REP: 118 Title: Coordinate Frames for Humanoids Robots Version: $Revision: 1 $ Last-Modified: $Date: 2012-01-11 11:53:00 +0200 (Wed, 11 Jan 2012) $ Author: Thomas Moulard Status: Draft Type: Informational Content-Type: text/x-rst Requires: 103, 105 Created: 25-Nov-2011 Post-History: Abstract ======== This REP specifies naming conventions and semantic meaning for coordinate frames of humanoids robots used within ROS. Motivation ========== Developers of packages aimed at humanoids robots need a shared convention for coordinate frames in order to better integrate and re-use software components. The REP 105 [2] already defines frames for mobile bases. This REP both remains compatible with REP 105 [2] and extends it to label other important locations on a humanoid robot such as the gaze (head), left and right wrists, hands and feet. Specification ============= Coordinate Frames ----------------- base_link ''''''''' The coordinate frame called ``base_link`` is rigidly attached to the robot root body. It is recommended to choose the robot waist as its root body. The ``base_link`` can be attached to the root in any arbitrary position or orientation; for every hardware platform there will be a different place on the base that provides an obvious point of reference. Note that REP 103 [1] specifies a preferred orientation for frames. base_footprint '''''''''''''' The coordinate frame called ``base_footprint`` projects the ``base_link`` position on the floor. left_wrist and right_wrist '''''''''''''''''''''''''' The coordinate frame called ``left_wrist`` defines the position and orientation of the left arm regardless of the tool (grasping device for instance) attached to it. The coordinate frame called ``right_wrist`` defines the equivalent frame for the right arm. left_hand and right_hand '''''''''''''''''''''''' The coordinate frame called ``left_hand`` defines the position and orientation of the left arm end effector. If the end effector is a grasping device, the frame should be located at the recommended object grasping location. The frame orientation is defined as X the axis which should be collinear with the object axis during the grasping process, Y the axis going "toward" the reached object and Z the axis orthogonal to the (X,Y) plan. The coordinate frame called ``right_wrist`` defines the equivalent frame for the right arm. left_ankle and right_ankle '''''''''''''''''''''''''' The coordinate frame called ``left_ankle`` defines the position and orientation of the left leg regardless of the support body geometry. The coordinate frame called ``right_ankle`` defines the equivalent frame for the right leg. left_sole and right_sole '''''''''''''''''''''''' The coordinate frame called ``left_sole`` defines the position and orientation of the left leg support body. The (X,Y) plan of this frame must be coplanar with the support body contact surface. It is recommended to choose the origin as the projection of the body center on the contact surface. The coordinate frame called ``right_sole`` defines the equivalent frame for the right leg. left_toe and right_toe '''''''''''''''''''''' The coordinate frame called ``left_toe`` defines the position and orientation of the left leg toe body. The (X,Y) plan of this frame must be coplanar with the toe body contact surface. It is recommended to choose the origin as the projection of the body center on the contact surface. The coordinate frame called ``right_toe`` defines the equivalent frame for the right leg. gaze '''' The coordinate frame called ``gaze`` defines the head position and orientation regardless of any sensors (camera for instance). chest ''''' The coordinate frame called ``chest`` is attached to the lowest body of the model which is a parent of ``left_hand``, ``right_hand`` and ``gaze``. map and odom '''''''''''' See REP 105 [1] for ``map`` and ``odom`` frames definition. Frame Hierarchy --------------- ``base_link`` <-- ``chest`` <-- ``gaze`` ``base_link`` <-- ``chest`` <-- ``left_wrist`` <-- ``left_hand`` ``base_link`` <-- ``chest`` <-- ``right_wrist`` <-- ``right_hand`` ``base_link`` <-- ``left_ankle`` <-- ``left_sole`` <-- ``left_toe`` ``base_link`` <-- ``right_ankle`` <-- ``right_sole`` <-- ``right_toe`` Frame Authorities ----------------- Unlike mobile bases, the transformation from ``base_link`` to ``base_footprint`` is not rigid on humanoid robots and is broadcasted by an external node. Exceptions ---------- The scope of potential robotics software is too broad to require all ROS software to follow the guidelines of this REP. However, choosing different conventions should be well justified and well documented. Compliance ========== This REP depends on and is compliant with REP 103 [1] and REP 105 [2]. References ========== .. [1] REP 103, Standard Units of Measure and Coordinate Conventions (http://www.ros.org/reps/rep-0103.html) .. [2] REP 105, Coordinate Frames for Mobile Platforms (http://www.ros.org/reps/rep-0105.html) Copyright ========= This document has been placed in the public domain.