Download Chapter 2

Chapter 4
Operation
■
Operation
Speed command
When bias is set
No bias
Bias addition band
(Pn108)
Bias
(Pn107)
Position error pulses
Bias
(Pn107)
Bias addition band
(Pn108)
4-7-2 Feed-forward Function (Position)
■
Functions
• This function shortens positioning time by automatically, in the Servo Driver, adding the position
command value differential to the speed loop.
• Perform feed-forward compensation to increase Servo gain efficiency, thus improving response.
There is very little effect, however, on systems with sufficiently high position loop gain.
■
Parameters Requiring Settings
Parameter
No.
Pn109
Pn10A
Parameter name
Feed forward amount
Feed forward command filter
Explanation
Set the feed-forward gain (setting rage: 0 to 100
(%)).
Set the feed-forward command filter (primary
lag). (Setting range: 0 to 6400 (× 0.01 ms).)
Reference
4-3-3 Parameter
Details
4-3-3 Parameter
Details
Note When not using the feed-forward function, set Pn10A to 0.
■
Setting Procedure
• Finish adjusting the gain before adjusting the feed-forward.
• Increase the Pn109 (feed-forward amount) setting until positioning time is minimal. At this point, if
there are no problems with using overshoot, adjustments are complete. A high setting may cause
the machinery to vibrate. With ordinary machinery, set the gain to 80% maximum. (Adjust the gain
while checking the machine response.)
• If the overshoot is too large, increase Pn10A (feed-forward command filter) to reduce the it.
• In the Servo Driver, feed forward compensation is applied to position control. This function is used
to shorten positioning time. If the value is set too high, the machinery may vibrate. Set it to 80% or
less.
4-104