Rockwell Automation Publication 2198-UM001M-EN-P - November 2022 233
Appendix D Motor Control Feature Support
Motion Polarity Setting
The Motion Polarity setting in the Logix Designer application > Axis Properties
> Polarity does not affect SLAT behavior. However, you may require
clarification on whether to use the SLAT Min Speed/Torque or SLAT Max
Speed/Torque configuration when Motion Polarity is set to Inverted. In this
case, the velocity error that is displayed in the Logix Designer application is
inverted compared to what is actually used by the axis to control the SLAT
function. So, if the SLAT configuration is set to Min and then Motion Polarity
is switched to Inverted, change the SLAT configuration to Max.
SLAT Min Speed/Torque
SLAT Min Speed/Torque is a special mode of operation that is primarily used
in web handling applications. If the TorqueTrim attribute is less than the
torque output due to the velocity regulator's control effort, then the drive
typically operates as a torque regulator. The drive can automatically enter
velocity regulation, based on conditions within the velocity regulator and the
magnitude of the velocity regulator's output relative to the torque reference.
When used for SLAT control, an application-dependent VelocityCommand
value is applied to the drive via an MAJ instruction. An application-dependent
TorqueTrim value is also applied via cyclic write. Under normal operation,
VelocityCommand is set to a level that results in the velocity regulator's control
effort becoming saturated when the motor's speed is mechanically limited. The
TorqueReference value equals the TorqueTrim value, resulting in a positive
VelocityError value.
If the mechanical speed limitation is removed (example: web break), the motor
accelerates and VelocityError becomes negative. At this time, a forced
transition to velocity regulation occurs, and the motor's speed is regulated to
the VelocityCommand attribute.
The axis remains in velocity regulation until VelocityError exceeds
SLATSetPoint for a period of time that is specified by SLATTimeDelay. At this
point, the axis returns to operating as a torque regulator.
Figure 134 - SLAT Min Speed/Torque
See the Integrated Motion on the EtherNet/IP™ Network Reference Manual,
publication MOTION-RM003
, for more information on SLAT attributes.
Table 98 - SLAT Operation When Motion Polarity Is Inverted
Velocity Command Motion Polarity SLAT Configuration
Positive (clockwise)
Normal Min
Inverted Max
Negative (counterclockwise)
Normal Min
Inverted Max
Select Minimum of Velocity Loop Output
or Torque Command
(speed control is OFF)
Select Velocity Loop Output
(speed control is ON)
Velocity Error < 0
Velocity Error > SLAT Setpoint for SLAT Time
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