Stable pinching with fingertips in humanoid robot hand

It is difficult to generate the action of stably pinching paper or needle, etc. with the finger tips, which is one of the important functions to be realized by humanoid robot hands. In this paper, therefore, the authors firstly propose a small-sized and light-weight robotic hand designed according to the concept of extracting required minimum motor functions and implementing them to the robot, and secondly propose a new robot hand capable of properly realizing a pinching motion with finger tips, by adding the minimum required degree of supplementary freedom which can be realized only with a machine. In the new robot hand, the authors mainly focus on additions of the degrees of freedom of independent motion to the terminal fingers and the degree of freedom of twisting motion to the thumb. Experiments were carried out to investigate force control characteristics of the finger tip joint. The results showed that providing the finger tip with rich force control performance even with weak force is effective for securing delicate control characteristics in a humanoid robot hand.