Emergence of hysteresis in gait transition of a hexapod robot driven by nonlinear oscillators with phase resetting

Our previous work has revealed that a quadruped robot, whose legs are controlled by nonlinear oscillators with phase resetting, shows a walk-trot transition induced by changing the locomotion speed through dynamic interactions among the robot's mechanical system, the oscillator control system, and the environment. Furthermore, the gait-pattern transition exhibited a hysteresis similar to that observed in the locomotion of humans and animals. In the present study, we apply this dynamic analysis to a hexapod robot model to investigate general properties of the hysteresis embedded in the locomotion dynamics of legged robotic systems. Our simulation results show that the hexapod robot produces the metachronal and tripod gaits depending on the locomotion speed and the gait transition is induced by changing the locomotion speed. In addition, the gait transition shows a hysteresis similar to the quadruped robot. We examined the mechanisms of the hysteresis from the perspective of dynamics.