Rockwell Automation MD65 User Manual Version 2.0 - Manual (Page 176)

I-8 MD65 AC Drive User Manual
Guidelines for Adjusting the PID Gains
1. Adjust the proportional gain. During this step it may be
desirable to disable the integral gain and differential gain
by setting them to 0. After a step change in the PID
Feedback:
– If the response is too slow increase PID Prop Gain (A134).
– If the response is too quick and/or unstable (see Figure F.1),
decrease PID Prop Gain (A134).
– Typically, PID Prop Gain (A134) is set to some value below
the point where the PID begins to go unstable.
2. Adjust the integral gain (leave the proportional gain set
as in Step 1). After a step change in the PID Feedback:
– If the response is too slow (see Figure F.2), or the PID
Feedback does not become equal to the PID Reference,
decrease PID Integ Time (A135).
– If there is a lot of oscillation in the PID Feedback before
settling out (see Figure F.3), increase PID Integ Time (A135).
3. At this point, the differential gain may not be needed.
However, if after determining the values for PID Prop
Gain (A134) and PID Integ Time (A135):
– Response is still slow after a step change, increase PID Diff
Rate (A136).
– Response is still unstable, decrease PID Diff Rate (A136).
The following figures show some typical responses of the PID loop
at different points during adjustment of the PID Gains.
Figure I.1 – Unstable
PID Feedback
PID Reference
Time