A Robot Hand for Versatile Grasping With Tendon-Driven Telescopic Fingers

Service robots need robot hands that are versatile to grasp various objects while being lightweight to ensure robot mobility, minimize power consumption, and prioritize safety. In this paper, we propose a robot hand capable of adjusting the length of its fingers using a tendon-driven telescopic mechanism to accommodate objects of different sizes. The telescopic mechanism utilizes embedded wires to extend actively and an external silicone rubber glove to contract passively. The initial length of the fingers is set at 81.5 mm, with a maximum length of 141.5 mm, resulting in an elongation rate of 73.6%. The bending mechanism of the finger, which is independent from the telescopic mechanism, is realized with wires for active flexion and torsion springs for passive extension. Underactuated bending of the three finger joints is incorporated to conform to object shapes. The implemented robot hand with 3 fingers weighed only 230 g including 2 motors for telescopic extension and finger flexion. To evaluate the effectiveness of the telescopic robot hand, a two-way pull-out experiment was conducted using cylindrical objects of seven different sizes. The results demonstrated that adjusting finger length according to the objects improves grasping stability. The grasping experiments with daily objects indicated that the robot hand with telescopic fingers can stably grasp most of the objects used in daily life.