ElmoMC SimplIQ Digital Servo Drives-Bell Getting Started - Manual (Page 77)

The SimplIQ for Steppers Getting Started & Tuning and Commissioning Guide
MAN-BELGS (Ver. 1.1)
77
0.3 0.32 0.34 0.36 0.38 0.4
0.2
0.24
0.28
0.32
0.36
0.4
Am
p
e
re
Tim e (sec.)
Figure 71: Zoom of current test measurement for the same controller used for Figure 68
with Notch
Remark: Figure 71 reveals two remaining oscillations, one about 75 Hz and the
other 860 Hz. The oscillation at 75 Hz is due to cogging and not due to a
mechanical resonance. In order to prove this, repeat the test with twice the
velocity command. If this frequency doubles then it is due to cogging and if it
remains the same then it is due to a resonance. The resonance at 860 Hz is very
close to half the Nyquist frequency, and may be dampened using the low-pass
filter option.
Repeat the test with different damping values according to the following
guideline:
Guideline 5: Try using the largest damping factor value, which knocks out the
resonance. Do not try using damping factors that are too small (0.07 is considered
small) because this introduces more phase delay, and it is less robust when faced
with resonant frequency variations
11 .
Continue the PI manual tuning process for designing KI and KP as described
earlier in this chapter.
11
The resonant frequency may change due to load or posture changes.