We’ve recently updated the Stretch URDF data to include accurate mass and inertial data. As you can see in this PR, the updated URDFs include new inertial data.
The process we used to generate this data is:
- Setting material properties in CAD (for all metal and plastic parts with uniform density) to generate accurate mass properties
- For other parts (eg, cables and PCBAs) with non-uniform density, we measured the mass empirically and set it in the CAD
- Use the Solidworks to URDF exporter to generate new URDFs for the main Stretch Body, the Stretch Gripper, and the DexWrist
The process is fairly accurate. For example the Stretch Gripper CAD estimates the mass at 227g while placing it on a scale shows a mass of 224g.
We have also shared a spreadsheet containing the URDF data as well as a PDF that visually illustrates the various links and their origins (linked below). These documents may be useful for users developing new simulations.
Feel free to contact us with any questions or additional data that you may need for your work.