Rockwell Automation 1771-QB Linear Pos. - Manual (Page 131)

Initializing and Tuning the Axes
Chapter 8
8Ć13
5. Set the integral gain equal to 70% of the proportional gain at which
continuous oscillations occurred (see step 3).
K
I
= 0.7 x K
P
6. Set the derivative gain equal to 70% of the proportional gain at which
continuous oscillations occurred (see step 3). This small derivative gain is
recommended to improve axis stability.
K
D
= 0.7 x K
P
7. Check the axis stability under all load conditions. In some instances, you
may have to adjust the proportional, integral and derivative gains slightly
or use the gain reduction factor to obtain the desired results.
Example: Optimal PID Loop Gain Calculation
If continuous oscillations occur with a proportional gain of 0.1000 ips/mil and
the integral and derivative gains set to zero, the optimal gains are calculated as
follows:
K
P(unstable)
= 0.1000 ips/mil
K
P
= 0.7 x 0.1000 = 0.0700 ips/ mil
K
I
= 0.7 x 0.0700 = 0.0490 (ips/s)/mil
K
D
= 0.7 x 0.0700 = 0.0490 unitless
Update the Application Program
As a final step, you should copy the parameter block data determined above,
into the data tables for your application. The tuning and integration procedure
used axis 1, but you can perform a similar procedure with axis 2.