ros2_maze-solver_setup

A custom ros2 maze solver package using turtlebbot3 model and a custom maze.

1. Pre-setup requirements

• Ubuntu 22.04 LTS
• ROS2 humble
• git
• python3.10 or plus

2. Check setup requirements

• checking your ros distribution :

echo $ROS_DISTRO

It should output humble.

• checking your gazebo version (we need gazebo classic 11):

gazebo --version

It should output version 11.xx.x.

• check python3 version :

python3 --version

It should output version 3.10.xx.

• check git version :

git --version

It should output version 2.34.xx.

Note : in case git or gazebo is not installed on your system, run the following commands.

sudo apt install ros-humble-gazebo-*
sudo apt install git

3. Create a ros2 workspace & source it in your .bashrc file :

cd ~
mkdir -p ros2_ws/src
cd ros2_ws
colcon build
echo "source ~/ros2_ws/install/setup.bash" >> ~/.bashrc
source ~/.bashrc

Now you will see build, log & devel folders inside your ros2_ws directory.

4. Create a custom ros2 python type package name maze_solver :

cd ~/ros2_ws/src
ros2 pkg create --build-type ament_python maze_solver --dependencies rclpy
cd ..
colcon build
source ~/.bashrc

This will create setup.cfg, setup.py, src/, package.xml, test/, resource/, maze_solver/ files & folders.

5. Add models and worlds folder in your maze_solver package :

• Copy the models folder from this git repo to the ros2_ws/src/maze_solver directory.
• Copy the worlds folder from this git repo to the ros2_ws/src/maze_solver directory.
• Also copy the content inside models folder & paste it to /.gazebo/models folder.

Note : You could also give your maze_solver/models path to your GAZEBO_MODEL_PATH environment variable, but let's do it wihout adding models folder to GAZEBO_MODEL_PATH explicitly.

6. Now modify your maze_solver/setup.py file with this code :

from setuptools import find_packages, setup
import os
from glob import glob

package_name = 'maze_solver'

setup(
    name=package_name,
    version='0.0.0',
    packages=find_packages(),
    data_files=[
        ('share/ament_index/resource_index/packages',
            ['resource/' + package_name]),
        ('share/' + package_name, ['package.xml']),
        (os.path.join('share', package_name, 'worlds'), glob('worlds/*.world')),
    ],
    install_requires=['setuptools'],
    zip_safe=True,
    maintainer='mohit',
    maintainer_email='mkgautam31102002@gmail.com',
    description='TODO: Package description',
    license='Apache-2.0',
    tests_require=['pytest'],
    entry_points={
        'console_scripts': [
            'launch_maze_world = maze_solver.launch_maze_world:main',
        ],
    },
)

As your saw, we explicitly added our worlds folder in package environment. And also we defined executable script/node named launch_maze_world that will be present in ros2_ws/src/maze_solver/maze_solver directory. It is basically a python node that have a main function which will be called while executing that node with the alias launch_maze_world. This node will spawn the empty world with our maze model inside it.
So we have to create that python node.

7. Create a python launch node to launch empty world with maze :

cd ~/ros2_ws/src/maze_solver/maze_solver
touch launch_maze_world.py
chmod +x launch_maze_world.py

Now open this launch_maze_world.py file & paste the below code into it

#!/usr/bin/env python3

import os
from ament_index_python.packages import get_package_share_directory
from launch import LaunchDescription
from launch.actions import ExecuteProcess
from launch_ros.actions import Node
from launch import LaunchService

def generate_launch_description():
    # Path to the maze_world.world file
    pkg_share = get_package_share_directory('maze_solver')
    world_file = os.path.join(pkg_share, 'worlds', 'empty_world.world')

    return LaunchDescription([
        # Launch Gazebo with the specified world file
        ExecuteProcess(
            cmd=['gazebo', '--verbose', world_file, '-s', 'libgazebo_ros_factory.so'],
            output='screen'
        ),
    ])

def main():
    ld = generate_launch_description()
    ls = LaunchService()
    ls.include_launch_description(ld)
    return ls.run()

if __name__ == '__main__':
    main()

8. Build and run the package node :

cd ~/ros2_ws
colcon build
source ~/.bashrc
ros2 run maze_solver launch_maze_world

It should open the gazebo empty world with a maze inside it. If you could follow up until this step, then go to the next step.
Now the next task is to spawn the turtlebot3 model into this world. For that, we have to install turtlebot3, turtlbot3_msgs, turtlebot3_simulations packages with the humble-devel branch from ROBOTIS-GIT account. Try to do it yourself, use internet resources, understand the code.