H-infinity control for networked control systems (NCS) with time-varying delays

This paper discusses H-infinity state feedback control for a networked control system with time-varying delays. Based on the flee-weighing matrix method, a dehy-dependent stability criterion satisfying a prescribed H-infinity norm bound is presented for an NCS with unknown, time-varying and bounded delays. And then, the criterion is transformed into sufficient conditions based on linear matrix inequalities for H-infinity control. The conditions thus obtained are also used to design an H-infinity state feedback controller. This design method is further extended to solve the design problem of robust H-infinity state feedback control. A numerical example demonstrates the validity of the method.

D-stability and disturbance attenuation properties fornetworked control systems： switched system approach

Both D-stability and finite L2-gain properties are studiedfor a class of uncertain discrete-time systems with timevaryingnetwork-induced delays. By using coordinate transformand delay partition, the D-stability and H∞ performance problemsfor such networked control systems （NCSs） are equivalentlytransferred into the corresponding problems for switching systemswith arbitrary switching. Then, a sufficient condition for the existenceof the robust D-stabilizing controllers is derived in termsof linear matrix inequality （LMI）, and the design method is alsopresented for the state feedback controllers which guarantee thatall the closed-loop poles remain inside the specified disk D（α,r）and the desired disturbance attenuation level. Finally, an illustrativeexample is given to demonstrate the effectiveness of the proposedresults.

PERFORMANCE ANALYSIS OF USER FAIR-BASED RELAY ADAPTIVE POWER ALLOCATION IN PHYSICAL-LAYER NETWORK CODING COOPERATION

Network Coding (NC) is an effective technology to enhance the cooperative system spectral efficiency. However, since it is network-oriented, the existing performance metric of single-user outage can not comprehensively evaluate its gain and the impact to the entire network, which affect the user fairness. This paper proposes two novel user fair-based adaptive relay power allocation algorithms in single-relay NC cooperative multiple access channels. Firstly, common outage probability is employed as the performance metric, and to minimize it, a specific condition is deduced. On this basis, the instantaneous channel information-based adaptive relay power allocation scheme and the channel statistic information-based one with lower complexity are designed respectively, which make users' signals superimposed at accurately calculated proportion to maintain fairness. Simulation results show that compared with other existing schemes, the proposed schemes can best maintain user fairness, and effectively improve the common outage performance of the whole system, at the expense of small spectral efficiency.

Signal difference-based deadband H_∞ control approach for networked control systems with limited resources

This paper investigates a signal difference-based dead- band H∞ control approach for networked control systems （NCSs） with limited resources. The effects of variable network-induced de- lays, sampling intervals and data transmitting deadbands are con- sidered simultaneously and the model of the NCS is presented. A Lyapunov functional is adopted, which makes full use of the network characteristic information including the bounds of net- work delay （BND）, the bounds of sampling interval （BSI） and the bounds of transmission deadband （BTD）. In the meanwhile, the new H∞ performance analysis and controller design conditions for the NCSs are proposed, which describe the relationship of BND, BSI, BTD and the system＇s performance. Three examples are used to illustrate the advantages of the proposed methods. The results have shown that the proposed method not only effectively reduces the data traffic, but also guarantees the system asymptotically sta- ble and achieves the prescribed H∞ disturbance attenuation level.

Performance analysis of a class of networked control systems under data rate constraints

In networked control system (NCS) where control loop is closed over communication network, limited data rate may deteriorate control performance even destabilize the control system. In this paper, performance analysis of a typical second-order control system with data rate constraints is conducted, and the concept of critical data rate (CDR) is presented. In order to find the CDR in NCS, an approximate searching method is proposed to guarantee acceptable control performance.

Study on the network delay of periodic information in the NCS based on EPA

The network delay of the periodic messages transmission in the network control system （NCS） based on Ethemet for plant automation （EPA） is analyzed from the theoretical and experimental perspective in this paper. The composition and the characteristics of the network delay of EPA periodic messages transmission in a subnet is studied through analyzing the information transmission regularity and EPA deterministic scheduling mechanism. On this basis, the queuing delay at communication schedule management entity （EPA _ CSME） that is the most important component of network delay is analyzed, during which the formulas for the queuing delay of periodic messages and other real time parameters are proposed. Furthermore, an experiment is developed to test each component of network delay of periodic messages transmission in a EPA subnet. According to the experimental and the theoretical analysis, the conclusion is drawn that the delay during which the periodic messages wait for the periodic messages transmission time slice is the main factor that causes considerable network delay, and improvement method is presented.

电力信息物理系统中信息系统物理化的建模及分析方法

该文基于信息系统物理化的设想提出电力信息物理系统(cyber-physical power system,CPPS)中的信息流建模和计算分析方法。采用连续时间函数来刻画信息流的特征,并定义信息网络运行参数为流量累积函数、信息流速和时延。首先,基于遍历法搜索出信息流路径,建立信息流速矩阵的范式;然后利用改进的网络演算(network calculus,NC)特性赋值流速矩阵的元素;进一步采用流量累积函数表征信源数据发送规律,从而显式求解时延上界。最后将提出的信息流建模方法应用于智能变电站自动化系统的时延计算,通过与OPNET的仿真结果相比较,验证所提出模型的有效性,而且该方法可以提供定量分析指标以优化变电站组网方案设计中的信息流分布。

XML在基于STEP-NC网络化制造中的应用

为实现新的数控编程语言STEP-NC在网络化协同制造中的应用,实现网络企业间的产品信息集成和共享,使信息可以在远程、异质、异构环境下进行共享和交流,需要把STEP-NC的描述语言EXPRESS转换为XML语言.分析了EXPRESS语言和XML语言的数据类型及特点,研究了EXPRESS语言和XML语言之间的映射方法,提出了基于XML模式库和DOM接口2种EXPRESS与XML转换方法,最后给出了使用DOM接口方法进行转换的具体实现过程.为企业开展异地产品协同设计、网络化制造提供技术支持.

具有随机时延和丢包补偿的NCS的H_∞控制

给出一个存在随机时延和数据包丢失的网络控制系统(Networked Control System,NCS)模型,并分析了其渐近稳定的LMI条件.为了降低数据包丢失对系统稳定性的影响,在系统中增加了补偿器,并建立了具有丢包补偿器和随机网络诱导时延的NCS模型.在此模型的基础上,给出了系统渐近稳定和γ次优、最优的充分条件,并且获得了系统最优H∞控制的输出反馈控制律.对同一算例进行Matlab仿真,结果表明具有丢包补偿器的NCS趋于稳定的速度更快.

基于Linux的NC操作系统

讨论网络计算机操作系统(NCOS)的一种实现方法,即通过改造Linux的内核代码,从而设计出一个适用于NC的操作系统。

基于改进量子粒子群算法的NCS模糊控制器参数优化

针对网络化控制系统中模糊控制器的量化因子和比例因子采用传统经验方法难以整定的问题,提出了一种改进量子粒子群(IQPSO)算法对模糊控制器量化因子和比例因子进行优化。该方法将ABC算法中的搜索算子作为变异算子引入到QPSO算法中,使得IQPSO算法较好地克服了QPSO算法保持种群多样性差容易早熟收敛的缺陷,并以ITAE指标作为IQPSO算法的适应度函数对模糊控制器进行优化。典型工业过程仿真结果表明,IQPSO优化的模糊控制器具有比PID控制器和标准QPSO优化的模糊控制器更好的控制性能和适用性。

基于DNC的网络制造技术的研究与应用

随着计算机技术、通讯技术和数控技术的发展以及制造自动化的需要,DNC技术得到越来越广泛的应用。目前,以CIMS为代表的企业信息化理念已经受到现代化企业越来越多的重视。DNC也逐渐由单一的程序传输演变为集分布式程序通讯、程序编辑与仿真、数控程序管理等强大功能于一体的综合系统,DNC成为MES等系统的最重要一环。文章讨论了基于DNC的网络制造技术在高校中的研究与应用,分析了基于DNC的网络制造系统的组成及特点,总结了网络制造系统实现的功能和关键技术,并强调了数字化设计与网络制造在先进制造技术中的地位及意义。

基于T-S模型的不确定NNCS鲁棒容错保性能设计

针对一类具有时变时延和丢包的不确定非线性网络化控制系统,基于T-S(Takagi-Sugeno)模糊模型,通过构造适当的Lyapunov-Krasovskii泛函,得出在执行器发生失效故障的情形下,系统基于线性矩阵不等式的渐近稳定且具有良好动态性能的时滞依赖充分条件,并给出了最优鲁棒容错保性能控制器的设计方法。由于证明中没有进行任何模型变换,并考虑了时延下界,使结果具有较少保守性。最后,仿真示例验证了本文所述方法的有效性和可行性。

CIMCO DNC机床联网系统应用与实施

分析了数控设备通信和管理的现状,阐述了CIMCO DNC系统的数据管理方式,详细介绍了基于该系统的数控设备及数控程序管理的解决方案。

面向STEP-NC的网络化制造信息交换与平台设计

目的研究STEP-NC数控程序的描述语言EXPRESS语言和XML之间的转换方法,实现网络化传输,建立基于STEP-NC的网络化制造平台的实现方法.方法以Visual C++为软件开发平台,利用DOM接口和ST-Developer的基础类库ROSE库来实现STEP-NC文件与XML语言之间的转换,采用Windows Socket编程技术实现XML文件在网络上的传输.结果给出了STEP-NC文件与XML语言之间的转换方法,设计了面向STEP-NC的网络化制造信息交换平台的基本框架.结论STEP-NC是新的数控编程接口标准,将STEP-NC与网络化制造相结合,有利于实现网络企业间的产品信息集成,使信息可以在远程、异质、异构环境下进行共享和交换.

长时延NCS的结构特性与建模

研究网络控制系统的关键问题包括两个方面:控制算法和网络结构,其中网络结构决定了系统可靠性和稳定性,系统的实时性也取决于网络结构(包括拓扑结构和协议结构),建立网络结构模型是研究NCS的前提,文章介绍了典型的网络结构和结构抽象化描述方法,并分析了针对长时延的数学模型,该成果对研究NCS有很重要的意义。

基于STEP-NC的网络化制造系统实现框架

为了解决在网络化制造中企业内部与企业间存在着大量异构信息,将STEP-NC与网络化制造相结合,企业内部产品信息统一使用STEP格式。设计了基于STEP-NC的网络化协同制造系统的基本框架,讨论了EXPRESS与XML的映射机制和方法,开发了STEP/XML映射模块,在此基础上结合MAS技术建立多个通过XML语言交换信息的Agent模型。

NCS中数据传输丢包与控制方法

解决数据包丢失是网络传输的一个基本问题,NCS中数据的丢失意味着会对控制系统的稳定性造成影响。本文研究了网络控制系统中单包丢弃和多包丢弃的现象和描述方法,分析了一种实用的补偿与控制方法。本研究可以看作是对NCS延时研究的一个主要补充。在NCS设计和实际使用过程中,正确对待丢包处理有时是提高系统稳定性的一种有效措施。

MSC中基于SDN的拓扑感知RLNC重传方案

为了将小蜂窝中的网络拓扑信息应用于网络编码重传过程,从而有效减少重传次数、提高系统吞吐量,提出了一种移动小蜂窝(mobile small cell,MSC)中基于软件定义网络(software defined network,SDN)的拓扑感知随机线性网络编码(random linear network coding,RLNC)重传方案(topology-aware RLNC retransmission scheme SDN based in MSC,TRRS)。首先,为了收集网络拓扑信息,设计SDN控制器端口设备映射表;其次,依据拓扑信息选择最佳编码包用于重传;最后,通过TRRS算法将网络拓扑信息嵌入编码重传过程。仿真结果表明,相比于现有的SDN与网络编码相结合的协议,TRRS方案减少了重传次数,增加了网络的弹性和吞吐量。

CAXA网络DNC在企业中的应用

传统意义的DNC(直接数字控制)只解决了数控系统存储器容量不足的问题,不能满足现代数控加工车间的集中管理的需求。为适应现代计算机技术发展和现代管理的要求,提出了基于CAXA平台的网络DNC在具体车间的实施方案,对实施效果进行了分析,表明网络DNC技术在企业的应用,提高了企业生产过程的自动化水平。