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UniversalRobots / Universal_Robots_ROS2_Description

ROS2 URDF description for Universal Robots
BSD 3-Clause "New" or "Revised" License
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Name of the Links #45

Closed LucaBross closed 1 year ago

LucaBross commented 1 year ago

I try to understand how every link is named. Since I´m a new user i don`t know if it is better to ask this question here or in the UR Forum because this is not really a issue with the description.

I made a example picture of my understanding of the names. Link_names

But I´m not sure about the last two links. Is wirst_3_link and flange the same? I already had a Look at the model.pdf Link_names_ur Here the wirst_1_link and the wrist_2_link is what i just called wrist_1_link, right? and the EE Link is the flange?

For my understanding of links, it is a riggid element between two joints.

When i start the moveit_config i saw there is additionaly base ,base_link_interia, tool0 and ft_frame. With tool0 i can imagine it is a just a empty link in case a tool will be attached. base and base_link is maybe the same? base_link_interia is maybe needed for Gazebo? But with ft_frame i have no clue what it could be.

fmauch commented 1 year ago

Looking at RViz might be more helpful, in fact

image

simply run e.g. ros2 launch ur_description view_ur.launch.py ur_type:=ur5e to view the ur5e model. In RViz, you can add a TF display to inspect all the frames. The frames basically follow this convention. The position of a couple of frames are the same, but the orientation might be different.

I'm not be sure TBH, why we still kept the model.pdf inside the repo, as it seems to no longer perfectly reflect the URDF.

LucaBross commented 1 year ago

Ah, okey. Thanks for this. In this case the Picture i posted above is right? Or can you find anything thats wrong in this. I`m a little bit confused about the shoulderlink and the upper arm link, because their coordinate system start at the the same point.

fmauch commented 1 year ago

I don't quite remember, but I think that had to do with the COGs and / or the robot calibration.