Carro

Sample Project: 3pi Wall Follower

© 2001–2010 Pololu Corporation

Sample Project: 3pi Wall Follower

1. Introduction . . . . . . . 2. Materials and Tools . . . 3. Construction . . . . . . 4. Software . . . . . . . . 5. Suggested Improvements 6. Conclusion . . . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . ..

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

2 3 4 6 9 10

Page 1 of 10

Sample Project: 3pi Wall Follower

© 2001–2010 Pololu Corporation

1. Introduction

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

The 3pi robot[http://www.pololu.com/catalog/product/975] 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 othersensors could be used to expand the 3pi: a radio-control receiver could make an RC 3pi [http://www.pololu.com/docs/0J37.a] gyro [http://www.pololu.com/catalog/product/765] could enable precision spinning, a sonar range finder [http://www.pololu.com/catalog/product/723] could improve the 3pi’s sensing range, and a digital distance sensor [http://www.pololu.com/catalog/product/1134] could offer speedyfront 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 frontof 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.

1. Introduction

Page 2 of 10

Sample Project: 3pi Wall Follower

© 2001–2010 PololuCorporation

2. Materials and Tools
Beyond the Polou 3pi robot + USB programmer + cable combo [http://www.pololu.com/catalog/product/1306], you will need a few other materials for this project. You only need the materials listed under the “required” section to make the wall follower work, but the optional headers make it easier to reconfigure your 3pi with other sensors later by allowing you tounplug your distance sensors.

Required
• 2 Sharp GP2Y0A21YK0F distance sensors [http://www.pololu.com/catalog/product/136] • 1 140-piece wire kit [http://www.pololu.com/catalog/product/312] • Double-sided foam tape • a Soldering iron [http://www.pololu.com/catalog/product/156] and solder

Optional
• 1 0.100" (2.54 mm) female header: 2×7-pin, straight[http://www.pololu.com/catalog/product/1027] • 1 0.100" (2.54 mm) female header: 1×2-pin, straight [http://www.pololu.com/catalog/product/1012] • 1 0.100" (2.54 mm) breakaway male header: 2×40-pin, straight [http://www.pololu.com/catalog/product/966] • 1 0.100" (2.54 mm) breakaway male header: 1×40-pin, straight [http://www.pololu.com/catalog/product/965]

2. Materials and Tools

Page 3 of 10

Sample Project: 3pi Wall Follower...