Extending a Robot Model

Xacro conventions

We use the following xacro naming conventions to improve reusability of the files:

• *.urdf.xacro: This is a top-level xacro file your launch file will use to generate the full robot description (as a URDF).

• *_urdf_macro.xacro: This file only contains xacro:macro definitions that generate URDF for use in *_urdf.xacro or other *_urdf_macro.xacro files.

• *_ros2_control_macro.xacro: Similarly, this file only contains xacro:macro definitions that generate ros2_control tags for a URDF.

Example top-level xacro composition

Below are examples show how to reuse the provided descriptions files. The tree structure reflects the xacro:include hierarchy of xacro files.

For URDF visualization

package://fanuc_crx_description/crx10ia.urdf.xacro provides an example of basic URDF formation without extensions for ros2_control.

├── package://fanuc_crx_description/crx10ia.urdf.xacro
│   ├── package://fanuc_crx_description/crx10ia_urdf_macro.xacro
|       ├── package://fanuc_crx_description/fanuc_common_urdf_macro.xacro

For physical hardware

package://fanuc_hardware_interface/crx10ia.urdf.xacro provides an example of using the fanuc_crx_description xacro:macro definitions and augmenting them with ros2_control tags.

├── package://fanuc_hardware_interface/crx10ia.urdf.xacro
│   ├── package://fanuc_crx_description/crx10ia_urdf_macro.xacro
|       ├── package://fanuc_crx_description/fanuc_common_urdf_macro.xacro
│   ├── package://fanuc_hardware_interface/crx_physical_ros2_control_macro.xacro

For mock hardware

package://fanuc_hardware_interface/crx10ia.urdf.xacro accepts a xacro argument use_mock the selects which of the packaged ros2_control xacro:macro definition files to use. When use_mock is set to true, the crx_mock_ros2_control_macro.xacro file is selected instead of crx_physical_ros2_control_macro.xacro.

├── package://fanuc_hardware_interface/crx10ia.urdf.xacro
│   ├── package://fanuc_crx_description/crx10ia_urdf_macro.xacro
|       ├── package://fanuc_crx_description/fanuc_common_urdf_macro.xacro
│   ├── package://fanuc_hardware_interface/crx_mock_ros2_control_macro.xacro

For your custom simulation

This file structure enables simple reuse of CRX URDF macros with custom ros2_control tags in the case you leverage other simulators. In this case, your top-level xacro would expose additional xacro arguments to select the additional simulator and use the corresponding ros2_control xacro:macro definition file.

├── package://MY_WORKCELL/crx10ia.urdf.xacro
│   ├── package://fanuc_crx_description/crx10ia_urdf_macro.xacro
|       ├── package://fanuc_crx_description/fanuc_common_urdf_macro.xacro
│   ├── package://CUSTOM_SIMULATOR/crx_CUSTOM_ros2_control_macro.xacro

For your custom workcell with a gripper

Finally, as you incorporate additional URDF and ros2_control definitions to your robot, we recommend a file structure similar to the below.

├── package://MY_WORKCELL/MY_ROBOT_GEN1.urdf.xacro # Defines the robot base geometry
│   ├── package://fanuc_crx_description/crx10ia_urdf_macro.xacro
|       ├── package://fanuc_crx_description/fanuc_common_urdf_macro.xacro
│   ├── package://fanuc_hardware_interface/crx_physical_ros2_control_macro.xacro
│   ├── package://GRIPPER_VENDOR_DESCRIPTION/GRIPPER_urdf_macro.xacro
│   ├── package://GRIPPER_VENDOR_DESCRIPTION/GRIPPER_physical_ros2_control_macro.xacro

This will improve composability as the robot is refined.

├── package://MY_WORKCELL/MY_ROBOT_GEN2.urdf.xacro # Defines the robot base geometry
│   ├── package://fanuc_crx_description/crx10ia_urdf_macro.xacro
|       ├── package://fanuc_crx_description/fanuc_common_urdf_macro.xacro
│   ├── package://fanuc_hardware_interface/crx_physical_ros2_control_macro.xacro
│   ├── package://GRIPPER_VENDOR_2_DESCRIPTION/GRIPPER_urdf_macro.xacro
│   ├── package://GRIPPER_VENDOR_2_DESCRIPTION/GRIPPER_physical_ros2_control_macro.xacro