The liquid level and flow rate need to be controlled evenly, with the flow rate being the primary factor and the liquid level being secondary; how should this be represented in a PID controller?
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The liquid level and flow rate need to be controlled evenly, with the flow rate being the primary factor and the liquid level being secondary; how should this be represented in a PID controller?
Liquid level – uniform flow control, which can be achieved through single-loop uniformity or cascade uniformity. The structure of a uniform control system has no special features; it is the same as that of single-loop and cascade structures. As for whether to focus on flow rate or liquid level, or to use both variables equally, this needs to be specified in the design notes.
I can’t draw. . . It can pee – with plenty of force; shooting it up to the third floor is no problem. Want to take a look? :P The liquid level refers to the height of the liquid column; flow rate is the rate of change of the liquid column’s height over time, multiplied by the container’s instantaneous cross-sectional area
More or less that’s it; in this graph, the primary variable is the liquid level, while the secondary variable is the flow rate
Thank you very much. So if in this uniform adjustment flow rate is the main factor and liquid level is the secondary factor, should it be drawn in the same way?
For example, when flow rate is the focus, is there a difference in the method of measurement compared to when liquid level is the focus?
There’s no difference, I guess, but I haven’t encountered a situation where flow rate is the primary factor and level is secondary; usually, it’s the level that matters most, with flow rate being adjusted accordingly
There is no difference. If it is uniform in a single loop, the measured liquid level is sent to the controller, whose output is then sent to the control valve. If it is series uniformity, the measured liquid level is sent to the flow controller as a setpoint; the measured flow rate is also sent to the flow controller, and the output from the flow controller is sent to the control valve. Specify in the design notes which one should be prioritized, or provide the range of variation for a certain parameter.
The drawing method is the same; the difference between this and fixed-value control lies in the different settings of the PID parameters. For cascade proportional control, the main regulator is usually set to PI, while the secondary regulator can be set to P.
Well, generally it’s the liquid level that plays the main role, but from the information on uniform control, it seems that either of the two can be the key factor
It’s a cascade-type uniform control system, with flow rate being the primary parameter to be stabilized, and liquid level being secondary. It would be simple if that weren’t the case. I’ve previously worked with distillation towers where liquid level was the key parameter, but I’ve not dealt with systems where flow rate is the main focus. Now, with this new design, I want to make changes