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docs(examples): flatten and enrich xacro examples with a modular diff-drive robot
- Flattened examples/xacro directory structure by removing redundant subfolders. - Added a comprehensive, modular diff_drive_robot.xacro example. - Fixed material tags in materials.xacro for standard compliance. - Updated examples README with accurate API usage and directory structure. - Verified xacro parsing via URDFParser.parse_xacro. Signed-off-by: arounamounchili <patouossa.mounchili@gmail.com>
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‎examples/README.md‎

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- **urdf/**: Standalone URDF XML models of various robots (mobile bases, quadrupeds).
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- **xacro/**: Modular models using Xacro macros and property evaluation.
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- **macros/**: Reusable kinematic and inertial macros.
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- **imports/**: Shared materials and global properties.
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- `diff_drive_robot.xacro`: Main entry point for a modular mobile robot.
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- `inertials.xacro`: Reusable kinematic and inertial macros.
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- `materials.xacro`: Shared materials and global properties.
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## Usage
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robot = parser.parse("examples/urdf/diff_drive_robot.urdf")
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print(robot.summary())
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```
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### Xacro Support
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LinkForge also supports Xacro files by automatically evaluating macros and properties during parsing:
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```python
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from pathlib import Path
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from linkforge_core.parsers.urdf_parser import URDFParser
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parser = URDFParser()
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# Resolve Xacro then parse into a Robot model
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robot = parser.parse_xacro(Path("examples/xacro/diff_drive_robot.xacro"))
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print(robot.summary())
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```

‎examples/xacro/diff_drive_robot.xacro‎

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<?xml version="1.0"?>
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<robot name="diff_drive_robot" xmlns:xacro="http://www.ros.org/wiki/xacro">
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<!-- Include modular components -->
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<xacro:include filename="materials.xacro" />
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<xacro:include filename="inertials.xacro" />
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<!-- Properties -->
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<xacro:property name="chassis_length" value="0.5" />
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<xacro:property name="chassis_width" value="0.3" />
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<xacro:property name="chassis_height" value="0.15" />
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<xacro:property name="wheel_radius" value="0.1" />
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<xacro:property name="wheel_width" value="0.04" />
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<xacro:property name="wheel_ygap" value="0.01" />
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<xacro:property name="wheel_zoff" value="0.05" />
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<xacro:property name="wheel_xoff" value="0.12" />
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<!-- Base Link -->
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<link name="base_link">
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<visual>
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<geometry>
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<box size="${chassis_length} ${chassis_width} ${chassis_height}"/>
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</geometry>
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<material name="silver"/>
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</visual>
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<collision>
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<geometry>
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<box size="${chassis_length} ${chassis_width} ${chassis_height}"/>
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</geometry>
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</collision>
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<xacro:box_inertia m="15.0" w="${chassis_width}" h="${chassis_height}" d="${chassis_length}"/>
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</link>
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<!-- Wheel Macro -->
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<xacro:macro name="wheel" params="prefix x_reflect y_reflect">
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<link name="${prefix}_link">
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<visual>
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<origin xyz="0 0 0" rpy="${pi/2} 0 0"/>
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<geometry>
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<cylinder radius="${wheel_radius}" length="${wheel_width}"/>
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</geometry>
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<material name="black"/>
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</visual>
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<collision>
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<origin xyz="0 0 0" rpy="${pi/2} 0 0"/>
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<geometry>
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<cylinder radius="${wheel_radius}" length="${wheel_width}"/>
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</geometry>
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</collision>
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<xacro:cylinder_inertia m="0.5" r="${wheel_radius}" h="${wheel_width}"/>
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</link>
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<joint name="${prefix}_joint" type="continuous">
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<parent link="base_link"/>
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<child link="${prefix}_link"/>
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<origin xyz="${x_reflect*wheel_xoff} ${y_reflect*(chassis_width/2+wheel_ygap)} ${-wheel_zoff}" rpy="0 0 0"/>
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<axis xyz="0 1 0"/>
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</joint>
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</xacro:macro>
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<xacro:wheel prefix="drivewhl_l" x_reflect="-1" y_reflect="1" />
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<xacro:wheel prefix="drivewhl_r" x_reflect="-1" y_reflect="-1" />
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<!-- Caster Wheel -->
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<link name="front_caster">
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<visual>
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<geometry>
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<sphere radius="${(wheel_radius+wheel_zoff)/2}"/>
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</geometry>
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<material name="black"/>
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</visual>
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<collision>
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<geometry>
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<sphere radius="${(wheel_radius+wheel_zoff)/2}"/>
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</geometry>
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</collision>
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<inertial>
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<mass value="0.1"/>
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<inertia ixx="0.0001" ixy="0.0" ixz="0.0" iyy="0.0001" iyz="0.0" izz="0.0001"/>
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</inertial>
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</link>
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<joint name="caster_joint" type="fixed">
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<parent link="base_link"/>
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<child link="front_caster"/>
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<origin xyz="${wheel_xoff} 0 ${-(wheel_radius+wheel_zoff)/2}" rpy="0 0 0"/>
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</joint>
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</robot>

examples/xacro/macros/inertials.xacro renamed to examples/xacro/inertials.xacro

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examples/xacro/imports/materials.xacro renamed to examples/xacro/materials.xacro

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<?xml version="1.0"?>
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<robot xmlns:xacro="http://www.ros.org/wiki/xacro">
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<xacro:material name="silver">
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<material name="silver">
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<color rgba="0.75 0.75 0.75 1.0"/>
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</xacro:material>
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</material>
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<xacro:material name="black">
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<material name="black">
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<color rgba="0.0 0.0 0.0 1.0"/>
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</xacro:material>
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</material>
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</robot>

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