U511 User’s Manual The User Interface
Version 1.1 Aerotech, Inc. 3-29
Setting Bandwidth and Damping
The Bandwidth and Damping parameters specify the desired response of the motor. The
higher the Bandwidth, the better the stage performance will be. This means minimizing
velocity error, position error, and settling time. Higher Bandwidth numbers will result in
higher servo loop gains. A typical value of Bandwidth is 35 Hz.
The Damping parameter determines how the motor comes into position. A low Damping
value (.3) may allow the axis to come into position more quickly, but take longer to
completely settle. There may also be some overshoot at the end of the move. A value of .7
will ensure that there is minimal overshoot. A typical value of Damping is .5.
Procedure for Autotuning
1. Defeat Position and Velocity Error traps. This is done by modifying the
“Global fault mask” on Page 9 of the Setup Menu (see axis parameter
x55).
2. Set starting gains. If the user does not have "working" gains, set
Kpos = 1, Ki = 1000, Kp = 10,000, and Vff = 256.
3. Set excitation Distance and Frequency. Distance is in current units (mm
or in).
Typical Distance = 25 mm or 1 in (see text)
Typical Frequency = 1 Hz
4. Set desired bandwidth and damping. A Bandwidth of 10 Hz and
Damping of .5 are good starting points.
5. Run autotune by pressing the Auto key (F2).
6. Increase bandwidth by 5 Hz increments until system becomes loud or
unstable. Return to next lower bandwidth and retune.
7. Save gains to parameter file by pressing F4.
8. Re-enable Position and Velocity Error traps (see axis parameter x55).
Autotuning cannot be run on stepper motors, motors with tachometer feedback, or
dual loop systems.
See the autotuning portion of the Chapter 8 for additional information on autotuning.
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