Feedback Control For A Class Of Networked Control Systems With Packet Dropouts And Time Delays

The rapid developments of computer technology, control technology, network technology and communication technology make networked control systems (NCSs) an important research area in modern control theory. Networked control systems have many advantages such as low cost, easy to extend, resource sharing and flexible structure. Due to the unreliability of communication network, it inevitably brings many problems such as transmission delays, packet dropouts and communication constraints, which directly affect the performance of the systems. How to decrease the influence of that these problems on networked control systems has theoretical and practical significance.In this thesis, we study the problem of feedback control of networked control systems with packet dropouts and time delays. The main results are summarized as follows:Firstly, the problem of the observer-based output feedback control of networked control systems with twin-channel packet dropouts and short time delays is studied, in which we assume that the sensor, the controller and the actuator are all time-driven and synchronized with the same sampling period. Then, the dynamics of closed-loop networked control systems can be described as a class of discrete-time Markov jump liner systems with four modes. Combing the linear matrix inequality method, we use the stochastic system theory to discuss the stochastic stability of the systems. In the end, we also design the output feedback controller based on observer.Secondly, on the basis of the study above, we consider a class of networked control systems with twin-channel packet dropouts and time-varying delays. When packet dropouts happen, the controller and the actuator will adopt the keep-input strategy, and we describe the discredited closed-loop networked control systems as a class of discrete-time switched delay systems. The stable subsystems describe the situations when packets are transmitted successfully; while the others describe the situations when packets fail. Then using the linearmatrix inequality method, we give exponential stability conditions by the switched delay systems theory and the average dwell time method. Furthermore, we also analyze the relationship between the max allowed packet dropouts’ rate and the exponential stability of the system. Finally, we give the design of the state feedback controller.Finally, we summarize the results of this thesis, with the further research problems of networked control systems discussed.