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Installation manual
CNC 8055
CNC 8055i
7.
CONCEPTS
SOFT: V02.2X
Axis setting
7.5.5 Derivative (AC-forward) gain setting
With the derivative gain, it is possible to reduce the following error during the acc./dec. stages.
Its value is given by axis parameter DERGAIN (P24).
When this additional velocity command is due to fluctuations of following error, "ACFGAIN" (P46)
= NO, it is called "derivative gain".
When it is due to variations of the programmed feedrate, "ACFGAIN" (P46) = YES, it is called AC-
forward gain" since it is due to acc./dec.
Best results are usually obtained when using it as AC-forward Gain, "ACFGAIN" (P46) = YES
together with feed-forward gain.
This gain is only to be used when operating with acceleration/deceleration control.
A practical value between 2 to 3 times the Proportional Gain, "PROGAIN" (P23), may be used.
To perform a critical adjustment, proceed as follows:
• Verify that there are no oscillations of following error, In other words, that it is not unstable.
• Check,with an oscilloscope, the tacho voltage or the command voltage at the drive (velocity
command), verify that it is stable (left graph) and that there are no instabilities when starting up
(center graph) or when braking (right graph).
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