Drive Configuration
Controller Tuning
Rule of thumb for an initial setup of the position controller:
1. Set Kr = 1 and Tn = 0, activate the
Bode
plot view and
Additive, Time Constant
in the
Select Con-
troller Structure
panel.
2. Choose an initial value for the gain crossover frequency
f
. For a high performance axis with
analog encoder,
f
gc
is typically in the range of 300Hz to 600Hz. For less stiff axes or encoders with
low resolution,
f
gc
may be reduced to below 100Hz to meet the stability criteria. A good starting
point is often 200Hz which can be adjusted later iteratively.
3. Based on the selected
f
gc
, initial values for the parameters
Tv
and
T1
can be calculated:
Tv
=
1
2
f
gc
T
1
=
1
20
f
gc
The angle plot should now show a sufficient phase margin
at
f
gc
of more than 30° to 50°. If this is
not the case, the gain crossover frequency
f
gc
may have to be reduced.
4. Measure the amplitude
A
gc
at frequency
f
gc
in
dB
in the bode plot with the crosshair. An initial
value for the gain
Kr
can now be calculated based on the measurement:
Kr
=
10
−
A
gc
20
The magnitude of
G
o
should now cross the 0dB level at the frequency
f
gc
.
5. Check the stability of the controller in the Bode and the Nyquist plot based on the criteria listed
above. If the stability of the controller is insufficient reduce
f
gc
or try to apply filters to compensate
unstable resonances.
6. If the stability is sufficient, the integral time constant can be set by using the following equation
as an initial value.
Tn
=
1.5
f
gc
7. Use the criteria above to further optimize the position controller. Figure 57 shows a tuned con-
troller and indicates qualitatively the effect of the parameter changes on
G
o
(f)
in the
Bode
and
Nyquits
plot.
8. Press the
Commit
button to activate the parameter changes on the drive.
11 The gain crossover frequency
f
gc
is the frequency at which the gain of the tuned controller crosses 0dB.
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