Output Feedback Control Of Networked Control Systems

With the rapid development of network technologies and the extension of the size of control systems, networked control systems (NCSs) appeared and became a new research field in the automation. The so-called NCS is a feedback control system wherein the control loop is closed through real-time network. It has a great deal of advantages such as shared resources of information, reduced system wiring, facility of system extending and maintenance, higher reliability and flexibility, and so on. NCSs are the collaboration of three engineering fields, computer engineering, communication engineering and control engineering, and have become the new direction of modern industry. However, because of the introduction of the network in traditional control system, it is inevitable that there exists networked-induced delays, data packet dropouts, message collision and time sequence confusion etc. These are main factors to degrade the performance of control systems. So the NCS brings a new challenge and opportunity to the investigation of control theory.In this thesis, the research focuses on the output feedback control of the networked control system. Main achievements are as follows:First of all, the thesis considers the NCSs with input delays and data dropouts (from the sensor to the controller) and sets up a discrete-time-switched system model. In terms of the given model, sufficient condition for asymptotical stability is derived via Lyapunov stability theory in the form of linear matrix inequalities. A switched output feedback controller can be designed. Numerical example demonstrates the effectiveness of the proposed methods.Next, the modeling and control of a class of NCSs with packet dropouts and delays is discussed. For the cases that there may be packet dropouts and delays which exist both between sensor and controller and between controller and actuator in the communication network, and the delay is shorter than one sampling period. The NCSs are exponential stable by designing the observer-based output feedback controller based on LMI technique. By using the asynchronous dynamical systems approach and the average dwell-time method, the precise relation between the packet dropout rate and the stability of the closed-loop NCS is presented. Numerical example validates the effectiveness of the proposed results.Finally, NCS with random communication delays and data packet dropouts is studied. The random delays and data dropouts exist in the forward and backward channels, and are modeled as a binary switching sequence satisfying a Bernoulli distribution. In terms of matrix inequalities, a sufficient condition is given for the existence of a dynamic output feedback controller which makes the closed-loop system asymptotically stable with a prescribed H-infinity performance. The thesis solves the matrix inequalities by applying to the sequentially linear programming matrix method (SLPMM). Simulation example illustrates the validity of the proposed approach.