实时数据库系统双机热备机制设计与实现

双机热备计算机系统可实现高任务可靠性,广泛应用于电力系统.针对实时数据库系统提出了一种新颖的双机热备设计技术,基于系统及资源状态检测与监控、双机状态一致性同步、网络通信协议、主备切换机制、数据镜像服务等关键技术实现了模块设计.主控模块对主备服务器工作状态进行仲裁与检测,网络通信模块检测服务器故障,切换控制模块实时响应服务器故障进行切换,配置模块对双机信息进行设置,保证了系统高可靠性持续运行.     

煤矿安全监控系统双机热备软件实现方案

针对煤矿安全监控系统的双机热备问题,提出了一种软件实现方案,即利用SQL Server 2000数据库的触发器拦截数据库更新的数据,采用双机热备软件实现数据双机同步,并通过人机界面与用户交互;针对该方案下可能出现的备机故障、数据库故障以及软件故障,提出了相应的解决方案。应用结果表明,该双机热备软件实现方案效果良好。     

自来水行业集散型控制系统的可靠性技术及性能分析

介绍了采用可靠性冗余设计技术来提高自来水给水集散型控制系统可靠性的方法,详细介绍了控制系统中冗余技术设计方案、整体结构的分析、主控机双机热备的设计方案以及PLC双机热备系统的实现.     

煤矿水泵控制系统双机热备设计方案

介绍了一种应用于煤矿水泵控制系统的主—备方式双机热备设计方案,阐述了双机热备工作过程,详细介绍了双机热备的总体设计、基本业务流程及接管控制流程设计。两台控制机之间通过心跳帧实现数据交互,通过比较切换时间及控制机地址数值解决初始化时两台控制机同时上电、争抢主控权的问题,通过备用机接管控制解决主控机在控制设备启停过程中发生故障可能导致设备失控的问题。该方案实现了主控机与备用机的自动切换,达到了系统不间断运行的目的,提高了系统的稳定性。     

基于数据库导出导入功能的煤矿双机热备系统

针对中小煤矿应用的双机热备需求,提出了一种基于数据库导出导入功能的纯软件形式的煤矿双机热备系统实现方案,详细介绍了系统的同步策略、网络传输及实现流程,并阐述了双机热备的任务切换和上层应用的透明访问等功能及流程。该方案具有效率高、容错性好、部署简单和运行稳定等特点,可满足煤炭行业对双机热备系统的通用技术要求。     

化学水处理PLC监控系统的设计与实现

介绍了可编程序控制器（ＰＬＣ）在化学水处理监控系统中的应用。该系统在硬件结构上采用上位机双机监控,下位机ＰＬＣ双机热备的二级监控形式,并着重讨论了本系统的特色之处－下位机ＰＬＣ双机热备的软件实现。实践表明：该系统能够有效地实现对化学水处理过程的自动监控,安全可靠,自动化程度高。     

双机热备份系统切换及同步设计

在航天型号系统的研制中,可靠性是衡量产品功能、性能稳定性的关键指标,采用双机热备份设计是系统提高可靠性的有效手段.任务处理单元是某型号运载火箭箭上电气系统的一个重要控制设备,是信息综合管理的核心,在高可靠性的前提下,也有较高的实时性要求.为了保障其故障时仍可以正常工作,设计了冗余热备系统双机之间的故障检测及切换策略,能够通过多种途径及时发现故障并实施主机切换.在此基础上,针对双机数据、状态同步的关键过程给出了两种基于VxWorks任务级同步的设计和实现方法,通过软件有效的控制管理使双机系统具有较强的可靠性和实时性.     

煤矿企业纯软件方式的双机热备系统研究

针对煤矿监控系统双机热备标准方案中硬件设备昂贵、维护成本较高的问题,设计了一种纯软件方式的双机热备系统。该系统利用文件差异备份以及MYSQL增量备份相结合的方式将数据保存到主、备机中,即采用RSYNC文件同步算法对文件进行备份,利用MYSQL数据库的Binary Log机制开启日志记录文件,将在一个时间间隔内发生修改的数据信息导出到增量备份文件中,并将增量备份文件发送到备机中,备机将修改数据导入数据库,从而达到数据库同步操作的目的。同样地,在主机出现故障后,在备机中修改的数据以同样的方式同步到主机中。该双机热备系统已投入实际应用,满足了煤矿监控系统中数据实时性与数据完整性的要求。     

基于Markov模型的可维修双机热备系统可靠性分析

为了综合考虑维修性、故障检测率及共因失效对双机热备系统可靠性的影响,利用马尔可夫模型对可维修双机热备系统进行可靠性分析.由系统状态转移关系建立双机热备系统的状态转移图,由于备用单元发生不可测失效时不能及时对其进行维修,提出在状态转移图中增加一个状态来区分此种降级工作状态.根据状态转移图得到系统状态转移方程并借助Matlab对其进行求解,得到故障检测率、失效率、维修率与共因失效因子为不同取值时的系统状态概率图.分析结果表明,维修率对可维修双机热备系统达到平稳状态所需时间贡献较大,系统工作状态概率值与故障状态概率值则由故障率与修复率的比值、故障检测率及共因失效等因素共同决定.     

高速铁路智能CTC自律机系统的可靠性与安全性评估

自律机系统是智能调度集中控制(Centralized traffic control, CTC)系统的核心, 其安全性和可靠性都至关重要. 首先分析了双机热备自律机系统和二乘二取二自律机系统的结构及工作原理; 然后综合考虑自律机分机的故障检出率和故障发生率等因素, 采用Markov模型, 构建了两个系统的安全度和可靠度模型. MATLAB仿真结果表明, 双机热备自律机系统的可靠性高于二乘二取二自律机系统的, 但双机热备自律机系统的安全度远低于二乘二取二自律机系统的, 因此二乘二取二自律机系统更能保障CTC系统的安全.     

Resource Allocation for Reliable Communication Between Controllers and Switches in SDN

In software-defined networking (SDN), the communication between controllers and switches is very important, for switch can only work by relying on flow tables received from its controller. Therefore, how to ensure the reliability of the communication between controllers and switches is a key problem in SDN. In this paper, we study this problem from two aspects: the controller placement and the resource backup aspect. Firstly, in order to implement the reliable communication and meet the required propagation delay between controllers and switches, a min-cover based controller placement approach is proposed. Then, in order to protect both controllers and control paths from regional failure, a backup method based on an exponential decay failure model is proposed, which considers the regional influence and the survivability of backup controllers and control paths. Simulations show that our controller placement approach can meet the reliability and delay requirement with appropriate controller allocation scheme, and our backup method can improve the survivability of backup controllers and control paths while ensuring the performance of control network.     

Designs of Bisimilar Petri Net Controllers With Fault Tolerance Capabilities

This paper proposes an approach for providing tolerance against faults that may compromise the functionality of a given controller modeled by a Petri net. The method is based on embedding the given Petri net controller into a larger (redundant) Petri net controller that retains the original functionality and properties, and uses additional places, connections, and tokens to impose invariant conditions that allow the systematic detection and identification of faults via linear parity checks. In particular, this paper considers two types of redundant Petri net controllers: 1) nonseparate redundant Petri net controllers have the same functionality as the given Petri net controller and allow for fault detection and identification, but do not necessarily retain the given controller intact; and 2) separate redundant Petri net controllers are a special case of the nonseparate redundant controllers that retain the given Petri net controller intact but enhance it with additional places to enable fault detection and identification. The work in this paper obtains complete characterizations of both types of redundant controllers along with necessary and sufficient conditions for them to be bisimulation equivalent to the given original Petri net controller. In addition, this paper discusses how each type of redundant controllers can be designed to have desirable fault detection and identification capabilities. When the bisimulation equivalence requirement is not directly enforced, nonseparate redundant controllers can potentially have advantages over separate ones (e.g., they can use fewer connections to detect and identify the same number of faults). An example of a Petri net controller for a production cell and its fault tolerance capabilities using separate and nonseparate embeddings is used to illustrate the approach.     

Decentralized fault tolerant control of a class of nonlinear interconnected systems

In this paper, a novel decentralized fault tolerant controller (DFTC) is proposed for interconnected nonlinear continuous-time systems by using local subsystem state vector alone in contrast with traditional distributed fault tolerant controllers or fault accommodation schemes where the measured or the estimated state vector of the overall system is needed. The proposed decentralized controller uses local state and input vectors and minimizes the fault effects on all the subsystems. The DFTC in each subsystem includes a traditional controller term and a neural network based online approximator term which is used to deal with the unknown parts of the system dynamics, such as fault and interconnection terms. The stability of the overall system with the proposed DFTC is investigated by using Lyapunov approach and the boundedness of all signals is guaranteed in the presence of a fault. Therefore, the proposed controller enables the system to continue its normal operation after the occurrence of a fault, as long as it does not cause failure or break down of a component. Although the decentralized fault tolerant controller is designed mainly for large-scale systems where continuous transmissions between subsystems is not possible, it can also be applied to small-scale systems where sensor measurements are available for use in all subsystems. Finally the proposed methods are verified and compared in simulation environment.     

Decentralized model predictive control of a multi-evaporator air conditioning system

Temperature control of multiple zones with a multi-evaporator vapor compression system is a common problem in modern air conditioning. Due to the coupled system dynamics, standard decoupled controllers can interfere with each unit′s performance. This paper proposes an architecture that is decentralized and modular, avoiding competing controllers and the practical difficulty of implementing a centralized controller. A model predictive control (MPC) supervisor calculates evaporator cooling and pressure setpoints for each zone, balancing temperature regulation with energy efficiency; these setpoints are tracked by local level controllers, which rely upon MPC's ability to respect constraints in order to maintain safe, efficient operation.     

工业控制系统VPN网关的双机热备功能设计

随着网络技术的快速发展,远程安全通讯的需求日益强烈,针对工业控制系统而言,安全可靠的远程通信是工业控制系统正常稳定运行的前提。VPN技术是实现远程安全通信的有效解决方案,其基于对称密码算法实现数据的高速加密,基于非对称密码算法实现通信实体的身份认证以及数字签名,有效实现了远程通信数据的机密性保护和完整性保护。随着业务系统可靠性需求的提升,VPN网关双机热备功能成为远程通信需要重点解决的问题,针对工业控制系统VPN网关的双机热备功能进行了设计,首先讨论了工业控制系统VPN网关的部署架构,其次详细设计了VPN网关的双机热备各软件功能模块,实际应用证明,VPN网关的双机热备设计可以有效提高网络链路的可靠性,有效保障企业业务系统的可用性。     

基于FPGA的双机热备外设容错系统仿真设计

针对传统的继电保护冗余系统缺乏对敏感外设容错处理、切换速度慢等问题,提出了基于FPGA的双机热备外设容错系统。该系统由FPGA控制器、DSP控制器、双A/D模块、双继电器模块等外设组成,FPGA控制器完成双机外设模块的故障检测、双机实时切换,为DSP控制器提供A/D实时采样数据、继电器信号接口,DSP控制器对采样数据进行计算与分析,产生继电保护信号,FPGA控制器和DSP控制器通过"心跳"信号互相检测。FPGA控制器时序仿真波形表明:双机外设模块可以实现周期故障自检、双机快速切换。     

基于软件定义网络的分层式控制器负载均衡机制

针对软件定义网络（SDN）多控制器负载均衡过程中控制器之间通信开销大以及控制器吞吐量低等问题,提出一种分层式控制器负载均衡机制。基于分层式架构,通过超级控制器与域控制器协作完成负载均衡,并采用预定义负载阈值以减少域控制器与超级控制器之间的消息交换开销;同时,该机制可以有效选择出过载最重的域控制器,并从该过载域控制器所控制的交换机中选取多个符合迁移标准的交换机,将其同时分别迁移到多个综合性能高的域控制器上,从而解决多控制器间负载不均衡问题。实验结果表明,与层次式SDN控制器协同负载均衡方案（COLBAS）以及用于控制器负载均衡的动态和自适应算法（DALB）相比,所提机制系统的消息数量降低了约79个百分点,且该系统的吞吐量分别比DALB、COLBAS分别提高了约8.57%、52.01%。所提机制能够有效降低通信开销,并提高系统吞吐量,有更好的负载均衡效果。     

Collaborative Fault Tolerant Control for Non‐Gaussian Stochastic Distribution Systems Based on Adaptive Control Strategy

This paper presents a new fault tolerant controller design method for a class of interconnected non‐Gaussian stochastic distribution system with boundary conditions. In order to obtain the fault estimation value, an observer based fault detection and fault diagnosis algorithms are presented at first, then a collaborative fault tolerant controller is designed based on the adaptive control strategy. Different from most of the existing fault tolerant controllers, when fault occurs the controller need to be reconstructed is for the healthy subsystem in this paper. That is to say, the fault is compensated not by the faulty subsystem itself but by the healthy one. The proposed method is used to a simulation example for demonstration, and the effectiveness is verified.