| Networked control system (NCS for short) is a control system wherein the control loop is closed via a communication network. The NCS has been widely employed in various areas. However, due to inherent problem of communication networks, the NCS always gets involved with network-induced delay, which may degrade the system performance or even make the system unstable. Therefore, it is of great theoretical and practical meanings to investigate the analysis and synthesis of NCS thoroughly.In this paper, the issues of network-induced delay analysis and modeling, predictor design, controller design, stability analysis, simulation system have been worked. The main contents of this thesis are as follows:First of all, analysis of network delay characteristics in NCS is worked. And based on the problem of current research methods, which is the lack of robustness and the over reliance on a fairly accurate mathematical model of plant, the linear active disturbance rejection control (LADRC for short) approach are proposed to control the NCS with time delay.Secondly, the theory and characteristics of LADRC are analyzed, and the predictor and modified LADRC controller are designed. Based on the transfer function representation of the LADRC approach based NCS with constant time delay, the frequency analysis of the system are shown to verify the system stability and robustness.Thirdly, according to the characteristics of time-varying time delays, the fuzzy logic approach is proposed as a viable addition to the modified ADRC approach. The control parameters change with the system error which caused by the time-varying delay, to improve the control performance.Finally, based on the MATLAB/Simulink and TrueTime toolbox, the effectiveness of the LADRC approaches is demonstrated by the simulation results of a network-based DC motor control system, and their excellent disturbance rejection ability and robustness are also demonstrated. |
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