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Generating Botzo URDF

Documentation on how to build our URDF from STL file

A URDF is a file used i robotics to import the robot in a simulation. It uses the STL/CAD files as a base. Assemble them with rigid or rotatory joins, and save positions of each bone and pivot in the joints. To sum up, it is file that describe your robot in deep details and precision.

Download our URDF here

Resources

Visit directly the repos if you don't understand something. This is a resume of what they do:

Prepare STL

As stated in the Fusion2PyBullet repo, we must prepare our STL file properly.

  1. All bodies/peaces/future links must be components.
  2. Add physical materials
  3. Add joint to connect all components. In fusion you can select various type of joint (static, rotational, etc...) and also the pivot point.
  4. Call one componet as base_link
  5. Remove links of comonents (if the are right clik on it and press Break Link) Result: https://github.com/IERoboticsAILab/botzo/blob/main/media_assests/fusion_joints_one_leg.mp4 result

  6. Check STL joint-link structure using Webgraphviz. Here how:

  7. Download Joint2Graphviz repo as a ZIP.

  8. Extract the ZIP in a known directory.

  9. Open terminal:

    cd <path to Joint2Graphviz>

Copy-Item ".\Joint2Graphviz-master\" -Destination "${env:APPDATA\Autodesk\Autodesk Fusion 360\API\Scripts\" -Recurse

    For me was:

     cd C:\Users\orlan\OneDrive\Desktop\side_projects\Joint2Graphviz-master

 Copy-Item "..\Joint2Graphviz-master\" -Destination "..\..\..\..\AppData\Roaming\Autodesk\Autodesk Fusion 360\API\Scripts\" -Recurse

  10. Now the script to create a .txt file for your link graph is added to fusion

  11. Open fusion
  12. Open the file of the robot
  13. Go to utility > Addins
  14. Under My Script you should see Joint2Graphviz
  15. Press it. It will create a graph.txt
  16. Copy and pase the text content to Webgraphviz and check your robot tf structure to be valid.

(for more infors check Joint2Graphviz readme)

Warning

  1. We discovered that URDF does NOT suport close loop. Our leg design is one big close loop. You can check wrong_graph folder to see a graph with a close loop... The URDF won't work if there is a close loop

Export URDF

  1. Download Fusion2PyBullet as a ZIP
  2. Extract the ZIP in a known directory.
  3. Open terminal:
cd <path to Fusion2PyBullet>

Copy-Item ".\URDF_Exporter\" -Destination "${env:APPDATA}\Autodesk\Autodesk Fusion 360\API\Scripts\" -Recurse

For me was:

    PS C:\Users\orlan\OneDrive\Desktop\side_projects\Fusion2PyBullet-master> Copy-Item ".\Bullet_URDF_Exporter\" -Destination "..\..\..\..\AppData\Roaming\Autodesk\Autodesk Fusion 360\API\Scripts\" -Recurse
  1. Open fusion > utils > addins > my scripts > Bullet_URDF_Exporter
  2. My URDF here

(for more infors check fusion2urdf readme or Fusion2PyBullet readme)

BOTZO URDF REPO