【作者】 李然；

【导师】 宗群；

【作者基本信息】 天津大学 ， 控制理论与控制工程， 2006， 硕士

【摘要】 网络控制系统(Networked Control Systems)是一类通过有线/无线通信网络将传感器、控制器和执行器进行互联的分布式控制系统,网络化提高了控制系统的效率、灵活性和可靠性,降低了系统成本,但也给控制系统带来了新的问题,带宽约束(Bandwidth Constraints)就是其中之一。由于网络带宽不可能无限大,如果没有足够的网络带宽,控制信息就无法及时有效的传输,从而导致系统性能恶化甚至造成系统不稳定。合理分配网络节点的带宽使用、减少网络中所需要传输的信息量是解决带宽约束问题的有效方法,但目前有关如何减少包传输网络数据量的研究比较少,有必要进行进一步探索。通信逻辑(Communication Logic)是解决带宽约束问题的一种有效方法。首先,针对通信逻辑的原理和研究现状进行了总结,分析了通信逻辑研究的关键问题和存在不足。以线性时不变过程为对象,提出了一种新型的、基于系统状态的随机通信逻辑,它由一个状态依赖泊松过程决定,设计了具有随机通信逻辑的智能传感器节点并应用于一般结构的状态反馈网络控制系统。为了分析通信逻辑在系统中所起的作用,采用Bounulli过程刻画网络丢包,建立了具有随机通信逻辑的网络控制系统模型。基于该模型,结合随机稳定性理论、带时倚强度泊松过程相关原理进一步证明了系统保持均方渐近稳定的充分条件,并对具有随机通信逻辑的输出反馈网络控制系统稳定性进行了探讨。最后利用Matlab/Simulink仿真工具对建立的具有随机通信逻辑的系统模型进行仿真验证,比较了随机通信逻辑和周期通信逻辑对系统性能的影响,进一步分析了采用常值强度和状态依赖强度时的随机通信逻辑的特点和性能,验证了基于状态依赖泊松过程的随机通信逻辑可以有效减少网络节点的带宽使用这一理论结果。仿真结果表明,通过在网络控制系统中引入基于系统状态的随机通信逻辑,可以合理的确定传感器选择合适的时间传送系统状态数据,从而减少网络节点对网络带宽的使用,有效的降低网络中传输的数据量,同时保证系统稳定和一定的系统性能。更多还原

【Abstract】 Networked Control Systems(NCS) belongs to distributed control systems which the sensors, controllers and actuators are connected by a shared communication network. This type of feedback control systems where the control loops are closed through a network is more efficient, flexible, and reliable with less cost. However, network also brings some new problems, such as network delay, dropouts, bandwidth contraints, etc. The remote controller can’t get enough information when there are many nodes on the network while the bandwidth is limited, and that will result degradation of system performance, even leads to instability. Dynamicly allocating the bandwidth usage and reducing the amount of the transmitted data is effective to solve the problem of bandwidth constraints, but no enough attention has been paid.Communication Logic is an effective key method for the bandwidth constraints problem in Networked Control Systems. First we introduce the principle idea of communication logic and summarize the recent research paper on it. The work is focused on linear time invariant processes and a new communication logic, which is built on a State Dependent Poisson Process, is proposed and combined into a new type of smart sensor, to determine when the sensor should transmite data to remote controllor. In order to analyze the influence of Communication Logic as well as the whole system, we set up the model of the states-feedback networked control systems with data dropouts described through Bounulli Process, and study the mean square asymptotically stability of systems by using the stochastic theory about Poisson Process with time varying density. Sufficient conditions are derived through mathematic deduction. The stability for output-feedback control systems with Communication Logic is also discussed later. Finally, theoretical results of NCS with the new communication logic are validated by Matlab/Simulink tools. The stochastic communication logic based on states of systems is compared with periodic commnunication logic through simulation and the result shows that the former can achieve better system performance.It turns out that the communication logic, which is based on State Dependent Poisson Process, can determine the appropriate time for sensors to send the data and reduce the usage of network bandwidth, meanwhile assure the stability and performence for Networked Control Systemes.更多还原