Locomotion

Swing Phase

The swing phase is the portion of a legged gait cycle during which a foot is off the ground, traveling from liftoff to its next touchdown location. Swing-leg control shapes the foot trajectory for ground clearance, places the foot to regulate balance — following principles like Raibert's foot placement heuristic — and manages touchdown timing and impact. Insufficient swing clearance causes tripping, a dominant failure mode on rough terrain.

Why it matters for physical AI

Foot placement during swing is the primary control authority a legged robot has over its own stability, which is why learned locomotion policies devote much of their capacity to it.