Make sure you have the newest version of urdf2webots installed. If you have an older version installed via pip, use this command:
pip install --no-cache-dir --upgrade urdf2webots
Alternatively, if you want to install from source, follow the instructions in the main README
Example using this Kuka ROS repo: https://github.com/ros-industrial/kuka_experimental
cd catkin_ws/src
git clone https://github.com/ros-industrial/kuka_experimental
cd ..
catkin_make # or catkin build depending on what you use
source devel/setup.bash
Note: If you want to convert this exact same robot, you will have to replace the file at
kuka_experimental/kuka_lbr_iiwa_support/meshes/lbr_iiwa_14_r820/visual/base_link.dae
with this (original file is corrupted):
base_link.dae
To follow the below instructions, you'll need to have the xacro tool installed; some ROS installations don't include it by default. If you don't have it, you can install it as follows on Ubuntu (substitute your ROS distribution for "noetic"):
sudo apt install ros-noetic-xacro
Navigate to the launch folder and open the launch file that launches your robot or displays it in Rviz. For this tutorial we chose the KUKA lbr iiwa robot. The launch file is:
/kuka_experimental/kuka_lbr_iiwa_support/launch/load_lbr_iiwa_14_r820.launch
Opening the launch file we look for the line, uploading the robot_description parameter, here it is this line:
<param name="robot_description" command="$(find xacro)/xacro.py '$(find kuka_lbr_iiwa_support)/urdf/lbr_iiwa_14_r820.xacro'" />
This tells us which xacro file and with what parameters we need to generate our URDF from. Next in your Terminal, navigate to the urdf folder specified in the launch file and enter following command:
cd src/kuka_experimental/kuka_lbr_iiwa_support/urdf
rosrun xacro xacro --inorder -o model.urdf lbr_iiwa_14_r820.xacro
This will compile the URDF from the XACRO file and save it as model.urdf in the same directory. If your launch file added parameters to the XACRO calls, you need to add them here too.
Convert the model.urdf with the following command. I recommend the 2 added parameters: --box-collision: simplifies objects. This can greatly improve the simulation of object interactions, especially grasping.
--multi-file: puts the mesh data in a separate file. If not set, the proto file becomes huge and very slow and sluggish in all editors / IDEs I tried.
--static-base and --tool-slot=tool0 are more specific for robotic arms. Have a look at all options and explanations below. To figure out, what the --tool-slot=LinkName is called for your robotic arm, you will have to open the model.urdf and figure out what the link is called.
--rotation="1 0 0 -1.5708" will change the default rotation of the converted model, so that the z-axis points up. If we were not to set this, the robot would spawn sideways when adding to Webots, where the y-axis is "up" by default.
python -m urdf2webots.importer --input=model.urdf --box-collision --multi-file --static-base --tool-slot=tool0 --rotation="1 0 0 -1.5708"
Check the main README for a list of all options.
After your file has been converted, you should have something like this:
Copy these files to your project’s protos directory (of course you can do this step by using your OS's GUI):
cp -r KukaLbrIiwa14R820* ~/my_simulation/protos/
Launch Webots and your project world. Click on the plus sign to add your model.
You should see your newly converted model under PROTO nodes (Current Project).
Select it and click Add
It should look similar to this:
If something is not right, such as orientation, right-click on the robot in the Scene Tree and select View PROTO Source.
This should open the PROTO file in Webot’s text editor and should look something like this:
The fields in the header correspond to the fields (parameters) we see in the Scene Tree (compare image above and below)
For example, in order to change the default orientation of our model, we can change the rotation field in the PROTO file. The following is an example, how it would look like, if we had not parsed the --rotation="1 0 0 -1.5708" option at the start. Most URDF models use the z-axis as up, while Webots, by default, uses the y-axis as up. In this specific case, change the line:
field SFRotation rotation 0 1 0 0
to
field SFRotation rotation 1 0 0 -1.5708
If these are not the correct values, you can manually adjust the values of your robot node in the scene tree (left side), until the robot is positioned correctly. Then simply copy and paste the values into the PROTO source.
Dont forget to save the file (Ctrl + S). In order to see the changes to your PROTO file in action, either save your world and reload it, or delete the robot and add it again.