Aerotech UNIDEX 600 Series, User Manual

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U600 User’s Guide AerTune
Version 1.4
Aerotech, Inc.
5-25
Figure 5-14. Unacceptable Position Error (While Adjusting Ki)
Figure 5-15. Acceptable Position Error (While Adjusting Ki)
Depending on the application, the user does not need to be too concerned with vibration
in the axis. However, when the position error crosses through zero, it indicates the
velocity loop gain is too high, especially if maintaining position is important to the user.
This zero crossing (or position overshoot) causes the settling time to increase and the
PGain within the position loop to be increased to keep the motor on its desired trajectory.
The two servo loop gains are in effect working against each other instead of
complimenting each other.
Shown in Figure 5-15 is a graph with Ki adjusted more optimally. Observing the position
error, it is smoother and the position error does not cross through zero indicating
positional overshoot. Likewise, the velocity error has been reduced.