a-star-turtlebot

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a-star-turtlebot

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Implementation of A* pathfinding algorithm on a differential-drive robot

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# A-Star Turtlebot
[![Build Status](https://travis-ci.org/urastogi885/a-star-turtlebot.svg?branch=master)](https://travis-ci.org/urastogi885/a-star-turtlebot)
[![License](https://img.shields.io/badge/License-MIT-blue.svg)](https://github.com/urastogi885/a-star-turtlebot/blob/master/LICENSE)

## Overview
In this project, a-star algorithm is simulated on a differential drive (non-holonomic) mobile robot in a defined static 
world. We are using Turtlebot in ROS-Gazebo for the simulation. The project generates a text file containing linear and 
angular velocities needed by the robot to reach its goal position. A ROS node publishes these velocities at regular 
intervals to simulate Turtlebot's movement in Gazebo. A sample of the simulation from one end of the map to the other 
is shown below.

<img src="https://github.com/urastogi885/a-star-turtlebot/blob/master/images/phase4.gif">
 Figure 1 - Turtlebot-3 Burger moving in known world using velocities provided by A* planner

The project has been developed over 4 phases:
- Phase-1: Installation of ROS and V-REP
- Phase-2: Implementation of A* on a non-holonomic robot
- Phase-3: Implementation of A* on a differential-drive robot
- Phase-4: Implementation of A* on Turtlebot using ROS

Phases 1 and 2 have been implemented on another [repository](https://github.com/urastogi885/a-star-robot). A sample output
for phase-3 of the project can be found [here](https://github.com/urastogi885/a-star-turtlebot#phase3-output)

Also, this project benefitted from my learnings while working on the [Optimal Path Finder](https://github.com/urastogi885/optimal-path-finder) 
project that implements path-finding algorithms such as Breadth-First Search (BFS), Dijkstra, and A* in a 2D-grid environment.

## Authors

- [Umang Rastogi](https://github.com/urastogi885)
- [Naman Gupta](https://github.com/namangupta98)

## Todo

- Add path smoothing

## Dependencies

- Ubuntu 16.04/18.04
- ROS Kinetic/Melodic
- Gazebo
- Turtlebot3 Packages
- Python Packages: Numpy, OpenCV-Python, Math, Queue

## Install Dependencies

- Install Python3, Python3-tk, and the necessary libraries: (if not already installed)

```
sudo apt install python3 python3-tk
sudo apt install python3-pip
pip3 install numpy opencv-python
```

- Check if your system successfully installed all the dependencies
- Open terminal using Ctrl+Alt+T and enter python3.
- The terminal should now present a new area represented by >>> to enter python commands
- Now use the following commands to check libraries: (Exit python window using Ctrl+Z if an error pops up while running 
the below commands)

```
import tkinter
import numpy
import cv2
import math
import queue
```

- If you want to work on Ubuntu 16.04, you will need to install [ROS Kinetic](http://wiki.ros.org/kinetic/Installation/Ubuntu)
by following the instructions given on referenced web-page.
- If you want to work on Ubuntu 18.04, you will need to install [ROS Melodic](http://wiki.ros.org/melodic/Installation/Ubuntu)
by following the instructions given on referenced web-page.
- We recommend installing the full-desktop version of ROS because it automatically installs the latest compatible version of
Gazebo on your system.
- If you wish to install Gazebo separately, then follow the instruction on the [Gazebo install page](http://gazebosim.org/tutorials?tut=install_ubuntu&cat=install).
- Install Turtlebot-3 package and its dependencies:
```
cd ~/<ROS_Workspace>/src
git clone https://github.com/ROBOTIS-GIT/turtlebot3.git
git clone https://github.com/ROBOTIS-GIT/turtlebot3_msgs.git
git clone https://github.com/ROBOTIS-GIT/turtlebot3_simulations.git
cd ../ && catkin_make
sudo su
cp -r src/turtlebot3/ /opt/ros/<distro>/share/
cp -r src/turtlebot3_msgs/ /opt/ros/<distro>/share/
cp -r src/turtlebot3_simulations/ /opt/ros/<distro>/share/
```
- Using the same terminal window, check installation of turtlebot3:
```
source devel/setup.bash
roslaunch turtlebot3_gazebo turtlebot3_world.launch
```
- Note that Turtlebot-3 package is supported by ROS Melodic as well as Kinetic.

## Phase3 Output

In phase-3, a video output was generated to show the exploration and final path a differential-drive robot might take 
using the OpenCV library. The output for one case is presented below.

<img src="https://github.com/urastogi885/a-star-turtlebot/blob/master/images/phase3.gif">
 Figure 2 - Exploration of a differential-drive robot using A* to find optimal path from start to goal 

 
## Run Instructions

- Clone the repository in your ROS workspace. Type
```
cd ~/<ROS_Workspace>/src
git clone https://github.com/urastogi885/a-star-turtlebot
```

- If you have a compressed version of the project, extract it, go into project directory, open the terminal, and type:

```
python3 a_star_turtlebot.py start_x,start_y,start_orientation goal_x,goal_y rpm1,rpm2,clearance animation
python3 a_star_turtlebot.py -4,-4.5,0 4.25,2.75 30,25,5 0
```

- This would generate a text file that will be used to run the Turtlebot-3 in Gazebo.
- Note the following to try the code with other inputs:
    - The origin of the map is taken at the center of the map s make sure to take into consideration in which 
    quadrant your points lie.
    - Provide start and goal coordinates in meters while start orientation is to be provided in degrees.
    - In addition to that, clearance is taken in centimeters.
    - Refer documentation of [*a_star_turtlebot.py*](https://github.com/urastogi885/a-star-turtlebot/blob/master/a_star_turtlebot.py) to
    understand further about input arguments.
    - Set animation to 1 to generate an exploration output as shown in [Phase3 Output](https://github.com/urastogi885/a-star-turtlebot#phase3-output).
    Note that this drastically increases exploration time. 
- Launch the world, spawn turtlebot, navigate it to the desired goal point. Type:

```
cd ~/<ROS_Workspace>
source devel/setup.bash
catkin_make or catkin build (For ROS Melodic, you might have to use catkin build instead of catkin_make)
roslaunch a-star-turtlebot launcher_1.launch
```

- Stop the execution, using ```Ctrl + C```. Do not close this terminal.
- Open *planner.py* from the scripts folder, replace *commander_1.txt* by *commander_2.txt* in the main section of the file.
- Essentially, the following line needs to be changed in *planner.py*:
```
with open(ros_root.get_path('a-star-turtlebot') + '/output_files/commander_1.txt', 'r') as command:
```

- From the same terminal, run:
```
roslaunch a-star-turtlebot launcher_2.launch
```

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