Abstract
We discovered a specific rule for generating typical quadrupedal gaits (the order of the movement of four legs) through a simulated quadrupedal locomotion, in which unprogrammed gaits (diagonal/lateral sequence walks, left/right-lead canters, and left/right-lead transverse gallops) spontaneously emerged because of leg loading feedbacks to the CPGs hard-wired to produce a default trot. Additionally, all gaits transitioned according to speed, as seen in animals. We have therefore hypothesized that various gaits derive from a trot because of posture control through leg loading feedback. The body tilt on the two support legs of each diagonal pair during trotting was classified into three types (level, tilted up, or tilted down) according to speed. The load difference between the two legs led to the phase difference between their CPGs via the loading feedbacks, resulting in nine gaits (32: three tilts to the power of two diagonal pairs) including the aforementioned.
Highlights
We discovered a specific rule for generating typical quadrupedal gaits through a simulated quadrupedal locomotion, in which unprogrammed gaits spontaneously emerged because of leg loading feedbacks to the central pattern generator (CPG) hard-wired to produce a default trot
Following the theory of motion generation proposed in the studies of physiology and biomechanics, we contributed to this literature by building simple quadruped robots[24,25] and a simulation model[26] and observed the effects of the dynamics of the locomotion in their gaits to search for a rule behind the generation of each gait
If two different feedback signals are inputted into the two CPGs of each diagonal pair of legs in phase during trotting, a different gait should emerge because the two CPGs would be prevented from being in phase
Summary
We discovered a specific rule for generating typical quadrupedal gaits (the order of the movement of four legs) through a simulated quadrupedal locomotion, in which unprogrammed gaits (diagonal/lateral sequence walks, left/right-lead canters, and left/right-lead transverse gallops) spontaneously emerged because of leg loading feedbacks to the CPGs hard-wired to produce a default trot. Since it has been reported that the sensory feedbacks to CPGs play important www.nature.com/scientificreports roles in synchronizing the oscillations of the CPGs with those of body parts[2,27,28], we applied the feedback of the body tilt around the roll axis to the CPG models, based on the vestibulospinal reflexes[29] for postural control This extended the stance duration of each leg on the side towards which the body tilted in the lateral plane and shortened that of each leg on the opposite side. Since the cyclic duration of walking becomes longer at low speeds, the body regularly sways during the double support phase of the trot We inputted this body oscillation into each CPG through the vestibular feedback; as a result, each leg phase regularly deviated from trotting and the lateral sequence walk spontaneously emerged. When we applied the vestibular modulation to the body oscillation around the pitch axis during running on flat terrain, the two legs that the model tilted towards led to the stance phase according to its regular large body oscillation of backwards and forwards, and the model achieved a safe bounding[25]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
