SDFormat URDF

This package contains a C++ library and urdf_parser_plugin for converting SDFormat XML into URDF C++ structures. Installing it allows one to use SDFormat XML instead of URDF XML as a robot description.

Supported platforms

The package has been tested with ROS Rolling Ridley on Ubuntu Focal.

Limitations and Considerations

In general, URDF C++ structures cannot represent every possible SDFormat XML file. SDFormat XML used with this plugin must be constructed with the following limitations.

Limitations that result in Errors

This package will error and refuse to convert any SDFormat XML that violates these constraints.

Model limitations

• The XML file must contain a single <model> not in a <world>
• The <model> tag must not have a <pose>
• There must not be any nested <model>

Geometry limitations

• The only supported geometry types are <box>, <cylinder>, <mesh>, and <sphere>
• The model must not use <plane> or <heightmap>

Joint limitations

• The only supported joint types are continuous, fixed, prismatic, and revolute
• The model must not use universal, screw, revolute2, gearbox, or ball joints

Kinematic limitations

• Starting from the canonical link, the links and joints must form a tree
• No link may be a child of more than 1 joint
• The canonical link cannot be a child of any joint

Limitations that may result in Warnings

If any of these constraints are violated then the library may issue a console warning, but the model is still converted to URDF c++ structures. The warning is issued using an rcutils logger with the name sdformat_urdf.

Joint limitations

• <axis> should not use <initial_position>
• <dynamics> should not use <spring_reference> or <spring_stiffness>
• <limit> should not use <dissipation> or <stiffness>
• <joint> should not use <sensor> or <physics>

Link limitations

• <link> should not have any <light> or <sensor>

Material limitations

• Only solid color materials are supported
  • The color only uses <ambient> and <diffuse> tags of the material
  • Color is calculated as 0.4 * ambient + 0.8 * diffuse
• The model should not disable dynamic lighting using the <lighting>
• The model should not use materials with <script>, <shader>, or <pbr>
• The URDF material name assigned the name of the SDFormat <visual> containing the material, so <visual> names should be unique within the model

Changelog for package sdformat_urdf

1.0.1 (2022-06-21)

• Remove version requirement on sdformat_test_files (#15)
• Contributors: Shane Loretz

1.0.0 (2022-06-21)

• Support for universal and ball joint as floating joints #13
• Support SDFormat 12 (#12)
• Use urdfdom_headers::urdfdom_headers (#5, #6))
• Contributors: Dharini Dutia, Louise Poubel, Shane Loretz

0.1.0 (2020-11-02)

• Initial urdf parser plugin that parses sdformat (#1)
• Contributors: Shane Loretz, Addisu Z. Taddese, Steve Peters, Chris Lalancette, Eric Cousineau