On Time-delay Compensation And Stability Of Networked Control Systems

Networked control systems (NCS) are distributed feedback control systems whose sensors, actuators, and control units are connected through communication networks. However, the information transmitted through the limited bandwidth and weight capability will result in the information collision and retransmission. Time-delays in transmission are unavoidable. This thesis mainly studies the time delays and the effective control methods which are applied to networked control systems with time delays.First, the concept and research background of networked control systems and the basic problems in networked control systems are presented. Based on the network-induced delay studied in this thesis, the present situation of the network-induced delay is introduced.Second, based on the causes of the network-induced delay, the influence of different driven means of node points on the network-induced delay is analyzed. Meanwhile the models of NCS under different conditions are presented, and the influence of network-induced delay on the performance of NCS delay is analyzed.Third, for the NCS with short time delay, based on the prediction of improved state observer, the time delay between the sensor and the controller is compensated. The simulation demonstrates that this method can effectively compensate the time delay between the sensor and the controller, and ensure the good performance of networked control systems; for the NCS with long time delay, the design of controller based on LMI is discussed; for the network with transmission delay larger than one sampling period and the data packet dropout, the NCS is modeled as an asynchronous dynamical system and the sufficient condition of exponential stability for the networked control systems is presented based on the theory of asynchronous dynamical system. Meanwhile the state feedback controller can be solved by a set of matrix inequalities. The simulation demonstrates the effectiveness of the proposed method of the proposed method. Finally, the development of networked control systems theory is forecasted, and research direction in the future is pointed out.