Movement Characteristics Of Human Hand Grasp And Its Applications For The Design Of Anthropomorphic Robotic Hand

After a long evolutionary process for millions of years,humans possess an incomparable dexterous hand among the animal kingdoms.Duplicating the human hand has become one of the most desirable objectives of robotics research in the last few decades.However,the anatomical structure of the human hand is extremely complex.It is a challenging problem that how to reproduce the human hand in a scientific way.This thesis carried out the systematic studies to solve the problem from making clear the movement characteristics for hand grasp,exploring the structural characteristics for the dexterous ability of the human hand,and inspiring the mechanical design of the anthropomorphic robotic hand.The main innovative researches are summarized as follows:The coordinated strategy of the human hand was inspected by analyzing the large amount of movement data during the various grasping tasks in the daily life.The movement analysis reveals that there exist the basic and inherent coordinated relationships in the human hand.A new method of clustering analysis was then applied to obtain almost all of the possible coordinated relationships.According to the obtained movement-coordinated relationships,the structural characteristics in the human hand that account for the hand coordination were found.Each movement-coordinated relationship has a clear anatomical evidence from the musculoskeletal structure.It establishes the functional link between the musculoskeletal structure and coordinated strategy of the human hand.The complex task of in-hand manipulation with the fingertips was chosen to establish the functional model of dexterous manipulation.A global manipulation index was proposed to construct the assessed way of the manipulative ability.By means of the assessed model,the manipulative abilities of the human finger and some mechanical fingers were measured and compared,so as to illuminate the functional advantage of the human finger.The results indicate that the three-joint finger structure in the human hand holds the much better manipulative dexterity than the two-joint finger structure in some mechanical hands when considering the constraints of joint range of motion.In addition,the mechanical coupling of proximal and distal inter-phalangeal joints by the biomechanical constraints in the human finger does not reduce the functionality too much.Forming the three-joint finger structure with the mechanical coupling of proximal and distal inter-phalangeal joints is perhaps a favorable strategy adopted in the human hand,with the three-joint structural form ensuring the functionality while the coupling mechanism decreasing the control complexity.The compare researches between the human hand and the other anthropoid hands were performed,by applying the collected morphological data of phalangeal lengths and the established functional model.The assessed result reveals that the morphological structure of the human hand is most suit for manipulation among all the anthropoids.The hand structure itself offers the excellent manipulative potential for the humans.The evolutionary analyses were further used to make clear the factors that how the human hand evolved into the best manipulative ability.The results indicate that the morphological changes of the human hand coevolved with the brain to facilitate the manipulative ability,with the morphological changes of lengthening both the metacarpal and phalanges of the thumb while shortening both the metacarpal and phalanges of the finger after descending from the common ancestor with the chimpanzees.Human hand thus formed the present specialized morphological structure that suits for manipulation.Based on the previous cognitive studies of the human hand,a mechanical design method of the robotic hand was proposed that it only needs to imitate the structural characteristics of the human hand while not necessary to mimic the biological structure completely.Applying the design method and considering some extra engineering requirements in the prosthetic application,which requests to reduce the number of actuators,a humanoid robotic hand with four actuators and sixteen joints was developed.Compared to the robotic hand developed before without the cognitive studies of the human hand,the robotic hand developed in this thesis has a compact structure and is able to reproduce most grasping tasks in daily life.The grasping experiments verified the validity of the proposed design method.