Notch Filter - Allen-Bradley PowerFlex 70 Reference Manual

Notch Filter

The 700 Vector has a notch filter in the torque reference loop used
Vector FV
to eliminate mechanical resonance created by a gear train. [Notch Filter Freq]
sets the center frequency for the 2 pole notch filter, and [Notch Filter K] sets the
gain.
Figure 24 Notch Filter Frequency
Gain
Notch Filter K
0 db
Notch Filter Frequency
Due to the fact that most mechanical frequencies are described in Hertz, [Notch
Filter Freq] and [Notch Filter K] are in Hertz as well. The following is an
example of a notch filter.
A mechanical gear train consists of two masses (the motor and the load) and
spring (mechanical coupling between the two loads). See
Figure 25 Mechanical Gear Train
Bm
Kspring
Jm
The resonant frequency is defined by the following equation:
=
resonance Kspring
Jm is the motor inertia (seconds)
Jload is the load inertia (seconds)
Kspring is the coupling spring constant (rad
Figure 26 shows a two mass system with a resonant frequency of 62 radians/
second (9.87 Hz). One Hertz is equal to 2ðπ radians/second.
Rockwell Automation Publication PFLEX-RM001H-EN-P - June 2013
Hz
BL
Jload
( )
Jm + Jload
-------------------------------- -
×
Jm Jload
2
/sec)
Notch Filter
Figure 25.
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