CPG Walker
central pattern generator locomotion
no learning. no evolution. the architecture IS the walk.
A Central Pattern Generator is a neural circuit that produces rhythmic motor output without requiring rhythmic input. Your spinal cord has them — they produce the basic walking pattern even without the brain. This is how biology walks: oscillators, not keyframes.
Matsuoka neurons form half-center oscillators: two neurons mutually inhibit each other, creating rhythmic alternation. Left hip flexor inhibits right hip flexor — this is where the anti-phase gait pattern comes from. Knees are driven by ipsilateral hip neurons with phase lag.
Proprioceptive reflexes feed back into the CPG: ground contact extends stance, swing foot lifts for clearance, vestibular sensing corrects balance. The CPG sets the rhythm; reflexes modulate it. Push the body — watch it recover. Change terrain — watch it adapt.
Five gaits from the same architecture: walk, run, creep, march, limp. Only the CPG parameters change — tonic drive (speed), time constants (rhythm), coupling weights (coordination). Same body, same reflexes, different personality. That is what gait IS — parameter variation over structure.
Genesis evolves walking. Cortex learns walking. The CPG Walker simply walks. It does not discover locomotion — it embodies it. This is the god end of the Kleist spectrum: total awareness, total grace. The body knows itself.