Distributed dynamic event-based finite-time dissipative synchronization control for semi-Markov switched fuzzy cyber-physical systems against random packet losses

This paper is concerned with the finite-time dissipative synchronization control problem of semi-Markov switched cyber-physical systems in the presence of packet losses, which is constructed by the Takagi–Sugeno fuzzy model. To save the network communication burden, a distributed dynamic event-triggered mechanism is developed to restrain the information update. Besides, random packet dropouts following the Bernoulli distribution are assumed to occur in sensor to controller channels, where the triggered control input is analyzed via an equivalent method containing a new stochastic variable. By establishing the mode-dependent Lyapunov–Krasovskii functional with augmented terms, the finite-time boundness of the error system limited to strict dissipativity is studied. As a result of the help of an extended reciprocally convex matrix inequality technique, less conservative criteria in terms of linear matrix inequalities are deduced to calculate the desired control gains. Finally, two examples in regard to practical systems are provided to display the effectiveness of the proposed theory.

Robust fault detection for delta operator switched fuzzy systems with bilateral packet losses

Considering packet losses, time-varying delay, and parameter uncertainty in the switched fuzzy system, this paper designs a robust fault detection filter at any switching rate and analyzes the H∞ performance of the system. Firstly, the Takagi-Sugeno(T-S) fuzzy model is used to establish a global fuzzy model for the uncertain nonlinear time-delay switched system,and the packet loss process is modeled as a mathematical model satisfying Bernoulli distribution. Secondly, through the average dwell time method and multiple Lyapunov functions, the exponentially stable condition of the nonlinear network switched system is given. Finally, specific parameters of the robust fault detection filter can be obtained by solving linear matrix inequalities(LMIs). The effectiveness of the method is verified by simulation results.

Event-triggered Tracking Consensus with Packet Losses and Time-varying Delays

This paper mainly investigates the event-triggered tracking control for leader-follower multi-agent systems with the problems of packet losses and time-varying delays when both the first-order and the second-order neighbors' information are used. Event-triggered control laws are adopted to reduce the frequency of individual actuation updating under the sampleddata framework for discrete-time agent dynamics. The communication graph is undirected and the loss of data across each communication link occurs at certain probability, which is governed by a Bernoulli process. One numerical example is given to demonstrate the effectiveness of the proposed methods.It is found that the tracking consensus is sped up by using the second-order neighbors' information when packet losses and time-varying delays occur.

Evaluation of packet loss impairment on streaming video

Video compression technologies are essential in video streaming application because they could save a great amount of network resources. However compressed videos are also extremely sensitive to packet loss which is inevitable in today's best effort IP network. Therefore we think accurate evaluation of packet loss impairment on compressed video is very important. In this work, we develop an analytic model to describe these impairments without the reference of the original video (NR) and propose an impairment metric based on the model, which takes into account both impairment length and impairment strength. To evaluate an impaired frame or video, we design a detection and evaluation algorithm (DE algorithm) to compute the above metric value. The DE algorithm has low computational complexity and is currently being implemented in the real-time monitoring module of our HDTV over IP system. The impairment metric and DE algorithm could also be used in adaptive system or be used to compare diffeient error concealment strategies.

Fault Tolerant Control for Networked Control Systems with Packet Loss and Time Delay

In this paper,a fault tolerant control with the consideration of actuator fault for a networked control system （NCS） with packet loss is addressed.The NCS with data packet loss can be described as a switched system model.Packet loss dependent Lyapunov function is used and a fault tolerant controller is proposed respectively for arbitrary packet loss process and Markovian packet loss process.Considering a controlled plant with external energy-bounded disturbance,a robust H ∞ fault tolerant controller is designed for the NCS.These results are also expanded to the NCS with packet loss and networked-induced delay.Numerical examples are given to illustrate the effectiveness of the proposed design method.

Packet-loss-dependent stabilization of NCSs with network-induced delay and packet dropout

This paper is concerned with controller design of net- worked control systems （NCSs） with both network-induced delay and arbitrary packet dropout. By using a packet-loss-dependent Lyapunov function, sufficient conditions for state/output feedback stabilization and corresponding control laws are derived via a switched system approach. Different from the existing results, the proposed stabilizing controllers design is dependent on the packet loss occurring in the last two transmission intervals due to the network-induced delay. The cone complementary lineara- tion （CCL） methodology is used to solve the non-convex feasibility problem by formulating it into an optimization problem subject to linear matrix inequality （LMI） constraints. Numerical examples and simulations are worked out to demonstrate the effectiveness and validity of the proposed techniques.

A channel distortion model for video over lossy packet networks

Error-resilient video communication over lossy packet networks is often designed and operated based on models for the effect of losses on the reconstructed video quality. This paper analyzes the channel distortion for video over lossy packet networks and proposes a new model that, compared to previous models, more accurately estimates the expected mean-squared error distortion for different packet loss patterns by accounting for inter-frame error propagation and the correlation between error frames. The accuracy of the proposed model is validated with JVT/H.264 encoded standard test sequences and previous frame concealment, where the proposed model provides an obvious accuracy gain over previous models.

Kalman Filtering with Partial Markovian Packet Losses

We consider the Kalman filtering problem in a networked environment where there are partial or entire packet losses described by a two state Markovian process. Based on random packet arrivals of the sensor measurements and the Kalman filter updates with partial packet, the statistical properties of estimator error covariance matrix iteration and stability of the estimator are studied. It is shown that to guarantee the stability of the Kalman filter, the communication network is required to provide for each of the sensor measurements an associated throughput, which captures all the rates of the successive sensor measurements losses. We first investigate a general discrete-time linear system with the observation partitioned into two parts and give sufficient conditions of the stable estimator. Furthermore, we extend the results to a more general case where the observation is partitioned into n parts. The results are illustrated with some simple numerical examples.

NEW METHOD TO RECOVER INTERNET PACKET LOSSES USING(2,1,m)SYSTEMATIC CONVOLUTIONAL CODES

A new method to recover packet losses using (2,1,m) convolutional codes is proposed.The erasure correcting decoding algorithm and the decoding determinant theorem is presented. It is also proved that the codes with optimal distance profile have also optimal delay characteristic.Simulation results show that the proposed method can recover the packet losses more efficiently than RS codes over different decoding delay conditions and thus suits for different packet network delay conditions.

高量测丢包率下基于共享模糊等价关系的配电网状态感知

配电网分布式新能源渗透率的不断增加,对实时监测的要求不断提高,大量量测数据在集中传输过程中常常出现延迟、丢包等现象导致配电网状态感知精度降低甚至不可观测。针对上述问题,提出基于共享模糊等价关系的状态感知方法。首先,将采集得到的多时间断面历史量测数据集作为源数据集,实时采集得到的高量测丢包率下的数据作为目标数据集。利用三角形隶属度函数分别将两组数据集写成模糊集的形式。然后采用一种向量间距离度量方法,分别计算得到两组模糊集的模糊等价关系矩阵。在此基础上,采用共享模糊等价关系的聚类方法,将知识从源数据集转移到目标数据集,减小两组数据集特征分布之间的差异。最后,利用深度神经网络对知识迁移后低维特征空间中高量测丢包率对应的数据进行标记,得到配电网实时状态。通过对IEEE标准算例和某实际地市公司配电网算例进行仿真测试,结果表明所提出的基于共享模糊等价关系的配电网状态估计方法能在高量测丢包率下获得准确的配电网实时运行状态,实现不同量测数据缺失程度下的配电网实时监测。

基于物联网农业灌溉系统的参数检测方法研究

为提升农业灌溉系统检测环节准确性及整体作业效率为目标,基于物联网灌溉及参数检测方法应用展开设计。以当前灌溉作业机理及通信结构布局为出发点,通过建立合理正确的参数检测架构,选定高效适应的参数检测方法,实现整体灌溉系统功能优化。进行灌溉系统作业监测试验,结果表明:参数数据通信监测准确率及系统执行效率分别提升至93.70%与95.89%,系统丢包率相对降低至0.79%,平均节水效率相对提升了6.39%。基于物联网平台进行参数检测的有效性与适应性改进,较好地满足了智能灌溉的发展趋势,其方法研究理念对于灌溉系统及类似农机培育系统开发应用具有参考价值。

HGU用户侧接口流量信息传输方法仿真

由于连接不同用户的侧接口过多,导致接口流量信息分配不均衡,造成信息传输时长较长、丢包率高等问题。为解决上述问题,提出HGU用户侧接口流量信息传输方法。通过对家庭网关单元(Home Gateway Unit,HGU)用户侧接口构建无向图和冲突图,确定流量信息传输距离以及各传输链路之间是否互相干扰;以链路流量模型为基础构建业务模型,得到传输链路负载率;在粒子群优化算法中,利用适应度函数更新粒子的位置坐标,实现合理分配网络流量,实现最大效率的传输。实验结果表明,所提方法网络时延始终保持在0.10s以下,整体丢包率控制在30%-45%之间,且具有较高的吞吐量。

网络控制系统中利用主动丢包的重放攻击检测方法

为实现网络控制系统(Networked Control Systems,NCS)中重放攻击的检测,在现有研究利用物理水印检测重放攻击的启发下,设计了利用主动丢包对重放攻击进行实时检测的方法 .首先,在理论层面上,利用系统输出的残差构建检测函数,并通过受攻击前后检测函数的变化,证明该检测方法的有效性.然后,以一辆四轮汽车为被控对象,比较车辆受攻击前后速度与检测函数的变化.最后,综合考虑车辆对重放攻击的检测结果与速度跟踪结果,确定车辆的最优主动丢包率的范围区间.结果表明:加入主动丢包前,车辆受到重放攻击时,速度会发生剧烈变化而检测函数几乎没有变化;加入主动丢包后,车辆受到重放攻击时,速度剧烈变化的同时检测函数也产生了剧烈的变化;主动丢包率为12%~16%时,系统既能够准确地检测出重放攻击,又能够保证车辆平稳行驶,为后续的重放攻击检测研究提供了参考.

改进TDM-LoRa低功耗森林火灾监测预警系统

针对目前森林火灾监测系统成本高、功耗大、维护复杂的缺点,提出一种基于改进TDM-LoRa设计的低功耗森林火灾监测预警系统.系统以STM32系列微处理器为节点控制核心,LoRa-SX1278芯片为通信模块,并使用增量传输和改进时分复用通信机制,有效降低节点能耗,从而延长监测节点和汇聚节点寿命.试验结果表明,数据信息在发射功率为20 dBm、传输速率为1.2 kbit·s^(-1)的情况下,节点在3500 m范围内实现的丢包率仅为7.2%;在使用2600 mA·h的电池、数据采集上传间隔时间为30 min的情况下,单个节点有效工作时间理论可达90.7个月,实现无中继远距离低功耗森林环境监测数据的采集.

小波包分解重构的励磁变压器整流谐波附加损耗计算

谐波损耗是造成励磁变压器安全事故的主要原因之一,损耗值过大易影响正常变电和输电,为此提出基于小波包分解重构的励磁变压器整流谐波附加损耗计算方法。通过获取小波包分解和重构系数,分析励磁变压器两种谐波附加损耗;利用开路和短路实验得到励磁变压器等效电路参数,采用小波包分解重构算法,计算不同谐波次数下的电阻和电抗并与基准值对比,得到励磁变压器整流谐波附加损耗值。最后,选取某种型号的励磁变压器,利用所提方法计算其在不同谐波次数下的附加损耗值,结果表明,得到的损耗值计算结果与实际结果非常接近,验证了所提方法具有较高的实用价值。

基于事件触发的Delta算子网络控制系统故障检测

针对网络控制系统在高速采样情况下,网络中由于通信网络带宽受限发生时延和丢包所引起的故障问题,文中采用了基于事件触发机制和Delta算子相结合的故障检测方法。在对故障检测滤波器和控制器进行协同设计的同时,在Delta算子滤波器模型中加入构造向量,避免了参数设计时双线性项的产生。构造δ域的Lyapunov-Krasovskii泛函,对残差系统的稳定性和H∞性能进行分析。数值仿真实例验证了文中所提事件触发机制的有效性,并通过残差评价函数证明了其对故障的灵敏度较高。

Adaptive Hybrid Forward Error Correction Coding Scheme for Video Transmission

This paper proposes an adaptive hybrid forward error correction(AH-FEC)coding scheme for coping with dynamic packet loss events in video and audio transmission.Specifically,the proposed scheme consists of a hybrid Reed-Solomon and low-density parity-check(RS-LDPC)coding system,combined with a Kalman filter-based adaptive algorithm.The hybrid RS-LDPC coding accommodates a wide range of code length requirements,employing RS coding for short codes and LDPC coding for medium-long codes.We delimit the short and medium-length codes by coding performance so that both codes remain in the optimal region.Additionally,a Kalman filter-based adaptive algorithm has been developed to handle dynamic alterations in a packet loss rate.The Kalman filter estimates packet loss rate utilizing observation data and system models,and then we establish the redundancy decision module through receiver feedback.As a result,the lost packets can be perfectly recovered by the receiver based on the redundant packets.Experimental results show that the proposed method enhances the decoding performance significantly under the same redundancy and channel packet loss.

智能变电站PMU频率跳变问题的诊断及处理

某省区WAMS(广域测量系统)中某智能变电站数字化PMU(相量测量单元)偶尔出现频率跳变现象。首先,调取频率跳变时刻的动态数据记录和录波文件,结合现场运行方式进行分析,得出两次频率跳变事件的原因。然后,通过调整智能终端模拟量阈值、改进SV(采样值)组网模式、划分交换机VLAN(虚拟局域网)、调整装置带宽阈值,解决了SV丢点造成的频率波动;同时对SV补点提升PMU装置SV异常容错能力,丢帧数小于3不会造成频率波动超限。接着,查找现场扰动源,分析扰动造成PMU频率波动的原因,提出基于触发录波文件的扰动快速识别方法。最后,通过实验验证了所提方法的有效性。

车路协同技术应用与性能对比及智能融合仿真分析

交通网络的持续扩展和交通流的不断增加使得高速公路协同管控极为重要,通过科学的协同管控策略来有效提升交通效率和行车安全性。在对车路协同技术分析的基础之上,构建了车路协同架构,并对高速公路场景不同通信协议的性能进行了对比,指出C-V2X技术的丢包率明显低于IEEE 802.11p技术。结合行车方向,避免反向车辆干扰,提出了高速公路资源调度算法,并通过仿真验证了高速公路资源调度算法能够有效避免反向车辆通信干扰,降低丢包率。

计及信息不确定性的多端交直流混合配电网分布式二级协同控制

分布式一致性控制(distributed consensus control,DCC)因其灵活协同能力成为交直流混合配电网二次控制的新途径.然而,传统DCC并未考虑实际通信环境中存在的随机时变时延和数据丢包问题,这致使其在非理想通信环境下难以稳定跟踪一致性期望目标.为此,本文提出一种计及信息不确定性的分布式二级协同控制策略.利用变量累加补偿机制,对时变时延和数据丢包进行统一等效.进而基于附加一致性算法(surplus consensus algorithm,SCA)构建具有零稳态误差特性的估计器,并对其收敛性进行推导证明.在此基础上,设计稳态收敛性能不受通信约束干扰的SCA-DCC控制器,实现非理想通信环境下的精准平均电压偏差调节和有功功率成比例分配.随后,以时延容忍度为指标优化SCA-DCC控制器参数,满足系统在不同通信条件下的稳定需求,进一步增强控制器的通信鲁棒性.仿真结果表明,在不同功率扰动和故障工况下,与现有控制策略相比,所提控制策略能够克服时变时延和数据丢包产生的负面影响,在维持较优动态响应性能的同时使稳态电压偏差降低73.08%~85.25%,具有控制精度高和抗扰动能力强的特点.