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Allow to override joint friction coefficients during parsing #443

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Allow to override joint friction coefficients during parsing #443

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75100b3
Allow to override joint friction coefficients
flferretti Jun 5, 2025
5d9f347
Update joint dynamics section in configuration docs
flferretti Jun 5, 2025
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11 changes: 11 additions & 0 deletions docs/guide/configuration.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -47,10 +47,21 @@ Joint Dynamics
~~~~~~~~~~~~~~
Joint dynamics are configured using environment variables starting with ``JAXSIM_JOINT_``. Available variables include:

- ``JAXSIM_JOINT_FRICTION_STATIC``: Overrides the static friction coefficient for all joints.
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Why the decision to put them as env variables?

These values should be dependent on the model. I am not convinced of having the default set via env variables.

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They should be dependent on the model, but instead of modifying the URDF, this allows to override them quickly. The default behavior does not change if the variable is not set


*Default:* ``0.0``.

- ``JAXSIM_JOINT_FRICTION_VISCOUS``: Overrides the viscous friction coefficient for all joints.

*Default:* ``0.0``.

- ``JAXSIM_JOINT_POSITION_LIMIT_DAMPER``: Overrides the damper value for joint position limits of the SDF model.

*Default:* ``0.0``.

- ``JAXSIM_JOINT_POSITION_LIMIT_SPRING``: Overrides the spring value for joint position limits of the SDF model.

*Default:* ``0.0``.

Logging and Exceptions
~~~~~~~~~~~~~~~~~~~~~~
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4 changes: 2 additions & 2 deletions src/jaxsim/parsers/rod/parser.py
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Expand Up @@ -252,14 +252,14 @@ def extract_model_data(
if j.axis is not None
and j.axis.dynamics is not None
and j.axis.dynamics.friction is not None
else 0.0
else os.environ.get("JAXSIM_JOINT_FRICTION_STATIC", 0.0)
),
friction_viscous=float(
j.axis.dynamics.damping
if j.axis is not None
and j.axis.dynamics is not None
and j.axis.dynamics.damping is not None
else 0.0
else os.environ.get("JAXSIM_JOINT_FRICTION_VISCOUS", 0.0)
),
position_limit_damper=float(
j.axis.limit.dissipation
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