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Sigma II User's Manual
Feed-forward Function
The responsiveness is increased by using the feed-forward function. This function is
not effective if the position loop gain is set to a high value. Adjust the feed-forward
set value of Pn109 as described below.
1. Adjust speed and position loops according to the method described on this page.
2. Gradually increase the set value of Pn109 so that the positioning completion sig-
nal (/COIN) will be output quickly.
Make sure that the positioning completion signal (/COIN) does not bounce (i.e.,
turned on and off repeatedly within a short period) and that speed overshoot does
not occur. These will likely to occur if the feed-forward value is too high.
It is possible to add a primary delay filter (to be set in Pn10A) to the feed-for-
ward function. The primary delay filter may prevent the positioning completion
signal from bouncing and the system speed from overshooting.
Bias Function
This function adds the bias set in Pn107 to the output (i.e., speed reference) of the
error counter if the number of accumulated pulses of the error counter exceeds the
bias increment width set in Pn108. The bias will not be added if the output is within
the bias increment width. As a result, the number of accumulated pulses of the error
counter decreases and the time required for positioning can be shortened.
If the bias set value of Pn107 is too large, the motor speed will be unstable. The
optimum bias value varies with the load, gain, and bias increment width. Make bias
adjustments while observing the response. When not using this function, set Pn107
to 0.
Speed
Speed
reference
Bias
Pn107
OFF
ON
6-32
Chapter 6: Servo Adjustment
Motor speed without bias function
Motor speed with bias function
Time
Bias increment width
(Accumulated pulse setting)
OFF
Pn108
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