considering the correlations. This controller turns out to depend on the packet loss history and would typically require a large lookup table for implementation when the Markovian order is high. To address this issue, we present and compare several suboptimal design approaches to reduce the number of control laws.     

Analysis and design of networked control systems using the additive noise model methodology

Networked Control has emerged in recent years as a new and exciting area in systems science. The topic has many potential applications in diverse areas ranging from control of microrobots to biological and economic systems. The supporting theory is very rich and combines aspects of control, signal processing, telecommunications, and information theory. In this paper, we give a partial overview of recent developments in Networked Control with an emphasis on the additive noise model methodology. We also point to several open problems in this emerging area. Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society