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Overview

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

Quick View

roslaunch stretch_description display.launch

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 unique to the particular Stretch 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.

roscd stretch_description/urdf
./export_urdf.sh

The exported URDF will be in your "stretch_user" directory at the following path: ~/stretch_user/$HELLO_FLEET_ID/exported_urdf. The exported URDF includes meshes and controller calibration YAML files. The exported URDF can be visualized using stretch_robot_urdf_visualizer.py, which is part of the stretch_body Python code.

Changing the Tool

If you want to generate a new URDF for Stretch (e.g. after attaching a new tool to Stretch), you can:

  1. Edit the stretch_description.xacro file in the Stretch Description package.

    Include the tool you want in the stretch_description.xacro. By default, it will include stretch_gripper.xacro. Simply comment out the old <xacro:include ... lines and paste in new ones for your tool. Example code for the other supported tools can be found by looking at the files matching stretch_description_<tool-name>.xacro. To add your own custom tool, copy your xacro/mesh files into the urdf/meshes folders in the Stretch Description package.

  2. In a terminal run

    roscore

  3. Next, in a different terminal terminal run

    rosrun stretch_calibration update_urdf_after_xacro_change.sh

This will create a calibrated URDF called stretch.urdf using the most recent calibration parameters. You can now visualize the new URDF with Rviz.

License and Patents

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

For license information, please see the LICENSE files.