I made this because I could. I had the plastic project box and a set of Pololu motors and wheels from a 3pi robot. It’s a pretty straightforward approach. It has an Arduino with an NKC Arduino Motor Shield. For a sensor, I use a Sharp Infrared long range unit. It can look ahead up to six feet and down to about 10 inches. Farther or closer, it cannot see.
Anyway, I used a Tamiya ball caster as the third wheel. Add in a switch and a 9 volt battery and that’s pretty much the robot. The Arduino reads the analog voltage from the sensor and mathematically converts that to range in inches. It’s programming is simple see and avoid; the robot is capable of pivoting on point by running the motors in opposite directions. It can also make gentler turns by running the motors at different speeds. The robot will correct itself to either the left or right, depending on what it detects as it begins its turns on first sighting an object.
That’s pretty much it. The robot is pretty fast. The motors are six volts and so I have dialed down the motor shield output with PWM. The motors aren’t heating up at all, so I guess it’s working ok. On the loose it does well with everything except low lying obstacles like clothing, but it doesn’t get trapped in corners.