Rockwell Automation 8520-ARM2 9/Series CNC AMP Reference Manual Documentation Set - Manual (Page 173)

Servo Parameters
Chapter 7
7-27
Advantages to ZFE Closed Loop are
1) improved performance during high precision or high speed
applications;
2) faster part program execution because velocity transition times are
reduced.
Important: A closed--loop axis requires homing. Refer to the homing
parameters of chapter 5.
Figure 7.17
ZFE Closed--loop Block Diagram
Analog Servo Interface
Analog Drive
Motor
Encoder
Tacho-
meter
Amplifier Amplifier
Interpolated
Velocity
Position
command
Position
feedback
Position feedback
Velocity feedback
DAC
output
Digital to
analog
converter
Fine
interpolation
Position
comparison
Feed Forward
Percentage
Velocity
comparison
d
dt
Servo Off -- The servo output has been disabled, but feedback can still
be monitored. This provides a valuable tool for diagnosing feedback
problems. With proper PAL programming, this can also be used to
“measure” tool or part position as in digitizing.
Servo Detached -- There is no servo connected to this axis. The servo
output and feedback are both disabled. The control will display a series
of dashes in the Axis Position screen to indicate a detached axis.
Depth Probe -- This output option tells the control that this device is an
adaptive depth probe. Refer to page 32-1 for additional AMP
configuration requirements for an adaptive depth probe. Don’t select
this option if you are using a 3-axis digital servo module. This selection
is available with 4-axis servo modules and the 9/440. This option is a
valid selection for mill control types only.