Yaskawa Sigma Mini - Manual (Page 257)

A.3 Adjusting a Position-control Servopack
— A-11 —
4) It is not necessary to change the torque reference filter time constant (Cn-17) unless tor-
sional resonance occurs in the machine shafts.
Torsional resonance may be indicated by a high vibration noise. Adjust the torque refer-
ence filter time constant (Cn-17) to reduce the vibration noise.
5) Finally, fine adjustment of the position gain, speed gain, and integration time constant is
required to determine the optimum point for step response, etc.
Functions to Improve Response
The mode switch, feed-forward, and bias functions improve response.
However, they are not certain to improve response and may even worsen it in some
cases. Follow the points outlined below and observe the actual response while making
adjustments.
Mode Switch
The mode switch improves the transition characteristics when the torque references be-
come saturated during acceleration or deceleration.
Above the set level, the speed loop control switches from PI (proportional/integral) con-
trol to P (proportional) control.
Feed-forward Function
Use feed-forward to improve the response speed. However, feed-forward may be inef-
fective in systems where a sufficiently high value of position loop gain is not possible.
Follow the procedure below to adjust the feed-forward amount (Cn-1D).
a) Adjust the speed loop and position loop, as described above.
b) Gradually increase the feed-forward amount (Cn-1D), such that the positioning com-
plete (/COIN) signal is output early.
At this point, ensure that the positioning complete (/COIN) signal breaks up (alter-
nately turns ON/OFF) and that the speed does not overshoot. These problems can
arise if the feed-forward is set too high.
This filter can be used to correct breakup (alternately turning ON/OFF) of the position-
ing complete (/COIN) signal or speed overshoot arising when feed-forward is acti-
vated.
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