Output has too many oscillations using Tyreus-Luyben tuning parameters?

I am trying to re-create these two figures from my process controls textbook:

These graphs were creating by using Tyreus-Luyben tuning parameters where y is the output and u is the input. My graphs are as follows:

My lines for the P and PI controllers are correct in both graphs, as well as my line for u for the PID. However, my PID y line (-.- line on both graphs) is oscillating too much, and I'm not sure how to adjust this. I've tried changing the value of b on my set point from 1 (keeping c=0), but this changes my u graph. My parameters & set-up are as follows:

kcu = 10 Pu = 6.2

Any thoughts on how to fix this would be greatly appreciated!

Answer 1

[Stephan]

Hi,

is it correct that you use a 2DOF PID Controller? You dont use the second input port. The 2DOF works with weights for both inputs. Due to this fact the internal calculation is not the same as it is by using standard PID. I guess this is the problem you have.

I recommend either to use the second input port as shown in the documentation or use the normal PID Controller, what seems more problably to me, since you use an example from a book.

Best regards

Stephan