9-6
Tuning
Filters
The velocity regulator has one low pass filter. The filter bandwidth range is from 1 Hz to 992 Hz.
The filter serves two purposes:
•
Adjust the frequency range to remove (filter) the noise produced by encoder resolution.
•
Reduce the amount of the mechanical resonance in the mechanical system (e.g., belt sys-
tems).
Similar results may often be achieved by reducing the update rate of the velocity loop.
T
ABLE
9.2
Position Loop Gains
Parameter
Description
Kp-gain
Proportional gain of the position loop.
Kp-gain changes:
• The position loop bandwidth.
• The settling time of the position loop.
In general, the higher the value of Kp-gain the faster the settling time. However, a high value of
Kp-gain with inadequate velocity loop bandwidth results in overshoot and ringing.
Note: Kp-gain is only for use with the position following mode.
Kd-gain
Differential gain of the position loop.
Provides position loop damping and reduces overshoot caused by Kp or Ki gain.
Kff-gain
Feedforward gain of the position loop.
Kff-gain reduces following error. However, a high value of Kff-gain can result in position over-
shoot. A reduction in following error allows the system to more closely approximate gear driven
systems.
Ki-gain
Integral gain of the position loop.
Ki-gain decreases the time period for the error to decay.
A non-zero value of Ki allows integration in the position loop which eliminates the steady state
following error. However, a non-zero value for Ki may introduce overshoot and ringing, which
cause system instability (oscillation).
Note: Ki-gain is used in conjunction with the Ki Zone-value.
Ki Zone - is the area around the commanded position where Ki - gain is active.
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