How Robots Walk: Central Pattern Generators

Walking is rhythmic, fast, unstable, and made discontinuous by every footfall, which is why trajectory planning fits it badly. Biology solves it with spinal circuits that generate rhythm without the brain. This path builds that architecture: coupled phase oscillators whose limit cycles absorb disturbances, gaits as nothing more than sets of phase relationships, the salamander robot where one scalar drive switches swimming to walking, and how sensory entrainment and reinforcement learning compose with it.