The Study Of Control Methods For Networked Control Systems With Time-delay And Uncertainty

The networked control system (NCS) is a kind of closed-loop feedback control system, which is built by use of a real-time networking. Compared to traditional point-to-point control system, the network control system has fewer connections, low-cost, shared resources, as well as ease of installation and maintenance advantages. However, while the introduction of the network offers many advantages, due to the bandwidth limitations of the network itself, as well as the packet loss, timing disorder and other issues caused by the network running state, coupled with the time delay networking environment, there will inevitably be new challenges brought into the traditional control theory. Therefore, it is necessary to appropriately improve existing control theory and control methods to adapt to the normal operation of the control system in the network environment. Moreover, in the daily production and life, the network control system has been in the field of equipment manufacturing, transportation, long-range video medical treatment, and defense and military and aerospace, etc. have been increasingly widely used.In this paper, the controlled object was to be described as a class of linear time-invariant system with the steady state delay and parameter uncertainties, and to the real-time status of the network, some factors were taken into account appropriately, such as the network-induced delay, packets loss and out-of-order packets, as well as external interference, making the model more close to reality. Based on the built control model, we considered several common control method, including robust control, guaranteed cost control, fault-tolerant control and robust H∞control, through the use of Lyapunov stability theory, by means of linear matrix inequalities (LMI) approach, we got the sufficient condition of system meeting the asymptotical stability and guaranteeing a certain performance index, and based on the state feedback control strategy, we attained the corresponding designing method for control law with less conservation. This article discussed the following major elements:First, we studied the robust control problem of the networked control system. Based on the establishment of the controlled object model, making use of Lyapunov stability theory to prove a sufficient condition for the robust stability, while taking advantage of the linear matrix inequality (LMI) approach, a robust stable control law design method was given.Then we studied the robust guaranteed cost control problem of the networked control system. On the premise of the system satisfying the asymptotic stability, the problem of how to design a system with a guaranteed cost controller was discussed. Based on the performance index proposed by the system model, by choosing a suitable Lyapunov function, via Lyapunov stability theory and LMI approach, we got a guaranteed cost control law.After that, we studied the fault-tolerant control problem of the networked control system. Considering that the actuator may be failure because of malfunction, further improving the system model, using the Lyapunov stability theory and LMI approach, a malfunction matrix was introduced. And based on the state feedback control strategy, we deduced the sufficient condition that the system remaining asymptotic stability, as well as meeting certain controlling performance index, and got a kind of design method to the optimal guaranteed cost control law.Finally, we studied the problem of robust H∞control of the networked control system. For the presence of external disturbances with finite energy on the basis of the existing model, first by Lyapunov stability theory and LMI approach proving the sufficient condition that the system satisfies the robust stability, and then using the condition to obtain the way to design H∞robust controller.