Safety Stop Category 2 with EAC Driver and External API Control SDK

[jacob-kruse]

Hello,

I am using the MoveIt2 Python API along with the EAC driver in this package to motion plan with the Kuka LBR iisy 3 r760. Recently I increased the speed of my robot and its execution, and was wondering if it was possible to call a Safety Stop Category 2 as defined in the iiQKA.OS documentation. Currently, I can press the Emergency Stop to stop the robot, if necessary, but this causes a very abrupt stop and is hard don the robot. The documentation says that a Safety Stop Category 2 occurs when you press the "pause" button or release the "start" button so figured I would try, but it did not work. I was wondering if it was possible to send a Safety Stop Category 2 with external control.

Thanks,
Jacob Kruse

[Svastits]

Hi,

If you would like a safety stop, it is not really possible using the driver, as it is not a safe system and therefore cannot be coupled to the safety of the robot.
But I think you can configure the reaction to the emergency stop in the safety configuration, maybe you can set Stop2 there (however I am not sure)

[jacob-kruse]

Thanks for the suggestion @altex111. Unfortunately, using ros2 lifecycle set robot_manager deactivate does not produce the result I desire. When this command is used, the brakes are applied instantaneously once the deactivation is processed. This is similar to a Safety Stop 1, although it is not real time. I am looking for a way to stop the robot in a gradual manner to produce less strain on the joints.

[gavanderhoorn]

If you're using a JointTrajectoryController from ros2_control, cancelling an active goal should result in a hold trajectory getting executed.

That would be somewhat similar to a -- very much non-safety-rated -- controlled stop.

[jacob-kruse]

@gavanderhoorn
Is there a terminal command to cancel the active goal? I have been searching for a way to do this for the past 45 minutes.

[gavanderhoorn]

Haven't tested it, but Easy way to cancel a ROS2 action seems to suggest this should work:

ros2 service call <service-name> action_msgs/srv/CancelGoal

See that Q&A also for a way to find <service-name>.

(you don't necessarily need to use ros2 service of course. A regular ROS 2 service client would also work)

Essentially you'd call the service with a default/zero-initialised action_msgs/srv/CancelGoal instance, which, according to the documentation:

If the goal ID is zero and timestamp is zero, cancel all goals.

As I wrote in the linked Q&A, I've always felt this is a bit of a hack, but it would be a way to cancel active goals when you don't actually 'own' them.

[jacob-kruse]

Okay, I will give this a try and let you know the results.