Finger abduction and adduction prosthetic hand for power and precision grasping

Abstract

The human hand has 27 bones and 19 joints, and they are classified into three groups like carpals, metacarpals, and phalanges. There are eight carpals, five metacarpals, and fourteen phalanges. There is a tendon system to produces finger movements and grasping patterns in activities of daily living. With those systems, the human hand is a highly complex part of the human body that is difficult to replicate with an artificial device. Hand amputation can happen due to various reasons, like war casualties, accidents, and neuromas. Losing a human hand through amputation is end up with mentally, physically, and socially devastating, significantly affecting the quality of life of the individual. Over the years, prosthetic hands have been developed to support hand amputees to come back to their normal lives. Different types of methods and mechanisms have been developed to replicate the human hand. However, maintaining the aesthetic view and anthropometry of the hand is challenging due to the size of the human hand. During the human hand replication, the finger movements and grasping patterns are very important. There are mainly two types of finger movements, flexion and extension (FL/EX) and abduction and adduction (AB/AD). Other than that, Retroposition and Opposition, and Bending and Flattening are some other finger movements. Using the above finger movements, the human hand is capable of different types of grasping patterns. Power, Precision, Lateral, and Extension grasps are the main grasping ranges. Power and Precision grasps cover 65% of the grasping patterns in Activities of Daily Living. Most of the currently available prostheses are not capable of producing individual finger AB/AD motion. Due to the lack of motion patterns, the functionality of the hand prostheses is limited. The aim was to propose an abduction and adduction mechanism to fill the gap in the prosthetic hand industry. The proposed prosthetic hand is capable of individual finger AB/AD motions and covers the special grasping patterns like Tripod, Quadpod, and Squeeze, along with other common power and precision grasping patterns. The objectives of the project are to design an under-actuated finger abduction and adduction mechanism for a prosthesis. Then, develop a suitable control system to control the prosthesis and test and validate the prosthesis using experiments