Tuning of Cascaded loops

  • Thread starter N. Mukhopadhyay
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Thread Starter

N. Mukhopadhyay

Hello Everybody

Can you suggest me the better ways to tune Cascaded loops . For Example LIC FIC , TIC PIC LOOPS ?
I recommend using the ISA 'Independent Learning Module' series of books to study this subject. There is one titled "Tuning of Industrial Control Systems" by Armando B. Corripio. Chapter 7 covers Tuning Cascade Control Systems.

Some key points: Tuning of the controllers in a cascade system must be done from the inside out, that is, the innermost loop must be tuned first.

The inner loop(s) must be tuned 'tighter' and 'faster' than the outer loops.

The methods used to tune each loop are the same used to tune loops which are not cascaded.

There are various other rules of thumb concerning selecting which modes to use in each loop. It is better to consult the text to cover these details.

best success!

Paul R Nelson, PE
Dow Corning Auburn Site
Engineering and Process Controls
Email: [email protected]
Phone: (517) 496-7013
Fax: (517) 496-7100

Félix Blanco


Check this first: secondary variable have to respond faster to change than the primary does.

In a two level cascade system:
1.- Tune the inner controller as fast as possible, while the primary is in manual.
2.- Then tune the primary or master controller (secondary in auto).

Hope this helps.

Félix Blanco

johan bengtsson

RE: INFO: Tuning of Cascaded loops

Tuning cascaded loops is not worse than tuning individual loops as long as you tune them "inside out" ie start with the innermost loop and works yourself out.
The general recommendation is that the speed of the loops differ approx 5 times or more. If you are tuning with for example the lambda method (where desired speed of the control loop is one input parameter) this might be something to keep in mind.

/Johan Bengtsson

P&L, the Academy of Automation
Box 252, S-281 23 H{ssleholm SWEDEN
Tel: +46 451 49 460, Fax: +46 451 89 833
E-mail: [email protected]
Internet: http://www.pol.se/

-----Original Message-----
From: [email protected]

Can you suggest me the better ways to tune Cascaded loops . For Example LIC FIC , TIC PIC LOOPS ?
Reading the previous answers, my friend you are in the right seat. One thing strikes my mind but forget it, I may well be wrong.
What puzzles me is cascaded level and pressure loops. I just can not see that in real need.