README

Overview

This repository holds ROS 2 Jazzy packages for the Stretch 4 mobile manipulator from Hello Robot Inc. On a fresh robot, these packages are built and available through the ~/ament_ws workspace.

Stretch 4 ROS packages contain breaking changes from Stretch 3 and earlier hardware versions. ROS packages for earlier versions can be found in stretch_ros2.

Packages

Resource	Description
stretch_core	ROS 2 drivers for Stretch 4
stretch_description	Visualize Stretch 4's URDF
stretch_nav2	Navigation stack built on Nav2
stretch_simulation	Simulation of Stretch 4, built on Stretch4 Mujoco
stretch_tag_perception	Detect aruco tags with Stretch 4
stretch_python_bridge	A high-level Python API that abstracts away rclpy
hello_helpers	Miscellaneous helper code used across the stretch_ros2 repository

Licenses

For license details for this repository, see the LICENSE files found in the directories. A summary of the licenses follows:

Directory	License
stretch_core	Apache 2.0
stretch_description	BSD 3-Clause Clear License
stretch_nav2	Apache 2.0
stretch_simulation	Apache 2.0
stretch_tag_perception	Apache 2.0
stretch_python_bridge	Apache 2.0
hello_helpers	Apache 2.0

Common ROS2 commands

Below is an unordered list of common or useful ROS2 commands:

• Start Stretch Driver: ros2 launch stretch_core stretch_driver.launch.py
  • Teleop twist keyboard: ros2 run teleop_twist_keyboard teleop_twist_keyboard
• Start Lidars: ros2 launch stretch_core dual_hesai.launch.py
• Start Cameras: ros2 launch stretch_core luxonis.launch.py use_center:=true use_left:=true use_right:=true for the head cameras and ros2 launch stretch_core gripper_camera.launch.py for the gripper camera.
• Navigation (See https://docs.hello-robot.com/stretch4_docs/working-with-stretch/getting-started/demo-mapping-and-navigation#set-a-navigation-goal):
  • Start Mapping: ros2 launch stretch_nav2 offline_mapping.launch.py and stretch_gamepad_teleop
  • Save a map: ros2 run nav2_map_server map_saver_cli -f ${HELLO_FLEET_PATH}/maps/<map_name>
  • Start nav2: ros2 launch stretch_nav2 navigation_mppi.launch.py map:=${HELLO_FLEET_PATH}/maps/<map_name>.yaml
• Web teleop (See https://docs.hello-robot.com/stretch4_docs/working-with-stretch/getting-started/demo-web-teleoperation): ~/ament_ws/src/stretch4_web_teleop/launch_interface.sh and navigate to https://localhost/operator
• Record rosbags/mcap files: ros2 bag record -a . Note: -a records all the topics, if lidar and cameras are streaming, a few minutes of recording are hundreds of gigabytes large.
  • Play rosbags/mcap files: ros2 bag play ./path/to/recording
• View topics: ros2 topic list and ros2 topic echo /joint_states
• View kinematic links: ros2 run tf2_tools view_frames
  • View transform between two links: ros2 run tf2_ros tf2_echo base_link head_link

Troubleshooting

Zenoh middleware not working

Zenoh should start as a linux user service on Stretch 4. Run systemctl --user status zenoh.service to see if it has failed to start. Run systemctl --user restart zenoh.service to restart it.

If you would like to manually start it, use ros2 run rmw_zenoh_cpp rmw_zenohd.

rviz2 is not launching with a Launch file

There is a known conflict between opencv and rviz2 in ROS2 Jazzy that is documented and a solution is proposed here: #19

Topics are not appearing

There are a number of reasons for topics to not appear.

1. Check that you are running the ros2 node and the client on the same computer. If you are trying to connect from a different computer, you may need to add the following environment variables to your client session:

export RMW_IMPLEMENTATION=rmw_zenoh_cpp
# Replace ROBOT_IP with your Stretch's IP address
ROBOT_IP=192.168.X.XXX
export ZENOH_CONFIG_OVERRIDE='mode="client";connect/endpoints=["tcp/$ROBOT_IP:7447"]'

2. Stretch 4 is configured with export RMW_IMPLEMENTATION=rmw_zenoh_cpp in the .bashrc file to tell ROS2 to use the Zenoh middleware. Make sure your terminal session with this env variable.
3. Use ros2 topic list to list topics. Also, ros2 topic echo /joint_states to listen to a topic
4. Check that the TF tree has all the links: ros2 run tf2_tools view_frames