Rockwell Automation MPAS Integrated Linear Stages - Manual (Page 102)

102 Rockwell Automation Publication MP-UM001D-EN-P - September 2013
Appendix E Home to Torque-level Example
Potential for Position Error When executing a torque limit homing procedure there is potential for a position
error. As mentioned earlier, for the home to torque limit to complete, the output
torque to the motor must reach or exceed the specified torque level for a set time
of 500 ms. During this time the axis is against the mechanical hard-stop, and
following error is increasing in the position loop. If the Position Error Tolerance
value is exceeded before completion of the homing instruction, a Position Error
(E19) results.
There are two ways to limit the occurrence of an E19.
• Set the Position Error Tolerance value on the Limits tab of the Axis
Properties to a value high enough to eliminate an error from occurring.
• Modify the Position Error Tolerance value via an SSV instruction similar
to the method used in code above to change the Bipolar Torque Limit.
Rung 6 of the ladder code opens the Position Error window. This lets the
Homing to complete without causing a Position Error. The original value is reset
after Homing completes.
TIP The second method is preferred because it temporarily sets Position
Error Tolerance to a value appropriate for homing to a mechanical
hard-stop and then resets it to the original value set in the Axis
Properties dialog.