Research Of Sewage Treatment Control System Based On Genetic Algorithm

The pharmaceutical wastewater with more complex quality and higher concentrations is one of the important sources of industrial wastewater,which causes greatly harm to environment and people's health.At present,it is absolutely essential to do the research on pharmaceutical wastewater treatment.Every link was very important in the process of wastewater treatment,especially the biochemical processing link was the most important.However,the dissolved oxygen content was closely related to whether the biochemical treatment phase can significantly reduce the content of organic matter in wastewater,so it was critical that the dissolved oxygen content was controlled accurately.However,the process of controlling the dissolved oxygen concentration in water was easily influenced by the fan frequency and water temperature,and the control process showed a serious nonlinear and hysteretic characteristics.It was difficult to control the dissolved oxygen content accurately by using the conventional PID controller.Therefore,the PID parameters optimization method based on genetic algorithm was put forward in this article.This paper was based on the research project of wastewater treatment control system of a pharmaceutical enterprise in Yi Chang.Firstly,the wastewater treatment process was introduced in this paper,the main technical content and the key water quality parameters of which were analyzed.Secondly,the overall design scheme of the wastewater treatment control system was determined,the main hardware devices in the system were the controller,the computer,the frequency converter,the electromagnetic valve and so on,the software part had completed the design of the host computer system and the control program.Then this paper introduced genetic algorithm in detail,strategies was proposed to overcome the disadvantages of genetic algorithm,such as local convergence,poor local-searching ability and so on.The improved algorithm was adaptive genetic algorithm.In the operation,the algorithm could retain the excellent individuals,which prompted the population move to optimal solution region so as to achieve the goal of improving the local-searching ability and guarantee diversity of individuals at the same time.The complex characteristics of the wastewater treatment process determined that the control object have properties of strong hysteresis,large inertia and non-linearity,thereby the research on simulation of a second-order with delay had been done.The PID controller parameters optimization of a second-order with delay system was simulated by using genetic algorithm,adaptive genetic algorithm and conventional PID algorithm respectively,the results showed that the parameter optimization and performance of PID controller based on adaptive genetic algorithm was optimal.According to the research of basic principles of biochemical treatment process,the mathematical model of the dissolved oxygen concentration was established.Then the simulation had been performed by MATLAB,and the results were stated as follows: the genetic algorithm,adaptive genetic algorithm,conventional PID algorithm were applied to the control object respectively,and the tracking,noise immunity and robustness were analyzed;the contrast diagram of simulation curves showed that the overshoot and adjusting time of the two optimization methods were lower than that of the conventional PID control method;when compared to genetic algorithm,adaptive genetic algorithm's overshoot decreased by 12% and settling time reduced by 49.8%,and its noise immunity and robustness were better.It was proved that the performance of PID controller based on adaptive genetic algorithm was best in both control precision and dynamic characteristics,and it could reach the control demand.