Barkour contact parameters

[Nate711]

This model might be missing the impratio setting which is important to allow soft foot contact but limit slipping. The other quadrupeds set it to 100. I also noticed the solimp="0.015 1 0.031" line is setting the d_width (compression distance) to 31mm which I think is bigger than Barkour's foot.

mujoco_menagerie/google_barkour_vb/barkour_vb_mjx.xml

Line 14 in 66080c4

<geom type="sphere" size="0.0175" pos="-0.21425 -0.0779806 0" rgba="1 0 0 1" solimp="0.015 1 0.031" friction="0.8 0.02 0.01"/>

Reference:

mujoco_menagerie/unitree_a1/a1.xml

Line 4 in 66080c4

<option cone="elliptic" impratio="100"/>

[kevinzakka]

@Nate711 impratio is not currently available in MJX (will be in the upcoming release).

Adding @btaba and @yuvaltassa to chime in about the solimp parameter.

[btaba]

Hi @Nate711 , indeed impratio helps limit slipping and will be available in the next MuJoCo release, hence why it is omitted from the vB XML. The foot diameter for the vB is 35mm, similar to the A1 at 40mm, which uses the same solimp param.

[Nate711]

Thanks for the replies! The regular barkour also doesn't have impratio FYI. https://github.com/google-deepmind/mujoco_menagerie/blob/66080c4bb74969c4508dc6663e0f9f5242ee9e13/google_barkour_vb/barkour_vb.xml

Also I think the 31mm d_width for the A1 was copied from anymal

mujoco_menagerie/anybotics_anymal_c/anymal_c.xml

Line 20 in 66080c4

<geom type="sphere" size="0.03" pos="0 0 0.02325" priority="1" solimp="0.015 1 0.031" condim="6"