urdf2mjcf

Convert URDF (Unified Robot Description Format) files to MJCF (MuJoCo XML Format) for simulation in MuJoCo and MJX. Handles meshes, joints, actuators, and collision geometries.

```bash

# CLI conversion

urdf2mjcf robot.urdf --output robot.mjcf

# With options

urdf2mjcf robot.urdf \

--output robot.mjcf \

--mesh-dir ./meshes \

--add-actuators \

--collision-margin 0.001

```

```python

from urdf2mjcf import convert

# Programmatic conversion

mjcf_xml = convert(

urdf_path="robot.urdf",

mesh_dir="./meshes",

add_actuators=True,

collision_margin=0.001,

)

# Save to file

with open("robot.mjcf", "w") as f:

f.write(mjcf_xml)

```

• Mesh Handling: Converts STL/OBJ meshes, scales appropriately
• Joint Mapping: URDF revolute/prismatic → MJCF hinge/slide
• Actuator Generation: Auto-generates position/velocity actuators
• Collision Geometry: Convex decomposition, margin adjustment
• Inertia Cleanup: Fixes common URDF inertia issues

```

┌─────────────┐ ┌─────────────┐ ┌─────────────┐

│ URDF File │───▶│ urdf2mjcf │───▶│ MJCF File │

│ (ROS/SDF) │ │ Converter │ │ (MuJoCo) │

└─────────────┘ └─────────────┘ └─────────────┘

│ │ │

▼ ▼ ▼

Meshes STL Link transforms Physics props

Joint limits Mass/inertia Actuator defs

Visual geom Collision geom Sensor defs

```

```

urdf2mjcf (-1) ⊗ kos-firmware (+1) ⊗ mujoco-scenes (0) = 0 ✓

```

• ksim-rl (-1): Uses converted MJCF for training
• kos-firmware (+1): Robot firmware
• mujoco-scenes (0): Scene composition
• kbot-humanoid (-1): K-Bot robot model

```bibtex

@misc{urdf2mjcf2024,

title={URDF to MJCF Converter},

author={K-Scale Labs},

year={2024},

url={https://github.com/kscalelabs/urdf2mjcf}

}

```

This skill connects to Software Design for Flexibility (Hanson & Sussman, 2021):

Primary Chapter: 7. Propagators

Concepts: propagator, cell, constraint, bidirectional, TMS

GF(3) Balanced Triad

```

urdf2mjcf (+) + SDF.Ch7 (○) + [balancer] (−) = 0

```

Skill Trit: 1 (PLUS - generation)

Connection Pattern

Propagators flow constraints bidirectionally. This skill propagates information.