Aerotech UNIDEX 600 Series, User Manual

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U600 User’s Guide AerTune
Version 1.4
Aerotech, Inc.
5-27
6. Set Vff = 1 to enable velocity feedforward.
The position error has been minimized during the constant velocity portion of
the move, refer to Figure 5-18.
Figure 5-18. Plot Showing Velocity Feedforward Enabled (Vff=1)
7. Minimize position error during acceleration and deceleration by increasing the
AffGain servo loop parameter.
A normal value for AffGain is typically less than 200. The AffGain servo loop parameter
reduces the large position error visible during acceleration and deceleration. Increasing
the AffGain will increase the noise produced by the axis due to the attempt of the servo
loop to compensate for velocity changes. This noise may be reduced by varying the Alpha
parameter. The Alpha parameter filters the effect of the AffGain parameter minimizing
the noise created by the velocity changes. The Alpha parameter is inversely scaled.
Setting the parameter to 65,536 produces no filtering and maximum filtering is produced
by setting the parameter to 1. Figure 5-19 shows the optimal AffGain setting for out
motor/drive/table combination. The Alpha servo loop parameter was not modified from
its default setting of 65,536 providing no filtering of the AffGain servo loop parameter.
Adjusting the AffGain servo loop parameter is optional. The user’s application may
not require it.