Rockwell Automation MPMA Integrated Multi-Axis Linear Stages - Manual (Page 126)

126 Rockwell Automation Publication MPMA-UM001B-EN-P - November 2010
Appendix D 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 methods to limit the occurrence of an E19.
• Set the Position Error Tolerance value on the Limits tab of the Axis
Properties to 10 mm.
• Modify the Position Error Tolerance value to 10 mm using a SSV
instruction code. You can use code similar to the code on page 122 which is
used to change the Bipolar Torque Limit.
Rung 6 of the ladder code opens the Position Error window. This lets the
Homing 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 box.