NSK EDD Megatorque Motor, User Manual, Page: 212 / 398

8. More Advanced Function
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8.5.2. Digital Filter
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Caution : Use of multi-stage filters may cause the velocity loop to be out of phase,
and it may cause unstable Motor operation.
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Caution : Do not use three or more filters. If the filter frequency is too low, hunting
may occur. It is recommended to set the filter frequency greater than 100
[Hz].

The digital filter filters the torque command, which is the output of velocity loop. There are two kinds of
filter: the low-pass filter and notch filter.

Te digital filters are used for reducing in resonant noise and vibration.
Table 8-29: List of digital filter
Name (code) Function
Initial
setting
Data range Unit
FP Primary low-pass filter 0
0: Filter off
10 to 1 000
-
Hz
FS Secondary low-pass filter 0
0: Filter off
10 to 1 000
-
Hz
NP Primary notch filter 0
0: Filter off
40 to 1 000
-
Hz
NPQ Primary notch filter, Q parameter 0.25 0.10 to 5.00 -
NS Secondary notch filter 0
0: Filter off
40 to 1 000
-
Hz
NSQ Secondary notch filter, Q parameter 0.25 0.10 to 5.00 -
 Refer to “9. Details of Commands and Parameters” for details of parameters.

The figure below shows the change in the characteristics of notch filter by the parameters NPQ and NSQ
(Notch filter, primary Q parameter)

The smaller the notch filter Q is, the wider frequency control is possible, centering around the
frequency set by the notch filter.
Fig 8-12: Characteristics of notch filter
NPQ5.00
NPQ1.00
NPQ0.25
NPQ0.10
NP