Modeling and Stability Analysis of Networked Control System with Time-delay
|Course||Operational Research and Cybernetics|
|Keywords||Networked control system delay packet loss stability system modeling|
With extensive usage of computer networks and continuous development of networked technology, the structure of control system is changing. The system, using a dedicated or public computer networked control system to replace the traditional point-to-point structure and realizing mutual transmission of control information among sensors, controllers, actuators and other system components, is called networked control system. The research on networked control system is fast becoming a cutting-edge topic of international control field. Meanwhile, it has important theoretical meanings and extensive application prospects. However, due to the involvement of networks, there is inevitably network-induced delay, packet loss, packet disorder in the control loop, which will affect the performance of the system. So, in this paper, the stability of networked control system with the first two issues is studied.In order to study the issue of system stability, this paper will be divided into two parts: delay less than a sampling period and greater than a sampling period.When delay is less than a sampling period, first of all, the networked control system with disturbances and random time-delay is analyzed and modeled. Then, based on Lyapunov stability theory and robust control theory, by using the linear matrix inequality approach, the sufficient condition of the system which is asymptotic stable and meets the performance requirements is given under the conditions of disturbance. Next, random time-delay networked control system with packet loss is studied; the system is modeled to be a switch system that consists of four time-varying sub-systems. In the sub-systems, switch rate is unknown, and then the system matrix is structurally decomposed, thus the stability of entire system is analyzed by using the four nominal systems and the sufficient asymptotic stability condition of the closed-loop system is given.When delay is greater than a sampling period, firstly, the stability of networked control systems with uncertain long time delay is studied. In connection with characteristics of NCS system such as time-varying and long time delay, the system is modeled to be a linear discrete-time system with uncertainty, and the sufficient asymptotic stability condition of the closed-loop system is given combined with the Lyapunov function method and linear matrix inequality approach. Then, the networked control system with packet loss and long time delay is analyzed in detail and modeled; next, the sufficient conditions of system exponent stability in state feedback and output feedback are respectively given, and the validity of the conclusions is verified by using the simulation examples.At last, research contents of this paper are summarized and the future work is pointed out.