Rockwell Automation 8520-ARM2 9/Series CNC AMP Reference Manual Documentation Set - Manual (Page 162)

Servo Parameters
Chapter 7
7-16
Range
Servo Loop Type: Results in: CNC generates:
(a) None Control behaves as if that servo is detached. --
(b) Position or
Analog Spindle Select this as the servo loop type for analog drive
systems that have an external tachometer mechanically
coupled to the motor shaft. Feedback from this
tachometer is typically returned to the servo amplifier to
close the velocity loop (see Figure 7.6). Can also be
used if the position loop is open or detached.
position command
(c) Position/Velocity The control closes the velocity loop. Separate devices
or the same feedback device can be used to close both
the position and velocity loops. This is typical of
tachless analog servo systems (see page 7-17).
Important: This selection is not applicable on the
9/440 high--resolution CNC. Any attempt to use this
selection with a 9/440 high--resolution results in the
error, “VEL LOOP INVALID WITH DAC OUT”.
torque command
(d) Digital or Digital
Spindle
The control closes the position and velocity loop. Motor
information necessary for proper commutation is
provided for digital drive systems. Can be used for
8520drive/8500motor or 1394 drive/1326 motor
systems. Must be selected for all digital systems,
including the 9/440, 9/230 Digital, and 1394 systems
used as digital spindles.
Important: Analog systems can not use a tachometer
for velocity feedback to the control. Only encoder
signals can be used for feedback to the 9/Series CNC.
Both the velocity feedback and positioning feedback for
an axis must be returned to the same servo module as
the servo’s output port.
digital command
(current)
Important: For more detailed information regarding Servo Loop Type,
refer to page 7-4.
Notes
This parameter must be set independently for each servo.
Important: The servo loop type, “Position/Velocity” is not applicable to
the 9/440 high--resolution device. Any attempt to select this servo loop
type will result in the error, “VEL LOOP INVALID WITH DAC OUT.”
Once you have configured both the “Servo Hardware Type” and the “Servo
Loop Type” additional parameters to configure that specific servo system
become available.