Abstract
Distilled water machine's work process is very complicated. The main steam pressure, temperature of its hot exchange loop and the pressure, temperature, liquid quantity of raw material water connect closely and present nonlinear relation. So during the process, we need to control two important parameters: one is the electric on ductivity rate of distilled water at exit; another is the temperature of distilled water at exit. Electric conductivity rate generally is controlled by regulating the raw material water's valve door, while export temperature generally is controlled by regulating steam quantity passed into the heat exchanger. Because the distilled water machine has the characteristics of serious delay, nonlinear, strong interference etc., And because the pure vapor output loop and cool water loop are all hot exchange loop's strong interference resource, therefore common PID can't achieve satisfactory effect. For this reason, this paper adopt PID controller composed of PID controller and expert system to control the system .
Combined the actual evaporating process, on the basis of expert system, this paper establish the perfect knowledge warehouse and adopt forward-reasoning mechanism,inspiring research method, exchange person-machine junction to design an expert system applicable to the distilled water production.
This paper uses configuration software to develop the supervisory control system of distilled water machine and realizes in the central control room to control on-line product quality examination, which not only saves a lot of spot operation, but also increases the control accuracy. This system has plenty of functions, friendly interface and high practicality.
