Kinematics Analysis of a Humanoid Leg With Redundancy Freedom

Abstract

Most of exist humanoid legs have 6 degrees of freedom (DOF). This paper proposes a new leg mechanism with 7 DOFs, and three DOFs in the hip, one DOF in the knee and three DOFs in the ankle. And in the hip joints, a mechanism called double spherical joint is adopted, which has six DOFs and those six axes intersect in one point. This mechanism is for humanoid hip joints with a waist joint function without increasing an actuator. And there are three degrees of freedom (DOF) in the ankle; therefore it is possible for the robot to perform multiple postures even if the positions of the hip and trunk are fixed