TurtleBot is a flexible robotic platform designed to work with ROS. Built from common components, TurtleBot is modular and therefore allows the user to create many different configurations. Turtlebot is the ideal platform for experimenting with and learning about ROS. There are many users of the turntable, which means that many functions are freely available on the Internet in the form of ROS nodes. You don't have to write any lines of code to get Turtlebot to automatically navigate the space. All you need to do is find the right nodes on the Internet and get them working.

Most recent and developed version of the turtlebot is version 3. TurtleBot3 is made up of modular plates that users can customize the shape. Available in three types: small size Burger and medium-size Waffle, Waffle Pi. TurtleBot3 consists of a base, two Dynamixel motors, a 1,800mAh battery pack, a 360 degree LIDAR, a camera(+ RealSense camera for Waffle kit, + Raspberry Pi Camera for Waffle Pi kit), an SBC(single board computer: Raspberry PI 3 and Intel Joule 570x) and a hardware mounting kit attaching everything together and adding future sensors. Turtlebot3 was released in May 2017.

The main sensor of the turtlebot is the 360 Laser Distance Sensor LDS-01. The LDS-01 is a 2D laser scanner capable of sensing 360 degrees that collects a set of data around the robot to use for SLAM (Simultaneous Localization and Mapping). The below fidure shows that how a the robot sees the environment from a 360 laser sensor. The blue laser rays are reflected from the objects and the distance is measured and finally a 2D point-cloud of the environment is built.

The 3D camera is one of the most versatile robot sensors. One output of a 3D camera is a 2D camera image, which means that various object recognition algorithms can be used. Many machine vision libraries are available for ROS. One of the most widely used and versatile is OpenCV. In addition, for example, the most up-to-date artificial intelligence library You only look once (YOLO) is available. The same library is used by Iseauto for object recognition.

Objects will be identified and a box will be drawn around them, with the name of the object type identified:

The advantage of a 3D camera over a conventional camera is the depth dimension. This allows the robot to sense the distance between objects. This feature allows the robot to develop autonomous navigation.

To simulate a turtle robot, everything you need to simulate a Gazebos robot is freely available on the Internet.

First of all, you need to install some dependencies. These are based on Ubuntu 18.04 and ROS melodic.

$ sudo apt-get install ros-melodic-joy ros-melodic-teleop-twist-joy \
ros-melodic-teleop-twist-keyboard ros-melodic-laser-proc \
ros-melodic-rgbd-launch ros-melodic-depthimage-to-laserscan \
ros-melodic-rosserial-arduino ros-melodic-rosserial-python \
ros-melodic-rosserial-server ros-melodic-rosserial-client \
ros-melodic-rosserial-msgs ros-melodic-amcl ros-melodic-map-server \
ros-melodic-move-base ros-melodic-urdf ros-melodic-xacro \
ros-melodic-compressed-image-transport ros-melodic-rqt* \
ros-melodic-gmapping ros-melodic-navigation ros-melodic-interactive-markers

Install TurtleBot3 via Debian Packages.

$ sudo apt-get install ros-melodic-turtlebot3-msgs
$ sudo apt-get install ros-melodic-turtlebot3
$ sudo apt-get install ros-melodic-turtlebot3-gazebo

The TurtleBot3 Simulation Package requires turtlebot3 and turtlebot3_msgs packages as prerequisite. Without these prerequisite packages, the Simulation cannot be launched.

$ cd ~/catkin_ws/src/
$ git clone -b melodic-devel https://github.com/ROBOTIS-GIT/turtlebot3_simulations.git
$ cd ~/catkin_ws && catkin_make

Set the default TURTLEBOT3_MODEL name to your model. Enter the below command to a terminal.

In case of TurtleBot3 Burger:

$ echo "export TURTLEBOT3_MODEL=burger" >> ~/.bashrc

The above line write export TURTLEBOT3_MODEL=burger in .bashrc file in your home directory. So whenever you open a new terminal the “burger” is assigned to the TURTLEBOT3_MODEL variable.

There are several predefined environments that you can run the turtle inside them. In the following, you can see an empty, sample and house world.

Empty World:

$ roslaunch turtlebot3_gazebo turtlebot3_empty_world.launch

Sample World:

$ roslaunch turtlebot3_gazebo turtlebot3_world.launch

House:

$ roslaunch turtlebot3_gazebo turtlebot3_house.launch

In the Gazebo Simulator, you can add simulation objects from the menu by clicking on the desired object. You'll also find tools for moving, enlarging and rotating objects in the same place.

Next we try to control the robot remotely.

Download TurtleBot Remote Libraries:

 $ sudo apt-get install ros-kinetic-turtlebot-apps ros-kinetic-turtlebot-rviz-launchers

Let's start the robot control unit:

 $ roslaunch turtlebot_teleop keyboard_teleop.launch

Using the keyboard, we should now see how Turtlebot moves in the simulation.

To avoid having to read sensor values ​​from the command line, we use the visualization tool. It is much easier to understand a robot if we see the same image as the robot. We use ROS's powerful visualization tool called Rviz. Rviz supports visualization of many different sensors. We can turn on and off visualization of different topics. You can also display camera pictures or charts on different panels. It is also possible to add functionality in the form of plugins.

Run TurtleBot Visualization Rviz:

 $ roslaunch turtlebot_rviz_launchers view_robot.launch

Rviz is initially configured to display the 3D Camera Image and Robot Model (URDF). In the bottom left, we also see a two-dimensional camera image.

Clearbot is an educational robot platform for advanced robotics enthusiasts. ClearBot opens up the opportunity to teach and learn complex technologies through simple, hands-on activities. ClearBot software is based on the ROS software framework, which provides the most up-to-date solutions for robot control, mapping, navigation, image processing, simulation, etc.

The ClearBot robot is developed for teaching purposes in cooperation with the University of Tartu Institute of Technology.

Omnidirectional wheels are wheels which are covered with rollers perpendicular to the wheel shaft, thus allowing the wheel to move in a transverse direction in addition to the normal direction of rotation. Omnidirectional wheels give the robot excellent maneuverability and flexible two-dimensional movement.