Rockwell Automation 1771-QDC, D17716.5.87(Passport) CLAMP AND EJECT MODE - Manual (Page 181)

Tune Your Machine
Chapter 10
10-8
Tune ClosedĆloop Velocity Control
Important: Only those clamp and ejector profiles which you run using
closed-loop velocity vs. position control require velocity loop tuning. If
you never run a profile under closed-loop velocity control (you are
utilizing pressure control instead), velocity tuning constants do not need to
be adjusted.
While full proportional and feedforward control is available for both clamp
and ejector velocity control algorithms, the majority of applications require
only proportional control with the feedforward term left at zero.
Important: In many cases, adding a feedforward term to the QDC
module’s velocity control algorithms makes the control too sensitive and
does not enhance the loop stability.
When tuning QDC velocity vs. position loops, we recommend first tuning
your proportional gain, and then adding feedforward only if it is required.
Tuning any loop is greatly simplified when an oscilloscope is available to
connect to your module’s output driving the selected valve.
We assume the same objective in tuning a velocity loop utilizing a scope as
without it. Maximum control is desired without introducing so much gain
that the machine hydraulics hammer and wear.
If an oscilloscope is available, connect it to your selected clamp (ejector)
velocity control valve at this time, and proceed to the section in this
chapter on Tuning velocity loops with an oscilloscope.
Tune Velocity Loops without an Oscilloscope
Before you begin tuning your velocity loops, confirm the following:
Velocity vs. position is selected
Closed-loop is selected
ERC is disabled
ERC values have been reset
Ramping is disabled
All setpoint changes have been download to the QDC module
ATTENTION: Prior to running clamp profiles, refer to chapter 8
to verify that the appropriate Low Pressure Close Zone Overrun
or Open Slow Zone Overrun setpoints and bit selections are
entered properly and downloaded to the QDC module. Do this to
minimize the possibility of mold or machine damage.