Rockwell Automation Publication 2198-UM002G-EN-P - February 2019 443
Motor Control Feature Support Appendix E
Velocity Droop
The velocity droop function can be useful when some level of compliance is
required due to rigid mechanical coupling between two motors. The feature is
supported when the axis is configured for Frequency Control, Velocity
Control, or Position Control.
Closed Loop Control
The closed-loop velocity droop function is supported when configured for
either Velocity or Position control. The velocity error input to the integral term
is reduced by a fraction of the velocity regulator's output, as controlled by the
VelocityDroop attribute. Therefore, as torque loading on the motor increases,
actual motor speed is reduced in proportion to the droop gain. This is helpful
when some level of compliance is required due to rigid mechanical coupling
between two motors.
Frequency Control
The velocity droop function is also supported when configured for Frequency
Control. As the estimated Iq current within the motor increases, the velocity
reference is reduced in proportion to the VelocityDroop attribute. Therefore,
as torque loading on the motor increases, actual motor speed is reduced in
proportion to the droop gain. This is helpful when some level of compliance is
required due to rigid mechanical coupling between two motors.
Velocity Droop Attribute
IMPORTANT The closed-loop velocity droop function acts to reduce the velocity error
input to the integral term, but never changes the polarity of the velocity
error.
IMPORTANT When configured for closed-loop control, the units of the VelocityDroop
attribute are Velocity Control Units / Sec / % Rated Torque.
IMPORTANT The frequency-control velocity droop function acts to reduce the velocity
reference, but never changes the direction of the velocity reference.
IMPORTANT When configured for frequency control, the units of the VelocityDroop
attribute are Velocity Control Units / Sec / % Rated Iq Current.
ID Access Attribute Conditional Implementation
464/321 SSV Velocity Droop Velocity Units / Sec / % Rated
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