herb_description

herb_description contains URDF and SRDF descriptions of HERB, a bimanual mobile manipulation robot designed and built by the Personal Robotics Lab in the Robotics Institute at Carnegie Mellon University.

SolidWorks Export

This package contains several URDF files that are directly exported from SolidWorks using the SW2URDF. These files are:

• BHD280_URDF.URDF: BarrettHand model (the BH-280 hardware revision)
• HERB_BASE_URDF.URDF: HERB torso and head
• WAM_URDF.URDF: Barrett WAM model (7-DOF, with wrist and force/torque sensor)

These files should not be edited by hand since they will be overwritten by future SolidWorks exports.

URDF Transformation

The URDF exported from SolidWorks does not correctly specify mass, inertia properties, and joint limits. These properties are patched into the raw URDF exported by SolidWorks using the postprocess_urdf.py script.

Specifically, the following transformations occur at build time:

• BHD280_URDF.URDF + config/bh280_params.urdf.xacro -> bh280_raw.urdf
• HERB_BASE_URDF.URDF + config/herb_params.urdf.xacro -> herb_base_raw.urdf
• WAM_URDF.URDF + config/wam_params.urdf.xacro -> wam_raw.urdf

These output files, with the suffix _raw.urdf, are an intermediate build artifact and should not be used directly. See below if you you want to include a BH-280 or WAM model as part of a larger URDF file.

xacro Transformation

The files generated above are wrapped in thin xacro wrappers using the postprocess_xacro.py script. This script performs several transformations of the input file:

1. Wrap the entire URDF file in a xacro:macro tag with a prefix argument.
2. Prepend prefix onto all link and joint names
3. Repair any incorrect package:// URIs generated by SW2URDF (optional)
4. Assign a default color to all links (optional)
5. Replace the collision geometry with primitives and/or meshes (optional)
6. Replace visual STL files with COLLADA models (optional)

Together, transformations (1) and (2) allow one URDF model exported by SolidWorks to be instantiated more than once in a larger xacro file. This is critical since HERB has two Barrett WAMs and BarrettHand end-effectors. The following transformations occur at build time:

• bh280_raw.urdf -> bh280.urdf.xacro
• herb_base_raw.urdf -> herb_base.urdf.xacro
• wam_raw.urdf -> wam.urdf.xacro.

These output files are placed in the devel space in your Catkin workspace and are intended for re-use. You should use these files when constructing larger models out of these components.

xacro Expansion

Finally, the herb.urdf.xacro file is expanded into herb.urdf by directly invoking xacro. This xacro file specifies the overall HERB description by instantiating the bh280.urdf.xacro, herb_base.urdf.xacro, and wam.urdf.xacro xacro macros generated in the previous build step. Similarly, a herb.srdf SRDF file is generated from the herb.srdf.xacro file You should only include the herb.urdf and herb.srdf files generated in this build step for most applications.

As a convenience, the following two URDF models are also generated:

• bh280_standalone.urdf - standalone BarrettHand
• wam_standalone.urdf - 7-DOF WAM with force/torque sensor and wrist
• wam_bh280_standalone.urdf - model consisting of bh280_standalone.urdf attached to the wrist of wam_standalone.urdf

Notes on Visual Geometry

Getting the COLLADA (i.e. .dae) files to both display properly in RViz andload in OpenRAVE takes some effort. Specifically:

• When generating new meshes, make sure the correct schema (1.4, not 1.5) is used. The second line of the file should read:

<COLLADA xmlns="http://www.collada.org/2005/11/COLLADASchema" version="1.4.0">

• Depending on the software that is exporting the mesh, you must take care to ensure that the resulting file has the <up_axis>Y_UP</up_axis> tag
• All units should be in meters

LICENSE

Unless otherwise noted, herb_description is licensed under a BSD license (see LICENSE.bsd). The COLLADA visual geometry for the Barrett WAM and BarrettHand are licensed under the GPL (see LICENSE.gpl). This includes the following files in the meshes directory:

• all .dae models except for: head_wam1.dae, head_wam2.dae, herb_base.dae, segway_wheel_left.dae, and segway_wheel_right.dae`
• all .jpg textures except for: head_wam1.jpg, head_wam2.jpg, herb_base.jpg, and wheel.jpg

Contributors

PrPy is developed by the Personal Robotics Lab in the Robotics Institute at Carnegie Mellon University.

This is a non-exhaustive list of contributors:

• The URDF and SRDF packaging of HERB was done by Michael Koval
• This model is based on an earlier model built by Mike Vande Weghe
• HERB's torso and head were designed, modeled, and exported by Michael Dawson-Haggerty
• The visual geometry for HERB's torso and head was modeled by Aaron Walsman.
• The Barrett WAM and BarrettHand URDF files were exported by Michael Dawson-Haggerty from the SolidWorks models provided by Barrett Technology, Inc.
• The visual geometry for the Barrett WAM and BarrettHand is copied from models produced by RE2 Inc. as part of the DARPA Autonomous Robotic Manipulation program. This package was available under the GPL license (see above for more information).
• Simplified collision geometry for the entire model is courtesy of Aaron Walsman.