【作者】 陈惠英；

【导师】 王万良；

【作者基本信息】 浙江工业大学 ， 控制理论与控制工程， 2009， 博士

【摘要】 网络控制系统(NCS)是将传感器、控制器、执行器等部件通过实时网络形成闭环的反馈控制系统,是基于网络的全分布式控制系统。这类新型的控制系统近年来得到了广泛关注。与传统的点对点控制系统相比,网络控制系统具有系统连线少、可靠性高、易于系统扩展以及能够实现信息资源的共享等优点。因此,在众多领域得到了广泛地应用。但实际网络控制系统中,常常受到网络有限带宽资源、网络通信协议等各种网络条件制约,使得网络控制系统中存在如网络诱导时延、数据包的多包传输及丢失、网络通信约束、网络调度等许多新的问题。这些问题的存在使网络控制系统的分析和设计变得异常复杂。本文主要以受带宽约束或通信协议约束的NCS,统称为资源受限的NCS为研究对象。从系统的建模和控制、网络资源的调度与控制协同设计等方面展开了研究。主要研究内容如下:对于具有通信约束的NCS,应用通信序列的概念,同时考虑不确定短时延的影响,通过将时延的不确定性等效为系统参数的不确定性,建立了一类具有参数不确定的集成信息调度与控制的离散周期切换系统。得到了这类系统信息可调度的条件和闭环系统渐近稳定的条件,并基于LMI方法给出了在一定的周期通信序列下的控制器参数化设计方法。针对具有短时延的多包传输网络控制系统,研究了数据包传输采用动态调度策略时系统的建模与控制问题。首先假定数据包传输具有Markov特性,其中数据包的传输考虑了丢包的情况,建立了集时延、丢包及多包传输多问题综合的模型。并获得了使系统随机稳定的条件和控制器的设计方法。其次,在数据包传输顺序随机不确定的情况下,引入了补偿器来补偿多包传输中部分数据包丢失对系统性能的影响,对多包传输中未能更新的数据用补偿器的预估状态来代替。在此基础上建立了一类离散随机切换系统模型,并对其稳定性进行了分析。针对NCS的信息速率约束问题,提出一种基于误差阈值的确定性通信调度策略来控制网络节点数据的发送,并将其应用于基于模型的网络控制系统(MB-NCS)中,建立了具有通信调度功能的MB-NCS模型。进一步对该系统的稳定性进行了分析,给出了系统中被控对象状态的稳定域范围。仿真表明该方法在保证系统获得较好性能的同时,数据包的传送次数大大减少了,有效减轻了带宽约束对系统性能的影响。研究了具有时变有界采样周期和时延的NCS的建模与控制问题,将其建模成一类离散动态区间系统。在此基础上,分别研究了系统的镇定、保性能控制及H∞控制问题,并给出了各控制器的设计方法。为变采样调度方法的研究提供了很好的理论依据和支持。针对带宽受限及负载可变的动态工作环境,设计了一个动态反馈调度器,基于LS SVM方法实现对网络可用带宽资源的预测;建立了一个基于模糊逻辑的回路控制性能评价指标;带宽管理器和优先级配置器以该性能指标为依据对预测到的可用带宽资源进行动态分配。通过与基于误差的带宽及优先级分配方法比较,结果表明本文提出方法优化了系统的控制性能,并在不确定运行环境中具有更好的适应性。更多还原

【Abstract】 Feedback control systems wherein the control system components(sensors, controller, actuator, etc)are closed through a real-time network are called networked control systems(NCS),which are fully spatially distributed systems. A great deal of attention has been focused on this class of control systems in recent years. Compared with conventional point to point control systems, NCS have advantages of less wires, high reliability, good flexibility and share of information resources, etc.Bacause of these distinctive benefits,typical application of these systems ranges over various fields,such as automotive,mobile robotics,advanced aircraft,and so on. However, in real networked control systems, there often exist various of network restrictions such as limited bandwidth resource, network communication protocol etc, which result to incur some new issues such as network-induced time delay,multiple-packet transimission and dropping network packets,network communication constraints,network scheduling etc. This new problems make the analysis and design of NCS complex.In this dissertation, we focus on the networked control systems suffering to bandwidth constraints or communication protocol constraints. Due to this class of research plants, some aspects such as system modeling and control, co-design of network scheduling and control are studied. The main achievements are as follows:Firstly, for the networked control system with communication constraints, the notion of communication sequence is employed. At the same time, considering the influence of uncertain short time delay, the NCS is modeled as a discrete switching system with uncertainty, which integrates information scheduling and control. The schedulability conditions and asymptotic stability results of this closed loop system are discussed in detail. The solution of control law is also given under a certain periodic communication sequence by means of linear matrix inequalities(LMI) approach.Secondly, for the networked control systems with multi-packet transmission and uncertain short time delay, system modeling and control problem is studied on the condition that data packet transmission using dynamic scheduling strategy. In the first place, supposing that the packet transmission process has the Markov characteristic which also contains the case of data dropouts, the synthetic model which considering the issuses of time delay, data dropouts and multiple-packet transmission is constructed. The stochastic stability condition and controller design method are also obtained. In the second place, for the case of uncertain packet transmission sequence, a compensator is introduced to compensate the effect of part of data dropouts in the process of multiple-packet transmission. Based on this, the NCS is modeled as a discrete stochastic switching system, and the stability of the system is also analyzed.Thirdly, due to the information rate constraints problem in the networked control system, a deterministic communication scheduling strategy is proposed to control data transmission of network nodes and is applied in the MB-NCS, the model of MB-NCS with communication scheduling role is constructed. Furthermore, the stability of the system is analyzed and the stability region of the plant states is provided. Simulation result shows that under obtaining good system performance, the introduced communication scheduling strategy reduces the data transmission times obviously,which lightens the effects of bandwidth constraints on system performance effectively.Fourthly, the modeling and control problem is studied for the networked control system with time-varying bounded sampling period and time delay, it is modeled as a class of discrete dynamic interval system. Based on this, we study the problems of system stability, guaranteed cost control and H_∞control, each controller design method is also given. The proposed method provides a good theory guide for the research of time-varying period scheduling.Finally, for the networked control system with limited bandwidth and flexible workload, a dynamic feedback scheduling strategy is proposed. The available bandwidth is predicted by using LS_SVM approach, the performance indices of the control loops are proposed based on fuzzy logic control technique. And the predicted network bandwidth is dynamically allocated by the bandwidth manager and priority assigner in terms of the control performance indices. By comparing to the error-based bandwidth and priority allocation method, the results of simulation highlight that the proposed algorithm can optimize the performance of control loop and has more flexible in uncertain running conditions.更多还原