6.4 Speed Feedforward Function
6.4.1 Relationship between the Host Controller and SERVOPACK
6-9
6
Function/Command Related Parameter
s
6.4
Speed Feedforward Function
The speed feedforward function applies feedforward compensation to position control to
shorten the positioning time. The speed feedforward reference is created from the differential of
the position reference at the host controller. Speed feedforward is specified with VFF (speed
feedforward) in the position control command.
You can specify speed feedforward for the INTERPOLATE command.
6.4.1
Relationship between the Host Controller and SERVO-
PACK
The following figure illustrates specifying speed feedforward in a command from the host con-
troller when the SERVOPACK is performing speed control.
B
A
S
ervomotor
S
peed
feedback
Po
s
ition
feedback
Current feedback
S
ERVOPACK (when INTERPOLATE command i
s
u
s
ed)
Ho
s
t controller
Encoder divided
pul
s
e output
M
Current
control
s
ection
Power
amplifier
Divider
S
peed
conver
s
ion
Pn
3
0C
VFF
TPO
S
KFF
Differential
Pn212
ENC
KFF: Feedforward gain
S
peed feedforward
average movement time
Pn426
TFF
Torque feedforward
average movement time
Po
s
ition
reference
S
peed
control
s
ection
KFF
Differential
Differential
-
+
+
-
+
-
+
Deviation
counter
S
moothing
Electronic
gear
Po
s
ition
control
s
ection
Pn20E
Pn210
Pn811
Pn812
Pn522
Po
s
itioning
completed
width
P
S
ET