Siemens PLC's PID controller parameter tuning method - Database & Sql Blog Articles

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The parameter tuning of the PID controller is the core content of the control system design. It determines the scale factor, integration time and derivative time of the PID controller according to the characteristics of the controlled process.

There are many methods for PID controller parameter tuning. There are two general categories: one is the theoretical calculation tuning method. It is mainly based on the mathematical model of the system, and the controller parameters are determined through theoretical calculations. The second is the engineering setting method, which relies mainly on engineering experience and is directly carried out in the test of the control system. The method is simple and easy to grasp, and is widely used in engineering practice.

The engineering tuning method of PID controller parameters generally adopts the critical ratio method. The tuning steps of the PID controller parameters using the method are as follows: (1) first select a sufficiently short sampling period for the system to work; (2) only add the proportional control link until the system has a critical oscillation in the step response of the input. Write down the proportional amplification factor and the critical oscillation period at this time; (3) Calculate the parameters of the PID controller by the formula under a certain degree of control.

PID parameter setting: It is based on the familiarity of experience and technology, and the measurement value tracking and set value curve are referenced to adjust the size of P\I\D. Proportion I / differential D = 2, the specific value can be determined according to the instrument, then adjust the proportional band P, P over the head, reach a stable time, P is too short, will oscillate, never hit the set requirements.

The engineering tuning of PID controller parameters, the empirical data of PID parameters in various adjustment systems can be referred to below:

Temperature T: P=20~60%, T=180~600s, D=3-180s;

Pressure P: P = 30 ~ 70%, T = 24 ~ 180s;

Liquid level L: P=20~80%, T=60~300s;

Flow rate L: P = 40 ~ 100%, T = 6 ~ 60s.

Here is a method of experience. The basic procedure of the method is to first determine a set of regulator parameters based on the operating experience, and put the system into closed-loop operation, and then artificially add a step disturbance (such as changing the given value of the regulator), observe The step response curve of the output or regulator output. If the control quality is considered unsatisfactory, the regulator parameters are changed according to the influence of each tuning parameter on the control process. Repeat the test in this way until you are satisfied.