Application Research Of Muti-mode Adaptive Fuzzy Control In Wastewater Treatment System

This thesis has been carried out based on the control system of a sewage treatment factory of Chongqing. Activated sludge wastewater treatment is one kind of biology method, which is used widely in the world. The principle of activated sludge process is consuming the pollutant in wastewater by microorganisms'metabolism. Due to the violent change of influent and the complexity of microorganisms'growth, the activated sludge processes have characteristics of muti-variables, strong coupling, high non-linearity, big lag and indetermination, which result in laggard automation of wastewater treatment process. To ensure that the treatment process run well and enhance effluent quality, it has become an important task in the field of wastewater treatment to research new control method. Researching the intelligent control strategy in wastewater treatment can not only enrich theory and application of intelligent control, but also be useful to the development of control theory, which can provide new control way for nonlinear and complicated systems.In order to solve those problems mentioned above, the author has done a lot of research job based on analyzing the past achievements. The main job is as follows:Firstly, based on the analyzing of the inward mechanism of activated sludge wastewater treatment system and considering the realities, established the system mathematic model, which reflects the relations among dissolved oxygen, microorganism and substrate, built a system simulation platform by the tool of MATLAB.Secondly, introduced the principle and design steps of fuzzy control system and analyzed the common structures of Fuzzy-PI controller. According to the feature of dissolved oxygen control, designed the adaptive fuzzy controller based on self-setting of scale factors,Lastly, combining the advantages of Bang-Bang control, P control, fuzzy control and PI control, a new muti-mode adaptive fuzzy control is put forward. Used DO concentration as controlled variable, the simulation result proved that muti-mode adaptive fuzzy control can obtain good tracking performance and good robustness. It can control dissolved oxygen concentration accurately to save energy by regulating aeration rate when influent concentration and influent flow changes.The application of multi-mode control and fuzzy control in the process of wastewater treatment is worthful both in academic studies and practical application.