Torque sensing of finger joint using strain-deformation expansion mechanism

^For dexterously performing object grasping and manipulation with multifingered hand of robot, sensing the finger joint torque is required. In general, the size of finger joint is quite small so that it is hard to realize the torque sensing. This paper proposes a novel mechanism, called the strain-deformation expansion mechanism, to sense the joint torque, which is small enough and fitted in the finger joint. By the torque sensing mechanism, the small joint strain-deformation used for torque sensing can be expanded without reducing the joint stiffness. In this paper, the torque sensing principle is addressed by analyzing the deformation of the sensing mechanism and the torques acting on the joint shaft theoretically. Then, the sensitivity of the sensing mechanism and its expansion rate of sensitivity are defined, and a design method for realizing the sensing mechanism with high sensitivity is discussed. Finally, some experiments with robot finger are performed to show the basic characteristics and the effectiveness of the proposed torque sensing mechanism.