Plant Modelling And Sliding Mode Control For Networked Control System

Feedback control systems wherein the control loops are closed through a real-time network are called networked control systems (NCSs). The NCSs are replacing the traditional point-to-point control systems that have not satisfied with new requirements. The networked control system has the advantages of sharing information resource, simple and fast actuation and maintenance, powerful system diagnosis, improving system flexibility and reliability. So it is attracting more and more attentions.The insertion of the communication network in the feedback control loop makes the analysis and design of a NCS more complex than before. When components of networked control systems exchange data, the limited bandwidth and weight capability lead to the information collide and re-transmit, which produce the delay. This delay is the main factor to degrade the performance of control systems. Meanwhile, because of the limit of data-packet capacity, the multiple-packet transmission is inevitable in NCS. As the basis of research, it is important to establish the model of a NCS.Considering the above, this thesis researches the NCS with multiple-packet transmission under considering delay longer than one sampling period. A method of sliding mode variable structure control is used to design controller with good performance. Firstly, the definition and feature of NCS are introduced. The reasons for occurring and influence of the network-induced delay, and current developments of NCS are proposed. Secondly, the model of NCS with single-packet and multiple-packet transmission under considering system noise and network-induced delay longer than one sampling are proposed. The sensor nodes are time-driven, while the controller nodes and actuator ones are event-driven in the NCS. Afterward, a method of sliding mode variable structure control is used to compensate the state delay .The sliding mode controller based on above method has advantage of robustness for parameter variations and external disturbances, which guarantees closed-loop systems stability and robustness.Meanwhile, the sliding predictive controller with good performance is designed for NCS with time delays from sensor to controller and from controller to actuator. Finally, the development of networked control systems theory is forecasted, and research in the future is analyzed.