Cohen Coon Tuning Method
  1. Under Manual mode, wait until the process is at steady state.
  2. Next, introduce a step change in the input.
  3. Based on the output, obtain an approximate first order process with a time constant t delayed by tDEL units from when the input step was introduced.

    4.  

     

    The values of t and tDEL can be obtained by first recording the following time instances:
     
     

    t0 = time when input step was initiated
    t2 = time when half point occurs
    t3 = time when 63.2% point occurs


  4. From the measurements based on the step test: t0, t2, t3, A and B, evaluate the following process parameters:

    5.  

     
     

    t1 = (t2 - ln(2) t3)/(1 - ln(2))

    t = t3 - t1

    tDEL = t1 - t0

    K = B/A


  5. Based on the parameters K, t and tDEL, the following formulas prescribe the controller parameters Kc, tI and tD:




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This page is maintained by Tomas B. Co (tbco@mtu.edu). Last revised 1/18/2000.
     Tomas B. Co
     Associate Professor
     Department of Chemical Engineering
     Michigan Technological University
     1400 Townsend Avenue
     Houghton, MI 49931-1295

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