urdf-sdf-model

Expert skill for robot model creation and validation in URDF and SDF formats. Generate URDF files with proper link-joint hierarchy, create Xacro macros, calculate inertial properties, configure joint types, and validate models.

Installable skillMITBy a5c-aiUpdated Oct 31, 2026

INTENDED FOROpenClawInstall in a listed agent.

instructions.md

---
name: urdf-sdf-model-710ec877d836
description: Expert skill for robot model creation and validation in URDF and SDF formats. Generate URDF files with proper link-joint hierarchy, create Xacro macros, calculate inertial properties, configure joint types, and validate models.
allowed-tools: Bash(*) Read Write Edit Glob Grep WebFetch
metadata:
  author: babysitter-sdk
  version: "1.0.0"
  category: robot-modeling
  backlog-id: SK-004
graph:
  domains: [domain:robotics]
  specializations: [specialization:robotics-simulation]
  skillAreas: [skill-area:motion-planning, skill-area:sensor-fusion]
  roles: [role:research-engineer]
---

# urdf-sdf-model

You are **urdf-sdf-model** - a specialized skill for robot model creation and validation in URDF (Unified Robot Description Format) and SDF (Simulation Description Format).

## Overview

This skill enables AI-powered robot modeling including:
- Generating URDF files with proper link-joint hierarchy
- Creating Xacro macros for modular robot descriptions
- Converting between URDF and SDF formats
- Calculating and setting inertial properties (mass, inertia tensors)
- Importing and optimizing mesh files (visual and collision)
- Configuring joint types (revolute, prismatic, continuous, fixed, floating)
- Setting up transmission and actuator definitions
- Adding sensor plugins and attachments
- Validating models with urdfdom and check_urdf
- Visualizing and debugging in RViz

## Prerequisites

- ROS/ROS2 with urdf packages
- xacro for macro processing
- urdfdom for validation
- Gazebo for SDF validation
- Mesh tools (MeshLab, Blender) for mesh optimization

## Capabilities

### 1. URDF Generation

Generate URDF files with proper structure:

```xml
<?xml version="1.0"?>
<robot name="my_robot" xmlns:xacro="http://www.ros.org/wiki/xacro">

  <!-- Materials -->
  <material name="blue">
    <color rgba="0.0 0.0 0.8 1.0"/>
  </material>

  <!-- Base Link -->
  <link name="base_link">
    <visual>
      <geometry>
        <box size="0.5 0.3 0.1"/>
      </geometry>
      <material name="blue"/>
    </visual>
    <collision>
      <geometry>
        <box size="0.5 0.3 0.1"/>
      </geometry>
    </collision>
    <inertial>
      <mass value="10.0"/>
      <origin xyz="0 0 0" rpy="0 0 0"/>
      <inertia ixx="0.0833" ixy="0" ixz="0"
               iyy="0.2167" iyz="0" izz="0.2833"/>
    </inertial>
  </link>

  <!-- Wheel Joint -->
  <joint name="wheel_joint" type="continuous">
    <parent link="base_link"/>
    <child link="wheel_link"/>
    <origin xyz="0.2 0.15 -0.05" rpy="-1.5708 0 0"/>
    <axis xyz="0 0 1"/>
    <limit effort="10" velocity="10"/>
    <dynamics damping="0.1" friction="0.1"/>
  </joint>

  <!-- Wheel Link -->
  <link name="wheel_link">
    <visual>
      <geometry>
        <cylinder radius="0.05" length="0.02"/>
      </geometry>
    </visual>
    <collision>
      <geometry>
        <cylinder radius="0.05" length="0.02"/>
      </geometry>
    </collision>
    <inertial>
      <mass value="0.5"/>
      <inertia ixx="0.0003" ixy="0" ixz="0"
               iyy="0.0003" iyz="0" izz="0.0006"/>
    </inertial>
  </link>

</robot>
```

### 2. Xacro Macros

Create modular robot descriptions with Xacro:

```xml
<?xml version="1.0"?>
<robot name="my_robot" xmlns:xacro="http://www.ros.org/wiki/xacro">

  <!-- Properties -->
  <xacro:property name="wheel_radius" value="0.05"/>
  <xacro:property name="wheel_width" value="0.02"/>
  <xacro:property name="wheel_mass" value="0.5"/>

  <!-- Inertia Macros -->
  <xacro:macro name="cylinder_inertia" params="m r h">
    <inertia ixx="${m*(3*r*r+h*h)/12}" ixy="0" ixz="0"
             iyy="${m*(3*r*r+h*h)/12}" iyz="0" izz="${m*r*r/2}"/>
  </xacro:macro>

  <xacro:macro name="box_inertia" params="m x y z">
    <inertia ixx="${m*(y*y+z*z)/12}" ixy="0" ixz="0"
             iyy="${m*(x*x+z*z)/12}" iyz="0" izz="${m*(x*x+y*y)/12}"/>
  </xacro:macro>

  <!-- Wheel Macro -->
  <xacro:macro name="wheel" params="prefix parent x_offset y_offset">
    <joint name="${prefix}_wheel_joint" type="continuous">
      <parent link="${parent}"/>
      <child link="${prefix}_wheel_link"/>
      <origin xyz="${x_offset} ${y_offset} 0" rpy="-1.5708 0 0"/>
      <axis xyz="0 0 1"/>
      <limit effort="10" velocity="10"/>
      <dynamics damping="0.1" friction="0.1"/>
    </joint>

    <link name="${prefix}_wheel_link">
      <visual>
        <geometry>
          <cylinder radius="${wheel_radius}" length="${wheel_width}"/>
        </geometry>
        <material name="black"/>
      </visual>
      <collision>
        <geometry>
          <cylinder radius="${wheel_radius}" length="${wheel_width}"/>
        </geometry>
      </collision>
      <inertial>
        <mass value="${wheel_mass}"/>
        <xacro:cylinder_inertia m="${wheel_mass}" r="${wheel_radius}" h="${wheel_width}"/>
      </inertial>
    </link>

    <!-- Gazebo friction -->
    <gazebo reference="${prefix}_wheel_link">
      <mu1>1.0</mu1>
      <mu2>1.0</mu2>
      <kp>1e6</kp>
      <kd>1.0</kd>
    </gazebo>
  </xacro:macro>

  <!-- Instantiate wheels -->
  <xacro:wheel prefix="front_left" parent="base_link" x_offset="0.15" y_offset="0.12"/>
  <xacro:wheel prefix="front_right" parent="base_link" x_offset="0.15" y_offset="-0.12"/>
  <xacro:wheel prefix="rear_left" parent="base_link" x_offset="-0.15" y_offset="0.12"/>
  <xacro:wheel prefix="rear_right" parent="base_link" x_offset="-0.15" y_offset="-0.12"/>

</robot>
```

### 3. Inertia Calculations

Calculate inertia tensors for common geometries:

```python
import numpy as np

def box_inertia(mass, x, y, z):
    """Calculate inertia tensor for a box centered at origin."""
    ixx = mass * (y**2 + z**2) / 12
    iyy = mass * (x**2 + z**2) / 12
    izz = mass * (x**2 + y**2) / 12
    return {'ixx': ixx, 'iyy': iyy, 'izz': izz, 'ixy': 0, 'ixz': 0, 'iyz': 0}

def cylinder_inertia(mass, radius, height):
    """Calculate inertia tensor for a cylinder along z-axis."""
    ixx = mass * (3 * radius**2 + height**2) / 12
    iyy = mass * (3 * radius**2 + height**2) / 12
    izz = mass * radius**2 / 2
    return {'ixx': ixx, 'iyy': iyy, 'izz': izz, 'ixy': 0, 'ixz': 0, 'iyz': 0}

def sphere_inertia(mass, radius):
    """Calculate inertia tensor for a solid sphere."""
    i = 2 * mass * radius**2 / 5
    return {'ixx': i, 'iyy': i, 'izz': i, 'ixy': 0, 'ixz': 0, 'iyz': 0}

def mesh_inertia_from_stl(stl_file, mass, density=None):
    """Estimate inertia from STL mesh using convex hull approximation."""
    # Use trimesh or similar library for accurate calculation
    import trimesh
    mesh = trimesh.load(stl_file)
    mesh.density = density if density else mass / mesh.volume
    return mesh.moment_inertia
```

### 4. Joint Types Configuration

Configure different joint types:

```xml
<!-- Revolute Joint (limited rotation) -->
<joint name="arm_joint" type="revolute">
  <parent link="base"/>
  <child link="arm"/>
  <origin xyz="0 0 0.1" rpy="0 0 0"/>
  <axis xyz="0 1 0"/>
  <limit lower="-1.57" upper="1.57" effort="100" velocity="1.0"/>
  <dynamics damping="0.5" friction="0.1"/>
</joint>

<!-- Continuous Joint (unlimited rotation) -->
<joint name="wheel_joint" type="continuous">
  <parent link="base"/>
  <child link="wheel"/>
  <axis xyz="0 0 1"/>
  <limit effort="10" velocity="10"/>
</joint>

<!-- Prismatic Joint (linear motion) -->
<joint name="slider_joint" type="prismatic">
  <parent link="base"/>
  <child link="slider"/>
  <origin xyz="0 0 0"/>
  <axis xyz="0 0 1"/>
  <limit lower="0" upper="0.5" effort="50" velocity="0.5"/>
</joint>

<!-- Fixed Joint (no motion) -->
<joint name="sensor_mount" type="fixed">
  <parent link="base"/>
  <child link="sensor"/>
  <origin xyz="0.1 0 0.05" rpy="0 0 0"/>
</joint>
```

### 5. Sensor Attachments

Add sensors to the robot model:

```xml
<!-- Camera Sensor -->
<link name="camera_link">
  <visual>
    <geometry>
      <box size="0.02 0.05 0.02"/>
    </geometry>
  </visual>
</link>

<joint name="camera_joint" type="fixed">
  <parent link="base_link"/>
  <child link="camera_link"/>
  <origin xyz="0.2 0 0.1" rpy="0 0 0"/>
</joint>

<gazebo reference="camera_link">
  <sensor type="camera" name="camera">
    <update_rate>30.0</update_rate>
    <camera>
      <horizontal_fov>1.3962634</horizontal_fov>
      <image>
        <width>640</width>
        <height>480</height>
        <format>R8G8B8</format>
      </image>
      <clip>
        <near>0.02</near>
        <far>100</far>
      </clip>
    </camera>
    <plugin name="camera_plugin" filename="libgazebo_ros_camera.so">
      <ros>
        <namespace>/robot</namespace>
        <remapping>image_raw:=camera/image_raw</remapping>
        <remapping>camera_info:=camera/camera_info</remapping>
      </ros>
      <frame_name>camera_link</frame_name>
    </plugin>
  </sensor>
</gazebo>

<!-- LiDAR Sensor -->
<link name="lidar_link">
  <visual>
    <geometry>
      <cylinder radius="0.03" length="0.04"/>
    </geometry>
  </visual>
</link>

<gazebo reference="lidar_link">
  <sensor type="ray" name="lidar">
    <pose>0 0 0 0 0 0</pose>
    <visualize>true</visualize>
    <update_rate>10</update_rate>
    <ray>
      <scan>
        <horizontal>
          <samples>360</samples>
          <resolution>1</resolution>
          <min_angle>-3.14159</min_angle>
          <max_angle>3.14159</max_angle>
        </horizontal>
      </scan>
      <range>
        <min>0.1</min>
        <max>10.0</max>
        <resolution>0.01</resolution>
      </range>
    </ray>
    <plugin name="lidar_plugin" filename="libgazebo_ros_ray_sensor.so">
      <ros>
        <namespace>/robot</namespace>
        <remapping>~/out:=scan</remapping>
      </ros>
      <output_type>sensor_msgs/LaserScan</output_type>
      <frame_name>lidar_link</frame_name>
    </plugin>
  </sensor>
</gazebo>
```

### 6. Model Validation

Validate URDF models:

```bash
# Check URDF syntax
check_urdf robot.urdf

# Process Xacro and check
xacro robot.urdf.xacro > robot.urdf && check_urdf robot.urdf

# Visualize URDF tree
urdf_to_graphviz robot.urdf

# View in RViz
ros2 launch urdf_tutorial display.launch.py model:=robot.urdf.xacro

# Convert URDF to SDF
gz sdf -p robot.urdf > robot.sdf
```

### 7. SDF Format

Generate SDF for Gazebo:

```xml
<?xml version='1.0'?>
<sdf version='1.7'>
  <model name='my_robot'>
    <link name='base_link'>
      <inertial>
        <mass>10.0</mass>
        <inertia>
          <ixx>0.0833</ixx>
          <iyy>0.2167</iyy>
          <izz>0.2833</izz>
        </inertia>
      </inertial>
      <collision name='base_collision'>
        <geometry>
          <box>
            <size>0.5 0.3 0.1</size>
          </box>
        </geometry>
        <surface>
          <friction>
            <ode>
              <mu>1.0</mu>
              <mu2>1.0</mu2>
            </ode>
          </friction>
        </surface>
      </collision>
      <visual name='base_visual'>
        <geometry>
          <box>
            <size>0.5 0.3 0.1</size>
          </box>
        </geometry>
        <material>
          <ambient>0.0 0.0 0.8 1</ambient>
        </material>
      </visual>
    </link>
  </model>
</sdf>
```

## MCP Server Integration

This skill can leverage the following MCP servers for enhanced capabilities:

| Server | Description | Installation |
|--------|-------------|--------------|
| CAD-Query MCP | Parametric 3D modeling | [mcpservers.org](https://mcpservers.org/servers/rishigundakaram/cadquery-mcp-server) |
| FreeCAD MCP | FreeCAD integration | [GitHub](https://github.com/bonninr/freecad_mcp) |
| Blender MCP | Mesh creation and editing | [blender-mcp.com](https://blender-mcp.com/) |
| OpenSCAD MCP | Parametric modeling | [playbooks.com](https://playbooks.com/mcp/jhacksman-openscad) |

## Best Practices

1. **Consistent units** - Use SI units (meters, kilograms, radians)
2. **Origin placement** - Place link origins at center of mass when possible
3. **Collision geometry** - Use simplified collision meshes for performance
4. **Inertia accuracy** - Calculate accurate inertia for stable simulation
5. **Mesh optimization** - Reduce polygon count for collision meshes
6. **Modular design** - Use Xacro macros for reusable components

## Process Integration

This skill integrates with the following processes:
- `robot-urdf-sdf-model.js` - Primary model creation process
- `robot-system-design.js` - System architecture with models
- `moveit-manipulation-planning.js` - MoveIt configuration
- `gazebo-simulation-setup.js` - Simulation model setup

## Output Format

When executing operations, provide structured output:

```json
{
  "operation": "create-urdf",
  "robotName": "my_robot",
  "status": "success",
  "validation": {
    "syntaxValid": true,
    "inertiasValid": true,
    "jointsValid": true
  },
  "artifacts": [
    "urdf/my_robot.urdf.xacro",
    "meshes/base_link.stl",
    "meshes/wheel.stl"
  ],
  "statistics": {
    "links": 5,
    "joints": 4,
    "sensors": 2
  }
}
```

## Constraints

- Verify coordinate frame conventions (REP-103)
- Ensure consistent units throughout model
- Validate inertia tensors are physically plausible
- Check for self-collision in collision geometry
- Respect Gazebo SDF version compatibility

Install this skill

Download the complete skill package or use the command below.

Your agentYour shell

Run from your active OpenClaw workspace (default: ~/.openclaw/workspace).

mkdir -p "skills" && archive=$(mktemp) && curl -fSL "https://daveai.thedave.site/downloads/urdf-sdf-model-710ec877d836.zip" -o "$archive" && unzip -o "$archive" -d "skills" && rm -f "$archive"

Download skill ZIP

Original SKILL.md, bundled files, source attribution, and license notices. Reload your agent if it does not discover the new skill.

FIELD OF WORKDevelopment & Engineering

LICENSEMIT

ACCESSFree / no account

AgentSkill.sh importml-ai-engineer

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Source & author

Creator / publisher: a5c-ai
Project source: Original project

Upstream repository explicitly recorded in package mirror path

ORIGINAL REPOSITORY

GitHub activity

a5c-ai/babysitter ↗

Stars: 1,889
Forks: 123
Open issues and PRs: 461
Repository size: ~261,102 KB
Default branch: main
Created: Jan 5, 2026
Repository updated: Nov 3, 2026
Last push: Nov 1, 2026
Language: JavaScript
License: MIT

Topics agent-orchestration · agent-skills · agentic-ai · agentic-workflow · ai-agents · ai-automation · babysitter · claude-code · claude-code-skills · claude-code-workflows · claude-skills · claude-workflows

Repository-wide figures from GitHub, checked Nov 3, 2026. Stars are endorsements, not a Dave AI quality rating. Repository size is GitHub’s estimate; a ZIP download may differ.

Classification

Fields of work: Development & Engineering
Roles: Backend Developer ML / AI Engineer
Skill specialties: API
Tools & integrations: Ros
Country applicability: Country not specified
Creator / publisher: a5c-ai

Source catalog labels. Country labels describe applicability, not creator location.

Platform guidance

Imported from the listed AgentSkill.sh category. Complete supplied package files and notices are retained. Required external tools and credentials are not installed. No bundled code was executed during import. Individual agent task behavior has not been tested.

urdf-sdf-model

instructions.md

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