Hobu - Differential-drive mobile robot

Kinematic chain

base_footprint  (virtual root - no geometry)
  └─ base_joint  [fixed]
       base_link (box 0.6 × 0.4 × 0.2 m)
         ├─ base_right_wheel_joint  [continuous Y]
         │    right_wheel_link (cylinder r=0.1, l=0.05)
         ├─ base_left_wheel_joint  [continuous Y]
         │    left_wheel_link  (cylinder r=0.1, l=0.05)
         └─ base_caster_wheel_joint  [fixed]
              caster_wheel_link (sphere r=0.05)

What this example demonstrates

• Origin.wheel() - applies a −π/2 roll so a URDF cylinder’s Z-axis aligns with Y, the standard wheel orientation in ROS

• Per-shape inertia factories (Inertial.from_box, Inertial.from_cylinder, Inertial.from_sphere) with an inertia_multiply safety margin

• Multi-branch kinematic trees - two continuous joints hang off the same parent link

• Virtual root link - base_footprint carries no geometry and serves as the world-fixed anchor (standard ROS convention for mobile bases)

Running the example

python3 examples/hobu.py

Output files are written to examples/hobu/:

File	Description
hobu.urdf	URDF robot description
hobu.xacro	Xacro equivalent
hobu_tree.txt	Plain-text kinematic tree

Quick visualisation: copy hobu.urdf into the online URDF viewer for instant validation and 3D preview without any local ROS install.

Source

examples/hobu.py