The underactuation and motion-coupling in robotic fingers and two new 1-DOF motion-coupling anthropomorphic fingers

Present multifingered hands share a common drawback: the complexity of both the hardware and the software. The complexity is derived from tens of DOF and their actuators placed in small space, and results in the high weight and the non-reliability of the whole system. So many multifingered hands, especially the prosthetics and the hand developed for project application, adopt under-actuation (in the finger or transmission system) or motion-coupling (in the finger) to reduce the number of actuators but not reduce the number of the DOF (under-actuation) or the motion (motion-coupling), and accordingly debase the complexity of the multifingered hand. This paper firstly reviews the under-actuation and motion-coupling used in existing anthropomorphic finger. And then based on the analysis of the existing motion-coupling anthropomorphic finger, we propose two new 1-DOF motion-coupling anthropomorphic fingers based on linkage. The two new proposed fingers are more compact than the existing 1-DOF fingers based on linkage. The feasibility of the two proposed fingers is validated in the end, and a 3D-CAD model of the anthropomorphic hand SIA-I with new-proposed fingers is given.