1. Maze Solver Robot Using Wall-Following Algorithm
By: Ali Ulku & Vardah Muhammad
Supervized By: Dr. Mehmet Keskinoz
24.05.2015

2. Outline

3. Outline
• Introduction
− Lego Mindstorm Construction Pack
− Completed View
− Wall-Following Algorithm
− Different Types of Circuits
• Algorithm
− Pseudo Code
− Initialization Block
− 1st If Block
− 2nd If Block
− Move Forward Block
− Turn Right/Left Block
− Medium Motor Turn Right/Left Block
− Logic
• Result
− Robot in the Maze
− Escape Route on Matlab

4. Introduction

5. 5
Introduction
Lego Mindstorm Construction Pack
Main Hardware:
• EV3 Brick (300 MHz ARM9 Controller)
• 2 Large Motors
• 1 Medium Motor
• Infrared Sensor
• Subassemblies
Comments

6. 6
Introduction
Top View
Completed View
Bottom View

7. 7
Introduction
Wall-Following Algorithm
Comments
Wall-Following Algorithm
•Follows the Right Hand Wall Rule
•Simple
•Fast
•Unique Solution
•Works for Open Circuits
•No need for Memory Storage
•Parameters can be easily controlled

8. 8
Introduction
Open Circuit
Different Types of Circuits
Closed Circuit

9. Algorithm

10. 10
Algorithm
Pseudo Code
Pseudo Code Blocks
Initialization
Block
Turn Right/Left
Block
Medium Motor
Turn Right/Left
Block
2 If Blocks
Move Forward
Block

11. 11
Algorithm
Initialization Block
• Initializes x, y position and direction
• Used to generate trajectory of robot and maze map
Comments

12. 12
Algorithm
1st
If Block
• Reads from Infrared Sensor
• Checks if there is a wall on the right
− Reading of less than 15 indicates that wall is present
Comments

13. 13
Algorithm
2nd
If Block
• Decides on the direction to move
Comments

14. 14
Algorithm
Move Forward Block
• Moves robot forward by 1 step (pre calculated)
• Updates its direction
• Direction:
− 1: forward
− 2: right
− 3: backward
− 4: left
Comments

15. 15
Algorithm
Turn Left Block
• Turns robot to the left
• Increments direction by 1
Comments

16. 16
Algorithm
Turn Right Block
• Turns robot to the right
• Decrements direction by 1
Comments

17. 17
Algorithm
Medium Motor Turn Right Block
• Medium motor holds the infrared sensor
• Turns medium motor to the right
− Add 90 to reading to get rid of drift
• Uses proportional gain of 0.5 to reduce accumulated error
Comments

18. 18
Algorithm
Medium Motor Turn Left Block
• Turns medium motor to the left
− Subtract 90 from reading to get rid of drift
• Uses proportional gain of 0.5 to reduce accumulated error
Comments

19. 19
Algorithm
Check Right
No wall
(proximity>15)
Wall
(proximity <15)
Turn Right & Move
Forward
Logic
Check Front
Move ForwardNo wall
(proximity>15)
Wall
(proximity <15)
Turn Left and Repeat
from the start

20. Result

21. 21
Result
Video
The Robot in the Maze
Constructed Maze

22. 22
Result
Robot’s Escape Route on Matlab
• Red and straight lines show the borders of the
maze
− Achieved by combining direction information
• Blue and dashed lines show the route that our
robot traveled only once
• Blue and straight lines show the route that our
robot traveled back and forth
− Achieved by combining position and direction
information
Comments

23. Thank You!