Rockwell Automation 1771-QDC, D17716.5.87(Passport) CLAMP AND EJECT MODE - Manual (Page 177)

Tune Your Machine
Chapter 10
10-4
Important: Never use FeedForward and ERC conjunctively to control
the same velocity loop.
The QDC module’s pressure control algorithm differs from classic PID
algorithms. For this reason, the loop integral term should generally be
larger than the loop proportional term upon completion of the tuning
process.
Disable ramping and ERC during tuning procedures.
Reset the QDC module’s internal ERC values before attempting to
modify closed-loop profile (stroke) tuning constants.
ERC values for all clamp and ejector profiles may be reset by accessing the
data table in your PLC processor and setting DYC05-B15 (Pro-Set 600
address B35/463) equal to “1”. The bit is reset to “0” after the ERC reset
has been accomplished.
Tuning constants differ not only between clamp and ejector profiles, but
also between profiles (strokes) with different directions of travel. The
dynamics of the loads being moved, as well as the differing hydraulic
characteristics of the circuits in forward and reverse directions, warrant
separate tuning considerations for all profiles (strokes).
Tune ClosedĆloop Pressure Control
Important: Only those clamp and ejector profiles which you run using
closed-loop pressure vs. position control require pressure loop tuning (for
example, Low Pressure Close should be tuned per the discussion below).
If you never run a profile under closed-loop pressure control (you are
utilizing velocity control instead), pressure tuning constants do not need to
be adjusted.
While full PID control is available for both clamp and ejector pressure
control algorithms, the majority of applications require only proportional
and integral control.
Important: In most cases, adding a derivative term to the QDC module’s
pressure control algorithms makes the control too sensitive and does not
enhance the loop stability.
When tuning QDC pressure vs. position loops, we recommend first tuning
your proportional gain, and then adding an integral term. Tuning any loop
is greatly simplified when an oscilloscope is available to connect to your
module’s output driving the selected valve.