Rockwell Automation 20B PowerFlex 70, PowerFlex 700 Reference Manual - Manual (Page 121)

Notch Filter
Rockwell Automation Publication PFLEX-RM001H-EN-P - June 2013 121
Notch Filter
The 700 Vector has a notch filter in the torque reference loop used
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
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 .
Figure 25 Mechanical Gear Train
The resonant frequency is defined by the following equation:
Figure 26 shows a two mass system with a resonant frequency of 62 radians/
second (9.87 Hz). One Hertz is equal to 2ð
π
radians/second.
Vector FV
Gain
0 db
Hz Notch Filter Frequency
Notch Filter K
Kspring
BL Bm
Jm Jload
Jm is the motor inertia (seconds)
Jload is the load inertia (seconds)
Kspring is the coupling spring constant (rad
2 /sec)
resonance Kspring
Jm Jload +
( )
Jm Jload
Ч
--------------------------------- =