Emerson Control Techniques Epsilon Eb Series Reference Manual page 158

When Feedforwards are enabled, the accuracy of the Inertia Ratio and Friction parameters is
very important. If the Inertia Ratio parameter is larger than the actual inertia, the result would
be a significant velocity overshoot during ramping. If the Inertia parameter is smaller than the
actual inertia, velocity error during ramping will be reduced but not eliminated. If the Friction
parameter is greater than the actual friction, it may result in velocity error or instability. If the
Friction parameter is less than the actual friction, velocity error will be reduced by not
eliminated.
Feedforwards can be enabled in any operating mode, however, there are certain modes in
which they do not function. These modes are described in table below.
Operating Mode
Analog Velocity
Preset Velocity
Pulse/Position
Summation
* EN revision B6 or later.
Low Pass Filter Enable and Frequency
The drive provides a low pass filter which may be used to reduce machine resonance due to
mechanical coupling or other flexible load components. The low pass filter filters the torque
command generated by the velocity loop. It is not active in Torque mode.
The low pass filter's frequency must be at least 2.5 times greater than the actual velocity loop
bandwidth. If there is no noticeable mechanical resonance effecting the system, the system is
better off without the low pass filter. If the system has a mechanical resonance effecting the
performance, the low pass filter can diminish the effects of the resonance and allow the tuning
response parameter to be increased.
The low pass filter may improve system performance when there is an inertia mismatch
between the load and the motor inertia causing compliance in the effective load shaft. For
example, if an EN-214/MG-490 drive motor combination is driving a 16-inch long ne-inch
steel shaft with a 40:1 inertia mismatch, the highest the tuning can be set to is 1 hertz. If the
low pass filter is enabled at a frequency of 70 hertz, the system's tuning response may be set
to 15 hertz.
Line Voltage (EN Only)
Line Voltage specifies the applied power and adjusts the internal gains to compensate for it.
This parameter has two choices 115 VAC and 230 VAC. If the Line Voltage is set to 230
VAC when the actual applied voltage is 115 VAC, the motor will be slightly less responsive
to commands and load disturbances.
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Tuning Procedures
Feedforward Parameters Active
Accel FF
No
Yes
No
Yes
Vel FF
Yes
Yes
Yes
Yes
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