create_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:

• Webgraphviz
• Joint2Graphviz repo zip
• Fusion2PyBullet repo zip
• fusion2urdf <-- deprecated

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/botzo-team/our_images_and_videos/blob/main/fusion_joints_one_leg.mp4

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

   • Download Joint2Graphviz repo as a ZIP.

   • Extract the ZIP in a known directory.

   • 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

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

   • Open fusion

   • Open the file of the robot

   • Go to utility > Addins

   • Under My Script you should see Joint2Graphviz

   • Press it. It will create a graph.txt (see mine here)

   

   • Copy and pase the text content to Webgraphviz and check your robot tf structure to be valid.

(for more infors check Joint2Graphviz readme)

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7. 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

leg:

Body:

---

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

4. Open fusion > utils > addins > my scripts > Bullet_URDF_Exporter

5. My URDF here

(for more infors check fusion2urdf readme or Fusion2PyBullet readme)