The Study on the Energy Efficiency of the Bipedal-Walking Pattern of a Humanoid Robot Using Four-Bar-Linkage Toe Joints

The purpose of this study is to increase the energy efficiency of a biped-walking humanoid robot. A traditional biped-walking robot walks with its knees bent, which places an unnecessarily large load on the knees. Therefore, in this study, a biped-walking robot with toe joints is developed. This allows it to walk naturally by moving its center of gravity forward, without bending its knees. In addition, as the load acting on the knee joint is reduced, a four-bar linkage mechanism is applied to avoid an excessive load on the toe joint. The toe structure to which the four-bar linkage mechanism is applied distributes the load transmitted to each axis of the toe joint. A 52.2-cm biped-walking robot was developed with the above toes applied. As it walked, the zero-moment point (ZMP) was measured, through forward kinematics and inverse kinematics, and experiments were conducted by applying a walking pattern unlike that of a robot without toes. The maximum step length, maximum speed, ZMP graph, and maximum current were measured. Experiment compared these metrics with those of a flat-footed robot, to demonstrate the efficiency of the robot to which toes were applied. The maxwimum speed and maximum step length were measured to be faster and larger, respectively, than those of a robot without toes, and a smooth ZMP-change graph was confirmed. In addition, the current measurement showed a lower electric charge; thus, proving the energy efficiency of applying the proposed mechanism.