ROS 2 Lyrical lab 06 · 75 min

Launch and parameters

Start a repeatable robot system and load reviewed limits from YAML.

Before you start

At least two working nodes
A package with launch and config directories

Files you will touch

src/robot_bringup/launch/system.launch.py
src/robot_bringup/config/limits.yaml

Step 1

Set up

status_node:
  ros__parameters:
    max_speed: 0.25
    publish_rate: 10.0

Step 2

Create the file

from launch import LaunchDescription
from launch_ros.actions import Node

def generate_launch_description():
    return LaunchDescription([
        Node(package='robot_basics', executable='status_node',
             parameters=['config/limits.yaml'], output='screen')
    ])

Step 3

Build, run and inspect

ros2 launch robot_bringup system.launch.py
ros2 param get /status_node max_speed
ros2 param set /status_node max_speed 0.2

Proof that it works

The launch file starts every declared node
max_speed loads as 0.25
Runtime changes are accepted only inside the node's declared safe range

Recovery notes

Install launch and config directories from CMakeLists.txt.
Declare every parameter before reading it and validate safety-critical changes in an on-set callback.

ROS 2 launch tutorials