robot_joint_names) and are always present. The
floating-base fields are optional so a fixed-base robot (an arm, a
bolted-down manipulator) can implement this interface without fabricating
an IMU reading; a consumer that needs one raises a descriptive error when
it is absent rather than reading a placeholder.
Fields
Motor positions (rad), motor order.
Motor velocities (rad/s), motor order.
Base angular velocity (rad/s), length 3;
None on a robot with no floating base or no IMU.Base orientation quaternion (w, x, y, z), length 4, mapping the base frame to a Z-up world frame — the robot driver owns any conversion from its sensor’s native convention;
None on a robot with no floating base or no IMU.Base linear velocity (m/s), length 3;
None unless the robot runs a state estimator that provides one.