Abstract
The paper reports a structural approach to reduce impact force in landing the swinging leg of biped robot. The robot introduces redundant legs in the sagital plane, which have redundancy in terms of DOF that is, extra joints besides hip, knee and ankle in each leg. The leg independently changes the posture, regardless of the tip position, while the center of mass (COM) of the leg moves to an arbitrary position even if the tip is fixed. Since the position of COM moves in landing the swinging leg toward the ground, therefore the impact force is reduced. The validity of the proposed approach is confirmed in physical experiments.