PID Tuning problem

Discussion in 'The Projects Forum' started by Dom Amoy Brew, May 6, 2014.

  1. Dom Amoy Brew

    Thread Starter New Member

    May 6, 2014

    I help two friends to upgrade there craft beer brewery with a little more advanced cooking pot solution. We got a nice PLC from ABB from an other project. Everything works very good except the PID tuning. I read already hours about PID setting but i get the feeling that this needs a lot of experience and training which i do not have. I also get really confused with all the short terms, where i think different systems use different terms. And never the less, i believe my far far away calculus knowledge is pretty much gone.

    I tried it with a bump test (very good explained at, but as from what i understand, and tried, it would have taken far to long, and when i estimate then this values, they get so big, that they must be wrong.

    Maybe someone can help us, to figure out the correct values. Attached the project description.

    Thanks a lot for any help and advice.


    Heating pot for beer brewing
    The target is to have a fast system which is not overshooting more then 0.2 degree at a given set point, which are different Values from 50˚C to 80˚
    We have an ABB AC500 eco with a PID controller. After the PID is a PWM from 0 to 1000.
    We use a Solidestate contactor to switch the power.
    Variables for the PID controller
    KP:REAL;********************************(* proportionality const. (P)*)
    TN:REAL;********************************(* reset time (I) in sec *)
    TV:REAL;********************************(* rate time, derivative time (D) in sec*)

    Cooking pot spec

    Ambient Temp 25˚C
    Heating power 12kW
    Oil Jacket 110l Thermal Oil
    Water 400L Constanty steared

    Heating @40-50˚C 15.12605042 ˚C/houer
    Heating @70-80˚C 14.57649376 ˚C/houer

    Cooling @45-37˚C/h 0.308333 ˚C/houer
    Cooling @80-70˚C/h 1.661341853 ˚C/houer

    heating power to be stable at the given temp in %
    @40˚C 1.57 %
    @80˚C 11.39740379 %

    Dead time

    40˚ to 80˚ @ 100% heating 14min

    PID values

    Calculated, by best knowledge. Which is after reading a lot still very limited. Result was not usable.
    Kp 0.713785359
    TN 101.9
    TV 8.911860718

    Values tried by trial and error. Result was not to bad, but far from what we need.
    It is Overshooting about 4˚C. The controller starts only to react after it passes the set point. And still then it reduces very slow from 100 to 0%
    Kp 2
    TN 10
    TV 1
  2. crutschow


    Mar 14, 2008
    I'm certainly no expert on the subject but it would seem that you need to change the TV value, since it's the derivative function that anticipates the reaching of the set point and controls overshoot. Have you read this?
  3. Dom Amoy Brew

    Thread Starter New Member

    May 6, 2014
    Thanks Crutschow

    That is how far i came as well. I start to believe i have mainly a calculus issue and my problem is mainly there.

    To just change TV by trying will cause again just to very instable results.

    But your link does help a bit.

    Enjoy ur day
  4. alfacliff

    Well-Known Member

    Dec 13, 2013
    most of the allen bradley pid units I have worked with have an autotune function, does yours?
  5. KeepItSimpleStupid

    Well-Known Member

    Mar 4, 2014
    I might have a problem with

    That has very many interpretations.

    Eurotherm, is one of the "cream of the crop" companies and you may actually need something like this:

    They have redefined their control modes to:
    Fast cycle
    Single cycle
    Advanced single cycle
    Phase angle

    Phase angle firing gives you the most precise control.

    This is only the device that controls the line voltage and not the temperature controller.
  6. Dom Amoy Brew

    Thread Starter New Member

    May 6, 2014

    Thanks for your answer. But as u might have seen from the values above the process is pretty slow. So i doubt there is a big influence at which phase angle i switch the sinus. With a SSR i can switch up to 50Hz easy, which is already even super fast. I believe even 1Hz is quick enough. Before we had even a normal contacor in it.


  7. Dom Amoy Brew

    Thread Starter New Member

    May 6, 2014
    I thought about this before as well, but could not find it in the documentation.
    But now i will contact ABB. Maybe they have something in hand.

    Thanks a lot