Real Time Research Of Temperature-Control NCS Based On Variable Structure Smith Predict Fuzzy PID

With the developing and combining of traditional control methods and network communi-cation technology, Networked control systems (NCS) appeared, it made geographically disper-sed controller nodes, actuator nodes, sensor nodes connect together through communication networks, realized data communication between them. The appearing of NCS adequately indicated the networking,distribution,integration and node intelligence of control systems'de-velopment direction. But because of the introduction of networks, inevitablely bring some problems:like uncertain network delay, mainly desplayed in delay randomness and delay variability. That closely have effects with network architecture, communication protocol, network load number. The existence of transmission delay will have an effect on the control quality of networked control systems, when transmission delay seriouly or even cause systems instability. If the plant was also containing long delay, it was no doubt that would increase a lot of difficulties to analysing and designing of the network control systems. So real-time researching and analysing of networked control systems were particularly important for us.In this paper, aimed at the key features of B&R's temperature control device:non-linear and difficult to obtain the exact mathematical model, the plant had long pure delay, difficult to select the controller parameters. Based on those problems, combined the classical Smith predictive control, fuzzy control theory and traditional PID control together, After repeated comparisons, using variable structure Smith predict fuzzy PID method to design such network control systems which has plant like that.The method of Smith prediction is in somewhere of system to increase control slip to offset transfer function denominator's delay component. Because of traditional PID control had simple structure, good stability and good high reliability, making it widely used in industrial control. Because of the combination of fuzzy control theory, the system is not very sensitive to outside interference compare to general control algorithm, that could help improve the system anti-jamming capability. In designing there had some structural adjustments, made the networked control system realize double dynamic predictation of network delay and the plant delay on structure, it also simplified the difficulties of NCS design, it would introduce specifically in the third chapter.In the fourth chapter of this thesis, displaced the simulation result based on variable struc-ture Smith predict fuzzy PID temperature control NCS. Devided to two instances to simulate and discuss:firstly network not only had transmission delay but also had certain packet loss (packet loss probability=0.3); secondly net work just had transmission delay (packet loss probability=0). According to simulation result, when used the variable structure Smith predict fuzzy PID method to deal with those networked control systems who had long delay uncertant-y plant, network control systems had good robustness, good dynamic and anti-jamming capability. Therefore it demonstrated that the control method to deal with such problems had certain advantages.In the fifth chapter of this thesis, builed the corresponding temperature control NCS model combined Truetime 1.5 and B&R special module, using Automation Studio soft wich was provided by B&R to do experiment, and displaced the final results. According to the experimental results, verificated the effectiveness of the control method again.