11 Adjustment Functions
11-32
G5 Series AC Servo Drives With Built-in EtherCAT Communications, Linear Motor Type
1
Set the Mass Ratio (3004 hex).
Set the Mass ratio as correctly as possible.
In the Mass Ratio (3004 hex), use the estimated value obtained during realtime autotuning or
set the mass ratio calculated from the machine specifications.
2
Set the Force Feed-forward Command Filter (3113 hex).
Set the Force Feed-forward Command Filter (3113 hex) to approx. 50 (0.5 ms).
3
Adjust the Force Feed-forward Gain (3112 hex).
By increasing the Force Feed-forward Gain (3112 hex) value little by little, it is possible to reduce
the position error during acceleration/deceleration at a constant speed to close to 0. This
enables the position error to be controlled to almost 0 throughout the entire operation range
during a trapezoidal speed pattern under ideal conditions where no disturbance force is
working.
In reality, disturbance force is always applied and therefore the position error cannot be
completely “0.”
Force feed-forward can reduce the position error in a range of constant acceleration/
deceleration.
Precautions for Correct UsePrecautions for Correct Use
• If you increase the Force Feed-forward Command Filter time constant, the operation noise will
be reduced. However, the position error where the acceleration changes will become larger.
• If the the external encoder resolution is low, or if the command refresh period of host controller
is long, the Force Feed-forward output will contain a large amount of noise. In this case,
increase the value set for the Force Feed-forward Command Filter (3113 hex).
• The force feed-forward function cannot be used when realtime autotuning is being used. Set
both the Force Feed-forward Gain (3112 hex) and Force Feed-forward Command Filter
(3113 hex) objects to 0.
Force Feed-forward Operating Method
Command
speed
Motor speed
Position error
Speed Feed-forward Gain = 100 [%] (fixed)
100
[%]
0
[%]
Force
Feed-forward Gain
50
[%]
Time
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