Keyboard teleoperation (teleop_twist_keyboard) in ROS - Mini Project: Build & Apply

Keyboard Teleoperation with teleop_twist_keyboard in ROS

📖 Scenario: You want to control a robot remotely using your keyboard. ROS provides a handy tool called teleop_twist_keyboard that lets you send movement commands by pressing keys.In this project, you will set up the necessary ROS nodes and configurations to teleoperate a robot using your keyboard.

🎯 Goal: Build a simple ROS setup that uses teleop_twist_keyboard to send velocity commands to a robot. You will create the ROS launch file and configure the keyboard teleoperation node.

📋 What You'll Learn

Create a ROS launch file named teleop_launch.launch with the correct node configuration

Set a parameter for the robot's velocity scale

Include the teleop_twist_keyboard node with the right topic remapping

Add a final tag to close the launch file properly

💡 Why This Matters

🌍 Real World

Keyboard teleoperation is commonly used in robotics labs and field tests to manually control robots for testing and demonstration.

💼 Career

Understanding how to configure and run teleoperation nodes in ROS is essential for robotics engineers working on robot control and navigation.

1

Create the ROS launch file skeleton

Create a file named teleop_launch.launch and write the XML declaration line <?xml version="1.0"?> followed by the opening <launch> tag.

ROS

Hint

Every ROS launch file starts with an XML declaration and an opening <launch> tag.

2

Add a parameter for velocity scaling

Inside the <launch> tag, add a <param> tag with name="scale_linear" and value="0.5" to set the linear velocity scale.

ROS

Hint

Use a <param> tag to set parameters inside launch files.

3

Add the teleop_twist_keyboard node with topic remapping

Add a <node> tag inside <launch> with pkg="teleop_twist_keyboard", type="teleop_twist_keyboard.py", name="teleop_twist_keyboard", and remap the cmd_vel topic to /robot/cmd_vel using <remap from="cmd_vel" to="/robot/cmd_vel" />.

ROS

Hint

The <node> tag runs a ROS node. Use <remap> to change topic names.

4

Close the launch file

Add the closing </launch> tag at the end of the file to complete the launch file structure.

ROS

Hint

Every XML file must have matching opening and closing tags.

Practice

1. What is the main purpose of the teleop_twist_keyboard node in ROS?

easy

A. To control a robot using keyboard keys

B. To visualize robot sensor data

C. To simulate robot movements automatically

D. To compile ROS packages

Solution

1. Step 1: Understand the node's function

   The teleop_twist_keyboard node allows manual control of a robot using keyboard inputs.

2. Step 2: Compare options with the node's purpose

   Only To control a robot using keyboard keys describes controlling a robot with keyboard keys, which matches the node's purpose.

3. Final Answer:

   To control a robot using keyboard keys -> Option A

4. Quick Check:

   Keyboard control = A [OK]

Hint: Remember: teleop means tele-operation via keyboard [OK]

Common Mistakes:

• Confusing teleop with simulation or visualization
• Thinking it compiles code
• Assuming it runs robot automatically

2. Which command correctly runs the teleop_twist_keyboard node in ROS 2?

easy

A. ros run teleop_twist_keyboard teleop_twist_keyboard

B. ros2 launch teleop_twist_keyboard teleop_twist_keyboard.launch

C. ros2 run teleop_twist_keyboard teleop_twist_keyboard

D. ros2 start teleop_twist_keyboard

Solution

1. Step 1: Identify the correct ROS 2 run syntax

   In ROS 2, the command to run a node is ros2 run <package> <executable>.

2. Step 2: Match the command to teleop_twist_keyboard

   ros2 run teleop_twist_keyboard teleop_twist_keyboard uses the correct syntax and package/executable names.

3. Final Answer:

   ros2 run teleop_twist_keyboard teleop_twist_keyboard -> Option C

4. Quick Check:

   ros2 run + package + executable = B [OK]

Hint: Use 'ros2 run' for running nodes in ROS 2 [OK]

Common Mistakes:

• Using 'ros' instead of 'ros2'
• Using 'launch' instead of 'run' for this node
• Typing 'start' which is not a ROS command

3. Given the following keys pressed in teleop_twist_keyboard: i, j, k, what is the expected robot movement sequence?

medium

A. Turn left, move forward, stop

B. Move backward, turn right, stop

C. Stop, move forward, turn right

D. Move forward, turn left, move backward

Solution

1. Step 1: Recall key functions in teleop_twist_keyboard

   Key 'i' moves robot forward, 'j' turns left, 'k' moves backward.

2. Step 2: Match keys to movements in sequence

   Pressing 'i' then 'j' then 'k' results in moving forward, turning left, then moving backward.

3. Final Answer:

   Move forward, turn left, move backward -> Option D

4. Quick Check:

   i = forward, j = left, k = backward [OK]

Hint: Remember i=forward, j=left, k=backward keys [OK]

Common Mistakes:

• Mixing up 'j' and 'l' keys for turning
• Assuming 'k' stops movement
• Confusing forward and backward keys

4. You run ros2 run teleop_twist_keyboard teleop_twist_keyboard but pressing keys does not move the robot. What is the most likely cause?

medium

A. The robot is not connected or not receiving velocity commands

B. The keyboard keys are incorrect; use arrow keys instead

C. The teleop_twist_keyboard node must be launched with a launch file

D. ROS 2 is not installed properly

Solution

1. Step 1: Check common reasons for no robot movement

   If keys are pressed but robot doesn't move, often the robot is not connected or not subscribed to velocity commands.

2. Step 2: Evaluate other options

   Keyboard keys are correct as per documentation; launch file is not required; ROS 2 installation issues would prevent node running.

3. Final Answer:

   The robot is not connected or not receiving velocity commands -> Option A

4. Quick Check:

   No movement = no connection [OK]

Hint: Check robot connection before blaming keys or launch files [OK]

Common Mistakes:

• Assuming arrow keys must be used
• Thinking launch file is mandatory
• Blaming ROS 2 install without checking connection

5. You want to increase the robot's forward speed using teleop_twist_keyboard. Which method correctly achieves this?

hard

A. Press 'i' key twice quickly to double speed

B. Press 'w' key to increase speed while running teleop_twist_keyboard

C. Restart teleop_twist_keyboard with a higher speed parameter

D. Edit the robot's URDF file to increase max speed

Solution

1. Step 1: Understand teleop_twist_keyboard speed control

   The node allows speed adjustment during runtime using 'w' and 'x' keys to increase or decrease linear speed.

2. Step 2: Evaluate other options

   Editing URDF changes robot model, not teleop speed; restarting with parameters is possible but less direct; pressing 'i' twice does not increase speed.

3. Final Answer:

   Press 'w' key to increase speed while running teleop_twist_keyboard -> Option B

4. Quick Check:

   Use 'w' to increase speed live [OK]

Hint: Use 'w' and 'x' keys to adjust speed live [OK]

Common Mistakes:

• Trying to speed up by pressing movement keys repeatedly
• Editing URDF for speed instead of teleop parameters
• Restarting node instead of adjusting speed live