[airbreather]

Derivative is used in certain specific applicatiopns, eg boiler freedwater pumps, but generally, yes, avoid.

If you want good fast loop performance without overshoot don't forget the posicast.

Finally, PID loops are not everything, ask yourself "do I really need a setpoint that is maintained to 1% or better, or do I really just not want to overflow the tank?" If the latter, a ratio control can often be simpler, easier and most noteably not pass on as much process disturbance down the line leading to the plant settling out quicker.

[MBaert]

Thanks for the feedback, hope you enjoyed reading it. Looks like you have a process engineering background, I am not familiar with a ratio controller actually, good to know.

Maybe for our next article I should dive in deeper how to avoid overshoot and what methods there are (eg. posicast, simple speed damper, ..)

[airbreather]

ratio controller example is like pump at 100% when tank at 90%, 0% when 70% and interpolated inbetween

pump % = (level% - 70) * 5

limited between 0 and 100

so fuller the tank, harder the pump works, in steady state an equilibrium point will be reached somewhere in the range relative to inflow vs outflow rates.

It gives less surging downstream, at the cost of a known setpoint, just has a working range.

It might have marginally have less capacity compared ti PID, as the pump wont jump up to 100% immediately a surge comes thru at all levels, but that also depends on PID loop tuning.