Universal Robots UR3e Description (MJCF)

Requires MuJoCo 2.3.3 or later.

Overview

This package contains a simplified robot description (MJCF) of the UR3e developed by Universal Robots. It is derived from the publicly available URDF description.

URDF → MJCF derivation steps

1. Converted the DAE mesh files to OBJ format using Blender.
   • In this process, the Z axis of the joint that a link is connected to should point up.
2. Processed .obj files with obj2mjcf.
3. Added <mujoco> <compiler discardvisual="false"/> </mujoco> to the URDF's <robot> clause in order to preserve visual geometries.
4. Loaded the URDF into MuJoCo and saved a corresponding MJCF.
5. Added a tracking light to the base.
6. Manually edited the MJCF to extract common properties into the <default> section.
7. Manually edited colors to match UR3 colors.
8. Added position-controlled actuators and joint damping and armature. Note that these values have not been carefully tuned -- contributions are more than welcome to improve them.
9. Added home joint configuration as a keyframe.
10. Manually designed collision geometries to be as realistic as the UR3's shape.
11. Added scene.xml, which includes the robot, with a textured ground plane, skybox, and haze.

Notes

Although the model is stable in the scene.xml, you might see unstable behavior when combined with other models (i.e., Robotiq-2F85 gripper). Switching the integrator from Euler to RK4 helps in these cases.

License

This model is released under a BSD-3-Clause License