Axiomatic Design Of A Tendon-driven Under-actuated Prosthetic Hand Based On Compliant Mechanism

The current existing prosthetic hands are deficient in these aspects:heavyweight and large volume,few grasping gestures,dissimilarity with human hands in their appearance and high price,making prosthetic hands’ utilization rate low.In order to improve the current situation of prosthetic hands,this thesis is devoted to the development of a multi-degree-of-freedom under-actuated hand prosthesis with high humanization,small volume and light weight.The thesis mainly focuses on the following aspects:(1)Based on axiomatic design theory,the design of prosthetic hand was analyzed and optimized,and two design schemes were proposed accordingly.Tendon driven mechanism,force distribution mechanism with pulleys and thumb’s abduction/adduction mechanism were proposed in the first generation of prosthetic hands.The second generation of prosthetic hands were designed to improve the few DOFs and poor finger coordination of the first generation of prosthetic hands.In the second generation of prosthetic hands,differential mechanism and optimized transmission mechanism were proposed,which can drive a variety of grasping gestures,thus ensuring a bigger grasping range.(2)The proposed compliant finger based on flexure hinges took a flexible resin material to be manufactured by 3D printing,and the finger proved to be extremely light with great bending and resilience performance.(3)Programmable controllers(Arduino)were developed in the second generation of prosthetic hands to collect the feedback signals from fingers and motor’s encoders,in the meantime realizing a real-time closed-loop control to adjust the fingers’ grasping position and force.(4)Bluetooth wireless communication module and gForce EMG bracelet were combined to accomplish hand control by EMG signals.Control system’s volume and cable numbers can be reduced with Bluetooth wireless communication module.This thesis proposed a new prosthetic hand,which can be controlled by EMG signals.The total weight of the hand is 186g,which is reduced by at least 62.8%of the exsiting prosthetic hand(mostly more than 500g),and the cost is less than 1000 RMB,which provides a high potential for commercialization.