Influence of rotation of humanoid hip joint axes on joint power during locomotion

Most of the fully actuated legs of existing humanoids have a straight kinematics, i.e. roll, pitch and yaw joint rotary axes are aligned, respectively, along longitudinal, lateral and vertical axes of the robot’s body. This work explores different orientations of the hip joint axes where the yaw joint and the pitch joint axes are rotated about the longitudinal axis, keeping the serial order – yaw, roll and pitch – from the pelvis. Two walking movements are simulated dynamically: forward walk and turn-in-place. The measurements of joint mechanical power (JMP) consumption are used to compare the different kinematics configurations. The results obtained from simulation show that the inward and outward rotations of hip yaw and pitch joint axes about the longitudinal axis bring a significant reduction of pitch JMP, and lead to a better JMP distribution among the hip joint actuators compared with the classical straight configuration. In addition, the outward configuration presents a significant reduction of JMP...