Optimal Path Finder

Overview

This project implements search-based algorithms that always yield an optimal path if one exists. Path finding algorithms, such as breadth-first search (BFS), Dijkstra, and A*, have been used find an optimal path for the robot from the user-defined start to end point. The project also generates animation to visualize the exploration of each of the mentioned search-based methods. It first checks that the user inputs do not lie in the obstacle space. Note that the obstacle space is pre-defined and static.

Figure 1 - Node exploration for a rigid robot using A*

The project has been improved from its previous release. The exploration time from one corner of the obstacle space to the other has been reduced to just less than a second from several minutes. Upon running, exploration and animation time are printed on the execution window.

Note that the implementation in this repository assumes the robot to be holonomic. I have used the A* implementation from this projects as a base to find path for a non-holonomic robot in the following projects: A-star Robot and A-star Turtlebot.

Dependencies

• Python3
• Python3-tk
• Python3 Libraries: Numpy, OpenCV-Python

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

Run

• Using the terminal, clone this repository and go into the project directory, and run the main program:

git clone https://github.com/urastogi885/optimal-path-finder
cd optimal-path-finder

• If you have a compressed version of the project, extract it, go into project directory, open the terminal, and run the robot explorer.

python3 robot_explorer.py <start_x,start_y> <goal_x,goal_y> <robot_radius> <clearance> <method> <animation>

• You can use the following one-letter acronyms to specify the method:
  • b - For Breadth-First Search (BFS)
  • d - For Dijkstra
  • a - For A*
• An example for using BFS for a point robot:

python3 robot_explorer.py 5,5 295,195 0 0 b 1

Figure 2 - Exploration + Path using BFS using above start and goal points

python3 robot_explorer.py <start_x,start_y> <goal_x,goal_y> <robot_radius> <clearance> <method> <animation>
python3 robot_explorer.py 5,5 295,195 0 0 d 1

• Radius and clearance for a point robot should be set as 0
• Animation parameter is to display exploration and path. Use 1 to show animation.

Figure 3 - Exploration for point robot using Djikstra's algorithm

• To run the rigid robot version, after execution of the previous command or open a new terminal from the project folder:

python3 robot_explorer.py <start_x,start_y> <goal_x,goal_y> <robot_radius> <clearance> <method> <animation>
python3 robot_explorer.py 5,5 295,195 1 1 d 1

Figure 4 - Final path for rigid robot

• A* algorithm has also been implemented in the project and can be run by using a as the method parameter instead of d

python3 robot_explorer.py <start_x,start_y> <goal_x,goal_y> <robot_radius> <clearance> <method> <animation>
python3 robot_explorer.py 5,5 295,195 1 1 a 1

Figure 5 - Final path for rigid robot using A*

Notes

• Both the explorers, point and rigid, take first 2 arguments as the start and goal points. The x,y values for each point are separated by a comma. DO NOT INCLUDE ANY SPACE AFTER THE COMMAS
• There should a space after each argument.
• The rigid explorer takes 2 extra arguments: robot radius and clearance. Please refer the format using the instance provided in the Run section.
• The explorer first finds a path from the start to the goal, then starts displaying the exploration of the map, and the final path.
• The map for the rigid robot is generated such that shows the extended obstacles due to the robot radius and clearance.