A study of function of foot´s medial longitudinal arch using biped humanoid robot

The humanoid robot, WABIAN-2R, has achieved human-like walking with knee-stretched, heel contact and toe off motions by using a foot mechanism with a passive toe joint. However, the foot structure is different from a human´s. In this paper, we describe a new foot mechanism capable of mimicking the human´s foot arch structure to figure out the function of the arch structure. Especially, the developed foot mimics the elastic properties of the arch of the human´s foot and the change of the arch height during walking. The foot mechanism consists of a passive joint in the internal toe, a passive joint in the external toe, and a joint in the foot arch. We conducted several walking experiments by using WABIAN-2R, and the function of the arch structure is clarified quantitatively. As a result, we confirmed that the arch elasticity could absorb a foot-landing force at the plantar contact phase and the change of the arch height contributed to a strong thrust at the push-off phase.