  We propose a modular architecture for neuromorphic closed-loop control based
on bistable relaxation oscillator modules consisting of three spiking neurons
each. Like its biological prototypes, this basic component is robust to
parameter variation but can be modulated by external inputs. By combining these
modules, we can construct a neural state machine capable of generating the
cyclic or repetitive behaviors necessary for legged locomotion. A concrete case
study for the approach is provided by a modular robot constructed from flexible
plastic volumetric pixels, in which we produce a forward crawling gait
entrained to the natural frequency of the robot by a minimal system of twelve
neurons organized into four modules.
