🐢 ROS 2 Humble - Turtlesim Guide 🐢

✨ Complete Step-by-Step Tutorial to Install, Use & Control Turtlesim in ROS 2 Humble ✨

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🚀 Step 1: Install Turtlesim Package

sudo apt update
sudo apt install ros-humble-turtlesim

✅ Check Installation:

ros2 pkg executables turtlesim

You should see:

turtlesim draw_square
turtlesim mimic
turtlesim turtle_teleop_key
turtlesim turtlesim_node

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🕹️ Step 2: Launch Turtlesim Simulator

ros2 run turtlesim turtlesim_node

🐢 A window will pop up showing a turtle in the center.

📜 Terminal output will show:

[INFO] [turtlesim]: Starting turtlesim with node name /turtlesim
[INFO] [turtlesim]: Spawning turtle [turtle1] at x=[5.544445], y=[5.544445], theta=[0.000000]

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🎮 Step 3: Control the Turtle

🖥️ Open a new terminal, source ROS 2 again, and run:

ros2 run turtlesim turtle_teleop_key

✅ Controls:

• ⬆️⬇️⬅️➡️ Use your arrow keys to move the turtle.
• 🐢 Each key press moves the turtle a small distance, just like a real robot.

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🔍 Step 4: Explore Nodes, Topics & Services

ros2 node list
ros2 topic list
ros2 service list
ros2 action list

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🛠️ Step 5: Install and Use rqt

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

🖥️ Launch rqt:

rqt

✅ First Time Setup:

• Navigate to Plugins > Services > Service Caller.
• 💡 If plugins don’t appear, run:

rqt --force-discover

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✨ Step 6: Spawn a Second Turtle

🔄 In rqt, refresh the service list.

🛠️ Select the /spawn service and set:

• name: turtle2
• x: 1.0
• y: 1.0

✅ Click Call to spawn turtle2.

⚠️ Note:

If you try to spawn turtle1 again, you’ll see:

[ERROR] [turtlesim]: A turtle named [turtle1] already exists

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🎨 Step 7: Change Pen Color

🎨 In rqt, select the /turtle1/set_pen service and set:

• r: 255 (Red)
• g: 0
• b: 0
• width: 5

✅ Click Call — turtle1 will now draw in red with thicker lines.

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🐢 Step 8: Control Turtle 2 (Remapping)

🕹️ To control turtle2, run this in a new terminal:

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

✅ Now:

• Terminal 1 controls turtle1.
• Terminal 2 controls turtle2.

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❌ Step 9: Close Turtlesim

• Press Ctrl + C in the turtlesim_node terminal.
• Press q in the turtle_teleop_key terminal.

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📚 Summary

✅ Installed turtlesim
✅ Moved the turtle using teleop
✅ Explored nodes, topics & services
✅ Used rqt to spawn and customize turtles
✅ Controlled multiple turtles with remapping

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💬 Final Note

Thanks for following this guide! 🐢 Dive deeper into ROS 2 for building awesome robotic projects!

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