Structure Design And Verification On An Underactuated Five-Finger Bionic Dexterous Hand Using Joint Constraints

The shortage of professional nursing staffs has become one of the serious problems in the field of medical rehabilitation.With the continuous development of robot technology,nursing robots have emerged at the historic moment.As the end effector of nursing robot,the bionic multi-finger dexterous hand has a direct impact on the working ability of nursing robot.Therefore,the development of low-cost,high-flexibility,light-weight dexterous hand has become a hot issue in the field of nursing robots today.In this study,an underactuated five-finger bionic dexterous hand using joint constraints has been designed,which combined of electromagnetic technology and metamorphism.It mainly includes the following aspects:In order to meet the requirements of the dexterity of bionic dexterous hand and controllability of finger gesture in performing grasping tasks.Referring to bionics and man-machine friendly theory as well as modular design ideas,an underactuated five-finger bionic dexterous hand design scheme that can achieve independent control of joint degrees of freedom is proposed.The joint coupling problem of underactuated dexterous hand is solved.The arrangement of the positions of the fingers and the mechanical structure of the fingers and palms are analyzed.The finger rotation joint and tendon rope transmission mechanism without disassembly and pre-tightening are designed.The problem of tendon slack of rope driven dexterous hand is solved.The three-dimensional model of the underactuated five-finger dexterous hand is established,which lays the foundation for the following analysis and optimization design of the dexterous hand.Based on the three-dimensional model of the underactuated five-finger dexterous hand,the mapping matrix of the global coordinate system of the dexterous hand and the base coordinate system of each finger is established through coordinate transformation.The fingertip coordinate system and the base coordinate system of each finger are established by D-H homogeneous transformation matrix and the Jacobian matrix of the finger is figured out.Research on the working space of the single finger and the whole hand of the dexterous hand is carried out using the Monte-Carlo method to obtain the evaluation index of the dexterity of the dexterous hand.The static and dynamic analysis of the finger is carried out.Based on the mathematical model of the finger joint constraint structure of the dexterous hand,the electromagnetic simulation of the rotating joint is carried out by using the software ANSYS electromagnetics.The influence rules of the parameters such as the gap between the armature and the electromagnet as well as the number of ampere turns of the electromagnet on the electromagnetic attraction are obtained,and the joint constraint structure is optimized.Through electromagnetic suction experiments,the accuracy of electromagnetic simulation and the reliability of the dexterous hand joint restraint ability are verified,which provides a testing basis for the reasonable selection of electromagnets.Simulation analysis of envelope grabbing and precise grabbing about regular and irregular objects are developed using Adams software.Single-finger submissive ability and control ability test on a prototype hand have been conducted to validate the dexterous hand’s self-protection and joint constraint ability.The test of envelope grasping and precise grasping of the prototype hand are carried out to verify the rationality of the design,the stability of grasping and the reliability of action.The underactuated five-finger dexterous hand using joint constraints has the characteristics of simple structure,low production cost,and stable movement.The research results provide a new choice for the realization of miniaturization,lightweight and flexible and stable grasping of nursing robot dexterous hand.