【作者】 方来华；

【导师】 吴爱国；

【作者基本信息】 天津大学 ， 电力电子与电力传动， 2005， 博士

【摘要】 网络控制系统(NCS)是控制科学、计算机技术及网络通讯等技术发展和综合的产物。NCS具有连线少、灵活性强、便于故障诊断和信息资源共享等众多优点,但控制系统引入网络后,由于带宽有限、分时复用、数据传输路径不确定等都会导致信息传输中的等待、阻塞及丢包等现象,不可避免地产生时延。这些受负载、通信协议等影响的时延,无论固定或时变还是有界或无界,都会不同程度影响控制系统性能,甚至导致系统失稳,这给NCS分析、设计和控制带来很大困难。因此,如何针对NCS自身特点,应用已有控制理论分析设计方法或建立新的理论和方法来解决NCS中存在的问题,成为人们研究的一个热点。本文对NCS中实时性、采样选择、时延等问题进行了分析,讨论了影响实时性因素和改善实时性方法,研究了采样和时延对系统性能影响。在考虑系统扰动基础上,建立了更具一般性的多输入多输出线性NCS连续时间模型。研究了四种不同驱动模式下,信息传输的时序以及具有任意有界时延NCS的离散模型和统一模型,建立了任意有界时延的MIMO网络控制系统离散模型,拓展了模型的适用范围。针对确定时延NCS,给出了基于输出反馈的状态观测器和控制器设计,以保证闭环NCS稳定性和良好的控制性能。给出了滑模变结构时滞补偿控制算法,提出了一种具有补偿控制时延的滑模面,所设计的滑模控制器保证了闭环系统的稳定性,得到了使系统稳定的最大允许网络时延,仿真表明了方法的有效性。针对具有不确定性闭环NCS,推导了时延相关和时延独立的稳定性条件,得到在时延相关情况下使不确定性闭环NCS稳定的允许时延上界。针对时变时延NCS,将其视为离散跳变系统,利用离散跳变系统分析方法给出NCS稳定的充要条件。针对变采样和时延NCS,基于区间代数和矩阵集合稳定性理论,通过构建一个更宽松的区间系统来分析原系统的稳定性,所给稳定性分析方法简单有效。为抑制时延对NCS性能影响,提出了模糊免疫自调整PID控制方法,所设计控制器具有较强的适应性,可使NCS获得更好动态特性。在时变时延仅存在反馈通道和时延同时存在反馈通道及前向通道这两种情况下,对具有不确定性的闭环NCS稳定性进行了分析,以线性矩阵不等式的形式给出了系统稳定性条件。对于存在丢包和变时延的NCS,在信息单包传输时,推导了时延无界/有界情况下闭环NCS渐进稳定的条件;在多包传输情况下,得到了时延变化率在不同情况下的NCS的渐进稳定的充分条件。更多还原

【Abstract】 Networked Control System (NCS) is an outcome of development and integration of control science, computer technology, network communication and other technologies. NCS reduces complexity in wiring connection, provides ease in maintenance and enables information shared among users. When network is introduced in the system, delay or packet dropout is induced by waiting, collision and congestion because of bandwidth constraint, time sharing multiplexing, uncertainty in transmission path, etc. The delay, which is affected by network load, communication protocol and some other factors, whether constant, time-varying, bounded or unbounded, can influence control performance, it can even cause system instability, which brings difficulties to analysis and design of NCS. Therefore, how to use existing control theory approaches or create new theory and means to solve the problems in NCS is a hot issue for researchers, pointing at NCS characteristics.Analysis of real-time characteristic, sampling period choice and time delay in NCS is made, factors that influence real-time characteristics and methods to reduce delay are discussed. Impact of sampling period and delay on system performance is also studied. A general continuous model of multiple inputs and multiple outputs (MIMO) linear networked control system is built, considering system disturbance. Graphs of time sequence of information transmission and discrete models of NCS with any bounded delay are constructed at four different driven modes. Discrete models of MIMO networked control system with any bounded delay are also established, which extends the range of model application.For NCS with deterministic delay, design of controller and state observer based on output feedback is presented, which guarantees stability of close-loop system and good performance. Sliding mode variable structure control scheme with delay compensation is given,then a sliding manifold that compensates control delay is introduced, the designed sliding controller guarantees the stability of closed loop system, and upper bound of allowed delay is given, simulation shows the effectiveness of the approach. Stability analysis criteria of delay-dependent and delay-independent for non-deterministic closed-loop NCS is derived, the maximum allowable network-induced delay for delay-dependent NCS with uncertainty is obtained.For NCS with time-varying delay, it is considered as a discrete time jump system,更多还原