Output lp filter bandwidth, Output notch filter frequency – Rockwell Automation 1784-PM16SE SoftLogix Motion Card Setup and Configuration Manual User Manual

Page 404

Publication 1784-UM003A-EN-P – June 2003

396 Motion Object Attributes

While the Vel I Gain, if employed, is typically established by the automatic
servo tuning procedure, the Pos I Gain value may also be set manually. Before
doing this it must be stressed that the Torque Scaling factor for the axis must
be established for the drive system. Refer to Torque Scaling attribute
description for an explanation of how the Torque Scaling factor can be
calculated. Once this is done the Vel I Gain can be computed based on the
current or computed value for the Vel P Gain using the following formula:

Vel I Gain = 0.25 * 0.001 Sec/mSec * (Vel P Gain)

Assuming a Vel P Gain value of 0.25 Sec

-1

this results in a Vel I Gain value of

~15.6 mSec

-1

-Sec

-1-

Output LP Filter Bandwidth

The Output LP (Low Pass) Filter Bandwidth attribute controls the bandwidth
of the drives low-pass digital output filter. The programmable low-pass output
filter is bypassed if the configured Output LP Filter Bandwidth for this filter is
set to zero (the default). This output filter can be used to filter out, or reduce,
high frequency variation of the drive output to the motor. The lower the
Output LP Filter Bandwidth, the greater the attenuation of these high
frequency components of the output signal. Unfortunately, since the low-pass
filter adds lag to the servo loop which pushes the system towards instability,
decreasing the Output LP Filter Bandwidth usually requires lowering the
Position or Velocity Proportional Gain of the system to maintain stability.

The output filter is particularly useful in high inertia applications where
resonance behavior can severely restrict the maximum bandwidth capability of
the servo loop.

Output Notch Filter Frequency

The Output Notch Filter Frequency attribute controls the center frequency of
the drive’s digital notch filter. Currently implemented as a 2

order digital

filter with a fixed Q, the Notch Filter provides approximately 40DB of output
attenuation at the Notch Filter Frequency. The programmable notch filter is
bypassed if the configured Output Notch Filter Frequency for this filter is set
to zero (the default). This output notch filter is particularly useful in
attenuating mechanical resonance phenomena.

GSV/SSV Access

Attribute Name

Data Type

Values

SSV/GSV

Output LP Filter Bandwidth

REAL

Hertz