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ASDA-A3

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Tuning

5.7.2 Resonance suppression low-pass filter

5.7.2.1 Function restriction

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.

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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 distance between each is

small, 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 intensively 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.

3

2

BW

BW

-3dB

(1) Resonance point;

(2) Resonance suppression low-pass filter (Cut-off frequency of low-pass filter = 1000 / P2.025 Hz);

(3) Resonance point after resonance suppression

Relevant parameter

Refer to Chapter 8 for detailed descriptions of the relevant parameter.

Parameter

P2.025

Function

Resonance suppression low-pass filter

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