Caterpillar and Woodpile

A caterpillar with nine electric motors climbs a woodpile!

Created in 2019, exactly 20 years after my first caterpillar, this one can tackle variably curved terrain. Inside the caterpillar is a micro-controller holding a file with a quarter million angles. As the motors sequentially follow these angles, the caterpillar traverses the woodpile.

The woodpile is not as random as it looks, but follows a predetermined polynomial spline within certain bounds of curvature. It is made of scrap wood and took about week to make. The caterpillar took several months, although a lot of that time was spent learning about servo motors, micro-controllers, Terminal and Python, and learning how to use an oscilloscope to trouble shoot the square wave signal that carries the angular information.

But the crux of the work was a gloriously fun math problem. Solving caterpillar motion over arbitrary curved surfaces is the toughest, and most rewarding, math that I’ve gotten into yet. It took me several months as well.

The video is a single take, shot between 1:10pm and 1:20pm in my shop, when the sun aligns with a skylight to create a pool of light. The video is by Chris Potter.

Special thanks to Dan Torop for his willingness to hear me go on and on about caterpillar movement, and for offering encouragement and insight into everything from aesthetics to coding. Thanks to Mike Prados and Greg Stevens for coming over to help me troubleshoot electrical noise and teaching me how to use an oscilloscope. And many thanks to my generous neighbors at Zephyr Tents who let me rummage through their bin of scrap wood to make my woodpile.