PTU - 2-DOF pan-tilt unit¶

Kinematic chain¶

base_plate (box 0.14 × 0.14 × 0.025 m)
  └─ pan_joint  [revolute Z  −π … +π]
       pan_link (cylinder r=0.028, l=0.07)
         └─ tilt_joint  [revolute Y  −π/2 … 0]
              tilt_link (box 0.09 × 0.05 × 0.05 m)
                └─ lens_joint  [fixed]
                     lens (sphere r=0.022)

What this example demonstrates¶

All three geometry primitives (Box, Cylinder, Sphere) used together in one robot description
Deeply chained kinematic tree - four links in a single serial chain
JointDynamics (damping + friction) on both revolute joints
Inertial.from_geometry() for every link - no manual inertia calculation
robot.print_tree() - colour-coded ASCII tree output shown below:

Robot: ptu

*  link  base_plate (box)
|
+-- joint pan_joint  [revolute]
|   \-- link  pan_link (cylinder)
|
|       +-- joint tilt_joint  [revolute]
|       |   \-- link  tilt_link (box)
|       |
|       |       \-- joint lens_joint  [fixed]
|       |           \-- link  lens (sphere)

Running the example¶

python3 examples/ptu.py

Output files are written to examples/ptu/:

File	Description
`ptu.urdf`	URDF robot description
`ptu.xacro`	Xacro equivalent
`ptu_tree.txt`	Plain-text kinematic tree

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

Source¶

examples/ptu.py