摘要
网络控制系统是一种通过实时网络而构成闭环的分布式反馈控制系统,其中控制器,传感器,执行器各节点通过一条共享的网络来交换信息。网络控制系统集成了计算机技术、通信技术和控制理论,是一门新兴的技术并且正成为现代工业生产的发展方向。
本文首先对网络控制系统的研究现状进行了总结,对网络控制系统中普遍存在的网络诱导时延特性进行了分析,阐述了网络控制系统中网络诱导时延产生的原因及其组成,不同节点驱动方式下网络时延的特性以及网络诱导时延对控制系统稳定性的影响。
接着论述了网络控制系统在单个数据包传输且随机时延小于一个采样周期的情况下,基于全维状态观测器的控制器设计方法,证实了这种补偿方法的有效性。
考虑到时延的随机性,把随机最优控制(LQG)理论应用到网络控制系统当中。通过建立增广状态系统,使用贝尔曼动态规划法推导出了NCS的随机最优状态反馈控制规律,并通过仿真实验对该算法的有效性进行了验证。
最后,针对数据包丢失和时延同时存在的这类系统,建立了带有补偿估计器的NCS模型。当数据包发生丢失时,通过数据包丢失估计补偿器的信息来更新控制器的输出,对被控对象进行控制。仿真结果表明,带补偿器和估计器的网络控制系统能有效降低时延和丢包对系统的影响,提高系统的稳定性能。
Networked Control System (NCS) is a special distributed feedback control system where in the control system loops are closed through real-time network. In the NCS, controller, sensor and actuator nodes exchange information through a shared network. Integrating computer technology, communication technology and control theory, NCS is an emerging technology and becoming future trend of modern industry.
Firstly we summarize the research actuality of NCSs, analyze the characteristic of network-induced time delay universally in NCSs and expound what is network-induced time delay made up of, what causes it coming into being, the characteristic of network -induced time delay in different kinds of the point driven form and effect of stability of control systems caused by network-induced time delay.
Then under condition that time delay is smaller than a sampling period in single-packet transmission we have suggested design procedures of entire thinking state observer and confirmed the validity of this compensatory method.
Considering a random delay, stochastic optimal control theory was applied to NCS. An augmented system of NCS is firstly built up, and an optimal state feedback with Bellman dynamic programming is deduced. And some simulations are done to validate the effectiveness of this algorithm.
Finally, the model of compensation and estimation for the networked control system with time-delay and data packet dropout is designed. When the data packet is lost, controlling object is realized through designing estimation compensator for data packet dropout of the system and using its information to update the output of the controller. Simulation results prove that the networked control system with compensator and estimator can effectively reduce time-delay and the impact of date packet dropout on the system, and it also can effectively improve the stability performance of control systems. Thus, it is verified that the design is feasible and effective.
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