Little Quadruped Emulates MIT's Cheetah on the Cheap

Six-legged robots can be dynamically stable on three limbs, while the other three move. If you want to have your device get around on four legs, things become a little more complicated. Robots like MIT’s Cheetah work quite well, but at a price in dollars (and research time) that's not affordable for the typical hobbyist. As a low-cost alternative, Jake Wachlin is developing a quadruped walker, which uses the same sort of gait as the Cheetah yet with only 150:1 brushed gearmotors.

It’s a tall order, and Wachlin doesn’t expect nearly the same kind of capabilities as MIT's, however there are a few tricks from the Cheetah that he’s incorporating to duplicate in the smaller model. First, this device is using Bezier curves to control leg movements, which is much smoother than attempting simple linear interpolation between two points. What's even more fascinating is that the Cheetah utilizes a virtual model to simulate elasticity in its motion. This creates a virtual spring and damper system between the foot and its desired placement, which Wachlin is trying to replicate as well.

It’s a really neat concept, and although it still seems to be a work in progress, the quadruped seen in then video below trots decently for something using only inexpensive gearmotors with integrated position sensing. The system is controlled via a closed-loop interface that we featured here, which also certainly helps these little motors perform far above their weight class!