Self-tuning Fuzzy Smith Controller Aics Sewage Treatment System

With the development of economy and the rapid trend of industrialization and urbanization, the situation of water pollution is more and more serious and becomes the bottleneck of sustainable development. Therefore, it is necessary to deal with water pollution and improve water environment. Although AICS(Alternated Internal Cyclic System) is a kind of advanced technology for sewage treatment, the operation mode of AICS is complex and requires high level automatic control system. Therefore, it is significant to research the controlling technology of AICS.The DO (dissolved oxygen) concentration in aeration tank is an standard to judge the quality of water. The DO does not only stand for the degree of water pollution, but also reflect the amount of air from blower. Due to nonlinearity, time-varying and delay of the process of aeration, it is not easy to control DO in the aeration tank.Based on the No.1 sewage treatment plant of Rizhao City, this essay analyses the controlling process of the DO in aeration tank theoretically and builts a model of areation process. In addition, a kind of self-tuning fuzzy Smith controller is designed through integrating self-tuning fuzzy PID control and the Smith predictive control to adapt controlled object and improve the aeration process. Siemens S7-300 PLC is the core of the self-tuning fuzzy Smith controller, which mainly includes PLC, frequency transformer, air blower and DO detector. The system can realize several functions, such as data capture for DO, self-tuning fuzzy Smith controlling algorithm and controlling upper machine.The results of simulation and practical application shows that the self-tuning fuzzy Smith controller reduces the overshoot of system, and improves the stability and anti-interference of system. It could be seen as an ideal intelligent controlling scheme. After using the self-tuning fuzzy Smith controller, the areation process works well, reduces energy consumption and friction of air blower and extendes lifetime. Finally, it improves economic benefit and social benefit of the enterprise.