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README.md

Kinova Gen3 Description (MJCF)

Important

Requires MuJoCo 2.3.3 or later.

Overview

This package contains a simplified robot description (MJCF) of the Kinova Gen3 developed by Kinova Robotics. It is derived from the publicly available URDF description.

MJCF derivation steps

  1. Converted xacro to URDF: rosrun xacro xacro gen3.xacro > gen3.urdf
  2. Added the following to the URDF's <robot> clause:
<mujoco>
  <compiler meshdir="assets" discardvisual="false" fusestatic="false"/>
</mujoco>

Note fusestatic="false" is needed so that base_link is preserved.

  1. Converted to MJCF:
import mujoco
model = mujoco.MjModel.from_xml_path('gen3.urdf')
mujoco.mj_saveLastXML('gen3.xml', model)
  1. Cleaned up the MJCF file as follows:
    • Added option: <option integrator="implicitfast"/>.
    • Replaced type="mesh" contype="0" conaffinity="0" group="1" density="0" rgba="0.75294 0.75294 0.75294 1" with class="visual" and added the class to defaults.
    • Replaced type="mesh" rgba="0.75294 0.75294 0.75294 1" with class="collision" and added the class to defaults.
    • Deleted <body name="end_effector_link"> entirely and replaced with <site name="pinch_site" pos="0 0 -0.061525" quat="0 1 0 0"/>.
  2. Added the following to the MJCF:
    • Added wrist camera: <camera name="wrist" pos="0 -0.05639 -0.058475" quat="0 0 0 1" fovy="41.83792730009236" resolution="640 480"/>.
    • Added position actuators with joint limits on joints 2, 4, and 6.
    • Added keyframes for "home" and "retract".
  3. Added scene.xml which includes the robot, with a textured groundplane, skybox, and haze.

Robotiq 2F-85

Do not include the Robotiq mechanical coupling used in arms such as the UR and Franka since for the Kinova Gen3, it is built into the end effector interface. Specifically, if using Menagerie's robotiq_2f85, the "base_mount" link (mechanical coupling) should be excluded. Instead, the "base" link should be directly mounted at pose pos="0 0 -0.06149039" quat="0 -1 1 0" like so:

<body name="base" pos="0 0 -0.06149039" quat="0 -1 1 0" childclass="2f85">
  ...
</body>

The end effector site should also be shifted by an additional 0.12 to match the behavior of Kinova Kortex API:

<site name="pinch_site" pos="0 0 -0.181525" quat="0 1 0 0" group="3"/>

License

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

Acknowledgement

This model was graciously contributed by Jimmy Wu.