U511 User’s Manual Tuning Servo Loops
Version 1.1 Aerotech, Inc. 8-19
Maximize Button
Figure 8-12. MAXIMIZE Button on the Axis Scope Window
b. In the Collect menu select “2500 points.”
c. In the Display menu select “2500 points.”
d. In the Axis menu select axis number 1 (X axis) or the axis that will be tuned.
e. In the Plot menu, select Velocity Command, Velocity Error, and Position
Error.
f. In the Trigger menu, set the F
orward Motion... and Reverse Motion... to a
typical move. For metric mode, a move such as LINEAR X10 F2000 for
Forward Motion... and LINEAR X-10 F2000 for R
everse Motion... is
appropriate. For English mode, moves such as LINEAR X1 F180 and
LINEAR X-1 F180 for Forward Motion... and R
everse Motion...,
respectively, are appropriate. Also set the Sample Rate to 1.
g. In the Tools menu select Status, Control, and Gains.
When the SINGLE button is pressed, axis number 1 will first move as specified
by Forward Motion... When the SINGLE button is pressed again, axis number 1
will move as specified by Reverse Motion...
5. Adjust the Velocity Loop using “Kp” and “Ki.” The “Kpos” and “Ki” have been
set to zero (0) to eliminate the Position Loop and half of the Velocity Loop.
Thus, the only gain that is having an effect is “Kp” which is the other half of the
Velocity Loop.
Even though the user may only be concerned with how well the stage positions, the
Velocity Loop cannot be overlooked as it is interrelated to positioning. The better a
stage tracks velocity, the closer it will be to its correct position.
The objective in adjusting “Kp” is to reduce the velocity error to 5-10 steps. In
between pressing the SINGLE button, the operator should observe no screeching
and howling from the motor. Noise means “Kp” is set too high causing it to
oscillate. It may screech a little during the move, but not when at a standstill.
E
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