Section 7 — Servo Tuning
7 - 5
A summary of servo parameter functions is listed in Table 7.2-1.
Table 7.2-1 — Servo Parameter Functions
Parameter
Function
Value Set Too Low
Value Set Too High
Kp
Determines
Servo loop too soft
Servo loop too tight
stiffness of
with high following
and/or causing oscillation
servo loop
errors
Kd
Main damping
Uncompensated
Higher-frequency oscillation
factor, used to
oscillation caused by
and/or audible noise in the
eliminate oscillation
other parameters
motor caused by large ripple
being high
in the motor voltage
Ki
Reduces following
Stage does not
Oscillations at lower frequency
error during long
reach or stay at the
and higher amplitude
motions and at stop
desired stop position
Vff
Reduces following
Negative following
Positive following error during
error during the
error during the
the constant velocity phase of
constant velocity
constant velocity
a motion. Stage is ahead
phase of a motion
phase of a motion.
of the desired trajectory.
Stage lags the
desired trajectory
Aff
Reduces following
Negative following
Positive following error during
error during the
error during the
the acceleration phase of a
acceleration and
acceleration phase of
motion. Stage is ahead of
deceleration phases
a motion. Stage lags
the desired trajectory.
of a motion
the desired
trajectory
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