Rethink Robotics Baxter User Manual page 167

Subtask ends, whereas Subtask counts are reset when the Task completes. Due to the automatic
resetting (e.g., in a Subtask with only one Place Action, the Subtask will end when the count is sat-
isfied and then immediately reset the count). Done signals may only stay true for a short period of
time, but in any case no less than 0.5 seconds.
Q: Why doesn't my Action run the second time through even though the Ready signal has always
been true?
A: Check the count, which is only reset on the rising edge of Ready. Therefore, if you have a count
of 1 and you leave Ready true, the Action will only happen once and the count will never be reset. If
you're using Ready to control a Pick, set the count to infinity. If you're using Ready to control a
Place and are using multiple subtasks, you can either set the count to infinity and use the Skip sig-
nal to move on to the next subtask or make sure that you cycle Ready false to true to reset the
count.
Q: How do I use signaling and an external PLC to run Action Sequences out of order?
A: There are two main approaches to using signaling to run sequences out of order using an exter-
nal PLC:
1. Put multiple Action Sequences into single Subtask using the combine operation on the Task
Order screen. Use Ready signals on the Picks to choose which Action Sequence to run.
a.Counts should be set to infinity for all Picks and Places, since the single subtask never ends
and the sequence is being controlled externally.
b. The Ready signal for a Pick must be held true until the action completes. A way to reliably
synchronize is to monitor the Increment Count signal and use that to clear Ready. An alternative
approach would be to use the Increment Count on the corresponding Place, which would allow
the Pick to repeat if the part was dropped. Which approach is better is highly dependent on the
application.
2. Put each Action Sequence into its own Subtask and use the Subtask Skip signal to choose which
Subtask to run.
a. All Subtasks should have their own Skip signal connected. In the idle case, all of the Skip sig-
nals should be true.
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