General Question about the reference position of joints

[MegMll]

Hi,

Thank you for the work you're doing to add models to this menagerie.

I have a question regarding one of attribute in some models. I tried loading the cassie model (agility_cassie/scene.xml) in mujoco simulator and realized that some joints position q, when loading the model, were not 0.
And when i checked the model xml (agility_cassie/cassie.xml), there is a ref attribute in some of the joints. For instance, the knees :
<joint name="left-knee" type="hinge" ref="-45" range="-164 -37" damping="1" armature="0.09344"/>

I read the documentation about this, and i don't really understand what it represent and why it needs to be added. Could you explain it with a bit more detail, please ?

Thank you in advance or your answer,

[yuvaltassa]

Presumably, this related to the values reported by the encoder on the actual robot. These numbers are from Agility, so you're better off asking them 🙂