Launching the Complete Robot Simulation in ROS 2
- ROS 2, Tutorials
Up to this point, we have built and tested individual parts of our robot: the URDF description, Gazebo simulation, controllers, and even integration with MoveIt and a remote Alexa interface.
Now it’s time to bring everything together into a single launch file that runs the complete robot simulation with all components working in harmony.
This is a crucial step before deploying the system onto the physical robot, as it allows us to validate the entire software pipeline in a safe and controlled environment.
1. Creating the Bringup Package
First, we create a new ROS 2 package called arduinobot_bringup. This package will serve as the central place to manage launch files for bringing up the robot.
Full Command
ros2 pkg create arduinobot_bringup
Let’s break down the code
ros2 pkg create→ Command to generate a new ROS 2 package.arduinobot_bringup→ The name of the package. By convention, a*_bringuppackage contains launch files and scripts that “bring up” the robot system (start all its components together).
2. Writing the Launch File
Now we create the main launch file: simulated_robot.launch.py. This file will start Gazebo, the controllers, MoveIt, and the remote interface.
Full Code: simulated_robot.launch.py
from launch import LaunchDescription
from launch_ros.actions import Node
from launch.actions import IncludeLaunchDescription
from launch.launch_description_sources import PythonLaunchDescriptionSource
import os
from ament_index_python.packages import get_package_share_directory
def generate_launch_description():
# Get paths to other packages
gazebo_pkg = get_package_share_directory('arduinobot_gazebo')
controller_pkg = get_package_share_directory('arduinobot_controller')
moveit_pkg = get_package_share_directory('arduinobot_moveit')
interface_pkg = get_package_share_directory('arduinobot_remote_interface')
# Include their launch files
gazebo_launch = IncludeLaunchDescription(
PythonLaunchDescriptionSource(
os.path.join(gazebo_pkg, 'launch', 'gazebo.launch.py'))
)
controller_launch = IncludeLaunchDescription(
PythonLaunchDescriptionSource(
os.path.join(controller_pkg, 'launch', 'controller.launch.py'))
)
moveit_launch = IncludeLaunchDescription(
PythonLaunchDescriptionSource(
os.path.join(moveit_pkg, 'launch', 'moveit.launch.py'))
)
interface_launch = IncludeLaunchDescription(
PythonLaunchDescriptionSource(
os.path.join(interface_pkg, 'launch', 'interface.launch.py'))
)
return LaunchDescription([
gazebo_launch,
controller_launch,
moveit_launch,
interface_launch
])
Let’s break down the code
from launch import LaunchDescription
from launch_ros.actions import Node
from launch.actions import IncludeLaunchDescription
from launch.launch_description_sources import PythonLaunchDescriptionSource
import os
from ament_index_python.packages import get_package_share_directory
LaunchDescription→ Defines the set of processes to start.IncludeLaunchDescription→ Lets us include other launch files.PythonLaunchDescriptionSource→ Allows referencing launch files written in Python.get_package_share_directory→ Finds the path to installed packages.
Getting Package Paths
gazebo_pkg = get_package_share_directory('arduinobot_gazebo')
controller_pkg = get_package_share_directory('arduinobot_controller')
moveit_pkg = get_package_share_directory('arduinobot_moveit')
interface_pkg = get_package_share_directory('arduinobot_remote_interface')
Here we locate the package directories for Gazebo, controller, MoveIt, and the remote interface.
Including Launch Files
gazebo_launch = IncludeLaunchDescription(
PythonLaunchDescriptionSource(
os.path.join(gazebo_pkg, 'launch', 'gazebo.launch.py'))
)
We repeat this for each package (controller, moveit, interface). Each line tells ROS 2 to include another launch file.
Final Launch Description
return LaunchDescription([
gazebo_launch,
controller_launch,
moveit_launch,
interface_launch
])
This returns a list of launch actions that ROS 2 executes. Running this file launches all components together.
3. Installing the Launch Directory
To ensure the launch file is installed with the package, we need to update the CMakeLists.txt.
Full Code Addition
install(
DIRECTORY launch
DESTINATION share/${PROJECT_NAME}/
)
Let’s break down the code
install()→ Command in CMake to install files into the workspace.DIRECTORY launch→ Installs everything in thelaunchdirectory.DESTINATION share/${PROJECT_NAME}/→ Puts the files in the package’s share directory so they can be found at runtime.
4. Running the Full Simulation
Now we are ready to run the complete system.
Step 1 — Build the Workspace
colcon build
Step 2 — Source the Workspace
. install/setup.bash
Step 3 — Launch the Simulation
ros2 launch arduinobot_bringup simulated_robot.launch.py
When you run this, Gazebo starts, controllers are loaded, MoveIt is initialized, and the remote interface is ready.
5. Connecting with Alexa via Ngrok
To test voice commands remotely, we need to expose the robot’s web service through ngrok.
Steps:
Start ngrok:
ngrok http 5000
- Copy the new Forwarding URL.
Paste it into your Alexa Developer Console under the endpoint configuration.
Speak a command to Alexa (e.g., “Move the robot arm forward”) and watch it execute in the simulation.
6. Conclusion
We now have a fully integrated robot simulation in ROS 2, complete with Gazebo, controllers, MoveIt, and a remote Alexa interface.
This simulation acts as a sandbox where you can safely test interactions and debug issues before deploying on the physical robot.
The next step is to bring this exact setup to the real robot — and that’s when your robot truly comes alive.
