Add URDFtoMuJoCoLoader and MujocoWrapper class

[Giulero]

Summary of PR #7 Generated by beloved Copilot assistant

Files Changed

1. examples/generate_ergoCub_xml.py (Added)

   • Demonstrates usage of URDFtoMuJoCoLoader and MujocoWrapper classes.
   • Example includes loading a URDF file, converting to MuJoCo XML, and initializing MuJoCo models.

2. mujoco_urdf_loader/init.py (Modified)

   • Imports URDFtoMuJoCoLoader, URDFtoMuJoCoLoaderCfg, ControlMode, and MujocoWrapper.

3. mujoco_urdf_loader/loader.py (Added)

   • Introduces URDFtoMuJoCoLoader class.
   • Handles loading and simplifying URDF, converting to MuJoCo XML, and setting control modes.

Summary of New Classes

• URDFtoMuJoCoLoader

  • Purpose: Converts URDF files to MuJoCo XML format.
  • Key Features:
  • Simplifies URDF using iDynTree.
  • Converts URDF to MuJoCo XML with specified control modes.
  • Adds actuators based on control modes (position or torque).

• MujocoWrapper

  • Purpose: Wrapper for MuJoCo models.
  • Key Features:
  • Initializes MuJoCo model and data from XML string.

For further details, you can view the full list of changes here.

[traversaro]

Cool! Could it make sense to update the README to advertise this class or at least link the example?

[giotherobot]

Also some tests would be nice :)

[traversaro]

Can you document in the PR add_position_actuator used to add actuators named <jointname>_motor and now is adding actuators named <jointname>_position_motor ? Thanks!

[Giulero]

Cool! Could it make sense to update the README to advertise this class or at least link the example?

Yup! I'll add some pointer there!

Also some tests would be nice :)

I agree! For now I can put one that checks that the conversion does not stop.

[Giulero]

Can you document in the PR add_position_actuator used to add actuators named <jointname>_motor and now is adding actuators named <jointname>_position_motor ? Thanks!

Actually, this is a point (and also a leftover) that I guess is worth to discuss. The order of the joints and the order of the actuators does not coincide. So I created a mapping between actuators and joints https://github.com/ami-iit/mujoco-urdf-loader/blob/51d484d513224a6f149ff76c55dccddac6922bba/mujoco_urdf_loader/wrapper.py#L20-L28

This mapping exploits the fact the the motors names are set with the same of the joints. I don't know if there is a smarter way to this mapping.

The use this mapping, also the <jointname>_position_motor should be changed to simply the joint name.

[giotherobot]

This mapping exploits the fact the the motors names are set with the same of the joints. I don't know if there is a smarter way to this mapping.

The use this mapping, also the <jointname>_position_motor should be changed to simply the joint name.

This should already work, if I'm not mistaken, since you are checking if the string joint_name is a subset of the actuator name.

[traversaro]

The existing heuristics as mentioned by @giotherobot seems to be working fine, but indeed it could could fail if some joints have some peculiar naming choice. URDFtoMuJoCoLoader knows the "real" mapping from joint to actuator, perhaps it can just pass it (optionally) to the MujocoWrapper, and if that is not present the MujocoWrapper fails back on the heuristics?

[Giulero]

The existing heuristics as mentioned by @giotherobot seems to be working fine, but indeed it could could fail if some joints have some peculiar naming choice. URDFtoMuJoCoLoader knows the "real" mapping from joint to actuator, perhaps it can just pass it (optionally) to the MujocoWrapper, and if that is not present the MujocoWrapper fails back on the heuristics?

Got it! Or another option could be to force who's using the URDFtoMuJoCoLoader to use as name of the actuators the one in the list of the controlled joints. A lazy solution to be honest.

Then I could set revert back the default name to <jointname>_motor in add_position_actuator, and just use the following lines to pass the name of the actuator (compliant with the list of actuated joints passed before)

https://github.com/ami-iit/mujoco-urdf-loader/blob/51d484d513224a6f149ff76c55dccddac6922bba/mujoco_urdf_loader/loader.py#L144-L160

[Giulero]

Reviving this PR!

• I reverted back the naming logic in the position actuator with b8f69b9.
• Readme updated in https://github.com/ami-iit/mujoco-urdf-loader/pull/7/commits/d0a3153a6ea82d3bc092b7343dbc81900dcc8a72
• Added a test for the URDFtoMuJoCoLoader class cd4f99b

[Giulero]

Ciao guys! Do you think there's something else to do for this PR?

[traversaro]

Ok for me!