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Calling pick results in "No Sampler was constructed"

asked 2018-05-25 05:00:51 -0500

SC gravatar image

Hi folks,

I am trying to get a simple pick & place demo to work. Objects were added to the planning scene and are correctly shown in rviz with their according names. I am using the Franka Emika Panda simulation which is started with roslaunch panda_moveit_config demo.launch. When I use the panda_arm_hand planning group and call group.pick('my_object'), an error is displayed stating that "No sampler was constructed". In addition, maybe as a consequence of the above, the following appears in the log:

[ INFO] [1527240082.156847614]: Planning attempt 1 of at most 1
[ INFO] [1527240082.156979205]: Added plan for pipeline 'pick'. Queue is now of size 1
[ERROR] [1527240082.157460490]: No sampler was constructed
[ INFO] [1527240082.157499970]: Manipulation plan 0 failed at stage 'reachable & valid pose filter' on thread 0
[ WARN] [1527240082.158674635]: All supplied grasps failed. Retrying last grasp in verbose mode.
[ INFO] [1527240082.158787599]: Re-added last failed plan for pipeline 'pick'. Queue is now of size 1
[ INFO] [1527240082.159718144]: Manipulation plan 0 failed at stage 'reachable & valid pose filter' on thread 1
[ INFO] [1527240082.162419179]: Pickup planning completed after 0.001770 seconds

In another attempt, I supplied a list of possible (more or less meaningful) grasps to the pick method, but that didn't change the outcome.

Do you have any suggestion to get rid of this error message? I was unable to find any clue regarding this particular error message- Do I have to load any special package, configuration parameter, or must some ros node be running I am currently not aware of?

Some remarks: I work with an Rviz simulation primarily, Kinetic inside an Xenial-based Docker container. However, I observed the error message also with a real robot on a real Xenial Ubuntu System. Both Ros and Ubuntu Packages are up-tot-date. The controller invoking the pick routine is written in Python, if that matters.

Regards, SC

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answered 2018-06-15 09:02:56 -0500

SC gravatar image

Replying to myself: The problem was an outdated/erroneous MoveIt configuration for the robot. Details can be found here:

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Asked: 2018-05-25 05:00:51 -0500

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Last updated: Jun 15 '18