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stretch_description

Overview

stretch_description provides materials for a URDF kinematic model of the Stretch RE1 mobile manipulator from Hello Robot Inc.

Details

The meshes directory contains STL mesh files representing the exterior geometry of various parts of the robot.

The urdf directory contains xacro files representing various parts of the robot that are used to generate the robot's URDF.

stretch_ros expects a URDF with the name stretch.urdf to reside within the urdf directory. The file stretch.urdf serves as the URDF for the robot and must be generated. Typically, it is a calibrated urdf file for the particular Stretch RE1 robot being used. To generate this file, please read the documentation within stretch_ros/stretch_calibration.

The xacro_to_urdf.sh will usually only be indirectly run as part of various scripts and launch files within stretch_ros/stretch_calibration.

Sometimes a stretch_uncalibrated.urdf file will reside with the urdf directory. This file is typically generated directly from the xacro files without any alterations.

Exporting a URDF

Sometimes a URDF is useful outside of ROS, such as for simulations and analysis. Running the export_urdf.sh script in the urdf directory will export a full URDF model of the robot based on stretch.urdf.

The exported URDF will be found within an exported_urdf directory. It is also copied to a directory for your specific robot found under ~/stretch_user. The exported URDF includes meshes and controller calibration YAML files. The exported URDF can be visualized using stretch_urdf_show.py, which is part of the stretch_body Python code.

Changing the Tool

If you wish to remove the default gripper and add a different tool, you will typically edit /stretch_description/urdf/stretch_description.xacro. Specifically, you will replace the following line in order to include the xacro for the new tool and then follow directions within stretch_ros/stretch_calibration to generate a new calibrated urdf file (stretch.urdf) that includes the new tool.

<xacro:include filename="stretch_gripper.xacro" />

As an example we provide the xacro stretch_dry_erase_marker.xacro and its dependent mesh files with stretch_ros.

Some of the tools found in the Stretch Body Tool Share include URDF data. To integrate these tools into the URDF for your Stretch

>>$ cd ~/repos
>>$ git clone https://github.com/hello-robot/stretch_tool_share
>>$ cd stretch_tool_share/<tool name>
>>$ cp stretch_description/urdf/* ~/catkin_ws/src/stretch_ros/stretch_description/urdf/
>>$ cp stretch_description/meshes/* ~/catkin_ws/src/stretch_ros/stretch_description/meshes/

Next add the xacro for the particular tool to /stretch_description/urdf/stretch_description.xacro. Then you can generate and preview the uncalibrated URDF:

>>$ cd ~/catkin_ws/src/stretch_ros/stretch_description/urdf
>>$ cp stretch.urdf stretch.urdf.bak
>>$ rosrun stretch_calibration update_urdf_after_xacro_change.sh

Now visualize the new tool

>>$ roslaunch stretch_calibration simple_test_head_calibration.launch

License and Patents

Patents are pending that cover aspects of the Stretch RE1 mobile manipulator.

For license information, please see the LICENSE files.