Fix overlapping variable names between robot definition files

[felixvd]

Uploading multiple different UR definitions currently breaks the previous robot definitions by overwriting their link lengths and other parameters. This commit makes the property names for each robot model unique so they are independent of the others.

See the before and after pictures in Gazebo below. The UR5 was the last model to be loaded in the scene definition, so the link lengths of the UR3 have become too long, and those of the UR10 too short.

I don't think this change affects anything outside of these files and I have had no problems using it in our own development.

[gavanderhoorn]

Thanks for the PR. This is indeed an issue.

Instead of renaming all the properties, would moving their declarations down a bit so they are inside the ur10_robot macro definition be an option?

According to wiki/xacro - Local properties:

Properties and macros defined within a macro are local to this macro, i.e. not visible outside.

[atomoclast]

One possible suggestion too is to namespace each robot. Either way this would be a great PR!

[gavanderhoorn]

@atomoclast: moving the declarations into the macro def should automatically achieve this. The properties should essentially get namespaced that way.

[felixvd]

I agree, that's the cleaner way. I updated the PR accordingly and took the liberty to remove the prefix from the kinematic parameters, too. I confirmed that it works in our simulation.

[dhled]

Tested on simulation.

[Chamango90]

Reviewed and accepted

[gavanderhoorn]

Accepting and merging this will break any urdfs that are currently directly using any of the xacro:property elements, so we will have to increase the package's version to convey that fact and post an announcement on ROS Discourse about it.

As the constants are 'almost' internal constants, I don't expect that to have happened to often, but we can still be clear about it.

For future readers: ${namespace.property} can be used to access properties inside namespaces. See also the xacro documentation on the wiki page linked to in #356 (comment).

[gavanderhoorn]

Approving based on reviews by @ipa-led and @ipa-jfh.