11-31
11-11 Feed-forward Function
OMNUC G5-series AC Servomotors and Servo Drives User’s Manual (with Built-in EtherCAT Communications)
11
Adjustment Functions
Torque Feed-forward Operating Method
1. Set the Inertia Ratio (3004 hex).
Set the inertia ratio as correctly as possible.
 If the inertia ratio is calculated for the selected motor, input the calculated value.
 If the inertia ratio is not known, perform autotuning and set the inertia ratio.
2. Set the Torque Feed-forward Command Filter (3113 hex).
Set it to approx. 50 (0.5 ms).
3. Adjust the Torque Feed-forward Gain (3112 hex).
Gradually increase the value of the Torque Feed-forward Gain (3112 hex).
Since the position error during acceleration/deceleration at a constant speed can be brought
close to 0, it can be controlled almost to 0 throughout the entire operation range during a
trapezoidal speed pattern under ideal conditions where no disturbance torque is working.
In reality, disturbance torque is always applied and, therefore, the position error cannot be
completely 0.
Torque feed-forward can reduce the position error in a range of constant acceleration/
deceleration.
Precautions for Correct Use
 If you increase the torque feed-forward filter time constant, the operation noise will be reduced.
However, the position error where the acceleration changes will become larger.
 The torque feed-forward function cannot be used when realtime autotuning is being used. Set both
the Torque Feed-forward Gain (3112 hex) and Torque Feed-forward Command Filter (3113 hex)
to 0.
Command
speed
Motor speed
Position error
Speed Feed-forward Gain = 100 [%] (fixed)
100
[%]
0
[%]
Torque
Feed-forward Gain
50
[%]
Time
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