A ros 2 simulated robot(ROS 2)

Fisrt step in building the differential-drive robot:

In the src directory of your workspace , make a folder called "robot" and clone the repo in it.

  cd src

  mkdir robot 

  cd robot 

  git clone https://github.com/Daviesss/Ros-2-simulated-robot..git

If you build the workspace and you see some errors pop up .You should upgrade pytest to a version that is 6.2 or higher. Use the following command

  pip install --upgrade pytest

Then build the workspace again:

  colcon build

Launch the Node:

  ros2 launch <name_of_package> robot.launch.py

The joint state publisher node must be launched/be active when launching the robot in rviz2.

  ros2 run joint_state_publisher_gui joint_state_publisher_gui

Open Rviz2:

  ros2 run rviz2 rviz2

Set the fixed frame to "base_link".

The centre of the robot which is the "base_link".

Plugins used in simulation of the robot can be gotten from: https://classic.gazebosim.org/tutorials?tut=ros_gzplugins

STEPS TO TAKE TO GET THE ROBOT UP AND READY:

1. Launch the robot_state_publisher in simulation mode.
2. Launch Gazebo.
3. Spawn the robot into Gazebo.

Set the sim time to true,we dealing with simulation.So our the boolean has to be true.

   ros2 launch robot show.robot.launch.py use_sim_time:=true

Start up Gazebo empty world:

   ros2 launch gazebo_ros gazebo.launch.py 

 To spawn the robot into gazebo, launch the file called show.robot.launch.py (Note: launch files in ROS 2 are python scripts/files)

Command:

  ros2 launch robot show.robot.launch.py

Check if the topics are available.This list all topics which are available:

  ros2 topic list

Now,we can drive the robot around once we use the teleop_twist_keyboard node to publish to the "/cmd_vel" topic that the robot subscribes to.

  ros2 run teleop_twist_keyboard  teleop_twist_keyboard

You can give colour to the robot,by adding colour to the .xacro file.Video decription below,while using the teleop_twist_keyboard to drive the robot.

We can also write a python script that publish certain velocity to make the robot move and also perform some basic task. Create a ROS 2 package called drive_robot ,its dependecies on rclpy,the package should be created in the src directory of your workspace.

  cd src

  ros2 pkg create drive_robot --build-type ament_python --dependencies rclpy

Run the node in the pasckage to make the robot drive forward, in linear of x.

  ros2 run drive_robot velocity_drive

   ros2 launch robot show.robot.launch.py world:='path to where you saved your Gazebo world'

You can check the TF2 TREE:

  ros2 run rqt_tf_tree rqt_tf_tree

   ros2 launch robot show.robot.launch.py world:="path to the .world file"

Mine is:

  ros2 launch robot show.robot.launch.py world:=/home/magnum/simuate_ws/src/robot/worlds/new.world

Run the slam_toolbox node.

  ros2 launch robot online_async.launch.py 

Localization:

   ros2 launch robot localization.launch.py map:=/home/magnum/simuate_ws/src/robot/maps/offline.yaml  use_sim_time:=true

But if you want to use the localization mode (AMCL) you have to specify the path in which your map.yaml file is located and pass it into map:=""

• ros2 launch robot localization.launch.py map:="" use_sim_time:=true

Navigation Mode(NAV2 stack)

   ros2 launch  robot nav.launch.py use_sim_time:=true map_subscribe_transient_local:true