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URDF Management

This tutorial will show you how to access URDFs of Stretch. The URDF (Unified Robot Description Format) is the most popular file format to represent a robot's physical descpriction and geometry. A robot's URDF is used in different applications such as collision checking, navigation planners and perform forward/inverse kinematics.

Stretch URDF

All the Stretch robot model's URDF and meshes are managed by the standalone python package Stretch URDF.

This package can be installed by: 

python3 -m pip install  -U hello-robot-stretch-urdf

The URDF data is uncalibrated and is managed seperately from the Stretch ROS/ROS2 URDF data but could be ported to over using the provided CLI tools.

Accessing URDF Files

The URDF and mesh data is installed as a Python package. It's location can be found as: 

import importlib.resources as importlib_resources
pkg_path = str(importlib_resources.files("stretch_urdf"))

The URDF naming convention is stretch_description_[model_name]_[tool_name].urdf. Example to retrieve a URDF file and mesh files directory: 

model_name = 'SE3' # RE1V0, RE2V0, SE3
tool_name = 'eoa_wrist_dw3_tool_sg3' # eoa_wrist_dw3_tool_sg3, tool_stretch_gripper, etc
urdf_file_path = pkg_path + f"/{model_name}/stretch_description_{model_name}_{tool_name}.urdf"
mesh_files_directory_path = pkg_path + f"/{model_name}/meshes"

Stretch URDF CLI Tools

The package comes with some useful stretch_urdf_* CLI tools for you to take advantage of.

Visualize URDFs

You can use the stretch_urdf_viz.py tool to visualize any robot model with a tool configuration of your choice. You can also pass different arguments while on robot to visualize URDF with stretch body drivers running and visualize realtime robot motions. 

$ stretch_urdf_viz.py -h
For use with S T R E T C H (R) from Hello Robot Inc.
---------------------------------------------------------------------

usage: stretch_urdf_viz.py [-h] [-t] [-c] [-g]

Python based URDF visualization

options:
  -h, --help        show this help message and exit
  -t, --trajectory  Visualize predefined trajectory
  -c, --collision   Use collision meshes
  -g, --gamepad     Use gamepad to control pose
Stretch URDF Viz

Copy URDF and Meshes to ROS

You can use the stretch_urdf_ros_update.py tool to port the right URDF and meshes in to your ROS/ROS2 stretch_description package. 

$ stretch_urdf_ros_update.py -h

For use with S T R E T C H (R) from Hello Robot Inc.
---------------------------------------------------------------------

usage: stretch_urdf_ros_update.py [-h] [-v] [--model {RE1V0,RE2V0,SE3}] [--tool TOOL]
                                  [--ros2_rebuild] [-y]

Tool to update the ROS Stretch Description package Xacros and Mesh files based on the configured
End-of-Arm tool.

options:
  -h, --help            show this help message and exit
  -v, --verbose         Prints more info
  --model {RE1V0,RE2V0,SE3}
                        Choose a Robot model name.
  --tool TOOL           Choose a supported Robot tool name.
  --ros2_rebuild        Rebuild ROS2's Stretch Description package
  -y, --yes             Override Confirmation prompt.