Resonance Suppression Low-Pass Filter; Function Restriction; Function Description; Application Example - Delta ASDA-B3 Series User Manual

Tuning

5.7.2 Resonance suppression low-pass filter

5.7.2.1 Function restriction

5
It is recommended that the filter bandwidth (1000 / P2.025) should be 8 times (or more) the
speed loop bandwidth (P2.004 / 2π).
Note: it is recommended that you set the Analysis Type to Speed Open-loop in the System Analysis of
ASDA-Soft; the zero-crossing frequency is the speed loop bandwidth.

5.7.2.2 Function description

The current command generated in the speed loop is filtered by the resonance suppression
low-pass filter, which reduces the interference of high-frequency resonance or noise to current
control. Since the filter causes a delay in the current command, when increasing the servo
response bandwidth, you must set the time constant for the low-pass filter (P2.025) smaller.
However, it causes greater noise during motor operation.

5.7.2.3 Application example

Draw Bode plots by setting the Analysis Type to Speed Open-loop in the System Analysis of
ASDA-Soft. When there is more than one resonance point and the distribution of the resonance
points is not wide, it is advisable to use the resonance suppression low-pass filter to suppress
the resonance occurring at the resonance points within a specified range.
If the resonance frequency is known, the Notch filter works better than the resonance suppression
low-pass filter for resonance suppression. If the spectrum displays multiple resonance points
which are densely distributed, or the resonance frequency drifts significantly with time or due to
other causes, use the resonance suppression low-pass filter instead.
When P2.025 is gradually increased, the filter bandwidth becomes smaller. Although resonance
does not occur in this condition, the servo response is slower and the phase margin is reduced.
If the ratio between the filter bandwidth (1000 / P2.025) and speed loop bandwidth (P2.004 / 2π)
is too small, the system becomes unstable.
(2) Resonance suppression low-pass filter (Cut-off frequency of low-pass filter = 1000 / P2.025 Hz);
Relevant parameter
Refer to Chapter 8 for detailed descriptions of the relevant parameter.
Parameter
P2.025
5-48
BW
-3dB
(3) Resonance point after resonance suppression
2
(1) Resonance point;
Function

Resonance suppression low-pass filter

ASDA-B3
3
BW