Project-2

Project 2: ROS Essentials

Project Overview

In this project two ROS packages have been created inside the catkin_wrc\src. They are drive_bot and the ball_chaser which will be used in Gazebo. The steps to design the robot, hourse it in the world and program it ro chase a white ball is mentioned below:

drive_bot

• Create a my_robot ROS package to hold the robot, the white ball and the world.
• Design a differential drive robot with the Unified Robot Description Format. Add two sensors to your robot: a lidar and a camera. Add Gazebo plugins for your robot’s differential drive, lidar, and camera.
• House the robot inside the world which was built in the Build My World Project.
• Add a white-coloredball to the gazebo world and savea new copy of this in the world.
• the world.launch file should launch your world with the white colored ball and your robot.

ball_chaser

• Create a ball_chaser ROS package to hold your C++ nodes.
• Write a drive_bot C++ node that will provide a ball_chaser/command_robot service to drive the robot by controlling its linear x and angular z velocities. The service should publish to the wheel joints and return back the requested velocities.
• Write a process_image C++ node that reads your robot's camera image, analyzes it to determine the presence and position of a white ball. If a white ball exists in theimage, your node should request a service via a client to drive the robot towards it.
• The ball_chaser.launch should run both the drive_bot and the process_image nodes.

Dependencies

Please make sure the following dependencies are met before running the project:

• Gazebo >= 7.0

• ROS Kinetic

• make >= 4.1(mac,linux) , 3.81 (Windows)

  • Linux: make is installed by default
  • Mac: Install Xcode
  • Windows: Installation Instructions

• gcc/gcc++ >= 5.4

  • Linux: gcc/gcc++ is installed by default
  • Mac: Install X Code
  • Windows: Install MinGW

Setup

• Step 1: Make sure the dependencies are met
• Step 2: Open bash/terminal and clone the project repository
• Step 3: Execute the following line in the command line to update info and upgrade the outdated packages and dependencies on your system.

  sudo apt-get update && sudo apt-get upgrade -y

• Step 4: Build and run the project

Directory Structure

.Project-2
├── ball_chaser                         # ball_chaser package
│   ├── CMakeLists.txt                  # compiler instructions
│   ├── launch                          # launch folder for the launch files
│   │   └── ball_chaser.launch          
│   ├── package.xml                     # package info
│   ├── src                             # source folder for all the C++ scripts
│   │   ├── drive_bot.cpp   
│   │   └── process_image.cpp
│   └── srv                             # service folder for ROS services
│       └── DriveToTarget.srv
└── my_robot
    ├── CMakeLists.txt                  # Compiler instructions
    ├── launch                          # launch folder for the launch files
    │   ├── robot_description.launch
    │   └── world.launch
    ├── meshes                          # meshes folder for hokuyo sensor
    │   └── hokuyo.dae
    ├── package.xml                     # package info
    ├── urdf                            # urdf folder for xacro files
    │   ├── my_robot.gazebo
    │   └── my_robot.xacro
    └── worlds                          # world files
        ├── empty.world
        └── office.world

Running the Project

• Step 1 : Clone the repository

  git clone https://github.com/Ayushman-Choudhuri/Udacity-Robotics-Software-Engineer-Nanodegree

• Step 2 : add the ball_chaser and my_robot to your catkin workspace

• Step 3: Open your catkin_workspace and make

  cd /home/workspace/catkin_ws/
  
  catkin_make

• Step 4: Launch my_robot in Gazebo (both world and plugins):

  source devel/setup.bash 
  
  roslaunch my_robot world.launch

• Step 5: launch ball_chaser and process_image nodes

  cd /home/workspace/catkin_ws/
  
  source devel/setup.bash
  
  roslaunch ball_chaser ball_chaser.launch

• Step 6: Visualize node connections

  cd /home/workspace/catkin_ws/
  
  source devel/setup.bash
  
  rosrun rqt_image_view rqt_image_view