Network Control System Stability Analysis

Networked control systems (NCSs) are systems that sensors, actuators and controllers implemented as the network nodes by a communication network. The main characteristic of the control system with feedback control loop is that the loop is connected through the network channel.The control model of the networked control system is no longer the traditional point-to-point connections, but sensors, actuators and controllers as the nodes directly connected to the network. The rapid popularization of the field-bus, high-speed Ethernet and public communication network technology, the rapid digital development of the sensors, actuators and electromechanical transformation devices, and the development of the complex theory of control system promoted the formation of networked control system. In addition to the obviously engineering significance, the theory of the networked control system is also challenging. The networked control systems have many problems that the traditional control systems have not encountered, such as the information transmission delay (delay is uncertain (randomness) and time-varying), the disorder and dropping of the data series caused by the congestion of the transmission channels, all these have greatly inspired people's enthusiasm of the networked control system, and it is rapidly becoming one of the areas of the most concern of the control area.For the networked control system, this paper relates to the following studies:(i) On the basis of the model-based networked control system proposed by Montestruque, we analyze the system with network transmission delay and non-fixed sampling period, and give the corresponding model-based output feedback networked control system model with the observations. If the network transmission delay is less than the minimum sampling period, we think that there is no data packet dropping occurred, if the network transmission delay is more than the sampling period of that moment, we think that the data dropping is occurred. Against the different types of model-based networked control systems with no packet dropping and packet dropping, we analyze the stability and give the sufficient conditions of the asymptotically stable for the closed-loop system, respectively;(ii) Against the random networked control system with white noise disturbance and known data packet dropping probability, we analyze its mean square stability; in ensuring the stability of the control system, we analyze its maximum allowable packet dropping probability, and give the algorithm to get the largest value of the data packet dropping probability.Main research results published in Journal of Qingdao University (engineering & technology edition).The main contents of this thesis are as follows:Chapter 1 gives the simple review of the developing of the networked control system. Chapter 2 summarizes the development status of the model-based networked control system, as well as generalized networked control system with external perturbations, gives some prior knowledge of the linear networked control system. Chapter 3 aims at the networked control system with no data packet dropping and packet dropping respectively, analyzes the stability of the model-based networked control system by using Lyapunov stability theory, and gives the sufficient conditions of the asymptotic stability of the control system respectively. Chapter 4 againsts the random networked control system with white noise disturbance, data packet dropping probability only in the network transmission and without time delay, gives the algorithm to get the maximum allowable packet dropping probability in ensuring the stability of the system. Chapter 3 and 4 give the results of in-depth theoretical analysis, and give examples demonstrating the correctness of the theory respectively. Chapter 5 sums up the research works, and proposes the problems that will continue to study in further.