Add option to automatically generate ros2_control's fake components description file

[JafarAbdi]

Description

Reduces the number of required trajectory execution config files for sim by 3 (out of 5), all the information needed to generate the fake components description file is already in the URDF file

See the discussion in #1261

Checklist

• Required by CI: Code is auto formatted using clang-format
• Extend the tutorials / documentation reference
• Document API changes relevant to the user in the MIGRATION.md notes
• Create tests, which fail without this PR reference
• Include a screenshot if changing a GUI
• While waiting for someone to review your request, please help review another open pull request to support the maintainers

[codecov]

Codecov Report

Merging #1283 (7cd6bc3) into main (934ac23) will decrease coverage by 0.02%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #1283      +/-   ##
==========================================
- Coverage   61.48%   61.47%   -0.01%     
==========================================
  Files         274      274              
  Lines       24940    24940              
==========================================
- Hits        15332    15329       -3     
- Misses       9608     9611       +3     

Impacted Files	Coverage Δ
...dl_kinematics_plugin/src/kdl_kinematics_plugin.cpp	75.36% <0.00%> (-1.07%)	⬇️

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[AndyZe]

I'm OK with this. It looks like you satisfied my concern from #1261

[AndyZe]

This defaults to 0.

Suggested change

	<state_interface name="velocity">
	<param name="initial_value">0.0</param>
	</state_interface>
	<state_interface name="velocity"/>

[JafarAbdi]

I was getting a warning about not explicitly setting this, @destogl is this needed?

[AndyZe]

I think you should just print a warning here. No need to maintain backward compatability in my opinion

[DLu]

As mentioned in the maintainers meeting last week, I have some code that does this the MSA side. Currently both fanuc and panda have it as part of their moveit configs.

I guess my main question is: when is the ros2_control tag need to be used?

[AndyZe]

I guess my main question is: when is the ros2_control tag need to be used?

Any time you're using ros2_control at all, that tag has to be in the URDF somewhere. Simulation or hardware

[DLu]

Any time you're using ros2_control at all, that tag has to be in the URDF somewhere. Simulation or hardware

What is the "fake" part then?

[AndyZe]

What is the "fake" part then?

Sorry I didn't understand the question completely at first. For you auto-generating these templates, this should always be fine. It's what allows the RViz simulation without needing Gazebo/Ignition. That's a nice, simple default that ought to be available for everybody in my opinion.

            <hardware>
                <plugin>fake_components/GenericSystem</plugin>
            </hardware>

If people want to start using real hardware, they'll need to add their own tag. Like here for the UR driver:

        <xacro:if value="${sim_gazebo}">
          <plugin>gazebo_ros2_control/GazeboSystem</plugin>
        </xacro:if>
        <xacro:if value="${sim_ignition}">
          <plugin>ign_ros2_control/IgnitionSystem</plugin>
        </xacro:if>
        <xacro:if value="${use_fake_hardware}">
          <plugin>fake_components/GenericSystem</plugin>
          <param name="fake_sensor_commands">${fake_sensor_commands}</param>
          <param name="state_following_offset">0.0</param>
        </xacro:if>
        <xacro:unless value="${use_fake_hardware or sim_gazebo or sim_ignition}">
          <plugin>ur_robot_driver/URPositionHardwareInterface</plugin>

[mergify]

This pull request is in conflict. Could you fix it @JafarAbdi?

[DLu]

@JafarAbdi Do you think that #1299 covers everything you wanted to do with this PR?

[mergify]

This pull request is in conflict. Could you fix it @JafarAbdi?

[tylerjw]

@AndyZe or @JafarAbdi do you know what should be done next with this change?

[mergify]

This pull request is in conflict. Could you fix it @JafarAbdi?

[tylerjw]

This PR has many conflicts and was abandoned. It seems like a useful change so I'll create an issue to track finishing this work.