- 126 - Aries User Guide
stabilize the system and speed up the response. It can also be used to
reduce the steady state position error.
When the proportional gain (SGP) is used alone (i.e., the other gain terms are
set to zero), setting this gain too high can cause the system to become
oscillatory, under damped, or even unstable.
SGV
Servo Gain Velocity
Type
Tuning
Product Rev
Syntax
<a_>SGV<i>
Aries 2.0
Units
i = gain value
Range
Ø.ØØ to 1ØØØ.ØØ
Default
1.4Ø
Response
SGV: <*>1.4Ø
See Also
SGILIM, SGI, SGP
This command is only valid in DMODE4 (velocity mode) and DMODE6 or 7
(position mode). SGV allows you to control the velocity feedback gain in the
servo algorithm. Using velocity feedback, the controller's output signal is
made proportional to the velocity, or rate of change, of the feedback device
position. Since it acts on the rate of change of the position, the action of this
term is to anticipate position error and correct it before it becomes too large.
This increases damping and tends to make the system more stable.
If this term is too large, the response will be slowed to the point that the
system is over-damped.
Since the feedback device signal has finite resolution, the velocity accuracy
has a limit. Therefore, if the velocity feedback gain (SGV) is too high, the
errors due to the finite resolution are magnified and a noisy, or chattering,
response may be observed.
SGVF
Velocity Feedforward Gain
Type
Tuning
Product Rev
Syntax
<a_><!>SGVF<i>
Aries 2.0
Units
N/A
Range
Ø-5ØØ
Default
1ØØ
Response
SGVF: *SGVF1ØØ
See Also
DMTD, LJRAT
Use the SGVF command to set the velocity feedforward gain. Velocity
feedforward control improves position tracking performance when the system
is commanded to move at constant velocity. The velocity tracking error is
mainly attributed to viscous friction.
The SGVF value is multiplied by the commanded velocity calculated by the
Aries drive’s move profile routine to produce an estimated torque command
that gets added to the servo control signal. The value is normalized to the
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