UsdKinematicsParser flip_joint_limits wrong behavior

[ChengshuLi]

1. cuRobo installation mode: python
2. python version: 3.10
3. Isaac Sim version (if using): 4.1.0

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When testing with Franka Panda, I noticed that UsdKinematicsParser flip_joint_limits seems to have the wrong behavior. Specifically, instead of

if joint_name in self._flip_joint_limits:
    joint_limits = np.ravel(
        [-1.0 * j_prim.GetUpperLimitAttr().Get(), j_prim.GetLowerLimitAttr().Get()]
    )

it should be

if joint_name in self._flip_joint_limits:
    joint_offset = [-1.0, 0.0]

I found out about this when looking at the panda_finger_joint2 link, with the following visualization.

sph = mg.kinematics.get_robot_as_spheres(joint_pos)
WorldConfig(sphere=sph[0]).save_world_as_mesh("/scr/chengshu/Downloads/robot.obj")

Before:

After:

Is my fix reasonable? Or maybe I wasn't passing in the argument correctly?

Many thanks!

[balakumar-s]

We recommend using the URDF kinematics parser. The USD parser is not fully implemented and does not work on most robot USD files.

[ChengshuLi]

@balakumar-s Thanks for the quick reply!

I understand URDF kinematics parser is more mature. However, currently I have some custom changes applied to the USD file that is not found in URDF (i.e. I manually changed stuff on the USD in Isaac Sim and saved it). Therefore, I might need to use the USD kinematics parser for the most-up-to-date information.