Research On Dissolved Oxygen Control Of Sewage Treatment Aeration System Based On Internal Model PID

With the development of global economy,industrial wastewater and domestic sewage are increasing day by day,sewage treatment has become a hot spot of research.At present,the activated sludge process is a relatively common method of sewage treatment,and the aeration system is a key part in the activated sludge process.Therefore,a sewage treatment plant in Shenyang is taken as the research background,and the aeration system is deeply studied for its Anoxic-Oxic(A/O)process in this thesis,one-degree-of-freedom internal model PID and twodegree-of-freedom internal model PID controllers are designed respectively,so that the aeration system can achieve a good control effect under both model matching and mismatch.The main research contents of this thesis are as follows.In this thesis,the mechanism of Anoxic-Oxic(A/O)process and the operation mechanism of aeration system are deeply analyzed,and the dissolved oxygen concentration is selected as the control parameter of the aeration process.An approximate mathematical model of sewage treatment aeration system is established.At the same time,in order to restrain the influence of non-uniform air flow on dissolved oxygen detection in aeration process,a cascade control structure was designed.In order to make up for the deficiency of conventional PID in dissolved oxygen control of aeration system,the internal model PID control method is studied in this thesis,which is applied to sewage treatment control system to realize the control of dissolved oxygen concentration.The structure of the method is simple and the control performance can be improved by adjusting the filter parameter a.The results of MATLAB simulation show that the control effect of the internal model PID is obviously better than that of the conventional PID.In order to improve the adaptability of the internal model PID,a fuzzy control strategy is introduced on the basis of the method to realize on-line adjustment of the filter parameter a in the internal model control.The results of MATLAB simulation show that the on-line adjustment of filter parameter a is realized by using the improved internal model PID control method with fuzzy strategy,and response speed is improved.In order to solve the problem that the dynamic model of aeration system is easily mismatched in the actual industrial environment,another internal model controller is introduced on the basis of one degree of freedom to form a two-degree-of-freedom internal model PID control structure.The target tracking performance and anti-jamming performance of the system are optimized by adjusting the parameters of the two-degree-of-freedom internal model controller.The simulation results of MATLAB show that the two-degree-of-freedom internal model PID control method has better target tracking performance and anti-jamming performance under model mismatch,realizes the control of dissolved oxygen concentration,and effectively overcomes the adverse effects of model mismatch on the system.