网络控制系统的研究综述

综述了近几年网络控制系统(networked control systems,NCS)的研究成果,介绍了网络控制系统最常见的基本结构,分析了影响NCS性能的问题,如时延、丢包、时序、带宽等.由于已有的NCS综述对于控制性能的讨论不多,故文章从稳定性和跟踪性两个角度总结和评述了 NCS的研究成果,并简要说明了NCS的应用.     

一种基于遗传算法的NCS控制器延时约束参数优化方法

网络化控制系统(NCS)设计中,如何提高系统性能质量(QOP)及网络服务质量(QOS)一直是本领域的热点问题,而对于此类问题的寻优过程必然需要以网络系统的数据延迟以及丢包问题展开。针对此问题,提出了一种基于遗传算法的网络化控制系统闭环延迟约束参数优化方法。在保证系统稳定性的情况下提高控制质量。最后给出了一组仿真参数,验证了方法的可行性与有效性。     

网络控制系统调度问题的研究与进展

网络控制系统的优化调度是保证网络服务质量(Q(P)的重要手段.在综合了国内外网络调度问题研究方法的基础上,将网络调度方法分类为协议层调度,应用层调度,协同调度和反馈调度四个方面,定义了每类方法的研究内容,详细介绍了每类方法的研究现状和特点,并提出了网络控制系统调度问题研究的发展方向.     

电动汽车CAN总线混合调度方法的研究

电动汽车网络控制系统中传输的消息越采越多，固定调度方法已经不能满足系统的消息传输。为此本文提出一种混合调度方法采对电动汽车中的消息进行调度。实验证明该方法改善了电动气车的整体控制性能，使得网络的利用率得到提高，消息的截止期得到满足。     

支持敏捷制造的控制系统体系结构研究

基于制造自动化系统的层次模型和Infranet、Intranet、Internet的3I网络集成结构，建立了支持敏捷制造的控制系统(NCS)的体系结构着重研究了NCS的网络计算结构、功能结构、集成机制和实现策略。     

无源二线制智能数字显示表的设计与实现

TTCAN是近几年发展起来并广泛应用于汽车以及其它一般工业控制系统的实时传输协议[1].分析了TTCAN网络平台对于周期性消息及非周期性消息的调度策略,分别对其进行改进,并通过遗传算法对系统矩阵周期调度表进行优化,之后利用Simulink中的Stateflow工具针对一般工业控制系统建立了TTCAN网络调度仿真平台,并对仿真平台进行优化,优化后的仿真平台较好地提高了网络系统带宽利用率,增大了总线通信量,降低了各传感器节点周期性消息的响应时间和非周期性消息的延时时间,从而改善了网络平台的通信实时性能.     

TTCAN网络调度平台的设计优化

TTCAN是近几年发展起来并广泛应用于汽车以及其它一般工业控制系统的实时传输协议~([1]).分析了TTCAN网络平台对于周期性消息及非周期性消息的调度策略,分别对其进行改进,并通过遗传算法对系统矩阵周期调度表进行优化,之后利用Simulink中的Stateflow工具针对一般工业控制系统建立了TTCAN网络调度仿真平台,并对仿真平台进行优化,优化后的仿真平台较好地提高了网络系统带宽利用率,增大了总线通信量,降低了各传感器节点周期性消息的响应时间和非周期性消息的延时时间,从而改善了网络平台的通信实时性能.     

基于预测控制的网络时延补偿策略研究

针对网络控制系统(NCS)中的时延问题,在分析网络时延特性的基础上,本文提出对系统采用预测控制策略进行时延补偿.为克服网络控制系统中时钟不易精确同步的问题,该策略用易于测昔的网络往返时延代替不易单独测量的前向时延和后向时延,不但采用MATLAB/TrueTime仿真工具箱对实际系统进行了仿真研究,还使用网络实验控制平台对实际的电机控制系统进行了实验研究.仿真和实验结果表明,该策略可以对网络时延进行精确补偿,保证网络控制系统具有良好性能.     

网络控制系统中信息调度的研究进展

由于网络带宽的限制以及控制系统的时限要求，网络控制系统的性能不仅取决于控制算法的设计，而且取决于网络信息的调度，以实现各个网络节点资源分配。文中综述了网络控制系统中信息调度的研究进展，主要内容：首先比较了单处理器的任务调度与网络控制系统的信息调度；介绍了单处理器的RM和EDF两种实时调度算法以及多处理器的调度算法；讨论了调度的单独设计和调度与控制的共同设计；最后探讨了若干待解决的问题及发展趋势。     

基于鲁棒控制的NCS实验系统理论分析

本文针对已搭建的网络控制系统实验台,对其实验的展开进行理论分析。通过运用控制理论基础,设计和推导实验系统受控对象的传递函数。针对存在网络诱导时延、数据丢包和外部干扰的网络控制系统,利用鲁棒控制方法设计短时延的网络控制系统,设计与计算反馈控制率,以满足NCS的稳定鲁棒性和性能鲁棒性。仿真结果显示所设计的控制系统具有较好稳定鲁棒性和性能鲁棒性。     

基于时间窗口的网络控制系统调度算法

由于网络控制系统中各个控制设备共享物理传输介质,造成了控制设备争用总线的问题,从而引起了控制数据传输的延时,而反馈控制系统的稳定性能由环延时决定,需要研究一种调度算法对网络中消息的传输进行调度,使消息可以满足其实时性要求。该调度算法从控制系统稳定性能角度出发,利用控制环的最大允许环延时确定控制环的采样周期,同时基于时间窗口得出控制环中各个节点的起始传输时刻,最终确定了系统静态调度表的结构。最后分析了该调度算法在CAN总线应用中需解决的问题以及未来的研究工作。     

NDIS-based four-layer architecture for IEEE 802.11b with a virtual scheduling algorithm

This paper examines the feasibility of using the IEEE 802.11b protocol for wireless networked control systems (NCSs). The IEEE 802.11b protocol is not suitable for industrial networking because the medium access control method is contention-based CSMA/CA, which exhibits unstable performance with an unbounded delay distribution under heavy traffic. To avoid these limitations, we present a four-layer architecture for IEEE 802.11b based on the network driver interface specification (NDIS) combined with a virtual scheduling algorithm. We compared the performance of the NDIS-based wireless NCS to that of a conventional wireless NCS. Experimental results showed that the NDIS-based four-layer architecture for IEEE 802.11b is a very promising alternative for wireless industrial networking.     

Real-time random delay compensation with prediction-based digital redesign

Today’s technological demands require challenging control solutions such as real-time applications of Networked Control System (NCS). However, due to communication protocol and shared data bus, NCS experiences uncertain and unpredictable time delays in both input and output channels. These delays cause asynchronization between the controller and the plant thereby degrading the performance of closed-loop control systems. To address this problem, this paper proposes to utilize digital redesign technique to provide real-time random delay compensation.     

Performance evaluation of wireless networked control system via IEEE 802.15.4 with time-triggered CSMA/CA algorithm

This paper focuses on performance evaluation of wireless networked control system (NCS) via IEEE 802.15.4 with time-triggered contention-based carrier sensing multiple access with collision (CSMA/CA) algorithm to satisfy the industrial quality-of-service (QoS). Although the IEEE 802.15.4 is considered to a promising protocol for wireless NCS, its performance is not stable and its delay is not bounded under heavy traffic because its medium access control (MAC) is based on the contention-based CSMA/CA scheme. As an alternative approach to avoid these limitations, this paper presents a time-triggered CSMA/CA algorithm for IEEE 802.15.4 non-beacon mode that relies on a time division multiplexing access (TDMA) method. The time-triggered CSMA/CA algorithm for IEEE 802.15.4 non-beacon mode was implemented an experimental wireless NCS, and its control performance was compared with conventional CSMA/CA algorithm. Based on the experimental results, the time-triggered CSMA/CA algorithm is a feasible alternative for wireless NCS.     

Key Technology of Embedded System Implementation for Software-based CNC System

The software-based computer numerical control(CNC)system includes three types of tasks: periodic real-time tasks,aperiodic real-time tasks,and non-real-time tasks.The tasks are characterized by concurrency,hybridization,and correlation,which make system implementation difficult.The conventional scheduling algorithm can not meet the demands of system implementation in the software-based CNC system completely.The uncertainty factors when running real-time tasks affect control performance by degrading manufacturing accuracy as a result of system resource and processor use restrictions.To address the technical difficulty of embedded system implementation,a novel fuzzy feedback scheduling algorithm based on output jitter of key real-time tasks for a software-based CNC system is proposed.Time characteristics,such as sampling jitter,input-output jitter,and non-schedulability are discussed,followed by quantification through simulations of the impact of time characteristics on manufacturing accuracy.On the basis of this research,the scheduler architecture is designed,and then the algorithm table is calculated.When the system resource changes,the key periodic real-time tasks meet their deadlines by means of dynamically adjusting the task period.The simulated results show that the machining precision rises by an order of magnitude for the proposed scheduler in resource-constrained software-based CNC systems.Moreover,unlike conventional feedback scheduling methods,the algorithm in this paper does not rely on the availability of task execution times and is easy to implement while incurring only a small overhead.     

Sensor scheduling for relay-assisted wireless control systems with limited power resources

In this paper, we investigate the transmission scheduling problem for wireless control systems (WCSs) with limited power resources. Different from the existing works, for a discrete-time linear process, we consider a more practical WCS, where a relay is introduced into the framework for remote transmission and control. To achieve the best control performance of the system, we propose a global optimal offline scheduling algorithm. Then, based on ACK-feedback framework, two different online scheduling schemes are further designed respectively under the given power resources. Theoretically, we prove the superiority of online schedule to the offline one under the same energy budget. Simulations are conducted to demonstrate and verify the effectiveness of the proposed algorithms.     

制造企业生产计划调度与控制集成策略研究

传统的生产系统中,生产计划、调度与控制是分开进行的,生产信息的反馈周期长,生产调度缺乏必要的现场信息。通过分析生产系统的功能模型和信息模型,结合我国制造企业的实际情况,建立了生产管理系统的层式模块化结构。按照这种结构,构建企业的集成化生产管理系统,将会实现生产计划的实时调度以及生产过程的实时控制。实例证明,本文提出的方案是行之有效的。     

流程工业生产调度与控制集成系统数据库设计

根据流程工业生产调度与控制集成系统的应用需求,该文建立了实时数据库管理系统的体系结构,对实时数据库的管理对象、存储内容、表单结构及录入算法进行了探讨,并选用SQL Server2000提供的数据仓库解决方案建立了流程工业生产调度数据仓库系统,提供了调度知识获取与调度知识库的建立方案,为实现流程工业生产调度与控制系统的集成提供了一种新的数据存储与知识获取方法。