Months ago, for a larger project that is currently languishing in my “when I have time” pile, I built a very simple Kiwi-drive robot. Since it likely won’t be “finished” for a long while (and has been sitting in my trunk for weeks), I figured I ought to at least document it.
Very briefly, kiwi drive is a “holonomic” method of moving a robot, which basically means it can move in any direction without having to turn first. It accomplishes this using three omniwheels mounted at the points of an equilateral triangle. With some vector math, you can find rotational speeds for each wheen such that the robot will move in whatever direction you like. I won’t go into the theory too much here, but here are some diagrams and here’s some math (via).
In the video I’m controlling the robot with a Wii Nunchuck. That’s because my 14-year-old cousin was hanging out at the shop when I built it; he saw the controller in my parts bucket and said “you HAVE to connect the nunchuck to the robot!” So I did. I used Tod E. Kurt’s breakout board and example code.
The robot is dead simple. It essentially consists of three different parts — a microcontroller, omniwheels, and servos — and it took about five minutes to put together. Keep reading to learn how it works and download the code. » Read the rest of this entry «