Base Frame

The coordinate frame rigidly fixed to a robot's base, used as the reference for the arm's position and orientation.

The base frame is a reference frame rigidly fixed to the robot's base; its origin and axis directions are set by the manufacturer, and the ROS convention points x forward, y left, and z up. Unless stated otherwise, an arm controller reports the end-effector's position and orientation relative to this frame — Franka's interface, for instance, stores the end-effector pose as O_T_EE, meaning “the end-effector's pose in base frame O.” In ROS, the corresponding frame is called base_link. The base frame differs from the world frame in one key way: when an arm is mounted on a mobile base or a humanoid body, the base frame moves along with the robot, while the world frame stays fixed in the environment. When recording demonstration data, it's essential to record which frame the actions are expressed in — otherwise the data won't transfer cleanly to a different robot.

ExampleFor a stationary tabletop arm, the command “move the end-effector to (0.5, 0, 0.3) meters in the base frame” means, under the x-forward, z-up convention, 0.5 meters directly in front of the base and 0.3 meters up.

Also called

base_link, Robot Base Frame

Related

World Frame · Coordinate Frame · End-Effector Pose · Coordinate Transformation · TF / tf2 Transform Tree · Body Frame

Sources

ROS REP 105: Coordinate Frames for Mobile Platforms
ROS REP 103: Standard Units of Measure and Coordinate Conventions
libfranka robot_state.h（O_T_EE: end effector pose in base frame）