6
6-53
6-16 Feed-forward Function
OMNUC G5-SERIES AC SERVOMOTOR AND SERVO DRIVE USER'S MANUAL
Applied Functions
Torque Feed-forward Operating Method
1. Set the Inertia Ratio (Pn004).
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 (Pn113).
Set it to approx. 50 (0.5 ms).
3. Adjust the Torque Feed-forward Amount (Pn112).
Gradually increase the value of Torque Feed-forward Amount (Pn112).
Since the position error during acceleration/deceleration at a certain 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 present and, therefore, the position error cannot be
completely 0.
Torque feed-forward can reduce the position error in a range of constant acceleration/
deceleration.
When operating in position control, this function normally is used together with the speed
feedforward.
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.
Command
speed
Motor speed
Position error
Speed feed-forward amount = fixed to 100 [%]
100 [%]
0 [%]
Torque
feed-forward amount
50 [%]
Time
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