**OPTIONAL**: If you would like to see how the static frames update while the robot is in motion, run the stow command node and observe the tf frames in RViz.
@ -40,7 +40,7 @@ ros2 run stretch_ros_tutorials stow_command
The aim of this example is to provide instruction on how to filter scan messages.
<!-- TODO: Update the links -->
For robots with laser scanners, ROS provides a special Message type in the [sensor_msgs](http://wiki.ros.org/sensor_msgs) package called [LaserScan](http://docs.ros.org/en/api/sensor_msgs/html/msg/LaserScan.html) to hold information about a given scan. Let's take a look at the message specification itself:
For robots with laser scanners, ROS provides a special Message type in the [sensor_msgs](https://github.com/ros2/common_interfaces/tree/galactic/sensor_msgs) package called [LaserScan](https://github.com/ros2/common_interfaces/blob/galactic/sensor_msgs/msg/LaserScan.msg) to hold information about a given scan. Let's take a look at the message specification itself:
```
#
@ -14,7 +13,7 @@ For robots with laser scanners, ROS provides a special Message type in the [sens
# with Stretch's LiDAR having both angle_min and angle_max facing forward
# (very closely along the x-axis) of the device frame
#
Header header
std_msgs/Header header # timestamp data in a particular coordinate frame
float32 angle_min # start angle of the scan [rad]
float32 angle_max # end angle of the scan [rad]
float32 angle_increment # angular distance between measurements [rad]
The above message tells you everything you need to know about a scan. Most importantly, you have the angle of each hit and its distance (range) from the scanner. If you want to work with raw range data, then the above message is all you need. There is also an image below that illustrates the components of the message type.
For a Stretch robot the start angle of the scan, `angle_min`, and
end angle, `angle_max`, are closely located along the x-axis of Stretch's frame. `angle_min` and `angle_max` are set at **-3.1416** and **3.1416**, respectively. This is illustrated by the images below.
@ -155,4 +155,3 @@ Setup Avoider class with `avoider = Avioder()`
Give control to ROS with `rclpy.spin()`. This will allow the callback to be called whenever new messages come in. If we don't put this line in, then the node will not work, and ROS will not process any messages.
Let's bringup stretch in RViz by using the following command.
@ -18,7 +18,7 @@ ros2 run stretch_ros_tutorials marker
```
The gif below demonstrates how to add a new *Marker* display type, and change the topic name from `visualization_marker` to `balloon`. A red sphere Marker should appear above the Stretch robot.
Create a maker. Markers of all shapes share a common type. Set the frame ID and type. The frame ID is the frame in which the position of the marker is specified. The type is the shape of the marker. Further details on marker shapes can be found here: [RViz Markers](http://wiki.ros.org/rviz/DisplayTypes/Marker)
@ -102,8 +102,7 @@ from control_msgs.action import FollowJointTrajectory
from trajectory_msgs.msg import JointTrajectoryPoint
from sensor_msgs.msg import JointState
```
<!-- TODO: Update links below -->
You need to import rclpy if you are writing a ROS 2 Node. Import the FollowJointTrajectory from the [control_msgs.msg](http://wiki.ros.org/control_msgs) package to control the Stretch robot. Import JointTrajectoryPoint from the [trajectory_msgs](http://wiki.ros.org/trajectory_msgs) package to define robot trajectories.
You need to import rclpy if you are writing a ROS 2 Node. Import the FollowJointTrajectory from the [control_msgs.msg](http://wiki.ros.org/control_msgs) package to control the Stretch robot. Import JointTrajectoryPoint from the [trajectory_msgs](https://github.com/ros2/common_interfaces/tree/galactic/trajectory_msgs) package to define robot trajectories.
```python
class StowCommand(Node):
@ -167,7 +166,7 @@ To make the script executable call the main() function like above.
## Installing Ubuntu 20.04 with ROS 2 Galactic on Stretch
Hello Robot utilizes Ubuntu, an open source Linux operating system, for the Stretch RE1 platform. If you are unfamiliar with the operating system, we encourage you to review a [tutorial](https://ubuntu.com/tutorials/command-line-for-beginners#1-overview) provided by Ubuntu. Additionally, the Linux command line, BASH, is used to execute commands and is needed to run ROS on the Stretch robot. Here is a [tutorial](https://ryanstutorials.net/linuxtutorial/) on getting started with BASH.
<!-- TODO: Change the installation instructions link below -->
Instructions on installing Ubuntu 20.04 with ROS Noetic and ROS 2 Galactic can be found in our open source [installation guide](https://github.com/hello-robot/stretch_ros/blob/dev/noetic/install_noetic.md). Following these steps should create a separate Ubuntu 20.04 partition with an ament worskspace created in the home directory.
## ROS 2 Tutorials Setup on Local Computer
Once your system is setup, clone the [stretch_ros_tutorials](https://github.com/hello-sanchez/stretch_ros_tutorials.git) to the src directory of the ament workspace, then build the packages.
Once your system is setup, clone the [stretch_ros_tutorials](https://github.com/hello-sanchez/stretch_ros_tutorials.git) repo to the src directory of the ament workspace, then build the packages.
The graph allows a user to observe and affirm if topics are broadcasted to the correct nodes. This method can also be utilized to debug communication issues.
This will brining up an RViz instance where you can move the robot around using [interactive markers](http://wiki.ros.org/rviz/Tutorials/Interactive%20Markers%3A%20Getting%20Started) and create plans between poses. You can reference the bottom gif as a guide to plan and execute motion.
Additionally, the demo allows a user to select from the five groups, *stretch_arm*, *stretch_gripper*, *stretch_head*, *mobile_base_arm* and *position* to move. The option to change groups in the in *Planning Request* section in the *Displays* tree. A few notes to be kept in mind:
@ -37,7 +37,7 @@ Additionally, the demo allows a user to select from the five groups, *stretch_ar
* When planning with *stretch_head* group make sure you select *Approx IK Solutions* in Planning tab of Motion Planning RViz plugin.
This will launch an Rviz instance that visualizes the joints with markers and an empty world in Gazebo with Stretch and load all the controllers. There are pre-defined positions for each joint group for demonstration purposes. There are three joint groups, namely stretch_arm, stretch_gripper and stretch_head that can be controlled individually via Motion Planning Rviz plugin. Start and goal positions for joints can be selected similar to [this moveit tutorial](https://ros-planning.github.io/moveit_tutorials/doc/quickstart_in_rviz/quickstart_in_rviz_tutorial.html#choosing-specific-start-goal-states).
Rviz will show the robot and the map that is being constructed. With the terminal open, use the instructions printed by the teleop package to teleoperate the robot around the room. Avoid sharp turns and revisit previously visited spots to form loop closures.
If you want to visualize Stretch's [tf transform tree](http://wiki.ros.org/rviz/DisplayTypes/TF), you need to add the display type to the RViz window. First, click on the *Add* button and include the *TF* type to the display. You will then see all of the transform frames of the Stretch robot and the visualization can be toggled off and on by clicking the checkbox next to the tree. Below is a gif for reference.
Stretch comes ready to run out of the box. The Xbox Teleoperation demo will let you quickly test out the robot capabilities by teleoperating it with an Xbox Controller.
Note that the teleop_twist_joy package has a deadman switch by default which disables the drive commands to be published unless pressed. For a Logitech F310 joystick, this button is A.
**Next Tutorial:** [Internal State of Stretch](internal_state_of_stretch.md)
Aaron Edsinger
2 years ago