Research And Application Of Fuzzy-PID Mixed Control Based On Smith Predictor In Temperation Time-Delay System

Temperature control is widely used in metallurgical, chemical, machinery and other industrial fields. These industrial areas'processes often have characteristics of complex conditions, parameter changes and controlling time-delay. Especially, as a result of phenomenon of time-delay, disturbances can't be observed in time that makes parameters of controllers not easy to select. If controller improper adjusts parameters, it will cause decline of controlling quality. Seriously, it will cause system instability. So researching on controlling time-delay has theoretic and practical significance.Due to industrial time-delay phenomenon, temperature time-delay control system based on web has been set up.Through experimental test and least-squares estimated methord, controlled plant's mathematical model has been established. Beause of controlled plant's model has characteristics of time-delay, the control strategy of Smith predictor and fuzzy-PID mixed control system based on rules has been used:the Smith predictor compensate system's time-delay; the controller used fuzzy-PID mixed algorithm based on fuzzy rules. This fuzzy controller chooses different controlling methods in different domain:in the transient phase, fuzzy controller takes main role; in the steady-state response, when the error and error change rates are all small, PID controller takes main role. This control method has advantages of fuzzy controller's good robust, good dynamic response, fast rise-time, and also has PID controller's high steady-state tracking accuracy.Fuzzy-PID mixed controller based on rules overcomes fuzzy-PID switching controller's weakness that difficult to achieve switching without disturbance, so it can be achieved more satisfactory results.Theoretical analysis and results of simulation show that fuzzy-PID mixed control has shorter response time and smaller stable error than pure PID or fuzzy logic controller.Based on the technology of Siemens's industry Ethernet and PROFIBUS fieldbus, temperature time-delay experimental control system has built in this paper.The control system uses Siemens'hardware and software to design process control system.Fuzzy-PID mixed control algorithm has been used in this control system. It hasb een used to control temperature time-delay, experimental results show that:the proposed algorithm has better control quality than traditional PID algorithm, so it has certain practical value.