I made my first caterpillar in 1999 during an artist residency at Orchardton House in southwest Scotland. In some ways it’s the most far-fetched mechanism I’ve ever created. There is a motor at each link connected to a piece of threaded rod. The caterpillar itself is covered with sliding contacts that feed variable resistance to these motors. So it is the shape of the caterpillar that determines the speed of the motors, which in turn changes the shape of the caterpillar. In theory it could work, but in practice it meant trying to balance six continually changing feedback loops. I considered myself quite lucky when, with a lot of coercion, it walked two feet in 17 minutes during its opening show.