Planar One-Leg Hopper (1980-1982)


The Planar One-Leg Hopper was built to explore active balance and dynamic stability in legged locomotion. The machine has one leg that changes length and pivots with respect to the body. The body carries sensors, interface electronics, and the hip actuators. The machine was powered by pneumatics.

Experiments with the Planar One-Leg Hopper showed that balance could be achieved with a simple control system. The control system has three separate parts: one controlling forward running speed, one controlling body attitude, and one controlling hopping height. These controllers worked independently, treating any coupling as disturbances. The control system for the Planar One-Leg Hopper did not explicitely program a stepping motion, but allowed the stepping motion to emerge under the constraints of balance and controlled travel. The Planar One-Leg Hopper hopped in place, travelled at specified rates, and maintained balance when disturbed. The simple techniques used for planar one-leg hopper were later generalized for 3D one-leg hopping, bipedal running, and quadruped trotting, pacing, and bounding.

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