| The boiler make-up water pretreatment has a great significance on safe,efficient and long-term stable operation of thermal power. The medicament feeding system of coagulant process is an important link in the boiler make-up water pretreatment system. But the traditional PID control method is hard to meet the demands of production, which can influence following links in the production. Based on the reality, the paper designed a PI-Fuzzy controller and bring a feedforward link into the control system, which can solve non- linearity, time-variable and time lag problems in the medicament feeding system.According to the characteristic of boiler make-up water pretreatment, this paper analyzes problems of the medicament feeding system:⑴The feedback control has a characteristic of long time lag;⑵The non-linearity factors that influence the coagulation effect are so many that the mathematical model is difficult to be established accurately.This paper creates a method to solve problems:Firstly,The thesis contrapose the shortage of single feedback control, choose the schemes of feedforward-feedback control which can solve the long delay of the medicament feeding system.Secondly, Fuzzy control system can translate experts'knowledge and experiences into control rules. According to these rules, Fuzzy controller can control the system. Therefore, fuzzy control is especially suitable for the control of the mathematical model which is difficult to be established accurately and non-linear system.The thesis designed a PI-Fuzzy controller, which is used to achieve the coagulant dosing automation system. In this system , it uses effluent turbidity deviation value of flow tank and its change rate as input variables, frequency as output variables. It can avoid the complicated mathematical model, solves the problem the traditional PID control methods cannot deal with and meet the demands of industrial production. The design of the PI-Fuzzy controller is feasible and practical. |
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