Rockwell Automation 8520-ARM2 9/Series CNC AMP Reference Manual Documentation Set - Manual (Page 723)

Appendix
A
A-1
Tuning a Digital or Tachless Analog
System
The digital and analog tachless servo system differs from traditional drive
systems in that the velocity loop is closed by the 9/Series CNC using an A
quad B feedback device. Traditional systems typically use the drive
amplifier to close the velocity loop while the CNC controls the position
loop. The digital and analog tachless servo system is designed to:
reduce integration costs by not requiring an external tachometer on the
servo motor
give the 9/Series CNC control of the velocity loop (necessary for
adaptive feed and feed to hard stop features) and provide better servo
control.
You can either close the velocity and position loops using the same
encoder device (attached to the motor shaft) or you can close the velocity
loop with an encoder on the motor shaft and use some other A quad B
device to close the position loop (on 3 axis prom based analog servo cards
you must use the same feedback device for both the velocity and
positioning feedback). The velocity loop must always be closed by a
feedback device mounted directly on the motor shaft.
ATTENTION: Your servo drive system must incorporate
dynamic breaking circuitry for safe performance. The 9/Series
CNC does not provide any controlled stopping of the servo
when in E-Stop.
Important: This servo tuning procedure can not be used when tuning an
8520 digital system. If your 8520 digital system requires additional tuning
above the AMP defaults, contact your Allen--Bradley customer support
group for assistance.
A.0
Overview