ROS2 Parameters

What is ROS2 Parameters?

ROS2 parameters are typed, named configuration values that a ROS2 node exposes at runtime. Other tools can read and modify them without recompiling the node. They are the standard way to expose tunable knobs — PID gains, frame IDs, frequencies, thresholds — to operators and other software.

How It Works

Each node declares parameters with a default value, a type (bool, int, float, string, array), and an optional descriptor (range, read-only). The parameter daemon stores them and exposes them via a service-like API. You can list them with ros2 param list, get them with ros2 param get, and set them with ros2 param set — even while the node is running. Nodes can register callbacks that fire whenever a parameter changes, so runtime retuning is straightforward.

Real-World Example

Every Nav2 navigation parameter — costmap inflation radius, planner tolerance, max velocity — is a ROS2 parameter. Camera drivers expose exposure and gain as parameters. ros2_control hardware drivers expose joint limits and PID gains.

Why It Matters for Robotics

ROS2 parameters separate code from configuration, making robots tunable in production without recompiling. They are a daily tool for every ROS2 engineer. Knowing how to declare, validate, and dynamically update parameters is a baseline interview expectation.

Try It Yourself

Write a simple talker node that publishes a string at a frequency configured via a parameter. Run it, then change the frequency live with ros2 param set /talker pub_rate 5.0 and watch the output rate change.

Quick Quiz

🧠
Quick Quiz
3 questions
1.A ROS2 parameter is best described as:
A.A compiled constant
B.A node's runtime configuration value
C.A topic message
D.A USB cable
2.You change a running parameter with:
A.ros2 topic echo
B.ros2 param set
C.ros2 launch
D.ros2 bag record
3.A great use of parameters is:
A.Streaming high-rate sensor data
B.Tuning PID gains live
C.Sending camera images
D.Running C++ tests

Further Reading

• Ros2
• Ros2 Nodes
• Ros2 Launch
• Ros2 Services

Ask R2 About This

Open the R2 Co-pilot (press ⌘K anywhere on R2BOT) and ask: "Explain ROS2 Parameters for a Class 9 student in India, with one real-world Indian example." You'll get a tailored, sourced answer in seconds.