Problem closed loop urdf

[jlaneurit]

Hello.

I am currently working on the control of a tractor three-point hitch system under real operating conditions, for agricultural applications. A description of the three-point hitch system is provided in the image below.

As shown, two prismatic cylinders are used to raise and lower the lower arms, which support the implements. Each cylinder is connected both to the vehicle and to the lower arms.

If we attempt to create a URDF of this system, it would generate kinematic loops, which URDF does not support.

In my specific case, I would like to exclude these prismatic joints from the URDF while still keeping the system compatible with ros2_control. However, if I do this, the component throws an error because the joint is not declared, as can be seen here:
ros2_control component_parser.cpp#L1015

Proposed idea / question:
Would it be possible to add a parameter to disable parsing of mimic options? This could allow the URDF to skip these prismatic joints without causing an error in ros2_control. Alternatively, if there is another recommended solution to handle joints that should be excluded from the URDF while keeping ros2_control functional, I would be very interested in it.

Thank you for your time and any guidance you can provide.

[christophfroehlich]

It would be easier if you posted the relevant section of the URDF, especially the ros2_control code.

What hardware component are you using? GenericSystem or gz_ros2_control?, or your own custom hw plugin?

[github-actions]

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