Composition of all assignments | Ozodjon Kunishev

1. Turtlesim and RQT installation

sudo apt update
sudo apt install ros-humble-turtlesim

ros2 pkg executables turtlesim

ros2 run turtlesim turtlesim_node

Output:

[INFO] [turtlesim]: Starting turtlesim with node name /turtlesim

[INFO] [turtlesim]: Spawning turtle [turtle1] at x=[5.544445], y=[5.544445], theta=[0.000000]

ros2 run turtlesim turtle_teleop_key

1.2 Install RQT

sudo apt update
sudo apt install ~nros-humble-rqt*

rqt

ros2 run turtlesim turtle_teleop_key --ros-args --remap turtle1/cmd_vel:=turtle2/cmd_vel

2. Writing a simple publisher and subscriber

ros2 pkg create --build-type ament_python py_pubsub

wget https://raw.githubusercontent.com/ros2/examples/humble/rclpy/topics/minimal_publisher/examples_rclpy_minimal_publisher/publisher_member_function.py

Some changes are made to the created files, then:

wget https://raw.githubusercontent.com/ros2/examples/humble/rclpy/topics/minimal_subscriber/examples_rclpy_minimal_subscriber/subscriber_member_function.py

rosdep install -i --from-path src --rosdistro humble -y

. install/setup.bash

ros2 run py_pubsub talker

ros2 run py_pubsub listener

3. Writing a simple service and client

Relevant files are opened and adjusted according to the official website. Some new files will also be created. Then:

rosdep install -i --from-path src --rosdistro humble -y

colcon build --packages-select py_srvcli

In a new terminal:

. install/setup.bash

ros2 run py_srvcli service

In the third terminal:

ros2 run py_srvcli client 2 3

Output:

4. Creating custom msg and srv files

ros2 pkg create --build-type ament_cmake tutorial_interfaces

mkdir msg
mkdir srv

Several files will be created and edited. Then:

colcon build --packages-select tutorial_interfaces

In a new terminal:

. install/setup.bash

ros2 interface show tutorial_interfaces/msg/Num

ros2 interface show tutorial_interfaces/msg/Sphere

ros2 interface show tutorial_interfaces/srv/AddThreeInts

After that changes are made to the publisher and subscriber files. After all the changes:

colcon build --packages-select cpp_pubsub

Two new terminals will be opened and sourced. Then:

ros2 run py_pubsub talker

ros2 run py_pubsub listener

5. Action server and client

This includes creating two python files for action.:

gedit fibonacci_action_server.py

gedit fibonacci_action_client.py

After making changes, we run them using python3 in separate terminals:

python3 fibonacci_action_server.py

python3 fibonacci_action_client.py

6. Composing multiple nodes in a single process

ros2 component types

ros2 run rclcpp_components component_container

ros2 component list

ros2 component load /ComponentManager composition composition::Talker

ros2 component load /ComponentManager composition composition::Listener

ros2 component load /ComponentManager composition composition::Server
ros2 component load /ComponentManager composition composition::Client

ros2 run composition manual_composition

ros2 component unload /ComponentManager 1 2

ros2 run rclcpp_components component_container --ros-args -r __node:=MyContainer -r __ns:=/ns

ros2 component load /ComponentManager composition composition::Talker --node-name talker2

ros2 component load /ComponentManager composition composition::Talker --node-namespace /ns

ros2 component load /ComponentManager composition composition::Talker --node-name talker3 --node-namespace /ns2

ros2 component load /ComponentManager image_tools image_tools::Cam2Image -p burger_mode:=true

ros2 component load /ComponentManager composition composition::Talker -e use_intra_process_comms:=true

7. Launch

7.1 Creating a launch file

mkdir launch

Creating new files will be included in this task.

cd launch
ros2 launch turtlesim_mimic_launch.py

ros2 topic pub -r 1 /turtlesim1/turtle1/cmd_vel geometry_msgs/msg/Twist "{linear: {x: 2.0, y: 0.0, z: 0.0}, angular: {x: 0.0, y: 0.0, z: -1.8}}"

rqt_graph

7.2 Integrating launch files into ROS 2 packages

mkdir -p launch_ws/src
cd launch_ws/src

ros2 pkg create py_launch_example --build-type ament_python

Several changes are made to the auto-created files inside the package

colcon build

ros2 launch py_launch_example my_script_launch.py

7.3 Using substitutions

ros2 pkg create launch_tutorial --build-type ament_python

mkdir launch_tutorial/launch

After creating new files and making changes to some of the existing ones:

colcon build

ros2 launch launch_tutorial example_main.launch.py

ros2 launch launch_tutorial example_substitutions.launch.py --show-args

ros2 launch launch_tutorial example_substitutions.launch.py turtlesim_ns:='turtlesim3' use_provided_red:='True' new_background_r:=200

8. Introducing tf2

sudo apt-get install ros-humble-turtle-tf2-py ros-humble-tf2-tools ros-humble-tf-transformations

ros2 launch turtle_tf2_py turtle_tf2_demo.launch.py

ros2 run turtlesim turtle_teleop_key

ros2 run tf2_tools view_frames

ros2 run tf2_ros tf2_echo [reference_frame] [target_frame]

ros2 run tf2_ros tf2_echo turtle2 turtle1