Fix URDF importer dropping joint friction values - #1
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Joint friction parsed from <dynamics friction='...'> was stored in the joint data dict but never forwarded to add_joint_revolute(), add_joint_prismatic(), or the JointDofConfig for planar (D6) joints. This adds the friction= parameter to all three joint creation paths and includes tests verifying friction values round-trip through URDF import.
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Description
Joint friction values from
<dynamics friction="...">in URDF files are correctly parsed and stored in the joint data dictionary, but never forwarded toadd_joint_revolute(),add_joint_prismatic(), or theJointDofConfigfor planar (D6) joints. All imported joints silently get zero friction regardless of their URDF specification.Changes
joint_friction = joint["friction"]alongsidejoint_dampingfriction=joint_frictiontoadd_joint_revolute()andadd_joint_prismatic()friction=joint_frictionto bothJointDofConfiginstances for planar joints[Unreleased] > FixedTests
test_joint_friction_parsed_from_urdf: verifies friction values (0.25 revolute, 0.75 prismatic) round-trip through URDF importtest_joint_friction_defaults_to_zero: verifies joints without<dynamics friction>default to 0.0Impact
Any URDF robot with non-zero joint friction (common for realistic manipulators) was simulating with zero friction on all joints. This fix is backward-compatible — joints without friction specifications continue to default to 0.0.