Command Descriptions
261
SGAF
Acceleration Feedforward Gain
Type
Tuning
Syntax
<a_><!>SGAF<i>
Units
i = percent
Range
0 – 500
Default
100
Response
SGAF: *SGAF100
See Also
DMTJ, LJRAT, SFB, SGENB, SGSET, SGVF, TGAIN, TSGSET
Product Rev
GT6K n/a
GV6K 6.0
(applicable only to
servo axes)
Use the
SGAF
command to set the gain for the acceleration feedforward term in the servo control algorithm.
Introducing acceleration feedforward control improves
position tracking performance
when the system is
commanded to accelerate or decelerate. Acceleration feedforward control does not affect the servo system’s
stability, nor does it have any effect at constant velocity.
The
SGAF
value is multiplied by the
commanded acceleration
calculated by the GV6K’s move profile
routine to produce an estimated torque command that is added to the servo control signal. The value is
normalized to the current setting of both the motor inertia and load inertia ratio (
DMTJ
and
LJRAT
,
respectively) as shown in the equation below.
(
)
command
on
accelerati
LJRAT
1
DMTJ
on torque
accelerati
Estimated
100%
value
SGAF
⋅
+
=
=
4
4
4
3
4
4
4
2
1
Setting
SGAF
to 100% will theoretically produce zero following error during the acceleration and
deceleration part of a move profile. This assumes that the drive or motor are not being current limited, the
values for inertia are accurate and the models used for analysis are correct. You can adjust the value of
SGAF
from zero to as high as 5 times or 500% (
SGAF500
) of the theoretical value. For example,
SGAF200
sets the acceleration feedforward to 200% of theoretical value.
Working with servo gains
.
•
Servo tuning process: refer to the
Hardware Installation Guide
or to the Motion Planner help
system.
•
Check the values of all active gains (
SGAF
is one of many servo gains): use
TGAIN
.
•
Creating and invoking gain sets: see
SGSET
,
SGENB
,
TGAIN
,
TSGSET
.
SGENB
Enable a Servo Gain Set
Type
Tuning
Syntax
<a_><!>SGENB<i>
Units
i
=
gain
set
identification
number
(see
SGSET
command)
Range
1 – 3
Default
n/a
Response
n/a
See Also
SFB, SGAF, SGSET, SGVF, TGAIN, TSGSET
Product Rev
GT6K n/a
GV6K 6.0
(applicable only to
servo axes)
SGENB
allows you to enable one of the three gain sets. The gain sets are established with the
SGSET
command. A gain set can be enabled during motion at any specified point in the profile, or when not in
motion. For example, you could use one set of gain parameters for the constant velocity portion of the
profile, and when you approach the target position a different set of gains can be enabled.
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