Research On Underactuated Anthropomorphic Hand Mechanism Based On Fingers’ Kinematic Synergy

As an important element of the rehabilitation medicine project, prosthetic hand is an important means to achieve the rehabilitation of the disabled or social regression. Therefore, how to design a prosthetic hand which is highly humanoid in form and function, and with highly adaptive capabilities for different objects,has been the focus of this research area. Base on the national 973 program whose topic is “design, manufacturing and performance evaluation of an intergrated smart prosthetic hand with operation perception”,an underactuated prosthestic hand with less drive number, high flexibility, low cost, reliable operation simple control, highly humanoid appearance and movement form is developed, which can meet the life and psychological requirement of amputees.The design focus of this paper is focused on how to design the underactuated prosthetic hand with less drive number, high flexibility, simple control, big output force and low cost under the guidance of sports spectrum, HIT-VI prosthetic hand prototype consists of five fingers, a cooperative mechanism, three drive system and a plam mounting plate. Each finger has three knuckles and three rotary joints, with two degrees of freedom. As the core component of a prosthetic hand, the cooperative mechanism includes a cooperative link mechanism and three linear guide rails. It is driven by two motors, with a cooperative motion between the fingers. Besides, there is a flexible rotatry joint between cooperative links, so the cooperative link mechanism has a strong synergistic adaptive gripping ability. Since the structure and layout form of the palm, three output points of collaborative links have position limits. Combined with the position limit, flexible rotary joints can make the cooperative mechanism complete extensive prosthetic hand pointing operation and adaptive grasping action.The movement pattern of fingers is continuous. The coordination proportinal relationship exists between finger joints before encountering an object. Thus, the design of underactuated prosthetic hand should fully replicate the actual movement of manpower and achieve the more anthropomorphic effect. The relationship between manpower knuckles must be taken into account while designing. Therefore, the finger of HIT-VI underactuated artificial hand is designed to have both coupling and underactuated characteristics. There exists proportional linkage between joints while finger moving in the free space. After a knuckle contacting with the object, the next level kunckle will continue rotating. The operation of adaptive grasp could be completed in this way.The second part of this paper gives the design specifications and transmission program of the underactuated artificial hand. The third part details the cooperative institutions, ideas and detailed design while designing HIT-VI prosthetic hand fingers. The fourth describes the design of the coupling –underactuated adaptive finger. In the last part of the paper, the personification and adaptability of the coupling-underactuated finger is verified experiments, which prove the dexterity and adaptive ability to grasp.