(Relay) Tuning Method:
Using a constant input, say uo, determine the corresponding
steady state output, say yo.
Next, change the setpoint to be yo.
Switch the controller to relay mode and choose a small value for h.
This will implement the following algorithm:
Under this mode, the output should settle towards a limit cycle.
From the plot, measure the amplitude of the output cycle, a. Using
both a and h, the ultimate gain, Ku, can
then be approximated by
Ku = (4/p)(h/a)
Using as an approximate for the ultimate gain Ku and
ultimate period Pu (the period of the limit cycle in
the plot above), apply the same prescribed values in Ziegler and Nichols
method. ( Click here
to go to Ziegler-Nichols method)
( Use the BACK button of your browser to return to a currently
running PID tuning simulation, otherwise click
here to initiate a PID tuning simulation.)
This page is maintained by Tomas B. Co (email@example.com).
Last revised 1/12/1999.
Tomas B. Co
Department of Chemical Engineering
Michigan Technological University
1400 Townsend Avenue
Houghton, MI 49931-1295