Robotiq gripper depth compensation

asked 2018-04-06 07:42:34 -0500

Fiddle gravatar image

updated 2018-04-09 03:02:44 -0500

Hi, a quick question. The height of the Robotiq gripper changes with respect to how wide it's open. Is this depth somehow automatically compensated when planning a trajectory of UR5 robot with this gripper attached to it, for example in moveit?

EDIT: Gripper pictures docs for anyone wondering:

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No, that is not taken into account. Or at least, not automatically (how could it, this is behaviour that is rather specific to this particular piece of hardware).

gvdhoorn gravatar image gvdhoorn  ( 2018-04-06 07:52:01 -0500 )edit

So in order to account for this offset, I would need to calculate the gripper kinematics myself basing on the return value from the gripper, and feed add/subtract it from the planned value, right?

Fiddle gravatar image Fiddle  ( 2018-04-06 08:24:42 -0500 )edit

This is all just speculation (and I don't know anything about the robotiq drivers/pkgs, but: if there are JointStates, a urdf and correctly modelled kinematics, TF frames for the fingers could be published "automatically". If you then define a toolframe that lies between the fingers, and ..

gvdhoorn gravatar image gvdhoorn  ( 2018-04-06 08:35:52 -0500 )edit

.. make this dependend on the location(s) of the TFs of the fingers, you should be able to have MoveIt plan for those, instead of for tool0 (of the UR). I can't remember right now whether MoveIt is able to plan to goals that are expressed in frames other than the ones that are part of the ..

gvdhoorn gravatar image gvdhoorn  ( 2018-04-06 08:37:26 -0500 )edit

.. group it's planning for, but that would make things even easier.

Doing it manually is also an option, but doesn't seem too 'nice'.

But let's wait for some other posters, perhaps they have better suggestions.

gvdhoorn gravatar image gvdhoorn  ( 2018-04-06 08:38:08 -0500 )edit

This question is not specific enough to give a real answer. Please add screenshots to illustrate the behavior (I don't have the gripper). What do you mean by "compensated"? Will moveit avoid collisions correctly? yes, probably. Will the grasp frame automatically adapt to the size of the object ...

v4hn gravatar image v4hn  ( 2018-04-07 00:42:46 -0500 )edit

the gripper should grasp? No. But you have to compute your grasp poses yourself/via some external module anyway. So it is actually better that MoveIt does no "magic" here to compensate for something, because it would interfere with your grasp computation.

v4hn gravatar image v4hn  ( 2018-04-07 00:44:28 -0500 )edit

Altogether I don't like gvdhoorn's answer "no". It depends on the exact question.

v4hn gravatar image v4hn  ( 2018-04-07 00:45:10 -0500 )edit