To Design a Small Pneumatic Actuator Driven Parallel Link Mechanism for Shoulder Prostheses for Daily Living Use

Only in Japan, there are about 82,000 upper limb amputees (Ministry of Health, Labour and Welfare, 2005). Using upper limb prostheses could restore the function for them, thus improve significantly the quality of their activities of daily living [ADL]. Compared with below-elbow prostheses, shoulder prostheses are left behind in their development, due to high degrees of freedom [DOF] required, which demands a large number of actuators, thus denotes a large size and a heavy weight, and complicated control mechanism. Recently, there is a certain body of research on developing robotic devices that could be used as prostheses for shoulder amputees (Jacobson et al., 1982; Motion Control, Inc., 20062011; The Johns Hopkins University Applied Physics Laboratory [APL], 2011; Troncossi et al., 2005, 2009a, 2009b). These research efforts have led to artificial prostheses with high functionality and performance. For example, the prosthetic arm of Defense Advanced Research Projects Agency and APL, has 25 DOFs, individual finger movements, dexterity that approaches that of the human limb, natural control, sensory feedback, and a number of small wireless devices that can be surgically implanted (or injected) to allow access to intramuscular signals(APL, 2011). The Utah Arm 3, a modification of the previous Utah Arm that has been the premier myoelectric arm for above elbow amputees, has two microcontrollers that are programmed for the hand and elbow, accordingly, allowing separate inputs and hence simultaneous control of both, and that is, the wearer can operate the hand and elbow concurrently for natural function (Jacobson et al., 1982; Motion Control, Inc., 2006-2011). The hybrid electric prosthesis for single arm amputee of Tokyo Denki University possesses a ball joint of 3 DOFs in humeral articulation. Patient operates the prosthesis to optional point by pressing a switch with the other healthy limb to free the joint, and releases to fix and hold the prosthetic arm stably (Nasu et al., 2001). Moreover, the electromechanical shoulder articulation with 2 DOFs for upper-limb prosthesis that has two actuated joints embedded harmonic drives, an inverted slider crank mechanism, and ball screw, has been developed (Troncossi et al., 2005, 2009a, 2009b). These prostheses have the following characteristics: they are more or less anthropomorphic, basically supported by metal frames or parts, driven by electric motors, therefore, many of them seem to be not suitable for the daily living use: they are not light weight, not convenient, with a bad portability, and lack of backdrivability which could contribute to the safety use in daily living.