Rockwell Automation 1746-HSRV SLC Servo Control Module User Manual - Manual (Page 181)

Publication 1746-6.1.2 - July 2000
A-8 Input/Output Quick Reference
Velocity Feed Forward
Constant
(Servo Loop) M0:s.32,s.33 0.0 to 1.0 0.0 This parameter is active only when the Loop Closure
Method is set to velocity feedforward. Units are in
percentage and represent the portion of the velocity
command controlled by the pre–calculated final
velocity. The percent of following error (incremental
to the standard position loop algorithm) is inversely
proportional to the value of this variable.
For example, setting the feedforward constant to 0.9
(90%) means that the SLC Servo Module applies
90% of the precalculated final velocity to the
velocity command. The servo runs at the commanded
velocity with only 10% of the following error it
would have by using the standard position loop
algorithm, providing the system is calibrated
properly.
A value of 0.0 for this parameter applies 100%
velocity feedforward action.
Acceleration Feed
Forward Constant
(Servo Loop) M0:s.34,s.35 0.0 to 1.0 0.0 This parameter is active only when the Loop Closure
Method is set to feedforward. Units are in
percentage and represent the portion of the velocity
command to be controlled by the pre–calculated
final acceleration.
The acceleration feedforward constant is similar to
velocity feedforward constant in terms of range
checking. In certain applications that require the
servo loop to closely follow the command position,
use this parameter to reduce the following error that
occurs on transitioning from current speed to the
new speed (i.e., accelerating or decelerating). If the
system is calibrated correctly, zero following error is
achieved by using velocity feedforward of 1.0, but
the system still generates following errors on
transitions. Use the acceleration feedforward
parameter to reduce the following error occurring on
transitions.
A value of 0.0 for this parameter applies 0%
acceleration feedforward action.
Home Tolerances –
Position Units
(Homing) M0:s.36,s.37 0.0 to axis travel limit 0.1 When the actual position is within the position band
of the home position, the At Home bit is set.
Parameter Name
(Parameter Group) Destination M
File Location
1
Range Default Additional Information