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DRIVES, MOTORS + SWITCHGEAR
Figure 6
• This time the inertia of the load exceeds the rotor inertia by 10:1.
The default servo parameters result in the large overshoot and
long settling time. The small Steady State Error is the result of
no friction present
Figure 7
• Well behaved response in spite of the 10:1 inertia mismatch
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Conclusion
It appears that the conventional wisdom on matching is valid in this
case with good response easily achieved. Note that the presence of
load friction would make system tuning more difficult. That said,
most systems tend to be dominated by inertia. The Servo Parameters
shown are by no means the only combinations possible for stable
system response. For point to point control, such as a drillingmachine,
the rise time could be shortened at the expense of overshoot. As long
Figure 6: 10:1 inertia match – default setting.
Figure 7: 10:1 inertia match – optimum settings.
Electricity+Control
July ‘16
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