On Chain Driven, Adaptive, Underactuated Fingers for the Development of Affordable, Robust Humanlike Prosthetic Hands

Amputations and limb loss can have detrimental effects on personal well-being. Although prosthetic devices can offer significant benefits helping amputees regain some of the lost dexterity, they often lack the required affordability and durability. Current affordable prosthetic designs have trended towards underactuation, which contributes to stable grasping but is often characterized by low durability. In this paper, a new chain-driven, adaptive, underactuated finger design has been proposed for the development of affordable and highly durable prosthetic hands. The transmission mechanism used is composed of a steel roller chain and several routing sprockets. The finger phalanges are constructed of 3D printed PLA, and finger flexion is produced by pulling the internally routed roller chain. In total, six 3D printed PLA sprockets are used for chain routing, with a design emphasis on high force transmission. The performance of the proposed chaindriven finger was experimentally validated and compared with an analogous tendon-driven version. The metrics employed for this comparison were longevity, pinch grasp efficiency, force response, and maximum force capability. The chain-driven finger was shown to have a higher maximum transmissible force, better long term durability, and no issues related to elongation (such as tendon elongation). The cost to manufacture the chain-driven robotic finger is only 91 USD, making it an excellent solution for affordable prostheses.