Stable dynamic walking of the quadruped "Kotetsu" using phase modulations based on leg loading/unloading against lateral perturbations

We intend to show the basis of a general legged locomotion controller with the ability to integrate both posture and rhythmic motion controls. We respectively used leg loading and unloading for the phase transitions from swingto-stance and stance-to-swing, and showed the following in our previous 3D model simulation study: (a) as a result of the phase modulations based on leg loading/unloading, rhythmic motion of each leg was achieved and leg coordination (resulting in a gait) emerged, even without explicit coordination among the leg controllers, allowing to realize dynamic walking in the lowto medium-speed range (b) but an additional ascending coordination mechanism between ipsilateral leg controllers was necessary to improve the stability. In this paper, we report on experimental results using “Kotetsu” under a lateral perturbation while walking and compare them with the results of our previous simulations. Detailed robot specifications and movies of the experiments can be seen at: http://robotics.mech.kit.ac.jp/kotetsu/.