Research On Underactuated Structure Of Implantable Prosthetic Hand

Hands are essential organs of human. Losing of hand caused by various reasons will do harm to people both in physical and psychological seriously. However, as two treatments of losing hand, limb replantation and installation of artificial limbs developed in their respective fields separately as if two parallel lines, but both failed to meet the requirements of patients in function and appearance. To be able to clone the missing structure and function of the hand has always been the dream of human. The idea of implantable prosthetic hand make this dream possible to be achieved. This idea aims to provide a kind of implantable artificial hand that is multi-function, zero error rate and no complications, and make it a part of human body through surgery.This paper designed a kind of rope-controlled structure of prosthetic hand based on the idea of implantable prosthetic hand and the principle of under-actuated. This kind of hand can be driven by the ropes which are connected with the tendons of human arm. And it's able to achieve the basic action of human hand, such as grip and pinch. The following jobs have been done in the paper: study of the novel prosthetic hand mechanism, imitated from human hand designed a novel prosthetic hand, and by kinematic simulation, the fingers'motion and the grasping abilities are tested.1. Hand losing treatment research and development statusBecause the rejection of allograft hand replantation can not be treated by medical treatment, patients need to take immunosuppressive drugs for life and some other reasons, the installation of prosthetic hands is the main treatment of hand losing. Prosthetic hand through the six stages for thousands of years'development, has formed series types of products, such as decorative type of prosthetic hand, the body powered type of prosthetic hand and EMG signal controlled prosthetic hand, etc. And make continuous progresses in scientific research. However, the prosthetic hands in the current development state are still not able to meet the requirements of patients in function and appearance.Dr. Zhang Weizhong proposed the idea of implantable prosthetic hand. This idea is to develop a kind of mechanical structure of artificial hand to instead losing hand. This is based on the study of titanium alloy material, it is able to healing together with human bones and skin. If this idea comes true, it will adopted in clinical treatment as a new measure to treat losing hand, and make the development of prosthetic hand into a new era.2. Biomechanical analysis of human handIn order to design a kind of prosthetic hand that is mimic the structure and function of human hand and able to meet the need of implantation, first study on the basic structure and function of human hand, and research on the biomechanical of bones and tendons in hand. Prosthetic hand will be designed to imitate the main supporting structure of the hand skeleton, control rope imitate tendon and control ropes'moment arm with the similar size to tendon.3. CATIA-based three-dimensional modeling of the prosthetic hand and electronic simulation of prototypeMake use of CATIA's parametric model of human hand to grip and pinch objects, and determine the trajectory function from the fingertip motion trajectory, the function is of cubic polynomial. The cubic polynomial function provide the necessary basis for the design of prosthetic hand. According to the joint form of human hand, make sure the degree of freedom to design the prosthetic hand. According to the size of human hand, determine the size of prosthetic hand structure. Utilize CATIA software to build three-dimensional of prosthetic hand, set constraints of simulation and conduct simulation of electronic prototype. Optimized design the structure of prosthetic hand from the results of simulation. Make sure that the prosthetic hand is able to grip and pinch objects of different shape and size.4. Research on under-actuated control of prosthetic hand and test of motor functionOne finger of the prosthetic hand has three rotational degrees of freedom, but there is just one driving force to control it. Study on the principle of under-actuated control according to this character. From the test of two kinds of fingers controlled by single group of two ropes, they do not have sufficient stability of movement. Study on two kinds of linkages and make them in use into the finger structure. This kind of under-actuated prosthetic hand finger has the similar size and shape to human hand, the rotation angle of joints and the cable pulling distance show a linear relationship. And from the test of this kind of finger, its movement trajectory is similar to the trajectory of human hand. It can be used in implantable prosthetic hand.5. ConclusionThis chapter is mainly about the conclusion obtained in this paper. Give some advice and prospects for future research.