6 Adjustment
121 SD780 Series Servo Technical Manual
6.6.3 Speed Feedforward
Feedforward is the function of feedforward compensation to shorten the positioning time during
position control.
The speed feedforward is divided into internal speed fee forward (Pn121/Pn122) and analog (V-
REF) given speed feedforward (using V-REF as speed feedforward selection Pn123). This
command is sent to the servo unit together with the position command.
Related parameters
Function
code
Parameter
Range
Default
Unit
Communication
address
When
enabled
Pn121
Speed
feedforward
gain
0
～
100
0
%
0x0121
Immediately
Speed feedforward is a function to shorten the positioning time. This function is
effective when the servo unit performs position control.
Note: When the feedforward command is too large, position overshooting will
occur. Please check the response and set appropriately.
Pn122
Speed
feedforward
filter time
0
～
64
0.00
ms
0x0122
Immediately
Speed feedforward low-pass filter time constant, which can slow position overshoot
and torque jump caused by feedforward.
Pn123
Use V-REF
as speed
feedforward
selection
0x00
～
0x01
0
－
0x0123
After restart
Speed feedforward is a function to shorten the positioning time. It is possible to
select speed feedforward given via external analog V-REF.
0-None.
1-Use V-REF as speed feedforward input.
Position loop gain
Pn103
/COIN
Switching condition is met
Waiting time
Pn114
Switching time
Pn112
The second position
loop gain Pn107
ON
OFF
