URDF

Links and joints describe the robot#

The ROS 2 URDF documentation introduces the format as a description of robot geometry and organization. Links represent body components, and joints specify their relationships and permitted relative movement.

A humanoid model can describe a torso connected to arm and leg links. The movable-model tutorial explains joint types and limits used to make such a model articulate.

Visual appearance and physical geometry differ#

A visual mesh specifies appearance. Collision geometry specifies shapes for collision checking. The physical-properties tutorial treats these separately and adds mass, centre of mass, and inertia for simulation.

Simpler collision shapes can reduce computation, while accurate inertial values matter when dynamics enter the task.

A description does not control the hardware#

Loading a valid URDF does not make a physical robot move or establish that its simulated behaviour matches reality. Controllers, live joint states, actuator interfaces, and appropriate simulator integration are separate parts of the system. A visually correct model can still have incorrect joint axes, limits, collision shapes, or inertial parameters.