1. Introduction

3pi wall follower’s path around an irregularly shaped object.

The 3pi robot is complete mobile platform designed to excel in line-following and maze-solving competitions. The 3pi has user accessible I/O lines that can be connected to different sensors to expand its behavior beyond line-following and maze-solving. This project shows just one possible configuration where two Sharp analog distance sensors are connected with minimal soldering. Many other sensors could be used to expand the 3pi: a radio-control receiver could make an RC 3pi gyro could enable precision spinning, a sonar range finder could improve the 3pi’s sensing range, and a digital distance sensor could offer speedy front obstacle detection!

Mounting two distance sensors as described in Section 3 and running the program detailed in Section 4 enables the 3pi to explore a room by following the wall and avoiding obstacles that it encounters. It tries to keep a safe distance from the wall or any other obstacles it sees on its left side and turns in place to the right if it detects an obstacle in directly in front of it. As an added safety precaution, every 15 seconds the robot tries to back up in case it has unknowingly gotten stuck while exploring. The figure above shows the path the 3pi wall follower might take around an irregularly shaped obstacle, and the video below shows the 3pi wall follower in action.