Simulation of autonomous rhythm and gait generation in quadrupedal locomotion with hindlegs

Intending to further simplify motion planning and control of quadrupedal locomotion through emergence, we propose a legged locomotion controller inspired by the sensorimotor functions observed in the spinal cord of cats. In simulations using a hind-legged biped robot, we demonstrate the emergence of a rhythm and gait closely resembling the belt-driven locomotion observed in spinal cats. We also show the self-propulsive locomotion of this hind-legged biped, based on the hypothesis that the brainstem output directs the intensity of muscle contraction (locomotion power) to the spinal cord. Furthermore, we meticulously examine the dynamic interaction with the environment, considering the fixture's presence, and document the entire process in detail. We show that the mechanisms underlying the emergence of legged locomotion are the interactions between leg phase switching, self-excited oscillations of the body or trunk, and leg load spatiotemporal pattern. In regard to the last parameter, the temporal pattern of the leg load determines the rhythm, and the spatial pattern determines the gait.