Waiting on a PosTable entry

[yeu-rioual]

PosTable users often uses actionID to check authorizations.
E.g. during picking trajectory, robot waits for a part to be available.

Using an actionID allows the program to hold the current trajectory until a condition becomes true.
However, if the condition is already true, the robot stops all the same, costing cycle time.

The idea is to add a waitID or reserve a special range of actionID for waiting.

Wait condition should be handled as the actionDone:

• a waitID should be used as an output. That way the user can select the right wait condition
• the result of the wait condition is transferred to a waitCondition input

Inside PosTable, the waitCondition input would be used to determine if the processed entry is a StopEntry.
Several scenarios are possible:

• waitCondition is True and remains True until the entry is passed: Robot stops and trajectory is suspended
• waitCondition is False and remains False until the entry is passed: Robot does not stop, trajectory is blended
• waitCondition is True and becomes False before the entry is passed: Robot makes a short stop. It is possible to avoid this situation by recalculating the QA
• waitCondition is False and becomes True before the entry is passed: This situation is more difficult to handle, motions may already be sent to the motion buffer. Following paragraph presents several solutions

I see 3 ways to handle the last scenario:

• Forced stop: waitID works as an actionID. This behavior is the safe choice in case of an unstable input but a disaster in terms of cycle time
• Last motion check: waitID entry is considered as a StopEntry until the index is equal to the waitID entry. That way, the waitCondition input is checked at the beginning of the motion. If the motion is long enough and waitCondition is True, no stop should occur. However, if waitCondition turns True during the waitID entry, the robot wont stop
• Hold instruction: a MLxHold stops the current trajectory. Motion resume with a MLxRestart. Only possible for a Yaskawa controller with 1 robot
  User could select how PosTable should behave with a waitBehavior input.