How to set PID parameters for a trend chart like this
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As shown in the figure, there is a level LIC101 controller that controls the opening degree of the inlet valve of the liquid storage tank. However, the output of the valve (MV) and the liquid level (PV) follow the curves shown in the figure. Is this what is commonly referred to as \"oscillation with constant amplitude\"? The current gain value is 0.5, and the integration time is 20 seconds. How should these parameters be adjusted to stabilize the liquid level? Thank you!
Is this setting available only during the points period? No proportional time or gain settings? Amplitude oscillations are generally caused by excessive force; it is recommended that you increase the integration time to see the effect.
There’s also a proportion factor; if the gain is set to 0.5, then both the proportion factor and the integration value are too high, so they need to be reduced, right? Thank you
The integration time is too small; increase it.
Adjust the integration time first; integration time is inversely proportional to the integration effect – the larger the integration time, the smaller the integration effect, and vice versa. The integral action is used to eliminate residual errors
Your liquid level integration time of 20 seconds is too short and unreasonable; the liquid level itself has a relatively slow dynamic response. Without performing step tests, start with an integration time of around 5 minutes; this will give a rough estimate, after which adjustments can be made gradually. A ratio of 0.5 is considered to be within a reasonable range.
This is not necessarily a parameter issue; your graph is missing time. Just by looking at the diagram, the parameters seem fine. When adjusting parameters, it is crucial not to make changes right away without analyzing the reasons first.
Since it’s similar to an amplitude-modulated oscillation, the gain is too high; it needs to be reduced. Integration is used to eliminate residual errors and prevent large fluctuations; this integration time isn’t particularly long. For level control systems, I have set the integration time to less than 10 seconds, and the control performance is good.
The too small product of the level control proportional and integral times is the root cause of level oscillation. First, change the integration time to 300 seconds and set the proportion to 1