|Title:||Coordinate Frames for Humanoid Robots|
|Author:||Thomas Moulard <thomas.moulard at gmail.com>|
|Post-History:||11-Jan-2012, 18-Jan-2012, 08-Feb-2012|
This REP specifies naming conventions and semantic meaning for coordinate frames of humanoid robots used within ROS.
Developers of packages aimed at humanoid robots need a shared convention for coordinate frames in order to better integrate and re-use software components.
The REP 105  already defines frames for mobile bases. This REP both remains compatible with REP 105  and extends it to label other important locations on a humanoid robot such as the gaze (head), left and right wrists, hands and feet.
The base_footprint is the representation of the robot position on the floor. The floor is usually the level where the supporting leg rests, i.e. z = min(l_sole_z, r_sole_z) where l_sole_z and r_sole_z are the left and right sole height respecitvely. The translation component of the frame should be the barycenter of the feet projections on the floor. With respect to the odom frame, the roll and pitch angles should be zero and the yaw angle should correspond to the base_link yaw angle.
Rationale: base_footprint provides a fairly stable 2D planar representation of the humanoid even while walking and swaying with the base_link.
The coordinate frame called l_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 r_wrist defines the equivalent frame for the right arm.
The coordinate frame called l_gripper 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 going "toward" the object. Y the main dimension in which the grasping device moves and Z orthogonal to X and Y axes.
The coordinate frame called r_gripper defines the equivalent frame for the right arm.
The coordinate frame called l_ankle defines the position and orientation of the left leg regardless of the support body geometry.
The coordinate frame called r_ankle defines the equivalent frame for the right leg.
The coordinate frame called l_sole defines the position and orientation of the left leg support body. The (X,Y) plane of this frame must be coplanar with the support body contact surface. It is recommended to choose the origin as the projection of the support body origin on the contact surface. The Z coordinate of this frame should be on the ground level when standing.
The coordinate frame called r_sole defines the equivalent frame for the right leg.
The coordinate frame called l_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 r_toe defines the equivalent frame for the right leg.
The coordinate frame called gaze defines the head position and orientation. The orientation indicates in which direction the head appears to be looking regardless of any sensors (camera for instance).
The coordinate frame called torso is attached to the lowest body of the model which is a parent of l_gripper, r_gripper and gaze.
See REP 105  for map and odom frames definition.
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.
This REP depends on and is compliant with REP 103  and REP 105 .
|||REP 103, Standard Units of Measure and Coordinate Conventions (http://www.ros.org/reps/rep-0103.html)|
|||REP 105, Coordinate Frames for Mobile Platforms (http://www.ros.org/reps/rep-0105.html)|
This document has been placed in the public domain.