H_∞ Control For NCS With Measurement Data Dropouts And Long Delay

With the increasing integration between computer technology, network communication technology, control technology and some other academic fields,networked control system(NCS)has been brought into being over the last decade. Networked control system has a great many advantages when compared with traditional control system, such as low cost, easy maintenance methods and high reliability and flexibility and so on,so that it has been applied to all kinds of fields in a large scale. However, when network is utilized as the transmission medium, some problems will inevitably happen, such as network delay, data loss and so on. The performance of control systems can be seriously diminished when these problems happen. In addition, all of the natural and realistic systems are basically nonlinear systems. At present, for the research of network delay and data loss problem of networked control systems, most existing achievements are built on the premise of linear systems and systems with short delay. In this paper, a controller design problem is researched for the linear NCS with long delay and measurement data dropouts and nonlinear NCS with long delay and measurement data dropouts. The major points of this paper are shown as follows:(1) A class of linear discrete-time system with both measurement data dropouts and long network-induced delay is studied,the data packet dropouts are modeled as a Bernoulli random binary switching sequence. The probability of the data packet dropouts is assumed to be known and the network-induced delay of system is longer than a sampling period. When the system state can be directly measured, a state feedback controller is proposed to make the whole closed-loop system satisfy mean square exponential stability and achieve the prescribed H_∞ performance. When the system state can not be directly measured, an observer-based controller is proposed to make the whole closed-loop system satisfy mean square exponential stability and achieve the prescribed H_∞ performance. Sufficient conditions are derived for the existence of controller through Lyapunov stability theory and linear matrix inequality method. Numerical examples are also provided to prove the validity of the control method.(2) A class of uncertain linear discrete system with both measurement data dropouts and long system one step delay is studied, the data packet dropouts are modeled as a Bernoulli random binary switching sequence. The probability of the data packet dropouts is assumed to be known and the uncertainty of the system satisfies prescribed condition. When the system state can be directlymeasured, a state feedback controller is proposed to make the whole closed-loop system satisfy mean square exponential stability and achieve the prescribed H_∞ performance. When the system state can not be directly measured, an observer-based controller is proposed to make the whole closed-loop system satisfy mean square exponential stability and achieve the prescribed H_∞ performance. Sufficient conditions are derived for the existence of controller through Lyapunov stability theory and linear matrix inequality method. Numerical examples are also provided to prove the validity of the control method.(3) A class of nonlinear discrete-time system with both measurement data dropouts and long system one step delay,the data packet dropouts are modeled as a Bernoulli random binary switching sequence. The probability of the data packet dropouts is assumed to be known and the nonlinear system satisfies Lipschitz condition. When the system state can be directly measured, a state feedback controller is proposed to make the whole closed-loop system satisfy mean square exponential stability and achieve the prescribed H_∞performance. When the system state can not be directly measured, an observer-based controller is proposed to make the whole closed-loop system satisfy mean square exponential stability and achieve the prescribed H_∞ performance. Sufficient conditions are derived for the existence of controller through Lyapunov stability theory and linear matrix inequality method. Numerical examples are also provided to prove the validity of the control method.