How To convert [xacro] to [urdf] for Panda robot?

Published:

(20250416).

How To convert [xacro] to [urdf] for Franka Emika Panda robot?

This post describes how you can create .urdf file from .xacro file for the Franka Emika Panda robot, based on the officially provided “franka_description (official)”.

Environment:

STEP-0: Install Docker

Docker is required for the process of xacro -> URDF. The installation is quick and easy. With the Docker, you can also run Franka’s official code to visualize the Panda robot in rviz.

$ sudo apt update
$ sudo apt install docker.io
$ sudo systemctl enable docker
$ sudo systemctl start docker
$ newgrp docker
$ whoami #this will output the USERNAME
$ sudo usermod -aG docker USERNAME
$ groups #should have "docker" as one output
$ sudo reboot #reboot or logout-login the PC is required.
$ docker run hello-world

STEP-1: Create Panda URDF from .xacro, need to do:

(1) Put the original folder “franka_description (official)” into a valid catkin_ws, ensure the subfolder “scripts” exists, which include the code (create_urdf.sh etc) will be used to create URDF files later.

(1.1) Commands for generating URDF from Franka’s xacro.

NOTE-1: Docker is required.

NOTE-2: It is better to NOT use abs-path, it may have problems when using the URDF later.

  # Start the generation of the urdf model
$ ./scripts/create_urdf.sh <robot_id> <ee_id>
  # id of the robot model: `fr3`, `fp3`, `fer`, `multi_arm`, `none`
  # id of the robot end effector: `franka_hand` (default), `cobot_pump`
  # Run the following inside *"USERNAME@RT6958U-NESR:~/catkin_ws4/src/franka_description$"*
$ cd ~/catkin_ws4
$ source devel/setup.bash #required
$ cd ~/catkin_ws4/src/franka_description
  # NOTE: It is better to **NOT** use `abs-path`, it may have problems when using the `URDF` later.
$ ./scripts/create_urdf.sh fr3 --robot-ee franka_hand --with-sc --abs-path --no-prefix 
$ ./scripts/create_urdf.sh fr3 --robot-ee franka_hand --with-sc --no-prefix
$ ./scripts/create_urdf.sh fp3 --robot-ee franka_hand --with-sc --no-prefix
$ ./scripts/create_urdf.sh fer --robot-ee franka_hand --with-sc --no-prefix
$ ./scripts/create_urdf.sh multi_arm --robot-ee franka_hand --with-sc --no-prefix

(1.2) If cmd in (1.1) does not work, run the following inside “USERNAME@RT6958U-NESR:~/catkin_ws4/src/franka_description$”:

$ python3 ./scripts/create_urdf.py fr3 --robot-ee franka_hand --with-sc --no-prefix
$ python3 ./scripts/create_urdf.py fp3 --robot-ee franka_hand --with-sc --no-prefix
$ python3 ./scripts/create_urdf.py fer --robot-ee franka_hand --with-sc --no-prefix
$ python3 ./scripts/create_urdf.py multi_arm --robot-ee franka_hand --with-sc --no-prefix
$ python3 ./scripts/create_urdf.py fr3 --robot-ee cobot_pump --with-sc --no-prefix
$ python3 ./scripts/create_urdf.py fr3 --robot-ee cobot_pump --with-sc --no-prefix

(2) In the newly generated URDF file, need to do:

  • Need to correct one conversion mistake for "fr3_link8" -> "link8".

  • The last two fingers "prismatic" -> "fixed", otherwise it will have few related errors in rviz.

STEP-2: Panda in .rviz file, needs to do:

(1) Link names do not matter, and you can leave them alone.

(2) Robot Description: /panda1/robot_description (if your publish topic name is /panda1/joint_states)

(3) Fixed Frame: link0

STEP-3: Panda in .cpp file, need to do:

(1) Ensure the joint names are exactly the same as the ones in the URDF file.

(2) The publish topic name will be /panda1/joint_states.

STEP-4: if all ok, double check with:

$ rosrun rqt_tf_tree rqt_tf_tree

(optional) STEP-5: Visualize Panda via Franka’s official code:

It would be interesting to try the officially provided code for visualizing the Panda robot in rviz, it will have an independent small panel to control each joint angle via a slider.

  # Run the following inside "USERNAME@RT6958U-NESR:~/catkin_ws4/src/franka_description$"
$ ./scripts/visualize_franka.sh arm_id:=<robot_id> 
$ ./scripts/visualize_franka.sh arm_id:=fr3 #it will show a realistic white franka robot in rviz.
$ ./scripts/visualize_franka.sh arm_id:=fp3 #it will show a realistic black franka robot in rviz.
$ ./scripts/visualize_franka.sh arm_id:=fer #it will show a realistic white franka robot in rviz.

Created on 2025-04-16.

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