Research about Fuzzy-PID Control Method of pH Value in Chemical Industry Process

In view of the nonlinear and time-delay characteristics in acid and alkali neutral reaction process, a novel parameter self-adjusting Fuzzy-PID control method is proposed. The fuzzy controller can adjust PID controller's parameters online according to the real-time deviation of pH value. There are two main methods to obtain the expected control index. Firstly, through enhancing the sensitivity of the linguistic value, it can adapt the big change rate of pH value nearby the neutral point when the deviation is small. Secondly, by analyzing the magnitude and symbol of the deviation and change rate of deviation, fuzzy rules can be well established. The simulation results show that the method can not only adapt to the change of pH value in large scale, but also overcome the flow fluctuation.