How to set PID parameters of liquid level in DCS control system?

The tuning steps of PID controller parameters are as follows:

(1) First, select a sufficiently short sampling period in advance to make the system work;

⑵ Only join the proportional control link until the step response of the system to the input appears critical oscillation, and write down the proportional magnification and critical oscillation period at this time;

⑶ Under a certain degree of control, the parameters of PID controller are calculated by formula.

Parameter tuning of PID controller is the core content of control system design. According to the characteristics of the controlled process, the proportional coefficient, integral time and differential time of PID controller are determined. There are many methods for tuning PID controller parameters, which can be summarized into two categories: one is theoretical calculation tuning method. It mainly determines the controller parameters through theoretical calculation according to the mathematical model of the system. The calculated data obtained by this method cannot be used directly, and must be adjusted and corrected through engineering practice. The second is the engineering setting method, which mainly relies on engineering experience and is directly carried out in the test of control system. This method is simple and easy to master, and is widely used in engineering practice. The engineering tuning methods of PID controller parameters mainly include critical proportion method, response curve method and attenuation method. The two methods have their own characteristics, and the common point is to adjust the controller parameters according to the engineering experience formula through experiments. But no matter which method is adopted, the parameters of the controller need to be finally adjusted and improved in actual operation. Generally, the critical proportion method is adopted.