Method for tuning regulator parameters

In the production process, sometimes process fluctuations are caused by process operations or individual equipment failures, which cannot be overcome by PID parameter tuning of instruments. So the tuning of regulator parameters should be appropriate, and abnormal phenomena caused by some abnormal factors should not be considered as poor parameter adjustment. Therefore, the quality of regulation cannot be judged without the process.

In parameter tuning, empirical method is one of the widely used engineering tuning methods in simple control systems. It is essentially a trial and error method, with the pre-set numerical range of parameters and the repeated trial and error program being the core of this method. It continues to be tested until the attenuation speed ratio approaches the 4:1 transition curve. There are various parameters that are suitable for this 4:1 oscillation process, among which the one with the smallest PI product is the parameter selection. On the basis of parameter selection, if differential adjustment is added, the PI parameter should be appropriately reduced. Because differential regulation is a forward acting regulation, its essence is to prevent changes in the regulated parameters, improve system stability, and attenuate the transition process more. Therefore, in order to maintain the original attenuation ratio, PI should be appropriately reduced.

In the specific setting of PID parameters, the following methods are worth learning from.

① If a small proportion parameter is selected in the flow regulation system, the problem of transient curve oscillation often occurs. However, by increasing the proportion and reducing the integration time, the oscillation can be overcome and the speed of eliminating static error can be accelerated.

② The liquid level regulation system generally selects a fixed proportional degree of about 20%, and with the addition of integration, a satisfactory transition process curve can generally be obtained.

③ The temperature regulation system generally has a wide range of proportional degree and integration time, with a proportional degree of about 20% and an integration time of about 1.5 minutes.

In short, the tuning of adjustment parameters should be adjusted according to the curve of the recorder, and repeatedly debugged under closed-loop operation. The basic principle of debugging is to increase the proportionality when reducing the integration time; When increasing the differentiation time, decrease the proportionality and integration time.