Stability Design For Networked Control System

In general, networked control system (NCS), also called internet-based control system, indicate that feedback control system wherein the control loops are closed through a real-time network. The primary nature of an NCS is that information (such as reference input, plant output, control signal, etc.) is exchanged among control system components such as sensors, controller, actuators, etc. This networked architecture has many advantages compared to the traditional point-to-point design including low cost of installation, ease of maintenance and higher reliability, etc. However, the network delay in NCS occurs when sensors, actuators, and controllers exchange data across the network. This network delay can degrade the performance and can even destabilize the system. Therefore, to ensure stability of NCS is an important issue in NCS design. In this paper, by constructing uncertain discrete system model and hybrid system model, the stability of NCS is studied deeply using of many techniques such as matrix norm, matrix measure, Lyapunov Function and Linear Matrix Inequality (LMI), etc.By using matrix measure and matrix norm, this paper presents how to simplify a complex and high order system into one-order system. Based on that, the controller for the system involves parameter uncertainties, sensor failures, actuator failures is designed, which makes system attain stable fault-tolerance control.Based on uncertain discrete system model, the robust non-fragile suboptimal controller is designed in terms of Lyapunov Function, LMI and interval matrices techniques. The robust non-fragile suboptimal controller which exits maximum-variable interval can be obtained by solving a convex optimization issue.The stability problem of NCS with data packet dropout is discussed based on dynamic system-controller. The NCS is modeled as a switched system with 0 or 1 random variable. Then, the dynamic system-controller ensure that NCS is asymptotically stable are designed, which involves solving LMIs.The robust observer-controller for NCS is studied also. The NCS is modeled as an uncertain discrete system and observer-controller is constructed for the uncertain discrete system. By using the robust control theories and the LMI techniques, the observer and controller are designed easily in terms of an algebraic Riccati equation and linear matrix inequality.For the plan with delay or with delay and equality constraint, the NCS is modeled as a hybrid system or a neutral hybrid system, respectively. Then, the Maximum Allowable Transfer Interval (MATI), the Lyapunov-krasovskii Function, and LMI methods are used to derive some sufficient conditions, which can guarantee that the NCSs are asymptotically stable. In terms of solving LMIs, the controller and the MATI are obtained easily. The simulation example illustrate the MATI is much less conservative than the existing methods. The MATI can be used as the rule to determine data sampling period and the Maximum Allowable Delay Bound (MADB). Furthermore, based on the model of hybrid system, the guaranteed cost controller is researched also.Finally, the problem of continuously dynamic output feedback stabilizing controllers for NCS is studied. Supposed that the network induced delay is random and less than the sampling period, the plan with delay is modeled as a hybrid system. Then, the continuously dynamic output feedback controller is constructed easily in terms of solving linear matrix inequalities.In each section, we show also example and simulation result for each research. Finally, we summarize the work and discuss future directions.