利用自适应编码调制的无线网络控制系统的分析和设计

研究了利用自适应编码调制的无线网络控制系统的分析和设计, 自适应编码机制引入无线网络能够提高衰退信道的能量效率, 增加数据传输率. 进一步, 通过等价时延的概念来描述无线传输信道中的时变速率, 干扰和路由特性. 基于时变的网络条件给出了等价时延的上下界. 无线网络控制系统被建模为具有时变输入时延的离散系统. 通过新的时滞系统技术给出了该闭环无线网络控制系统可稳定化的充分条件. 最后, 数值算例表明了所提控制策略的有效性.     

无线网络环境下移动机器人轨迹跟踪的认知控制分析与设计

现有的网络控制系统领域中的研究通常先对网络环境的时延和丢包特性进行理想性假设, 然后设计对应 的控制算法. 然而, 由于无线网络环境具有复杂的时延和丢包特性, 这些假设在无线网络控制系统(WNCS)运行过 程中很难得到满足. 为了在不对网络环境的时延和丢包特性进行理想性假设的前提下设计控制系统, 本文受认知 控制思想的启发, 在控制系统中加入了认知控制器. 认知控制器在感知–作用循环中学习产生认知作用的策略, 调 节无线网络的媒体接入控制(MAC)层的重传次数上限和物理控制器的命令序列长度, 使控制系统可以主动地适应 所处的无线网络环境. 本文以全向轮移动机器人为被控对象, 对使用认知控制器的WNCS和使用固定配置的WNCS 的仿真结果进行比较. 仿真结果表明使用认知控制器调节MAC层的重传次数上限和物理控制器的命令序列长度, 可以提高WNCS对网络环境的时延和丢包的承受能力.     

Optimal controller location in wireless networked control systems

The control performance of wireless networked control systems (WNCS) has been shown to heavily depend on the packet delivery quality of both the sensor‐to‐controller and controller‐to‐actuator communications. Such quality relies on the relative distance between the wireless transmitter and receiver, which naturally raises the challenging problem of controller placement in WNCS for optimal control performance. In this paper, we investigate the optimal controller location (OCL) problem in WNCS based on linear‐quadratic‐Gaussian control strategy. For the one‐hop network case where the controller can only be placed at either the sensor side or the actuator side, we derive a simple yet effective criterion to determine the OCL. For the more general multi‐hop case where the controller can be located at either one of the sensors, relays, or actuators, we obtain the necessary and sufficient condition under which the closed‐loop system is guaranteed to be stable. On the basis of these results, we further transform the OCL problem into an optimization problem that can be solved efficiently. Numerical results are provided to verify our analysis. Copyright © 2013 John Wiley & Sons, Ltd.     

Resilient control for wireless networked control systems under DoS attack via a hierarchical game

In this paper, the resilient control problem is investigated for a wireless networked control system (WNCS) under denial‐of‐service (DoS) attack via a hierarchical game approach. In the presence of a wireless network, a DoS attacker leads to extra packet dropout in the cyber layer of WNCS by launching interference power. A zero‐sum Markov game is exploited to model the interaction between the transmitter and the DoS attacker under dynamic network environment. Additionally, with the attack‐induced packet loss, an H_∞ minimax controller is designed in the physical layer by using a delta operator approach. Both value iteration and Q‐learning methods are used to solve the hierarchical game problem for the WNCS. The proposed method is applied to a load frequency control system to illustrate the effectiveness.     

Modeling and control for wireless networked control system

In this paper, the stabilization problem is considered for the class of wireless networked control systems (WNCS). An indicator is introduced in the WNCS model. The packet drop sequences in the indicator are represented as states of a Markov chain. A new discrete Markov switching system model integrating 802.11 protocol and new scheduling approach for wireless networks with control systems are constructed. The variable controller can be obtained easily by solving the linear matrix inequality (LMI) with the use of the Matlab toolbox. Both the known and unknown dropout probabilities are considered. Finally, a simulation is given to show the feasibility of the proposed method.     

无线网络化系统自适应能量调度与协同控制

无线网络化系统（wireless networked control system,WNCS）中节点能量受限是影响系统性能的重要因素．本文提出了一种自适应能量调度方法解决节点能量与控制需求问的矛盾,在采样周期与能量消耗之间关系的基础上,利用动态采样周期实现能耗的实时调节,满足节点生存时间的需求．进而,将自适应采样的WNCS建模为一类具有短暂不确定切换信号的离散切换系统,采用切换状态反馈控制律,利用切换系统理论分析了系统的稳定性,给出了系统渐近稳定时控制器增益与滞留时间需要满足的约束条件．最后在Truetimel．5和MATLAB仿真平台上验证了文中提出的方法和结论．     

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.     

基于标准神经网络模型的非线性系统分布式无线网络化控制

针对采用标准神经网络模型(SNNM)描述的非线性系统,提出一种基于无线控制网络(WCN)的全分布式控制方法.采用置信因子模拟WCN中无线通信链路的不确定性,利用Lyapunov理论和Lur’e系统方法,将无线网络化控制系统(WNCS)的稳定性分析转化为一个具有线性矩阵不等式(LMI)约束的凸优化问题;使用CVX工具包求解该凸优化问题,得到了保证闭环系统全局渐近稳定的WCN配置参数.仿真结果验证了所提出控制策略的正确性和有效性.     

无线网络化控制系统的功率感知事件触发策略及其闭环稳定性

本文研究了能量受限无线网络化控制系统的设计和分析问题.首先建立了无线网络化控制系统中通信传输时的数据误码率和丢包率间的定量关系,从而在通信功率与系统性能之间建立了联系.进而设计了基于事件触发策略和功率优化机制的智能控制器,该方法充分考虑了网络节能与控制系统性能表现两方面的要求,通过添加事件触发机制减少了系统的通信次数,并在此基础上以优化算法优化单次发送功率.随后,在随机稳定框架下给出了相应闭环系统稳定的充分性条件,在理论上证明了在该充分条件下,本文的设计能够在降低通信能耗的同时令系统维持预期的性能表现.最后数值例子证明了所提出方法的有效性.     

具有数据包丢失及多包传输的网络控制系统稳定性

在分析网络数据包丢失和多包传输原因的基础上,研究存在数据包丢失和多包传输的网络控制系统稳定性问题.根据网络数据包丢失模型,提出了信号传输成功率应满足的系统指数稳定性条件,并依据具有事件概率限制的异步动态系统理论建立了多包传输网络控制系统模型,给出了判定系统指数稳定性的充分条件.仿真示例验证了上述判定系统稳定性条件的有效性.     

不确定时滞模糊系统的鲁棒H∞网络控制

A robust H_∞networked control method for Takagi-Sugeno (T-S) fuzzy systems with uncertainty and time delay is presented.A state feedback controller is designed via the networked control system (NCS) theory.Sufficient condition for robust stability with H_∞performance is obtained.Network-induced delay in network transmission and packet dropout are analyzed. Simulation result shows the validity of this control scheme.     

Optimal codesign of industrial networked control systems with state‐dependent correlated fading channels

This paper examines a codesign problem in industrial networked control systems (NCS) whereby physical systems are controlled over wireless fading channels. The considered wireless channels are assumed to be stochastically dependent on the physical states of moving machineries in the industrial working space. In this paper, the moving machineries are modeled as Markov decision processes whereas the characteristics of the correlated fading channels are modeled as a binary random process whose probability measure depends on both the physical states of moving machineries and the transmission power of communication channels. Under such a state‐dependent fading channel model, sufficient conditions to ensure the stochastic safety of the NCS are first derived. Using the derived safety conditions, a codesign problem is then formulated as a constrained joint optimization problem that seeks for optimal control and transmission power policies which simultaneously minimize an infinite time cost on both communication resource and control effort. This paper shows that such optimal policies can be obtained in a computationally efficient manner using convex programming methods. Simulation results of an autonomous forklift truck and a networked DC motor system are presented to illustrate the advantage and efficacy of the proposed codesign framework for industrial NCS.     

Resilient control for wireless networked control systems

This paper proposes an approach to quantify the concept of resiliency in terms of Quality of Control (QoC) of a control system. Based on this concept, an intelligent resilient control algorithm (RCA) is presented for wireless networked control systems (WNCS) to maintain operational normalcy in face of wireless interference incidents, such as Radio Frequency (RF) jamming and signal blocking. The proposed algorithm closes the control loop with wireless sensors feasible by significantly increasing control system’s tolerance to data packet loss and delay caused by wireless interference. The proposed algorithm, along with other well developed wireless technologies, has the potential to enable implementing wireless sensors widely in the next generation of industrial automation and control systems.     

Anomaly detection and resilient control of networked control system with multi-hop routing

With the wide application of networked control systems, how to deal with data injection attacks and maintain the stability of control systems including wireless multi-hop networks is a problem that the researchers and technological workers must consider and solve. Based on the construction of a control system including wireless multi-hop networks, the data transmission mode between routing nodes and the stability condition of the control system are given. Considering the existence of data injection attacks to routing nodes, a real-time detection method for anomaly behaviours is presented on the basis of chi-square goodness-of-fit test. In the case of data injection actions taking place, a strategy of switching paths in turn is used to execute the control task. The strategy is satisfied with the resilient stability of the control system. The simulation results show that the detection method can detect the data injection actions in real time, and the control strategy can restore control variables to proper values when the data injection actions exist. These methods have certain application prospects and popularisation values.     

Fundamental Issues in Networked Control Systems

This paper provides a survey on modeling and theories of networked control systems (NCS). In the first part, modeling of the different types of imperfections that affect NCS is discussed. These imperfections are quantization errors, packet dropouts, variable sampling/transmission intervals, variable transmission delays, and communication constraints. Then follows in the second part a presentation of several theories that have been applied for controlling networked systems. These theories include: input delay system approach, Markovian system approach, switched system approach, stochastic system approach, impulsive system approach, and predictive control approach. In the last part, some advanced issues in NCS including decentralized and distributed NCS, cloud control system, and co-design of NCS are reviewed.      

基于状态空间模型的无线网络控制仿真研究

针对采用状态空间模型描述的几类无线网络控制系统,介绍了基于TrueTime的无线网络控制系统仿真程序的设计与实现问题。首先介绍了TrueTime工具箱的组成,然后给出了如何利用无线仿真模块实现基于状态空间模型描述的控制系统仿真方法。分别考虑当系统具有单输入多输出、网络诱导时延、数据丢包、时滞脉冲等特性时,利用TrueTime仿真工具箱,如何建立上述系统的无线网络控制仿真模型以及如何编写相应的程序代码。根据上述不同模型的仿真可以看出,对于不同的系统,他们的初始化设置基本相同,而任务代码却有很大的差别。仿真曲线符合理论结果,说明了仿真模型和程序代码的正确性与有效性。     

On the stability of networked impulsive control systems

In this paper, the stability of linear networked impulsive control systems is studied. The data dropout rate over N steps (DRNS) is defined, and the maximal allowable DRNS is computed, which provides a guideline for the system stability in the sense that, if the actual DRNS is less than this maximal value, then the system is asymptotically stable. To handle the network‐induced delays, a propagation unit based on the system model is introduced to the system. A necessary and sufficient condition for the asymptotical stability of the networked system with the propagation unit is derived. Furthermore, networked linearized impulsive control systems suffering from both transmission delays and data dropouts are also investigated. To design proper impulsive controllers for such systems, some algorithms are further proposed based on LMI techniques and V‐K iteration approaches. Finally, numerical examples are presented to illustrate the theoretical results. Copyright © 2011 John Wiley & Sons, Ltd.     

Control for wireless networked control systems based on 802.11b

In this article, the stabilisation problem is considered for a wireless networked control system. A new model is constructed by integrating the wireless network protocols in IEEE802.11 with control systems. All the possible delays and dropouts are considered in the new model for the packets to be transmitted on both the sensor-to-controller side and the controller-to-actuator side of the WNCS structure. A linear state feedback controller is designed to stabilise the model. The results are given in the form of linear matrix inequalities. Finally, simulations are performed to show the effectiveness of the proposed method.     

无线网络控制系统的研究

介绍了无线网络控制系统出现的背景，综述了无线网络控制系统的研究内容及现状。无线网络控制系统是基于无线网络的分布式控制系统。它融合了控制技术、计算机技术、网络技术与通信技术，已成为控制界的热点研究之一。针对无线网络控制系统中存在的随机时延和数据丢包，讨论了系统的建模问题，分析了目前的研究现状，并总结了国内外在无线网络控制系统研究过程中所提出的方法和取得的成果，提出了有待进一步解决的问题及以后的研究方向。     

MIMO网络控制系统的稳定性分析

推导了多输入多输出网络控制系统的时滞离散时间数学模型，此模型包括了控制网络的网络延时．提出了一种新的网络控制系统稳定性分析方法，得到了使系统稳定的各网络延时应满足的条件．只要系统的网络延时满足这些条件，网络控制系统的极点便分布在复平面内的一个圆形区域内．若此圆形区域在单位圆内，网络控制系统就是稳定的．仿真实验验证了所提理论的有效性．