Giters

Avi241 / ROS_Workshop_2

Geek Repo:Geek Repo

Github PK Tool:Github PK Tool

ROS (Robot Operating System) Basic Workshop Tutorial

Introduction

Welcome to the basic ROS workshop! This tutorial is designed to introduce you to the fundamental concepts of ROS, along with practical hands-on exercises using the Turtlesim package. By the end of this workshop, you will have a basic understanding of ROS architecture, its commands, and how to control a simulated turtle in Turtlesim.

Prerequisites

  • Basic knowledge of Linux commands
  • Ubuntu (preferably 18.04 or 20.04)
  • ROS melodic installed on your machine

Workshop Outline

  1. Introduction to ROS
  2. ROS Concepts
    • ROS Master
    • ROS Nodes
    • ROS Topics
    • ROS Services
    • ROS Actions
  3. Basic ROS Commands
  4. Working with Turtlesim
  5. Conclusion

1. Introduction to ROS

What is ROS?

ROS (Robot Operating System) is an open-source, flexible framework for writing robot software. It provides tools, libraries, and conventions to simplify the task of creating complex and robust robot behavior across a wide variety of robotic platforms.

2. ROS Concepts

ROS Master

The ROS Master provides naming and registration services to the rest of the ROS system. It enables nodes to locate each other and manage communications.

ROS Nodes

Nodes are the basic processes that perform computation in ROS. Each node is designed to execute a specific task, and nodes can communicate with each other to build a complete robotic system.

ROS Topics

Topics are named buses over which nodes exchange messages. A node can publish messages to a topic, and other nodes can subscribe to that topic to receive those messages. This communication method is asynchronous.

ROS Services

Services in ROS provide a synchronous communication mechanism between nodes. A service consists of a request and a response. A node can call a service to request a specific action, and the service will respond once the action is complete.

ROS Actions

Actions in ROS are designed for tasks that take an extended period and can be preempted. They provide a way to send goals to a server, receive feedback during execution, and get a result when the task is completed. Actions are particularly useful for long-running or continuous tasks.

3. Basic ROS Commands

Setting Up ROS Environment

source /opt/ros/melodic/setup.bash

Creating a ROS Workspace

  1. Create a directory for your workspace:

    mkdir -p ~/ros_workspace/src

  2. Initialize the workspace:

    cd ~/ros_workspace/src
catkin_init_workspace

  3. Build the workspace:

    cd ~/ros_workspace
catkin_make

  4. Source the workspace:

    source devel/setup.bash

Basic ROS Commands

  • Starting ROS Master: roscore
  • Creating a New Package: catkin_create_pkg <package_name> std_msgs rospy roscpp
  • Listing ROS Nodes: rosnode list
  • Displaying Node Information: rosnode info /node_name
  • Listing ROS Topics: rostopic list
  • Displaying Topic Information: rostopic info /topic_name
  • Publishing to a Topic: rostopic pub /topic_name std_msgs/String "data: 'Hello, ROS!'"
  • Subscribing to a Topic: rostopic echo /topic_name
  • Running a ROS Node: rosrun <package_name> <node_name>

4. Working with Turtlesim

Installing Turtlesim

sudo apt-get install ros-melodic-turtlesim

Launching Turtlesim

  1. Open a terminal and start the ROS Master:

    roscore

  2. In a new terminal, launch Turtlesim:

    rosrun turtlesim turtlesim_node

  3. In another terminal, open the Turtlesim Teleop Key:

    rosrun turtlesim turtle_teleop_key

Demonstrating ROS Concepts with Turtlesim

ROS Nodes

  • List nodes:

    rosnode list

    This will show you the nodes that are currently running, including /rosout and /turtlesim.

  • Node information:

    rosnode info /turtlesim

    This command provides information about the /turtlesim node, such as the topics it publishes and subscribes to.

ROS Topics

  • List topics:

    rostopic list

    This will display all the active topics, including /turtle1/cmd_vel and /turtle1/pose.

  • Topic information:

    rostopic info /turtle1/pose

    This command shows details about the /turtle1/pose topic, including the type of messages and the nodes publishing and subscribing to it.

  • Echo topic:

    rostopic echo /turtle1/pose

    This command prints messages being published to the /turtle1/pose topic, showing the turtle's position in real-time.

ROS Services

  • List services:

    rosservice list

    This lists all available services, such as /clear and /spawn.

  • Service information:

    rosservice info /spawn

    This provides information about the /spawn service.

  • Call service:

    rosservice call /spawn 2 2 0.2 "turtle2"

    This spawns a new turtle at the specified coordinates with the name "turtle2".

ROS Actions

  • List actions: There are no default actions with Turtlesim, but you can explore actions with other ROS packages that support actions, such as the navigation stack.
  • Action information: To understand actions, you typically need a package that defines action servers and clients. Actions involve more complex interactions than services, suitable for tasks that provide feedback and can be preempted.

Writing a Simple ROS Node for Turtlesim

  1. Create a new package: Follow the instructions to create a package and set up your workspace.

  2. Create a Python script: Write a script to move the turtle in a pattern using the geometry_msgs/Twist message type.

  3. Run the script: Execute the script using rosrun and observe the turtle's movements in the Turtlesim window.

Conclusion

Congratulations! You have completed the basic ROS workshop. You now have a foundational understanding of ROS concepts, commands, and how to work with the Turtlesim package. Additionally, you have learned about ROS services, actions, and the role of the ROS Master in managing communications. Keep exploring ROS to build more complex and exciting robotic applications.

Happy coding!

TurtleBot3 Simulation Workshop Tutorial

Introduction

Welcome to the TurtleBot3 simulation workshop! This tutorial will guide you through setting up and using TurtleBot3 in a simulated environment using RViz and Gazebo. You will learn how to perform basic movements, SLAM (Simultaneous Localization and Mapping), save maps, and navigate autonomously.

Prerequisites

  • Basic knowledge of Linux commands
  • Ubuntu (preferably 18.04 or 20.04)
  • ROS melodic installed on your machine
  • TurtleBot3 packages installed

Workshop Outline

  1. Introduction to TurtleBot3
  2. Basic Setup
  3. RViz Simulation
  4. Gazebo Simulation
    • Empty World
    • Predefined World
    • Teleoperation
  5. SLAM
  6. Map Saving
  7. Autonomous Navigation

1. Introduction to TurtleBot3

What is TurtleBot3?

TurtleBot3 is a low-cost, personal robot kit with open-source software. It is designed to support education, research, and product prototyping.

2. Basic Setup

Installing TurtleBot3 Packages

  1. Install TurtleBot3 packages:

    sudo apt-get update
sudo apt-get install ros-melodic-turtlebot3 ros-melodic-turtlebot3-simulations

  2. Set the TurtleBot3 model environment variable:

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

3. RViz Simulation

Launching TurtleBot3 in RViz

  1. Open a terminal and start the ROS Master:

    roscore

  2. In a new terminal, launch the TurtleBot3 simulation in RViz:

    roslaunch turtlebot3_fake turtlebot3_fake.launch

  3. RViz will start, showing the TurtleBot3 model. You can use RViz to visualize different sensor data and robot states.

4. Gazebo Simulation

Launching TurtleBot3 in an Empty World

  1. Open a terminal and launch Gazebo with an empty world: 
    roslaunch turtlebot3_gazebo turtlebot3_empty_world.launch

Launching TurtleBot3 in a Predefined World

  1. Open a terminal and launch Gazebo with a predefined world: 
    roslaunch turtlebot3_gazebo turtlebot3_world.launch

Teleoperation in Gazebo

  1. Open a terminal and run the teleop node to control TurtleBot3: 
    roslaunch turtlebot3_teleop turtlebot3_teleop_key.launch
  2. Use the keyboard to move the robot around the simulation.

5. SLAM (Simultaneous Localization and Mapping)

Running SLAM with TurtleBot3

  1. Open a terminal and launch the TurtleBot3 in a Gazebo world:

    roslaunch turtlebot3_gazebo turtlebot3_world.launch

  2. In a new terminal, start the SLAM node:

    roslaunch turtlebot3_slam turtlebot3_slam.launch slam_methods:=gmapping

  3. In another terminal, run the teleop node to control the robot and explore the environment:

    roslaunch turtlebot3_teleop turtlebot3_teleop_key.launch

  4. Move the robot around to create a map in RViz.

6. Map Saving

Saving the Map

  1. Once you are satisfied with the map created, save it using the following command in a new terminal:

    rosrun map_server map_saver -f ~/map

  2. This will save the map as map.pgm and map.yaml in your home directory.

7. Autonomous Navigation

Running Autonomous Navigation

  1. Launch the TurtleBot3 in a Gazebo world:

    roslaunch turtlebot3_gazebo turtlebot3_world.launch

  2. Launch the navigation stack with your saved map:

    roslaunch turtlebot3_navigation turtlebot3_navigation.launch map_file:=$HOME/map.yaml

  3. Use RViz to set an initial pose estimate:

    • Click on the "2D Pose Estimate" button and click on the map to set the initial pose.

  4. Use RViz to set a goal for autonomous navigation:

    • Click on the "2D Nav Goal" button and click on the map to set the target destination.

Conclusion

Congratulations! You have completed the TurtleBot3 simulation workshop. You now have a foundational understanding of simulating TurtleBot3 using RViz and Gazebo, performing SLAM, saving maps, and navigating autonomously. Keep exploring and building upon these skills to create more advanced robotic applications.

Happy coding!

About